boeing ssfl comprehensive dqo report march2013 · 1-1 section 1 introduction this comprehensive...

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Contents Section Page

Acronyms and Abbreviations ............................................................................................................................... v

Introduction ......................................................................................................................................... 1‐1

Relevant SSFL Background Information ................................................................................................ 2‐1 2.1 SSFL Setting and Ownership Information ........................................................................................ 2‐1 2.2 SSFL Regulatory History and Investigation Program Summary ....................................................... 2‐1

2.2.1 RCRA Corrective Action ...................................................................................................... 2‐1 2.2.2 Surficial Media Operable Unit ............................................................................................ 2‐2 2.2.3 Chatsworth Formation Operable Unit ................................................................................ 2‐2 2.2.4 Comprehensive and Complete RFI ..................................................................................... 2‐3 2.2.5 Senate Bill 990 .................................................................................................................... 2‐3 2.2.6 DTSC Administrative Orders on Consent ............................................................................ 2‐3 2.2.7 Radiological Constituents ................................................................................................... 2‐4 2.2.8 Non‐AOC Investigation ....................................................................................................... 2‐4

Summary of Regulatory Comments and Requirements ........................................................................ 3‐1

Rationale and Scope of Comprehensive Data Quality Objectives .......................................................... 4‐1

Content of the Comprehensive Data Quality Objectives ....................................................................... 5‐1 5.1 Site Conceptual Models ................................................................................................................... 5‐2

5.1.1 CUA Confirmation and CNFA Area Documentation ........................................................... 5‐2 5.1.2 Surface Water Bodies Data Quality Objectives and Sampling Strategy ............................. 5‐3

5.1.2.1 Extent of Surface Water Impacts ....................................................................... 5‐3 5.1.2.2 Surface Water Mass Flux of Contaminants to Groundwater ............................. 5‐3

5.1.3 Soil and Sediment Data Quality Objectives and Sampling Strategy (Applicable to Boeing Only) ................................................................................................................................... 5‐4

5.1.4 Vadose Zone Data Quality Objectives and Sampling Strategy ........................................... 5‐4 5.1.4.1 Soil Vapor/Indoor Air Quality ............................................................................. 5‐4 5.1.4.2 Vadose Zone Mass Flux of Contaminants to Burrowing Ecological Receptors .. 5‐5 5.1.4.3 Vadose Zone Mass Flux of Contaminants to Groundwater ............................... 5‐5

5.1.5 Groundwater and Seeps DQOs and Sampling Strategy ...................................................... 5‐6

Summary and Conclusions ................................................................................................................... 6‐1

Glossary of Terms ................................................................................................................................ 7‐1

References ........................................................................................................................................... 8‐1

Tables

1 Assessment Methods and Activities to Identify a Chemical Release or Potential Release 2 Potential CUA Field Sampling Methodologies for CUA or Conditional NFA Determination for the SMOU 3 Surface Water Bodies Data Quality Objectives 4 Surface Water Bodies Characterization Sampling Strategy 5 Soil and Sediment Data Quality Objectives 6 Soil and Sediment Characterization Sampling Strategy 7 Vadose Zone Data Quality Objectives 8 Vadose Zone Characterization Sampling Strategy

CONTENTS, CONTINUED

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9 Groundwater and Seeps Data Quality Objectives 10 Groundwater and Seeps Characterization Sampling Strategy

Figures

1 SSFL Administrative Boundaries 2 CUA Confirmation and CNFA Area Weight of Evidence Assessment for the SMOU 3 Data Quality Objectives Process 4 Iteration of the DQO Process through the Project Life Cycle 5 Comprehensive Data Quality Objectives Flow Chart 6 CUA and CUA Cluster Scale Site Conceptual Model 7 Deep Soil and Groundwater Plume Scale Site Conceptual Model 8 SSFL Sitewide Facility Scale Site Conceptual Model 9 SSFL Historical Document Review Process 10 Analytical Approach/Decision Rules for Vadose Zone Mass Flux of Contaminants to Groundwater

Evaluation

Appendices

A Recommended Approach for Assessing the Vapor Intrusion Pathway B Recommended Approach for Air Dispersion Modeling C Integration of the SMOU Risk Assessment Methodology with the DQO Process D Recommended Approach for Evaluating Vadose Zone Mass Flux of Contaminants to Groundwater

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Acronyms and Abbreviations AOC Administrative Order on Consent

AST above ground storage tank

bgs below ground surface

Boeing The Boeing Company

BTV background threshold value

building demolition SOP The Boeing Company – Santa Susana Field Laboratory, Standard Operating Procedures: Building Demolition Debris Characterization and Management

building feature SOP Standard Operating Procedures: Building Feature Evaluation and Sampling, Revision 1, Santa Susana Field Laboratory, California

CDM CDM Federal Programs Corporation

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act of 1980

CFOU Chatsworth Formation Operable Unit

CMS corrective measures study

CNFA conditional no further action

COCA Consent Order for Corrective Action

CUA chemical use area

DNAPL dense nonaqueous‐phase liquid

DOE United States Department of Energy

DQO data quality objective

DTSC California Environmental Protection Agency, Department of Toxic Substances Control

FSP field sampling plan

GCL groundwater characterization level

GIS geographic information system

MCL maximum contaminant limit

MRL method reporting limit

MWH MWH Americas, Inc.

NASA National Aeronautics and Space Administration

NBZ Northern Buffer Zone

NPDES National Pollutant Discharge Elimination System

NDMA n‐nitrosodimethylamine

OU operable unit

PCB polychlorinated biphenyl

PID photoionization detector

RCRA Resource Conservation and Recovery Act

ACRONYMS AND ABBREVIATIONS

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RFA RCRA facility assessment

RFI RCRA facility investigation

SAP sampling and analysis plan

SB990 Senate Bill 990

SCM site conceptual model

SMOU Surficial Media Operable Unit

SOP standard operating procedure

SQ study question

SSFL Santa Susana Field Laboratory

SVCL soil vapor characterization level

SVOC semivolatile organic compound

SWMU solid waste management unit

TCE trichloroethene

TPH total petroleum hydrocarbons

USEPA United States Environmental Protection Agency

UST underground storage tank

VI vapor intrusion

VI TM Recommended Approach for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, SSFL

VOC volatile organic compound

Water Board California Regional Water Quality Control Board, Los Angeles Region

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SECTION 1

Introduction This comprehensive data quality objective (DQO) report presents a systematic and defensible process for completing the investigation program at the Santa Susana Field Laboratory (SSFL), located in Ventura County, California. The comprehensive DQOs were prepared to facilitate documentation of the weight of evidence to support the corrective measures study (CMS) and conditional no further action (CNFA) recommendations. Significant portions of the site characterization process are substantially complete for many areas of SSFL. The purpose of the comprehensive DQOs is to facilitate completion of the characterization process and transition to the CMS.

This comprehensive DQO report was prepared to address sitewide comments made by the California Environmental Protection Agency, Department of Toxic Substances Control (DTSC) pertaining to DQOs used as the basis of the ongoing site investigation program at the SSFL. For this purpose, The Boeing Company (Boeing) coordinated with the SSFL technical teams, and CH2M HILL prepared this report to provide comprehensive DQOs for use in systematic identification of the remaining site investigation data gap information required to satisfy the current regulatory requirements as part of the SSFL site closure process. Boeing authorized preparation of this report to update and integrate DQOs for all media and operable units (OUs). This DQO report builds on, integrates, and supersedes previous DQOs that were prepared for the SSFL.1 Although this report specifically applies to all Boeing land outside the footprints subject to further evaluation by the National Aeronautics and Space Administration (NASA) and the United States Department of Energy (DOE) under the 2010 Administrative Orders on Consent (AOCs), as depicted in Figure 1, Boeing offers these comprehensive DQOs for all parties’ use going forward, as applicable, in the SSFL site closure process.

The comprehensive DQO process presented herein starts with a flowchart that outlines the process for completing source identification confirmation and weight‐of‐evidence documentation to support CNFA recommendations; Figure 2 depicts this process. Table 1 accompanies Figure 2 and presents assessment methods and activities for identification of a chemical release or potential release. (All tables and figures are provided at the end of this report.) Chemical use areas (CUAs) that were previously identified, or are identified through the process outlined in Figure 2 (using, in part, the sampling methodologies presented in Table 2), will be combined into CUA clusters associated with a Resource Conservation Recovery Act (RCRA) facility investigation (RFI) site. The CUAs will be combined into CUA clusters based on similarities in operational history, geographic proximity, lithologic features, analytical parameters, or previous CMS recommendation areas. The CUA clusters will be carried forward to media‐specific DQO evaluations, performed specifically for surface water bodies, soil and sediment, the vadose zone, and for groundwater and seeps. Each media‐specific DQO evaluation has a companion approach methodology that defines the characterization sampling strategy for that media. In addition, site conceptual models (SCMs) are included to support evaluation of releases, migration pathways, and potential receptors for the various media at SSFL.

Implementation of the systematic and comprehensive DQO process proposed herein will facilitate the following:

Confirm all CUAs have been identified.

Integrate DQOs for all media of concern at SSFL.

Confirm media‐specific DQOs are achieved or data gaps are identified.

Confirm all data and information have been collected to achieve the following:

Address DTSC comments on the draft RFI reports.

Complete documentation of the nature and extent of contamination.

1 The DQOs presented in this report supersede the majority of the RFI DQOs previously prepared for the SSFL. However, these DQOs do not supersede previous DQOs related specifically to the sitewide groundwater monitoring program, RCRA-permitted units, or National Pollutant Discharge Elimination System permit requirements.

1 INTRODUCTION

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Support evaluation of cross‐media/ OU contaminant fate and transport.

Support human health and ecological risk assessments, where required.

Delineate recommended CMS/remedial planning areas and obtain data required for conducting CMS/ remedial planning, where required.

Delineate recommended CNFA areas and the supporting documentation.

Achieve final objectives of the SSFL site investigation program in relation to the site closure process.

The key rationale for preparing the comprehensive DQOs are as follows:

Respond to DTSC Comments. Recent DTSC comments identify specific data gaps that are most efficiently and cost effectively addressed through an integrated media approach to the DQOs.

Integrate Operable Units. The SSFL RCRA corrective action process strategy includes the integration of the Surficial Media Operable Unit (SMOU) and the Chatsworth Formation Operable Unit (CFOU). Hence, the comprehensive DQOs were prepared to address cross‐media and cross‐site impacts because the two OUs are linked as part of one subsurface hydrogeologic system and one overall SCM.

Conform to United States Environmental Protection Agency (USEPA) 2006 DQO Guidance. This comprehensive DQO report was prepared to be compliant with USEPA’s February 2006 Guidance on Systematic Planning Using the Data Quality Objectives Process (USEPA, 2006).

Identify and Address Media‐specific DQOs Gaps. The comprehensive DQOs identify and address media‐specific gaps, including the following:

Vapor Intrusion. The comprehensive DQOs explicitly address the vapor intrusion (VI) pathway, including VI risk to indoor air receptors due to migration from vadose zone sources (SMOU) and from uppermost groundwater sources (which could be located in the SMOU or CFOU).

Air Dispersion. The comprehensive DQOs provide a framework for evaluating chemical impacts to soil resulting from air dispersion and deposition from historical operations.

Integration of Vadose Zone Mass Flux of Contaminants to Groundwater. The comprehensive DQOs address the integrated migration between the vadose zone and groundwater.

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SECTION 2

Relevant SSFL Background Information

2.1 SSFL Setting and Ownership Information The SSFL is located approximately 30 miles northwest of downtown Los Angeles, California, in the southeast corner of Ventura County. The SSFL occupies approximately 2,850 acres of hilly terrain with approximately 1,100 feet of topographic relief. Boeing predecessors began SSFL operations in the 1940s. The SSFL was divided into four administrative areas based on ownership and operations (Areas I, II, III, and IV) and includes undeveloped land areas to both the north and south, as shown on Figure 1. Principal operations in Areas I, II, and III included research, development, and testing of rocket engines and propulsion systems by Boeing and NASA. Principal operations in Area IV included energy technology research for DOE. The northern and southern undeveloped lands of the SSFL are owned by Boeing and were not used for industrial activities.

Currently, the three responsible parties at the SSFL include Boeing, NASA, and DOE. Administrative Areas I and III are operated by Boeing, which owns the majority of Area I and all of Area III. A portion of Area I (42 acres) and all of Area II are owned by the federal government, administered by NASA, and operated by Boeing. Portions of Area IV are owned and operated by Boeing for DOE. DOE owns specific facilities located on approximately 90 acres of Area IV.

2.2 SSFL Regulatory History and Investigation Program Summary

2.2.1 RCRA Corrective Action RFI activities began at the SSFL in 1996. Prior to 1996, activities at the site included:

An initial RCRA facility assessment conducted for USEPA in 1989 (SAIC, 1991).

A Stipulated Enforcement Order issued by DTSC in 1992 (DTSC, 1992).

A RCRA Hazardous Waste Management Facility operating permit issued by DTSC in 1993 (DTSC, 1993).

Three current conditions reports and draft RFI work plans prepared in 1993 (ICF, 1993a, 1993b, and 1993c).

Two RCRA Hazardous Waste Management Facility post‐closure permits issued by DTSC in 1995 (DTSC, 2005a and 2005b).

A RFI work plan addenda prepared in 1996 (Ogden, 1996).

The RFI program is being performed by Boeing, DOE, and NASA in accordance with the August 16, 2007 DTSC Consent Order for Corrective Action (COCA; DTSC, 2007).

Known or potential chemical impacts are the focus of the RCRA corrective action program being conducted under the direction and jurisdiction of DTSC in cooperation with other local, state, and federal regulatory authorities. DTSC identified two OUs:

The SMOU, which includes air, biota, surface water, sediment, saturated and unsaturated soil, saturated and unsaturated weathered bedrock, and groundwater within the alluvium and within weathered bedrock.

The CFOU, which includes the Chatsworth Formation aquifer and both saturated and unsaturated unweathered (competent) bedrock of the Chatsworth Formation.

Historically, the boundary between the OUs has been defined as the contact between weathered and unweathered bedrock.2

2 The boundary between the SMOU and the CFOU occurs at the transition from weathered to unweathered bedrock, which has historically been defined (in consultation with DTSC) as the maximum depth of advancement with a hollow-stem auger. The

2 RELEVANT SSFL BACKGROUND INFORMATION

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2.2.2 Surficial Media Operable Unit Boeing, NASA, DOE, and DTSC divided the SSFL SMOU investigation program into 11 group reporting areas, referred to as RFI groups. For the sake of this comprehensive DQO document, these are referred to as group reporting areas, each comprising a number of individual investigation areas (termed RFI sites). Each of the RFI sites comprises a subset of the 135 named solid waste management units and areas of concern identified at the SSFL that are grouped together based on consideration of common operational, geographic, drainage, and administrative characteristics, shown on Figure 1. With the exception of Group 10, each RFI site contains one or more solid waste management units or areas of concern, and each group reporting area contains from four to 17 RFI sites. RFI Group 10 is situated in the southern undeveloped land portion of SSFL and contains no RFI sites.

The group reporting areas (numbered 1A, 1B, and 2 through 10) are not coincident with the boundaries of Administrative Areas I, II, III, and IV. The group reporting areas were established to provide a comprehensive, integrated description of data from all media across large, interrelated areas of the SSFL. Group reporting areas were identified generally based on natural topographic constraints at the SSFL, but groundwater plume extents, RFI and remedial investigation site responsibility, and operational boundaries were also considered. The SSFL site investigation program for the group reporting areas were conducted both sequentially and concurrently at various RFI sites.

The investigation results and CMS recommendations for each RFI site were presented in the RCRA facility investigation reports and remedial field investigation reports, one or the other was prepared for each of the 11 group reporting areas. The group report documents were submitted to DTSC between September 2006 and November 2009, as identified in the reference list provided in Section 8.

2.2.3 Chatsworth Formation Operable Unit The Draft Site‐Wide Groundwater Remedial Investigation Report, Santa Susana Field Laboratory, Ventura County, California (MWH Americas, Inc. [MWH], 2009a) presents an assessment of the nature and extent of site‐related chemicals and radionuclides in groundwater and vadose zone bedrock across the SSFL. The primary groundwater data gaps proposed for investigation were presented in the Draft Groundwater Remedial Investigation Data Gap Sampling and Analysis Plan, Santa Susana Field Laboratory, Ventura County, California (MWH, 2010) and include the following:

Source characterization for potential impacts to bedrock groundwater

Additional horizontal and vertical extent characterization of volatile organic compound impacts

Additional investigation to characterize the effect of faults on groundwater levels and flow

Additional investigation of seeps

DTSC provided conditional approval of the Draft Groundwater Remedial Investigation Data Gap Sampling and Analysis Plan, Santa Susana Field Laboratory, Ventura County, California (MWH, 2010), but subsequently identified additional data gaps, as documented in DTSC’s comments on the Draft Site‐Wide Groundwater Remedial Investigation Report, Santa Susana Field Laboratory, Ventura County, California (MWH, 2009a; DTSC, 2011a).

The University of Guelph is conducting ongoing work to complete the SCM elements at the SSFL. The current scope of work is focused on the following:

Bedrock matrix and fracture network

Groundwater flow and hydrochemical characteristics

Contaminant migration, transport, and fate

The work is conducted as a series of university research projects that are relevant to ongoing and proposed work at the SSFL, including treatability studies, fault studies, and seep characterization. A key success factor at the SSFL

transition from the SMOU to CFOU is gradational and variable across the site. Although the terms weathered bedrock and unweathered bedrock do not define distinct stratigraphic units, they distinguish regions of the subsurface that have different physical characteristics.


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will be to demonstrate to stakeholders, through multiple lines of evidence, that the SCM is supported and can be used as the basis for the site strategy and to support remedial decision‐making.

2.2.4 Comprehensive and Complete RFI Ultimately, the full contingent of Boeing SMOU RFI reports will be coupled with the sitewide groundwater assessment report and a large home‐range species ecological risk assessment report for the Boeing land outside the NASA and DOE AOC footprints. This is intended to fulfill agency requirements for achieving the objectives of a comprehensive Boeing SSFL RFI that integrates evaluation of all chemical impacts and potential risks associated with those impacts in all media at all locations and provides sufficient data to perform interim measures and/or other evaluations to be conducted as part of the CMS/corrective measure implementation.

2.2.5 Senate Bill 990 On October 14, 2007, the State of California passed Senate Bill 990 (SB990), codified as Section 25359.20 of the California Health and Safety Code. SB990 prescribes cleanup of SSFL, which mandates both the chemical and radioactive cleanup of SSFL and designates DTSC as the lead regulatory agency to oversee the cleanup program. SB990 presents specific cleanup criteria for both chemical and radionuclide constituents and provides for the inclusion of Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) requirements. Boeing, NASA, and DOE began negotiating a revised Consent Order or comparable cleanup agreement with DTSC with the intent that the work elements required to complete the SMOU and CFOU RFI reporting project work, or equivalent, would be revised once the terms and conditions of a final Consent Order or cleanup agreements were established.

Boeing continues to support the goal of a comprehensive agreement between all of the parties to accelerate the SSFL cleanup process. However, in September 2009, Boeing filed a federal lawsuit contesting the enforceability of the SB990 legislation, asserting that SB990 is preempted by federal laws governing the SSFL cleanup and that Boeing should be released from compliance with SB990.

On April 26, 2011, the United States District Court for the Central District of California ruled in Boeing’s favor and granted relief with respect to Boeing’s motions. On April 27, 2011, the California Environmental Protection Agency announced its plans to appeal the judge’s decision. Boeing is committed to continue cleanup actions at the SSFL while the SB990 issue is in federal court. Until the applicability of SB990 is finally resolved, Boeing’s SSFL cleanup actions are being conducted under the COCA (DTSC, 2007).

The Boeing RFI‐required characterization levels, which apply to the Boeing land outside the NASA and DOE AOCs, as identified in Figure 1, ultimately could be background chemical concentrations, method reporting limits (MRLs), or other agreed‐upon risk‐based concentrations. Because of the uncertainty associated with the final RFI requirements, the comprehensive soil and sediment DQOs refer to “required characterization levels” and reference that these could be based on background chemical concentrations, MRLs, or risk‐based concentrations, depending upon final resolution of SB990 for Boeing and the respective applicability of the AOC requirements for DOE and NASA, if they choose to use this document for the AOC portions of their work.

2.2.6 DTSC Administrative Orders on Consent On December 6, 2010, DTSC signed an AOC for remedial action with both DOE and NASA (one each, resulting in two separate AOCs) that define the process for characterization and the cleanup end‐state for portions of the SSFL. The December 2010 AOCs supersede the 2007 DTSC COCA requirements pertaining to soil cleanup and specifically define “cleanup of soil” and DOE’s and NASA’s required obligations and responsibilities. The AOCs do not in any way operate to modify, amend, or nullify the obligations of Boeing, DOE, and NASA under the 2007 COCA.

The purpose of the AOCs is to further define and make more specific DOE’s and NASA’s obligations with respect to only the cleanup of soils at the SSFL. The NASA AOC requires NASA to prepare a field sampling plan (FSP) for NASA‐administered sites within SSFL Groups 2, 3, 4, and 9. The DOE AOC requires DOE to prepare a work plan/ FSP for the property within Administrative Area IV and the adjacent Northern Buffer Zone (NBZ), which includes


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portions or all of the SSFL Groups 5, 6, 7, and 8 and the adjacent northern undeveloped land area. The FSPs described above are being followed by subsequent site‐specific FSP addenda. Figure 1 presents the portions of the SSFL subject to the DOE and NASA AOCs.

Under the AOCs, soils to be investigated include saturated and unsaturated soil, sediment and weathered bedrock, debris, structures, and other anthropogenic materials. The term “soils” does not include surface water, groundwater, air, or biota. Under the AOCs, “cleanup of soils” does not include the cleanup of volatile organic compounds that are found in the groundwater, soil, or bedrock below the groundwater level. Likewise, the AOCs do not include the cleanup of volatile organic compounds that emanate from groundwater contaminated with volatile organic compounds that migrate into and through the saturated and unsaturated soil and bedrock at SSFL.

DOE has initiated shallow soil characterization under the 2010 DOE AOC, consistent with the Master Work Plan/Field Sampling and Analysis Plan, Co‐Located Chemical Sampling at Area IV, Santa Susana Field Laboratory, Ventura County, California (CDM Federal Programs Corporation [CDM], 2011) and the Work Plan for Chemical Data Gap Investigation Phase 3 Soil Chemical Sampling at Area IV, Santa Susana Field Laboratory, Ventura County, California (CDM, 2012). In March 2011, NASA submitted the Draft Remedial Investigation Work Plan for NASA Sites at the Santa Susana Field Laboratory, Ventura County, California (NASA, 2011), which included a master FSP, in accordance with the 2010 NASA AOC. NASA is also submitting subsequent FSP addenda for specific areas. The soil cleanup levels required under the AOCs are to be determined by DTSC based on work underway to establish background chemical concentration levels and analytical laboratory MRLs.

2.2.7 Radiological Constituents Concurrent with the ongoing chemical investigation programs, a radiological background study and a radiological characterization survey of the SSFL Administrative Area IV and the adjacent NBZ is being performed under the technical direction and oversight of USEPA Region 9. These efforts are part of the activities USEPA is conducting pursuant to House Resolution 2764, P.L. 110‐161—work that is funded pursuant to an interagency agreement between DOE and USEPA. In accordance with House Resolution 2764, DOE is funding USEPA’s radiological study. The DOE AOC stipulates the soils cleanup of the SSFL Administrative Area IV and the NBZ shall result in an end state of the site consistent with “background” (with the exception of the exercise of the exceptions that are specifically expressed in the September 3, 2010 Final Agreement in Principle).

2.2.8 Non-AOC Investigation The non‐AOC chemical site investigation work (all SSFL media other than “soils,” as defined in the AOCs) for Boeing, NASA, and DOE is to comply with the COCA (DTSC, 2007) and potentially SB990. Consequently, with the exception of the AOC‐focused investigation and cleanup of “soils,” all other site investigation work is proceeding in a coordinated manner, and the remaining investigation data gap requirements or demonstration of characterization completeness can be considered in the context of the comprehensive DQOs presented herein. Boeing proposes to use the comprehensive DQOs to identify the remaining RFI data gaps. DOE and NASA may decide to also use the comprehensive DQOs for non‐AOC‐related data gap identification.

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SECTION 3

Summary of Regulatory Comments and Requirements DTSC has transmitted draft or final comments for the group RFI reports, including comments on portions or all of the Groups 1A, 1B, 2, 3, 4, 5, 6, 7, 8, 9, and 10 reports. DTSC has provided comments on the December 2009 Draft Site‐Wide Groundwater Remedial Investigation Report, Santa Susana Field Laboratory, Ventura County, California (MWH, 2009a) and has conditionally approved the March 2010 Draft Groundwater Remedial Investigation Data Gap Sampling and Analysis Plan, Santa Susana Field Laboratory, Ventura County, California (MWH, 2010). DTSC’s comments were prepared by the Geological Services Unit, the DTSC Geological Services Unit SSFL groundwater lead, and by the DTSC SSFL lead human health and ecological risk assessors from the DTSC Human Health and Ecological Risk Office. Based on comments received to date, the following general comment categories were identified by DTSC reviewers:

General Issues

Acknowledge outstanding issues: SB990, chemical background, MRLs

Quality Assurance Project Plan and DQO updates: use latest regulatory guidance

Source Identification

Historic records review completeness, including documents and aerial photographs

Sitewide fluid/gas storage and distribution features, and infrastructure: coordinated sitewide compilations and assessments

Site Characterization (nature and extent delineation)

Chemical contaminant source identification versus CNFA documentation

Contaminant nature and extent characterization completeness

Soil vapor investigation, risk assessment, remedial planning information

Surface water runoff characterization in focused locations

Mass flux to groundwater (fate‐and‐transport evaluation)

Vertical delineation and bedrock investigations: complete characterization of contaminants

Contaminant mass flux to groundwater evaluation

Characterize surface sources/contaminant releases to groundwater

Groundwater and Seeps

Groundwater characterization/evaluation

Characterize the effect of faults on groundwater levels and flow

Additional investigation of seeps

DTSC’s 2011 comments acknowledge that there are both common and unique regulatory drivers for the responsible parties at SSFL—Boeing, NASA, and DOE. Where party‐specific regulatory drivers or yet‐to‐be finalized drivers apply to the DQOs, generic terms and footnotes have been included in this document so that the comprehensive DQOs can be applicable to all parties and are flexible to accommodate future changes and final agreements.

Common regulatory drivers include Boeing, DOE, and NASA collaboration for all but the AOC scopes of work. Note that the SMOU RFI work performed under the COCA (DTSC, 2007) typically evaluates “surface” soil at depths of 0 to 2 feet below ground surface (bgs) and incorporates risk assessment exposure scenarios for “shallow” soil at

3 SUMMARY OF REGULATORY COMMENTS AND REQUIREMENTS

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depths of 0 to 10 feet bgs. The AOC criteria do not appear to be depth limited but rather are dependent upon contaminant concentrations at any depth and only limited by media and groundwater level (saturated materials).

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SECTION 4

Rationale and Scope of Comprehensive Data Quality Objectives This comprehensive SSFL DQO report builds on, integrates, and supersedes previous OU‐specific DQOs, including those previously presented in the Quality Assurance Project Plan, Santa Susana Field Laboratory RCRA Facility Investigation Surficial Media Operable Unit (MECx, 2012) and the RFI Program Report, Surficial Media Operable Unit, Santa Susana Field Laboratory, Ventura County, California (MWH, 2004). The key rationale for preparing the comprehensive DQOs includes the following:

DTSC comments identify specific data gaps, which are most‐efficiently and cost‐effectively addressed through an integrated media approach to the DQOs that acknowledges and addresses the iterative nature of the DQO process.

The SSFL RCRA corrective action process strategy includes the integration of the OUs and, hence, because the two OUs are inextricably linked as part of one subsurface hydrogeologic system and one overall SCM, the comprehensive DQOs address cross‐media and cross‐site impacts.

This comprehensive DQO document for the SSFL site investigation program conforms to the latest USEPA DQO guidance, Guidance on Systematic Planning Using the Data Quality Objectives Process (USEPA, 2006), and includes the seven‐step process shown on Figure 3.

The comprehensive DQOs present the process for identifying and investigating new releases or potential releases for all portions of each reporting area (within and outside of previously identified CUAs). This process supports the identification of all CUAs within each group reporting area and also supports the identification of the portion of each reporting area appropriate for a CNFA recommendation.

The comprehensive DQOs address media‐specific gaps, including the following:

Vapor Intrusion. The comprehensive DQOs explicitly address the VI pathway, including VI risk to indoor air receptors due to migration from vadose zone sources (SMOU) and from uppermost groundwater sources (which could be located in the SMOU or CFOU).

Air Dispersion. The comprehensive DQOs provide a framework for evaluating chemical impacts to soil resulting from air dispersion and deposition from historical operations.

Integration of Vadose Zone Mass Flux of Contaminants to Groundwater Evaluation and Modeling. The comprehensive DQOs address the integrated migration between the vadose zone and groundwater.

The 2007 strategy for the SSFL RCRA corrective action process administratively separates the SMOU from the CFOU; however, the two units are linked as part of one subsurface hydrogeologic system and one overall SCM.

For the SMOU, Boeing, DOE, and NASA performed field investigations of source areas in surficial media, in accordance with the RFI work plans, to determine contaminant nature and extent and fate and transport within the SCM framework and to integrate data for the SMOU and CFOU to identify source areas, chemicals of potential concern, and potential cross‐media impacts in SMOU RFI reports. For the CFOU, Boeing, DOE, and NASA proposed to identify and characterize all sources of contamination and to define the nature and extent of contamination in the CFOU. This included characterizing potential contaminant pathways, rates, and directions of migration and refinement of a comprehensive and detailed SCM for the flow of groundwater and transport of contaminants within the Chatsworth Formation in the vicinity of SSFL. Notwithstanding the DOE and NASA AOC stringent soils cleanup standards and reporting requirements, most of the site strategies identified in 2007 are still applicable to the SSFL and ongoing cleanup program.

Boeing, DOE, and NASA are clearly at different points in the regulatory process, based on the signing of the 2010 AOCs concurrent with the ongoing SSFL site investigation programs, coupled with resolution of DTSC’s site‐specific

4 RATIONALE AND SCOPE OF COMPREHENSIVE DATA QUALITY OBJECTIVES

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and sitewide comments. It is acknowledged that uncertainty remains regarding the amount and type of additional analysis, methods, and data that will be required to successfully characterize the SSFL. It is also acknowledged that the site investigation program is an iterative process and that, regardless of the current progress or status of the work, compilation of comprehensive DQOs consistent with the latest DQO guidance provides a useful framework for the systematic evaluation of all pertinent information and assembling the required documentation to facilitate regulatory decisions. Consequently, these comprehensive DQOs have been prepared by Boeing with the intention that they could also be used by NASA and DOE for the non‐AOC portions of the SSFL site characterization work. The DQO guidance document (USEPA, 2006) presents a useful diagram that depicts the iterative nature of the DQO process, with a “barrel roll” that tracks the lifecycle components of a project, as shown on Figure 4.

Portions of the SSFL investigation program are still in the CUA identification stage. Other portions of the program are completing the nature and extent characterization or fate‐and‐transport analysis, and some more advanced portions have moved through the RFI process and have been recommended for CMS/remedial planning. The comprehensive DQOs are intended to identify and address all CUAs and CUA clusters at SSFL, regardless of their current stage in the SSFL site investigation program.

Two field and four laboratory treatability studies were proposed in June 2009 (MWH, 2009b). The work plan for the treatability studies was conditionally approved by DTSC. Clearly, the RCRA corrective action program at the SSFL is making progress toward development of a site closure strategy, although it is recognized that further characterization and remedial testing will provide refinement of the strategy. Although portions of the SSFL site investigation program are nearing completion, a comprehensive DQO process is needed to finalize the identification of all CUAs, provide the framework to systematically evaluate all media in a consistent manner, and document recommendations for CNFA areas. It is anticipated that DTSC will require this to support regulatory concurrence.

The Master RFI Data Gap Work Plan, Santa Susana Field Laboratory, Ventura County, California (Master RFI Data Gap Work Plan) (CH2M HILL, 2013a) presents the proposed process and schedule for completing the RFI work for the Boeing areas of SSFL that are not subject to the DOE or NASA AOCs. The Boeing areas have been organized into nine RFI subareas, and an addendum to the Master RFI Data Gap Work Plan will be prepared for each Boeing RFI subarea. Each addendum will present the data gaps identified through application of the comprehensive DQO process for each Boeing RFI subarea. The addenda will also present the plan for addressing the identified data gaps. After the identified data gaps are filled, each Boeing RFI subarea will be evaluated in the context of the comprehensive DQOs to identify any additional data gaps. This process is repeated until all data gaps are identified and filled. After receiving DTSC’s concurrence that characterization for a Boeing RFI subarea is complete and the DQOs have been satisfied, Boeing will prepare a draft RFI data summary and findings report for that subarea. These reports will present an evaluation of analytical and field data and CMS and CNFA recommendations for each Boeing RFI subarea.

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SECTION 5

Content of the Comprehensive Data Quality Objectives The components of the comprehensive DQOs are listed in Section 1 and are described in this section. The DQO tables referenced in this section are included at the end of this report. The comprehensive DQOs are compliant with DQO guidance (USEPA, 2006) and reflect the current status of the SSFL site investigation program/process (that is, all group reports have been submitted, DTSC has commented on the group reports, responses to DTSC comments and data gap sampling and analysis plans [SAPs] are in preparation, and the majority of required site investigation data and sitewide infrastructure systems and historical aerial photograph documentation have been compiled). Implementation of the systematic and comprehensive DQO process will facilitate the following:

Confirm the identification of all contaminant sources and documentation of CNFA areas.

Update and integrate the DQOs for all media of concern at the SSFL.

Confirm media‐specific DQOs achieved or data gaps identified for the following media:

Surface water bodies

Soil and sediment

Vadose zone (mass flux to groundwater and indoor air quality)

Groundwater and seeps

Confirm all data/information are collected to achieve the following:

Address DTSC comments on the draft group reports.

Complete documentation of the nature and extent of contamination.

Evaluate volatilization from groundwater to the vadose zone.

Evaluate soil vapor migration from the vadose zone to indoor air.

Evaluate vadose zone mass flux of contaminants to groundwater.

Support human health and ecological risk assessments, where required.

Delineate recommended CMS/remedial planning areas and obtain data required for conducting CMS/ remedial planning.

Delineate recommended CNFA areas and prepare weight‐of‐evidence documentation to support the recommendation.

Obtain DTSC’s concurrence that the SSFL site investigation program is complete and that sufficient data have been collected to transition into the CMS stage of the RCRA corrective action process.

The comprehensive DQO process is an iterative effort, which cycles through the characterization process to systematically evaluate and assemble the documentation required to complete the RFI process and achieve the overall objectives of this phase of the RCRA corrective action program or equivalent RI phase of CERCLA. Performance and acceptance criteria to complete the RFI process are developed through the comprehensive DQO process. Existing data are compared to the criteria to identify areas where additional data are required. After the additional data are collected, the data are again compared against the criteria to evaluate if the criteria have been achieved. This cycle continues in an iterative manner until all criteria have been achieved, as illustrated in Figure 4.

A flow chart of the proposed DQO process is presented in Figure 5. This process starts with completion of the RCRA‐facility‐assessment‐related activities, including confirming source identification, developing weight‐of‐evidence documentation to support a CNFA recommendation for appropriate areas of the SMOU, and

5 CONTENT OF THE COMPREHENSIVE DATA QUALITY OBJECTIVES

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assembling remaining areas into CUA clusters that are subject to the DQO process. The arrows among the four media‐specific tables in Figure 5 represent the potential cross‐media mass flux among media (for example, between the vadose zone and groundwater and between groundwater and surface water). Also shown in Figure 5 is the property description terminology that is referenced within the RFI reporting process and that is used in this comprehensive DQO report.

Tables 3 through 10 of this report present the DQOs and sampling approach methodologies for surface water bodies, soil and sediment, vadose zone, and groundwater and seeps. Each DQO table consists of five study questions, which will be evaluated sequentially, starting with Study Question (SQ) #1. For each DQO table, SQ #4 (CNFA or cleanup assessment) will be answered after the DQOs for SQs #1 through #3 in the same DQO table have been satisfied. For the Boeing areas, human health and ecological risk assessments will be performed under SQ #4 in accordance with the Standard Risk Assessment Methodology Work Plan, Revision 2 Addendum (SRAM Rev.2, MWH, pending) and in accordance with the technical memorandum, Integration of the Surficial Media Operable Unit Risk Assessment Methodology with the Data Quality Objectives Process, Boeing RCRA Facility Investigation, SSFL (CH2M HILL, 2013b), which is included as Appendix C.

5.1 Site Conceptual Models The following three SCMs have been developed to represent site conditions at the SSFL and to evaluate the DQOs:

CUA and CUA cluster‐scale SCM (Figure 6)

Deep soil and groundwater plume‐scale SCM (Figure 7)

SSFL sitewide facility‐scale SCM (Figure 8)

These SCMs are consistent with SCMs previously published in Draft Site‐Wide Groundwater Remedial Investigation Report, Santa Susana Field Laboratory, Ventura County, California (MWH, 2009a) and the Site Conceptual Model for the Migration and Fate of Contaminants in Groundwater at Santa Susana Field Laboratory, Simi, California (MWH, 2009c).

The CUA and CUA cluster‐scale SCM shown on Figure 6 is used in conjunction with Tables 3, 5, and 7 to address releases from CUAs to surface water bodies, soil, sediment, and the vadose zone (and between surface water and groundwater in DQO Table 3). The deep soil and groundwater plume scale SCM on Figure 7 is used in conjunction with Tables 7 and 9 to address onsite vadose zone and groundwater cross‐media questions (between the vadose zone and indoor air, between the vadose zone and burrowing ecological receptors, between the vadose zone and groundwater, and between groundwater and indoor air). The SSFL sitewide facility scale SCM on Figure 8 is used in conjunction with Table 9, addressing groundwater cross‐media migration pathways (between the vadose zone and groundwater and between groundwater and indoor air) and receptors (between groundwater and seeps and offsite wells). The SCMs are also referenced in the following sections that describe the comprehensive DQO process.

5.1.1 CUA Confirmation and CNFA Area Documentation All land within each Boeing RFI subarea will be evaluated to determine if a release or potential release of any chemical previously used, stored, handled, or disposed of at an area of interest is located within the Boeing RFI subarea. The releases and potential releases are identified and documented in accordance with Figure 2, which presents the specific process for CUA confirmation and CNFA area weight‐of‐evidence documentation for the SMOU. As presented on Figure 2, the following five methods to evaluate the Boeing RFI subarea will be implemented to accomplish the objectives of Figure 2: (1) document and record review, (2) SSFL sitewide inventories, (3) SSFL sitewide comprehensive inspections and documentation, (4) RFI site‐specific inspections and documentation, and (5) chemical migration assessment. The activities associated with these five methods are described in detail in Table 1. Review of historical SSFL documents, which is a component of Method 1: Document and Record Review, is performed in accordance with the Boeing SSFL historical document review flowchart presented on Figure 9.


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If a release or potential release of any chemical previously used, stored, handled, or disposed of at a feature is identified through the Figure 2 process, then one of the following will occur:

The feature is added to an existing CUA.

The feature is identified as a new CUA (if there is clear documentation that indicates there was a release of any chemical previously used, stored, handled, or disposed at the area of interest).

Screening‐level samples are collected following the feature type‐specific sampling and analysis strategy outlined in Table 2 to determine whether the feature constitutes a new CUA or whether it should be recommended for CNFA.

The process presented in Figure 2 is intended to be ongoing and iterative. Figure 2 will ultimately facilitate the identification of all CUAs and associated chemicals in each Boeing RFI subarea.

Each new and existing CUA will then be grouped with a new or existing CUA cluster. CUA clusters consist of one or more CUAs within an RFI site that are essentially collocated or adjacent to each other such that they can be combined based on similarities in geographic proximity, operational history, lithologic features, analytical parameters, previous CMS recommendation areas, and locations of dense nonaqueous‐phase liquid (DNAPL) sources/ releases. CUA clusters include the full extent of identified impacts (above characterization levels) associated with the CUAs. The new and previously identified CUA clusters are then subject to the media‐specific DQO process presented in Tables 3 through 10 (described in the following sections).

The Figure 2 process also allows for portions of the subarea where a release or potential release of any chemical was not identified (through the Figure 2 process) to be recommended for CNFA. Multiple lines of evidence will be used and documented to support the CNFA recommendation.

5.1.2 Surface Water Bodies Data Quality Objectives and Sampling Strategy Table 3 identifies the DQOs for study questions related to identification of sources and chemicals, nature and extent, fate and transport, cleanup assessment, and remedial planning for perennial surface water bodies at the SSFL. The CUA and CUA cluster‐scale SCM presented in Figure 6 is used in conjunction with Table 3 to address releases, migration pathways, and potential receptors for perennial surface water bodies at the SSFL. Characterization samples are collected from sediment beneath the surface water body and from soil in upstream and downstream pathways in accordance with Table 4 to address Table 3 SQ #2 (nature and extent of contamination). Because perennial surface water bodies are not addressed in the 2010 AOCs or associated DQOs, Table 3 is applicable to Boeing, DOE, and NASA.

5.1.2.1 Extent of Surface Water Impacts Surface water bodies, such as ponds, are identified as RFI sites and/or CUAs and are evaluated as part of a CUA cluster in Table 3. Outside of perennial surface water bodies, surface water is monitored, evaluated, and managed under the National Pollutant Discharge Elimination System program, which is administered by the California Regional Water Quality Control Board, Los Angeles Region (Water Board). Surface water drainage, such as sheet flow or channel flow, is evaluated at each CUA cluster as a potential migration pathway for contaminant transport. This potential migration pathway from a CUA is considered within the DQO framework (SQ #3 in Tables 3 and 5) for migration of contaminated surface soil from CUAs.

5.1.2.2 Surface Water Mass Flux of Contaminants to Groundwater Table 3, SQ #3 (fate and transport) and SQ #4 (CNFA or cleanup assessment) addresses surface water mass flux of contaminants to groundwater. Surface water mass flux of contaminants to groundwater is also represented on the CUA and CUA cluster‐scale SCM on Figure 6. Because of the relatively small distance between the base of the large perennial surface water bodies at the SSFL (for example, the Silvernale or Perimeter Ponds) and the uppermost groundwater surface, fate‐and‐transport modeling is not recommended to evaluate potential impacts from surface water to groundwater. Instead, surface water bodies will be recommended for remedial planning if chemicals detected above surface water action levels in a surface water body are also detected in underlying


5-4

and/or downgradient groundwater at concentrations above the corresponding groundwater characterization level (GCL).

5.1.3 Soil and Sediment Data Quality Objectives and Sampling Strategy (Applicable to Boeing Only)

Table 5 identifies the DQOs for study questions related to identification of sources and chemicals, nature and extent, fate and transport, cleanup assessment, and remedial planning for soil and sediment. Tables 5 and 6 apply to Boeing only and will be used to support future human health and ecological risk assessments. The DQO tables included in the Draft Remedial Investigation Work Plan for NASA Sites at the Santa Susana Field Laboratory, Ventura County, California (NASA, 2011), the Master Work Plan/Field Sampling and Analysis Plan, Co‐Located Chemical Sampling at Area IV, Santa Susana Field Laboratory, Ventura County, California (CDM, 2011), and the Work Plan for Chemical Data Gap Investigation Phase 3 Soil Chemical Sampling at Area IV, Santa Susana Field Laboratory, Ventura County, California (CDM, 2012) present the DQOs for soils in SSFL areas for which NASA or DOE is the responsible party.

The CUA and CUA cluster‐scale SCM presented on Figure 6 is used in conjunction with Table 5 to address releases, migration pathways, and potential receptors for soil and sediment at SSFL. Boeing proposes to collect characterization (step‐out and step‐down) samples from soil or sediment in accordance with Table 6 to address DQO SQ #2 (nature and extent of contamination). In general, characterization of soil and sediment continues laterally and vertically (following the strategy outlined in Table 6) until detected concentrations are below the required soil characterization levels or until refusal is reached with a direct‐push rig, whichever is shallowest.

As discussed in the previous section, surface water drainage as sheet flow or channel flow is evaluated as a potential migration pathway for contaminant transport from CUAs in Table 5, SQ #3 (fate and transport of contamination). Similarly, the transport of dust by air pathway (air dispersion and deposition of airborne materials) is evaluated as a potential migration pathway for contaminant transport in Table 5, SQ #3 for appropriate CUA clusters, as applicable. The technical memorandum, Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, SSFL (CH2M HILL, 2013c), is intended to guide decision‐making on which sources are modeled and how the modeling will be conducted. This technical memorandum is presented in Appendix B. Migration through subsurface soil is also evaluated as a potential migration pathway for contaminant transport in Table 5, SQ#3. The indoor air migration pathway is addressed in Table 7.

5.1.4 Vadose Zone Data Quality Objectives and Sampling Strategy Table 7 identifies the DQOs for study questions related to identification of sources and chemicals, nature and extent, fate and transport, cleanup assessment, and remedial planning for the vadose zone (unsaturated soil [alluvium], weathered bedrock, and bedrock present between the ground surface and the water table). The key subject matters that are addressed in Table 7 include indoor air quality, vadose zone mass flux of contaminants to burrowing ecological receptors, and vadose zone mass flux of contaminants to groundwater. The SCMs presented on Figures 6 and 7 are used in conjunction with Table 7 to address vadose zone cross‐media questions (between the vadose zone and indoor air, between the vadose zone and burrowing ecological receptors, and between the vadose zone and groundwater) within a CUA and CUA cluster (Figure 6) and above a downgradient groundwater plume (Figure 7). Because these migration pathways/ receptors are not addressed in the 2010 AOCs or associated DQOs, Table 7 is applicable to Boeing, DOE, and NASA.

5.1.4.1 Soil Vapor/Indoor Air Quality CH2M HILL prepared the technical memorandum Recommended Approach for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, SSFL (VI TM) (CH2M HILL, 2013d). The VI TM is included as Appendix A. The VI TM presents a brief overview of the Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air (VI guidance, DTSC, 2011b). The VI assessment approach provides a systematic and defensible process that relies on multiple lines of evidence for completing the assessment part of the RFI to identify areas where the VI pathway is potentially complete and significant. Recommended actions to address VI at the SSFL are presented in the VI TM based on the VI guidance, the DQO evaluation process, RFI work performed


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to date, and DTSC comments received to date. The proposed DQOs and sampling approach methodologies presented in the VI TM are incorporated into Tables 7 and 8.

Table 8 describes the sampling strategy to sufficiently characterize soil vapor to support VI assessments. In general, characterization of soil vapor continues (following the strategy outlined in Table 8) until detected concentrations are below the required soil vapor characterization levels (SVCLs) or until refusal is reached with a direct‐push rig, whichever is shallowest. Table 8 identifies the criteria for collecting subslab, indoor air, and outdoor samples to support a VI assessment. The SVCLs for evaluating indoor air quality are presented in the VI TM in Appendix A. Following collection of the soil vapor samples, the need to collect additional soil vapor samples above groundwater plumes located downgradient of CUA clusters will be evaluated on a plume‐specific basis, giving consideration to lithologic conditions and soil vapor and groundwater chemical data.

5.1.4.2 Vadose Zone Mass Flux of Contaminants to Burrowing Ecological Receptors Vadose zone mass flux of contaminants to burrowing ecological receptors is addressed in Tables 7 and 8 and on Figure 6. Ecological receptors are expected to burrow up to 6 feet bgs in unconsolidated material (alluvium). Table 8 describes the sampling strategy to sufficiently characterize soil vapor to support evaluations of potential exposures of burrowing ecological receptors to volatile organic compounds in soil vapor. In general, characterization of shallow soil vapor (in the upper 6 feet) continues (following the strategy outlined in Table 8) until detected concentrations are below the required SVCLs or until refusal is reached with a direct‐push rig, whichever is shallowest. The SVCLs for evaluating the burrowing ecological receptor exposure pathway (low toxicity reference values) are presented in Inhalation Toxicity Reference Value Updates for Use in Ecological Risk Assessments at the Santa Susana Field Laboratory, Ventura County, California ‐ Technical Memorandum (MWH and CH2M HILL, 2011).

5.1.4.3 Vadose Zone Mass Flux of Contaminants to Groundwater Vadose zone mass flux of contaminants to groundwater will be evaluated in accordance with Table 7 and the analytical approach/decision rules presented in Figure 10. The CUA and CUA cluster‐scale SCM on Figure 6 and the deep soil and groundwater plume scale SCM on Figure 7 are applicable to the vadose zone mass flux of contaminants to groundwater evaluation. In evaluating this migration pathway, Table 7 SQ #2 (nature and extent of vadose zone contamination), SQ #3 (fate and transport of mobile constituents in the vadose zone toward groundwater), and SQ #4 (decision‐making process to determine if the vadose zone at a CUA cluster should be carried forward for remedial planning) consider constituent concentrations and trends with depth, plume stability, groundwater migration and modeling results, and the location of DNAPL source areas associated with rocket engine or equipment testing. Deep borings to groundwater will be advanced at locations identified in accordance with Table 7 and following the analytical results/decision rules presented on Figure 10. To evaluate

the presence or extent of chemical impacts to groundwater, sampling results will be compared to background threshold values (BTVs) for chemicals where such values have been established or GCLs. GCLs are based on the following rank order:

1. The lower of federal or state primary drinking water maximum contaminant levels

2. Notification levels established by the California Department of Public Health (CDPH) (Water Board, 2008; CDPH, 2010a)

3. Archived advisory levels established by the CDPH (2010b)

4. Secondary maximum contaminant levels, which address aesthetics, such as taste and odor (Water Board, 2008; CDPH, 2011)

5. Taste and odor threshold (Water Board, 2008)

6. Site‐specific values developed for SSFL using risk assessment procedures assuming direct ingestion of groundwater.

The methodology used to develop the risk‐based screening values for chemicals that are not metallic elements and where there are no agency‐published values is described in a technical memorandum included in


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Appendix 7‐C of the Draft Site‐Wide Groundwater Remedial Investigation Report, Santa Susana Field Laboratory, Ventura County, California (MWH, 2009a). In cases where the secondary maximum contaminant limit (MCL) is lower than the primary MCL, the secondary MCL is used. Additionally, for those chemicals where DTSC has established GCLs (that is, metals), DTSC’s specified GCL is selected if it is lower than any values in the rank order described above.

Previous investigation results and deep boring results will be used to model the mass flux of contaminants from the vadose zone to groundwater, if needed, in accordance with the methodology presented in the technical memorandum, Recommended Approach for Evaluating Vadose Zone Mass Flux of Contaminants to Groundwater, Boeing RCRA Facility Investigation, SSFL (MWH, 2013), included as Appendix D. The need for mass flux modeling is addressed under SQ #3 (fate and transport) and Figure 10. The outcome of SQ #4 (CNFA or cleanup assessment) will be based on multiple lines of evidence, including field data, a comparison of the soil/ rock/ soil vapor concentrations with the groundwater concentrations and, if warranted, the estimated concentrations of chemicals migrating to groundwater based on the mass flux of contaminants to groundwater fate‐and‐transport analysis. Specifically, CUA clusters will be recommended for remedial planning if groundwater concentrations exceed the GCLs, based on the modeled mass flux from the vadose zone.

5.1.5 Groundwater and Seeps DQOs and Sampling Strategy Table 9 identifies the DQOs for study questions related to identification of sources and chemicals, nature and extent, fate and transport, cleanup assessment, and remedial planning for groundwater and seeps. The SCMs presented on Figures 7 and 8 are used in conjunction with Table 9 to address groundwater cross‐media migration pathways (between the vadose zone and groundwater and between groundwater and indoor air) and receptors (between groundwater and seeps and offsite wells). Table 10 identifies the sampling and analysis strategy for characterizing the lateral and vertical extents of constituents in groundwater, including criteria for selecting the locations of new groundwater monitoring wells. The fate and transport of groundwater is considered in Table 10, SQ #3, under which plume stability and natural attenuation are evaluated through review, analysis, and evaluation of site‐specific data. Because groundwater is not addressed in the 2010 AOCs or associated DQOs, Table 9 is applicable to Boeing, DOE, and NASA.

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SECTION 6

Summary and Conclusions The SSFL characterization program completion is supported by these comprehensive DQOs. The proposed comprehensive DQOs are compliant with USEPA’s 2006 DQO guidance and reflect the overarching SSFL sitewide strategy. The comprehensive DQOs provide a systematic and defensible structure for completing the SSFL site investigation program and documenting the weight of evidence to support CMS and CNFA recommendations. The comprehensive DQO report will enable the SSFL technical teams and regulators to systematically identify all remaining key site investigation data gaps, and it documents the field investigation methodologies to address those data gaps. The comprehensive DQOs add value to Boeing, and DTSC (and also DOE and NASA, if they choose to use them) by facilitating a focused evaluation of existing site information that integrates OUs to evaluate cross‐media impacts and identify specific requirements to satisfy the completion of SSFL site investigation program objectives.

The systematic comprehensive DQO process will facilitate identification of only the specific required investigations (identification of focused data gaps, limiting additional site investigation) and does not promote investigation for the sake of investigation. Implementation of the comprehensive DQOs will enable Boeing and DTSC (and also DOE and NASA, if they choose to use them) to expedite completion of the site investigation program and move efficiently toward remedial planning and implementation in a manner focused on reaching site closure.

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SECTION 7

Glossary of Terms This section presents a brief glossary of select terms commonly used within this comprehensive DQO report.

Chemical Use Area (CUA): Areas of known or potential chemical use, storage, handling, or disposal within each of the RFI/RI reporting areas.

CUA Cluster: A grouping of one or more CUAs that are combined based on similarities in geographic proximity, operational history, lithologic features, analytical parameters, previous CMS recommendations, and locations of DNAPL sources/releases. CUA clusters consist of one or more CUAs and include the full extent of identified impacts above characterization levels.

Conditional No Further Action (CNFA) Recommendation: A no further action recommendation that is based on current site information and weight‐of‐evidence data but that is considered conditional pending resolution of SB990 and determination of background concentrations, MRLs, and final regulatory requirements. Also, CNFA recommendations will be reviewed upon demolition of remaining structures in consideration of observations and data collected in accordance with the Standard Operating Procedures: Building Feature Evaluation and Sampling, Revision 1, Santa Susana Field Laboratory, California (MWH and CH2M HILL, 2009) to assess the potential for chemical impacts beneath buildings.

Plume: A contiguous area of groundwater contamination resulting from one or more vadose zone sources. Plume extent is bounded laterally and vertically by concentrations at or below the required GCLs. Professional judgment is also used in evaluating plume extent.

RCRA Facility Investigation Site (RFI site): as previously defined in SMOU group reports.

Boeing RFI Subarea: all Boeing SSFL land subject to evaluation under the comprehensive DQO process in an individual master RFI data gap work plan addendum. This land typically consists of one or more Boeing RFI sites and the surrounding land.

Sediment: Material at the bottom of perennial surface water features but that does not include soil in ephemeral streambeds.

Surface Water: Considered as the following:

“Surface water drainage,” such as sheet flow or channel flow, where surface water runoff could cause migration of surface soil. This drainage was evaluated as a potential migration pathway from a CUA.

“Surface water features,” such as water bodies, such as ponds, where water accumulates and that were evaluated as a potential source of contamination under the SMOU RFI.

Vadose Zone: Unsaturated soil (alluvium), weathered bedrock, and bedrock present between the ground surface and the water table.

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References California Department of Public Health (CDPH). 2010a. Drinking Water Notification Levels and Response Levels:

An Overview. December 14.

CDPH. 2010b. CDPH’s Archived Advisory Levels for Drinking Water. December.

CDPH. 2011. California Regulations Related to Drinking Water. September 22.

California Environmental Protection Agency, Department of Toxic Substances Control (DTSC). 1992. Docket HWCA Stipulated Enforcement Order. November 16.

DTSC. 1993. Operating Permit for the Santa Susana Field Laboratory Area IV Hazardous Waste Management Facility.

DTSC. 1995a. Hazardous Waste Facility Post‐Closure Permit, The Boeing Company, Rocketdyne Propulsion and Power, Santa Susana Field Laboratory, Areas I and III, Simi Hills, Ventura County, California. Permit Number PC‐94/95‐3‐03. May 11.

DTSC. 1995b. Hazardous Waste Facility Post‐Closure Permit, National Aeronautic & Space Adminstration/The Boeing Company, Santa Susana Field Laboratory, Area II, Simi Hills, Ventura County, California. Permit Number PC‐94/95‐3‐02. May 11.

DTSC. 2007. Consent Order for Corrective Action, In the Matter of: Santa Susana Field Laboratory, Simi Hills, Ventura County, California, The Boeing Company, National Aeronautics and Space Administration, and The U.S. Department of Energy (Respondents). Docket No. P3‐07/08‐003. August 16.

DTSC. 2011a. Department of Toxic Substances Control Comments on the Sitewide Groundwater Remedial Investigation Report for Santa Susana Field Laboratory, Ventura County, California. December 21.

DTSC. 2011b. Final Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air. Available online at: http://www.dtsc.ca.gov/AssessingRisk/upload/Final_VIG_Oct_2011.pdf. October. Accessed on: October 2011.

California Regional Water Quality Control Board, Central Valley Region. 2008. A Compilation of Water Quality Goals, prepared by Jon D. Marshack, D.Env. July.

CDM Federal Programs Corporation (CDM). 2011. Master Work Plan/Field Sampling and Analysis Plan, Co‐Located Chemical Sampling at Area IV, Santa Susana Field Laboratory, Ventura County, California. February.

CDM. 2012. Work Plan for Chemical Data Gap Investigation Phase 3 Soil Chemical Sampling at Area IV, Santa Susana Field Laboratory, Ventura County, California. April.

CH2M HILL. 2013a. Master RFI Data Gap Work Plan, Santa Susana Field Laboratory, Ventura County, California. March.

CH2M HILL. 2013b. Integration of the Surficial Media Operable Unit Risk Assessment Methodology with the Data Quality Objectives Process, Boeing RCRA Facility Investigation, SSFL. March.

CH2M HILL. 2013c. Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, SSFL. March.

CH2M HILL. 2013d. Recommended Approach for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, SSFL. March.

CH2M HILL. 2012a. Sitewide Inventory of Tanks, Santa Susana Field Laboratory, Ventura County, California. April 6.

CH2M HILL. 2012b. Sitewide Summary of the Water Conveyance System at the Santa Susana Field Laboratory, Ventura County, California. April 6.

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CH2M HILL and MWH. 2008. Standard Operating Procedure, Onsite Debris Survey and Sampling Methodology, Santa Susana Field Laboratory, Ventura County, California. Prepared for The Boeing Company, United States Department of Energy, National Aeronautics and Space Administration. November.

ICF Kaiser Engineers (ICF), 1993a. Current Conditions Report and Draft RCRA Facility Investigation Work Plan, Areas I and III, Santa Susana Field Laboratory, Ventura County, California. October.

ICF, 1993b. Current Conditions Report and Draft RCRA Facility Investigation Work Plan, Area II and Area I LOX Plant, Santa Susana Field Laboratory, Ventura County, California. October.

ICF, 1993c. Current Conditions Report and Draft RCRA Facility Investigation Work Plan, Area IV, Santa Susana Field Laboratory, Ventura County, California. October.

MECx. 2012. Quality Assurance Project Plan, Santa Susana Field Laboratory RCRA Facility Investigation Surficial Media Operable Unit. Revision 5. November.

MWH. 2004. RFI Program Report, Surficial Media Operable Unit, Santa Susana Field Laboratory, Ventura County, California. July.

MWH. 2005. Standardized Risk Assessment Methodology Work Plan, Revision 2, Santa Susana Field Laboratory, Ventura County, California. September.

MWH. 2009a. Draft Site‐Wide Groundwater Remedial Investigation Report, Santa Susana Field Laboratory, Ventura County, California. December.

MWH. 2009b. Treatability Study Work Plans, Santa Susana Field Laboratory, Ventura County, California. June.

MWH. 2009c. Site Conceptual Model for the Migration and Fate of Contaminants in Groundwater at Santa Susana Field Laboratory, Simi, California.

MWH. 2010. Draft Groundwater Remedial Investigation Data Gap Sampling and Analysis Plan, Santa Susana Field Laboratory, Ventura County, California. March.

MWH. 2012a. Sanitary Sewer System Feature Class, Santa Susana Field Laboratory, Ventura County, California. April 6.

MWH. 2012b. Natural Gas Pipeline Feature Class, Santa Susana Field Laboratory, Ventura County, California. April 6.

MWH. 2013. Recommended Approach for Evaluating Vadose Zone Mass Flux of Contaminants to Groundwater, Boeing RCRA Facility Investigation, SSFL. March.

MWH. Pending. Standardized Risk Assessment Methodology Work Plan, Revision 2 Addendum, Santa Susana Field Laboratory, Ventura County, California.

MWH and CH2M HILL. 2009. Standard Operating Procedures: Building Feature Evaluation and Sampling, Revision 1, Santa Susana Field Laboratory, California. June.

MWH and CH2M HILL. 2011. Inhalation Toxicity Reference Value Updates for Use in Ecological Risk Assessments at the Santa Susana Field Laboratory, Ventura County, California ‐ Technical Memorandum. June 21.

NASA. 2011. Draft Remedial Investigation Work Plan for NASA Sites at the Santa Susana Field Laboratory, Ventura County, California. March.

Ogden Environmental and Energy Services Co., Inc. (Ogden). 1996. RCRA Facility Investigation Work Plan Addendum. Santa Susana Field Laboratory, Ventura County, California. September.

Science Applications International Corporation (SAIC). 1991. Final RCRA Facility Assessment Report for Rockwell International Corporation, Rocketdyne Division, Santa Susana Field Laboratory, Ventura County, California. Prepared for USEPA Region IX. July.

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The Boeing Company (Boeing). 2010. The Boeing Company – Santa Susana Field Laboratory, Standard Operating Procedures: Building Demolition Debris Characterization and Management. Final. February 24.

United States Environmental Protection Agency (USEPA). 2006. Guidance on Systematic Planning Using the Data Quality Objectives Process. (EPA QA/G‐4, EPA/240/B‐06/001) February.

Tables

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TABLE 1 Assessment Methods and Activities to Identify a Chemical Release or Potential Release Comprehensive Data Quality Objectives, Santa Susana Field Laboratory, Ventura County, California

Method 1: Document and Record Review ‐ Review of all available historical RFI‐related reports and documents that might contain information relevant to the RFI.

RCRA Facility Assessment (1989 to 1994): Historical and current operational chemical use information was reviewed, a site inspection was performed, and previous sampling data were evaluated to determine the likelihood of a potential release to environmental media. One hundred twenty‐five areas of the SSFL that used, stored, or handled hazardous waste were identified for designation as SWMU or Areas of Concern by the USEPA under the SSFL RFA.

RFI Program Report (2004): Subsequent to the RFA, 10 additional Areas of Concern were identified during preparation of the RFI program report, for a total of 135 SWMUs and Areas of Concern. These 135 SWMUs and Areas of Concern were grouped into 51 RFI sites. Boeing, DOE, NASA, and DTSC subdivided the SSFL into 11 RFI groups for the purposes of RFI reporting work activities; each group contains 0 to 17 RFI sites. All information relevant to the SSFL RFI available at that time was summarized and presented in the RFI program report.

Boeing RFI Reports (2008 to 2009): The Boeing RFI reports considered all historical reporting and documentation available at the time of report preparation. CUAs were identified in the Boeing RFI reports; these reports serve as the baseline compilation of CUAs that are evaluated and expanded upon during implementation of the DQO evaluation process. DTSC and stakeholder comments on the 2008/2009 Boeing RFI reports are considered under the context of the comprehensive DQO process, and any new release or potential release identified as a result of the DTSC comments will be identified and included in the DQO media‐specific Tables 3 through 10. Other RFI‐relevant information derived from DTSC comments on the RFI reports are included within the applicable DQO Figure 2 activities identified below.

Sitewide Groundwater RI Report (2009): The Sitewide Groundwater Remedial Investigation Report presents an assessment of the nature and extent of SSFL site‐related chemicals in groundwater and the vadose zone bedrock. Additional investigation of the CFOU is ongoing, and information obtained is to be evaluated to supplement the existing data set and site conceptual model understanding for the SMOU RFI DQO evaluation.

Review of Historical Documentation: Review of all available historical RFI‐related reports and documents that might contain information relevant to the RFI was performed, including but not limited to reports, maps, inventories, spill records, notes, and correspondence, to identify areas of chemical use not already identified during the RFA or RFI. The process for reviewing historical documents is presented in Figure 9. This process was consistently followed by the Boeing technical consultants to ensure that relevant information from the historic records review was captured and incorporated into the RFI reporting process to meet the RFI DQOs. More than 150,000 historic documents were reviewed for identification of information potentially relevant to the RFI; these findings were included in the 2008/2009 Boeing RFI reports. Subsequently, additional historical documents became available and were reviewed or are currently under review using the same process for identification of potentially RFI‐relevant information. A reference list of all historical documents reviewed will be provided to DTSC, along with an electronic copy of the documents on the DTSC hard drive deliverable.

Method 2: SSFL Sitewide Inventories: Compilation and evaluation of sitewide inventories of infrastructure or features with potential chemical storage, distribution, use, or disposal history. The documentation for the inventories performed to date was provided to DTSC with the central key document repository deliverable in May 2012.

Building Inventory and Feature Survey: The building feature inventory and survey was performed in 2008 to systematically document the location and condition of all existing building features that potentially could have been a source of a chemical release to environmental media. All tasks identified in the Standard Operating Procedures: Building Feature Evaluation and Sampling, Revision 1, Santa Susana Field Laboratory, California (building feature SOP; MWH and CH2M HILL, 2009) have been performed and the relevant information was documented in the Boeing SSFL RFI building feature documentation logs.

Tank Inventory: An SSFL sitewide tank inventory was compiled by Boeing, DOE and NASA (CH2M HILL, 2012a). This inventory identifies all known information regarding the location, size, composition, contents, use period, and regulatory status of all underground storage tanks, aboveground storage tanks, and undetermined tanks.

Sewer System Survey: A comprehensive summary of the SSFL sanitary sewer system (MWH, 2012a) was prepared and submitted to DTSC. This summary included information on the SSFL sewage treatment plants, sewer system pipelines, manholes, leachfields, septic tanks, and other key sewer system features. A SSFL sitewide sewer system survey was performed in 2008 and 2009 to visually inspect sewer manholes and pipeline inlets and outlets and to identify manholes that are in poor condition and may have resulted in impacts to environmental media. Boeing inspected the interior of each sanitary sewer system manhole and catch basin located in the Boeing RFI subareas. Soil samples were collected when soil was observed or available for collection inside the manholes or catch basins at the time of the inspection. The inspection also recorded the condition of the manholes and catch basins, including any fractures or deterioration of the concrete structure or the inlet and outlet pipelines. In addition, analytical data for samples collected within 100 feet of the sewer system were reviewed to evaluate if there is evidence of a release or potential release from the sewer system.

Reclaimed Water System Inventory: A comprehensive sitewide evaluation was performed to identify and document the locations and operational history of all features associated with the reclaimed water system. A summary of the SSFL water conveyance system (CH2M HILL, 2012b) was compiled and submitted to DTSC. This summary included information on the SSFL reclaimed water system, including groundwater reclamation system effluent, recycled/recirculated water, leach fields, sewage treatment plant effluent, and reclaimed storage.

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Pipelines Wrapped with Mastic Tape Documentation: A comprehensive sitewide evaluation was performed to identify and document the locations of natural gas pipelines wrapped with mastic tape (that potentially contains polychlorinated biphenyls). A summary of the natural gas piping distribution system was prepared and submitted to DTSC (MWH, 2012b). In addition, other pipelines wrapped with mastic tape have been identified at SSFL.

Primary Fuel‐oil and Chemical Pipeline Inventory: Information on the locations and contents of primary fuel oil and chemical pipelines within the Boeing RFI subareas and Boeing RFI sites is being compiled and will be documented in forthcoming addenda to the Boeing Master RFI Data Gap Work Plan.

GIS Gold Copy Data Management Tool: A comprehensive GIS and analytical database was compiled for the SSFL that contains current and complete Boeing, NASA, DOE chemical and radiological data for all media combined into single database and sitewide features composited in GIS using common symbology. All RFI‐relevant information is now contained in a single GIS system and is linked to analytical databases and key document files. The comprehensive GIS and analytical database was uploaded to DTSC hard drive and provides for viewing of coverage layers unique to various site features and types of information in addition to providing electronic search and screening functions for review of the existing data sets. The comprehensive GIS and analytical database will be updated periodically, as appropriate, and will be provided to DTSC for access to the most recent and complete set of SSFL RFI‐relevant information.

Method 3: SSFL Sitewide Comprehensive Inspections and Documentation

Debris Survey and Sampling: A sitewide debris survey was performed in 2008/2009 to systematically identify surficial evidence of solid waste disposal through visual inspections of the SSFL. Types of solid wastes that were targeted as part of this survey included but were not limited to soil piles, building demolition debris, containers, metal debris, pipe segments, skeet target (clay pigeon) fragments, and miscellaneous other non‐household‐type debris. The debris survey was conducted on 50‐foot transects across all of the SSFL. The 50‐foot transects were walked by two people in tandem to photograph and global positioning system map debris locations in accordance with the Standard Operating Procedure, Onsite Debris Survey and Sampling Methodology, Santa Susana Field Laboratory, Ventura County, California (CH2M HILL and MWH, 2008). Qualifying debris areas were sampled and analyzed in accordance with the 2008 SOP.

Biological Survey and Mapping: A sitewide survey of biological and ecological site conditions was performed in 2008 and 2009; the results were mapped and included in the Boeing RFI reports.

Aerial Photograph Review: Review of historical aerial photographs was performed, commencing in 1997 (USEPA) and continuing through 2011 (Boeing, DOE, and NASA). Historical aerial photographs were integrated into GIS by orthorectifying the photographs and modifying existing feature classes in GIS with attributes to allow association of information in GIS with identified aerial photographs. Features identified in the aerial photograph review are documented in GIS to show that information provided in the photographs has been adequately captured in the RFI documentation. Aerial photographs are used to provide a basis for site histories and site configurations, identify chemical use areas, and locate site features for characterization sampling. Boeing, DOE, and NASA reviewed historic aerial photographs representing 17 photo coverage years that span the lifecycle of SSFL facility operations, from 1953 to 2005. The historical aerial photograph review findings are documented in accordance with the SSFL sitewide format, consistent with the 2010 air photo documentation SOP. Observed features documented in the GIS include buildings, debris, asphalt swales, channels, streams, excavation areas, pipes, sumps, ponds, roads, storage yards, cleared vegetation, tanks, soil disturbance areas, and other features that could be of interest to the RFI.

Method 4: RFI Site‐specific Inspections and Documentation

Topography and Physical Accessibility: The SSFL topography is evaluated to identify areas where physical accessibility for historical chemical use, storage, handling, or disposal activities would have been prohibitively difficult or reasonably possible.

Proximity to Roadways and Operations: The locations of historical roadways relative to the locations of historical operations are evaluated to identify areas where historical chemical use, storage, handling, or disposal activities could have been reasonably possible along roadways.

Geophysical Survey: In some cases, geophysical surveys have been performed during the Boeing demolition process and for investigation of suspect underground features. All geophysical survey information will be evaluated for RFI‐relevant information.

Demolition Documentation and Sampling: Oversight was conducted during demolition of existing buildings and structures to identify locations of potential impacts to environmental media beneath the buildings and structures (through observation, field monitoring, and sample collection and chemical analysis). The Boeing demolition documentation is submitted to DTSC on an RFI site‐by‐site basis as it is performed and in accordance with the The Boeing Company – Santa Susana Field Laboratory, Standard Operating Procedures: Building Demolition Debris Characterization and Management (building demolition SOP) (Boeing, 2010).

Interim Removal Actions: Oversight was conducted, including sample collection and chemical analysis, during ongoing SSFL interim removal actions. All documentation associated with the interim actions is contained in the final documentation reports submitted to DTSC for each interim removal action.

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Method 5: Chemical Migration Assessment: Evaluation of potential chemical migration from any impacted area at SSFL to the CNFA areas thought to be un‐impacted.

Vapor Intrusion Pathway Evaluation: The vapor intrusion pathway will be evaluated in accordance with Appendix A of the comprehensive DQO report: Recommended Approach for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California (CH2M HILL, 2013d). Additional soil vapor data will be collected where required to complete characterization of the nature and extent and fate and transport of impacts from source areas and to support remedial planning. The areas at Boeing SSFL where the vapor intrusion pathway might be complete will be spatially delineated by considering the known or suspected vapor sources, the nature and extent of impacts, and the fate and transport of VOC constituents.

Air Dispersion Modeling: Air dispersion modeling will be performed in accordance with the protocols identified in Appendix B of the DQO report: Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California (CH2M HILL, 2013c). Based on the air dispersion modeling results, soil sample collection locations will be identified along transects defined by model results. Samples will be collected and analyzed to evaluate the air dispersion pathway for potential migration of chemicals from the identified sources.

Vadose Zone Mass Flux of Contaminants to Groundwater Modeling: The vadose zone mass flux of contaminants to groundwater approach includes evaluating the need for additional field data (that is, drilling of deep borings); evaluating the need to model vadose zone mass flux of contaminants to groundwater; modeling; and determining if the vadose zone should be recommended for the CMS or CNFA. Vadose zone mass flux of contaminants to groundwater modeling will be performed in accordance with Appendix D of the DQO report: Recommended Approach for Evaluating Vadose Zone Mass Flux of Contaminants to Groundwater, Santa Susana Field Laboratory, Ventura County, California (MWH, 2013).

Surface Water Drainage Documentation: A comprehensive and systematic sitewide evaluation was performed to identify and document the locations of all surface water drainage features and the direction of surface water flow at RFI sites. The results of this comprehensive evaluation were included in the GIS gold copy data management tool.

NPDES Surface Water Data: Surface water runoff at the SSFL is regularly monitored as part of the NPDES monitoring program under the oversight of the Water Board. Historical and ongoing surface water data collected under the NPDES program are evaluated for RFI‐relevant information.

Seeps and Springs Data: Ongoing seeps and springs investigation and evaluation is being conducted under the CFOU RI program.

Analytical Data Collected for Purposes Other than the RFI: All analytical data, field notes, and field logs from all prior field investigations and interim measures were reviewed to identify any chemical constituents that have been detected above the required characterization levels and to identify any observations made during field activities that suggest a chemical release may have occurred.

Notes:

GIS = geographic information system NPDES = National Pollutant Discharge Elimination System RFA = RCRA facility assessment SOP = standard operating procedure SWMU = solid waste management unit

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TABLE 2 Potential CUA Field Sampling Methodologies for CUA or Conditional NFA Determination for the SMOU Comprehensive Data Quality Objectives, Santa Susana Field Laboratory, Ventura County, California

Feature Typea Sampling Strategy for CUA or CNFA Determinationb Analysis Strategyc Sampling Density/Depths d, e, f, g, h

Structures with no known chemical use based on documentation (that is, documentation shows that the structure did not have any chemical uses), including buildings, concrete pads, awnings, canopies, trailers, and storage bins

1. Sampling is not required if documentation indicates that the structure did not use chemicals (for example, office building, guard shack, and lunch room).

1. No sampling will be performed in these areas.

1. No sampling will be performed in these areas.

Structures with no documented chemical usage information (that is, it is not known what the structure was used for, or it is known what the structure was used for but information is insufficient to conclude that no chemical use occurred), including, but not limited to, buildings, concrete pads, awnings, canopies, trailers, cooling towers, spillways, and storage bins

1. For existing buildings, collect samples at locations of building features that likely or potentially resulted in contaminant release to environmental media in accordance with the building feature SOP (MWH and CH2M HILL, 2009). Samples collected during building demolition will follow the building demolition SOP (Boeing, 2010).

2. For existing and former structures, perform targeted soil and soil vapor sampling at suspect release locations (for example, locations of building features that may have resulted in releases to the environment or locations where stained or disturbed soil are observed).

3. Collect soil samples from drainage pathways downstream of the structure.

4. If no sample locations are identified during Steps 1 and 2 above, perform soil and soil vapor sampling on a biased grid, targeting topographic low points and cracks in concrete (where applicable).

5. For existing buildings that are not planned for future demolition, subslab samples will be collected during two sampling events in accordance with Final Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air (DTSC, 2011b). During each event, a minimum of two subslab soil vapor samples will be collected beneath the building to support evaluation of the vapor intrusion pathway in the human health risk assessment (if performed).

1. Analyze soil samples for the limited target analyte list: VOCs, SVOCs, metals, and TPH. Add any adjacent CUA‐specific or RFI site‐specific analytical methods to the list, as appropriate. At cooling towers, also analyze for NDMA, formaldehyde, and hexavalent chromium. Analyze soil vapor samples for VOCs.

1. Lateral: If no sample locations were identified during the building feature survey or during review of historical photographs, perform soil and soil vapor sampling on a biased grid. Samples will generally be collected on 50‐foot to 100‐foot grids; however, the size and spacing of the grid will be determined on a structure‐specific basis and based on professional judgment (based on the size, age, and condition of the structure).

Collect soil samples from a minimum of two locations from drainage pathways immediately downstream of the structure.

2. Vertical: Collect soil samples at 0.5 foot bgs (for chemicals with low mobility in the environment, with limited susceptibility to chemical degradation, and that were likely released at the surface), 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation), 6 feet bgs, and 10 feet bgs. Analyze samples from 0.5, 1.5, and 6 feet bgs. If the 6‐foot‐bgs sample at a particular location has concentrations that exceed characterization levels, analyze the 10‐foot‐bgs sample at that location. Collect soil vapor samples at 5 feet bgs.

Collect soil samples from 0.5 foot bgs (for chemicals with low mobility in the environment and with limited susceptibility to chemical degradation) and 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation) and from the base of alluvium within downstream drainage pathways.

Structures with known chemical uses, including, but not limited to, buildings, concrete pads, awnings, canopies, trailers, cooling towers, spillways, and storage bins

1. For existing buildings, collect samples at locations of building features that likely or potentially resulted in contaminant release to environmental media in accordance with the building feature SOP (MWH and CH2M HILL, 2009). Samples collected during building demolition will follow the building demolition SOP (Boeing, 2010).

2. For existing and former structures, perform targeted soil sampling at suspect release locations (for example, locations of building features that may have resulted in releases to the environment or locations where stained or disturbed soil are observed). If known chemical uses include VOCs, also collect soil vapor samples from these areas.

3. For existing and former structures, collect soil samples from areas where historical documentation indicates that chemicals were used, stored, handled, or disposed of. If known chemical uses include VOCs, also collect soil vapor samples from these areas.

4. Collect soil samples from drainage pathways downstream of the structure.

5. If no sample locations are identified during Steps 1 through 3 above, perform soil sampling on a biased grid, targeting topographic low points and cracks in concrete (where applicable). If known chemical uses include VOCs, also collect soil vapor samples on a biased grid.

6. For existing buildings that are not planned for future demolition, subslab samples will be collected during two sampling events in accordance with Final Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air (DTSC, 2011b). During each event, a minimum of two subslab soil vapor samples will be collected beneath the building to support evaluation of the vapor intrusion pathway in the human health risk assessment (if performed).

1. Analyze soil samples for analytical methods corresponding to chemicals used, stored, handled, or potentially released in or around the structure. If other chemical uses cannot be excluded based on available documentation, also analyze soil samples for VOCs, SVOCs, metals, TPH, and other chemicals used at adjacent CUAs or RFI sites. At cooling towers, also analyze for NDMA, formaldehyde, and hexavalent chromium. If soil vapor samples are collected, analyze for VOCs.

1. Lateral: If no sample locations were identified during the building feature survey or during review of historical photographs or other historical documentation, perform soil and soil vapor sampling on a biased grid. Samples will typically be collected on 50‐foot to 100‐foot grids; however, the size and spacing of the biased grid, if performed, will be determined on a structure‐specific basis and based on professional judgment (based on the size, age, and condition of the structure).

Collect soil samples from a minimum of two locations from drainage pathways immediately downstream of the structure.


Collect soil samples from 0.5 (for chemicals with low mobility in the environment and with limited susceptibility to chemical degradation) and 1.5 (for chemicals that are volatile, mobile, and subject to degradation) feet bgs and from the base of alluvium within downstream drainage pathways.

Storage Yards and Unpaved Parking Areas 1. Collect soil and soil vapor samples from a minimum of two locations in most former storage yards and unpaved parking areas, targeting topographic low points and suspect release locations. Using professional judgment, one soil and soil vapor sample location may be deemed sufficient for very small storage yards or unpaved parking areas.

2. Collect soil samples from drainage pathways downstream of the storage yard or unpaved parking area.

1. Analyze soil samples for analytical methods corresponding to chemicals used, stored, handled, or potentially released in the storage yard. If other chemical uses cannot be excluded based on available documentation, also

1. Lateral: Collect soil and soil vapor samples from one to three locations within each storage yard or unpaved parking area.

Collect soil samples from a minimum of two locations from drainage pathways immediately downstream of the storage yard or unpaved parking area.

2. Vertical: Collect soil samples at 0.5 foot bgs (for chemicals with low mobility in the environment, with limited

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analyze soil samples for VOCs, SVOCs, metals, TPH, and other chemicals used at adjacent CUAs or RFI sites. If chemical uses are unknown, then analyze samples for the limited target analyte list: VOCs, SVOCs, metals, and TPH. Analyze soil vapor samples for VOCs.

susceptibility to chemical degradation, and that were likely released at the surface), 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation), 6 feet bgs, and 10 feet bgs. Analyze samples from 0.5, 1.5, and 6 feet bgs. If the 6‐foot‐bgs sample at a particular location has concentrations that exceed characterization levels, then also analyze the 10‐foot‐bgs sample at that location. Collect soil vapor samples at 5 feet bgs.


Pole‐mounted Transformers 1. Collect soil samples beneath pole‐mounted transformers installed prior to 1980.

2. Also collect soil samples from drainage pathways downstream of the transformer pole.

1. Analyze samples for PCBs. 1. Lateral: Collect soil samples from three to four locations within 2 feet beyond the “drip line” of the transformer (or based on professional judgment if the pole is no longer present). Composite discrete samples into one sample. Composite samples will be analyzed. Discrete samples will be held by laboratory. Analysis of discrete samples will be performed if PCBs are detected in composite sample.

Collect soil samples from a minimum of two locations from drainage pathways immediately downstream of the transformer pole.

2. Vertical: Collect samples at approximately 0.5 foot bgs.

Substations and Pad‐mounted Transformers

1. Collect soil samples at substations and pad‐mounted transformers installed prior to1980.

2. Also collect soil samples from drainage pathways downstream of the substation or pad‐mounted transformer.

1. Analyze samples for PCBs. 1. Lateral: Collect discrete soil samples from three to four locations (~5 feet around substation location). Composite discrete samples into one sample. Composite samples will be analyzed. Discrete samples will be held by laboratory. Analysis of discrete samples will be performed if PCBs are detected above laboratory reporting limits in the composite sample.

Collect soil samples from a minimum of two locations from drainage pathways immediately downstream of the substation.

2. Vertical: Collect samples at approximately 0.5 foot bgs.

Tank Areas, including USTs, ASTs, and undetermined tanks, and tanks for which contents are “water” and available documentation does not specify that the tank only contained potable water; excluding tanks containing compressed gases, liquid nitrogen, liquid hydrogen, nitrogen tetroxide, and hydrogen peroxide

1. If the tank location is known, perform the following:

a. Inspect tank and vicinity for visible impacts/soil staining. Collect soil samples from locations of visible impacts.

b. For USTs, collect soil samples beneath the tank. Also, collect soil samples beneath the inlet and outlet piping extending to/from the UST, if known.

c. For ASTs and undetermined tanks, collect soil samples beneath the tank, from low areas within the tank pad, and beneath valve connection points. Also, collect soil samples from drainage pathways downstream of the tanks.

d. If tank may have contained VOCs or may have been cleaned using solvents (for example, LOX tanks), collect soil vapor samples beneath or adjacent to each tank or group of tanks. For the LOX tanks, target the tanks themselves and associated LOX piping distribution centers.

2. If the tank location is unknown, perform the following:

a. For undetermined tanks, evaluate the type and contents of the tank, uses of the tank, and findings from any building demolition activities performed in the area. Based on this evaluation, if the undetermined tank is suspected of being a UST, proceed to Step B; otherwise, proceed to Step C.

b. Perform a geophysical survey to locate subsurface tanks (that is, USTs and undetermined tanks). If the tanks or potential fill areas (potential locations of former USTs that have been backfilled following UST removal) are located during the geophysical survey, collect samples as described above.

c. If the tank cannot be located during the geophysical survey or if the tank is believed to be an AST, perform soil sampling in the area suspected to have contained tanks on a biased grid, targeting topographic low points and drainage pathways. If tank may have contained VOCs, also collect soil vapor samples on a biased grid.

1. Analyze soil samples for the tank contents (if known) or for the limited target analyte list: VOCs, SVOCs, metals, and TPH and any adjacent CUA‐specific or RFI site‐specific analytical methods, as appropriate (if tank contents are unknown and for water tanks). If soil vapor samples are collected, analyze for VOCs.

1. Lateral: For groups of tanks located next to one another, samples may represent multiple tanks.

If tank location(s) cannot be confirmed, perform soil (and soil vapor, if tank may have contained VOCs) sampling on a biased grid. Samples will typically be collected on 50‐foot to 100‐foot grids; however, the size and spacing of the biased grid, if performed, will be determined on a tank‐area‐specific basis using professional judgment. The grid size will be on the lower end of this range for small tank areas and for less mobile constituents (for example, PCBs and heavy carbon‐range hydrocarbons) and on the higher end of this range for large tank areas and more mobile constituents (for example, VOCs).

Collect soil samples from a minimum of two locations from drainage pathways immediately downstream of ASTs and undetermined tanks.

2. Vertical: For ASTs and undetermined tanks, collect soil samples at 0.5 foot bgs (for chemicals with low mobility in the environment, with limited susceptibility to chemical degradation, and that were likely released at the surface), 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation), 6 feet bgs, and 10 feet bgs. For undetermined tanks, also collect a sample from 15 feet bgs unless it can be demonstrated that the undetermined tank is not likely a UST.

For ASTs, analyze samples from 0.5, 1.5, and 6 feet bgs. If the 6‐foot‐bgs sample at a particular location has concentrations that exceed characterization levels, then also analyze the 10‐foot‐bgs sample at that location. For undetermined tanks, analyze samples collected from 0.5, 1.5, 6, and 10 feet bgs. If the 10‐foot‐bgs sample at a particular location has concentrations that exceed characterization levels, analyze the 15‐foot‐bgs sample at that location.

Collect soil vapor samples at 5 feet bgs.

Collect soil samples from 0.5 foot bgs (for chemicals with low mobility in the environment and with limited susceptibility to chemical degradation) and 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation) and from the base of alluvium within drainage pathways downstream of ASTs and undetermined tanks.

For subsurface tanks, collect soil samples from 1 and 6 feet bgs beneath the tank bottom. Collect soil vapor samples immediately below the bottom of the tank (unless tank bottom is shallower than 5 feet bgs, in which case collect soil vapor samples at 5 feet bgs).

Pipelines, excluding fresh/domestic water pipelines, compressed gas pipelines, and

1. If the locations of pipelines are known, perform the following:

a. Inspect pipelines and vicinity for visible impacts/soil staining and conditions of the

1. Analyze soil samples for pipeline contents (if known) or for the limited

1. Lateral: If the locations of the pipeline are known, collect samples from an average of 50, 100, or 200 feet along pipeline (depending on the type of pipeline [aboveground or belowground], the age and condition of the

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LOX pipelinesi pipeline (for example, rusting, cracks, etc.).

b. Collect soil samples beneath the pipeline. Focus soil sampling beneath pipeline joints and bends, beneath locations where the pipeline has been repaired, and beneath low points in the pipeline (to the extent that these locations can be identified). If the pipeline may have contained VOCs, also collect soil vapor samples beneath pipeline.

c. Collect soil samples from drainage pathways downstream of aboveground pipelines.

2. If the locations of the pipeline are unknown, perform the following:

a. If it is unknown if the pipeline is aboveground or belowground, evaluate the type and contents of the pipeline, uses of the pipeline, and findings from any building demolition activities performed in the area. Based on this evaluation, if the pipeline is suspected of being a subsurface pipeline, proceed to Step b; otherwise, proceed to Step C.

b. Perform a geophysical survey to locate subsurface pipelines (review past geophysical survey results if a geophysical survey has been performed in the area previously). If the pipeline is located during the geophysical survey, collect samples as described above.

c. If the pipeline cannot be located during the geophysical survey or if the pipeline is believed to be an aboveground pipeline, perform soil sampling on a biased grid, targeting topographic low points and drainage pathways. If pipeline may have contained VOCs, also collect soil vapor samples on a biased grid.

target analyte list: VOCs, SVOCs, metals, and TPH and any adjacent CUA‐specific or RFI site‐specific analytical methods, as appropriate (if unknown). Analyze soil vapor samples for VOCs.

pipeline, mobility of the pipeline contents, and the number of locations where soil staining, pipeline rusting, cracks, joints, bends, or low points occur or are observed). Locations of soil staining, rusting, cracks, joints, bends, low points, and areas of repair along the pipeline will be targeted for sampling.

If the locations of the pipeline are unknown, collect soil (and soil vapor, if the pipeline may have contained VOCs) on a biased grid. The size and spacing of the biased grid, if performed, will be determined on a pipeline‐specific basis. Samples will typically be collected on 50‐foot to 100‐foot grids. The grid size will be on the lower end of this range for short pipelines and for less mobile constituents (for example, PCBs and heavy carbon‐range hydrocarbons) and on the higher end of this range for long pipelines and more mobile constituents (for example, VOCs).

Collect soil samples from a minimum of two locations from drainage pathways immediately downstream of any aboveground pipeline locations where a potential for chemical release occurred based on professional judgment (for example, area of visible soil staining or a pipeline repair location).

2. Vertical: For aboveground pipelines, collect soil samples at 0.5 foot bgs (for chemicals with low mobility in the environment, with limited susceptibility to chemical degradation, and that were likely released at the surface) and 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation). Collect soil vapor samples at 5 feet bgs.


For subsurface pipelines, collect soil samples at 1 foot beneath the bottom of the pipeline at a location immediately adjacent to the pipeline. Collect soil vapor samples immediately adjacent to the pipeline from a depth corresponding to the bottom of the pipeline (unless pipeline is shallower than 5 feet bgs, in which case, collect soil vapor samples at 5 feet bgs).

Pipelines Wrapped in Mastic Tape 1. Following building demolition activities where such pipelines are observed, collect soil samples immediately below pipelines wrapped in mastic tape.j

1. Analyze soil samples for asbestos, PCBs, TPH, and SVOCs.

1. Lateral: Collect soil samples approximately every 50 feet along pipelines wrapped in mastic tape.

2. Vertical: Collect soil samples immediately beneath pipelines wrapped in mastic tape.

Spray Field Areas 1. Perform soil sampling on a biased grid, targeting topographic low points and drainage pathways. If chemicals used include VOCs, also collect soil vapor samples on a biased grid.

1. Analyze samples for analytical methods corresponding to chemicals used in the area and chemicals potentially present in reclaimed water (see the complete analytical list for “Reclaimed Water System” below). Add any adjacent CUA‐specific and RFI site‐specific analytical methods to the list, as appropriate. Analyze soil vapor samples for VOCs, if applicable.

1. Lateral: The size and spacing of the biased grid will be determined on a site‐specific basis. Samples will typically be collected on 50‐foot to 100‐foot grids. The grid size will be on the lower end of this range for small spray field areas and on the higher end of this range for large spray field areas.

Collect soil samples from a minimum of two locations from drainage pathways immediately downstream of spray field areas where there is a potential for a chemical release to have occurred based on professional judgment.

2. Vertical: Collect soil samples at 0.5 foot bgs (for chemicals with low mobility in the environment, with limited susceptibility to chemical degradation, and that were likely released at the surface), 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation), 6 feet bgs, and 10 feet bgs. Analyze samples from 0.5, 1.5, and 6 feet bgs. If the 6‐foot‐bgs sample at a particular location has concentrations that exceed characterization levels, then also analyze the 10‐foot‐bgs sample at that location. Collect soil vapor samples at 5 feet bgs.

Collect soil samples from 0.5 foot bgs (for chemicals with low mobility in the environment and with limited susceptibility to chemical degradation) and 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation) and from the base of alluvium within drainage pathways downstream of spray field areas.

Reclaimed Water System 1. Collect samples from spray fields, tanks, surface water bodies, pipelines, and surface water drainage pathways associated with the reclaimed water system in accordance with feature‐specific sampling strategies listed in this attachment.

2. The reclaimed water system is being further evaluated sitewide. Following this evaluation, a plan for performing further investigation of the reclaimed water system (beyond the investigation prescribed in Step 1 above) will be presented to DTSC for approval.

1. Analyze soil samples for VOCs, TPH, SVOCs (including PAHs and NDMA), metals, pH, PCBs, energetics, formaldehyde, perchlorate, dioxins, inorganics, hexavalent chromium, pesticides, herbicides, and cyanide. Analyze soil vapor samples for VOCs.

1. Collect samples from spray fields, tanks, surface water bodies, pipelines, and surface water drainage pathways associated with the reclaimed water system in accordance with feature‐specific sampling strategies listed in this report.

Sanitary Sewer System 1. The sewer system is investigated as follows (this sampling strategy generally summarizes how the sewer system has been investigated to date; the need for further investigation of the sewer system is currently being evaluated):

a. Inspect sewer manholes and pipelines visible from the manholes for indications of

1. For samples collected at or near buildings, analyze soil samples for analytical methods corresponding to chemicals used, stored, handled, or potentially released in the building. For

1. Vertical: Collect soil samples at 0.5 foot bgs (for chemicals with low mobility in the environment and with limited susceptibility to chemical degradation), 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation), and 6 feet below the bottom depth of the sewer system pipeline, manhole, or other sewer system structure.

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deterioration, cracks, breaks, etc. Collect soil and soil vapor samples from locations where the manholes and/or pipelines are observed to be deteriorated, cracked, or broken.

b. Inspect the sewer pipeline and other sewer structures during building demolition activities. Collect soil and soil vapor samples from locations where the pipeline or other sewer structures are observed to be deteriorated, cracked, broken, etc., if applicable.

c. Collect soil and soil vapor samples from locations of junctions in the sewer pipeline, at major force main structures, and at locations where the pipeline has been repaired.

d. Collect samples from locations where the sewer pipeline exits buildings.

e. Collect samples from leach fields and septic tanks as described below.

other samples not associated with specific buildings, analyze soil samples for VOCs, TPH, SVOCs (including PAHs and NDMA), metals, pH, PCBs, energetics, formaldehyde, perchlorate, dioxins, inorganics, hexavalent chromium. Analyze soil vapor samples for VOCs.

Leach Fields and Septic Tanks 1. If the locations of leach fields are known, perform the following:

a. Inspect area for visible impacts/soil staining through trenching. If no visible impacts are observed during trenching, identify influent and downslope ends of leach field and collect soil and soil vapor samples.

b. In addition, if soil beneath or surrounding leach field gravels is visibly impacted, perform targeted soil and soil vapor sampling in this area.

c. Collect soil samples from drainage pathways downstream of the leach field.

2. If the locations of distribution box connections and/or septic tank are known, collect soil and soil vapor samples from these locations.

3. If the locations of the leach field, septic tank, and/or distribution box are unknown, perform the following:

a. Perform a geophysical survey to locate the leach field, septic tank, and distribution box. If the leach field, septic tank, and/or distribution box are located during the geophysical survey, collect samples as described above.

b. If the leach field, septic tank, and/or distribution box cannot be located during the geophysical survey, perform soil and soil vapor sampling on a biased grid, targeting topographic low points and drainage pathways.

1. Analyze soil samples for analytical methods corresponding to chemicals used in the area. Add any adjacent CUA‐specific and RFI site‐specific analytical methods to the list, as appropriate. Analyze soil vapor samples for VOCs.

1. Lateral: Collect soil samples from a minimum of two locations per leach field and per septic tank. Collect samples from a minimum of one location at distribution box connections.

Collect soil samples from one or two locations from drainage pathways immediately downstream of the leach field.

If the locations of the leach field, septic tank, and distribution box cannot be confirmed, collect soil and soil vapor samples on a biased grid. The size and spacing of the biased grid, if performed, will be determined on a site‐specific basis. Samples will typically be collected on 50‐foot grids.

2. Vertical: Collect soil samples at 0.5 foot bgs (for chemicals with low mobility in the environment and with limited susceptibility to chemical degradation), 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation), and 6 feet below the bottom of the leach lines, septic tank, and distribution box connections. Collect soil vapor samples immediately beneath the bottom of the leach lines, septic tank, and distribution box connections (unless the bottom of these features is shallower than 5 feet bgs, in which case collect soil vapor samples at 5 feet bgs).


Debris Areas 1. Clearly delineate debris areas.

2. Collect soil and soil vapor samples from at least one location in each debris area, targeting topographic low points and suspect release locations.

3. Collect soil samples from drainage pathways downstream of debris areas.

1. Analyze soil samples for known chemicals if debris source is known. If debris source is unknown, then analyze soil samples for the limited target analyte list (VOCs, SVOCs, metals, and TPH) and dioxins. Analyze soil vapor samples for VOCs.

1. Lateral: Collect soil and soil vapor samples from one to three locations in each debris area.

Collect soil samples from a minimum of two locations from drainage pathways immediately downstream of the debris areas.

2. Vertical: Collect samples from native soil beneath debris areas at 0.5 foot bgs (for chemicals with low mobility in the environment, with limited susceptibility to chemical degradation, and that were likely released at the surface), 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation), and 6 feet below the native soil ground surface. Also collect a soil sample 10 feet below the native soil ground surface if needed to evaluate potential for increasing concentration gradients. Collect soil vapor samples at 5 feet bgs.


Surface Water Drainage Pathway (downstream of CUAs)

1. Inspect unlined drainage pathways and vicinity for visible impacts/soil staining. Collect soil samples from locations of visibly impacted soil.

2. For lined and unlined drainage pathways, collect soil samples along length of drainage. Focus samples near mouth of drainage, alluvium accumulation areas, and at topographic low points. For lined drainages, also focus on cracks or fractures in lining material.

1. Analyze samples for analytical methods corresponding to chemicals used in upstream areas.

1. Lateral: Collect soil samples at intervals of approximately 200 feet along unlined drainages and approximately 500 feet along lined drainages in areas outside corrective measures study areas. Sample locations along drainage pathways should target alluvium accumulation areas and topographic low points. In addition, collect samples from locations of cracks or repairs in lined drainages.

2. Vertical: Collect soil samples from 0.5 foot bgs (non‐mobile constituents) and 1.5 feet bgs (mobile constituents) and from the base of alluvium (for lined drainages, 1 foot below the bottom of the material that lines drainage).

Perennial Surface Water Body 1. The surface water body will be sounded to establish a water depth configuration and profiled using indicator parameters (for example, temperature, dissolved oxygen, conductivity and pH). To reduce potential disturbance of surface water body stratification, if any, sounding and indicator parameter profiling will be performed at least 48 hours before sampling.

1. Analyze samples for analytical methods corresponding to chemicals used in the area and upstream areas.

1. If vertical profiles of indicator parameters indicate the pond water is vertically stratified, water samples will be collected at three locations: (1) near shore at the water surface; (2) a location with half the maximum water depth, at the water surface and near bottom (below thermocline); and (3) a location with maximum water depth, at the water surface, mid‐depth (above thermocline), and near bottom (below thermocline).

If vertical profiles of indicator parameters at several locations indicate the surface water body does not appear

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2. Collect a minimum of two surface water samples from perennial surface water bodies.

3. Collect a minimum of two sediment samples beneath perennial surface water bodies (including the deepest area of the surface water body and near the surface water body inlet).

4. Collect a sample from the soil underlying the surface water body dike.

vertically stratified, a water sample will be collected from two locations: near the shore at the water surface and mid‐depth near the maximum depth location.

Unless the air is still, near‐shore samples should be collected on the downwind side of the surface water body.

2. Sediment samples will be collected, at a minimum, from the deepest area of the surface water body and at the inlet of the surface water body. At each location, collect discrete sediment samples from 0.5 foot below the bottom of the surface water body and at 1.5‐foot intervals in sediment below the depth of the initial sediment sample. Composite sediment samples collected from each location and submit for laboratory analysis. For each location, if constituents are detected in the composite sediment sample (detected above background concentrations for constituents that have a background concentration), analyze the discrete sediment samples that were collected from that location for the chemicals that were detected (or detected above background concentrations). Also collect a sample from the upper 6 inches of underlying native soil beneath sediment (if any) at each location.

3. Collect soil samples from the soil underlying the dike at 0.5 foot bgs (for chemicals with low mobility in the environment, with limited susceptibility to chemical degradation, and that were likely released at the surface),1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation), and 6 feet bgs.

Seep 1. Collect a grab water sample from the seep. 1. Analyze samples for analytical methods corresponding to chemicals detected in upstream groundwater monitoring wells.

1. Collect the grab water sample as close to the seep discharge point as possible.

Soil Disturbance and Vegetation Clearance Areas

1. Collect soil and soil vapor samples from one to two locations at small‐ to medium‐sized soil disturbance or vegetation clearance areas, targeting topographic low points.

2. For large soil disturbance or vegetation clearance areas with areas of approximately 5,000 square feet or more, consider collecting soil and soil vapor samples on a biased grid, targeting topographic low points.

3. Collect soil samples from drainage pathways downstream of the soil disturbance or vegetation clearance area.

1. Analyze soil samples for analytical methods corresponding to chemicals used in the area. If chemical use in the area is unknown, analyze for the limited target analyte list: VOCs, SVOCs, metals, and TPH. Analyze soil vapor samples for VOCs.

1. Lateral: For large soil disturbance or vegetation clearance areas, soil and soil vapor samples may be collected on a biased grid. The size and spacing of the biased grid will be determined on a site‐specific basis. Samples will typically be collected from soil disturbance and vegetation clearance areas on 100‐foot grids.

Collect soil samples from a minimum of two locations from drainage pathways immediately downstream of the soil disturbance or vegetation clearance area.



Roads 1. Collect soil samples from the following locations, targeting topographic low points:

a. Roads that terminate at soil disturbance areas, vegetation clearance areas, debris areas, large storage areas, or waste disposal areas.

b. Suspect locations (for example, stained or darkened soil or turnouts) observed along roads during review of historical photographs.

1. Analyze soil samples for analytical methods corresponding to chemicals used in the area. If chemical use in the area is unknown, analyze for the limited target analyte list: VOCs, SVOCs, metals, and TPH.

1. Vertical: Collect soil samples at 0.5 foot bgs (for chemicals with low mobility in the environment, with limited susceptibility to chemical degradation, and that were likely released at the surface), 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation), 6 feet bgs, and 10 feet bgs. Analyze samples from 0.5, 1.5, and 6 feet bgs. If the 6‐foot‐bgs sample at a particular location has concentrations that exceed characterization levels, analyze the 10‐foot‐bgs sample at that location.

Undefined Features (that is, features observed on historical photographs for which the feature type is unknown)

1. Collect soil and soil vapor samples from one to two locations at small‐ to medium‐sized undefined features, targeting topographic low points. The number of samples and distribution of sample locations will be determined based on site‐specific conditions such as topography.

2. For large undefined features with areas of approximately 5,000 square feet or more, consider collecting soil and soil vapor samples on a biased grid, targeting topographic low points. Soil and soil vapor samples should be collected from a minimum of three locations at large undefined features. The number of sample locations and distribution of sample locations will be determined based on site‐specific conditions such as topography.

3. Collect soil samples from drainage pathways downstream of the undefined feature.

1. Analyze soil samples for the limited target analyte list: VOCs, SVOCs, metals, and TPH. Add any adjacent CUA‐specific or RFI site‐specific analytical methods to the list, as appropriate. Analyze soil vapor samples for VOCs.

1. Lateral: For large undefined features, soil and soil vapor samples may be collected on a biased grid. The size and spacing of the grid, if performed, will be determined on a feature‐specific basis. Samples will typically be collected on 50‐foot to 100‐foot grids.

Collect soil samples from a minimum of two locations from drainage pathways immediately downstream of the undefined feature.



a The sampling strategy for feature types with historical chemical uses beyond those listed in this report will be evaluated case by case. For all features, samples will not be collected in areas previously recommended for CMS, unless the CMS area has not previously been investigated for one or more

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chemicals associated with the feature (in accordance with the analysis strategy presented in this table). b The majority of CUAs at SSFL were previously identified during the RFA or RFI. However, for new features or areas of interest that may be identified during the ongoing RFI at SSFL, Figure 2 presents the process and criteria for determining if the feature or area represents a CUA or a CNFA area. If analytical results from screening‐level samples collected in accordance with this table indicate that the feature or area represents a CUA, refer to DQO Tables 3 through 10 to evaluate whether additional data collection efforts are required to address the DQOs for the CUA cluster for the various media at SSFL. c For features for which VOCs are listed for analysis in soil and soil vapor, the VOCs in soil samples will only be collected if the VOCs in soil vapor sample cannot be collected (either due to refusal on bedrock at a depth more shallow than 5 feet bgs or due to poor air flow in the soil vapor probe). d Vertical soil sample depths are the depth below ground surface to the bottom of the soil sample interval. Proposed sample depths target approximate intervals and may vary (for example, 0.5, 5, and 10 feet bgs samples have been collected at many locations). Sample depths also may be adjusted based on field observations, lithology, depths of targeted subsurface features, and in consideration of nearby sampling results and gradients. e For the purpose of collecting screening‐level samples to support a CUA or a CNFA area determination, soil and soil vapor samples will be collected from the upper 10 feet of unconsolidated soil, alluvium, and weathered bedrock only. If refusal on bedrock is encountered before 10 feet bgs, a soil sample will be collected immediately above the depth of refusal. The need for analysis of the 10 foot bgs sample is often contingent on analytical results of more shallow samples. However, professional judgment will be used to evaluate the need for analysis of the 10‐foot‐bgs sample (or the sample collected from the depth of bedrock refusal) regardless of the analytical results for more shallow samples to support the evaluation of potential lateral subsurface migration (for example, along soil/bedrock contact and along weather bedrock bedding planes). f Where surface disturbance has occurred, professional judgment will be used to evaluate if the disturbed layer needs to be evaluated separately from the deeper, nondisturbed soil. g Soil vapor samples are to be collected no shallower than 5 feet bgs (unless the soil from which the soil vapor sample is to be collected is covered by concrete or asphalt). If there is insufficient unconsolidated soil thickness to collect a soil vapor sample (i.e., soil thickness is less than 5 feet), but unconsolidated soil thickness is at least 3 feet, then collect a soil sample from the maximum depth possible in lieu of a soil vapor sample. Similarly, if there is insufficient sample volume withdrawn from a soil vapor probe, collect a soil sample (from a minimum depth of 3 feet bgs) in lieu of a soil vapor sample. Analyze soil sample for VOCs. h For the purpose of characterization of soil and sediment, mobile constituents include VOCs, TPH‐gasoline, perchlorate, NDMA, 1,4‐dioxane, formaldehyde, and hexavalent chromium. i While LOX pipelines are excluded from evaluation, LOX storage tanks and LOX piping distribution centers will be investigated at locations where solvents were used to clean these features (see Tanks feature type). j Soil samples will generally be collected below pipelines wrapped in mastic tape during demolition activities. AST = above ground storage tank bgs = below ground surface CMS = corrective measures study CNFA = conditional no further action CUA = chemical use area DQO = data quality objective LOX = liquid oxygen NDMA = n‐nitrosodimethylamine PCB = polychlorinated biphenyl RCRA = Resource Conservation and Recovery Act RFA = RCRA facility assessment RFI = RCRA facility investigation SMOU = Surficial Media Operable Unit SOP = standard operating procedure SVOC = semivolatile organic compound TPH = total petroleum hydrocarbons UST = underground storage tank VOC = volatile organic compound

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TABLE 3 Surface Water Bodies Data Quality Objectivesa Comprehensive Data Quality Objectives, Santa Susana Field Laboratory, Ventura County, California

Step Sources and Chemicals Nature and Extent Fate and Transport CNFA or Cleanup Assessment Remedial Planning Information

Step 1: Problem Statement

Chemicals identified in surface water bodies within CUAs or CUA clusters may represent unacceptable current or future risk to groundwater, human health, or ecological receptors at SSFL.

Step 2: Goals of the Study

Study Question #1: Are all potential sources of contamination to, and chemicals within, surface water bodies identified within CUAs?

Study Question #2: Are the nature and extent of chemical distributions characterized to required characterization levelsb in surface water bodies within CUAs and/or CUA clusters, or are data adequate to recommend the CUA cluster for CMS?

Study Question #3: Are data adequate to evaluate the fate and transport of chemicals in surface water bodies, or are data adequate to recommend the CUA cluster for CMS?

Study Question #4: Do concentrations of chemicals in surface water bodies within CUAs and/or clusters exceed action levels?c

Study Question #5: Are existing data sufficient to perform remedial planning for surface water and source areas that exceed action levels?

Step 3: Information Inputs

1. Historical operations data and chemical use information, including information on historic and current conditions.

2. Previous investigations data (all media).

3. Facility maps.

4. Other historical information:

a. Site inspections and surveys.

b. Aerial photograph review and systematic documentation.

5. Sitewide infrastructure information:

a. Water conveyance system.

b. Drainage system.

6. NPDES data.

7. Biological survey data.

1. Documents:

a. Previous plans, including RFI SAPs, quality assurance project plan, health and safety plan, field SOPs.

b. Previous RFI reports, including previous recommendations for CMS.

c. Previous DTSC comments and response to DTSC comments on the RFI reports.

2. Field data:

a. Analytical data collected to date (all media) and associated quality control data.

b. Field observations (for example, bedrock, staining, debris, photoionization detector screening, etc.).

c. Results of biological surveys, including areas of sensitive habitats, endangered species, and stressed vegetation.

d. Upstream/downstream surface water migration patterns.

3. Conceptual exposure model for human and ecological risks.

1. Documents:

a. Previous RFI reports, including previous recommendations for CMS.

2. Field data:

a. Topography.

b. Surface water flow directions.

c. Locations of surface water drainage pathways.

d. Analytical data collected to date, including downstream soil data.

3. Site conceptual model.

1. Documents:

a. Previous RFI SAPs.

b. Previous RFI reports.


d. Most recent SRAM or SRAM equivalent (for example, exposure assumptions, toxicity data, etc.).

2. Characterization data.


4. Beneficial uses of surface water.

1. Surface water body with chemical concentrations exceeding action levels.

2. Known source of surface water body contamination.

3. Locations of sensitive species and endangered habitats.

Step 4: Boundaries of the Study (applicable spatial and temporal limits)

1. Extent of surface water bodies within each CUA.

2. Dates of chemical use, storage, and disposal within CUAs based on available documentation regarding the period of operations at the CUA.

1. Extent of surface water bodies within each CUA cluster.

2. All data collected during or following the dates of chemical use, storage, and disposal within CUAs.

1. Extent of surface water bodies within each CUA cluster and areas downstream of the surface water body.


1. Extent of surface water bodies within each CUA cluster.


3. For constituents that could degrade (that is, organics), newer data will be used in preference to older data if newer and older data are inconsistent.

1. Extent of surface water bodies and extent of source areas resulting in contaminated surface water bodies.


Step 5: Analytical Approach/ Decision Rules

1. If all sources and chemicals in surface water bodies have been sufficiently identified within CUAs, then confirm that sources and chemicals are clearly identified in RFI documentation; else complete documentation for all potential sources and chemicals identified through the Figure 2 process.

2. Continue to SQ #2. Return to SQ #1 if additional source areas or chemicals are identified.

1. If existing data sufficiently characterize nature and extent within CUA clusters, then confirm that nature and extent of chemicals are clearly defined in RFI documentation; else collect samples following approved SOPs and the sampling strategy presented in Table 4.

2. If a sufficient number of soil samples have been collected from downstream drainage pathways to evaluate chemical migration from a surface water body, then document analytical results in RFI documentation; else collect additional soil samples from downstream drainage pathways following the

1. If chemical concentrations within CUA clusters exceed the characterization levels for surface water and/or sediment, then compare chemical concentrations in downstream soil samples to the characterization levels for soil to evaluate if chemicals in the CUA cluster are migrating via surface water runoff; else, this comparison is not required.

2. Continue to SQ #4 following fate‐and‐transport assessment.

1. If chemical concentrations within CUA clusters exceed action levels for surface water, then recommend CUA cluster for remedial planning; else recommend CUA cluster for CNFA.

2. If chemicals detected above action levels in a surface water body are also detected in underlying and/or downgradient groundwater at concentrations above the corresponding groundwater characterization levels, then recommend surface water body for remedial planning; else recommend CUA cluster containing the surface water body for CNFA.

1. If existing data are sufficient for remedial planning and estimation of the volume of surface water and source areas that exceed action levels within a tolerance of +50% or ‐30%, then confirm data are clearly reported in RFI documentation; else collect data to support remedial planning and volume estimation.

2. If chemicals in surface water pose an imminent threat to receptors and/or chemical migration may be controlled through the use of best management practices, then evaluate the need to perform interim actions; else do not perform this evaluation.

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sampling strategy presented in Table 6.

3. Continue to SQ #3. Return to SQ #2 following collection of additional data, if applicable.

3. Continue to SQ #5, if CUA cluster is recommended for remedial planning.

Step 6: Performance or Acceptance Criteria

1. Review and confirm lines of evidence listed in Figure 2 that demonstrate sources and chemicals within CUAs have been sufficiently identified to proceed with investigation and that they satisfy the final source identification objectives of the RFI.

An uncertainty is the potential for undocumented releases or chemicals to exist that are not included in RFI documentation.

1. Required characterization levels.

2. Confirm that characterization samples were analyzed by an accepted USEPA method with MRLs below required characterization levels. If MRLs are above characterization levels, perform a sensitivity analysis of reporting limits to determine the need for re‐samplingd. Return to SQ #2 following collection of additional data, if applicable.

3. Verify that data used to define nature and extent of chemical distributions are representative of existing and future conditions or are usable for risk management decisions.

4. Verify that new analytical data reported by the laboratory have been validated to assess usability to ensure that data quality indicators (precision, accuracy, representativeness, completeness, comparability, and sensitivity) are met and to determine if the collected data can be used to help answer SQ #2. Verify that appropriate field procedures were followed, that deviations were documented and assessed, that data met the required characterization levels, and that data are usable for project needs.

Uncertainties include the spatial or temporal variability of the samples, as well as attenuation and migration of contaminants.


2. MRLs.

3. Use only data determined to be usable under SQ #2.

An uncertainty is the historic surface water flow patterns from CUA clusters.

1. Action levels for surface water.


Uncertainties are assumptions inherent in the risk assessment, if performed.

1. Action levels.

2. Verify that collected data support estimation of the volume of surface water and source areas that exceed action levels within a tolerance of +50% or ‐30%.

3. Verify that all data and information required for surface water body remedial planning have been collected and documented.

An uncertainty is the volume of surface water and source areas that exceed action levels.

Step 7: Plan for Obtaining the Data

Develop a plan to obtain the data gap information required to be collected so that the weight‐of‐evidence documentation is complete and all sources and chemicals are identified. Move to SQ #2.

1. Determine which data are usable for defining nature and extent of contamination to required characterization levels.

2. Do not collect additional samples if nature and extent are adequately defined based on existing data.

3. If nature and extent are not adequately defined based on existing data, prepare a SAP to define how and where additional samples will be collected to address nature and extent data gaps. Sample collection will follow established SOPs and Table 4. Sample collection will follow Table 6 if it is necessary to collect soil samples from drainage pathways.

1. Fate and transport assessment results will be considered during the cleanup assessment (SQ #4).

1. Recommend remedial planning, if chemicals exceed action levels.

2. Recommend CNFA and document CNFA justification, if chemicals do not exceed action levels.

1. Collect data to determine the potential volume for cleanup of chemicals concentrations that exceed action levels.

2. Collect all data and information required for surface water body remedial planning.

a This table addresses current perennial surface water bodies only. Surface water runoff is managed under the NPDES program. Surface water migration of surface soil is addressed under Table 5. Tables 5, 7, and 9 provide the DQOs for soil and sediment, vadose zone, and groundwater and seeps, respectively. b Boeing complies with the Consent Order for Corrective Action (COCA; DTSC, 2007). On December 6, 2010, DTSC signed the AOC with DOE and NASA, which defines the process for characterization and the cleanup end‐state for portions of SSFL. The December 2010 AOC supersedes the 2007 Order requirements pertaining to soils cleanup and specifically defines “cleanup of soil” and DOE’s and NASA’s required obligations and responsibilities. In addition to the DTSC Orders, California SB990 was passed on October 14, 2007, codified as Section 25359.20 of the California Health and Safety Code and prescribes cleanup of SSFL. Boeing currently conducts the RFI program under the 2007 Order. DOE and NASA have initiated shallow soil characterization under the 2010 AOCs. RFI‐required characterization levels depend on location and will be subject to final regulatory agreements. The RFI‐required characterization levels could be background chemical concentrations, MRLs, or other agreed‐upon risk‐based concentrations. c It is expected that action levels will be developed in the future based on the COCA (DTSC, 2007). For the Boeing land areas, human health and ecological risk assessments will be performed under SQ #4 in accordance with the Standard Risk Assessment Methodology Work Plan, Revision 2 Addendum (MWH, pending) and in accordance with the technical memorandum Integration of the Surficial Media Operable Unit Risk Assessment Methodology with the Data Quality Objectives Process, Boeing RCRA Facility Investigation, SSFL (CH2M HILL, 2013b) (Appendix C). d The sensitivity analysis of MRLs will be based on consideration of the following: (1) locations where the existing nondetect/elevated MRL data are being used to define the extent of contamination outside of areas proposed for CMS and (2) locations within CUAs but outside CMS areas where constituents have nondetect analytical results with MRLs that exceed characterization levels and those same constituents were never detected above MRLs at the RFI site (this is to better address the uncertainty of the presence of specific constituents that were never detected at the RFI site; this evaluation focuses on constituents for which the number of MRL exceedances for that constituent relative to the total number of samples analyzed for that constituent is greater than 25%). Potential matrix interference and technical limitations in obtaining lower reporting limits are also considered in identifying the need to re‐sample at previous locations with nondetect/elevated MRL data.

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PID = photoionization detector

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TABLE 4 Surface Water Bodies Characterization Sampling Strategy Comprehensive Data Quality Objectives, Santa Susana Field Laboratory, Ventura County, California

Media Criteriaa Step‐out and Step‐down Sampling and Analysis Strategy

Surface Water Bodyb (Input from Table 3, SQ #2).

Step‐out samples are collected if chemical concentrations in surface water and/or sediment

c samples exceed required characterization levels.

1. Lateral: Collect soil samples from surface water drainage pathways upstream and downstream of the surface water body, following guidelines described in Table 2.

If a minimum of two surface water samples have not already been collected and analyzed for the analytical methods corresponding to chemicals used in the area and upstream areas of the surface water body, collect surface water samples in accordance with Table 2 and analyze for the missing analytical methods.

Collect sediment samples beneath the surface water body on a biased grid. Samples typically will be collected

on 50‐foot to 100‐foot grids. The grid size will be on the lower end of this range for small surface water bodies and on the higher end of this range for large surface water bodies.

2. Vertical: Collect discrete sediment samples 0.5 foot below the bottom of the surface water body and at 1.5‐foot intervals in sediment below the depth of the initial sediment sample. Composite sediment samples collected from each location. For each location, if constituents are detected in the composite sample (detected above background concentrations for constituents that have a background concentration), analyze the discrete sediment samples that were collected from that location for the chemicals that were detected (or detected above background concentrations).

Also collect a sample from the upper 6 inches of underlying native soil below sediment (if any) at each location.

3. Go to SQ #3 in Table 3.

a While exceedances over characterization levels will typically drive step‐out and step‐down sampling, additional criteria will be considered in determining the need for and distance of step‐out and step‐down sampling. These criteria include site conditions (for example, presence of bedrock outcrops or other surface or subsurface obstructions), field observations (for example, staining), concentration gradients, data quality, and level of certainty regarding historical uses. b This sampling strategy pertains to perennial surface water bodies only. Surface water runoff is managed under the NPDES program. Surface water migration of surface soil is addressed under Table 6. c For the purposes of this comprehensive DQO report, sediment is defined as material at the bottom of perennial surface water bodies and does not include soil in ephemeral streambeds.

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TABLE 5 Soil and Sediment Data Quality Objectivesa Comprehensive Data Quality Objectives, Santa Susana Field Laboratory, Ventura County, California



Chemicals identified within CUAs or clusters in soil and sediment may represent unacceptable current or future risk to human health or ecological receptors at SSFL.


Study Question #1: Are all potential sources and chemicals identified in soil and sediment within CUAs?

Study Question #2: Are the nature and extent of chemical distributions characterized to required characterization levels

b in soil and sediment within CUAs and/or clusters, or are data adequate to recommend the CUA cluster or a portion of the CUA cluster for CMS?

Study Question #3: Are data adequate to evaluate the fate and transport of chemicals in soil and sediment, or are data adequate to recommend the CUA cluster or a portion of the CUA cluster for CMS?

c

Study Question #4: Do concentrations of chemicals in soil or sediment within CUAs and/or clusters exceed action levels?

d

Study Question #5: Are existing data sufficient to perform remedial planning of soil or sediment that exceeds action levels?


1. Historical operations and chemical use information, including information on historic and current conditions.

2. Previous investigation data (all media).

3. Facility maps.




c. Building suspect feature documentation.

d. Building demolition documentation, including any geophysical data.


a. USTs, ASTs, and septic tanks.

b. Sewer lines/system.

c. Water conveyance system.

d. Natural gas distribution system.

e. Surface water drainage.

1. Documents:

a. Previous plans including RFI SAPs, quality assurance project plan, health and safety plan, field SOPs.



2. Field data:

a. Field observations (for example bedrock, staining, debris, photoionization detector screening, etc.).

b. Geophysical data.

c. Analytical data collected to date (all media) and associated quality control data.

d. Gradients.

e. Upstream/downstream migration patterns for surface water and groundwater.

f. Results of biological surveys, including areas of sensitive habitats, endangered species, and stressed vegetation.

3. Conceptual exposure model for human and ecological receptors

1. Documents:


2. Field data:

a. Topographic contours.

b. Surface water flow directions.

c. Locations of surface water drainage pathways.

d. Analytical data collected to date, including downstream soil/sediment sample data.

e. Meteorological data, including wind data from onsite and offsite locations

f. Terrain and land use data.

3. Site‐specific data

a. Source locations.

b. Source size.

c. Source temperature.

d. List of airborne, environmentally persistent chemicals from historic operations.

e. Frequency of historic operations resulting in emissions of environmentally persistent chemicals.

f. Chemical emission rates for environmentally persistent chemicals.

4. Models:

a. Air dispersion model (CALPUFF) developed and applied for selected air emission sources, with input parameters including wind and topographic data (see Appendix B).

b. Site conceptual model

1. Documents:







1. CUA clusters with chemical concentrations exceeding action levels4 in unconsolidated soil and weathered bedrock.

2. Data required to support an evaluation of presumptive remedies:

a. Physical testing data (for example, lithologic and soil vapor properties).

b. Solubility testing data (STLC analysis).

3. Locations of sensitive habitats and endangered species.


1. Extent of each CUA.


1. Extent of each CUA cluster, including areas downstream and downwind of each CUA (not limited to specific RFI site or Boeing RFI subarea).


1. Extent of each CUA cluster, including areas downstream and downwind of each CUA (not limited to specific RFI site or Boeing RFI subarea).


1. Unconsolidated soil and weathered bedrock within each CUA cluster. See Table 7 for the vadose zone DQOs.



1. Unconsolidated soil and weathered bedrock within each CUA cluster. See Table 7 for the vadose zone DQOs.


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1. If all sources and chemicals in soil and sediment have been sufficiently identified within CUAs, then confirm that sources and chemicals are clearly identified in RFI documentation; else complete documentation for all potential sources and chemicals identified through the Figure 2 process.


1. If existing soil and sediment data sufficiently characterize nature and extent within CUA clusters, then confirm that nature and extent of chemicals are clearly defined in RFI documentation; else collect soil and/or sediment samples following approved SOPs and the sampling strategy presented in Table 6.


Air Dispersion and Deposition:

1. If sufficient soil samples have been collected from locations determined during air dispersion fate‐and‐transport modeling (when performed, in accordance with SQ #3), then confirm that nature and extent of chemicals are clearly defined in RFI documentation; else collect surface soil samples from the modeled air deposition locations following approved SOPs and analyze for environmentally persistent chemicals.

Surface Water Migration:

1. If sufficient soil samples have been collected from downstream drainage pathways to evaluate chemical migration from the CUA, then record analytical results in RFI documentation; else collect additional surface soil samples from downstream drainage pathways following approved SOPs and the sampling strategy presented in Table 6.

Migration through Soil Subsurface:

1. If sufficient soil samples have been collected along potential preferential pathways identified during the fate‐and‐transport evaluation, then confirm the nature and extent of chemicals are clearly defined in RFI documentation; else collect soil samples from potential preferential pathways following approved SOPs and the sampling strategy presented in Table 6.

Air Dispersion and Deposition:

1. If the CUA cluster contains a source that is identified for air dispersion modeling in Appendix B, then perform fate‐and‐transport modeling to estimate the locations where soil particulates may have been deposited and to estimate chemical concentrations in particulates potentially deposited to surface soil; else consider other data specific to source(s) in the CUA cluster (that is, size of the source, temperature of the source, frequency of operations, environmentally persistent chemicals that may have been emitted from the source) to determine if air dispersion fate‐and‐transport modeling should be performed.

2. If air dispersion fate‐and‐transport modeling is determined to be required, then review Appendix B and proceed with modeling; else proceed to SQ #4.

3. If air dispersion fate‐and‐transport modeling is performed, then collect surface soil samples from the modeled air deposition locations following SQ #2; else proceed to SQ #4.

4. Continue to SQ #4 after fate‐and‐transport assessment.

Surface Water Migration:

1. If chemical concentrations in surface soil samples within CUAs exceed the characterization levels, then compare chemical concentrations in downstream soil samples (collected within the drainage flow path or adjacent bank deposits) to the characterization levels to evaluate if chemicals in the CUA are migrating via surface water runoff; else this comparison is not required.

2. If areas downstream of CUAs may have received runoff from paved areas, then compare chemical concentrations in downstream soil samples (collected within the drainage flow path or adjacent bank deposits) to the characterization levels to evaluate if chemicals in the CUA are migrating via surface water runoff (unless there is adequate documentation that no chemical usage and no releases occurred at or near the paved areas); else this comparison is not required.


Migration through Soil Subsurface:

1. If chemical concentrations within CUA clusters exceed characterization levels and CUA clusters contain preferential migration pathways (for example, fill around pipelines or the interface between alluvium and bedrock), then evaluate the potential for chemicals to migrate along the preferential pathways; else proceed to SQ #4.

2. If this evaluation identifies the need to collect soil samples along preferential pathways, collect soil samples from preferential pathways following SQ #2 or proceed to SQ #4.


1. If chemical concentrations in soil within CUA clusters exceed action levels for soil and/or if chemical concentrations in sediment within CUA clusters exceed action levels for sediment, then recommend CUA cluster for remedial planning; else recommend CUA cluster for CNFA.

2. Continue to SQ #5, if CUA cluster is recommended for remedial planning.

1. If existing data are sufficient for remedial planning and estimation of the volume of soil and sediment that exceeds action levels within a tolerance of +50% or ‐30%, then confirm data are clearly reported in RFI documentation; else collect data to support remedial planning and volume estimation.

2. If chemicals in soil or sediment pose an imminent threat to receptors and/or chemical migration may be controlled through the use of best management practices, then evaluate the need to perform interim actions; else do not perform this evaluation.

3. Remedial planning will consider the following presumptive soil and sediment remedies:

a. Soil vapor extraction and stabilization for mobile constituents (for example, VOCs).

b. Excavation for less mobile constituents (for example, polychlorinated biphenyls).

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1. Review and confirm lines of evidence listed in Figure 2, which demonstrate that sources and chemicals within CUAs have been sufficiently identified to proceed with investigation and satisfy the final source identification objectives of the RFI.



2. Confirm that characterization samples were analyzed by accepted USEPA methods with MRLs below required characterization levels. If MRLs are above characterization levels, perform a sensitivity analysis of reporting limits to determine the need for re‐sampling.e Return to SQ #2 following collection of additional data, if applicable.

3. Verify that data used to define the nature and extent of chemical distributions are representative of existing and future conditions or usable for risk management decisions.

4. Verify that new analytical data reported by the laboratory have been validated to assess usability to ensure that data quality indicators (precision, accuracy, representativeness, completeness, comparability, and sensitivity) are satisfied and to determine if collected data can be used to help answer SQ #2. Verify that appropriate field procedures were followed, any deviations were documented and assessed, data met the required characterization levels, and data are usable for project needs.

Uncertainties include the spatial or temporal variability of the samples and the attenuation and migration of contaminants.

1. MRLs.

2. Background concentrations.

3. Characterization levels.

4. Use only data determined to be useable under SQ #2.

Uncertainties include historic surface water and air flow patterns from CUAs and chemical emission rates.

1. Action levels.

2. Use only the data determined to be usable under SQ #2.

An uncertainty is carrying forward the assumptions inherent in the risk assessment, if performed.

1. Action levels.

2. Verify that collected data support estimation of the volume of soil and sediment that exceeds action levelsd within a tolerance of +50% or ‐30%.

3. Verify that all data and information required for remedial planning have been collected and documented.

An uncertainty is the volume of soil and sediment with chemical concentrations that exceed action levels.


1. Develop a plan to obtain the data gap information required to be collected so that the weight‐of‐evidence documentation is complete and all sources and chemicals, within CUAs are identified. Move to SQ #2.

1. Determine which data are usable for defining nature and extent of contamination to required characterization levels.

2. Do not collect additional samples if nature and extent are adequately defined based on existing data.

3. If nature and extent are not adequately defined based on existing data, prepare a SAP to define how and where additional soil and sediment samples will be collected to address nature and extent data gaps. Sample collection will follow established SOPs and Table 6.

1. Prepare a plan to perform modeling using site‐specific and site‐relevant data to support fate‐and‐transport assessment.

2. Collect additional data if determined to be necessary during fate‐and‐transport assessment.

3. Results of fate‐and‐transport assessments will be considered during the cleanup assessment (SQ #4).

1. Recommend remedial planning if chemicals exceed action levels.


1. Collect data to determine the potential volume for cleanup if concentrations of chemicals exceed action levels.

2. Collect data and information required for soil and sediment remedial planning.

a This table pertains to sediment, unconsolidated soil, and weathered bedrock that may be accessed with a hand auger or direct‐push rig in the SSFL areas for which Boeing is the responsible party. Deeper soil and bedrock are evaluated in Table 7. For the purposes of the Comprehensive DQO Report, sediment is defined as material at the bottom of perennial surface water bodies and does not include soil in ephemeral streambeds. Soil and sediment data collected from the upper 10 feet will be used in future human health and ecological risk assessments. Refer to the DQO tables included in Master Work Plan/Field Sampling and Analysis Plan, Co‐located Sampling at Area IV, Santa Susana Field Laboratory, Ventura County, California (CDM, 2011) and Work Plan for Chemical Data Gap Investigation Phase 3 Soil Chemical Sampling at Area IV, Santa Susana Field Laboratory, Ventura County, California (CDM, 2012) for the DQOs for soil and sediment in SSFL areas for which DOE is the responsible party. Refer to the DQO table in Draft Remedial Investigation Work Plan for NASA Sites at the Santa Susana Field Laboratory, Ventura County, California (NASA, 2011) for the DQOs for soil and sediment in SSFL areas for which NASA is the responsible party. Tables 3, 7, and 9 provide the DQOs for surface water bodies, vadose zone, and groundwater and seeps, respectively, for the entire SSFL (Boeing, DOE, and NASA areas). The vapor intrusion pathway for all soil, rock, and groundwater is presented in Tables 7 and 9. b Boeing complies with the Consent Order for Corrective Action (COCA; DTSC, 2007). On December 6, 2010, DTSC signed the AOC with DOE and NASA, which defines the process for characterization and the cleanup end state for portions of SSFL. The December 2010 AOC supersedes the 2007 Order requirements pertaining to soils cleanup and specifically defines “cleanup of soil” and DOE’s and NASA’s required obligations and responsibilities. In addition to the DTSC Orders, California SB990 was passed on October 14, 2007, codified as Section 25359.20 of the California Health and Safety Code and prescribes cleanup of SSFL. Boeing currently conducts the RFI program under the 2007 Order. DOE and NASA have initiated shallow soil characterization under the 2010 AOCs. RFI required characterization levels depend on location and will be subject to final regulatory agreements. The RFI required characterization levels could be background chemical concentrations, MRLs, or other agreed upon risk‐based concentrations. c See Table 7 for fate‐and‐transport DQOs related to the mass flux of contaminants from the vadose zone to indoor air and the mass flux of contaminants from the vadose zone to groundwater. d It is expected that action levels will be developed in the future based on the COCA (DTSC, 2007). For the Boeing land areas, human health and ecological risk assessments will be performed under SQ #4 in accordance with the Standard Risk Assessment Methodology Work Plan, Revision 2 Addendum (MWH, pending) and in accordance with the technical memorandum, Integration of the Surficial Media Operable Unit Risk Assessment Methodology with the Data Quality Objectives Process, Boeing RCRA Facility Investigation, SSFL (CH2M HILL, 2013b) (see Appendix C). e The sensitivity analysis of MRLs will be based on consideration of the following: (1) locations where the existing nondetect/elevated MRL data are being used to define the extent of contamination outside of areas proposed for CMS and (2) locations within CUAs but outside CMS areas where constituents have nondetect analytical results with MRLs that exceed characterization levels and those same constituents were never detected above MRLs at the RFI site (this is to better address the uncertainty of the presence of specific constituents that were never detected at the RFI site; this evaluation focuses on constituents for which the number of MRL exceedances for that constituent relative to the total number of samples analyzed for that constituent is greater than 25%). Potential matrix interference and technical limitations in obtaining lower reporting limits are also considered in identifying the need to re‐sample at previous locations with nondetect/elevated MRL data.

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TABLE 6 Soil and Sediment Characterization Sampling Strategya

Comprehensive Data Quality Objectives Technical Memorandum, Santa Susana Field Laboratory, Ventura County, California

Media Criteriab Step‐out and Step‐down Sampling and Analysis Strategy

Soil and Sediment (Input from Table 5, SQ #2).

Step‐out samples are collected if chemical concentrations in a soil or sediment sample exceed required characterization levels. If characterization levels are not exceeded in the initial sample, consideration will be given to collecting additional samples to better assess potential contamination, unless there is adequate documentation that no chemical usage and releases occurred in the area, or that physical conditions exist (such as topographic isolation) that would limit further migration relative to the original sample location. For metals and dioxins, step‐out samples are not collected if chemical concentrations slightly exceed required characterization levels over a wide area with no apparent trend in concentrations, and the site conceptual model does not suggest a potential for higher concentrations within or beyond the sampled area.

1. Lateral Extent for Soil and Sediment: Advance a step‐out location boring approximately 25 to 100 feet from original sample location, as appropriate for field conditions. Step‐out distance will be on lower end of range for smaller sites, for constituents that are less mobile (for example, PCBs and heavy carbon‐range hydrocarbons), and for concentrations slightly above required characterization levels in the original sample. Step‐out distance will be on higher end of range for larger sites, more mobile constituents (for example, VOCs), and for concentrations greatly above required characterization levels in the original sample. Step‐out distance will also be based on the estimated release volume, estimated areal extent of impacted soils, and concentration range of impacted soils. In cases where a single detection may warrant additional sampling or re‐sampling, a step‐out distance of less than 25 feet may be warranted. For areas previously recommended for CMS, collect step‐out samples along the periphery of the CMS area, rather than within the CMS area. Analyze step‐out samples for the analytical group (for example, VOCs, PCBs, or metals) for which specific chemicals were detected above required characterization levels in the original sample, unless the site conceptual model suggests only specific chemicals are required for analysis.

Lateral Extent for Drainage Channels: Collect soil samples from banks of unlined drainage channels if soil samples collected from the bottom of the drainage channel exceed required characterization levels and if supported by the site conceptual model. Collect a soil sample from each bank at representative locations of overbank deposits along the drainage channel. If the site conceptual model suggests contaminant migration to the channel from an upslope source adjacent to the channel, then multiple soil samples will be collected from the bank and slope adjacent to the upslope source and no samples will be collected from the opposite bank.

Collect soil samples from the bottom of lined and unlined drainage channels at locations upstream and downstream of the original drainage channel sample (except for the case of an upslope source adjacent to the channel, in which case only a downstream sample will be collected from the drainage channel). Step‐out distance for upstream and downstream samples should follow the step‐out distance guidelines described above, with the goal of targeting the same material that was sampled in the original drainage channel sample and with consideration of potential upstream and downstream sources. For lined drainage channels, target unpaved areas upstream and downstream of the channel lining and locations with cracks or joints in the channel lining.

Air Dispersion and Deposition. Soil samples may be collected along transects originating from a CUA to evaluate the transport of dust by air pathway (air dispersion and deposition of air borne materials). The need to collect soil samples within a CUA cluster to evaluate this pathway will be determined case by case and in accordance with SQ #3 in Table 5.

2. Vertical Extent for Soil:

Collect a soil sample approximately 5 feet below the depth of original sample in which required characterization levels were exceeded. Step‐down distance will vary based on chemical type, depth of bedrock, and concentrations in original sample (relative to required characterization levels). At step‐out locations, collect samples from the same depth interval as the original sample that exceeded characterization levels. At step‐out locations, also collect samples from depths shallower (for example, 0.5 feet bgs for chemicals with low mobility in the environment, with limited susceptibility to chemical degradation, and that were likely released at the surface and 1.5 feet bgs for chemicals that are volatile, mobile d, and subject to degradation) and deeper (for example, 6 and 10 feet bgs)

c than the original sample unless the site conceptual model or other data are sufficient to conclude that soils shallower and/or deeper than the depth of the original sample are unlikely to be affected by the release at the step‐out location. (At a minimum, soil samples will be collected from the same depth as the original sample and from a depth greater than the original sample at step‐out locations. Even if the deeper step‐out sample is not initially analyzed based on the site conceptual model, the deeper sample will be analyzed if the analytical results of the shallower sample[s] at the step‐out location exceed characterization levels).

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At transformer locations, collect a sample 0.5 to 1 foot below depth of original sample in which required characterization levels were exceeded.

Analyze step‐down samples for the analytical group (for example, VOCs, PCBs, or metals) for which specific chemicals were detected above required characterization levels in the original sample, unless the site conceptual model suggests only specific chemicals are required for analysis.

Vertical Extent for Sediment:

Collect discrete sediment samples at 1.5‐foot intervals below the depth of the original sediment sample and collect a soil sample from the upper 6 inches of underlying native soil beneath sediment if any). At step‐out locations, collect discrete sediment samples from the depth of the original sample and at 1.5‐foot intervals below the depth of the original sediment sample. Also collect a soil sample from the upper 6 inches of underlying native soil beneath sediment if any) at step‐out locations. Composite sediment samples collected from each location and submit for laboratory analysis. For each location, if constituents are detected in the composite sediment sample (detected above background concentrations for constituents that have a background concentration), also analyze the discrete samples that were collected from that location for the chemicals that were detected (or detected above background concentrations).

Vertical Extent for Drainage Channels:

Unlined drainage channels: Collect soil samples at 0.5 foot bgs (for chemicals with low mobility in the environment and with limited susceptibility to chemical degradation), 1.5 feet bgs (for chemicals that are volatile, mobile d, and subject to degradation), and from the base of accumulated alluviume along drainage channels. Collect soil samples at 0.5 foot bgs (for chemicals with low mobility in the environment and with limited susceptibility to chemical degradation) and 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation) from banks of unlined drainage channels if they were also potentially impacted.

Lined drainage channels: Collect a sample at 1 foot below bottom of material that lines the drainage, targeting areas where the lining is cracked, if possible. Collect samples upstream and downstream of the channel lining at 0.5 foot bgs (for chemicals with low mobility in the environment and with limited susceptibility to chemical degradation), 1.5 feet bgs (for chemicals that are volatile, mobile, and subject to degradation), and from the base of alluvium accumulated in the channel.

e


a This table pertains to sediment, unconsolidated soil, and weathered bedrock that may be accessed with a hand auger or direct‐push rig in the SSFL areas for which Boeing is the responsible party. Deeper soil and bedrock are evaluated in Table 7. For the purposes of this comprehensive DQO report, sediment is defined as material at the bottom of perennial surface water bodies and does not include soil in ephemeral streambeds. Soil and sediment data collected from the upper 10 feet will be used in future human health and ecological risk assessments. Refer to the DQO tables included in Master Work Plan/Field Sampling and Analysis Plan, Co‐located Sampling at Area IV, Santa Susana Field Laboratory, Ventura County, California (CDM, 2011) and Work Plan for Chemical Data Gap Investigation Phase 3 Soil Chemical Sampling at Area IV, Santa Susana Field Laboratory, Ventura County, California (CDM, 2012) for the DQOs for soil and sediment in SSFL areas for which DOE is the responsible party. Refer to the DQO table in Draft Remedial Investigation Work Plan for NASA Sites at the Santa Susana Field Laboratory, Ventura County, California (NASA, 2011) for the DQOs for soil and sediment in SSFL areas for which NASA is the responsible party. b While exceedances over characterization levels will typically drive step‐out and step‐down sampling, additional criteria will be considered in determining the need for and distance of step‐out and step‐down sampling. These criteria include site‐specific conditions (for example, presence of bedrock outcrops or other surface or subsurface obstructions, release migration mechanisms), field observations (for example, staining), concentration gradients, data quality, and level of certainty regarding historical uses. As a general rule, the step‐out distances will range from 25 to 100 feet, but may be less than 25 feet if there are single detections that warrant re‐sampling or step‐out sampling. Step‐out distances will typically not exceed 100 feet. c The sample depths shown are depth below ground surface to the bottom of the soil sample interval. Sample depths target approximate intervals and may vary (for example, 0.5‐, 5‐, and 10‐foot‐bgs samples have been collected at many locations). Sample depths also may be adjusted based on field observations, lithology, depths of targeted subsurface features, and in

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consideration of nearby sampling results and gradients. d For the purpose of characterization of soil and sediment, mobile constituents include VOCs, TPH‐gasoline, perchlorate, NDMA, 1,4‐dioxane, formaldehyde, and hexavalent chromium. e Samples targeting the base of alluvium should be collected from fine‐grained, noncompacted soil located at the bottom of the drainage channel.

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TABLE 7 Vadose Zone Data Quality Objectivesa Comprehensive Data Quality Objectives, Santa Susana Field Laboratory, Ventura County, California



Chemicals identified in the vadose zone within CUAs or CUA clusters and above downgradient groundwater plumes may represent unacceptable current or future risk to groundwater, human health, or ecological receptors at SSFL.


Study Question #1: Are all potential sources and chemicals identified in the vadose zone soil, rock, and soil vapor within CUAs?

Study Question #2: Are the nature and extent of chemical distributions in vadose zone soil, rock, and soil vapor adequatelyb characterized to the required characterization levels, or are data adequate to recommend the CUA cluster or a portion of the CUA cluster for CMS?

Study Question #3: Are data adequateb to evaluate the fate and transport of chemicals in the vadose zone, or are data adequate to recommend the CUA cluster or a portion of the CUA cluster for CMS?

Study Question #4: Do concentrations of chemicals in the vadose zone within CUA clusters and/or above downgradient groundwater plumes exceed action levels?c

Study Question #5: Are existing data sufficient to perform remedial planning in vadose zone soils and/or soil vapor that exceed action levels?


1. Historical operations and chemical use information, including historic and current conditions.


3. Facility maps.





d. Building demolition documentation.






e. Drainage system.

1. Documents:

a. Previous plans including RFI SAPs, quality assurance project plan, health and safety plan, field SOPs.



2. Field Data:

a. Field observations (for example bedrock, staining, debris, photoionization detector screening, etc.).

b. Geophysical data.

c. Analytical data collected to date (all media) and associated quality control data.

d. Depth to groundwater.

e. Upstream/downstream migration patterns for surface water and groundwater.

3. Conceptual exposure model for human and ecological receptors.

4. Output or results from SSFL groundwater flow model.

1. Documents:


2. Field Data:

a. Analytical data collected to date, including depth‐discrete vapor and rock porewater data.

b. Properties of lithologic and hydrostratigraphic units.

c. Gradients and aquifer/aquitard properties.

d. Continuous profile of porosity and water content in vadose zone.

e. Effect of faults and shale beds and other low permeability units.

f. Depth to groundwater.

g. Water infiltration recharge rate.

h. Areas of previous or future excavations.

3. Models:

a. Vapor intrusion pathway evaluation (developed based on DTSC, 2011b, see Appendix A) to assess potential indoor air quality risks.

b. Mann‐Kendall (or similar) plume stability evaluation (see Table 8)

c. SESOIL for vadose zone mass flux of contaminants to groundwater evaluation (see Appendix D).

d. SSFL groundwater flow model to evaluate groundwater flow conditions.

4. Existing and future building data:

a. Locations

b. Construction/conditions

c. Activities and occupancy

d. Building demolition plan

1. Documents:



c. DTSC comments and response to DTSC comments on the RFI reports.




4. Action levels

5. Results of fate‐and‐transport modeling performed under SQ #3.

1. Documents:

a. Bedrock Vapor Extraction Field Experiment Treatability Study Work Plan.

2. Field data:

a. Chemical concentrations in vadose zone soil, rock, and/or soil vapor that exceed action levels.c

b. Depth to groundwater.

c. Data required to support an evaluation of appropriate potential technologies and remedial options, which may include.

- Physical testing data, including data planned for collection during an upcoming treatability study for vapor extraction in fractured bedrock (for example, extraction rate, vacuum response, effects of lithology on advective flow paths, VOC mass flow rate, and diffusive response of VOCs following testing).

- Solubility testing data (for example, synthetic precipitation leaching procedure analysis).

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1. Extent of CUAs within vadose zone.


1. Vadose zone; within CUA clusters and above downgradient groundwater plumes.




3. The temporal nature of identified contamination is understood for current conditions and may be used to estimate future conditions; for vadose zone fate‐and‐transport evaluation, a 50‐year timeframe into the future will be used (Appendix D).

4. Recent (that is, last 3 years) groundwater sampling results from monitoring locations along the flow path from the CUA cluster.







1. If all sources and chemicals in vadose zone soil, rock, and soil vapor have been sufficiently identified within CUAs, then confirm that sources and chemicals are clearly identified in RFI documentation; else complete documentation for all potential sources and chemicals identified through the Figure 2 process.


Vadose Zone Soil Vapor:

1. If existing soil vapor data sufficiently characterize nature and extent in the vadose zone within CUA clusters and above downgradient groundwater plumes, then confirm that nature and extent of chemicals are clearly defined in RFI documentation; else collect additional soil vapor samples following approved SOPs and the sampling strategy presented in Table 8.

d


Vadose Zone Mass Flux to Groundwater:

1. If an area of known release of DNAPL associated with rocket engine or equipment testing is located within the CUA cluster, and a deep boring has not been advanced at or near the DNAPL input location, then advance a deep boring

e to characterize the vadose zone.

2. If existing soil, rock, and soil vapor data sufficiently characterize nature and extent in the vadose zone within CUA clusters, then confirm that nature and extent of chemicals are clearly defined in RFI documentation; else determine if deep borings are required in accordance with Table 8 and Figure 10.


Vadose Zone Soil Vapor:

1. If CUA clusters or areas above groundwater plumes contain existing buildings not planned for future demolition and if subslab samples collected in accordance with Tables 2 or 8 exceed soil vapor to indoor air characterization levels, then collect concurrent indoor air, outdoor air, and subslab samples following the sampling strategy presented in Table 8; else do not collect additional indoor air, outdoor air, or subslab samples.

2. If CUA clusters or areas above groundwater plumes contain existing buildings planned for future demolition, then use empirical data and multiple lines of evidence (including the groundwater‐to‐indoor air evaluation described in Appendix A) to assess the fate and transport of VOCs from the vadose zone to indoor air; else do not perform this assessment.



1. If concentrations of chemicals in soil, rock, or soil vapor exceed BTVs or GCLs and groundwater has been impacted at concentrations above GCLs in wells along the flow path from the CUA cluster, then continue to SQ #4; else continue to Step 2 below.

2. If concentrations of chemicals in soil, rock, or soil vapor exceed BTVs or GCLs and groundwater has not been impacted at concentrations above GCLs in wells along the flow path from the CUA cluster due to this release, then perform vadose zone fate‐and‐transport modeling to evaluate potential future impacts to groundwater (see Appendix D); else continue to Step 3. Groundwater impact assessment will be based on sampling results from within the last 3 years.

3. Using professional judgment, consider, on a case‐by‐case basis, the technical merits of vadose zone fate‐and‐transport modeling to evaluate potential future impacts to groundwater in additional areas where results may add to the lines of evidence to support the DQO SQs #3 and #4 results or do not perform modeling.


Post‐Remediation Mass Flux from Contaminated to Clean Areas:

1. If soil vapor with chemical concentrations that exceed the required characterization levels is located below or near a past

Indoor Air Quality Concerns:

1. For existing buildings not planned for future demolition, if chemical concentrations detected in indoor air samples exceed indoor air action levels

due to vapor intrusion, then recommend vadose zone for remedial planning; else recommend for CNFA.

2. For existing buildings planned for future demolition and for future buildings not yet constructed, if soil vapor to indoor air fate‐and‐transport assessment estimates future indoor air concentrations that exceed indoor air action levels

c and/or if shallow soil vapor samples exceed soil vapor‐to‐indoor air action levels, then recommend vadose zone for remedial planning; else recommend for CNFA.

3. Continue to SQ #5 if CUA cluster is recommended for remedial planning.

Burrowing Ecological Receptor Concerns:

1. If chemical concentrations in soil vapor within CUA clusters exceed burrowing ecological receptor action levels, then recommend CUA cluster for remedial planning; else recommend CUA cluster for CNFA.



1. If concentrations of chemicals in soil, rock, and/or soil vapor exceed GCLs, and it appears that groundwater has been impacted at concentrations above GCLsf in wells along the flow path from the CUA cluster due to this release, then recommend vadose zone for remedial planning; else continue to Step 2.

2. If fate‐and‐transport modeling results indicate contaminants present in the vadose zone can be leached to the water table at concentrations that will exceed their respective GCLs over the next 50 years, then recommend vadose zone for remedial planningg ; else continue to Step 3.

3. As an additional review step, evaluate data on a site‐specific basis using professional judgment and

1. If existing data are sufficient for remedial planningf and estimation of the volume of soil, rock, and soil vapor that exceeds action levels within a tolerance of +50% or ‐30%, then confirm data are clearly reported in RFI documentation; else collect data to support remedial planning and volume estimation.

2. If chemicals in the vadose zone pose an imminent threat to receptors, then evaluate the need to perform interim actions; else do not perform this evaluation.

3. Remedial planning will consider the appropriate potential technologies and remedial options.

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or future excavation area, then perform fate‐and‐transport modeling to evaluate the potential for the contaminated soil vapor to migrate into “clean” excavation fill; else do not perform this evaluation.


multiple lines of evidence; if vadose zone concentrations are increasing with depth and groundwater concentrations are above GCLs in wells along the flow path from the CUA cluster, then recommend vadose zone for remedial planning; else recommend vadose zone for CNFA.


g

Post‐remediation Mass Flux from Contaminated to Clean Areas:

1. If fate‐and‐transport modeling indicates contaminated soil vapor will migrate into “clean” excavation fill and will result in chemical concentrations that exceed soil vapor‐to‐indoor air action levels in the fill, then recommend vadose zone for remedial planning; else recommend for CNFA.



1. Review and confirm lines of evidence listed in Figure 2, which demonstrate that sources and chemicals within CUAs have been sufficiently identified to proceed with investigation and satisfy the final source identification objectives of the RFI.

An uncertainty is the potential for undocumented releases or chemicals to exist that are not included in RFI documentation. Also, comingled plumes may be difficult to identify the sources or impacts.

1. Soil vapor to indoor air characterization levels.

h

2. Burrowing ecological receptor characterization levels.

i

3. Vadose zone mass flux to groundwater characterization levels.

j

4. Confirm that characterization samples were analyzed by accepted USEPA methods with MRLs below the required characterization levels. If MRLs are above these levels, perform a sensitivity analysis of reporting limits to determine the need for re‐sampling.

k Return to SQ #2 following collection of additional data, if applicable.

5. Verify that data used to define nature and extent of chemical distributions are representative of existing and future conditions or usable for risk management decisions.

6. Verify that new analytical data reported by the laboratory have been validated to assess usability to ensure that data quality indicators (precision, accuracy, representativeness, completeness, comparability, and sensitivity) are met and to determine if the collected data can be used to help answer SQ #2.

7. Verify that appropriate field procedures were followed, and deviations were documented and assessed, data met the required characterization levels, and data are usable for project needs.

1. Soil vapor to indoor air characterization levels.

2. Vadose mass flux to groundwater characterization levels.j


An uncertainty is the effect of faults and shale beds in vadose zone mass flux to indoor air and groundwater.

1. Indoor air action levels.

2. Soil vapor‐to‐indoor air action levels.

3. Burrowing ecological receptor action levels.

4. GCLsj.



1. Action levels.

2. Verify that collected data support estimation of the volume of soil, rock, and soil vapor that exceeds action levels within a tolerance of +50% or ‐30%.

3. Verify that all data and information required for the vadose zone remedial planning have been collected and documented.

Uncertainties include the volume of soil, rock, and soil vapor with chemical concentrations that exceed action levels and the efficacy of specific treatment technologies in addressing various combinations of chemicals and lithologies.

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Uncertainties include the spatial or temporal variability of the samples and attenuation and migration of the contaminants.


1. Develop a plan to obtain the data gap information required to be collected so that the weight‐of‐evidence documentation is complete and all sources and chemicals within CUAs are identified. Move to SQ #2.

1. Determine which data are usable for defining nature and extent of contamination in vadose zone to the required characterization levels.

2. Do not collect additional samples if nature and extent are adequately defined to the required characterization levels based on existing data.

3. If nature and extent are not adequately defined based on existing data, prepare a SAP to define how and where additional soil, rock, and soil vapor samples will be collected to address nature and extent data gaps. Sample collection will follow established SOPs and Table 8.

1. Prepare a plan to perform modeling using site‐specific data to support fate‐and‐transport assessment.

2. Fate‐and‐transport assessment results will be considered during the cleanup assessment (SQ #4).

1. Recommend remedial planning if chemicals exceed action levels and/or if the need for remedial planning is supported by fate‐and‐transport modeling results.

2. Recommend CNFA and document CNFA justification if chemicals do not exceed action levels and/or if CNFA is supported by fate‐and‐transport modeling results.

1. Collect data to determine the potential volume for cleanup if concentrations of chemicals exceed action levels.

c

2. Collect data and information required for the vadose zone remedial planning.

a For the purposes of this comprehensive DQO report, the vadose zone is defined as soil, rock, and soil vapor between the ground surface and the groundwater table. Tables 3, 5, and 9 provide the DQOs for surface water bodies, soil and sediment, and groundwater and seeps, respectively. b Adequate is defined by the remaining steps in this table and by Table 8 and Figure 10. c It is expected that action levels will be developed in the future based on the COCA (DTSC, 2007). For the Boeing land areas, human health and ecological risk assessments for the SMOU will be performed under SQ #4 in accordance with the Standard Risk Assessment Methodology Work Plan, Revision 2 Addendum (MWH, pending) and in accordance with the Integration of the Surficial Media Operable Unit Risk Assessment Methodology with the Data Quality Objectives Process, Boeing RCRA Facility Investigation, SSFL (CH2M HILL, 2013b) (see Appendix C). d Only soil vapor samples collected between 0 and 6 feet below ground surface will be used to evaluate burrowing ecological receptors. e A deep boring is defined as a boring drilled through the vadose zone and 5 feet into groundwater. f Remedial planning may contain a mitigation component. The DTSC mitigation advisory states that if it is shown that vapor migration is occurring and presents unacceptable risks, mitigation is required. Mitigation could include, but is not limited to fences, vapor barriers, and passive venting systems. g Multiple lines of evidence will be used to support CNFA and remedial planning recommendations, including the results of fate‐and‐transport modeling and field data. h The residential soil vapor characterization levels presented in Appendix A, Recommended Approach for Assessing Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, SSFL (CH2M HILL, 2013d) are the proposed characterization levels for performing indoor air quality assessments. i The low toxicity reference values published in Inhalation Toxicity Reference Value Updates for Use in Ecological Risk Assessments at the Santa Susana Field Laboratory, Ventura County, California ‐ Technical Memorandum (MWH and CH2M HILL, 2011) are the proposed characterization levels for evaluating the burrowing ecological receptor. j The basis for GCLs is described in Section 5.1.4.3 of this comprehensive DQO report. k The sensitivity analysis of MRLs will be based on consideration of the following: (1) locations where the existing nondetect/elevated MRL data are being used to define the extent of contamination outside of areas proposed for CMS and (2) locations within CUAs but outside CMS areas where constituents have nondetect analytical results with MRLs that exceed characterization levels and those same constituents were never detected above MRLs at the RFI site (this is to better address the uncertainty of the presence of specific constituents that were never detected at the RFI site; this evaluation focuses on constituents for which the number of MRL exceedances for that constituent relative to the total number of samples analyzed for that constituent is greater than 25%). Potential matrix interference and technical limitations in obtaining lower reporting limits are also considered in identifying the need to re‐sample at previous locations with nondetect/elevated MRL data.

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TABLE 8 Vadose Zone Characterization Sampling Strategy Comprehensive Data Quality Objectives, Santa Susana Field Laboratory, Ventura County, California

Media Step‐out and Step‐down Sampling and Analysis Criteria and Strategy

Soil Vapor in Vadose Zone (Input from Table 7, SQ #2).

1. Lateral extent to support indoor air quality and burrowing ecological receptor assessments: Advance soil vapor points around sample locations with concentrations above required SVCLsa approximately 50 to 100 feet from original sample location, or as appropriate for field conditions.b Collect step‐out samples from unconsolidated soil (alluvium) at same depth as original sample (or 5 feet bgs if original sample is more shallow than 5 feet bgs). For areas previously recommended for CMS, collect step‐out samples along the periphery of the CMS area, rather than within the CMS area. Samples for which sufficient sample volume was withdrawn will be analyzed for VOCs.

If there is insufficient unconsolidated soil thickness to collect a soil vapor sample (that is, soil thickness is less than 5 feet), but unconsolidated soil thickness is at least 3 feet, then collect a soil sample from the maximum depth possible in lieu of a soil vapor sample. Similarly, if insufficient sample volume is withdrawn from a soil vapor probe, then collect a soil sample (from a minimum depth of 3 feet bgs). Analyze soil sample for VOCs.

2. Vertical extent to support indoor air quality and burrowing ecological receptor assessments: For soil vapor samples with VOC concentrations exceeding one or more SVCLs, collect soil vapor samples every 5 feet below the soil vapor sample until refusal is reached with a direct‐push rig or until detected VOC concentrations in soil vapor are below corresponding SVCLs.

3. For existing buildings that are not planned for future demolition, collect subslab samples during two sampling events in accordance with Final Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air (DTSC, 2011b). During each event, collect two subslab samples beneath the building (if such samples were not previously collected) in accordance with Table 2. Subsequent to collection of the subslab samples, collect concurrent indoor air, outdoor air, and subslab samples if analytical results for the original subslab samples exceed characterization levels. Collect a minimum of two sets of concurrent indoor air, outdoor air, and subslab samples to support evaluation of the vapor intrusion pathway in the human health risk assessment, if performed. The need for additional samples will be determined case by case, taking the size and layout of the building into consideration.


a For indoor air quality assessments, the recommended SCVLs are the residential soil vapor characterization levels presented in Appendix A. For burrowing ecological receptor assessments, the recommended SVCLs are the low toxicity reference values published in Inhalation Toxicity Reference Value Updates for Use in Ecological Risk Assessments at the Santa Susana Field Laboratory, Ventura County, California ‐ Technical Memorandum (MWH and CH2M HILL, 2011). Samples collected to support burrowing ecological receptor assessments will only be collected from the upper 6 feet of unconsolidated soil (the depth over which burrowing is expected to occur). b Additional information will be considered in determining the distance of step‐out sampling. These criteria include site conditions (for example, presence of bedrock outcrops or other surface or subsurface obstructions), field observations (for example, staining), concentration gradients, data quality, and level of certainty regarding historical uses. c Soil vapor samples may be collected from consolidated material (that is, bedrock) in the future, pending the results of a treatability study that is planned to assess the effectiveness of vapor extraction in fractured sedimentary bedrock.

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TABLE 9 Groundwater and Seeps Data Quality Objectivesa Comprehensive Data Quality Objectives, Santa Susana Field Laboratory, Ventura County, California



Chemicals identified in groundwater plumes beneath and/or downgradient of CUA clusters may represent unacceptable current or future risk to human health or ecological receptors at SSFL.


Study Question #1: Are all potential sources and chemicals identified in groundwater?

Study Question #2: Are the nature and extent of chemicals characterized to required characterization levelsb in groundwater, or are data adequate to recommend the CUA cluster or portions of the CUA cluster for CMS?

Study Question #3: Are data adequate to evaluate the fate and transport of chemicals in groundwater, including volatilization of chemicals from groundwater to the vadose zone and migration of chemicals to seeps and off‐site wells, or are data adequate to recommend the CUA cluster or portions of the CUA cluster for CMS?

Study Question #4: Do concentrations of chemicals in groundwater exceed action levels,c and/or do concentrations of chemicals present significant risk to current or future receptors (indoor air, seeps, or off‐site wells)?

Study Question #5: Are existing data sufficient to perform remedial planning of groundwater with chemical concentrations above action levels?c


1. Historical operations and chemical use information, including historic and current conditions.


3. Facility maps.





d. Building demolition documentation.






e. Drainage system.

1. Documents:

a. Site‐wide groundwater remedial investigation report and accompanying site conceptual model report, including previous recommendations for CMS.

b. Data gaps SAP.

c. Quarterly/annual groundwater monitoring reports.

2. Field data:

a. Field observations (for example, bedrock, staining, debris, photoionization detector screening, etc.).

b. Analytical data collected to date (all media) and associated QC data, including depth discrete rock porewater and groundwater concentrations in wells and piezometers over time.

c. Hydraulic head and gradient data.

d. Lithologic units, fractures, and fault data.

e. Locations of groundwater monitoring wells, source areas, and potential receptors.

f. Entry pressures, porosity, transmissivity, and storage.

3. Models:

a. Output from SSFL three‐dimensional groundwater flow and two‐dimensional discrete fracture network transport models.

b. Conceptual exposure model for human and ecological receptors.

1. Documents:

a. Site‐wide groundwater remedial investigation report (MWH, 2009a) and accompanying site conceptual model report, including previous recommendations for CMS.

2. Field data:

a. Hydrostratigraphy, geology, hydrology, and hydrogeology data.

b. Fracture connectivity.

c. Depth‐discrete hydraulic head and conductivity.

d. Pumping tests.

e. Analytical data collected to date (all media), including depth‐discrete rock porewater data, concentrations in wells and piezometers over time, hydrogeochemical data, seep data, and soil vapor data.

f. Bench‐scale tests.

g. Monitored natural attenuation data.

3. Models:

a. SSFL groundwater flow and contaminant transport models.

b. Vapor intrusion screening levels (developed based on DTSC, 2011b – see Appendix A).

c. Mann‐Kendall (or similar) plume stability evaluation (see Table 10)

1. Documents:



c. DTSC comments and response to DTSC comments on the RFI reports.


2. Field data:

a. Characterization data for all media (soil, sediment, vadose zone, surface water, and seeps).

b. Characterization data for offsite wells.


4. Beneficial uses of groundwater.

1. Documents:

a. Treatability study work plans:

- Chemical oxidation.

- Enhanced biological reduction.

- Thermal treatment.

2. Field data:

a. Extent of impacts in groundwater, vadose zone, surface water, and/or seeps above action levels.3

b. Data to be collected during upcoming treatability study for chemical oxidation:

- Delivery and distribution of oxidant to fractured bedrock.

- Extent of TCE oxidation in rock matrix.

- Magnitude of contaminant concentration reduction in rock matrix.

- Natural oxidant demand of minerals and organics in rock matrix.

3. Lab data:

a. Data to be collected during upcoming treatability studies:

- Enhanced biological reduction: effect of biostimulation on rate of TCE reduction.

- Thermal treatment: magnitude of diffusion caused by heating saturated bedrock, mass balance for VOC removal/reduction mechanisms during heating.


1. Extent of groundwater plumes at SSFL.



2. Dates of chemical use, storage, and disposal within CUAs.

3. Chemical and groundwater elevation data from each monitoring location are used to evaluate the nature and extent of chemicals with respect to plume boundaries and plume stability.

1. Extent of groundwater plumes, areas downgradient of groundwater plumes, and vadose zone above groundwater plumes at SSFL.


1. Extent of groundwater plumes, areas downgradient of groundwater plumes, and vadose zone above groundwater plumes at SSFL.

2. The following temporal limits apply to groundwater data used for comparison against action levelsc and/or risk assessment:

a. For each chemical and for each well or piezometer, use data from the last 3 years of available data unless more recent data are judged to be more representative.



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Step 5: Analytical Approach/Decision Rules

1. If all sources and chemicals in groundwater have been sufficiently identified within CUAs, then confirm that sources and chemicals are clearly identified in RFI documentation; else complete documentation for all potential sources and chemicals identified through the Figure 2 process.


1. If existing groundwater data characterize the nature and extent of chemicals to GCLs, then confirm that nature and extent are clearly defined in RFI documentation; else collect groundwater samples from new or existing monitoring wells following approved SOPs and the sampling strategy presented in Table 10.

2. If the lateral and vertical directions of groundwater flow can be reasonably predicted, then the migration pathways of groundwater plumes can be located, and monitored; else identify a data gap and evaluate a new monitoring well location to address characterization of the potential migration pathway.


The plume stability evaluation will first be conducted as described in Table 10, prior to addressing the following:

1. Plume Stability.

a. Plume front stability. If a well(s) at the plume front maintains stable or decreasing chemical concentrations near or below the GCL,b then the downgradient edge of the plume is considered stable; else the plume is considered unstable and additional data should be collected to evaluate the plume’s downgradient extent and stability.

b. Further evaluation of plume stability using professional judgment. In addition to the above primary criteria, evaluate data on a site‐specific basis using professional judgment and multiple lines of evidence to perform focused plume extent and stability evaluations, including consideration of chemical concentrations at the plume mid‐point and screened in the lower portion of the plume, in areas where results add to the lines of evidence to support the DQO SQs #3 and #4 results. Based on professional judgment and in consultation with DTSC, collection of additional data will be considered as required to evaluate plume stability.

2. Natural Attenuation. If biodegradation, chemical reduction, and/or dispersion are occurring at rates substantially different than what is defined in the site conceptual model, then revise the site conceptual model to incorporate the rates of these attenuation processes; else the site conceptual model will remain as currently defined.

3. Indoor and Outdoor Air Quality. If chemical concentrations in shallow groundwater exceed groundwater‐to‐indoor air screening levels developed using the DTSC (2011) methodology (see Appendix A), then assess the need to collect soil vapor samples from the vadose zone above the groundwater plume to evaluate groundwater as a source of VOCs to the vadose zone (soil vapor sample collection is constrained by subsurface refusal by a direct push rig); else the groundwater plume is not expected to be a source of VOCs to the vadose zone. Soil vapor samples, if determined to be necessary, will be collected in accordance with Tables 7 and 8. Soil vapor samples will be collected above select groundwater plumes to develop empirical relationships between shallow groundwater and soil vapor concentrations for different lithologic units (combinations of alluvium, weathered bedrock, and bedrock). These empirical relationships may support development of groundwater‐to‐indoor air action levels.


1. If chemical concentrations in groundwater are above action levels and/or present significant risk to groundwater receptors (indoor air, seeps, or offsite wells), then recommend groundwater plume for remedial planning; else recommend for CNFA.

2. Continue to SQ #5 if groundwater plume is recommended for remedial planning.

1. If existing data are sufficient for remedial planningd

and estimation of the volume of groundwater with chemical concentrations that exceed action levelsc within an order of magnitude, then confirm data are clearly reported in RFI documentation; else collect data to support remedial planning and volume estimation.

2. If chemicals in groundwater or seeps pose an imminent threat to receptors and/or chemical migration may be controlled through the use of best management practices, then evaluate the need to perform interim actions; else do not perform this evaluation

3. Data collection requirements may include:

a. Aquifer and geologic unit properties.

b. Contaminant fate‐and‐transport including distribution and transport of contaminants in matrix and fractures.

c. Water balance.

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1. Compile and document lines of evidence listed in Figure 2 that demonstrate sources and chemicals within CUAs have been sufficiently identified to proceed with investigation and satisfy the final source identification objectives of the RFI.


1. GCLs.b

2. Confirm that characterization samples were analyzed by an accepted USEPA method with MRLs below characterization levels. If MRLs are above characterization levels, perform a sensitivity analysis of reporting limits to determine the need for re‐sampling.

Return to

SQ #2 following collection of additional data, if applicable.

3. Verify that data used to evaluate nature and extent of chemical distributions are representative of existing and future conditions or are usable for risk management decisions.

4. Verify that new analytical data reported by the laboratory have been validated to assess usability to ensure that data quality indicators (precision, accuracy, representativeness, completeness, comparability, and sensitivity) are met and to determine if the collected data can be used to help answer SQ #2. Verify that appropriate field procedures were followed, that deviations were documented and assessed, that data met required characterization levels, and that data are usable for project needs.

Uncertainties include the spatial or temporal variability of the samples, heterogeneity and anisotropy within the subsurface, and attenuation and migration of the contaminants.

1. GCLs.b

2. Groundwater‐to‐indoor air screening levels developed using the DTSC (2011) methodology (see Appendix A).

3. Use only the data determined to be useable under SQ #2.

An uncertainty includes the aquifer properties assumed during groundwater fate‐and‐transport modeling (for example, aquifer thickness and hydraulic conductivity) and heterogeneity and anisotropy within the subsurface.

1. Action levels.c



1. Action levels.c

2. Verify that collected data support estimation of volume of groundwater with chemical concentrations that exceed action levels3 within a tolerance of +50% or ‐30%.

3. Verify that all data and information required for groundwater remedial planning have been collected and documented.

Uncertainties include the volume of groundwater with chemical concentrations that exceed action levels and the efficacy of specific treatment technologies to address various combinations of chemicals and lithologies.


1. Develop a plan to obtain the data gap information required to be collected so that the weight‐of‐evidence documentation is complete and all sources and chemicals identified.

1. Determine which data are usable for evaluating nature and extent of contamination to GCLs

b and for evaluating the lateral and vertical directions of groundwater plume flow.

2. Do not collect additional samples if nature and extent of chemicals in groundwater and direction of groundwater plume flow are adequately evalauted based on existing data.

3. If nature and extent are not adequately defined based on existing data, prepare a SAP to define how and where additional groundwater samples will be collected to address nature and extent data gaps and/or to better define lateral and vertical directions of groundwater plume flow. Sample collection will follow established SOPs and Table 10.

1. Perform plume scale modeling using site‐specific data to support fate‐and‐transport assessment.

2. Collect additional data, if determined to be necessary during fate‐and‐transport assessment.

3. Fate‐and‐transport assessment results will be considered during the cleanup assessment (SQ #4).

1. Recommend remedial planning if chemicals exceed action levels.c


c

1. Collect data to determine if the potential volume for groundwater cleanup of chemicals concentrations exceeds action levels.

c

2. Collect all data and information required for groundwater remedial planning.

a Tables 3, 5, and 7 provide the DQOs for surface water bodies, soil and sediment, and the vadose zone, respectively. b GCLs will be subject to final regulatory agreements. Currently, the basis for GCLs is described in Section 5.1.4.3 of this Comprehensive DQO Report. To evaluate indoor air quality risks via volatilization from a groundwater plume, the current GCLs are expected to be adequate; this will be confirmed through soil vapor sampling to be performed above known groundwater plumes (SQ #3). c It is expected that action levels will be developed in the future based on the COCA (DTSC, 2007). d Remedial planning may contain a mitigation component. The DTSC Mitigation Advisory states that if it is shown that vapor migration is occurring and presents unacceptable risks, mitigation is required. Mitigation could include, but is not limited to fences, vapor barriers, passive venting systems.

TCE = trichloroethene

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TABLE 10 Groundwater and Seeps Characterization Sampling Strategy Comprehensive Data Quality Objectives Technical Memorandum, Santa Susana Field Laboratory, Ventura County, California

Media Criteria Step‐Out and Step‐Down Sampling and Analysis Strategy

Seeps (Input from Table 9, SQ #2).

Groundwater samples are collected from multiple depths if site‐related chemical concentrations are detected in a seep sample and/or if supported by the SSFL groundwater flow model and geochemistry results.

1. Nested wells or piezometers will be installed with short screens at multiple depth intervals near the location where chemical concentrations are detected in a seep sample. Discrete groundwater samples will be collected from each well screen depth interval to evaluate groundwater impacts to seeps, as well as to evaluate groundwater flow patterns.

2. Based on professional judgment and in consultation with DTSC, collection of additional data will be considered as required to evaluate seeps.


Groundwater (Input from Table 9, SQ #2).

Groundwater samples are collected if chemical concentrations in soil or soil vapor indicate a potential impact to groundwater. Additional groundwater samples are collected if the nature and extent of chemical concentrations in groundwater exceed required characterization levels.

1. Groundwater samples will be collected near the top of the water table at locations of known DNAPL releases (that is, rocket engine or rocket engine equipment testing locations) or as specified by DTSC based on professional judgment. Groundwater sample types will depend on the specific lithology from which the groundwater sample is collected and may include grab groundwater samples, rock core pore water samples, or groundwater samples withdrawn from a temporary well.

2. Additional groundwater monitoring wells will be installed downgradient of areas with vadose zone contamination where:

a. Concentrations of chemicals in the vadose zone exceed GCLs.

b. Existing monitoring wells do not intercept groundwater sourced from the CUA cluster.

3. Additional groundwater monitoring wells will be installed to define the extent of a chemical plume at locations where the following criteria are met:

a. The chemical plume is increasing laterally or vertically (or it cannot be demonstrated that the plume is stable). The plume stability evaluation will be conducted using a Mann‐Kendall statistical trend evaluation (or similar trend analysis) using all available data, and

b. The plume is not bounded by existing wells with concentrations below the GCLs (lateral and vertical extents) as estimated using flow directions from the SSFL three‐dimensional groundwater flow model coupled with path length analysis from the three‐dimensional flow model and two‐dimensional discrete fracture network transport model.

Additional wells beyond those that satisfy the criteria above will also be assessed based on a multiple lines of evidence approach, professional judgment, and consultation with DTSC.

4. Groundwater samples will be collected from new or existing monitoring wells to define the extent of chemical concentrations at or near the required characterization levels.


a The basis for GCLs are described in Section 5.1.4.2 of this comprehensive DQO report.

Figures

Group 10(791 acres)

Group 1a(491 acres)

Group 1b(300 acres)

Group 2(285 acres)

Group 5(232 acres)

Group 3(187 acres)

Group 9(178 acres)

Group 4(140 acres)

Group 8(108 acres)

Group 6(86 acres)

Group 7-N(43 acres)

Group 7-S

UNDEVELOPED LAND

AREA IAREA II

AREA IV

AREA III

UNDEVELOPED LAND

UNDEVELOPED LAND

NASA

IL

CA

CN

SR

OC

CTL-III

LF

HVS

B1

BL

ELV

DA

Alfa

FS

AF

STL-IV

Bravo

Bowl Area

CTL-V

B9

LOX

RM

SPA

BS

NC A1

B204

Area I Burn Pit

PDU

Silvernale

L4

ES

PL

ECL

B100

DOE Leachfield 3

RIHL

Area II Landfill

B13

Compound A

Boeing LF

CDFF

EEL

DOE LF 1

Pond Dredge

ABFF

HVN

HWSA

Perimeter Pond

SNAP

R-1 Pond

B515 STP

R-2A and R2B Ponds

B29

B211 Leach Field

STP-3

Ash Pile

DOE LF 2 Alfa Bravo Skim Pond

SE Drum

HWCT

HMSA

B213 Leach FieldMetals

Clarifier

B212 Leach Field

B217 Leach Field

SPA 1 ImpoundmentB208

Leach Field

Coca

UT-52

UST-51

UT-53

I1 inch = 1,200 feet

FIGURE1

SSFL Administrative Boundaries

SCO \\GALT\PROJ\BOEING\362070\MAPFILES\2013\AOC_BOUNDARY.MXD RANHORN 3/7/2013 2:40:46 PM

Basemap Legend

DOE AOC Boundary

NASA AOC Boundary

RFI Group Boundary

Administrative Area

Ponds

RFI Site - Boeing

RFI Site - DOE

RFI Site - NASA

Surface Drainage Divide

Paved Road

Dirt Road

Unpaved trail0 600 1,200 1,800

Feet

SCO362070.TM.11.SW.BO Boeing_source_area_decision_tree_rev9.vsd 3/13

Question 1:Was a release or

potential release of any chemical previously used, stored, handled, or

disposed at an area of interest identified during any of the steps

listed above?

Conditional No Further Action (CNFA)Based on all information and data gathered during the steps listed above, no release or potential release of a chemical has been identified. Based on this comprehensive and complete review of all available information, a determination of CNFA is appropriate for the identified area.

Question 2:Is the

area of interest within a chemical use area (CUA) that has previously been

identified?

Question 4:Were chemicals detected

at concentrations that exceed characterization levels in the screening-level sample(s)?

This represents a Potential CUA.Collect screening-level sample(s), as appropriate, at the area of interest to determine if chemicals impacted environmental media. (Follow sampling strategy presented in Table 2).

Perform DQO EvaluationAdditional field investigation may be required for this CUA. Refer to DQO Tables 3, 5, 7, and 9 to evaluate if additional data collection efforts are required to address the data quality objectives for the CUA, for the various media at SSFL.

New CUAThe area of interest represents a new CUA. Add this new CUA to existing CUA maps and inventories, and follow the data quality objective process described above.

Yes

Yes

No

NoNo

Yes

FIGURE 2Chemical Use Area Confirmation and Conditional No Further Action Area Weight of Evidence Documentation for the Surficial Media Operable UnitComprehensive Data Quality Objectives ReportSanta Susana Field Laboratory, Ventura County, California

Question 3:Was a release of any

chemical previously used, stored, handled, or disposed documentedat the area of interest?

Yes

No

As part of the planned demolition of the remaining SSFL buildings, sampling will be performed, as needed, according to the process specified in the Building Feature Evaluation and Sampling Standard Operating Procedure (MWH and CH2M HILL, 2009), to assess the potential for chemical impacts beneath the buildings. The CNFA recommendation for each applicable area will be re-evaluated based on the data collected following building demolition. In addition, CNFA recommendations will be re-evaluated if chemical background concentrations or method reporting limits change in the future and pending final regulatory requirements established when SB990 applicability is resolved.

Conditional No Further Action (CNFA)Based on all information and data gathered during the steps listed above and screening-level sample analytical data, no release or potential release of a chemical has been identified above characterization levels. Based on this comprehensive and complete review of all available information, a determination of CNFA is appropriate for the identified area.

Assess if a release or potential release of any chemical previously used, stored, handled or disposed within the RFI Reporting Area was identified during any of the following activities.

RCRA Facitity Assessment (1989 - 1994) RFI Program Report (2004)Boeing RFI Reports (2008-2009)Site-Wide Groundwater RI Report (2009)Review of historical documentation

Building Inventory and Feature SurveyTank InventorySewer System SurveyReclaimed water system inventoryPipelines Wrapped with Mastic Tape DocumentationPrimary Fuel Oil and Chemical Pipeline inventoryGIS Gold Copy data management tool

Debris Survey and SamplingBiological Survey and MappingAerial Photograph Review

Topography and Physical AccessibilityProximity to roadways and operationsGeophysical SurveyDemolition Documentation and SamplingInterim Remedial Actions

Vapor Intrusion Pathway EvaluationAir Deposition ModelingVadose Zone Mass Flux to Groundwater ModelingSurface water drainage documentationNPDES surface water dataSeeps and Springs dataAnalytical data collected for purposes other than the RFI

Method 1: Document and Record Review

Method 2: SSFL Site-wide Inventories

Method 3: SSFL Site-wide Comprehensive Inspections and documentation

Method 4: RFI Site specific inspections and documentation

Method 5: Chemical Migration Assessment

ES120210023632SCO362070.TM.11.SW.BO SSFL_Data Quality Objectives Process_ACTIVE.ai 12/12

FIGURE 3 Data Quality Objectives ProcessComprehensive Data Quality Objectives ReportSanta Susana Field Laboratory, Ventura County, CA

Step 6. Specify Performance or Acceptance Criteria

Step 7. Develop the Plan for Obtaining Data Select the resource-effective sampling and analysis plan

that meets the performance criteria

Step 1. State the Problem.Define the problem that necessitates the study;

identify the planning team, examine budget, schedule

Step 2. Identify the Goal of the Study.State how environmental data will be used in meeting objectives and

solving the problem, identify study questions, define alternative outcomes

Step 3. Identify Information Inputs. Identify data & information needed to answer study questions.

Step 4. Define the Boundaries of the StudySpecify the target population & characteristics of interest,

define spatial & temporal limits, scale of inference

Step 5. Develop the Analytic Approach. Define the parameter of interest, specify the type of inference,

and develop the logic for drawing conclusions from findings

Decision making(hypothesis testing)

Specify probability limits for false rejection and false

acceptance decision errors

Develop performance criteria for new data being collected or acceptable criteria for existing data being considered for use

Estimation and other analytic approaches

Source: USEPA, Guidance on Systematic Planning Using the Data Quality Objectives Process, February 2006

ES120210023632SCO362070.TM.11.SW.BO SSFL_Iteration of the DQO Process_ACTIVE.ai 12/12

FIGURE 4 Iteration of the DQO Process through the Project Life CycleComprehensive Data Quality Objectives ReportSanta Susana Field Laboratory, Ventura County, CA

Source: USEPA, Guidance on Systematic Planning Using the Data Quality Objectives Process, February 2006

ITERATEAS

NEEDED

STARTTHE

DQO PROCESS

PRIM ARYSTUDY

DECISION

STATE THE

PROBLEM

IDENTIFY GOALS OF THE STUDY

DEVELOP THE

ANALYTIC APPROACH

DEFINE THE

BOUNDARIES OF THE STUD Y

IDENTIFY INFORMATION

INPUTS

STATE THE

PROBLEM

DEVELOP DETAILED PLAN

FOR OBTAINING

DATA

IDENTIFY GOALS OF THE STUDY

DEVELOP THE ANALYTIC APPROACH

DEFINE THE

BOUNDARIES OF THE STUDY


INPUTS

STATE THE

PROBLEM

IDENTIFY GOALS OF

THE STUDY

DEVELOP THE

ANALYTIC APPROACH

DEFINE THE

BOUNDARIES OF THE STUDY

STUDY PLANNINGCOM PLETED



INTERM E-DIATESTUDY

DECISIONADVANCED

STUDYDECISION

DECIDENOT

TO USEPROBABILISTIC

SAM PLINGAPPROACH

SPECIFY PERFORMANCE

OR ACCEPTANCE CRITERIA SPECIFY

PERFORMANCE OR

ACCEPTANCE CRITERIA SPECIFY

PERFORMANCE OR

ACCEPTANCE CRITERIA

DEVELOP DETAILED PLAN

FOR OBTAINING

DATA DEVELOP DETAILED PLAN

FOR OBTAINING

DATA


INPUTS

INCREASING LEVEL OF EFFORT

Property Description Terminology Referenced Under the RFI Reporting Process

SSFL RFI Subarea

Figure 2 – CUA Confirmation and CNFA

Weight of Evidence Documentation

Information Compilations Organized by

Expanded RFI Site Boundary

SSFL RFI CUAs and Chemicals for Each

Recommended CMS Remedial Planning Areas

Recommended CNFA Areas

Potential CUA Identified?

Provide the Documentation for

CNFA

Define CUA Clusters, Satisfy Media-Specific

DQOs

Yes

No

Table 5 – Soil and Sediment

Table 7 - Vadose Zone

Table 3 - Surface Water Bodies

Table 9 – Groundwater and Seeps

Potential unacceptable

risk?

CNFA

CMS Remedial Planning Process

SCO362070.TM.11.SW.BO Boeing_Process_Flow_ACTIVE.vsd 12/12

Data Quality Objectives Flowchart

Note: This is an iterative process, and may feed back to previous steps.

Notes:CMS = Corrective Measure StudyCUA = Chemical Use AreaDQO = Data Quality ObjectiveCNFA = Conditional No Further ActionRFI = RCRA Facility InvestigationSSFL = Santa Susana Field Laboratory

Yes

No

FIGURE 5Comprehensive Data Quality Objectives FlowchartComprehensive Data Quality Objectives ReportSanta Susana Field Laboratory, Ventura County, CA

SSFL RFI CUA Clusters and

Chemicals for Each

(For those portions of each RFI Subarea with initial CNFA weight-of-evidence documentation)

ES120210023632RDD.SCO362070.TM.11.SW.BO Boeing_CUA_scale_ACTIVE.ai 12/12

FIGURE 6CUA and CUA Cluster Scale Site Conceptual ModelComprehensive Data Quality Objectives ReportSanta Susana Field Laboratory, Ventura County, CA

Indoor Air Quality

Vadose zone mass flux to indoor air

Vadose zone mass flux to burrowing ecological receptors

Surface water mass flux to vadose zone and groundwater

Surface water mass flux to groundwater

Groundwater mass flux to

surface water

Vadose zone mass flux to groundwater

VOCs in groundwater volatilization to surface

Soil exposures via dermal, ingestion, and/or inhalation pathways

Burrowing ecological receptor

Ecological receptors

Surface water drainage pathway

Uptake into plants

Pond

Sediment

Surface water and sediment exposures via dermal and ingestion pathways

Note: CUA = Chemical use area

Alluvium

Weathered Bedrock

Bedrock

Groundwater Plume

ES120210023632RDD.SCO362070.TM.11.SW.BO Boeing_Plume_scale_ACTIVE.ai 12/12

FIGURE 7Deep Soil and Groundwater Plume ScaleSite Conceptual ModelComprehensive Data Quality Objectives ReportSanta Susana Field Laboratory, Ventura County, CA

Indoor Air Quality

CUA Cluster

Shallowdowngradient

well (e.g.,500 µg/L TCE)

Intermediate down-gradient well (e.g.,

100 µg/L TCE)

Deep downgradient well

(<5 µg/L TCE)

Intermediate downgradient well

(<5 µg/L TCE)

Deepdowngradient well(<5 µg/L TCE)

Shallowdowngradient well

(>5 µg/L TCE)

Shallowdowngradient well

(<5 µg/L TCE)

Seep

Off-site well

Note: TCE concentrations are used for example only.

Upgradient well (ND for TCE)

Vadose zone

mass flux to indoor

air

Vadose zone mass flux to ground-water

VOCs in Groundwater Volatilization

to Surface

Groundwater Plume

Bedrock

AlluviumWeathered

bedrock

“SSFL” or “On-site” Off-site

ES120210023632RDD.SCO362070.TM.11.SW.BO SSFL_Facility_scale_ACTIVE.ai 12/12

FIGURE 8SSFL Site-Wide Facility ScaleSite Conceptual ModelComprehensive Data Quality Objectives ReportSanta Susana Field Laboratory, Ventura County, CA

Note: CUA = Chemical use area

Vadose zone mass flux to groundwater

VOCs in groundwater volatilization to surface

Vadose zone mass flux to

indoor airSeepsSeeps

Surface water flow

Bedrock outcrops

Off-site well

Off-site well

CUA Cluster

SSFL

Faults

Alluvium

Alluvium Weathered Bedrock

Bedrock

Shale Layers

Ubiquitous interconnected

fractures

ES120210023632RDD.SCO362070.TM.11.SW.BO SSFL_Historical_Document_Review_Process_rev.ai 11/12

FIGURE 9SSFL Historical Document Review ProcessComprehensive Data Quality Objectives ReportSanta Susana Field Laboratory, Ventura County, CA

Boeing 2007 Starting Input: Key Source Documents● Key historical documents (RFA, CCR, WPs, IMs, etc.)● Aerial Photographs● Inventories● Known Facility Diagrams

Boeing 2008/2009 Output: Preliminary RFI Report Components● RFI Site History● Base Map & Chemical Use Areas (CUAs)● Inventories (tanks, buildings, transformers, etc.)● Preliminary Report Reference List● Site conceptual model

Thorough Historical Document Review● Technical staff trained for document review conduct with senior oversight for QC● All documents manually screened for relevance● Focused, manual review of all relevant documents by assigned RFI Group

Technical Staff● Information on site operations and potential chemical use compiled into DQO

tabulated documentation, as appropriate

Verification: Based on knowledge gained, site manager conducts site walk/building feature documentation review, including aerial photo field check, site personnel interviews, delineation of drainage features, etc. to verify new information (as possible) and also review all RFI Site information and existing chemical data to verify identification of potentially new RFI-relevant information. Revise DQO information compilations, as appropriate.

Output: Go to Comprehensive DQO Report Figure 2, Question 1

Sort and Assign Database by RFI Group for Technical Review* (All SSFL relevant documents potentially containing chemical and/or operation use information; examples include):● Correspondence● Reports● Aerial and oblique photographs

Thorough Review: Source Documents

● Maps/facility drawings● Depositions● Waste Manifests

● Spill Records● Inventories● Notes

Revise RFI Document Group

Assignment(s)

Document relevant to more than one RFI

Group?

Document correctly assigned to all

relevant RFI Groups?

Identification of Potentially New RFI-Relevant

Information? (release or potential release of any chemical

previously used, stored, handled, or disposed at an area of interest

identified during historic document review)

Yes

Yes

Yes

No

No

No

* Repeated to capture new documents added to HDMS at important milestones: 2008/2009 RFI report submittal, Master RFI Data Gap Work Plan Addenda preparation, Data Summary and Findings Report preparation.

ES120210023632RDD.SCO362070.TM.11.SW.BO SSFL_DQO_Report_rev1.ai 11/12

FIGURE 10Analytical Approach/Decision Rules for Vadose Zone Mass Flux of Contaminants to Groundwater EvaluationComprehensive Data Quality Objectives ReportSanta Susana Field Laboratory, Ventura County, CA

CUACluster

within known rocketengine or equipment

testing DNAPLrelease?

Are concentrations

>BTVs or GCLs?

DTSC professional judgement

requires deep boring?

Monitoringwell alongflow pathnearby?

Recent groundwater

sampling results available

(within last3 years)?

Groundwater concentrations for soil, soil vapor, or rock constituents

listed>GCLs?

Model predicts leachate at water

table > GCLs within next 50 years?

No

No

No

No

No

No

No

No

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Compare available soil, soil vapor and rock core chemical sampling results to background threshold values (BTVs) or groundwater characterization levels (GCLs)1

List chemicals in soil, soil vapor, and rock core with concentrations > BTVs or GCLs

Drill deep boring & analyze vadose zone & groundwater samples

Install well

Collect and analyze samples

Evaluate vadose zone in corrective measures study for groundwater protection

Model future transport of constituents in vadose zone to groundwater2

Conditional no further action for vadose zone mass flux to groundwater

Deep boring results

available?

1. See Section 5.3.2 of Data Quality Objectives Report for Definition of Groundwater Characterization Levels (GCLs).

2. In Accordance with the Recommended Approach for Existing Vadose Zone Mass Flux of Contaminants to Groundwater Technical Memorandum included as Appendix D to the Comprehensive DQO Report.

Appendix A Recommended Approach for Assessing the

Vapor Intrusion Pathway

APPENDIX A_COMPREHENSIVE DQOS_BOEING SSFL RFI_UPDATED VI ASSESSMENT APPROACH_13 NOVEMBER 2012.DOCX 1

T E C H N I C A L M E M O R A N D U M Recommended Approach for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California PREPARED FOR: The Boeing Company

PREPARED BY: CH2M HILL

DATE: March 8, 2013

1.0 Introduction and Purpose This technical memorandum (TM) presents the recommended approach to assess vapor intrusion (VI) for The Boeing Company (Boeing) Resource Conservation and Recovery Act (RCRA) facility investigation (RFI) project at the Santa Susana Field Laboratory (SSFL). The approach documented in this TM is consistent with the California Environmental Protection Agency (Cal/EPA), Department of Toxic Substances Control (DTSC) Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air (VI guidance) (DTSC, 2011a). The updated approach provides the basis for evaluating VI issues for the Boeing RFI data gap site characterization and supports the Comprehensive SSFL Data Quality Objectives, RCRA Facility Investigation, Santa Susana Field Laboratory, Ventura County, California (DQO Report) (CH2M HILL, 2013a).

The proposed VI assessment approach for the Boeing SSFL RFI project begins with development of the appropriate characterization screening levels and a review of historical documentation and existing data to confirm that all volatile organic compound (VOC) spills and releases have been identified. The existing soil gas and groundwater quality data will be compared against appropriate DTSC‐approved characterization screening levels to assess whether the data are sufficient to evaluate the nature and extent and fate and transport of impacts for assessment of the VI pathway. Additional soil gas data will be collected where required to complete characterization of the nature and extent and fate and transport of impacts from source areas and to support remedial planning. The areas at Boeing SSFL where the VI pathway might be complete will be spatially delineated by considering the known or suspected vapor sources, the nature and extent of impacts, and the fate and transport of VOC constituents. In this manner, the VI assessment approach is consistent with the comprehensive data quality objectives (DQO) evaluation. This approach provides a systematic and defensible process for completing the VI assessment portion of the RFI to identify areas where the VI pathway could be (or is not) complete and significant and for preparing documentation in support of corrective measures studies (CMS) and conditional no further action (CNFA) recommendations.

2.0 Regulatory Framework for VI Evaluation The Boeing RCRA activities at the SSFL are being conducted under the oversight and jurisdiction of the DTSC. The DTSC (2011a) VI guidance recommends a “multiple lines of evidence” approach for evaluating VI into buildings and its subsequent impact on indoor air. The intent of the VI guidance is to help stakeholders understand and evaluate the VI exposure pathway. Although the VI guidance states that its use is optional because other technically sound approaches may be available, this updated VI assessment approach incorporates the VI guidance to the extent practical to support the Boeing SSFL RFI, as further described in Section 4 of this TM.

The DTSC (2011a) VI guidance presents an 11‐step approach in which Steps 1 through 11 apply to sites with existing buildings, as shown in Table A‐1 of this TM. Steps 1, 2, 3, 5, 6, 7, and 11 apply to sites (or portions of sites) where no buildings exist but buildings may potentially be built in the future. For the Boeing SSFL site, it is anticipated that ongoing site closure activities and preparation for open space preservation will result in the demolition of most existing structures. A limited number of new buildings might be constructed in the future in support of the open space future land use plan. As a result, Steps 1, 2, 3, 5, 6, 7, and 11 from the VI guidance

RECOMMENDED APPROACH FOR ASSESSING THE VAPOR INTRUSION PATHWAY, BOEING RCRA FACILITY INVESTIGATION PROJECT, SANTA SUSANA FIELD LABORATORY, VENTURA COUNTY, CALIFORNIA

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(which apply to sites where buildings might be built in the future), are the steps primarily relevant to the Boeing SSFL RFI project. In addition, Steps 4, 8, 9, and 10 from the VI guidance will be reviewed and implemented, if warranted, for any existing buildings not slated for demolition. The VI guidance steps and their potential applicability to the Boeing SSFL RFI are presented in Table A‐1.

TABLE A‐1 DTSC Stepwise Vapor Intrusion Assessment – List of Steps and Applicability to Existing and Future BuildingsUpdated Approach for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

VI Assessment 11‐step Process Sites with Existing Buildings

a or Sites where Buildings might be Built?

Step 1: Site History and Identification of Spills and/or Releases Both

Step 2: Site Characterization Both

Step 3: Evaluate Whether the Exposure Pathway is Complete Both

Step 4: Evaluation of an Acute Hazard in an Existing Building Existing

Step 5: Preliminary Screening Evaluation Both

Step 6: Additional Site Characterization Both

Step 7: Site‐specific Screening Evaluation Both

Step 8: Building Survey and Work Plan Development Existing

Step 9: Indoor Air Sampling Existing

Step 10: Evaluation of Indoor Air Sampling Results and Response Actions Existing

Step 11: Mitigate Indoor Air Exposures, Monitoring, and Implementation of Engineering Controls Both

Notes: a For the Boeing SSFL RFI, an “existing” building is assumed to be one not slated for demolition.

Source: DTSC, 2011a.

Other DTSC initiatives related to VI assessments are described in the VI guidance and are potentially pertinent to the Boeing SSFL RFI project. In January 2005, the Cal/EPA Office of Environmental Health Hazard Assessment (OEHHA) established California human health screening levels (CHHSLs) for soil gas and indoor air (OEHHA, 2005) and updated the CHHSLs on September 23, 2010 (OEHHA, 2010). These CHHSLs are appropriate for use as characterization levels for soil gas. The presence of a chemical in soil gas or indoor air at concentrations below the corresponding CHHSL can be assumed not to pose a significant health risk to people who hypothetically may live at the site (residential CHHSLs) or work at the site (commercial/industrial CHHSLs).

As described in the VI guidance, DTSC has updated the attenuation factors used to calculate concentrations in soil gas that are considered protective of human health. These updated attenuation factors also can be used to calculate protective concentrations in groundwater.

In October 2011, DTSC issued the revised VI mitigation advisory (DTSC, 2011b), which will be considered with respect to the Boeing SSFL CMS, as appropriate. In April 2012, DTSC issued the Advisory ‐ Active Soil Gas Investigations (DTSC, 2012). This advisory will be reviewed for potential applicability to soil gas sampling performed in support of the Boeing SSFL RFI project.

The United States Environmental Protection Agency (USEPA) VI‐related activities are also monitored for possible relevance and application to the ongoing Boeing VI evaluation at SSFL. USEPA issued a white paper in August 2010 titled “Review of the Draft 2002 Subsurface Vapor Intrusion Guidance (USEPA, 2002),” which summarizes the anticipated changes to the 2002 draft guidance (USEPA, 2010). USEPA is currently preparing the final VI guidance. When issued, this guidance will be reviewed for potential applicability to the Boeing SSFL RFI project.


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3.0 Prior VI Activities for the Boeing SSFL RFI Project The VI pathway at SSFL has been evaluated by Boeing as part of the RFI project. A significant amount of characterization data—consisting of soil, soil gas, and groundwater data—have been collected from the Boeing RFI subareas. Building feature documentation logs have been prepared to capture potentially relevant RFI‐related information for all existing buildings. The VI pathway evaluation was initiated by Boeing prior to the decision to fully close and decommission the SSFL. Consequently, the initial focus was on evaluating potential impacts to indoor air at existing buildings.

The Standardized Risk Assessment Methodology Work Plan, Revision 2 Report, Santa Susana Field Laboratory, Ventura County (SRAM Rev. 2) (MWH International, Inc. [MWH], 2005) was prepared to establish a framework for conducting risk assessment activities at SSFL, including assessing the potential risk from VI. Appendix G of the SRAM Rev. 2 presents proposed methods for estimating subsurface to indoor air exposure concentrations. The primary steps involved in this evaluation were as follows:

The measured soil vapor data from source area units and default/site‐specific parameters were proposed as inputs to the Johnson and Ettinger VI model for estimating indoor air levels.

A modified Johnson and Ettinger model, termed the “groundwater bedrock model,” was proposed for use where contaminated groundwater has migrated from source areas.

DTSC comments to the SRAM Rev. 2 stated that the groundwater bedrock model had not been validated, and DTSC requested field validation data be obtained. DTSC participated in multiple discussions with Boeing during development of the scope of work to obtain the validation data, expressing concerns about the effective diffusivity through bedrock and whether it would adequately represent site conditions. As a result of the DTSC comments and ensuing discussions, the SSFL groundwater bedrock model validation study was conducted in 2006 and was presented in the Vapor Migration Model Validation Study Report, Santa Susana Field Laboratory, Ventura County (Validation Report) (MWH, 2007).

DTSC comments on the Validation Report, received in March 2010, stated that insufficient data have been collected to successfully validate the groundwater bedrock model and that the model could not be approved for risk assessment purposes. Subsequent DTSC comments to draft RFI reports stated that follow‐up documents should consider an updated or alternative approach for VI risk modeling and soil vapor characterization. DTSC also commented that soil gas characterization was still needed because the Validation Report was not approved; therefore, modeling of the indoor air VI pathway was considered preliminary.

A VI evaluation approach is proposed by Boeing that supports the planned long‐term land use of open space preservation with a limited number of existing and potential future buildings. Boeing has been actively working with its technical consultants to develop this updated VI evaluation approach that merges the previous work and DTSC comments with the new DTSC guidance, current VI evaluation methodologies, an updated soil gas sampling standard operating procedure (SOP), and the comprehensive DQO evaluation process (CH2M HILL, 2013a) to identify and address all remaining RFI data gaps. The comprehensive DQO process provides a systematic means for evaluating not only the nature and extent but also the fate and transport of contaminants from source areas to potential receptors and for preparing documentation to support CMS and CNFA recommendations. The proposed VI evaluation approach is described in Section 4 of this TM.

4.0 Proposed VI Evaluation Approach Based on the comprehensive DQO evaluation process, the updated VI Guidance (DTSC, 2011a), the RFI work performed to date, and DTSC comments as discussed in Section 3 of this TM, the actions outlined in this section are proposed to further evaluate the VI pathway at SSFL under the Boeing RFI project. The proposed approach for the VI assessment is linked to the appropriate portions of the comprehensive DQO Report (CH2M HILL, 2013a) that pertain to potential VI and indoor air quality concerns. Specifically, the VI evaluation procedures are included in the DQOs and characterization sampling strategy for the vadose zone (DQO Report Tables 7 and 8) and for


4

groundwater (DQO Report Tables 9 and 10). For the vadose zone and groundwater, DQOs were developed for five sequential study questions. The five DQO Report study questions are related to:

Identification of sources and chemicals (DQO Report Study Question [SQ] #1).

Nature and extent (DQO Report SQ #2).

Fate and transport (DQO Report SQ #3).

CNFA or cleanup assessment (DQO Report SQ #4).

Remedial planning (DQO Report SQ #5).

The proposed VI assessment approach includes sufficient characterization to address these RFI DQO study questions and to prepare documentation in support of CMS or CNFA recommendations. The primary elements of the VI assessment approach are presented in the following subsections.

4.1 Develop RFI VI-related Characterization Screening Levels The initial step in the VI assessment process is to develop the characterization screening levels that will guide this portion of the RFI data gap evaluation process. Characterization levels are proposed in this section for the soil gas investigation to evaluate potential VI impacts and for the shallow groundwater investigation to identify portions of groundwater plumes with potential VI impacts.

As described in Section 2 of this TM, the CHHSLs are appropriate for use as characterization levels for soil gas. The thresholds of concern used to develop the CHHSLs are an excess lifetime cancer risk of 1 in a million (10‐6) and a hazard quotient of 1.0 for noncancer health effects. The presence of a chemical in soil gas or indoor air at concentrations below the corresponding CHHSLs can be assumed to not pose a significant health risk to hypothetical site occupants. Conversely, the presence of a chemical at concentrations in excess of a CHHSL does not indicate that adverse impacts to human health would occur but would suggest that further evaluation is warranted. Cumulative excess lifetime cancer risks or noncancer hazard indices will be evaluated as needed in cases where multiple VOCs have been detected.1 The assessment of cumulative risks from VOCs sampled as part of a VI evaluation will be consistent with the approach presented in the risk assessment methodology technical memorandum, Integration of the Surficial Media Operable Unit Risk Assessment Methodology with the Data Quality Objectives Process, Boeing RCRA Facility Investigation, Santa Susana Field Laboratory, Ventura, California (CH2M HILL, 2013b). Further evaluation could include additional sampling or evaluation of soil gas results if sufficient unconsolidated alluvial material is present, or per DTSC (2011a) VI guidance, collecting or evaluating soil VOC data if soil gas sampling is not feasible. The CHHSLs are intended for use as screening levels only and are not intended to be regulatory cleanup standards or action levels (OEHHA, 2005).

The CHHSLs were developed using standard exposure assumptions and chemical toxicity values published by USEPA and Cal/EPA. As shown in Tables A‐2 and A‐3 (presented at the end of this TM) and as described in Attachment A1 to this TM, the screening levels for indoor air, soil vapor, and groundwater‐to‐indoor air were updated or calculated with the most current toxicity values and the updated default attenuation factors (DTSC, 2011a). The updated screening levels for indoor air will be used for comparison with indoor air concentrations if indoor air sampling in buildings that are not scheduled for demolition is warranted as an outcome of the comprehensive DQO evaluation. Because any existing buildings not slated for demolition are designated for commercial/industrial use, the commercial/industrial indoor air CHHSLs were used as the basis for the indoor air screening levels included in Tables A‐2 and A‐3 of this TM.

To assess potential VI impacts from shallow groundwater, initial delineation of the groundwater plumes will be performed to the characterization levels in groundwater presented in Tables A‐2 and A‐3 at the end of this TM. In cases where calculated groundwater to indoor air screening levels (described below) are lower than method reporting limits (MRL), the MRL will be used as the basis for assessing or delineating VI from VOCs in shallow groundwater. Groundwater to indoor air screening levels were calculated from the soil gas screening levels using equilibrium partitioning with Henry’s Law constants, as described in DTSC’s updated VI guidance (DTSC, 2011a).

1 Characterization levels for carcinogenic effects (Table 2 at the end of this TM) and for noncarcinogenic effects (Table 3 at the end of this TM) have been developed to perform screenings based on cumulative effects as needed.


5

The resulting VOC groundwater to indoor air screening levels are presented in Tables A‐2 and A‐3 at the end of this TM and are described in Attachment A1. For areas in which VOC groundwater plumes are present, the existing shallow groundwater data (near the water table) will be compared with the conservative groundwater to indoor air screening levels developed either using the updated default attenuation factors and equilibrium partitioning with Henry’s Law constants (as presented in Tables A‐2 and A‐3 at the end of this TM). In all cases, the groundwater to indoor air evaluation will be conducted in consideration of the lithology between the shallow groundwater and the surface. If the subsurface lithology suggests there is potential for vapor migration (for example, through fractured bedrock) that is inconsistent with the assumption of transport through porous media inherent in the groundwater to indoor air screening level, then further evaluation might be warranted, as described above.

4.2 Confirm that VOC Sources are Identified: DQO Study Question #1 This activity consists of a review of existing data to confirm that all potential VOC spills and releases have been identified. This step is accomplished by the process presented in DQO Report Figure 2, “Chemical Use Area Confirmation and Conditional No Further Action Area Weight of Evidence Documentation for the Surficial Media Operable Unit” (CH2M HILL, 2013a). This VI evaluation step is also consistent with and completed under DQO Report SQ #1 (from the DQO Report Tables 7 and 9) for the identification of all potential sources within identified chemical use areas. The steps outlined in the DQO Report Figure 2 are ongoing under the current Boeing RFI reporting process and are integral to the data gap identification process. Existing VOC sources, as well as new VOC sources that are identified through this process, will be subject to the subsequent VI assessment activities prescribed in the comprehensive DQO process and as described in the following sections. This activity is consistent with Step 1 from the VI guidance (DTSC, 2011a).

4.3 Evaluate Adequacy of Soil Gas and Groundwater Data and Collect Additional Data as Required to Satisfy DQO Study Questions #2 through #5

The existing soil gas and groundwater data will be reviewed to evaluate whether the nature and extent and fate and transport of subsurface VOC impacts have been adequately characterized (consistent with DQO SQs #2 and #3 from DQO Report Tables 7 and 9). The approach for evaluating soil gas and groundwater data is summarized in Sections 4.3.1. and 4.3.2.

4.3.1 Soil Gas Data Evaluation The adequacy and defensibility of existing soil gas data will be evaluated for assessing the VI pathway, per DQO Report Table 7. Consistent with the VI Guidance (DTSC, 2011a), soil gas sampling data are the preferred data to assess potential VI impacts from potential release (that is, source) areas. Field sampling decision rules for soil gas sampling in the vadose zone are summarized in DQO Report Table 8. The soil gas data will be reviewed in an iterative manner, as follows:

Existing soil gas data will be compared with the soil gas screening levels (described in Section 4.1 and presented in Tables A‐2 and A‐3 of this TM) to evaluate the nature and extent of shallow soil gas impacts in the unconsolidated vadose zone. If delineation to the residential soil gas screening levels has not occurred, additional soil gas characterization in the unconsolidated vadose zone might be needed to satisfy DQO SQ #2 in DQO Report Table 7. Soil gas characterization will be performed in accordance with DQO Report Table 8. Additional soil gas characterization could be needed if MRLs for nondetect results exceed the screening levels (depending on the results of a sensitivity analysis to be performed on MRLs). The existing soil gas data will also be reviewed for representativeness and usefulness on a site‐specific basis, accounting for proximity to contaminant sources (per DTSC, 2011a), the age and extent of the existing data, as well as other considerations including source type, status of cleanup activities, proximity to other sources, local geology, depth to groundwater, possible attenuation, and other related factors.

If existing or newly collected soil gas data indicate that areas with soil gas concentrations above the residential soil gas screening levels are in proximity to existing buildings not slated for demolition, then collection of additional data, including initial subslab samples, might be needed to address the potentially


6

complete VI pathway and satisfy DQO SQ #3 from DQO Report Table 7. In accordance with DQO Report Tables 2 and 8, subslab samples will be collected from beneath those existing buildings not slated for demolition that have documented historical chemical use or that have limited or no information regarding historical chemical use. In general, subslab sampling is conducted where existing buildings (not slated for demolition) are within 100 feet of the plume boundary in groundwater or soil gas with VOC concentrations higher than the characterization levels presented in Tables A‐2 and A‐3 at the end of this TM. The need for concurrent indoor air, outdoor air, and subslab samples at these buildings will be determined following a comparison of initial subslab sampling results to residential soil gas screening levels, accounting for the subslab attenuation factor of 0.05 (DTSC, 2011a).

After acceptance criteria under DQO SQ #2 and/or DQO SQ #3 are satisfied, the data will be reviewed to recommend remedial planning or CNFA in accordance with DQO SQ #4.

If data reviewed under DQO SQs #1 through #4 are insufficient for remedial planning (for example, do not allow for a reasonable estimate of soil vapor volume requiring remediation), then additional data might be needed to satisfy DQO SQ #5.

The outcome of the soil gas data evaluation will allow for delineation of areas where the VI pathway from soil gas impacts is incomplete (that is, where soil gas concentrations are below the residential screening levels) or is potentially complete (that is, where soil gas concentrations are above the residential screening levels and where existing buildings not slated for demolition will remain and/or where buildings might be constructed in the future). The use of the residential soil gas screening levels represents a conservative approach to evaluating potential soil gas impacts to the VI pathway. As needed, Boeing may elect to conduct further evaluation, including a risk assessment specific to the area of interest (for example, RFI site), consistent with the “multiple lines of evidence” approach (DTSC, 2011a) to evaluate whether the VI pathway is potentially complete and significant and to provide additional documentation in support of the RFI recommendations.2

4.3.2 Groundwater Data Evaluation The adequacy and defensibility of existing groundwater data will be evaluated for assessing the VI pathway, per DQO Report Table 9. Consistent with the VI guidance (DTSC, 2011a), impacts to groundwater need to be characterized when assessing the VI pathway, particularly shallow groundwater at or near the water table. The groundwater data will be reviewed for potential contribution to the VI pathway in an iterative manner, as follows:

Shallow groundwater first will be characterized to appropriate characterization levels to satisfy DQO SQ #2 from DQO Report Tables 9 and 10.

For areas in which VOC groundwater plumes are present, the existing shallow groundwater data (near the water table) will be compared with the conservative groundwater to indoor air screening levels developed using the updated default attenuation factors and equilibrium partitioning (presented in Table A‐2 of this TM). The areas where existing groundwater concentrations exceed the groundwater screening levels will be displayed graphically on plan‐view maps to evaluate the nature and extent of soil gas potentially impacted by groundwater to satisfy DQO SQ #3 from DQO Report Table 9. This step could result in the need for additional groundwater data collection in areas where a plume was not sufficiently characterized to evaluate the VI pathway, as prescribed in DQO Report Table 10.

If existing or newly collected groundwater data indicate that a portion of a plume with concentrations above the groundwater screening levels is in proximity (within 100 feet, per DTSC, 2011a) to existing buildings not slated for demolition, then collection of additional data, including initial subslab samples, might be needed to address the potentially complete VI pathway and satisfy DQO SQ #3 from DQO Report Table 8. The need for concurrent indoor air, outdoor air, and subslab samples at these buildings will be determined following a

2 Note that Table 3 also includes low toxicity reference value risk-based screening levels for ecological receptors (MWH, 2011). While unrelated to VI, these values were included in Table 3 of this TM for use in evaluating shallow soil gas data, as appropriate, to evaluate potential exposure pathways to burrowing mammals.


7

comparison of initial subslab sampling results to commercial subslab screening levels, accounting for the subslab attenuation factor of 0.05 (DTSC, 2011a).

After acceptance criteria under DQO SQ #3 from DQO Report Tables 7 and 9 are satisfied, additional sampling might be needed to satisfy DQO SQs #4 and #5 from DQO Report Table 9, based on the resulting data.

The outcome of the groundwater data evaluation will allow for delineation of areas where the VI pathway from groundwater impacts is incomplete (that is, where groundwater concentrations are below the groundwater screening levels) or is potentially complete (that is, where groundwater concentrations are above the screening levels and where existing buildings not slated for demolition will remain and/or where buildings might be constructed in the future). The use of the groundwater screening levels calculated with the updated default attenuation factors and equilibrium partitioning with Henry’s Law constants represents a conservative approach to evaluating potential groundwater impacts to the VI pathway. As needed, Boeing might elect to conduct further evaluation, including a risk assessment specific to the area of interest (for example, area potentially impacted by off‐gassing from groundwater), consistent with the “multiple lines of evidence” approach (DTSC, 2011a). As part of the further evaluation, soil gas data collected for source characterization in areas overlying groundwater plumes could be used to further assess potential empirical relationships between groundwater and soil gas data and to evaluate the appropriateness of the default attenuation factors to refine the VOC impacted extent delineation.

This activity is consistent with the DTSC VI guidance regarding site characterization (Steps 2 and 6), exposure pathway evaluation and screening (Steps 3, 5, and 7), and potential indoor air sampling and response actions if warranted by the DQO process (Steps 4, 8, 9, 10, and 11).

4.4 Data Evaluation, Documentation, and Reporting The data collected in support of the VI assessment will be evaluated to confirm that the RFI DQOs have been satisfied. The procedures used to conduct and evaluate the VI pathway will be documented and reported for DTSC review and approval. The DQO evaluation is described in the Master RFI Data Gap Work Plan, Santa Susana Field Laboratory, Ventura County, California (CH2M HILL, 2013c) and the subsequent addendum prepared for each Boeing RFI subarea. Each addendum will include the proposed sampling and analysis plan that presents the approach for addressing the RFI data gaps (including VI‐related data gaps) identified through the DQO process. Additional reporting requirements, including laboratory reports, modeling results, and an uncertainty analysis, will be provided in a format that is agreed upon by Boeing and DTSC. The future RFI documentation will include an evaluation of areas where the VI pathway is (and is not) potentially complete and significant, along with corresponding recommendations for CMS and CNFA decisions. The future RFI documentation will incorporate the “multiple lines of evidence” approach for evaluating VI. The documentation will consider existing soil, soil vapor, and groundwater data, as well as supporting information. Consideration of multiple sources of data and information together, rather than relying on a single dataset, will provide a more comprehensive understanding of VI and lead to better informed decision‐making.

5.0 Overall Summary of Vapor Intrusion Assessment Approach In summary, the proposed VI assessment approach for the Boeing SSFL RFI project begins with development of the appropriate characterization levels and a review of historical documentation and existing data to confirm that all VOC spills and releases have been identified. The existing soil gas and groundwater quality data will be compared against appropriate characterization screening levels (provided in Tables A‐2 and A‐3 of this TM) to assess whether they are sufficient to evaluate both the nature and extent and the fate and transport of impacts. Additional soil gas data will be collected where required to complete characterization of the nature and extent and fate and transport of impacts and to support remedial planning. The areas at Boeing SSFL where the VI pathway might be complete will be spatially delineated by considering the known or suspected vapor sources, the nature and extent of impacts, and the fate and transport of VOC constituents. The VI assessment approach is consistent with the comprehensive DQO evaluation and provides a systematic and defensible process that relies on multiple line of evidence for completing the VI assessment portion of the RFI to identify areas where the VI


8

pathway could be (or is not) potentially complete and significant and for preparing documentation to support CMS and CNFA recommendations.

6.0 References California Environmental Protection Agency, Department of Toxic Substances Control (DTSC). 2011a. Final

Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air. October.

DTSC. 2011b. Vapor Intrusion Mitigation Advisory, Final, Revision 1. October.

DTSC. 2012. Advisory – Active Soil Gas Investigations. April.

California Environmental Protection Agency, Office of Environmental Health Hazard Assessment (OEHHA). 2005. Use of Human Health Screening Levels (CHHSLs) in Evaluation of Contaminated Property. January.

OEHHA. 2010. Risk Assessment Soil Screening Numbers. Available at: http://oehha.ca.gov/risk/chhsltable.html. Accessed on

CH2M HILL. 2013a. Comprehensive Data Quality Objectives, RCRA Facility Investigation, Santa Susana Field Laboratory, Ventura County, California. March.

CH2M HILL. 2013b. Integration of the Surficial Media Operable Unit Risk Assessment Methodology with the Data Quality Objectives Process, Boeing RCRA Facility Investigation, Santa Susana Field Laboratory, Ventura County, California. Technical Memorandum. March.

CH2M HILL. 2013c. Master RFI Data Gap Work Plan, Santa Susana Field Laboratory, Ventura County, California. March.

MWH International, Inc. (MWH). 2005. Standardized Risk Assessment Methodology Work Plan, Revision 2. Santa Susana Field Laboratory, Ventura County. September.

MWH. 2007. Vapor Migration Modeling Validation Study Work Plan. Santa Susana Field Laboratory, Ventura County. November.

MWH. 2011. Ecological Risk‐Based Screening Levels for Use in Ecological Risk Assessments in the Santa Susana Field Laboratory, Ventura County, California. November.

National Aeronautics and Space Administration. 2012. Final Soil Vapor Standard Operating Procedure for NASA Sites at the Santa Susana Field Laboratory, Ventura County, California. March.

United States Environmental Protection Agency (USEPA). 2002. Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance). Office of Solid Waste and Emergency Response. November.

USEPA, Office of Solid Waste and Emergency Response. 2010. White Paper: “Review of the Draft 2002 Subsurface Vapor Intrusion Guidance.” August.

USEPA. 2012. Vapor Intrusion Database. Available at: http://www.epa.gov/oswer/vaporintrusion/vi_data.html. Accessed January 2012.


9

TABLE A‐2

Characterization Screening Levels for Vapor Intrusion, Carcinogenic Effects

Updated Approach for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

CASRN Chemical

Commercial/ Industrial Indoor Air –

Carcinogen (µg/m3)

Commercial/ Industrial Subslab

Vapor – Carcinogen(µg/m3)

Residential Soil Vapor – Carcinogen

(µg/m3)

Commercial/ Industrial Soil Vapor –

Carcinogen (µg/m3)

Residential Groundwater –

Carcinogen (µg/L)

Commercial/ Industrial Groundwater –

Carcinogen (µg/L)

Source For Cancer Toxicity Value

Target Analytes in the Soil Vapor Sampling SOP (National Aeronautics and Space Administration, 2012)

56235 Carbon tetrachloride 9.73E‐02 1.95E+00 5.79E+01 1.95E+02 5.35E‐02 1.80E‐01 Cal/EPA

67663 Chloroform 7.71E‐01 1.54E+01 4.59E+02 1.54E+03 3.18E+00 1.07E+01 Cal/EPA

71432 Benzene 1.41E‐01 2.82E+00 8.39E+01 2.82E+02 3.86E‐01 1.30E+00 Cal/EPA

71556 1,1,1‐Trichloroethane ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

75003 Chloroethane (ethyl chloride) ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

75014 Vinyl chloride (chloroethene) 5.24E‐02 1.05E+00 3.12E+01 1.05E+02 2.81E‐02 9.45E‐02 Cal/EPA

75092 Methylene chloride 4.09E+00 8.18E+01 2.43E+03 8.18E+03 1.90E+01 6.38E+01 Cal/EPA

75343 1,1‐Dichloroethane 2.56E+00 5.11E+01 1.52E+03 5.11E+03 6.87E+00 2.31E+01 Cal/EPA

75354 1,1‐Dichloroethylene ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

75694 Trichlorofluoromethane ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

75718 Dichlorodifluoromethane ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

76131 1,1,2‐Trichloro‐1,2,2‐trifluoroethane ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

79005 1,1,2‐Trichloroethane 2.56E‐01 5.11E+00 1.52E+02 5.11E+02 4.75E+00 1.59E+01 Cal/EPA

79016 Trichloroethylene 9.97E‐01 1.99E+01 5.93E+02 1.99E+03 1.54E+00 5.18E+00 USEPA

79345 1,1,2,2‐Tetrachloroethane 7.05E‐02 1.41E+00 4.20E+01 1.41E+02 2.96E+00 9.93E+00 Cal/EPA

95476 o‐Xylene ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

100414 Ethylbenzene 1.64E+00 3.27E+01 9.73E+02 3.27E+03 3.19E+00 1.07E+01 Cal/EPA

106423 p‐Xylene ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

107062 1,2‐Dichloroethane 1.95E‐01 3.89E+00 1.16E+02 3.89E+02 2.51E+00 8.43E+00 Cal/EPA

108383 m‐Xylene ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

108883 Toluene ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

127184 Tetrachloroethylene 1.57E+01 3.14E+02 9.36E+03 3.14E+04 1.36E+01 4.57E+01 USEPA

156592 cis‐1,2‐Dichloroethylene ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

156605 trans‐1,2‐Dichloroethylene ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

630206 1,1,1,2‐Tetrachloroethane 5.52E‐01 1.10E+01 3.29E+02 1.10E+03 3.42E+00 1.15E+01 USEPA


10

TABLE A‐2

Characterization Screening Levels for Vapor Intrusion, Carcinogenic Effects


CASRN Chemical


Carcinogen (µg/m3)


Vapor – Carcinogen(µg/m3)

Residential Soil Vapor – Carcinogen

(µg/m3)

Commercial/ Industrial Soil Vapor –

Carcinogen (µg/m3)

Residential Groundwater –

Carcinogen (µg/L)

Commercial/ Industrial Groundwater –

Carcinogen (µg/L)

Source For Cancer Toxicity Value

Other VOCs Historically Detected at SSFL

67630 Isopropanol ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

67641 Acetone ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

75150 Carbon disulfide ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

78933 Methylethylketone (2‐butanone) ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

108907 Chlorobenzene ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

120821 1,2,4‐Trichlorobenzene ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐

Notes:

CASRN = Chemical Abstract Services Registry Number NA = not available µg/L = micrograms per liter µg/m3 = micrograms per cubic meter

Commercial/industrial indoor air screening level is the CHHSL (OEHHA, 2005a‐b); values were calculated using the current Cal/EPA toxicity values provided on OEHHA's toxicity criteria database, when available, or toxicity values provided by USEPA, if appropriate values were not available from OEHHA.

Commercial/industrial subslab soil vapor screening level is calculated from the commercial/industrial CHHSL using an attenuation factor of 0.05 for an existing commercial/industrial building (DTSC, 2011a).

Residential soil vapor screening level is calculated from a residential CHHSL (OEHHA, 2005a‐b) using an attenuation factor of 0.001 for a future residential building.

Commercial/ industrial soil vapor screening level is calculated from a commercial/industrial CHHSL (OEHHA, 2005a‐b) using an attenuation factor of 0.0005 for a future commercial/ industrial building.

Groundwater screening levels are calculated from the residential or commercial/industrial soil vapor screening level using equilibrium partitioning with Henry's Law.


11

TABLE A‐3

Characterization Screening Levels for Vapor Intrusion, Noncarcinogenic Effects


CASRN Chemical


Noncarcinogen (µg/m3)


Soil Vapor – Noncarcinogen

(µg/m3)

Residential Soil Vapor –

Noncarcinogen(µg/m3)

Commercial/ Industrial Soil

Vapor – Noncarcinogen

(µg/m3)

Residential Groundwater – Noncarcinogen

(µg/L)

Commercial/ Industrial

Groundwater – Noncarcinogen

(µg/L)

Source for Non cancer

Toxicity Value

Low TRV‐based

EcoRBSL (µg/m3)

Target Analytes in the Soil Vapor Sampling SOP (National Aeronautics and Space Administration, 2012)

56235 Carbon tetrachloride 5.84E+01 1.17E+03 4.17E+04 1.17E+05 3.85E+01 1.08E+02 Cal/EPA 8.4E+03

67663 Chloroform 4.38E+02 8.76E+03 3.13E+05 8.76E+05 2.17E+03 6.07E+03 Cal/EPA 1.6E+03

71432 Benzene 8.76E+01 1.75E+03 6.26E+04 1.75E+05 2.88E+02 8.05E+02 Cal/EPA 7.6E+02

71556 1,1,1‐Trichloroethane 1.46E+03 2.92E+04 1.04E+06 2.92E+06 1.54E+03 4.32E+03 Cal/EPA 2.5E+05

75003 Chloroethane (ethyl chloride) 4.38E+04 8.76E+05 3.13E+07 8.76E+07 7.11E+04 1.99E+05 Cal/EPA 1.32E+06

75014 Vinyl chloride (chloroethene) 1.46E+02 2.92E+03 1.04E+05 2.92E+05 9.40E+01 2.63E+02 USEPA 7.3E+02

75092 Methylene chloride 5.84E+02 1.17E+04 4.17E+05 1.17E+06 3.25E+03 9.11E+03 Cal/EPA 1.2E+04

75343 1,1‐Dichloroethane ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ 2.4E+05

75354 1,1‐Dichloroethylene 2.92E+02 5.84E+03 2.09E+05 5.84E+05 2.02E+02 5.65E+02 EPA 7.9E+03

75694 Trichlorofluoromethane 1.02E+03 2.04E+04 7.30E+05 2.04E+06 1.90E+02 5.31E+02 EPA 1.21E+06

75718 Dichlorodifluoromethane 1.46E+02 2.92E+03 1.04E+05 2.92E+05 7.75E+00 2.17E+01 EPA 1.21E+06

76131 1,1,2‐Trichloro‐1,2,2‐trifluoroethane 4.38E+04 8.76E+05 3.13E+07 8.76E+07 1.51E+03 4.23E+03 EPA 1.21E+06

79005 1,1,2‐Trichloroethane 2.92E‐01 5.84E+00 2.09E+02 5.84E+02 6.51E+00 1.82E+01 EPA 1.1E+03

79016 Trichloroethylene 2.92E+00 5.84E+01 2.09E+03 5.84E+03 5.41E+00 1.52E+01 USEPA 8.5E+03

79345 1,1,2,2‐Tetrachloroethane ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ NA

95476 o‐Xylene 1.02E+03 2.04E+04 7.30E+05 2.04E+06 3.64E+03 1.02E+04 Cal/EPA 1.0E+04

100414 Ethylbenzene 2.92E+03 5.84E+04 2.09E+06 5.84E+06 6.83E+03 1.91E+04 Cal/EPA 3.1E+04

106423 p‐Xylene 1.02E+03 2.04E+04 7.30E+05 2.04E+06 2.73E+03 7.65E+03 Cal/EPA 1.0E+04

107062 1,2‐Dichloroethane 1.02E+01 2.04E+02 7.30E+03 2.04E+04 1.58E+02 4.43E+02 USEPA 5.6E+04

108383 m‐Xylene 1.02E+03 2.04E+04 7.30E+05 2.04E+06 2.62E+03 7.35E+03 Cal/EPA 1.0E+04

108883 Toluene 4.38E+02 8.76E+03 3.13E+05 8.76E+05 1.21E+03 3.38E+03 Cal/EPA 2.2E+02

127184 Tetrachloroethylene 5.84E+01 1.17E+03 4.17E+04 1.17E+05 6.06E+01 1.70E+02 EPA 3.2E+04

156592 cis‐1,2‐Dichloroethylene 8.76E+01 1.75E+03 6.26E+04 1.75E+05 3.90E+02 1.09E+03 EPA 2.5E+04

156605 trans‐1,2‐Dichloroethylene 8.76E+01 1.75E+03 6.26E+04 1.75E+05 3.89E+02 1.09E+03 USEPA 2.5E+04

630206 1,1,1,2‐Tetrachloroethane ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ NA


12

TABLE A‐3

Characterization Screening Levels for Vapor Intrusion, Noncarcinogenic Effects


CASRN Chemical


Noncarcinogen (µg/m3)


Soil Vapor – Noncarcinogen

(µg/m3)

Residential Soil Vapor –

Noncarcinogen(µg/m3)

Commercial/ Industrial Soil

Vapor – Noncarcinogen

(µg/m3)

Residential Groundwater – Noncarcinogen

(µg/L)

Commercial/ Industrial

Groundwater – Noncarcinogen

(µg/L)

Source for Non cancer

Toxicity Value

Low TRV‐based

EcoRBSL (µg/m3)

Other VOCs Historically Detected at SSFL

67630 Isopropanol 1.02E+04 2.04E+05 7.30E+06 2.04E+07 2.24E+07 6.28E+07 EPA NA

67641 Acetone 4.53E+04 9.05E+05 3.23E+07 9.05E+07 2.35E+07 6.57E+07 USEPA 1.74E+06

75150 Carbon disulfide 1.17E+03 2.34E+04 8.34E+05 2.34E+06 1.47E+03 4.10E+03 Cal/EPA 1.6E+03

78933 Methylethylketone (2‐butanone) 7.30E+03 1.46E+05 5.21E+06 1.46E+07 2.34E+06 6.55E+06 USEPA 1.15E+06

108907 Chlorobenzene 1.46E+03 2.92E+04 1.04E+06 2.92E+06 8.63E+03 2.42E+04 Cal/EPA 7.7E+04

120821 1,2,4‐Trichlorobenzene 2.92E+00 5.84E+01 2.09E+03 5.84E+03 3.86E+01 1.08E+02 USEPA NA

Notes:

CASRN = Chemical Abstract Services Registry Number NA = not available µg/L = micrograms per liter µg/m3 = micrograms per cubic meter

Commercial/ industrial indoor air screening level is the CHHSL (OEHHA, 2005a‐b); values were calculated using the current Cal/EPA toxicity values provided on OEHHA's toxicity criteria database, when available, or toxicity values provided by EPA, if appropriate values were not available from OEHHA.

Commercial/ industrial subslab soil vapor screening level is calculated from the commercial/industrial CHHSL using an attenuation factor of 0.05 for an existing commercial/industrial building (DTSC, 2011a).

Residential soil vapor screening level is calculated from a residential CHHSL (OEHHA, 2005a‐b) using an attenuation factor of 0.001 for a future residential building.

Commercial/industrial soil vapor screening level is calculated from a commercial/industrial CHHSL (OEHHA, 2005a‐b) using an attenuation factor of 0.0005 for a future commercial/ industrial building.

Groundwater screening levels are calculated from the residential or commercial/industrial soil vapor screening level using equilibrium partitioning with Henry's Law.

Low toxicity reference value‐based ecological risk‐based screening levels (EcoRSBLs) will be used to evaluate soil gas data in locations where exposure pathways to burrowing mammals need to be addressed.

Attachment A1 Development of Characterization Screening Levels for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana

Field Laboratory, Ventura County, California

A1-1

ATTACHMENT A1

Development of Characterization Screening Levels for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California 1.0 Introduction and Purpose This attachment presents the development of the proposed characterization screening levels to assess vapor intrusion (VI) for the Boeing Resource Conservation and Recovery Act (RCRA) facility investigation project at the Santa Susana Field Laboratory (SSFL). The overall approach to assessing the VI pathway at SSFL and the proposed characterization screening levels are presented in the parent technical memorandum, to which this document is attached, titled Recommended Approach for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California (VI TM) (CH2M HILL, 2013).

Development of the characterization screening levels is the initial step in the VI evaluation at the SSFL. The characterization screening levels are concentrations of volatile organic compounds (VOCs) in soil gas and groundwater, which are proposed for use in soil gas investigations to evaluate potential VI impacts and for shallow groundwater investigations to identify portions of groundwater plumes with potential VI impacts.

The characterization screening levels were developed using the risk‐based methodology embodied in the California human health screening levels (CHHSLs), along with updated attenuation factors presented in the final VI investigation guidance document issued by the California Environmental Protection Agency, Department of Toxic Substances Control (DTSC) (DTSC, 2011). This documentation for the development of the characterization screening levels is subject to DTSC approval before using them to evaluate soil gas and groundwater data.

2.0 Approach to Screening Levels Development The characterization screening levels been developed for comparison with existing and future concentration data in indoor air, subslab soil vapor, soil vapor, and groundwater grab samples and are presented in Table A‐2 in the VI TM. The screening levels in indoor air are calculated using the methodology and exposure factors presented in the California Environmental Protection Agency (Cal/EPA) Office of Environmental Health Hazard Assessment (OEHHA) CHHSL guidance (OEHHA, 2005a‐b). As described in the VI TM (CH2M HILL, 2013), CHHSLs are appropriate for developing characterization screening levels for soil gas. The thresholds of concern used to develop CHHSLs are an excess lifetime cancer risk of 1 in a million (10‐6) and a hazard quotient of 1.0 for noncancer health effects.1 The presence of a chemical at concentrations below the corresponding CHHSLs can be assumed not to pose a significant health risk to hypothetical site occupants. Conversely, the presence of a chemical at concentrations that exceed a CHHSL does not indicate that adverse impacts to human health would occur but would suggest that further evaluation is warranted. Further evaluation might include additional sampling, consideration of ambient levels in the environment, a reassessment of the assumptions used to calculate the CHHSLs, or a site‐specific risk assessment. The CHHSLs are intended for use as screening levels only and are not intended to be regulatory cleanup standards or action levels (OEHHA, 2005b).

Toxicity values developed by Cal/EPA and published in the toxicity criteria database by the OEHHA were used, when available, to calculate CHHSLs in indoor air (Cal/EPA‐OEHHA updates its online database regularly). For VOCs that had no toxicity values developed by Cal/EPA‐OEHHA, CHHSL values were calculated using toxicity values obtained from the United States Environmental Protection Agency (USEPA), along with the exposure factors

1 Where both cancer risk and noncancer-based screening levels have been calculated, the lower of the two values is used to develop screening levels.

ATTACHMENT A1 DEVELOPMENT OF CHARACTERIZATION SCREENING LEVELS FOR ASSESSING THE VAPOR INTRUSION PATHWAY, BOEING RCRA FACILITY INVESTIGATION PROJECT, SANTA SUSANA FIELD LABORATORY, VENTURA COUNTY, CALIFORNIA

A1-2

provided by Cal/EPA (OEHHA, 2005a). Toxicity values from USEPA were selected in accordance with the hierarchy of toxicity values presented in Human Health Toxicity Values in Superfund Risk Assessments (USEPA, 2003). The toxicity values used in the calculations were current values obtained from USEPA’s regional screening level (RSL) Web site (USEPA, 2011).

Screening levels in subslab soil vapor were calculated from the indoor air CHHSLs using attenuation factors provided in DTSC’s VI guidance document (DTSC, 2011). A detailed description of the calculations, assumptions, and input values used to develop the screening levels is provided in Section 4 of this attachment.

Screening levels have been developed for the VOCs listed as target analytes in the Final Soil Vapor Standard Operating Procedure (SOP) for National Aeronautics and Space Administration (NASA) Sites at the SSFL in Ventura County, California (NASA, 2012). In addition to these target analytes, a query was performed of historical soil gas data at SSFL to identify other VOCs that were above their respective detection limit and might require characterization screening levels. Screening levels were calculated for these other VOCs that historically had been detected in soil gas samples at some frequency (three or greater detections) and that had available toxicity value information.

3.0 Summary of Characterization Screening Levels The proposed screening levels (Table A‐2 in the VI TM) were developed for the following media and exposure scenarios:

Commercial/industrial indoor air CHHSLs. The commercial/industrial indoor air screening level is the CHHSL (OEHHA, 2005a‐b); values were calculated using the current Cal/EPA toxicity values provided on OEHHA’s toxicity criteria database, when available, or toxicity values provided by USEPA, if appropriate values were not available from OEHHA.

Commercial/industrial subslab soil vapor. These screening levels are calculated from the commercial/ industrial CHHSL using an attenuation factor of 0.05 for an existing commercial/industrial building (DTSC, 2011).

Future residential soil vapor. These screening levels are calculated from a residential CHHSL in indoor air (OEHHA, 2005a‐b) using an attenuation factor of 0.001 for a future residential building.

Future commercial/industrial soil vapor. These screening levels are calculated from a commercial/industrial CHHSL in indoor air (OEHHA, 2005a‐b) using an attenuation factor of 0.0005 for a future commercial/industrial building.

Shallow groundwater. Groundwater screening levels are calculated from the future residential soil vapor screening levels using partitioning with Henry’s Law.

4.0 Supporting Information on Development of the Characterization Screening Levels

This section presents supporting information with the calculations used to develop screening levels for VI for the Boeing portion of the SSFL. The approach used in these calculations is drawn primarily from guidance updated in October 2011 by DTSC. For chemicals that DTSC guidance does not address, guidance for these calculations has been drawn from USEPA.

In 2005, Cal/EPA developed the CHHSLs for use in screening chemical concentrations in soil for further evaluation (OEHHA, 2005a‐b). CHHSLs were also developed for soil vapor and indoor air to evaluate VI pathways using the standard of practice at the time (OEHHA, 2005b). The CHHSLs were updated (or added) on September 23, 2010 (OEHHA, 2010). In October 2011, DTSC issued revised VI guidance (DTSC, 2011), incorporating current approaches for assessing potential VI pathways. Updates in the 2011 guidance developed by DTSC include changes in attenuation factors from the values used originally for calculating the CHHSLs for soil vapor or subslab samples.

ATTACHMENT A1 DEVELOPMENT OF CHARACTERIZATION SCREENING LEVELS FOR ASSESSING THE VAPOR INTRUSION PATHWAY, BOEING RCRA FACILITY INVESTIGATION PROJECT,

SANTA SUSANA FIELD LABORATORY, VENTURA COUNTY, CALIFORNIA

A1-3

The DTSC VI guidance provides the updated attenuation factors but does not include updated VI screening levels for soil gas and subslab soil gas samples.

4.1 Methodology The VI screening levels subject to revision based on DTSC’s 2011 VI guidance are:

Screening levels in indoor air

Screening levels in subslab soil vapor

Screening levels in soil vapor

Screening levels in shallow (uppermost) groundwater

Sections 4.1.1 through 4.1.4 provide the equations and input values used to calculate VI screening levels in indoor air, subslab soil vapor, exterior soil vapor, and groundwater.

4.1.1 Equations for Calculating Target Indoor Air Concentrations The following equation is used to calculate the cancer target indoor air concentration:

⁄

(1)

Where:

Cia‐c = Cancer target indoor air concentration (micrograms per cubic meter [µg/m3]) TR = Target risk level (unitless) ATC = Averaging time for carcinogens (years) IUR = Inhalation unit risk factor (µg/m3)‐1 EF = Exposure frequency (days/year) ED = Exposure duration (years)

The following equation is used to calculate the noncancer target indoor air concentration:

⁄

⁄ (2)

Where:

Cia‐nc = Noncancer target indoor air concentration (µg/m3) THQ = Target hazard quotient (unitless) REL = Reference exposure level (µg/m3) EF = Exposure frequency (days/year) ED = Exposure duration (years)

The target concentrations in indoor air are calculated for residential and commercial industrial land uses. The inputs to these equations are presented in Table A1‐1.

TABLE A1‐1 Input Parameters for Calculation of Target Indoor Air ConcentrationsDevelopment of Characterization Screening Levels for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

Input Parameter Residential Land Use Industrial/Commercial Land Use

Target Cancer Risk 1 x 10‐6 1 x 10‐6

Target Hazard Quotient 1 1

Averaging Time – Cancer (years) 70 70

Exposure Frequency (days/year) 350 250

Exposure Duration (years) 30 25

Source: OEHHA, 2005a, Table B‐2 and Section 3.1.2.


A1-4

4.1.2 Toxicity Values for Calculating Target Indoor Air Concentrations The Cal/EPA OEHHA toxicity criteria database (OEHHA, undated) was the preferred source for inhalation unit risk factors and chronic reference exposure levels. If the appropriate values were not available from the OEHHA toxicity criteria database, toxicity values were obtained from the USEPA Integrated Risk Information System (IRIS). The toxicity values obtained from IRIS were inhalation unit risk values for calculating carcinogenic target indoor air concentrations and the reference concentration values for calculating noncancer target indoor air concentrations. When toxicity values were not available from IRIS, provisional toxicity values were used, selected in accordance with USEPA’s hierarchy of toxicity values (USEPA, 2003). The toxicity values are provided in Table A1‐2.

TABLE A1‐2 Toxicity Values Development of Characterization Screening Levels for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

CASRN Chemical

Toxicity Values

Cal/EPA Inhalation Unit

Risk Factor (µg/m

3)‐1

USEPA Inhalation Unit

Risk Factor (µg/m3)‐1

Cal/EPA Reference Exposure Level

(µg/m3)

USEPA Reference Concentration

(µg/m3)

56235 Carbon tetrachloride 4.20E‐05 6.00E‐06 4.00E+01 1.00E+02

67630 Isopropanol 7.00E+03

67641 Acetone 3.10E+04

67663 Chloroform 5.30E‐06 2.30E‐05 3.00E+02 9.80E+01

71432 Benzene 2.90E‐05 7.80E‐06 6.00E+01 3.00E+01

71556 1,1,1‐Trichloroethane 1.00E+03 5.00E+03

75003 Chloroethane (ethyl chloride) 3.00E+04 1.00E+04

75014 Vinyl chloride (chloroethene) 7.80E‐05 4.40E‐06 1.00E+02

75092 Methylene chloride 1.00E‐06 4.70E‐07 4.00E+02 1.00E+03

75150 Carbon disulfide 8.00E+02 7.00E+02

75343 1,1‐Dichloroethane 1.60E‐06 1.60E‐06

75354 1,1‐Dichloroethylene 2.00E+02

75694 Trichlorofluoromethane 7.00E+02

76131 1,1,2‐Trichloro‐1,2,2‐trifluoroethane 3.00E+04

75718 Dichlorodifluoromethane 1.00E+02

78933 Methylethylketone (2‐butanone) 5.00E+03

79005 1,1,2‐Trichloroethane 1.60E‐05 1.60E‐05 2.00E‐01

79016 Trichloroethylene 4.10E‐06 2.00E+00

79345 1,1,2,2‐Tetrachloroethane 5.80E‐05 5.80E‐05

95476 o‐Xylene 7.00E+02 1.00E+02

100414 Ethylbenzene 2.50E‐06 2.50E‐06 2.00E+03 1.00E+03

106423 p‐Xylene 7.00E+02 1.00E+02

107062 1,2‐Dichloroethane 2.10E‐05 2.60E‐05 7.00E+00

108383 m‐Xylene 7.00E+02 1.00E+02

108883 Toluene 3.00E+02 5.00E+03

108907 Chlorobenzene 1.00E+03 5.00E+01



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TABLE A1‐2 Toxicity Values Development of Characterization Screening Levels for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

CASRN Chemical

Toxicity Values

Cal/EPA Inhalation Unit


USEPA Inhalation Unit


Cal/EPA Reference Exposure Level

(µg/m3)

USEPA Reference Concentration

(µg/m3)

120821 1,2,4‐Trichlorobenzene 2.00E+00

127184 Tetrachloroethylene 5.90E‐06 2,60E‐07 4.00E+01

156592 cis‐1,2‐Dichloroethylene 6.00E+01

156605 trans‐1,2‐Dichloroethylene 6.00E+01

630206 1,1,1,2‐Tetrachloroethane 7.40E‐06

Notes:

Cal/EPA toxicity values were obtained from the OEHHA toxicity criteria database (OEHHA, undated).

USEPA toxicity values were selected using the hierarchy presented in Human Health Toxicity Values in Superfund Risk Assessments (USEPA, 2003). The toxicity values used in the calculations were obtained from USEPA RSL Web site (USEPA, 2011).

4.1.3 Equation for Calculating Screening Levels in Subslab and Soil Gas The relationship between the subslab soil vapor or exterior soil vapor concentration beneath a building and the indoor air concentration in that building is represented by the attenuation factor:

∝

(3)

Where:

Cindoor = Concentration in indoor air (µg/m3) Csoil gas = Concentration in subslab soil vapor or exterior soil vapor (µg/m3)

The preceding equation is rearranged to solve for a screening level in subslab soil vapor or exterior soil vapor, as follows:

∝ (4)

DTSC’s VI guidance provides default attenuation factors for the following three sampling locations relative to the building foundation:

Contaminant source (that is, concentration in soil vapor evaluated using an exterior vapor gas sample)

Subslab (that is, directly under a slab)

Crawl space

These default attenuation factors reflect reasonably protective assumptions for concentrations in indoor air due to VI. The screening levels developed with these default attenuation factors are intended to be used in a preliminary evaluation of VI pathways, as described in Step 5 of DTSC’s VI guidance. Further discussion about the derivation of these attenuation factors is provided in the DTSC VI guidance (DTSC, 2011).

The attenuation factors are shown in Table A1‐3.


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TABLE A1‐3 Default Attenuation Factors Development of Characterization Screening Levels for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

Building Scenario Building Type Sample Location Attenuation Factor

Existing Residential Contaminant Source 0.002

Residential Crawl Space 1.0

Residential Subslab 0.05

Commercial/Industrial Contaminant Source 0.001

Commercial/Industrial Subslab 0.05

Future Residential Contaminant Source 0.001

Commercial/Industrial Contaminant Source 0.0005

Source: DTSC, 2011. Samples from crawl spaces are evaluated using indoor air screening levels.

4.1.4 Equations for Calculating Screening Levels in Groundwater Concentrations of VOCs in soil vapor overlying shallow groundwater are assumed to be in equilibrium according to Henry’s Law:

,

(5)

Where:

Csoil gas = Concentration in soil gas (µg/m3) Cgroundwater = Concentration in groundwater (micrograms per liter [µg/L]) H’TS = Henry’s Law constant at the system (groundwater) temperature (dimensionless)

This equation is rearranged to solve for the screening level in groundwater, using the screening level in soil vapor:

, (6)

The dimensionless form of the Henry’s Law constant at the groundwater temperature is used to calculate a groundwater screening level (DTSC, 2011). The dimensionless Henry’s Law constant at the groundwater temperature can be estimated using the Clapeyron equation (OEHHA, 2005a; USEPA, 2003):

∆ ,

(7)

Where:

H’TS = Henry’s Law constant at the system temperature (that is groundwater temperature) (dimensionless)

Hv,TS = Enthalpy of vaporization at the system temperature (cal/mole) TS = System temperature (297 degrees Kelvin [K]) TR = Reference temperature (298 degrees K) HR = Henry’s Law constant at the reference temperature (atm‐m3/mole) Rc = Universal gas constant (1.9872 cal/mole‐K) R = Universal gas constant (8.205 x 10‐5 atm‐m3/mole‐K)

The enthalpy of vaporization at the system temperature is calculated as follows (Lyman et al., 1990):

∆ , ∆ , ⁄

⁄ (8)



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Where:

Hv,TS = Enthalpy of vaporization at the system temperature (cal/mole)

Hv,b = Enthalpy of vaporization at the normal boiling point (cal/mole) TS = System temperature (degrees K) TC = Critical temperature (degrees K) TB = Normal boiling point (degrees K) n = Constant (unitless)

The value of exponent n is a function of the ratio TB/TC as shown below:

TB/TC N

less than 0.57 0.30

0.57 to 0.71 0.74 (TB/TC) – 0.116

more than 0.71 0.41

The hierarchy of sources used to select Henry’s Law constants is described in the user’s guide to the USEPA table of RSLs, and the sources for those values are shown on the USEPA RSL Web site (USEPA, 2011). The system temperature is the average soil and groundwater temperature assumed for California. That value is 24 degrees Celsius (297 degrees K) as described in the VI final guidance (DTSC, 2011). The other chemical‐specific parameters—enthalpy of vaporization at the normal boiling point, critical temperature, and normal boiling point—were obtained from the hazardous substances databank (http://toxnet.nlm.nih.gov/cgi‐bin/sis/htmlgen?HSDB).

As described in the VI guidance (DTSC, 2011), the Henry’s Law constant should be calculated using site‐specific groundwater temperatures. The spreadsheet used to calculate the screening levels can calculate Henry’s Law constants using site‐specific groundwater temperature data. The input parameters and temperature‐corrected Henry’s law constants are provided in Table A1‐4.

4.2 Summary The characterization screening levels for evaluating VI at sites have been developed using the updated VI guidance that DTSC published in October 2011. Screening levels have been developed for indoor air, soil gas, subslab soil gas, and groundwater. The screening levels are based on a 1 x 10‐6 target cancer risk level for carcinogenic VOCs and a noncancer hazard quotient of 1 for noncarcinogenic VOCs. When both carcinogenic and noncarcinogenic values are available for a screening level, the lower value was selected for use as the screening level.

The screening levels in indoor air were developed with exposure factors published in Cal/EPA’s CHHSLs methodology and with toxicity values published by the OEHHA. For VOCs that do not have Cal/EPA toxicity values, screening levels have been calculated using toxicity values obtained from USEPA. Soil gas and subslab screening levels are calculated from indoor air screening levels using updated attenuation factors published in the October 2011 VI guidance (DTSC, 2011). Groundwater screening levels are calculated from soil gas screening levels using a temperature‐corrected Henry’s Law constant.

5.0 References California Environmental Protection Agency, Department of Toxic Substances Control (DTSC). 2011. Final

Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air. Available at: http://www.dtsc.ca.gov/AssessingRisk/upload/Final_VIG_Oct_2011.pdf. Accessed October 2011.


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California Environmental Protection Agency, Office of Environmental Health Hazard Assessment (OEHHA). 2005a. Human Exposure‐Based Screening Numbers Developed to Aid Estimation of Cleanup Costs for Contaminated Soil. Available at: http://www.calepa.ca.gov/brownfields/documents/2005/ NumberReport.pdf. Accessed on: November 2011.

OEHHA. 2005b. Use of California Human Health Screening Levels (CHHSLs) in Evaluation of Contaminated Properties. Available at: http://www.calepa.ca.gov/brownfields/documents/2005/ CHHSLsGuide.pdf. Accessed on: November 2011.

HSDB. 2011. Hazardous Substances Data Bank, U.S. National Library of Medicine Toxicology Data Network (TOXNET). Available at: http://toxnet.nlm.nih.gov/cgi‐bin/sis/htmlgen?HSDB. Accessed December 2011.

OEHHA. 2010. Risk Assessment Soil Screening Numbers. Available at: http://oehha.ca.gov/risk/chhsltable.html.

OEHHA. Undated. Toxicity Criteria Database. Available at: http://www.oehha.ca.gov/tcdb/. Accessed December 2011.

CH2M HILL. 2013. Recommended Approach for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, California. March.

Lyman, W.J., W.F. Reehl, and D.H. Rosenblatt (eds). 1990. Handbook of Chemical Property Estimation Methods. American Chemical Society. Washington, D.C. Chapter 14.

National Aeronautics and Space Administration (NASA). 2012. Final Soil Vapor Standard Operating Procedure (SOP) for NASA Sites at the Santa Susana Field Laboratory, Ventura County, California. January.

United States Environmental Protection Agency (USEPA). 2003. Human Health Toxicity Values in Superfund Risk Assessments. OSWER Directive 8285.7‐53. December 5.

USEPA. 2011. Regional Screening Table. Available at: http://www.epa.gov/reg3hwmd/risk/human/rb‐concentration_table/. November update. Accessed December 2011.

ATTACHMENT 1 DEVELOPMENT OF CHARACTERIZATION SCREENING LEVELS FOR ASSESSING THE VAPOR INTRUSION PATHWAY, BOEING RCRA FACILITY INVESTIGATION PROJECT, SANTA SUSANA FIELD LABORATORY, VENTURA COUNTY, CALIFORNIA

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TABLE A1‐4 Chemical‐specific Parameters Used for Temperature‐corrected Henry’s Law Constant Calculation Development of Characterization Screening Levels for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

CASRN Chemical

Henry’s Law Constant at Reference Temperature

(atm‐m3/mole)

Enthalpy of Vaporization at the Normal Boiling Point

(cal/mole) Normal Boiling Point

(deg K) Normal Critical Temperature

(deg K) TB/TC Value of Exponent n as a

function of TB/TC

Enthalpy of Vaporization at the System Temperature

(cal/mole) Dimensionless Henry’s Law

Constant at System Temperature

56235 Carbon tetrachloride 0.0276 7127 349.9 556.6 0.63 0.35 7,717 1.08E+00

67630 Isopropanol 0.0000081 3160 355.5 508 0.70 0.40 3,600 3.26E‐04

67641 Acetone 0.000035 6955 329.2 508.1 0.65 0.36 7,386 1.38E‐03

67663 Chloroform 0.00367 6988 334.32 536.4 0.62 0.35 7,409 1.44E‐01

71432 Benzene 0.00555 7342 353.24 562.16 0.63 0.35 7,979 2.18E‐01

71556 1,1,1‐Trichloroethane 0.0172 7136 347.24 545 0.64 0.36 7,734 6.75E‐01

75003 Chloroethane (ethyl chloride) 0.0111 6310 285.3 460 0.62 0.34 6,162 4.40E‐01

75014 Vinyl chloride (chloroethene) 0.0278 5250 259.25 432 0.60 0.33 4,842 1.11E+00

75092 Methylene chloride 0.00325 6706 313 510 0.61 0.34 6,885 1.28E‐01

75150 Carbon disulfide 0.0144 6391 319 552 0.58 0.31 6,573 5.69E‐01

75343 1,1‐Dichloroethane 0.00562 6895 330.55 523 0.63 0.35 7,296 2.21E‐01

75354 1,1‐Dichloroethylene 0.0261 6247 304.75 576.05 0.53 0.30 6,300 1.03E+00

75694 Trichlorofluoromethane 0.097 5999 296.7 471 0.63 0.35 5,995 3.85E+00

75718 Dichlorodifluoromethane 0.343 9419 243.2 385 0.63 0.35 7,965 1.35E+01

76131 1,1,2‐Trichloro‐1,2,2‐trifluoroethane 0.526 6788 320.7 487.3 0.66 0.37 7,131 2.07E+01

79005 1,1,2‐Trichloroethane 0.000824 8322 386.15 602 0.64 0.36 9,421 3.20E‐02

79016 Trichloroethylene 0.00985 7505 360.36 544.2 0.66 0.37 8,384 3.85E‐01

79345 1,1,2,2‐Tetrachloroethane 0.000367 8996 419.6 661.15 0.63 0.35 10,401 1.42E‐02

95476 o‐Xylene 0.00518 8661 417.6 630.3 0.66 0.37 10,247 2.01E‐01

100414 Ethylbenzene 0.00788 8501 409.34 617.2 0.66 0.37 9,995 3.05E‐01

106423 p‐Xylene 0.0069 8525 411.52 616.2 0.67 0.38 10,085 2.67E‐01

1330207 Xylenes 0.00518 8525 411.52 616.2 0.67 0.38 10,085 2.01E‐01

107062 1,2‐Dichloroethane 0.00118 7643 356.65 561 0.64 0.35 8,369 4.62E‐02

108383 m‐Xylene 0.00718 8523 412.27 617.05 0.67 0.38 10,092 2.78E‐01

108883 Toluene 0.00664 7930 383.78 591.79 0.65 0.36 9,003 2.59E‐01

108907 Chlorobenzene 0.00311 8410 404.87 632.4 0.64 0.36 9,662 1.21E‐01

120821 1,2,4‐Trichlorobenzene 0.00142 10471 486.15 725 0.67 0.38 13,071 5.41E‐02

127184 Tetrachloroethylene 0.0177 8288 394.4 620.2 0.64 0.35 9,412 6.88E‐01

156592 cis‐1,2‐Dichloroethylene 0.00408 7192 333.65 544 0.61 0.34 7,593 1.60E‐01

156605 trans‐1,2‐Dichloroethylene 0.00408 6717 320.85 516.5 0.62 0.34 6,988 1.61E‐01

Notes:

Dimensional Henry’s Law constants were selected according to the hierarchy of sources provided in USEPA’s RSL table (http://www.epa.gov/reg3hwmd/risk/human/rb‐concentration_table/).

Other chemical‐specific parameters (normal boiling point, normal critical temperature and enthalpy of vaporization at normal boiling point) were obtained from the sources used to develop EPA’s Johnson and Ettinger Model spreadsheet (http://www.epa.gov/oswer/riskassessment/airmodel/johnson_ettinger.htm).

Chemical‐specific parameters not provided on the Johnson and Ettinger model spreadsheet were obtained from National Library of Medicine’s Hazardous Substances Data Bank (HSDB) (http://toxnet.nlm.nih.gov/cgi‐bin/sis/htmlgen?HSDB).

Appendix B Recommended Approach for

Air Dispersion Modeling

B-1

T E C H N I C A L M E M O R A N D U M Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California PREPARED FOR: The Boeing Company


DATE: March 8, 2013

1.0 Introduction and Purpose This technical memorandum presents the recommended air dispersion modeling approach for The Boeing Company (Boeing) Resource Conservation and Recovery Act (RCRA) facility investigation (RFI) project at the Santa Susana Field Laboratory (SSFL). This technical memorandum supports the Comprehensive Data Quality Objectives [DQO] RCRA Facility Investigation Santa Susana Field Laboratory, Ventura County, California (CH2M HILL, 2013a) and is an appendix to that document.

The purpose of air dispersion modeling is to evaluate the potential spatial distribution of chemical constituent impacts to soil resulting from deposition from historical operations and, if appropriate, to determine whether existing soil data are sufficient to characterize the nature and extent of such impacts. If data are not sufficient, the modeling will aid in the selection of soil sampling locations for the forthcoming Boeing RFI data gap work plans for each Boeing RFI subarea. By using available data on historical operations, air dispersion modeling can be performed to provide results that show the potential deposition patterns of materials modeled. This technical memorandum presents a brief summary of the SSFL background information relevant to air dispersion modeling, identification of potential sources to be modeled, a summary of potential air dispersion model options, the proposed air dispersion model to be used, a summary of model input parameters, and the proposed air dispersion modeling path forward for the Boeing SSFL RFI project.

2.0 Regulatory Framework for Air Dispersion Modeling The California Environmental Protection Agency, Department of Toxic Substances Control (DTSC) has oversight responsibility for the Boeing RFI project, including the air dispersion assessment components. DTSC previously engaged the California Air Resources Board (CARB) to perform review of the Boeing air modeling work performed at the Area I Burn Pit RFI site during performance of the Boeing RFI evaluations. CARB is the state agency responsible for statewide air quality management, including the establishment of California ambient air quality standards and enforcement of the federal Clean Air Act. The CARB is also responsible for monitoring the regulatory activity of California’s 35 local air districts. The local air districts, which include the Ventura County Air Pollution Control District, are responsible for promulgating rules and regulations for stationary sources of air pollution within their districts, as well as preparing an air quality plan to achieve compliance with the California ambient air quality standards. The Boeing RFI project is located within the jurisdiction of the Ventura County Air Pollution Control District.

3.0 Prior Air Dispersion Modeling Activities for the Boeing SSFL RFI Project

In 2008, Boeing used the open burn/open detonation dispersion model (OBODM) to evaluate the open burn (OB) and open detonation (OD) activities at the Area I Burn Pit RFI site and to evaluate the air dispersion pathway for extent delineation of constituents of potential concern (COPCs) in adjacent soil. OBODM was selected for evaluation of the Area I Burn Pit as a single OB/OD source. The current proposed air dispersion modeling effort is more comprehensive and will address several types of historical air emission sources.

RECOMMENDED APPROACH FOR AIR DISPERSION MODELING, BOEING RCRA FACILITY INVESTIGATION PROJECT, SANTA SUSANA FIELD LABORATORY, VENTURA COUNTY, CALIFORNIA

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4.0 Proposed Air Dispersion Modeling Approach Principal operations in Administrative Areas I and III of the SSFL included research, development, and testing of rocket engines and propulsion systems by Boeing. The vast majority of rocket engine testing and ancillary support operations occurred from the 1950s through the early 1970s, which were conducted by Rocketdyne (a Boeing predecessor) in support of various government programs. The frequency of rocket engine testing decreased significantly during the 1980s and 1990s and ceased in 2006.

The various types of potential air dispersion sources have been documented in the draft RFI reports submitted for each Boeing RFI group and RFI site. These include larger emission sources, such as rocket engine test stands and burn pits, and smaller emission sources, such as those that involved propellant testing or motor engine testing. Section 4.1 provides more detailed information on the various sources that may be subject to air dispersion modeling.

4.1 Identification of Sources In general, air emission sources can be categorized broadly into point sources (for example, from a stack), area sources, or volume sources (for example, a building with windows and doorways). Emissions from these sources can be described as buoyant (lighter than air, typically because of a higher temperature), dense (heavier than air), or neutral.

Air dispersion modeling is recommended for the large Boeing sources that had a greater potential for widespread distribution of chemical constituents. As the initial step in the Boeing air dispersion modeling approach, specific air emission sources within the Boeing RFI groups were identified. These sources were then evaluated to determine, for each source type, which sources would result in the worst‐case deposition results and warrant air dispersion modeling to assist in the data gap characterization. If the results from air dispersion modeling of these worst‐case sources indicate that impacts are minimal, then modeling the smaller, similar sources is not warranted.

Readily available historical data were reviewed for all identified sources using the decision criteria listed below, as depicted on Figure B‐1). All decision criteria are to be satisfied for the source to warrant air dispersion modeling.

Criteria 1 ‐ Source Type Based on Buoyancy: Buoyant sources have the potential to transport contaminants by air dispersion over large distances because they release plumes that are lighter than air. Dense and neutral sources, however, have a limited potential to transport contaminants by air dispersion because they release plumes that are greater than or equal to the density of air, thus increasing immediate settling of particulates and causing localized impacts (that is, the majority of impacts occur within a short distance of the source). It is anticipated that DQOs and soil sampling performed to characterize the extent of contamination in chemical use areas will identify contaminants transported limited distances from dense or neutral sources. As a result, only buoyant sources will be retained and considered for modeling (for example, rocket engine test stands).

Criteria 2 ‐ Potential for Dispersion: Buoyant sources with a high temperature and large initial plume radius have a greater potential for dispersion and are expected to transport contaminants by air dispersion over large distances. As the source temperature and/or initial plume radius decreases, the buoyancy and flow rate of emissions released decreases, resulting in a smaller potential for dispersion and more localized impacts. Similarly, uncontained sources have a greater potential for dispersion whereas the dispersion from contained sources would be greatly restricted by the sources’ surroundings. It is anticipated that DQOs and soil sampling performed to characterize the extent of contamination in chemical use areas will identify contaminants transported limited distances from less buoyant sources. As a result, buoyant sources with a greater potential for dispersion, which means a higher temperature, larger initial plume radius, and uncontained surroundings, generally will be retained and considered for modeling. Depending on site characteristics and available information, lesser mass and lower buoyancy sources may be considered for modeling based on professional judgement and consultation with DTSC.

Criteria 3 ‐ Emissions Constituents: Pollutants released are dependent on the fuel combusted or waste disposed. Only sources with toxic emission constituents will be considered for modeling. These toxics from combustion sources will largely be identified by reviewing available operational data and available site


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characterization data from RFI activities. Combustion modeling (POLU4WN) may be used to identify emissions constituents from certain sources. POLU4WN is a thermodynamically based combustion model used to predict emissions from the combustion of energetic materials such as propellants and explosives (Baroody, 1987; Baroody and Peters, 1990). POLU4WN may also be used to estimate particulate matter emissions from liquid fuel combustion. As additional information and sampling data are obtained through the RFI, they will be evaluated to identify when modeling of additional sources may be warranted to characterize the extent of COPCs in surface soil.

Criteria 4 ‐ Relative Mass of Emissions: For each source type considered, the potential impact for deposition correlates to the relative mass of emissions released by the source (that is, the more emissions released, the greater the potential impact for deposition). Therefore, within each source type, which would have similar types of emissions and COPCs, the source releasing the largest mass of emissions will be chosen as the source representing the worst‐case deposition results. This source will be modeled to represent all other sources within the source type. For example, the quantity of material released from a rocket engine test stand is a function of the engine’s thrust and specific impulse. Of the engines tested in the Group 1B ‐ Bowl Area RFI Site (Bowl Area) (Agency for Toxic Substances & Disease Registry [ATSDR], 1999), the Atlas engine has the largest thrust (Sutton, 2006) and, therefore, the largest potential for emissions from a single event. As a result, the Atlas engine will be modeled as the worst‐case rocket engine testing scenario and deemed representative of the rocket engine testing conducted in the Bowl Area of the SSFL. The results from modeling of the worst‐case source will be used as appropriate to assess potential impacts from other sources of the same type (for example, deposition contours from the worst‐case modeling can be overlain on other nearby source locations to provide a conservative indication of cumulative deposition impacts).

As previously discussed, each air emission source at Boeing will be evaluated for its potential for air dispersion using the criteria listed above, as depicted in Figure B‐1. As an outcome of this process, Boeing proposes to select a conservative and representative source for each source type to be modeled. For example, there are several rocket engines tested in the Bowl Area of the SSFL. Using the above decision criteria, the Atlas engine will be modeled as representative of the potential deposition impacts from rocket engine testing conducted in the Bowl Area.

The available information about potential emissions and deposition sources to the air is presented in Table B‐1. This information summarizes the range of testing activities reported at the different RFI sites; types of propellants, oxidizers, or energetic chemicals used or waste managed at these sites; and identification as a candidate for modeling based on the process outlined in Figure B‐1. Table B‐2 summarizes the Boeing air emission source types present at the SSFL, sorted by RFI site, which are proposed for modeling based on the Figure B‐1 process. A brief explanation of why each source is representative of the source type is also included in Table B‐2. The source types selected for modeling (Table B‐2) reflect a range of COPCs (rocket engine testing, incineration, open burning, and energetics testing). Note that this is a preliminary list that may be modified based on further and ongoing review of the available data. The results from sampling performed to characterize surface soils around the representative sources will be evaluated to identify when modeling of additional sources may be warranted to characterize the extent of COPCs in surface soil.

Based on the Figure B‐1 process, the following source types are not considered to have a significant potential for air dispersion and, therefore, are not proposed for modeling by Boeing at this time:

Small jet engines and motor engine testing

Rocket engine component testing, such as injectors and combustors

Testing occurring in enclosed structures

Projectile testing

Gun propellant testing

Tank venting

Demolition activities


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Regarding demolition, the impacts from this neutrally buoyant activity are expected to be relatively limited in horizontal extent with any emissions deposition occurring close to the building (as compared to the large buoyant area sources). These potential impacts are typically managed by engineering controls (such as dust suppression). Also, Figure 2 of the comprehensive DQO report (CH2M HILL, 2013a) allows for review of “demolition documentation and sampling” to identify if soil sampling in these areas is warranted. As a result, no modeling is proposed for demolition activities.

4.2 Model Options This section presents a brief overview of the air dispersion models that are considered potentially applicable for the SSFL and the proposed model for use in the air dispersion modeling.

4.2.1 Open Burn/Open Detonation Model OBODM is the only United States Environmental Protection Agency (USEPA) dispersion model available specific to OB/OD sources. OBODM is intended for use in evaluating the potential air quality impacts of the OB/OD of obsolete munitions and solid propellants. OBODM uses cloud/plume rise dispersion and deposition algorithms for instantaneous and quasicontinuous sources to predict the downwind transport and dispersion of pollutants released by OB/OD. A distinguishing feature of OBODM is that it contains internal libraries with emission factors and source characteristic information for selection of munitions emissions factors. The most recent version of OBODM is Version 1.3.24 and is available from USEPA’s Technology Transfer Network bulletin board. It was last updated in 2007.

While OBODM has algorithms for OB/OD events, it has the following limitations:

It is based on a 1992 version of USEPA’s Industrial Source Complex code, which was subsequently replaced by the American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) in 2005.

The complex terrain option cannot be used when calculating concentration with gravitational deposition occurring or gravitational deposition for particulates with appreciable settling velocities.

An older, gravitational settling method is used for dry deposition.

It cannot calculate wet deposition.

It allows for a limited number of gridded receptors.

The discrete receptors must be entered by hand, thus creating a greater opportunity for error.

It is limited to OB or OD sources.

4.2.2 American Meteorological Society/Environmental Protection Agency Regulatory Model AERMOD is the USEPA’s current preferred model for short‐range (that is, less than 50 kilometers [km]) air dispersion modeling. The most recent version of AERMOD is Version 12345, which is available from USEPA’s Technology Transfer Network bulletin board. It was last updated on December 10, 2012.

AERMOD is a steady‐state plume dispersion model for assessment of pollutant concentrations from a variety of sources. AERMOD simulates transport and dispersion from multiple point, area, or volume sources based on an up‐to‐date characterization of the atmospheric boundary layer. Sources may be located in rural or urban areas, and receptors may be located in simple or complex terrain. AERMOD accounts for building wake effects (that is, plume downwash) based on the PRIME building downwash algorithms. The model employs hourly sequential preprocessed meteorological data to estimate concentrations for averaging times from one hour to one year (also multiple years). AERMOD does not have the capability of modeling hot areas sources, such as OB/OD events.

4.2.3 CALPUFF Modeling System CALPUFF (Scire et al., 2000a‐b) is a multilayer, multispecies nonsteady‐state puff dispersion modeling system that simulates the effects of time‐ and space‐varying meteorological conditions on pollutant transport, transformation, and removal. CALPUFF is intended for use on scales from tens of meters (m) from a source to hundreds of km.


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CALPUFF includes algorithms for near‐field effects such as stack tip downwash, building downwash, transitional buoyant and momentum plume rise, rain‐cap effects, partial plume penetration, subgrid scale terrain and coastal interactions effects, and terrain impingement. CALPUFF also includes longer‐range effects such as pollutant removal due to wet scavenging and dry deposition, chemical transformation, vertical wind shear effects, overwater transport, plume fumigation, and visibility effects of particulate matter concentrations.

In CALPUFF, a sequence of puffs is used to approximate emissions. These puffs are tracked in time on the computational grid. Because no steady‐state approximation is made, CALPUFF calculates emissions at every time step. The characteristics of the CALPUFF model are as follows:

It is a nonsteady‐state puff model.

It accounts for causality.

It accounts for stagnation flows.

It is the standard to use with the diagnostic meteorological model (CALMET).

It includes special options for time‐varying, buoyant area sources (designed for forest fires).

It can calculate both wet and dry deposition.

CALPUFF also has post‐processing programs for estimating downwind concentrations and deposition fluxes of material emitted from modeled sources. CALPUFF is expected to predict impacts more accurately because, as a puff model, it enables movement of the puff to be controlled by multiple wind directions. The series of puffs emitted by a source will move downwind based on the spatially and time‐varying meteorological file created by CALMET. These puffs will continue to be modeled until either the meteorological data ends or the puffs travel a distance extending beyond the computational grid.

The distinguishing features of CALPUFF include:

The algorithms used by CALPUFF for buoyant area sources are appropriate for high‐temperature sources. Specifically, they do not use the Boussinesq approximation found in most air dispersion models. Furthermore, CALPUFF can model time‐varying buoyant area sources.

Because the CALMET meteorological preprocessor of the CALPUFF air dispersion modeling system generates a full three‐dimensional, time‐dependent meteorological field, the model is appropriate for use in situations with complex terrain and complex wind fields.

CALPUFF is the only model that can simultaneously model point and buoyant area sources.

CALPUFF does not have built‐in algorithms for OB/OD events; however, due to its ability to model time‐varying buoyant area sources, it has the flexibility to incorporate the characteristics of an OB or OD source.

4.2.4 Proposed Model Selection Boeing proposes to use the CALPUFF modeling system for the RFI project. The Gaussian plume models, such as OBODM and AERMOD, are derived from more general atmospheric dispersion equations by making the simplifying assumption of a continuous source under steady‐state conditions. Since standard meteorological data are available at a temporal resolution of one hour, this approximation is accurate for all distances within which impacts could occur within one hour. Gaussian plume models are considered sufficiently accurate for so‐called “near field” dispersion calculations. However, the further from the source, the more inaccurate the approximation becomes. For distances of 50 km or greater from the source, the Guideline for Air Quality Models (USEPA, 2005a) states that CALPUFF should be used. Furthermore, by a similar reasoning, the more complex the terrain, the less accurate the steady‐state approximation becomes.

CALPUFF is proposed by Boeing for the RFI project because the algorithms used by CALPUFF for buoyant area sources are appropriate for high‐temperature sources. Specifically, the algorithms do not use the Boussinesq approximation found in most air dispersion models of this type (such as AERMOD). Consequently, CALPUFF is the most appropriate system to use for modeling rocket engine testing and has applicability to other high‐temperature sources such as burn pits and incinerators. Furthermore, the CALMET meteorological preprocessor of the CALPUFF air dispersion modeling system generates a full three‐dimensional, time‐dependent


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meteorological field and is appropriate for use with complex wind fields, which exist in areas like the SSFL due to complex terrain and varying topography. CALPUFF is also more appropriate to capture non‐steady‐state, time‐varying dispersions from large buoyant area sources than are Gaussian plume models (such as AERMOD), which make steady‐state approximations.

Unlike any other USEPA‐approved air dispersion model, CALPUFF can be used to model buoyant area sources and point sources. The use of CALPUFF will allow for consistency in evaluations of the area and point sources currently proposed for modeling.

CALPUFF can be used to model each source unit separately using a representative event size. For each source modeled, available historical data were reviewed to identify the representative event for modeling purposes. These data will also be reviewed to define the parameters needed to model the emissions from those sources, as summarized in Section 5.3. In the absence of site‐specific data, assumptions will be made based on available standard methods, such as the USEPA’s AP‐42, Compilation of Air Pollutant Emission Factors (USEPA, 1995).

As noted in Section 3.0, Boeing used OBODM in 2008 to evaluate the OB/OD activities at the Area I Burn Pit RFI site located in Group 1B and to evaluate the air dispersion pathway for extent delineation of COPCs in adjacent soil. OBODM was selected for evaluation of the Area I Burn Pit because: (1) it is an USEPA air dispersion model designed specifically for OB/OD activities; (2) it has a built‐in database of burn rates and heat contents of common OB/OD materials; (3) it handles buoyant area sources; (4) it has algorithms to estimate an initial volume source, and; (5) it can provide analysis only for one OB/OD source. In the currently proposed analysis, the CALPUFF modeling system is being proposed due to the following changes in the overall modeling approach: (1) multiple sources are now proposed for modeling, and (2) evaluation is needed for potential impacts to all of the SSFL, which has complex terrain and hence complex wind fields. The heat content, burn rate, and initial volume source size information from OBODM and/or from other independent sources will be used as input to the CALPUFF modeling system as appropriate.

5.0 CALPUFF Input Parameters 5.1 CALMET Meteorological Files and CALPUFF Receptor Grid The CALMET meteorological preprocessor is proposed for use with the CALPUFF modeling system to generate five years of site‐specific wind fields for a computational grid that is approximately 75 km by 75 km and is centered on the SSFL. The CALPUFF dispersion modeling will use an appropriately sized receptor grid, approximately 20 km by 20 km. A detailed description of these activities is provided in the following subsections.

5.1.1 Meteorological Data A comprehensive meteorological dataset will be developed using the CALMET pre‐processor for the CALPUFF modeling system. CALMET uses a variety of data sources, which are discussed in the following subsections, to create wind fields representative of the complex flows resulting from the complex terrain surrounding the SSFL.

CALMET is a meteorological model which develops hourly wind and temperature fields on a three‐dimensional gridded domain. Associated two‐dimensional fields, such as mixing height, surface characteristics, and dispersion properties, are also developed by CALMET (Scire et al., 2000a). To develop these various fields, CALMET consists of a diagnostic wind field module and micrometeorological modules for overwater and overland boundary layers (Scire et al., 2000a):

The diagnostic wind field module uses a two‐step approach to compute the wind fields. In the first step, an initial guess wind field is estimated using prognostic data such as mesoscale model (known as MM5) data. In the second step, the initial guess wind field is refined using terrain and observational data. Observational data are upper‐air and surface meteorological data (including onsite SSFL data). Using an inverse‐distance‐squared interpolation scheme, the observational data are heavily weighted in the vicinity of the observational station location, whereas the initial guess wind field is applied to regions with no observational data. The inverse‐distance‐squared interpolation scheme requires the identification of a radius of influence (ROI). The ROI is applied equally around each station and is selected based on stations’ proximity to terrain, other stations, etc.


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The RFI project air dispersion modeling will utilize an ROI of 5 km, indicating that data measured at each observational station will greatly influence the initial guess wind field within 5 km of the station itself.

The micrometeorological modules use an energy budget method for overland surfaces and a profile method for overwater surfaces. The energy budget method is based on an energy balance of heat fluxes and parameterization of unknown variables. The profile method is based on air‐sea temperature differences and overwater wind speeds.

Computation of the temperature field is based on an interpolation of upper‐air and surface temperature data as well as an estimate of the local convective mixing depths. The influence of each station’s data is based on the same inverse‐distance squared interpolation scheme used by the diagnostic wind field module.

The Guideline on Air Quality Models (USEPA, 2005a) recommends the use of one year of onsite or five years of representative offsite meteorological data to support dispersion modeling. For the Boeing RFI project air dispersion modeling, five years of onsite and representative offsite meteorological data will be used. While the Guideline on Air Quality Models suggests that onsite meteorological data are sufficient for air dispersion modeling (USEPA, 2005a), these data might not be fully representative of meteorological conditions for all of the air emission sources proposed for modeling. For example, the prominent terrain features may not be positioned similarly around the locations of interest and the location of the onsite meteorological station, which may lead to different wind patterns. Therefore, the meteorological data measured onsite may not be fully representative of each modeled source location. In these cases, the onsite meteorological data will be used in conjunction with the offsite meteorological data, and five years (instead of one year) will be modeled to evaluate a larger range of possible meteorological conditions. This approach is consistent with the recommendations for complex terrain in the Meteorological Monitoring Guidance for Regulatory Modeling Applications (USEPA, 2000). Figure B‐3 displays the location of different stations (relative to the location of the SSFL) that may be used to obtain offsite meteorological data, which are discussed in the following subsections.

All meteorological data will be evaluated for completeness and will span the years 2002 through 2006, which corresponds to the most recent, readily available onsite data, as recommended in the Guideline on Air Quality Models (USEPA, 2005a). Guidelines for evaluating data quality, discussed in Section 8.3.3.2 of the Guidelines for Air Quality Models (USEPA, 2005a) and described in further detail in Meteorological Monitoring Guidance for Regulatory Modeling Applications (USEPA, 2000), will be consulted prior to using meteorological data for modeling of specific SSFL sources.

Mesoscale Model Data. Five years of MM5 data, corresponding to the available years of onsite data (2002 through 2006), will be used for the Boeing RFI project air dispersion modeling. The use of MM5 data allows incorporation and better representation of certain regional features of the flow field that may not be captured in the surface observational data, such as a three‐dimensional wind field rather than a two‐dimensional wind field (Scire et al., 2000a). As noted previously, the MM5 data are used to create the initial guess wind field.

The MM5 data, purchased from Alpine Geophysics,1 will be provided in 36‐km grid size for the entire United States (University Corporation for Atmospheric Research, 2010). Prior to distribution, Alpine Geophysics will quality‐assure the MM5 data by comparing the modeled results with available observations and synoptic weather charts. For use in the RFI project air dispersion modeling, the purchased data will be processed to extract the MM5 grid points within the required CALMET domain, which is specified in Table B‐3.

Upper‐Air Data. Within CALMET, upper‐air‐sounding data are vertically averaged and time‐interpolated to compute components of a constant domain‐mean wind field, which influences the initial guess wind field within CALMET (Scire et al., 2000a). For the Boeing RFI project air dispersion modeling, five years of upper‐air data, corresponding to the available years of onsite data (2002 through 2006), will be obtained from the National Oceanic and Atmospheric Administration (NOAA)/Earth System Research Laboratory radiosonde database.2 This database, created at the Forecast Systems Laboratory (FSL), combines radiosonde observations separately

1 http://www.alpinegeophysics.com/. 2 http://esrl.noaa.gov/raobs/.


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recorded and quality‐controlled by the National Climatic Data Center (NCDC) and the Global Telecommunication System. The procedures by which the FSL creates this database, as well as the additional quality control procedures used by the FSL, are documented in A Hydrostatically Consistent North American Radiosonde Data Base at the Forecast Systems Laboratory, 1946‐Present (FSL, 1992).

For the Boeing RFI project air dispersion modeling, the downloaded data is measured at the Miramar Upper Air Station, located in Miramar, California. Although this station is approximately 200 miles south of the SSFL, the station’s measured data are representative of the SSFL conditions due to the proximity of both locations to the coast (less than 20 miles for both the Miramar Upper Air Station and the SSFL). Per the Meteorological Monitoring Guidance for Regulatory Modeling Applications (USEPA, 2000), upper‐air measurements are generally representative of large spatial domains because measurements taken aloft exhibit less site‐to‐site variability than those measured near the surface. Data from the two upper‐air stations located closer to the SSFL than the Miramar Upper Air Station have been considered but have been determined not to best represent the SSFL conditions because of their distances from the coast.

The downloaded upper‐air data, or twice‐daily sounding data, will provide vertical profiles of wind speed, wind direction, temperature, pressure, and elevation. At a minimum, CALMET requires twice‐daily sounding data at the standard sounding hours of 0 and 12 Greenwich Mean Time (GMT) (Scire et al., 2000a). To meet this minimum requirement, missing data will be interpolated from the surrounding data values, as recommended in the Meteorological Monitoring Guidance for Regulatory Modeling Applications (USEPA, 2000). Per the recommendations in A User’s Guide for the CALMET Meteorological Model (Version 5) (Scire et al., 2000a):

If an entire sounding at 0 or 12 GMT is missing, the 0 or 12 GMT sounding from the previous day will be copied.

If an entire day of data are missing, the previous day’s data will be copied.

If several days of data are missing, the missing data will be extracted from the available MM5 data.

Onsite Meteorological Data. Onsite meteorological data are used to influence the initial guess wind field within CALMET within the area surrounding the SSFL (Scire et al., 2000a). For the Boeing RFI project air dispersion modeling, the most recent five years of readily available, hourly onsite meteorological data (2002 through 2006) will be provided by Boeing. These data were collected at a meteorological tower located in Administrative Area IV of the SSFL.

Prior to use in CALMET and selection of offsite meteorological data, onsite data have been evaluated for completeness. According to USEPA regulatory guidance, meteorological data are complete when at least 90 percent of the data are accepted or present (Atkinson and Lee, 1992). The five years of onsite meteorological data were evaluated for the number of missing values for each meteorological parameter. The percent completeness for each parameter evaluated is presented in Table B‐4. Based on this analysis, all five years of data were found to be complete by regulatory standards. Missing data will be supplemented with data from the Miramar Upper Air Station, as recommended in the Guideline on Air Quality Models and the Meteorological Monitoring Guidance for Regulatory Modeling Applications (USEPA, 2000 and 2005a), because the upper‐air data contains rural and urban mixing heights. The meteorological data used in the RFI project air dispersion modeling will include wind speed, wind direction, dry bulb temperature, stability class, and rural and urban mixing heights.

Surface Data. In addition to the upper‐air data, CALMET also uses hourly surface meteorological data to influence the initial guess wind field (Scire et al., 2000a). These hourly surface meteorological data are extrapolated vertically using similarity theory to provide more accurate wind field estimates near each station location that are not solely dependent on the upper‐air station (Scire et al., 2000a), which is located more than 200 miles from the SSFL. Hourly surface meteorological data are also used to compute the overland boundary layer parameters (Scire et al., 2000a).

For the Boeing RFI project air dispersion modeling, five years of hourly surface meteorological data, corresponding to the available years of onsite data (2002 through 2006), will be taken from nearby National Weather Service


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(NWS) surface stations, available for download from the NCDC.3 Following the recommendations of the Guideline on Air Quality Models (USEPA, 2005a),4 surface stations will be selected for the Boeing RFI project air dispersion modeling by canvassing the area surrounding the SSFL to identify NWS surface stations residing within the meteorological grid. This will be completed by reviewing the list of NWS surface stations made available by the NCDC. NWS surface stations within the meteorological grid, described in Section 5.1.2, are considered to provide data representative of the SSFL’s meteorological conditions given their proximity to the coast and complex terrain. The quality control procedures used by the NCDC to prepare this database are documented in The Quality Control of the Integrated Surface Hourly Database (NCDC, 2012a).

The 2002 and 2003 data files are available in the DatSav data format, while 2004, 2005, and 2006 data files are available in the ISH data format. Regardless of the format in which data are downloaded, the available data files will be converted to the CD144 format for processing in CALMET. Following the data file conversion, one data file for each year will be created by compiling the data from the available surface station data files. The surface station data files available for each year and to be used in this analysis are displayed in Table B‐5 and are included on Figure B‐3.

Unlike the onsite meteorological data used, the surface data do not include stability class or rural or urban mixing heights; however, the data do include the wet bulb temperature, relative humidity, and cloud cover. At a minimum, CALMET requires one complete data set for every hour; in other words, one surface station could have a missing hour if another surface station had data for that same hour (Scire et al., 2000a). Data missing from the available surface station records will be interpolated from surrounding data values, as recommended in the Meteorological Monitoring Guidance for Regulatory Modeling Applications (USEPA, 2000).

Precipitation Data. Five years of hourly precipitation data, corresponding to the available years of onsite data (2002 through 2006), will be taken from precipitation stations included in the modeling domain. The use of precipitation data allows CALPUFF to use the wet removal algorithm, which computes wet deposition impacts (Scire et al., 2000a).

The precipitation data used in this analysis will be downloaded from the NCDC.5 The data collection and quality control procedures used by the NCDC to prepare this database are documented in Hourly Precipitation Data Documentation (NCDC, 2012b). The precipitation station data files available for each year and to be used in this analysis are displayed in Table B‐6 and are included on Figure B‐3. Data substitution will not be performed because CALMET does not require 100 percent completeness for precipitation data (Scire et al., 2000a).

Buoy Data. Buoy data, including air‐sea temperature differences, air temperatures, relative humidities, and overwater mixing heights, are used to estimate overwater boundary layer parameters in CALMET. The overwater boundary layer parameters provide an additional refinement for coastal conditions. Due to the SSFL’s proximity to the coast, buoy data will be used for the RFI project air dispersion modeling.

Five years of hourly buoy meteorological data, corresponding to the available years of onsite data (2002 through 2006), will be downloaded from the National Data Buoy Center6 as measured at buoys near the SSFL. The National Data Buoy Center follows the procedures in the National Oceanic and Atmospheric Administration Information Quality Guidelines (NOAA, 2012) to quality‐control disseminated data.

Two buoy stations, displayed on Figure B‐3, will be used for the five years of the RFI project air dispersion modeling:

E. Santa Barbara – 12NM Southwest of Santa Barbara CA (Station ID 46053)

Santa Monica Basin – 33NM West Southwest of Santa Monica CA (Station ID 46025)

3 http://www.ncdc.noaa.gov/. 4 The Guideline on Air Quality Models recommends the use of NWS surface station data because such data have been subjected to the required quality assurance procedures. Although data from universities, the Federal Aviation Administration, military stations, industrial stations, and pollution control agencies may be used, their use is recommended if the data are proven to be equivalent in accuracy and detail to the NWS surface station data (USEPA, 2005a). 5 http://www.ncdc.noaa.gov/. 6 http://www.ndbc.noaa.gov/rmd.shtml.


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CALMET requires 100 percent completeness for buoy data (Scire et al., 2000a). To meet this requirement, missing data will be assumed to be consistent from the previous hour, as recommended in the Meteorological Monitoring Guidance for Regulatory Modeling Applications (USEPA, 2000). Table B‐7 shows the percent of data to be substituted from each buoy station for each of the five years modeled.

Coastal Boundary File. Because the SSFL is located only 20 miles from the coast, modeled plumes may experience abrupt spatial changes in meteorological and dispersion conditions at the coastline (Earth Tech, Inc., 2006). To improve the transition from overland to overwater meteorological conditions, a binary coastal boundary file will be used in addition to the above data sources. This high‐resolution file, containing a series of x‐ and y‐coordinates along the California coast at a resolution smaller than 250 m, provides a definitive outline of the coast (further differentiating between the water and land boundaries), allowing for better definition of the coastal/land turbulence influence and a more accurate characterization of the thermal internal boundary layers. This subgrid thermal internal boundary layer option will be used within CALMET to better resolve the relationship between the coastline and source locations during periods conducive to onshore fumigation events (Earth Tech, Inc., 2006).

5.1.2 Receptor Grid The CALPUFF modeling domain will be approximately 20 km by 20 km and will be centered over the approximate site location. Since CALPUFF is a puff model, it is possible for puffs to travel off the grid and then return to the domain of interest. Therefore, a larger meteorological grid, approximately 75 km by 75 km, will be used to create a buffer. While the MM5 data have 36‐km grid cells, smaller grid spacing can be used for the modeling to capture the effects of the complex topography. The CALMET preprocessor contains algorithms to adjust the MM5 data to account for terrain effects. A grid spacing of approximately 250 m is proposed to evaluate for numerical artifacts; topographic effects will be captured within the 250‐m grid cell by averaging data read at nodes placed every 90 m. This proposed grid spacing is intended to create a balance between resolving the terrain at the SSFL and not selecting a grid that is smaller than the input data (primarily the MM5 data) will support.

A receptor grid network, a subset of the meteorological grid cells, will be used to locate the deposition impacts resulting from each air emission source modeled. The receptor grid network used to model deposition impacts over the entire modeling domain will include receptors spaced 125 m apart. As necessary, a refined grid, with receptors spaced 25 m apart, will be used to model deposition impacts over a smaller area to better depict results near the air emission source modeled.

5.1.3 Terrain and Land Use CALPUFF uses data files that incorporate the terrain and land use characteristics of the project area. Terrain data for the SSFL will be obtained from the 1:250,000 scale digital elevation model with 90‐m resolution at United States latitudes. These files will account for the variations in hills and valleys that characterize the SSFL. Aerial images of each source location will also be reviewed to verify that the terrain surrounding the source location does not vary significantly at 90‐m intervals.

Land use and land cover data, in the Lambert azimuthal map projection, will be used to provide surface properties on up to 14 categories of land use, such as urban, agricultural, or forest, within the modeling domain. Surface properties, such as albedo, Bowen ratio, roughness length, and leaf area index, will be computed from the land use values. Missing land use data will be filled with a value that is appropriate for the missing area. Descriptions of these surface properties are as follows:

Albedo is the fraction of total incident solar radiation reflected by the surface without absorption; typical values range from 0.1 for thick deciduous forests to 0.9 for fresh snow (USEPA, 2004).

Bowen ratio is an indicator of surface moisture equal to the ratio of the heat caused by conduction and convection (sensible heat flux) to the heat moved by water evaporating and condensing higher up in the atmosphere (latent heat flux); typical values range from 0.1 over water bodies to 10 for deserts (Scire et al., 2000a).


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Roughness length relates to the height of obstacles to the wind flow and is, in principle, the height at which the mean horizontal wind speed is zero (USEPA, 2004); typical values range from 0.0001 m over calm water to 1 m over a forest or urban area (Scire et al., 2000a).

Leaf area index is a forest measurement of leaf area in a given section of ground area; typical values range from 0 over water to 7 in a forest (Scire et al., 2000a).

5.1.4 Wind Impacts The SSFL is dominated by winds from two directions: from the northwest and from the southeast. A wind rose showing these wind directions, generated using onsite data collected in Administrative Area IV of the SSFL, is presented in Figure B‐2. The elevation of the terrain ranges from 1,174 feet to 2,254 feet above mean sea level. The elevation ranges for each of the source types proposed for modeling are summarized below:

Bowl Area Rocket Engine Testing: elevations of the three test stands range from 1,824 feet to 1,880 feet.

Canyon Rocket Engine Testing: elevations of the four test stands range from 1,972 feet to 1,998 feet.

B359 Energetics Testing: elevations of the testing locations (within former Buildings 1359 and 1741) range from 1,898 feet to 1,904 feet.

Happy Valley North Incinerator: elevation is approximately 1,940 feet.

Area I Burn Pit: elevation of the Thermal Treatment Facility, where the principal OB activities occurred within the Area I Burn Pit, is approximately 1,760 feet.

STL‐IV Intercontinental Ballistic Missile Testing: elevations of the three test modules range from 1,748 feet to 1,756 feet.

The processed CALMET data incorporates the wind patterns as indicated in the wind rose and the topographic effects of the terrain to provide a representative meteorological file.

5.2 CALPUFF Modeling Options The preliminary meteorological, terrain, and pollutant modeling options proposed to identify deposition are listed in Table B‐8.

5.3 Source Characteristics Using the screening criteria discussed in Section 4.1, one source will be modeled within each source type and will be considered representative of the other sources within that source type at a site. However, if geographic differences would result in different modeling characteristics, more than one source would warrant modeling for the same source type. For example, because rocket engine testing was performed at two RFI sites (Canyon and Bowl Area), one representative source will be identified for each testing area to capture the areas’ geographic differences that may lead to significantly different dispersion characteristics.

Table B‐9 presents the sources and modeling parameters that will be used to model each source type identified in Table B‐2. The specific parameters and source characteristics for each source will be further developed during further and ongoing review of available data. Most of these parameters have been identified for the Bowl Area rocket engine testing and are described in Section 5.3.1 to provide an example of how the necessary modeling parameters will be developed for the remaining source types proposed for modeling.

5.3.1 Example Source Evaluation: Bowl Area Rocket Engine Testing Scenario The Bowl Area of SSFL was used for large rocket engine and engine component testing from 1954 to 1960. There were three test stand locations within the Bowl Area that tested the following programs: Atlas, Navaho, and Redstone (ATSDR, 1999). Liquid oxygen (LOX) and kerosene were used to test the Navaho and Atlas engines, whereas LOX and ethanol were used to test the Redstone engine (ATSDR, 1999). Because the total number of tests performed within the Bowl Area is known, as shown in Table B‐9, one rocket engine testing scenario was


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chosen as representative of SSFL operations in the Bowl Area to be modeled at one representative test stand location.

As shown in Table B‐9, the Atlas engine program was chosen as the representative rocket engine testing scenario for the Bowl Area. This scenario was considered the most significant contributor to the release of particulate matter and thus the most representative, worst‐case scenario for the following reasons:

Kerosene and LOX were fuels that were frequently used throughout the test stand areas, with the potential for toxic emissions (Criteria 3).

The Atlas engine had approximately 564,000 pounds of thrust (Sutton, 2006), making it the largest engine tested in the Bowl Area (Criteria 2 and 4).

Therefore, while there were multiple rocket engines tested at the Bowl Area, the Atlas engine is a worst‐case scenario that is representative of the range of testing activities. The Atlas engine tests used the same fuels as other engine testing performed at the SSFL and would, therefore, potentially produce emissions comparable with other testing. The Atlas engine thrust is the largest tested at the Bowl Area and would, therefore, produce larger emissions with a greater extent of dispersion and deposition. As discussed in Section 4.1, additional information and sampling results will be reviewed as they become available to confirm that the modeling results are sufficient to help identify sampling locations that achieve the DQOs.

The specific modeling parameters for the Atlas engine that will be used to model the potential deposition impacts associated with the Bowl Area sources are listed in Table B‐10.

CALPUFF Options for Bowl Area Rocket Engine Testing Scenario. A model is an approximation of an actual emission source. To accurately model a buoyant area source, source characteristics were converted into representative modeling parameters. Although the modeling will be done using CALPUFF for the reasons previously discussed, OBODM (Bjorklund et al., 1998) has the technical equations to convert source characteristics into modeling parameters for buoyant area sources. Therefore, the following modeling parameters were calculated using the specific characteristics of the Atlas engine and the buoyant area source equations in OBODM and are presented in Table B‐11:

Plume Temperature: temperature of the plume cloud immediately after the initial burn, including the initial entrainment of air

Effective Rise Velocity: rate at which the initial plume rises based on the buoyant flux

Effective Plume Radius: radius of plume after the initial burn, including the initial entrainment of air

Effective Release Height: midpoint of the vertical spread of the plume after the initial burn, including the initial entrainment of air

Sigma Z: initial dispersion of the plume in the along‐wind direction

Bowl Area Rocket Engine Testing Scenario Assumptions. The following assumptions were made in preparing the data that will be used to model the Bowl Area rocket engine testing scenario; many of these assumptions will be applicable to the remaining sources to be modeled at the SSFL:

Emission events will be allowed during all hours to cover all possible testing scenarios (that is, day and night testing) performed in the Bowl Area.

Only one slug per hour is released from this source, assuming all rocket engine testing emissions are released at once at the beginning of every hour.

The Atlas engine fueled by a mixture of LOX and rocket propellant‐1 (RP‐1) is assumed representative for rocket engine testing events conducted in the Bowl Area. RP‐1 was assumed to be the type of kerosene fuel consumed by the Atlas engines based on historical fueling information (CH2M HILL, 2009).


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The Atlas engine propellant consumption per test was assumed to be the sum of the booster nozzle and the sustainer nozzle consumption rates during a 190‐second test (Sutton, 2006; Glasgow, 2010). The detailed calculations are included in Attachment B‐1.

The test duration(s) and propellant heat content of an RD‐170 engine test fueled by LOX and RP‐1 were assumed representative of Atlas engine tests. The heat content accounts for noise suppression as the presence of deionized water suggested the use of water during engine tests for noise suppression (CH2M HILL, 2009).

A 10‐micron particulate matter (PM10) emission factor was assumed comparable to that for the RD‐170 engine and was scaled by the ratio of the Atlas engine fuel burn rate to the RD‐170 engine fuel burn rate. The detailed calculations are included in Attachment B‐1.

The plume temperature, effective rise velocity, effective plume radius, effective release height, and Sigma Z (parameters required for modeling a buoyant area source in CALPUFF) are calculated based on the intrinsic properties of the propellant as well as assumed parameters used by OBODM.

As described previously, modeling initially will be performed assuming one test every hour of every year to conservatively model potential deposition. This will allow modeling to account for possible worst‐case meteorological conditions during the years modeled, thereby allowing consideration of diurnal differences in meteorological conditions and capture of the worst‐case dispersion. Because this frequency is impractical from an operations perspective, the 5‐year average results will be scaled to better reflect the actual operational history at an engine test stand. In the absence of site‐specific operations logs, a range of operating frequencies will be assumed. The sensitivity of resulting deposition fluxes to the operating frequency will be evaluated in the modeling report for each individual source.

6.0 Reporting and Uncertainty Evaluation 6.1 Reporting The air dispersion modeling will be conducted as described in the previous section to support the comprehensive DQO report (CH2M HILL, 2013a). In accordance with DQO Table 2, Study Question #3, air dispersion modeling will be conducted to evaluate the potential spatial distribution of chemical constituent impacts to surface soil resulting from deposition from historical operations. Deposition concentrations (relative values, not specific or absolute concentrations) will be presented with contour maps indicating deposition patterns. Overlays will be provided to show areas of overlap of the predicted deposition from each source modeled.

Each addendum to the Boeing Master RFI Data Gap Work Plan, Santa Susana Field Laboratory, Ventura County, California (CH2M HILL, 2013b) for each Boeing RFI subarea will include the response to DTSC comments on the draft RFI report, the comprehensive DQO evaluation, and the proposed sampling and analysis plan for the identified data gaps. If a specific work plan addendum includes sources that should be modeled (as derived from the list in Section 4.1 and from the DQO process), a summary of the air dispersion modeling performed for the identified source(s) will be included as an appendix to the work plan addendum.

Air dispersion modeling will aid in the selection of soil sampling locations to address identified data gaps in accordance with DQO Table 2, Study Question #2. Surface soil samples will be collected, as needed, from the modeled air deposition locations and submitted for laboratory analysis to evaluate the nature and extent, and fate and transport, of constituents. If the air dispersion modeling results indicate that soil sampling is needed and existing data are not available, then soil sampling will be proposed in the work plan addendum to address the identified data gaps.

6.2 Uncertainty Evaluation It is important to note that there will be uncertainties in several of the assumptions used in the air dispersion modeling. Modeling assumptions where there may be uncertainties include: the total amount of materials disposed, the number of events, and the amount of materials disposed per event. Additionally, there is limited


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particle size distribution data available for the various rocket engine testing programs. Consequently, there will be uncertainty in the deposition range and values calculated. Therefore, it is most appropriate to use the deposition values calculated as indicators of relative levels of deposition, rather than as specific or absolute amounts of deposition. The need for sampling and the extent of sampling will be based on the relative levels of deposition. Sensitivity analyses for the key modeling input parameters may be conducted to address uncertainty when site‐specific data are unavailable.

Parameters identified as having high levels of uncertainty (due to limited documentation, and due to their influence in estimating dispersion) will be evaluated further by performing sensitivity cases. The sensitive parameters will differ between sources; therefore, specific parameters and ranges of values to be evaluated in a sensitivity analysis will be conducted on a case‐by‐case basis and documented in the modeling reports for each individual source. Results of these sensitivity analyses, if performed, will be documented in the air dispersion modeling report included as an appendix to the work plan addenda (where appropriate). This uncertainty will also be evaluated and accounted for in identifying sample locations proposed in the work plan addenda.

As described in Section 5.1.1, a comprehensive meteorological data set has been compiled for all modeling activities at the SSFL site. Use of this comprehensive data set is intended to provide consistency across different source locations. However, the modeling reports will present a qualitative evaluation of how selection of the meteorological data may affect modeling results. In addition, the surface wind field generated by CALMET will be extracted for selected sites as appropriate and configured into a wind rose, for comparison with the modeling results.

7.0 Overall Summary of Air Dispersion Modeling Approach In summary, the proposed air dispersion modeling approach for the Boeing RFI project will evaluate the potential spatial distribution of chemical constituent impacts to soil resulting from particle deposition from historical operations. The air dispersion modeling will be conducted at selected sources to support the comprehensive DQO evaluation and, if appropriate, to aid in the selection of surface soil sampling locations to address identified data gaps.

Boeing proposes to use the CALPUFF modeling system for the RFI project. CALPUFF is the most appropriate system for modeling high‐temperature sources, for areas with complex terrain, and for nonsteady‐state, time‐varying dispersions from large buoyant area sources.

At this time, Boeing proposes to perform air dispersion modeling on representative large buoyant area sources (that is, rocket engine testing, energetics testing, intercontinental ballistic missile testing, and OB activities) and representative large point sources (that is, incineration) to address data gaps. It is possible that fewer sources or additional source types may be evaluated in the future based on further and ongoing review of available data and the outcome of the initial modeling activities. Following review by DTSC, this air dispersion modeling approach will be applied to satisfy the comprehensive DQO process.

8.0 References Agency for Toxic Substances & Disease Registry (ATSDR). 1999. Draft Preliminary Site Evaluation, Santa Susana

Field Laboratory (SSFL), Ventura County, California. December.

Atkinson, D. and R. Lee. 1992. Procedures for Substituting Values for Missing NWS Meteorological Data for Use in Regulatory Air Quality Models. Available online at: http://www.epa.gov/scram001/surface/missdata.txt. Accessed December 10, 2010. Updated July 1992.

Baroody, E.E. 1987. Computer Predictions of Pollution Products from Open Burn and Detonation of Navy Explosives and Propellants. Naval Surface Weapons Center/White Oak Ordnance Environmental Support Office, Naval Ordnance Station. Indian Head, Maryland.


B-15

Baroody, E.E. and S.T. Peters. 1990. Heat of Explosion, Heat of Detonation and Reaction Products: Their Estimation and Relation to the First Law of Thermodynamics. IHTR 1340; Naval Ordnance Station. Indian Head, Maryland.

Bjorklund, Jay R., James F. Bowers, Gregory C. Dodd, and John M. White. 1998. Open Burn/Open Detonation Dispersion Model (OBODM) User’s Guide, Volume 1, User’s Instructions, DPG Document No. DPG‐TR‐96‐008a. Prepared for U.S. Army Dugway Proving Ground, West Desert Test Center. Meteorology & Obscurants Division. February. Model revision May 15, 2003.

CH2M HILL. 2009. Draft Group 1B – Southern Portion of Area I RCRA Facility Investigation Report, Santa Susana Field Laboratory, Ventura County, California, Volume VII, Appendix E. September.

CH2M HILL. 2013a. Comprehensive Data Quality Objectives, Santa Susana Field Laboratory, Ventura County, California. Technical Memorandum. March.

CH2M HILL. 2013b. Master RFI Data Gap Work Plan, Santa Susana Field Laboratory, Ventura County, California. March.

Earth Tech, Inc. 2006. Development of the Next Generation Air Quality Models for Outer Continental Shelf (OCS) Applications. Final Report: Volume 2 – CALPUFF Users Guide (CALMET and Preprocessors). March.

Forecast Systems Laboratory (FSL). 1992. A Hydrostatically Consistent North American Radiosonde Data Base at the Forecast Systems Laboratory, 1946‐Present. August.

Glasgow, Jason/CH2M HILL. 2010. Personal communication with Beth Vaughan/CH2M HILL. September 23.

MWH. 2009. Group iA – Northeastern Portion of Area I RCRA Facility Investigation Report, Santa Susana Field Laboratory, Ventura County, California. February 2009.

Mitchell, W.J. and J.C. Suggs. 1998. Emission Factors for the Disposal of Energetic Materials by Open Burning and Open Detonations. U.S. Department of Defense. August.

National Aeronautics and Space Administration. 1994a. Determination of Input Values for Rocket Exhaust Effluent Diffusion Model (REEDM) Modeling for Testing of an RD170 Engine. Memorandum for Record. March.

National Aeronautics and Space Administration. 1994b. Estimates of Rocket Exhaust Emission Factors for the RD‐170 Engine Test Program. Memorandum for Record. April.

National Climatic Data Center (NCDC). 2012a. The Quality Control of the Integrated Surface Hourly Database. Available online at: http://www1.ncdc.noaa.gov/pub/data/inventories/ish‐qc.pdf. Accessed October 19, 2012.

NCDC. 2012b. Hourly Precipitation Data Documentation. Available online at: feetp://feetp.ncdc.noaa.gov/pub/data/cdo/documentation/PRECIP_HLY_documentation.pdf. Accessed October 22, 2012.

National Oceanic and Atmospheric Administration (NOAA). 2012. National Oceanic and Atmospheric Administration Information Quality Guidelines. Available online at: http://www.cio.noaa.gov/ Policy_Programs/IQ_Guidelines_011812.html. Accessed October 22, 2012.

Scire, J.S., F.R. Robe, M.E. Fernau, and R.J. Yamartino. 2000a. A User’s Guide for the CALMET Meteorological Model (Version 5). January.

Scire, J.S., D.G. Strimaitis, and R.J. Yamartino. 2000b. A User’s Guide for the CALPUFF Dispersion Model (Version 5). January.

Sutton, G.P. 2006. History of Liquid Propellant Rocket Engines. American Institute of Aeronautics and Astronautics, Virginia.

Sutton, G.P. and O. Biblarz. 2010. Rocket Propulsion Elements, Eighth Edition. John Wiley & Sons, Inc., New Jersey.


B-16

United States Environmental Protection Agency (USEPA). 1995. Compilation if Air Pollution Emission Factors. AP‐42, Fifth Edition. January.

USEPA. 2000. Meteorological Monitoring Guidance for Regulatory Modeling Applications. EPA‐454/R‐99‐005. February.

USEPA. 2004. User’s Guide for the AERMOD Meteorological Preprocessor (AERMET). EPA‐454/B‐03‐002. November.

USEPA. 2005a. Guideline on Air Quality Models. 40 CFR Part 51, Appendix W. November.

USEPA. 2005b. Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities. Final. OSWER, EPA 530‐R‐05‐0006. September.

University Corporation for Atmospheric Research. 2010. MM5 Community Model. Available online at: http://www.mmm.ucar.edu/mm5/mm5‐home.html. Accessed September 28, 2010.

Tables

TABLE B-1Selection of Air Emissions Sources for Modeling at the Santa Susana Field LaboratoryRecommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County California

Group RFI SiteSource Type

Source Name

Location/Test Stand Duration Fuel Oxidizer

Testing Programs Comments Sources

Selected for Modeling?

Rationale (per Figure B-1)

Test Stand TRE-1

Bldg 1717 1954-1963

Test Stand TRE-2 Bldg 1718 1955-1960

Test Stand TRE-3 (3A

and 3B)Bldg 1719 1957-1968

B-1 Jet engine test stand

Prototype Jet Engine Test Stands 1-4

Bldgs 1781 (TS 1), 1782 (TS 2), 1783 (TS 3), and 1788 (TS 4)

early 1950s through mid-

1970sJP-4 NA

Prototype Jet Engine Test Stands 1-4 (for Lancer B-1 bomber and other aircraft. Test Stand 1 [slosh testing], 2 [leakage testing], 3 [pressure testing], 4 (exotic fuels).

Exotic fuels thought to be hydrazine and pentaborane, but not documented, according to the RFI Report.

MWH, 2009 No

4b - mass of emissions smaller relative to other sources at the

Canyon; emissions

constituents expected to be the same as from the Canyon, because same kind of fuel

was used.

1A CanyonRocket engine testing

Kerosene, JP-4/RP-1 LOX

Jupiter, Thor, Redstone and H-1 Saturn 1B

629 tests reported at TRE-1; 606 tests reported at TRE-2; 4,384 tests reported at TRE-3

MWH, 2009; ATSDR, 1999;

rocketdynearchives.com

Yes

3a, 4a - H-1 engine releases largest mass of

emissions associated with JP-

4/LOX combustion.



Source Name





B359 Energetics testing

Small test cells

Bldgs 1359 and 1741

1950s to 1960s

perchlorate, HMX, RDX NA

Energetics research using solid propellants.

Pechlorate was used to test igniters in small test cells in Bldg 1741. Energetics testing using HMX and RDX was performed in four test cells in Building 1359.

MWH,2009 Yes

3a - identified source of

emissions from energetics testing.

B359Rocket engine testing

NAKA AreaLikely Blgs 1344, 1348,

1363

1956-early 1960s perchlorate NA

Rocket engine component production and testing.

MWH, 2009 No

4b - mass of emissions smaller relative to other sources at the

B359; emissions constituents

expected to be the same as from the Bldgs 1359 and 1741, because same kinds of

energetics were used.



Source Name





Happy Valley North

(HVN)

Energetics testing

Tunnel Facility/Bldg

1316Bldg 1316 Mid-1950s to

early 1990s perchlorate NA

Enclosed structure used to test gun propellants and turbine spinners

MWH, 2009 No2b - represents small, enclosed

source.

HVN Energetics testing

Detonation sumps Bldg 1315 Mid-1950s to

early 1990s perchlorate NA

Detonation sumps used to test small rocket motors and small rounds (20 and 40 mm)

MWH, 2009 No 4b - represents small source.

HVN Incinerator Incinerator East of Bldg 1316

1957 - 1990 see comments NA

Used for burning of rags and paper towels used to apply solvent, and propellant waste (perchlorate).

MWH, 2009 Yes


emissions from incineration.

Happy Valley South (HVS)

Energetics testing

Gun Propellant

R&D & Testing (with small rocket

motor testing)

Bldg 1372 mid-1960s to 1993 perchlorate NA MWH, 2009 No 4b - represents

small source.



Source Name





HVSRocket engine testing

Motor Test Area

Bldgs 1745 and 1706

mid-1960s to 1993

perchlorate; other

chemicals reported include

beryllium and MMH

Some use of NTO

Small motor engines tested on vertical stands with solid and high energy propellants; exhaust from Bldg 1706 testing captured in AST with water spray system

MWH, 2009 No 4b - represents small source.

Advanced Propulsion

Test Facility (APTF)

Component testing

3.5-inch injectors Peter 1978-1979 Kerosene LOX MWH, 2009 No

1b - neutrally buoyant source -

no combustion testing.

5.7-inch injectors Mike 1989-1991 Kerosene LOX

Advanced Experimental

Thrust Program

-- 1967 MMH NTO

HHC Hit with Azine Mike 1991 Kerosene LOX

Liquid Flyback booster

-- 1998 Kerosene LOX

Used to test components in liquid-fueled rocket engines & propellant research. Components tested included injectors, combustors, pulse engines, cryogenic engines, thrust chambers, small turbopumps, bearings, and seals.

There were four test pits: Bldg 1786 had Pits 1 (Nan, Lima, Mike stands) and 2 (Peter, Roger, Sugar stands); Bldg 1764 had Pit 3 (Uncle, Victor, Yoke, Willie); Bldg 1767 had Pit 4 (Zebra, X-Ray, Tare).



Source Name





MK51 Turbopump Willie 1984-85 MMH NTO

OMS (Orbital Maneuver-ing System)

Peter 1998 Ethanol LOX

Pulse Engine Alta Early 1980s MMH NTO

RS-44 Nan 1984-1989 Hydrogen LOX

RS-68 gas generator Peter 1997 Hydrogen LOX

Static pulse engine Victor 1983-1986 MMH NTO

XLR-132 Willie/Uncle 1989-1991 MMH NTO

Lance -- 1962-1970 UDMH IRFNA

APTF Incinerator IncineratorSW of

Equipment Storage Yard

not available not available not available

Dioxins detected in soil below characteriza-tion levels.

MWH, 2009 No

4b - represents small source

compared with HVN incinerator.



Source Name





1B Area I Burn Pit (AIBP) Burn Pit

Burn Pit (destruction

of waste chemicals and high energy

compounds by

combustion and

1958-1990 see comments NA

Used for disposal of fuels, solvents, process chemicals, igniters, reactive metals, energetics

CH2M HILL, 2009 Yes


emissions from incineration.

BowlRocket engine testing

Atlas See comments 1954-late 1960s Kerosene LOX CH2M HILL,

2009 Yes

Navaho 1950-1957 Kerosene LOX

Redstone 1951-1959 Ethanol LOX

Component Testing

Laboratory III (CTL-III)

Component testing

Modules 1 through 4 late 1950s NA NA

Included testing various sub-components of sitewide rocket testing programs (e.g., new pumps and generators).

CH2M HILL, 2009 No 3b - no toxic

emissions.

3a, 4a - Atlas engine releases largest mass of

emissions associated with JP-

4/LOX combustion.

Vertical Test Stands (VTS) - VTS-1, VTS-2,

and VTS-3, and a

horizontal test stand at the

VTS-1 location.



Source Name





Component Testing

Laboratory V (CTL-V)

Component testing Building 1422 not

availableNA NA

Used to test rocket engine turbo pumps and turbines.

CH2M HILL, 2009 No 3b - no toxic

emissions.

5

System Testing

Laboratory IV (STL-IV)

Rocket engine testing

Modules 1 through 3

Near Building 3747 See below See below See below

STL-IV was used for small engine testing from the mid-1950s through the early 2000s.

CH2M HILL, 2008; ATSDR,

1999Yes

3a, 4a - Peacekeeper

engine emissions represent the

largest mass of emissions

associated with hydrazine/MMH

Apollo reentry

Located in Cell 16 of Module 1 1962-1969 Hydrazine NTO

Beech 1959-1966 Hydrazine NTO

Condor (RS-19)

Located in Cell 26 of Module 2 1967-1970 Hydrazine CTF

EXO 1978 MMH NTOGemi 1953-1954 Hydrazine NTOHOE 1979 MMH NTO

KEW 1993-early 2000s MMH NTO

LE3 1973-1976 Hydrazine NTOLEM 1967-1970 Hydrazine NTO

Liquid aircraft rockets 1955-1958 Hydrazine NTO

MKV 1979 MMH NTOMX Peace-

keeperLocated in Cell 24A in Module 1978-1994 MMH NTO



Source Name





OEM-6K 1973 Hydrazine NTORCS-600 1973 Hydrazine NTO

RS-14 Minuteman 1968-1977 Hydrazine NTO

RS21 1975 Hydrazine NTOSE5 1960-1968 Hydrazine NTO

Transtage 1953 Hydrazine NTOX70 1977-1978 MMH NTO

Delta 2A Diffuser

Located in Cell 26 in Module 2 not available not available not

available

Tank venting and system aspiration

One ventline exhausted

vapors to top of hill 338 feet east of Bldg

254; other vent stack is 452 ft

NE of Bldg 254.

not available NA NTO

Notes and Key Sources:Draft Preliminary Site Evaluation, Santa Susana Field Laboratory, Ventura County, CA (Agency for Toxic Substances and Disease Registry, Dec. 1999)Group 1A, Northeast Portion of Area I, RCRA Facility Investigation Report (MWH, Feb. 2009) APTF Test History, Memorandum from R. Metzner, 8-11-98, HDMSE00434880. Rocketdyne Archives, www.rocketdynearchives.comGroup 1B, Southern Portion of Area I, RCRA Facility Investigation Report (CH2M HILL, Sept. 2009) Group 5, Central Portion of Areas III and IV, RCRA Facility Investigation Report (CH2M HILL, Nov. 2008)

TABLE B‐2 Summary of Sources to be Modeled Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

Group RFI Site Source Type Representative

Source Reason for Selection

1A Canyon Rocket Engine Testing H‐1 Saturn 1B Engine

Potential toxicity of combustion products. Of the engines tested in the Canyon, H‐1 Saturn 1B is likely to release a larger mass of emissions due to its higher thrust.a,b

1A Happy Valley North

Incineration Incinerator Potential toxicity of combustion products. Of Boeing’s two former incinerators, this source is likely to release a larger mass of emissions due to its longer operational period (relative to the Advanced Propulsion Test Facility incinerator).

1A B359 Energetics Testing Testing with Research Department Explosive (RDX)

Potential toxicity of combustion products. B359 is less contained relative to the other locations where energetics testing was performed; as such, the B359 tests are likely to have a greater potential for dispersion. In this location, data regarding RDX is readily available and one of the most common materials used in the industry.

1B Area I Burn Pit

OB Activities Area I Burn Pit Potential toxicity of combustion products. This is the only source of its type.

1B Bowl Area Rocket Engine Testingc Atlas Engine Potential toxicity of combustion products. Of the engines tested in the

Bowl Area, Atlas is likely to release a larger mass of emissions due to its higher thrust.

a,b

5 STL‐IV Intercontinental Ballistic Missile Testing

MX‐Peacekeeper Missile

Potential toxicity of combustion products. Of the missiles tested in STL‐IV, MX‐Peacekeeper is likely to release a larger mass of emissions due to its longer operational period.b

Notes: a Source: Sutton, 2006. b Source: ATSDR, 1999. c Although the Bowl Area source type is identical to the Canyon Area, a rocket engine will be modeled in both RFI sites because they both used differing fuels (kerosene and ethanol were used at the Bowl Area, while kerosene, jet propellant‐1/rocket propellant‐1 [RP‐1], and hydyne were used at the Canyon Area) and are geographically separated areas with potentially different dispersion characteristics due to the local terrain.

TABLE B‐3 CALMET Domain Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

Corner UTM Easting (km) UTM Northing (km)

Southwest 306.181 3751.536

Northeast 381.181 3826.536

Note: Coordinates are provided in WGS‐84, Universal Transverse Mercator (UTM), Zone 11.

TABLE B‐4 Meteorological Data – Percent Completeness Evaluation Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

Year Onsite Data

Total Wind Direction Wind Speed Temperature Stability Class Rural Mixing

Height Urban Mixing

Height

2002 99% 97% 97% 100% 100% 99% 99%

2003 93% 94% 94% 98% 98% 88% 88%

2004 99% 97% 97% 99% 100% 99% 99%

2005 94% 91% 91% 96% 96% 96% 96%

2006 97% 94% 94% 97% 99% 99% 99%

TABLE B‐5 Surface Stations Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

Station Name Station ID 2002 2003 2004 2005 2006

Los Alamitos AAF 722975 x x X x x

Torrance Municipal 722955 x x X x x

Long Beach Airport 722970 x x X x x

Fullerton Municipal 722976 x x X x x

El Monte 747043 x x X x x

Santa Barbara Municipal 723925 x x X x x

Oxnard Airport 723927 x x X x x

Point Mugu NAWS 723910 x x X x x

Camarillo AWOS 723926 x x X x x

Sandburg AUT 723830 x x X x x

Santa Monica Municipal 722885 x x X x x

Newhall 720046 X x x

Los Angeles International 722950 x x X x x

Van Nuys Airport 722886 x x X x x

Jack Northrop Field H 722956 x x X x x

Whiteman Airport 745057 x x X x x

LA USC Downtown Campus 722874 x x X x x

Burbank/Glendale 722880 x x X x x

Mount Wilson 722890 x x x x

Lancaster/Fox Field 723816 x x X x x

Palmdale Production 723820 x x X x x

Note: ‘x’ Indicates that data from this station for this year will be included in the RFI project air dispersion modeling. The list of meteorological stations to be used to provide surface meteorological data for modeling will be confirmed with DTSC.

TABLE B‐6 Precipitation Stations Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

Station Name Station ID 2002 2003 2004 2005 2006

Brea Dam 41057 X x X x x

Santa Fe Dam 47926 x x X x x

Fullerton Dam 43285 x x X x x

Orange Co. RSVR 46473 x x X x x

Pacific Cologe FC 356B 48436 x x X x x

San Gabriel DM FC425BE 47779 x x X

Simi Sanitation Plant 48261 x x X x x

Piru Telemetering 46942 x x X x x

Newhall S FC32CE 46162 x x X x x

San Fernando PH 3 47762 x x X x x

Acton Escondido FC261 40014 x x X x x

Vincent FS FC120 49345 X x x

Lancaster ATC 44749 x x X x x

Mill Creek Summit RS 45637 x x X x x

Palmdale 46624 x x X x x

Carpinteria RSVR 41540 x x X x x

Matilija Dam 45417 x x X x x

Ozena GRD Station 46577 x x X x x

Frazier Park 9 SW 43219 x x X x x

Oxnard WFO 46572 x x X x x

Chatsworth RSVR 41682 x x X x x

Sepulveda Dam 48092 x x X x x

Los Angeles International Airport 45114 x x X x x

Hansen Dam 43751 x x X x x

Los Angeles Downtown USC 45115 x x X x x

Burbank Valley Pump Plant 41194 x x X x x

Signal Hill FC415 48230 x x X x x

Long Beach Daugherty Airport 45085 x x X x x

Whittier Narrows Dam 49666 x x X x x

Note: ‘x’ Indicates that data from this station for this year will be included in the RFI project air dispersion modeling. The list of meteorological stations that will be used to provide precipitation data for modeling will be confirmed with DTSC.

TABLE B‐7 Buoy Data – Percent of Substituted Data Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

Year Station ID 46053 Station ID 46025

2002 1.1% 1.9%

2003 9.1% 0.9%

2004 0.3% 0.4%

2005 0.2% 0.3%

2006 0.7% 0.5%

TABLE B‐8 CALPUFF Modeling Options Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

Parameter CALPUFF Option

Meteorological Options

Meteorological File Onsite Data; Hourly Surface, Buoy, Upper Air, and Precipitation Data; MM5 Data; Coastal Data

Met Data Type CALMET

Wind Direction No limitations

Base Time Zone 8

Wind Speed Wind speeds of less than 1 meter per second (m/sec) are set equal to 1 m/sec, unless wind is 0 m/sec when puffs are immobile during calm periods

Precipitation Events modeled during precipitation events

Terrain Options

Terrain Type Complex

Stack Tip Downwash Not applicable for buoyant area sources; yes for point sources

Pollutant Options

Number of Species Modeleda 1

Number of Species Emitteda 1

Model Puffs as Slugs Yes for buoyant area sources; no for point sources

Allow Puff Splitting Yes

Maximum Number of Puffs Released per Hour

1 for buoyant area sources; continuous for point sources

Notes: a Particulate matter will be modeled as the surrogate pollutant for each source type modeled. This is appropriate because the volatile organic compound and semivolatile organic compound combustion products are typically evaluated as particle‐bound constituents (USEPA, 2005b). As appropriate, a molecular weight of 200 grams per mol will be used for 10‐micron particulate matter in accordance with A User’s Guide for the CALPUFF Dispersion Model (Version 5) (Scire et al., 2000b).

TABLE B‐9 Modeling Parameters by Source Type Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

Modeling Parameters

Source Description

Incineration Energetics

Testing OB Activities

Intercontinental Ballistic Missile

Testing Rocket Engine

Testing Rocket Engine

Testing

RFI Location Happy Valley North

B359 Area I Burn Pit STL‐IV Bowl Area Canyon

Source Type Point Buoyant Area Source

Buoyant Area Source

Buoyant Area Source

Buoyant Area Source

Buoyant Area Source

Representative Source Incinerator Testing with RDX Area I Burn Pit MX‐Peacekeeper Atlas H‐1 Saturn 1B

Source Dimensions TBD TBD TBD TBD TBD TBD

Propellant Name TBD RDXa Diesel & Dunnage TBD LOX & Keroseneb LOX & Keroseneb,c

Propellant Typed TBD Solid Solid TBD Liquid Liquid

Years of Operation 1957 ‐ 1990 1950 ‐ 1960 1958 ‐ 1990 1978 ‐ 1994 1954 ‐ 1960 1954 ‐ 1968

Tests per Year N/A TBD TBD TBD 293e TBD

Tests per Operation Lifetime

N/A TBD TBD TBD 2,340 ± 1,500e TBD

Total Mass Consumed TBD TBD TBD TBD TBD TBD

Notes:

STL‐IV = Systems Test Laboratory IV TBD = to be determined N/A = not applicable RDX = research department explosive a Although high‐melting explosive was also used, RDX has similar properties and was likely used in larger quantities. b Source: ATSDR, 1999. c Hydyne (60% unsymmetrical dimethylhydrazine and 40% diethylenetriamine) was also used as a fuel at the Canyon Area. The relative toxicity of all fuels used at Canyon Area will be evaluated prior to modeling to confirm which should be used in the modeling scenario. d The particle size distribution used within CALPUFF will be selected based on the propellant type. Solid propellants will be represented using data estimated during the BangBox studies (Mitchell and Suggs, 1998). Liquid propellants will be represented using data for gas‐fired turbines obtained from manufacturer data or other reputable sources. If available, source‐specific, particle‐sized distributions will be used in place of representative distributions based on propellant type. e Source: CH2M HILL, 2009.

TABLE B‐10 Bowl Area: Representative Rocket Engine Testing ScenarioRecommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

Parameter Bowl Area

Engine Type Atlas

Propellant Type LOX & Kerosene/RP‐1a

Propellant per test (grams)b 163,350,000

Propellant Heat Content (calories per gram)c 96

Fire Duration (seconds)c, d 190

Nozzle Orientation Vertical, nozzle downe

Burn Pan Area (square feet) TBD

Source Height (feet) TBD

Source Locations (UTM Zone 11, km, North American Datum 83) TBD

Quench Cooling Systemsf Yes

Max Thrust Capacity by Design (pounds)g 564,000

PM10 Emission Factor (pounds per second)h 0.697

Notes: a While kerosene is the fuel listed as being combusted by the Atlas engines, historical information indicates that RP‐1 was piped in 4‐inch pipelines from fuel tanks within the Bowl Area to each of the test stands (CH2M HILL, 2009). As a result, it was assumed that RP‐1 was the type of kerosene fuel combusted during Atlas engine testing. b The propellant per test was estimated using the specific impulse (seconds), thrust (Newtons), burn rate (kilogram per second), gravitational acceleration (meters per seconds squared), and fire duration (seconds) (Sutton, 2006). The available data specified these parameters for both the booster and sustainer nozzle; as a result, the propellant quantities for both nozzle types were summed to yield the propellant per test per engine. Detailed calculations are included in Attachment B‐1. c Data for an RD‐170 type engine were assumed representative of the Atlas engine using the same fuel blend without performing any scaled analysis. The heat content accounts for water used for noise attenuation (National Aeronautics and Space Administration, 1994a). d Data for a large test engine at Marshall Space Flight Center were assumed representative of the Atlas engine without performing any scaled analysis (Glasgow, 2010); data provided were consistent with that of an RD‐170 type engine. e Although the Bowl Area’s Test Stand 1 had a horizontal test stand, vertical test stands are expected to have more significant and measurable deposition. As a result, Boeing proposes to only model vertical test stands and consider impacts from the horizontal test stand negligible. f When water tanks are present near a test site, it is assumed that quench cooling systems were used; therefore, due to the presence of deionized water storage tanks near Test Stand 3 in the Bowl Area, it was assumed that quench cooling systems were used for this source (CH2M HILL, 2009). g This is the maximum thrust of a three‐nozzle Atlas engine in flight (two booster nozzles and one sustainer nozzle) (Sutton, 2006). h Data for an RD‐170 type engine, scaled from data measured by Rocketdyne for a MA5 engine, were scaled by the ratio of Atlas engine fuel burn rate to the RD‐170 engine fuel burn rate (Sutton, 2006; Sutton and Biblarz, 2010). The RD‐170 emission factor was 1.74 pounds per second (National Aeronautics and Space Administration, 1994b). Detailed calculations are included in Attachment B‐1.

TABLE B‐11 Bowl Area: CALPUFF Options for Rocket Engine Testing ScenarioRecommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

Parameter CALPUFF Option

Plume Temperature (degrees Kelvin)a 400

Effective Rise Velocity (m/sec)a 1

Effective Plume Radius (m)a 40

Effective Release Height (m)a 20

Sigma Z (m)a 19

Notes: a These parameters were calculated based on the intrinsic properties of the propellant as well as assumed parameters used by OBODM.

Figures

START

SCO362070.TM.11.SW.BO MDGWP Ident_Sources_Flow_rev3.vsd 11/12

1. Source Type Based on Buoyancy

2. Potential for Dispersion

3. Emission Constituents 4. Relative Mass of Emissions

Buoyant

FIGURE B-1Flowchart for Identifying Sources that Warrant Air Dispersion ModelingRecommended Approach for Air Dispersion Modeling Technical MemorandumSanta Susana Field Laboratory, Ventura County, CA

5. Confirmation

Neutral

Dense

No modeling warranted –limited and localized

impacts

High Temperature and/or Uncontained (larger plume

radius, more distant impacts)

Low Temperature and/or Partially or Fully Contained (small plume

radius, localized impacts)

High – relative to other sources

Low – relative to other sources

No modeling warranted –limited and localized

impacts or inadequate data

Sources Selected for Modeling

1a

1b

1c

2a

2b

4a

4b

Toxic or Combination of Toxic/Non-Toxic

Non-Toxic only (e.g., steam)

3a

3b

Legend:Source retained for modelingSource not retained for modeling

ES120210023632SCO362070.TM.11.SW.BO SSFL_Wind_Rose_rev.ai 11/12

FIGURE B-2 Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation ProjectComprehensive Data Quality Objectives Technical MemorandumSanta Susana Field Laboratory, Ventura County, CA

WRPLOT View - Lakes Environmental Software

WIND ROSE PLOT:

SSFL ONSITE data2002-2006 ISC Processed Data

COMMENTS:

10-m AGL

COMPANY NAME:

MODELER:

DATE:

9/20/2010

PROJECT NO.:

SSFL

NORTH

SOUTH

WEST EAST

3%

6%

9%

12%

15%

WIND SPEED (m/s)

>= 11.1

8.8 - 11.1

5.7 - 8.8

3.6 - 5.7

2.1 - 3.6

0.5 - 2.1

Calms: 8.75%

TOTAL COUNT:

43167 hrs.

CALM WINDS:

8.75%

DATA PERIOD:

2002-2006 Jan 1 - Dec 3100:00 - 23:00

AVG. WIND SPEED:

2.69 m/s

DISPLAY:

Wind SpeedDirection (blowing from)

FIGURE B-3 Modeling Domain and Off-Site Meteorological Data Stations Recommended Approach for Air Dispersion Modeling, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California

Notes:

The Miramar Upper Air Station is not included in this figure because it is located approximately 200 miles south of the SSFL. X and Y axes are presented in latitude/longitude coordinates (NAD 83). The on-site meteorological station in SSFL Administrative Area IV was also used; it is not shown because. at this scale, the symbol would cover the SSFL boundary shown on the figure.

Attachment B-1 Bowl Area Rocket Engine Testing

Scenario Parameters

1-1

ATTACHMENT B‐1

Bowl Area Rocket Engine Testing Scenario Parameters Parameter: Fuel Burn Rates

Methodology: Calculate the Fuel Burn Rate for both the RD‐170 and Atlas engines based on the equation for constant thrust of an engine and data available in Rocket Propulsion Elements (Sutton and Biblarz, 2010) and History of Liquid Propellant Rocket Engines (Sutton, 2006).

Data:

Engine Thrust Units Data Source

RD‐170 740,000 kilograms (kg)

Table 11‐3 of Rocket Propulsion Elements (Sutton and Biblarz, 2010)

Atlas ‐ Booster Nozzle 430,000 pounds (lbs) Table 7.8‐1 of History of Liquid Propellant Rocket Engines (Sutton, 2006)

Atlas ‐ Sustainer Nozzle 60,000 lbs

Engine RD‐170 Atlas ‐ Booster

Nozzle Atlas ‐ Sustainer

Nozzle Data Source

Thrust (Newtons [N]) 7,256,921 1,912,735 266,893 Converted from above data

Specific Impulse (seconds) 309 265 220 a, b

Gravity (meter per seconds squared [m/s2])

9.8066 9.8066 9.8066 Rocket Propulsion Elements (Sutton and Biblarz, 2010)

Oxidizer / Fuel Ratio 2.63 2.25 2.27 See Notes below

Propellant Burn Rate (kilograms per second [kg/sec])

2,395 736 124 Calculated, as indicated below, using Equation 2‐5 from Rocket Propulsion Elements (Sutton and Biblarz, 2010)

Fuel Burn Rate (kg/sec) 660 226 38 Calculated, as indicated below, assuming the propellant burn rate is the sum of the oxidizer burn rate and fuel burn rate

Notes: a Data for the RD‐170 engine were taken from Table 11‐3 of Rocket Propulsion Elements (Sutton and Biblarz, 2010). b Data for the Atlas engine were taken from Table 7.8‐1 of History of Liquid Propellant Rocket Engines (Sutton, 2006).

Calculation:

Thrust (N) = Thrust (lbs) x 4.448222 (N/lb) Thrust (N) = Thrust (kg) x 9.80665 (N/kg) Propellant Burn Rate (kg/sec) = Thrust (N) / [Specific Impulse (seconds) x Gravity (m/s2)] Fuel Burn Rate (kg/sec) = Propellant Burn Rate (kg/sec) / [Oxidizer / Fuel Ratio + 1]

Parameter: PM10 emission factor

Methodology: Determined the PM10 emission factor by scaling the emission factor available for an RD‐170 engine by the ratio of the Atlas engine fuel burn rate to the RD‐170 engine fuel burn rate.

Data:

Engine RD‐170 Atlas Data Source

Fuel Burn Rate (kg/sec) 660 264 Calculated above; the Atlas fuel burn rate is the sum of the booster and sustainer nozzle fuel burn rates

PM10 Emission Factor (pounds per second

1.74 x Estimates of Rocket Exhaust Emission Factors for the RD‐170 Engine Test Program, Memorandum for Record (National Aeronautics and Space Administration,1994b);

ATTACHMENT 1 BOWL AREA ROCKET ENGINE TESTING SCENARIO PARAMETERS

1-2

[lbs/sec]) calculated

Calculation:

x = RD‐170 PM10 emission factor (lbs/sec)x (Atlas fuel burn rate [kg/sec]/RD‐170 fuel burn rate [kg/sec]) x = 0.697 lbs/sec

Parameter: Propellant per test

Methodology: Calculate the propellant per test using the propellant burn rate and fire duration.

Data:

Engine Atlas ‐ Booster

Nozzle Atlas ‐ Sustainer

Nozzle Data Source

Propellant Burn Rate (kg/sec) 736 124 Calculated above

Fire Duration (seconds) 190 190 Typical duration for engines tested at Marshall Space Flight Center (Glasgow, 2010)

Propellant per Test (grams [g]) 139,844,109 23,504,454 Calculated, as indicated below

Total Atlas Propellant per Test (g) 163,348,562 Calculated, as indicated below

Calculation:

Propellant per Test (g) = Propellant Burn Rate (kg/sec) x Fire Duration (seconds) x 1,000 (g/kg)

Total Atlas Propellant per Test (g) = Atlas ‐ Booster Nozzle Propellant per Test (g) + Atlas ‐ Sustainer Nozzle Propellant per Test (g)

Appendix C Integration of the SMOU Risk Assessment

Methodology with the DQO Process

1

T E C H N I C A L M E M O R A N D U M Integration of the Surficial Media Operable Unit Risk Assessment Methodology and the Data Quality Objectives Process, Boeing RCRA Facility Investigation, Santa Susana Field Laboratory, Ventura County, California PREPARED FOR: The Boeing Company


DATE: March 8, 2013

1.0 Introduction and Purpose This technical memorandum (TM) presents the proposed approach for integration of the Surficial Media Operable Unit (SMOU) risk assessment methodology and the comprehensive data quality objectives (DQO) process for The Boeing Company (Boeing) Resource Conservation and Recovery Act (RCRA) facility investigation (RFI) subareas at the Santa Susana Field Laboratory (SSFL). The comprehensive DQO process will be used to identify and fill remaining RFI data gaps in the various Boeing RFI subareas and to support completion of the RFI and transition to the corrective measures study (CMS) phase of the project. This TM supports the Comprehensive Data Quality Objectives, RCRA Facility Investigation, Santa Susana Field Laboratory, Ventura County, California (DQO Report, CH2M HILL, 2013a) and the Master RCRA Facility Investigation Data Gap Work Plan, Santa Susana Field Laboratory, Ventura County, California (Boeing Master RFI Data Gap Work Plan, CH2M HILL, 2013b).

The Boeing SMOU risk assessment methodology will be applied to support RFI recommendations regarding portions of land identified for CMS and as an additional line of evidence for portions of land identified for Conditional No Further Action (CNFA). The Boeing risk assessment methodology described in this TM will be applied to all media of the SMOU, including soil, soil vapor, surface water, sediment, and groundwater. The risk assessment methodology will also include concurrent evaluation of risk associated with the Chatsworth Formation Operable Unit (CFOU) within each Boeing RFI site; however, CMS/CNFA recommendations for groundwater and the CFOU vadose zone will not be made until completion of all ongoing CFOU RFI activities. In addition, seeps and springs, which are generally located around the perimeter of the SSFL and beyond the boundaries of the RFI sites, will be evaluated separately as part of the CFOU RFI.

Following the ecological risk assessment work at each RFI site, a large home‐range receptor ecological risk assessment (LHRERA) will be conducted separately as part of the Boeing SMOU RFI evaluations, and the results will be incorporated into the SMOU CMS and CNFA recommendations.

2.0 Regulatory Framework for Risk Assessment Evaluation The California Environmental Protection Agency, Department of Toxic Substances Control (DTSC) has oversight responsibility for the Boeing SSFL RFI, including the risk assessment components. In addition, DTSC has engaged human health and ecological toxicologists from its Human and Ecological Risk Office to review the various risk assessment deliverables generated during the Boeing SSFL RFI project.

3.0 Prior Risk Assessment Activities for the Boeing SSFL RFI Project

The Boeing draft SMOU RFI reports were submitted to DTSC during 2008 and 2009, and a sitewide groundwater remedial investigation report was submitted to DTSC in 2009. These reports incorporated a consistent risk assessment methodology developed by Boeing and its technical consultants to support the RFI completion process. The DTSC approved the Standardized Risk Assessment Methodology Work Plan, Revision 2 (SRAM, Rev. 2) (MWH Americas, Inc. [MWH], 2005), and this methodology and was used as the basis for the human health and

INTEGRATION OF THE SURFICIAL MEDIA OPERABLE UNIT RISK ASSESSMENT METHODOLOGY AND THE DATA QUALITY OBJECTIVES PROCESS, BOEING RCRA FACILITY INVESTIGATION, SANTA SUSANA FIELD LABORATORY, VENTURA COUNTY, CALIFORNIA

2

ecological risk assessments included in these various Boeing draft reports submitted to DTSC. The risk assessment findings in these reports will be updated following collection and evaluation of additional RFI data during the comprehensive DQO process using the risk assessment methodology presented herein, as well as the SRAM, Rev. 2 (MWH, 2005) and the SRAM, Rev. 2 addendum (currently under development).

4.0 Proposed Risk Assessment Methodology The SRAM, Rev. 2 (MWH, 2005) is being updated by a series of supplementary TMs, which include updated risk assessment procedures, exposure assumptions, and toxicological information. The TMs were developed largely in response to DTSC comments concerning human health and ecological risk assessments submitted in the draft SMOU RFI reports, as well as comments and requests provided by DTSC during various review meetings. Selected TMs also provide chemical‐specific risk‐based screening levels (RBSLs) for use in forthcoming risk assessment work. Although the TMs have been prepared and submitted as separate documents, they represent an interrelated set of methodologies that together serve to update the SRAM, Rev. 2 and guide ongoing and future

risk assessment work at SSFL.1

The key human health and ecological TMs that will be referenced during risk assessment methodology in the forthcoming Boeing RFI work are listed in Table 1.

TABLE 1 Key Human Health and Ecological Technical Memoranda Developed to Update the Standardized Risk Assessment Methodology, Revision 2 Integration of the Surficial Media Operable Unit Risk Assessment Methodology with the Data Quality Objectives Process, Boeing RCRA Facility Investigation, Santa Susana Field Laboratory, Ventura County, California

Title Date Submitted

to DTSC Current Status

(June 2012)

Human Health Risk Assessment TMs

Human Health Risk Assessment Sum‐of‐Fractions Methodology for Chemicals TM (MWH, 2010a) April 2010 Draft

Hotspot Evaluation TM (MWH, 2010b) June 2010 Draft

Process for Selecting the Comprehensive List of Chemicals for Development of Rural Residential Risk‐based Screening Levels TM (MWH, 2011b)

September 2011 Draft

Human Health Risk‐based Screening Levels TM (MWH, 2012) February 2012 Draft

Ecological Risk Assessment TMs

Inhalation Toxicity Reference Value Updates for use in Ecological Risk Assessments TM (MWH and CH2M HILL, 2011)

June 2011 Final

Ecological Effects Characterization Update TM (MWH, 2011c) August 2011 Final

Ecological Exposure Assessment Update TM (MWH, 2011d) August 2011 Draft

Ecological Risk‐based Screening Levels for Use in Ecological Risk Assessments TM (MWH, 2011a) November 2011 Draft

Large Home‐range Receptor Ecological Risk Assessment Technical Memorandum (CH2M HILL) Summer 2012 In preparation

Note:

These human health and ecological TMs apply to soil, sediment, and surface water exposures by suburban residents, recreators, and ecological receptors.

1 The various TMs issued subsequent to the SRAM, Rev. 2 (MWH, 2005) will be collectively published as a SRAM Rev. 2 addendum to update the risk assessment process for the SSFL.


3

5.0 Human Health Risk Assessment Methodology For the forthcoming Boeing RFI work, the human health risk assessment will be conducted for the suburban

residential and recreational receptors on a Boeing RFI site scale.2 The human health risk assessment will be conducted sequentially for the various media. First, the soil evaluation will follow a sum‐of‐fractions approach, as described in the Human Health Risk Assessment Sum‐of‐Fractions Methodology for Chemicals Technical Memorandum, Santa Susana Field Laboratory, Ventura County, California (MWH, 2010a). The sum‐of‐fractions method for chemicals involves computation of the ratio of constituent concentrations in site media with precalculated, chemical‐specific RBSLs to derive risks for each constituent and each receptor. The updated human health RBSLs for soil have been computed for all potentially relevant and complete exposure pathways using exposure parameters specific to a given receptor and the toxicity characteristics of each constituent, as documented in the Human Health Risk‐Based Screening Levels Technical Memorandum, Santa Susana Field Laboratory, Ventura County, California (MWH, 2012); it is expected that the RBSLs will be updated to incorporate current toxicity values when the SRAM, Rev. 2 addendum is prepared and that the updated RBSLs will be used for risk assessment purposes. For the few locations where sediment and surface water sampling data exist, risk estimates will be computed in accordance with SRAM, Rev. 2 to evaluate human health (recreational) exposures.

Secondly, the risk evaluation for soil vapor based on measured concentrations, if available, will be conducted for each RFI site. Characterization of soil vapor in support of the evaluation of potential human health risks is described in the Updated Approach for Assessing the Vapor Intrusion Pathway, Boeing RCRA Facility Investigation Project, Santa Susana Field Laboratory, Ventura County, California (VI TM) (CH2M HILL, 2013c). The soil vapor screening levels identified in the VI TM will be used in a similar sum‐of‐fractions approach as RBSLs being applied for the soil risk evaluation. When soil vapor and collocated groundwater volatile organic compound data are both available, the soil vapor data will be used preferentially over the groundwater data for the indoor air pathway evaluation. Shallow soil vapor data (collected from a minimum of 5 feet below ground surface unless collected beneath concrete or asphalt) that provide a reasonable representation of the vapor intrusion pathway will be used for the sum‐of‐fractions evaluation.

Thirdly, the groundwater risk evaluation will be conducted as described in the SRAM, Rev. 2 (including potable consumptive use). The risk assessment methodology will include evaluation of risk contributions from

groundwater on a Boeing RFI site scale,3 but individual CMS and CNFA recommendations for groundwater will not be provided until completion of the ongoing CFOU RFI.

The cumulative multimedia4 risks will be estimated by considering the additive ratios for all carcinogenic constituents or will target organ‐specific constituent groups for noncarcinogenic constituents for all media within each RFI site. As needed, the radionuclide concentrations will be addressed in a similar manner, except that the radionuclide concentrations in site media will be compared to United States Environmental Protection Agency (USEPA) preliminary remediation goals for radionuclides (USEPA, 2007) to derive risks.

6.0 Ecological Risk Assessment Methodology As part of the combined risk assessment process, the ecological risk assessment will follow a similar sum‐of‐fractions approach on an RFI site scale, consistent with the Ecological Risk‐Based Screening Levels for Use in Ecological Risk Assessments, Santa Susana Field Laboratory, Ventura County, California (Ecological RBSLs TM) (MWH, 2011a), and as described in Section 5.0 of this TM. The ecological risk assessment will involve computation of the ratio of constituent concentrations in site media with precalculated medium‐ and chemical‐specific ecological RBSLs for each representative receptor. The ecological RBSLs for soil, soil vapor, sediment, surface

2 The cumulative risk will be evaluated for each RFI site within each Boeing RFI Sub-Area. For Group 10, cumulative risk will be evaluated for each of the three distinct portions of that group (that is, the western, central, and eastern watersheds). 3 If an RFI site does not have a monitoring well within the boundaries, then a representative alternate nearby or downgradient monitoring well will be used. 4 Cumulative multi-media risk, as used in this TM, refers to potential risks and/or hazards posed by joint exposure to multiple carcinogenic constituents, or target organ-specific constituent groups for noncarcinogenic constituents as evaluated for soil, soil vapor, sediment, surface water, and groundwater.


4

water, and shallow groundwater were computed using the SRAM, Rev. 2 (MWH, 2005), as updated with the ecological TMs listed in Table 1, and are presented in the Ecological RBSLs TM. As described in the SRAM, Rev. 2, potential impacts from shallow groundwater to ecological receptors will be evaluated if groundwater is present at a depth of 6 feet or less below grade level. Cumulative risks are estimated for chemical groups with similar modes of toxicity, including organochlorine pesticides, dioxins/ furans/ coplanar polychlorinated biphenyls, non‐coplanar polychlorinated biphenyls, low‐molecular‐weight polycyclic aromatic hydrocarbons, and high‐molecular‐weight polycyclic aromatic hydrocarbons. As needed, radionuclides will be evaluated following the Level I approach and using biota concentration guides as described in the United States Department of Energy’s (DOE) A Graded Approach for Evaluating Radiation Doses to Aquatic and Terrestrial Biota (DOE, 2002).

In addition, a LHRERA will be conducted separately in accordance with the LHRERA TM (currently in preparation). The LHRERA will be conducted following completion of the Boeing SMOU RFI evaluations for all Boeing RFI subareas and will evaluate all subareas as a single exposure area. The LHRERA will achieve the DQOs and will support SMOU CMS/CNFA recommendations, as discussed in Section 5.2.4 of this TM.

7.0 Approach for Implementing the Boeing SMOU Risk Assessment Methodology in Support of DQO Process

This section describes how and when the Boeing SMOU risk assessment methodology will be implemented during completion of the Boeing RFI DQO process to support CMS and CNFA recommendations.

7.1 Identify Boeing Areas to be Evaluated and Complete the DQO TM Media-specific Evaluation Process

The initial step is to identify the Boeing areas for which the DQO data gap evaluation process and corresponding SMOU risk assessment methodology will be applied. The nine Boeing RFI subareas are identified in the Boeing Master RFI Data Gap Work Plan (CH2M HILL, 2013b). With the exception of RFI Group 10, each Boeing RFI subarea includes two to four RFI sites, and each RFI site contains one or more chemical use areas (CUAs). For each Boeing RFI subarea, the existing draft RFI reports (submitted in 2008 and 2009) will be reviewed to identify the draft CMS area recommendations and the remaining areas that were preliminarily recommended for CNFA. This step allows for an assessment of the existing information (site history, site characterization, and previous risk assessment findings) for each subarea, serves as the starting point for understanding the existing CUAs identified at the time of the draft RFI report preparation, and supports the data gap evaluation process.

All land in the subarea is then subject to evaluation under the process presented in the DQO Report on Figure 2 (CH2M HILL, 2013a) to identify and evaluate any new release or potential release. Each new release or potential release is either added to an existing CUA, identified as a new CUA (if documentation indicates chemicals were released to the environment), or is investigated to evaluate if the release or potential release meets the criteria for an expanded or new CUA. Each CUA is then grouped into a CUA cluster based on consideration of operational history, geographic proximity, lithologic features, analytical parameters, dense nonaqueous‐phase liquid source locations, and previous CMS area recommendations. The individual CUA clusters in each subarea are then subject to further evaluation to satisfy the DQO Report media‐specific Tables 3, 5, 7, and 9, Study Questions 1, 2, and 3 (regarding complete characterization of the sources, nature and extent, and fate and transport of contaminants). The DQO process is intended to be an iterative process that continues until these study questions are adequately addressed. The Boeing SMOU risk assessment methodology will be performed as part of DQO Report Study Question 4 only after the DQO Report Study Questions 1, 2, and 3 are completely addressed.

7.2 Implement Risk Assessment Methodology 7.2.1 Generate Risk Calculations for each RFI Site As a first step in the Boeing SMOU risk assessment methodology for a specific Boeing RFI site, all existing and newly collected soil, soil vapor, surface water, and sediment data will be used to prepare human health and ecological risk calculations for the entire RFI site (using the SRAM, Rev. 2, as updated by the applicable TMs). The RFI site‐scale risk assessment will also include concurrent evaluation of risk associated with groundwater and the


5

CFOU vadose zone at that RFI site. If unacceptable human health or ecological risks are identified for an RFI site, the primary risk contributors will be identified as the focus of the follow‐on evaluation of refined CMS areas for the SMOU only (excluding groundwater), as described in Section 5.2.2. For the purposes of this SMOU risk assessment approach, the primary risk contributors are those chemicals with estimated risks that exceed the points of departure identified in the human health and/or ecological risk assessments.

The existing and new characterization data and risk evaluation results will be used to revise the previously identified SMOU CMS area boundaries and/or identify new CMS areas, if required (the CMS/CNFA boundaries for groundwater and the CFOU vadose zone will not be delineated until after completion of the ongoing CFOU RFI). This broad‐scale approach is consistent with the approach and results presented in the draft RFI reports and allows for an overall assessment of risk for each RFI site within the Boeing RFI subareas.

7.2.2 Delineate Preliminary SMOU CMS and CNFA Areas within each RFI Site Based on the existing and newly collected data and initial risk assessment results, all land in each RFI site will be reviewed to identify preliminarily which portions should be assigned to individual CMS areas or for designation as a CNFA area with respect to the SMOU (excluding groundwater, if present). The preliminary identification of which portions of land are to be assigned to individual CMS areas will be conducted by delineating those areas where the primary risk contributors (as identified from the RFI site‐scale risk assessment, as described in Section 5.2.1) for each RFI site are above applicable screening levels, with consideration given to natural features such as bedrock outcrops and steep terrain where sampling is infeasible. This process will include review of existing soil, soil vapor, surface water, and sediment data and delineating areas where individual chemical concentrations for the primary risk contributors associated with the corresponding media are above their respective human health or ecological screening levels (identified as points for departure for CMS recommendations), and the available background concentrations for such constituents. Based on this weight of evidence approach, the CMS areas will be compiled and identified in plan view using dot maps and/or other appropriate graphical methods.

Each of the preliminary CMS areas will be identified within the RFI site, and the remaining land within the RFI site will be identified as a preliminary CNFA area. The risk calculations for each RFI site will then be generated again, but only using data from the preliminary CNFA area (specifically excluding all preliminary CMS areas within each RFI site by assuming they will be subject to remedial planning). The risk assessment results will then be used when addressing the DQO Report media‐specific Tables 3, 5, 7, and 9, Study Question 4 (for SMOU only). The outcome will confirm whether the land outside the preliminary CMS areas should be recommended for CNFA, as initially assigned, or if modifications are needed to the preliminary CMS/CNFA boundaries (for example, some land preliminarily identified as CNFA is changed to CMS) and the risk calculations re‐run for the RFI site (again excluding the refined, preliminary CMS areas). This process will continue in an iterative manner until the preliminary CMS/CNFA areas are appropriately identified.

7.2.3 Incorporate Results of Groundwater-to-indoor-air Vapor Intrusion Pathway At this stage of the evaluation, the results from the vapor intrusion pathway assessment related to impacted groundwater will be incorporated (in accordance with the VI TM [CH2M HILL, 2013c]). The presence of groundwater plumes underlying portions of each RFI site will be reviewed to evaluate whether they extend beyond areas for which soil vapor data are available. Data from those areas that could be subject to vapor intrusion from groundwater source areas will be reviewed, and the preliminary CMS and CNFA area delineations will be modified accordingly to address SMOU multimedia risks, if any. Groundwater‐to‐indoor‐air screening levels have been calculated from risk‐based indoor‐air screening levels using attenuation factors to calculate corresponding concentrations in soil vapor and equilibrium partitioning with Henry’s Law constants to calculate groundwater screening levels. The methods used to calculate the groundwater screening levels are presented in further detail in the VI TM (CH2M HILL, 2013c). These screening levels will be used to evaluate the groundwater data to estimate potential risks from vapor intrusion. As described in Section 4.1, soil vapor data will be used preferentially to groundwater data to assess potential risks from the vapor intrusion pathways. Soil vapor screening levels that have been calculated using attenuation factors presented in DTSC’s vapor intrusion guidance,


6

as described in the VI TM (CH2M HILL, 2013c), will be used to evaluate soil vapor data. Risks from multiple volatile organic compounds in groundwater or soil gas will be assessed using the sum‐of‐fractions approach described in Section 4.1. In some cases, it may be necessary to collect soil vapor data to verify whether the CMS designation is appropriate for ecological exposures and whether it can be verified for human exposures.

7.2.4 Incorporate Results of Large Home-range Receptor Ecological Risk Assessment At this stage, the LHRERA will be conducted separately during the Boeing SMOU RFI evaluation to achieve the DQOs. The LHRERA will be conducted collectively for all Boeing RFI subareas using all existing data and forthcoming data from the DQO/data gap process. Therefore, the LHRERA will be conducted after all the RFI‐scale risk calculations are completed. The LHRERA results will be used to modify, if needed, the recommended SMOU CMS/ CNFA areas within each RFI site and RFI subarea.

The Boeing SMOU risk assessment findings and resulting proposed SMOU CMS and CNFA areas will be presented in the Data Summary and Findings Report for each subarea.

8.0 Overall Summary of Risk Assessment Approach For the forthcoming Boeing RFI work, the human health risk assessment will be conducted sequentially for the various SMOU and CFOU media on an RFI site scale to support the SMOU CMS and CNFA recommendations (excluding groundwater). The soil, sediment, and surface water evaluation will follow a sum‐of‐fractions approach (MWH, 2010a) using the appropriate RBSLs (MWH, 2012, as updated when the SRAM, Rev. 2 addendum is submitted) for soil and the SRAM, Rev. 2 (MWH, 2005) for sediment and surface water. The risk evaluation for soil vapor will use the residential soil vapor screening levels (CH2M HILL, 2013b) in a similar sum‐of‐fractions approach. The groundwater risk evaluation will be conducted as described in the SRAM, Rev. 2 (MWH, 2005), but individual CMS and CNFA recommendations for groundwater (and the CFOU vadose zone) will not be provided until completion of the ongoing CFOU RFI. The cumulative multimedia risks will then be estimated by considering the additive ratios for all carcinogenic constituents or target organ‐specific constituent groups for noncarcinogenic constituents for all media within each RFI site.

The ecological risk assessment will also be conducted to support the SMOU CMS and CNFA recommendations (excluding groundwater). The ecological risk assessment will follow a similar sum‐of‐fractions approach on an RFI site scale using precalculated ecological RBSLs for each representative receptor. The ecological RBSLs for soil, soil vapor, sediment, surface water, and shallow groundwater were computed using the SRAM, Rev. 2 (MWH, 2005) and are presented in the Ecological RBSLs TM (MWH, 2011a). Potential impacts from shallow groundwater to ecological receptors will be evaluated if groundwater is present at or less than 6 feet below grade level. Cumulative risks will be estimated for chemical groups with similar modes of toxicity. Finally, an LHRERA will be conducted following completion of the Boeing SMOU RFI evaluations for all Boeing subareas and will evaluate all subareas as a single exposure area.

9.0 References CH2M HILL. 2013a. Comprehensive Data Quality Objectives, RCRA Facility Investigation, Santa Susana Field

Laboratory, Ventura County, California. March.

CH2M HILL. 2013b. Master RCRA Facility Investigation Data Gap Work Plan, Santa Susana Field Laboratory, Ventura County, California. March.

CH2M HILL. 2013c. An Updated Approach for Assessing the Vapor Intrusion Pathway, Santa Susana Field Laboratory, Ventura County, California. Technical Memorandum. March.

MWH Americas, Inc. (MWH). 2005. Standardized Risk Assessment Methodology Work Plan, Santa Susana Field Laboratory, Ventura County, California. September.

MWH. 2010a. Human Health Risk Assessment Sum‐of‐Fractions Methodology for Chemicals Technical Memorandum, Santa Susana Field Laboratory, Ventura County, California. Draft. April.


7

MWH. 2010b. Hot Spot Evaluation Technical Memorandum, Santa Susana Field Laboratory, Ventura County, California. Draft. June.

MWH. 2011a. Ecological Risk‐Based Screening Levels for Use in Ecological Risk Assessments at the Santa Susana Field Laboratory Technical Memorandum, Ventura County, California. Draft. November.

MWH. 2011b. Process for Selecting the Comprehensive List of Chemicals for Development of Rural Residential Risk Based Screening Levels Technical Memorandum, Santa Susana Field Laboratory, Ventura County, California. Draft. September.

MWH. 2011c. Ecological Effects Characterization Update Technical Memorandum, Santa Susana Field Laboratory, Ventura County, California. August.

MWH. 2011d. Ecological Exposure Assessment Update Technical Memorandum, Santa Susana Field Laboratory, Ventura County, California. Draft. August.

MWH. 2012. Human Health Risk Based Screening Levels Technical Memorandum, Santa Susana Field Laboratory, Ventura County, California. Draft. February.

MWH and CH2M HILL. 2011. Inhalation Toxicity Reference Value Updates for Use in Ecological Risk Assessments Technical Memorandum, Santa Susana Field Laboratory, Ventura County, California. June.

United States Department of Energy (DOE). 2002. A Graded Approach for Evaluating Radiation Doses to Aquatic and Terrestrial Biota. Washington, DC. DOE‐STD‐1153‐2002. July.

United States Environmental Protection Agency (USEPA). 2007. Preliminary Remediation Goals for Radionuclides. Available online at: http://epa‐prgs.ornl.gov/radionuclides/equation.shtml. January. Accessed March 2012.

Appendix D Recommended Approach for Evaluating Vadose

Zone Mass Flux of Contaminants to Groundwater

TECHNICAL MEMORANDUM

Recommended Approach for Evaluating Vadose Zone Mass Flux of Contaminants to Groundwater, Revision 2 Santa Susana Field Laboratory, Ventura County, CA March 5, 2013

1.0 INTRODUCTION AND PURPOSE This Technical Memorandum (TM) presents the recommended approach for evaluating the mass flux of contaminants in the vadose zone to groundwater at Santa Susana Field Laboratory (SSFL). The TM also describes the vadose zone transport modeling that may be conducted at selected locations as a result of data evaluation. This TM supports the data quality objectives (DQO) framework for completing site characterization (CH2MHILL, 2012) in accordance with the Resource Conservation and Recovery Act (RCRA) Facility Investigation (RFI) as outlined in the 2007 Consent Order for Corrective Action (DTSC, 2007). In particular, Table 7 of the DQO framework establishes specific data quality objectives for chemical contamination in the vadose zone, with a subset of the DQOs specific to an evaluation of the transport of contaminants in the vadose zone (i.e., mass flux) to groundwater. The vadose zone at SSFL consists of variably thick layers of alluvium/colluvium, weathered/unweathered sandstone and siltstone bedrock, with prominent sandstone outcrops.

2.0 SUMMARY OF PRIOR MASS FLUX TO GROUNDWATER ASSESSMENTS

A review of prior mass flux to groundwater assessments has been made for SSFL and provides a basis for further evaluations. Conceptual assessments of trichloroethene (TCE) mass flux to groundwater were made in 2000 as documented in Appendix D of Technical Memorandum, Movement of TCE in the Chatsworth Formation (Montgomery Watson). The mass transport methodology presented therein applies to any volatile, dense non-aqueous phase liquid (DNAPL), in addition to TCE. This assessment considered TCE DNAPL flow and mass transfer in the bedrock vadose zone and utilized analytical solutions to evaluate rock matrix imbibition of TCE DNAPL, interphase partitioning, DNAPL dissolution rates and relative contributions of mass flux to groundwater from imbibed TCE DNAPL and vapor-phase TCE in the bedrock matrix.

Technical Memorandum March 5, 2013 Approach for Evaluating Vadose Zone Mass Flux of Contaminants to Groundwater, Rev 2 Page 2

A numerical two-dimensional discrete fracture network modeling assessment (FRACTRAN) of mass flux to groundwater of a perchlorate source in the vadose zone was made in 2003 (MWH, 2003a). The purpose of this modeling assessment was to evaluate the transport of perchlorate in a horizontally layered alluvial/weathered bedrock/unweathered bedrock aquifer with characteristics representative of SSFL and the influence of a short-lived (5-year) perchlorate source on plume behavior and longevity. A similar assessment was made for perchlorate in a fractured bedrock aquifer (MWH, 2003b) with characteristics representative of SSFL and a longer source term (10 years).

Additional numerical modeling assessments of vadose zone mass flux to groundwater were made in the Draft Site-wide Groundwater Remedial Investigation (RI) report (MWH, 2009). SESOIL was used to model the mass transfer of metals from vadose zone soil to groundwater. This modeling was based on site characteristics at the Engineering Chemistry Laboratory (ECL) RFI site located in Administrative Area III. SESOIL was also used to evaluate the protectiveness of soil matrix-based risk-based screening levels to groundwater for eleven volatile organic compounds (VOCs). In this same report, numerical modeling assessments were also made of the longevity of vadose zone sources on groundwater plume extent and internal concentrations using FRACTRAN.

Most recently, numerical modeling assessments (CompFlow Bio) have been made of three-phase flow (DNAPL, water, air) and mass transfer in the vadose zone and groundwater using two- and three-dimensional fracture networks. The numerical model is substantively based on the physics of the three-phase flow and mass transfer in the vadose zone described in Dense Chlorinated Solvents (Pankow and Cherry, 1996). CompFlo Bio’s relevance here likely lies in gaining insight into the physics of transient groundwater flow and separate and dissolved-phase contaminant transport in variably saturated 3-D fractured porous media. These numerical modeling assessments are research-related work that is in progress at the University of Waterloo in collaboration with the University of Guelph.

Additional information about these prior assessments can be gained by reviewing the referenced documents, with the exception of the recent-research related work using CompFlow Bio, which is unpublished as of the date of this Technical Memorandum.

3.0 APPROACH FOR EVALUATING MASS FLUX TO GROUNDWATER Information contained in the data quality objectives discussion for evaluating the mass flux to groundwater from the vadose zone (listed in Table 7 of the DQO framework) has been supplemented and compiled into a decision tree as depicted in Figure 1. The vadose zone mass flux to groundwater approach includes: evaluating the need for additional field data (i.e., drilling of deep borings); evaluating the need to model vadose zone mass flux to groundwater; modeling; and determining if the vadose zone should be recommended for the corrective measures study (CMS) or conditional no further action (CNFA).


3.1 Evaluate Need to Drill Additional Deep Borings Thirty deep borings have been installed at 21 RFI sites and two additional deep borings are scheduled to be installed at the Coca RFI site. Criteria for installing additional deep borings are outlined in Table 7 of the DQO framework. Such locations will be identified during development of the Master Data Gap Work Plan Addenda, which include the comprehensive DQO evaluation, responding to DTSC comments on the draft RFI reports and compilation of the Data Gap Sampling and Analysis Plan.

3.2 Evaluate Need to Model Mass Flux to Groundwater The DQO framework requires an evaluation of vadose zone sampling results against comparison values. As noted in Table 7 of the DQO framework, soil matrix, rock core and soil vapor sampling results are to be compared to background threshold values (BTVs) for chemicals where such values have been established or to groundwater comparison values (GCVs) to chemicals without BTVs. Comparison values are provided Tables 1 and 2. The BTVs listed in Table 1 reflect the values posted by DTSC for combined Chatsworth Formation strata at the 95th percent confidence level of the 95th percentile of the upper tolerance limit.

Groundwater comparison values are the maximum contaminant level (MCL) for drinking water. Groundwater MCLs are either primary MCLs established by the US Environmental Protection Agency (USEPA) and promulgated under the Safe Drinking Water Act (SDWA), or by the California Department of Public Health (DPH) promulgated by 22 CCR, sections 64431 through 64449 and 64672 (as published in Regional Water Quality Control Board, 2008; DPH, 2011). In cases where there are no MCLs, groundwater comparison values are based on the following rank order:

1. Notification Levels (NL) established by the California DPH (RWQCB, 2008; DPH, 2010a);

2. Archived Advisory Levels established by the California DPH (2010b);

3. Secondary Maximum Contaminant Levels (SMCLs), which address aesthetics, such as taste and odor (RWQCB, 2008; DPH, 2011) (listed as Secondary MCL in tables);

4. Taste and Odor Threshold (RWQCB, 2008) (listed as Taste/Odor in tables); and

5. Site-specific values developed for SSFL using risk assessment procedures assuming direct ingestion of groundwater (listed as SWGW RBSL [site-wide groundwater risk-based screening level] in tables). The methodology used to develop the risk-based screening values for chemicals that are not metallic elements and where there are no agency-published values is described in a technical memorandum included in Appendix 7-C of the Groundwater RI Report (MWH, 2009).


In some cases where more than one value is available for a chemical, the lower value is used to be more protective. When USEPA and California DPH MCLs differ, the lower value is used. In cases where the SMCL is lower than the primary MCL, the SMCL is used.

All soil vapor, soil matrix and rock core sampling results are to be queried and compared to the comparison values presented in Tables 1 or 2 in the first evaluation step. If vadose zone concentrations do not exceed comparison values, the mass flux to groundwater evaluation is complete and the vadose zone at this location will be recommended for CNFA to protect groundwater, unless in DTSC’s professional judgment additional work is required. If comparison values are exceeded, the vadose zone at this chemical cluster will either be recommended for CMS, or the transport of chemicals to groundwater may need to be modeled depending on a review of groundwater sampling results.

The second evaluation step requires a comparison of groundwater sampling results from nearby wells (generally within about 300 feet) along flow paths from the chemical cluster to groundwater comparison values. Flow paths will be evaluated by reviewing forward particle tracks from RFI sites and backward particle tracks from monitoring wells from the three-dimensional groundwater flow model under both pumping and non-pumping conditions (see Appendix 6-A in MWH, 2009 for additional information of particle tracking). Groundwater comparison values to which groundwater sampling results are to be compared (see Table 2) are the MCL (or other standards as described above). The well sampling results to compare against the groundwater comparison value are proposed as maximum detected concentrations within the last 3 years. The historical sampling record and hydrograph for the well(s) to be used for comparison are to be reviewed to ensure that groundwater conditions are representative of the monitoring history. Should groundwater concentrations in samples from the well exceed the comparison value, modeling is not required since data are available to demonstrate that the vadose zone at this location has impacted groundwater. The vadose zone at these locations requires further evaluation as part of subsequent study questions listed in DQO Table 7.

If sampling results from the well(s) does not exceed groundwater comparison values, vadose zone transport modeling is to be conducted, the methodology for which is described below.

3.3 Model Mass Flux to Groundwater The final step in the mass flux to groundwater evaluation requires an assessment of the contaminant conditions in the vadose zone and their potential impact on groundwater. This assessment will be completed by estimating their future transport, with the results used to determine if the vadose zone should be considered for CMS or CNFA as part of subsequent study questions of DQO Table 7.


3.3.1 Considerations in Simulating Vadose Zone Transport to Groundwater A range of lithologic and groundwater conditions exists throughout SSFL as described in previously submitted reports (e.g., MWH, 2003a and 2009) and as shown in Figure 2. Lithologic conditions include locations where:

1. Alluvium or colluvium overlies weathered and unweathered fractured sandstone1 and/or siltstone/shale; and

2. Weathered bedrock is exposed in outcrops with little or no soil cover and is underlain by unweathered fractured sandstone and/or siltstone.

The thickness of each lithologic unit varies locally throughout the site.

The occurrence of groundwater also varies across the site, with it being present under the four conditions shown in Figure 2. Groundwater can be present in alluvium/colluvium (condition 1), and/or weathered and/or unweathered fractured sandstone and siltstone (conditions 2 through 4). Groundwater can also be found perched at various locations (condition 3) and the perching condition may only persist during and after wet periods of a year. Groundwater flow and contaminant transport in the fractured sandstone and siltstone beneath SSFL occurs within a dual-porosity, dual-permeability system wherein little groundwater is stored within the fracture network and flow is rapid (i.e., ~kilometer per year), while the low permeability bedrock matrix holds nearly all of the groundwater and flow is slow (i.e., centimeters per year).

Vadose zone to groundwater transport estimates will be based on the following conditions:

1. The point of compliance will be first encountered groundwater as indicated by gauging events from monitoring locations. Depth to groundwater measurements collected during 2011 will be used to establish vadose zone thickness and the vertical point of compliance for modeling. The 2011 depth to groundwater measurements represent a conservative case, as they reflect about 10 years of groundwater recovery associated with the shutdown of interim measures extraction wells that started in 2000. Furthermore, additional groundwater interim measures are pending that will minimize the further rise of groundwater (MWH/Hargis, 2009).

2. The compliance period will be from current to 50 years into the future. This period is a reasonable assumption as it reflects a total timeframe of more than 100 years as the data assessment incorporates more than 50 years of operational history that has produced the current day contaminant distribution(i.e., ~1955 to current).

1 Sandstone at SSFL has been sub-divided into four lithologies: “typical”, banded, hard and breccia as described in Hurley, Parker and Cherry, 2007. For the vadose zone modeling work, “typical” sandstone properties will be used as it comprises the vast section of sandstone at the site.


3. The compliance limits will be the MCLs or other screening values described in Section 3.2. The modeled porewater concentration at the base of the vadose zone will be compared to this compliance limit as a basis for further action.

4. Fractures in the vadose zone bedrock will be neglected since they represent the largest openings and hence have small entry pressures. Calculations indicate (Appendix D in Montgomery Watson, 2000) that the interfacial tension of water entering fractures during precipitation events is insufficient to support a capillary interface across the fracture. As such, water flow in the vadose zone will occur in the bedrock matrix blocks since the pore sizes are much smaller than the fracture openings.

5. Because the fractures can be neglected in the vadose zone, contaminant transport within alluvium/colluvium underlain by weathered and unweathered sandstone/siltstone or outcropped fractured sandstone/siltstone can be modeled using available tools that have been developed to characterize transport in granular media (see Appendix D in Montgomery Watson, 2000 for additional supporting information).

6. Transport modeling will utilize the local lithologic and contaminant conditions.

7. Initially, recharge flux through the vadose zone will be applied as a boundary condition using the rates derived during optimized calibration of the three-dimensional groundwater flow model (see Appendix 6-A in MWH, 2009). The recharge flux may be adjusted within the estimated range for the site (see SCM Element 10-2 in Groundwater Advisory Panel, 2009).

3.3.2 Software Code Evaluation Various vadose zone transport software codes were considered for application at SSFL. Software codes that were considered included: VLEACH (Ravi & Johnson, 1997), SESOIL (Environmental Software Consultants Inc., 2006), VS2DI (Hsieh, et al, 1999), HYDRUS 2-D/3-D (Integrated Groundwater Modeling Center, 2011), and FEFLOW (DHI-WASY, 2010). VLEACH and SESOIL are one-dimensional (1-D), screening-level vadose zone transport software codes, while the other 3 software codes can simulate transport in 1-D columns and 2-D planar and axisymmetric problems. HYDRUS 3-D and FEFLOW can simulate contaminant transport in 3-D variably saturated conditions. FEFLOW has been applied extensively at SSFL to simulate the groundwater flow field (see Appendix 6-A of the Draft Groundwater RI Report, MWH, 2009).

VLEACH is a 1-D, finite difference, screening-level software code for making preliminary assessments of the effects on groundwater from the leaching of volatile, sorbed contaminants through the vadose zone. The software code accounts for four main processes: liquid-phase advection, solid-phase sorption, vapor-phase diffusion, and three-phase equilibration. VLEACH requires an assumption of homogeneous soil conditions within a 1-D column and was specifically developed for evaluating transport of volatile organic compounds.

SESOIL is a 1-D vertical transport screening-level software code for the vadose zone and is designed to simulate fate and transport of chemical compounds based on diffusion, adsorption,


volatilization, biodegradation, cation exchange and hydrolysis. SESOIL is based on mass balance and partitioning of the chemical between the dissolved, sorbed, vapor, and pure phases.

VS2DI is U.S. Geological Survey’s graphical software package for simulating flow and transport in variably saturated porous media. VS2DT is a finite-difference model code that solves Richard’s equation for fluid flow, and the advection-dispersion equation for solute transport. Solute transport processes include advection, dispersion, first-order decay, adsorption, and ion exchange. VS2DI does not include vapor transport for volatile organics.

The HYDRUS (1-D version also available, United States Salinity Laboratory, 2005) and FEFLOW programs are both finite element software codes for simulating the 3-D movement of water, heat, and multiple solutes in variably saturated media. Both software codes include more sophisticated descriptions for water flow and contaminant transport than the other 3 codes mentioned above. Of these two codes, FEFLOW would be most easily adapted to vadose zone transport assessments at SSFL because of its extensive use for simulating flow in the groundwater system.

3.3.3 Software Code Selection and Description The transport of contaminants from the vadose zone to groundwater will be simulated using the Seasonal Soil compartment model (SESOIL). SESOIL was selected for this screening-level vadose zone transport evaluation because of its: relative simplicity of use; hydrologic representation; ability to incorporate the lithologies encountered; previous use in the Draft Groundwater RI Report; and representation of the transport processes for the chemicals to be modeled. SESOIL has undergone modifications and improvements by Oak Ridge National Laboratory and others since 1981. SESOIL has been incorporated along with other modeling packages into the Windows-based SEVIEW Version 7.1 software distributed by Environmental Software Consultants, Inc. (ESCI) and is proposed for the vadose zone transport evaluation.

SESOIL assumes steady state flow conditions and solves the water balance equation on a monthly cycle. The vadose zone flow rate is calculated as a function of the saturated hydraulic conductivity and the average saturation raised to the power of an exponent referred to as the pore disconnectedness index. The entire unsaturated zone is conceptualized as homogeneous and the soil moisture content calculated by SESOIL is an average value for the entire thickness. When different lithologies are modeled in the hydrologic cycle of SESOIL, it calculates a depth-weighted average of permeability. As such, care must be taken when applying SESOIL with varying lithologies to ensure that the resultant water balance and moisture contents are representative.

SESOIL contains five basic files for constructing a vadose zone modeling scenario; climate, chemical, soil, washload, and application (ESCI, 2006). Within each file are various sub-files with additional data inputs. It is proposed that the washload sub-file not be utilized for the vadose zone


mass transport to groundwater evaluation because neglecting its effect will result in allowing more mass transfer to the groundwater and is therefore more conservative.

3.3.3.1 Climate File SESOIL’s climate file contains data from meteorological stations that describe air temperature, cloud cover, relative humidity, short wave albedo, mean evapotranspiration rate, monthly precipitation, mean length of precipitation events, number of precipitation events per month, and the distribution of precipitation events throughout the month. A survey of meteorological stations that record such data and are proximal to SSFL shows the meteorological station located at Pierce College in Canoga Park, CA to be closest and pertinent records are shown in Table 3. The station is located approximately seven air miles southeast of SSFL at an elevation of 740 feet. Although SSFL is located approximately 1,000 feet higher in elevation than the Pierce College weather station, the proximity of the station to the site is believed to be more representative than stations at a similar elevation, but more distant from SSFL. SSFL meteorological data will be further reviewed and evaluated against the Pierce College meteorological file to determine if adjustments can be made to the climate file to reflect the higher elevation of SSFL and be locally representative. As an example, recorded monthly precipitation may be utilized that equates to the site’s annual average of 18.4 inches per year.

3.3.3.2 Chemical File SESOIL’s chemical database lists chemical and physical data for 695 chemicals. The majority of default chemical and physical data included in the database provide information on water solubilities, air and water diffusion coefficients, Henry’s Law constants, molecular weights, octanol-carbon adsorption (Koc) coefficients, and soil partition coefficients (Kd), which are also the most commonly used chemical input parameters for SESOIL modeling. Default chemical and physical data included in the SESOIL chemical database should be viewed as broadly representative because of the multiple data sources used to develop the database, which sometimes provide conflicting values. As a result, a literature review of chemical and physical data listed for each inorganic and organic chemical to be modeled will be conducted to verify its accuracy and appropriateness. In cases, where values are not provided or multiple values exist for a particular property, sources such as CRC Press’ Handbook of Chemistry and Physics (66th Edition, 1985-1986), technical resource websites associated with the United States Environmental Protection Agency (EPA), United States Geological Survey, National Institute of Standards and Technology, and Oak Ridge National Laboratory, plus peer reviewed journal articles will be evaluated and considered. In the case where conflicting property values are listed and resolution cannot be accomplished, a median value will be calculated and selected.


Although provided as a default parameter in SESOIL, a Henry’s Law constant (HLC) for metals, metalloids, and alkaline earth cations will not be used except for mercury, for which a specific HLC value is proposed in lieu of the default. Vadose zone modeling conducted for the Draft Groundwater RI report showed little sensitivity in the model results with and without HLCs for metals. Default octanol-water partitioning coefficients and distribution coefficients values listed in the SESOIL chemical database generally represent the most conservative (i.e., lowest) value within a range reported in the literature or determined experimentally in the field or laboratory. The use of conservative Koc and Kd values potentially results in significantly higher predicted movement of chemicals in the vadose zone than would be reasonably expected under actual site conditions. For trace metals, metalloids, and alkaline earth cations expected to be modeled (except cadmium), site-specific Kds have been calculated using total and synthetic precipitation leaching procedure (SPLP) sample results presented in a 1996 site investigation report (Ogden, 1996). For cadmium, a literature review of Kd data was conducted to identify a range of values representing soils and vadose zone conditions similar to SSFL. The data were then reviewed to generate a median Kd value. The site-specific Kds are within the mid-range of Kd values reported in the literature. Table 4 lists Kd values plus other chemical and physical input parameters for the nine inorganic chemicals expected to be modeled at SSFL. Koc values have been obtained from the literature for the chlorinated ethenes that are expected to modeled. Table 5 lists these Koc values plus other pertinent chemical and physical input parameters for the chlorinated ethenes. A table of similar information will be prepared for the three PAHs, pentachlorophenol and 2,3,7,8-TCDD and any other chemicals that may need to be modeled as a result of the RFI site data evaluations. As a conservative approach, vadose zone transport modeling of chlorinated ethenes will not incorporate mass transfer or loss via biodegradation or hydrolysis. These processes may be evaluated in a sensitivity analysis.

3.3.3.3 Soils/Lithology File Site-specific chemical and physical soils data will be used as inputs to characterize contaminant transport from the vadose zone. Site-specific chemical and physical soils data reported in the Site Conceptual Model for the Migration and Fate of Contaminants in Groundwater (Groundwater Advisory Panel, 2009) and the Draft Groundwater RI Report (MWH, 2009) provide values for the physical and chemical properties. Table 6 lists the target physical properties for the lithologies to be used in the vadose zone transport modeling. These properties may be adjusted within the measured range reported in the Site Conceptual Model (Groundwater Advisory Panel, 2009) to match the expected hydrologic cycle, groundwater recharge rates, and reported moisture content. Data generated from soil surveys conducted by the Natural Resource Conservation Service (2009) may be used as supplementary information to construct the vadose zone column for transport modeling if necessary.


3.3.3.4 Applications File SESOIL’s application file contains five sub-files; column, ratio, layer, sub-layer load, and Summers equation. The column sub-file requires site-specific inputs for size of load area (i.e., source area), site latitude, number of layers in the vadose zone column (up to 4), thickness of each layer, number of sub-layers per layer (up to 10), and selection of release type (instantaneous or continuous). Location-specific data consisting of the vadose zone thickness and lithology will be used to populate the column sub-file. Since there are no longer active operations at SSFL, the vadose zone modeling will utilize the measured concentrations of chemicals present in soil vapor, soil matrix or rock core samples at RFI sites as the source term for predicting future impacts to groundwater. Releases will be considered instantaneous, that is the entire mass of the chemical released in the modeling scenario occurred on the first day of the first month of the first year of the 50-year compliance period. The ratios sub-file allows inputs for pH, intrinsic permeability, ratios for liquid and solid phase biodegradation, organic carbon, cation exchange, Freundlich exponent and adsorption coefficient. Site-specific data that corresponds to the lithology will be used for pH, intrinsic permeability, organic carbon (Table 6) and adsorption coefficient (Table 4), while default values will be used for the remainder. As mentioned previously, the modeling will be conducted without incorporating mass loss by biodegradation as a conservative case, but may be evaluated in a sensitivity analysis. For each model layer a sub-file is available that contains seven categories that allow for monthly inputs of contaminant load, mass of contaminant transformed, mass of contaminant removed, ligand load, volatilization index, index of contaminant transport in surface runoff, and ratio of contaminant concentration in rainwater to vadose zone water. For this modeling effort, only the volatilization index sub-file will be used when modeling VOC transport. Volatilization indices for the VOCs that may require modeling will be generally represented as follows for locations that are not covered by paved surfaces or buildings:

From ground surface to a depth of 0.5 meters: 0.5,

From a depth >0.5 meters to 1.0 meter: 0.25, and

From depths >1.0 meter: 0.

Volatilization indices of 0.5 and 0.25 represent cases where 50% and 25% of the mass predicted to volatilize in the vadose zone migrates upward and is not part of the mass predicted to reach groundwater during the 50-year compliance period. A volatilization index of 0 represents the case where volatilization to the atmosphere is not allowed and the remaining mass is used to predict the VOC aqueous phase solute concentration that reach groundwater. For locations covered by paved surfaces or buildings, the volatilization index to be set to 0 throughout the soil column.


The sub-layer load sub-file will be used to enter chemical concentration data for each sub-layer in the vadose zone. The chemical concentration profile to be modeled will be the maximum concentration detected within an RFI site at each vertical sampling interval. For values that are reported as “U” or non-detect, a value of half the detection limit will be utilized to the total depth investigated. Concentrations below the total depth investigated will be assigned either a value of “0” for non-native chemicals or background concentrations for naturally-occurring chemicals. Soil vapor sample results will be converted to soil matrix concentrations assuming equilibrium partitioning between the vapor, sorbed and aqueous phases. The calculated VOC soil matrix concentrations will be used as input to the vadose zone model. The Summers equation sub-file will not be used. This sub-file incorporates mixing of vadose zone leachate with groundwater. However, the aqueous phase concentration at the groundwater interface prior to mixing will be used as the value for comparison to the groundwater comparison value of 10 times the MCL (or other screening values).

3.3.3.5 Sensitivity Analyses and Uncertainties Expected sensitivity analyses that may be conducted for the vadose zone mass flux modeling include the following:

Vadose zone thickness: This sensitivity will be evaluated at locations where the historical groundwater gauging record indicates the historical presence of shallower groundwater than the depths gauged during the 2011 timeframe and in areas beyond the expected influence of groundwater extraction as specified in the Groundwater Interim Measures Work Plan Addendum (MWH/ Hargis+Associates, 2009). This sensitivity will only be evaluated if the initial results show that the groundwater comparison value is not exceeded over the 50 year compliance period.

Biodegradation: This sensitivity will be evaluated specifically for the PAHs and pentachlorophenol by incorporating half-lives on the lengthier end of those reported in the literature. Although there is strong evidence of chlorinated ethene transformation in the vadose zone as evidenced by the measurement of TCE daughter products in soil vapor, the pathway is not well understood and a representative half-life is difficult to estimate. As such, biodegradation of chlorinated ethenes will not be evaluated as a sensitivity for the characterization evaluation.

Chemical concentration: Depending upon the availability of the vertical profile of chemical sampling results, a sensitivity analysis may be conducted on chemical concentration by considering that the chemical has been transported to a greater depth than site measurements indicate. This sensitivity would be evaluated at locations where sample results show elevated concentrations of chemicals at the soil/bedrock interface. The value of the concentration that will be assumed will be equivalent to the value of the deepest measured concentration. This sensitivity will only be


evaluated if the initial results show that the groundwater comparison value is not exceeded over the 50 year compliance period.

Recharge: The influence of increased recharge on vadose zone contaminant transport will be evaluated at locations proximal to ephemeral drainages. At these locations, groundwater recharge will be increased by a factor of two or three beyond the base case. This sensitivity will also only be evaluated if the initial results show that the groundwater comparison value is not exceeded over the 50 year compliance period.

3.4 Data Evaluation, Documentation and Reporting The vadose zone mass flux to groundwater evaluation requires analysis and evaluation of the data inputs as presented in Table 7 of the DQOs. Of critical importance at each site are:

Operational history and DQO criteria to determine if new deep borings are to be drilled.

Soil matrix, soil vapor, rock core and groundwater sampling results and comparison of the results to the comparison values presented in Tables 1 and 2.

Determinations and rationale as to whether existing data are sufficient to recommend the vadose zone for CNFA, transport modeling, or evaluation in the CMS.

For vadose zone transport modeling:

o Cross-section of the location chosen to represent the vadose zone transport column, including lithologies encountered and their thickness and depth to groundwater.

o Well hydrographs to confirm that depth to groundwater in 2011 is at or near historical maximums.

o Selection and rationale for the chemicals whose transport is simulated.

o Selection and rational for the chemical properties (if not listed in this document) and vertical concentration profile to be used as input to the transport estimates.

o Modifications to the climate file based on an evaluation of SSFL meteorological data.

o Listing and rationale for any other model inputs not presented in this document or modified from the parameters listed herein.

o Selection and rationale of any sensitivity analyses.

Documentation will be provided on all of the above in either electronic file format or in hard copy report. Transport modeling output needs to document the aqueous solute concentration at the


vadose zone/groundwater interface over the 50 year compliance period for each chemical modeled. Breakthrough curves will be provided for chemicals simulated to reach this interface at concentrations equal to or greater than MCLs (or other groundwater screening criteria). Results of sensitivity analyses will also be provided along with a discussion of their effect on transport modeling outcomes. The modeling results will be used to specify if the vadose zone should be recommended for CMS or CNFA.

4.0 SUMMARY OF VADOSE ZONE MASS FLUX TO GROUNDWATER APPROACH

Data quality objectives for the vadose zone at SSFL require an evaluation of the mass flux of contaminants to groundwater. Final outcomes of the evaluation will be to either: recommend that the vadose zone at various locations throughout SSFL be further evaluated in the CMS to protect groundwater, or recommended for CNFA.

The DQO process for the vadose zone mass flux to groundwater evaluation includes evaluations of existing data to determine:

If additional deep borings need to be drilled; and

If the vadose zone can be recommended for CMS based on comparing new or available data to comparison values, or if transport estimates are required.

Decisions to install additional deep borings will be determined during planned comprehensive data reviews for data gap sampling in accordance with DQO Table 7.

If concentrations of contaminants in the vadose zone exceed the DQO comparison values but are below the groundwater comparison values, contaminant transport will be estimated using the SESOIL vadose zone transport model. If model results show contaminant concentrations in aqueous phase solute are above groundwater MCLs (or other available screening criteria) at the base of the vadose zone anytime over the next 50 years, the location will be recommended for CMS. If not, the vadose zone at this location will be recommended for CNFA (to protect groundwater). However, additional vadose zone evaluations may be required to protect other transport pathways and receptors as described in Table 7 of the DQOs (CH2MHill, 2012).

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Hurley, J.C., B.L. Parker and J.A. Cherry, 2007. Source Zone Characterization at the Santa Susana Field Laboratory: Rock Core VOC Results for Coreholes C1-C7. Final. Department of Earth Sciences, University of Waterloo. June.

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_____, 2003b. Perchlorate Characterization Work Plan (Revision 1). Santa Susana Field Laboratory, Ventura County, California. December, 2003.

_____, 2009. Draft Site-Wide Groundwater Remedial Investigation Report, Santa Susana Field Laboratory, Ventura County, California. Volumes 1 through 7. In Association with the SSFL Groundwater Advisory Panel, University of Guelph, Haley & Aldrich and AquaResource Inc. December.


MWH & Hargis+Associates, 2009. Addendum to Revision 2 of the Work Plan for Groundwater Interim Measures, Santa Susana Field Laboratory, Ventura County, CA. January.

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Pankow, James F. and John A. Cherry, 1996. Dense Chlorinated Solvents and Other DNAPLs in Groundwater. Waterloo Press.

Ravi, V. and J. A. Johnson, VLEACH: An One-Dimensional Finite Difference Vadose Zone Leaching Model, Version 2.2, Developed for USEPA, R. S. Kerr Res. Lab., Ada, OK. 1997.

Regional Water Quality Control Board, Central Valley Region, 2008. A Compilation of Water Quality Goals, prepared by Jon D. Marshack, D.Env. July

Syracuse Research Corporation, 1997. Anaerobic Biodegradation of Organic Chemicals in Groundwater: A Summary of Field and Laboratory Studies. Final Report. Environmental Sciences Center, Syracuse Research Center, North Syracuse, NY 13212-2509

Syracuse Research Corporation, 1999. Aerobic Biodegradation of Organic Chemicals in Environmental Media: A Summary of Field and Laboratory Studies. Final Report: SRS TR 99-002. Environmental Science Center, Syracuse Research Corporation, North Syracuse, NY 13212-2509

United States Environmental Protection Agency, 1999. Anaerobic Biodegradation Rates of Organic Chemicals in Groundwater: A Summary of Field and Laboratory Studies. June.

United States Salinity Laboratory, Agricultural Research Service, 2005. HYDRUS-1D Model, Version 3.01. April

ATTACHMENTS FIGURES 1 Decision Tree for Vadose Zone Mass Flux to Groundwater Evaluation

2 Lithologic and Groundwater Conditions

TABLES 1 Background Threshold Values

2 Groundwater Comparison Values

3 Meteorological Inputs

4 Chemical and Physical Properties for Inorganic Chemicals

5 Chemical and Physical Properties for Preliminary Volatile Organic Chemicals

6 Physical Properties of Lithologic Units

ATTACHMENTS

FIGURES

Compare available soil, soil vapor and rock core

chemical sampling results to background (BTVs) or groundwater comparison

values1 (GCVs)

Are concentrations > BTVs or GCVs?

Conditional no further action for vadose zone

mass flux to groundwater

Monitoring well along flow path

nearby?

Recent groundwater sampling

results available (within last 3 years)?

Groundwater concentration

>GCV?

Evaluate vadose zone in corrective measures

study for groundwater protection

Install well

Collect and analyze samples

Model future transport in accordance with

vadose zone to groundwater mass flux

TM

Modelpredicts

leachate at water table >GCVs within next 50

years?

List chemicals with concentrations >

BTVs or GCVs

Yes

No

No

Yes

Yes

Yes

Yes

No

No

No

Figure 1 - Decision Tree for Vadose Zone Mass Flux to Groundwater Evaluation

1For chemicals that have background values, soil

matrix sample results will be compared to the

background values. For all other chemicals, soil

matrix, soil vapor and rock core sample results will

be compared to groundwater comparison values.

Groundwater comparison values are based on the

following rank order:

1. The lower of federal or state primary drinking

water maximum contaminant levels,

2. Notification Levels (NL) established by the

California DPH (RWQCB, 2008; DPH, 2010a);

3. Archived Advisory Levels established by the

California DPH (2010b);

3. Secondary maximum contaminant levels, which

address aesthetics, such as taste and odor

(RWQCB, 2008; DPH, 2011);

4. Taste and odor threshold (RWQCB, 2008) ; and

5. Site-specific values developed for SSFL using risk

assessment procedures assuming direct ingestion

of groundwater.

The methodology used to develop the risk-based

screening values for chemicals that are not metallic

elements and where there are no agency-

published values is described in a technical

memorandum included in Appendix 7-C of the

Groundwater RI Report (MWH, 2009).

The only exception to the priority rank for selecting

the comparison value is for those chemicals for

which groundwater comparison values have been

established by DTSC (i.e., metals). For metals, the

groundwater comparison value was selected as the

first priority, followed by the rank order as

described above.

Area within known

rocket engine or equipment testing

DNAPLrelease?

No

Deep boring results

available?

Yes

Yes

NoDrill deep boring &

analyze vadose zone & groundwater

samples

DTSC professional

judgment requires deep

boring?

NoYes

Figure 2Lithologic and Groundwater Conditions

Vadose Zone Mass Flux to Groundwater Modeling

1 2 3 4

AAlluvium/ colluvium

Alluvium/ colluvium

Alluvium/ colluvium

BWeathered sandstone

Weathered sandstone

Weathered sandstone

Weathered sandstone

CUnweathered

sandstone

D Siltstone

Condition #:

Lithology:

Groundwater occurrence:

Variation on groundwater occurrence:

Cro

ss-s

ecti

onal

sch

emat

ic (

not t

o sc

ale,

lith

olog

y th

ickn

ess

and

dept

h to

gro

undw

ater

var

y)

3A:Perched groundwater (almost always a

single perched zone) extends upward into alluvium/ colluvium

Present in all lithologies with continuous saturation

Present in both lithologies with continuous saturation

Perched on weathered/unweathered contact, extensive system deeper

Present in unweathered fractured sandstone and siltstone

1A:Alluvium/ colluvium is unsaturated,

groundwater first occurs in weathered sandstone

2A:Weathered sandstone is unsaturated,

groundwater first occurs in unweathered sandstone

Layered: alluvium, weathered, unweathered fractured sandstone/ siltstone of variable

thickness

Unweathered sandstone



Layered: alluvium, weathered, unweathered fractured sandstone of

variable thickness

Layered: weathered, unweathered fractured sandstone of variable thickness

Layered: alluvium, weathered, unweathered fractured sandstone of variable thickness

TABLES

Table 1Background Threshold Values

Updated 3/5/13 Page 1 of 3 Abbreviations defined on page 3

Analyte UnitsBackground Threshold

Value1,2,3,4,6,7,8-HpCDD mg/kg 2.41E-061,2,3,4,6,7,8-HpCDF mg/kg 6.94E-071,2,3,4,7,8,9-HpCDF mg/kg 6.55E-081,2,3,4,7,8-HxCDD mg/kg 7.61E-081,2,3,4,7,8-HxCDF mg/kg 1.25E-071,2,3,6,7,8-HxCDD mg/kg 7.39E-071,2,3,6,7,8-HxCDF mg/kg 1.69E-071,2,3,7,8,9-HxCDD mg/kg 9.95E-071,2,3,7,8,9-HxCDF mg/kg 9.84E-071,2,3,7,8-PeCDD mg/kg 1.00E-071,2,3,7,8-PeCDF mg/kg 1.64E-071-Methyl naphthalene mg/kg 1.80E-032,3,4,6,7,8-HxCDF mg/kg 1.81E-072,3,4,7,8-PeCDF mg/kg 2.18E-072,3,7,8-TCDD mg/kg 2.76E-082,3,7,8-TCDF mg/kg 2.81E-072,4,5-T mg/kg 6.07E-042,4,5-TP (Silvex) mg/kg 3.22E-042,4-Dichlorophenoxyacetic Acid (2,4-D) mg/kg 3.17E-032,4-Dichlorophenoxybutyric acid mg/kg 2.70E-022,4-DP (Dichloroprop) mg/kg 1.42E-032-Methylnaphthalene mg/kg 1.80E-034,4'-DDD mg/kg 1.86E-044,4'-DDE mg/kg 4.16E-034,4'-DDT mg/kg 6.10E-03Acenaphthene mg/kg 1.80E-03Acenaphthylene mg/kg 8.15E-04Aldrin mg/kg 9.30E-04alpha-BHC mg/kg 8.70E-04Aluminum mg/kg 37900Anthracene mg/kg 6.45E-04Antimony mg/kg 0.497Arsenic mg/kg 24.2Barium mg/kg 203.8Benzo(a)anthracene mg/kg 1.22E-03Benzo(a)pyrene mg/kg 1.64E-03Benzo(b)fluoranthene mg/kg 3.26E-03Benzo(ghi)perylene mg/kg 1.18E-03Benzo(k)fluoranthene mg/kg 3.53E-03Beryllium mg/kg 1.424beta-BHC mg/kg 1.26E-04bis(2-Ethylhexyl) phthalate mg/kg 2.80E-02Boron mg/kg 18.85Butyl benzyl phthalate mg/kg 4.30E-02Cadmium mg/kg 0.435




ValueCalcium mg/kg 9765Chlordane mg/kg 3.72E-03Chlordane (Technical) mg/kg 3.72E-03Chromium mg/kg 60.11Chrysene mg/kg 2.46E-03Cobalt mg/kg 26.18Copper mg/kg 42Cyanides mg/kg 0.267Dalapon mg/kg 0.1delta-BHC mg/kg 1.15E-04Dibenzo(a,h)anthracene mg/kg 1.02E-03Dicamba mg/kg 7.56E-04Dieldrin mg/kg 1.28E-04Diethyl phthalate mg/kg 9.95E-02Dimethyl phthalate mg/kg 2.00E-02Di-n-butyl phthalate mg/kg 8.37E-03Di-n-octyl phthalate mg/kg 6.37E-03Dinoseb mg/kg 2.70E-02Endosulfan I mg/kg 8.26E-05Endosulfan II mg/kg 2.14E-04Endosulfan sulfate mg/kg 1.78E-04Endrin mg/kg 1.59E-04Endrin aldehyde mg/kg 3.70E-04Endrin ketone mg/kg 3.21E-04Ethanol mg/kg 0.58Fluoranthene mg/kg 2.47E-03Fluorene mg/kg 1.81E-03Fluoride mg/kg 5.387Formaldehyde mg/kg 1.7gamma-BHC mg/kg 6.01E-05Heptachlor mg/kg 1.16E-04Heptachlor epoxide mg/kg 1.10E-04Hexavalent chromium mg/kg 1.129Indeno(1,2,3-cd)pyrene mg/kg 7.92E-04Iron mg/kg 46671Lead mg/kg 33.9Lithium mg/kg 64.4Magnesium mg/kg 11992Manganese mg/kg 723MCPA mg/kg 0.398MCPP mg/kg 0.202Mercury mg/kg 2.80E-02Methanol mg/kg 0.267Mirex mg/kg 2.79E-04Molybdenum mg/kg 1.642




ValueNaphthalene mg/kg 1.70E-03Nickel mg/kg 64.2Nitrate mg/kg 11.73OCDD mg/kg 1.67E-05OCDF mg/kg 1.19E-06Orthophosphate - PO4 mg/kg 863.2p,p'-Methoxychlor mg/kg 7.43E-04Perchlorate mg/kg 6.49E-04Phenanthrene mg/kg 1.86E-03Phosphorus mg/kg 863.2Potassium mg/kg 7524Pyrene mg/kg 2.59E-03Selenium mg/kg 0.536Silver mg/kg 9.50E-02Sodium mg/kg 754Strontium mg/kg 79.1Thallium mg/kg 0.629Tin mg/kg 3.83Titanium mg/kg 1865Toxaphene mg/kg 3.50E-02Vanadium mg/kg 111.8Zinc mg/kg 153Zirconium mg/kg 10.64

Abbreviations:mg/kg - milligrams per kilogram

Table 2Groundwater Comparison Values


Analyte Comparison Value Screen Type Units1,1,1-Trichloroethane 200 Primary MCL ug/L1,1,2,2-Tetrachloroethane 1 Cal MCL ug/L1,1,2-Trichloro-1,2,2-trifluoroethane 1200 Cal MCL ug/L1,1,2-Trichloroethane 5 Primary MCL ug/L1,1-Dichloroethane 5 Cal MCL ug/L1,1-Dichloroethene 6 Cal MCL ug/L1,2,3-Trichlorobenzene 2.1 SWGW RBSL ug/L1,2,3-Trichloropropane 0.005 Notification Level ug/L1,2,3-Trichloropropene 0.005 Notification Level ug/L1,2,4-Trichlorobenzene 5 Cal MCL ug/L1,2,4-Trimethylbenzene 330 Notification Level ug/L1,2-Dibromo-3-chloropropane 0.2 Primary MCL ug/L1,2-Dibromoethane 0.05 Primary MCL ug/L1,2-Dichloro-1,1,2-trifluoroethane 190000 SWGW RBSL ug/L1,2-Dichlorobenzene 600 Primary MCL ug/L1,2-Dichloroethane 0.5 Cal MCL ug/L1,2-Dichloroethenes 130 SWGW RBSL ug/L1,2-Dichloropropane 5 Primary MCL ug/L1,3,5-Trimethylbenzene 330 Notification Level ug/L1,3-Dichlorobenzene 600 Archived Advisory Level ug/L1,3-Dichloropropane 130 SWGW RBSL ug/L1,3-Dichloropropene 0.5 Cal MCL ug/L1,3-Dinitrobenzene 1.3 SWGW RBSL ug/L1,4-Dichlorobenzene 5 Cal MCL ug/L1,4-Dioxane 1 Notification Level ug/L2,2-Dichloro-1,1,1-trifluoroethane 190000 SWGW RBSL ug/L2,3,7,8-TCDD 0.00003 Primary MCL ug/L2,3,7,8-TCDD TEQ 0.00000037 TEQ ug/L2,4,5-T 130 SWGW RBSL ug/L2,4,6-Trichlorophenol 2.1 SWGW RBSL ug/L2,4,6-Trinitrotoluene 1 Notification Level ug/L2,4-Dichlorophenoxyacetic Acid (2,4-D) 130 SWGW RBSL ug/L2,4-Dimethylphenol 100 Archived Advisory Level ug/L2,6-Dinitrotoluene 0.22 SWGW RBSL ug/L2-Chlorophenol 63 SWGW RBSL ug/L2-Heptanone 280 Taste/Odor ug/L2-Hexanone 250 Taste/Odor ug/L2-Methylnaphthalene 50 SWGW RBSL ug/L3,3'-Dichlorobenzidine 0.12 SWGW RBSL ug/L4,4'-DDD 0.62 SWGW RBSL ug/L4,4'-DDE 0.44 SWGW RBSL ug/L4,6-Dinitro-o-cresol 1.3 SWGW RBSL ug/LAcetone 20000 Taste/Odor ug/LAcetonitrile 300000 Taste/Odor ug/LAcrolein 110 Taste/Odor ug/LAcrylonitrile 910 Taste/Odor ug/L



Analyte Comparison Value Screen Type UnitsAldrin 0.002 Archived Advisory Level ug/LAllyl chloride 8.9 Taste/Odor ug/Lalpha-BHC 0.015 Archived Advisory Level ug/LAluminum 200 Secondary MCL ug/LAluminum, Dissolved 13000 SWGW RBSL ug/LAniline 65000 Taste/Odor ug/LAnthracene 3800 SWGW RBSL ug/LAntimony 2.5 SSFL Comparison ug/LAntimony, Dissolved 2.5 SSFL Comparison ug/LAroclor 1016 0.5 Primary MCL ug/LAroclor 1221 0.5 Primary MCL ug/LAroclor 1232 0.5 Primary MCL ug/LAroclor 1242 0.5 Primary MCL ug/LAroclor 1248 0.5 Primary MCL ug/LAroclor 1254 0.5 Primary MCL ug/LAroclor 1260 0.5 Primary MCL ug/LArsenic 7.7 SSFL Comparison ug/LArsenic, Dissolved 7.7 SSFL Comparison ug/LBarium 150 SSFL Comparison ug/LBarium, Dissolved 150 SSFL Comparison ug/LBenzene 1 Cal MCL ug/LBenzidine 0.0003 SWGW RBSL ug/LBenzo(a)pyrene 0.2 Primary MCL ug/LBenzo(a)pyrene TEQ 0.0071 TEQ ug/LBenzoic acid 50000 SWGW RBSL ug/LBenzyl chloride 12 Taste/Odor ug/LBeryllium 0.14 SSFL Comparison ug/LBeryllium, Dissolved 0.14 SSFL Comparison ug/Lbeta-BHC 0.025 Archived Advisory Level ug/Lbis(2-Chloroethoxy)methane 38 SWGW RBSL ug/Lbis(2-Chloroethyl) ether 360 Taste/Odor ug/Lbis(2-Ethylhexyl) phthalate 4 Cal MCL ug/LBoron 340 SSFL Comparison ug/LBoron, Dissolved 340 SSFL Comparison ug/LBromochloromethane 34000 Taste/Odor ug/LBromodichloromethane 80 Primary MCL ug/LBromoform 80 Primary MCL ug/LBromomethane 8.8 SWGW RBSL ug/LButyl benzyl phthalate 78 SWGW RBSL ug/LCadmium 0.2 SSFL Comparison ug/LCadmium, Dissolved 0.2 SSFL Comparison ug/LCarbon Disulfide 160 Notification Level ug/LCarbon Tetrachloride 0.5 Cal MCL ug/LChlorate 0.8 Notification Level ug/LChlordane 0.1 Cal MCL ug/LChloride 250000 Secondary MCL ug/L



Analyte Comparison Value Screen Type UnitsChlorine 4000 Primary MCL ug/LChlorobenzene 70 Cal MCL ug/LChloroethane 16 Taste/Odor ug/LChloroform 80 Primary MCL ug/LChloromethane 5.7 SWGW RBSL ug/LChromium 14 SSFL Comparison ug/LChromium, Dissolved 14 SSFL Comparison ug/Lcis-1,2-Dichloroethene 6 Cal MCL ug/Lcis-1,3-Dichloropropene 0.5 Cal MCL ug/LCobalt 1.9 SSFL Comparison ug/LCobalt, Dissolved 1.9 SSFL Comparison ug/LCopper 4.7 SSFL Comparison ug/LCopper, Dissolved 4.7 SSFL Comparison ug/LCumene 770 Notification Level ug/LCyanides 150 Cal MCL ug/LDiazinon 1.2 Notification Level ug/LDibromochloromethane 80 Primary MCL ug/LDichlorodifluoromethane 1000 Notification Level ug/LDieldrin 0.002 Archived Advisory Level ug/LDiesel Range Organics 100 Taste/Odor ug/LDiesel Range Organics (C12-C14) 100 Taste/Odor ug/LDiesel Range Organics (C13-C22) 100 Taste/Odor ug/LDiesel Range Organics (C14-C20) 100 Taste/Odor ug/LDiesel Range Organics (C15-C20) 100 Taste/Odor ug/LDiesel Range Organics (C20-C30) 100 Taste/Odor ug/LDiesel Range Organics (C21-C24) 100 Taste/Odor ug/LDiesel Range Organics (C21-C30) 100 Taste/Odor ug/LDiesel Range Organics (C8-C11) 100 Taste/Odor ug/LDiesel Range Organics (C8-C30) 100 Taste/Odor ug/LDiethyl phthalate 10000 SWGW RBSL ug/LDimethoate 1 Archived Advisory Level ug/LDimethyl phthalate 130000 SWGW RBSL ug/LDi-n-butyl phthalate 1300 SWGW RBSL ug/LDi-n-octyl phthalate 500 SWGW RBSL ug/LDinoseb 7 Primary MCL ug/LDiphenyl ether 630 SWGW RBSL ug/LEndosulfan I 75 SWGW RBSL ug/LEndosulfan II 75 SWGW RBSL ug/LEndosulfan sulfate 75 SWGW RBSL ug/LEndrin 2 Primary MCL ug/LEthane 7500 Taste/Odor ug/LEthanol 760000 Taste/Odor ug/LEthyl acetate 2600 Taste/Odor ug/LEthyl ether 750 Taste/Odor ug/LEthylbenzene 300 Cal MCL ug/LEthylene 39 Taste/Odor ug/L



Analyte Comparison Value Screen Type UnitsEthylene glycol 14000 Notification Level ug/LFluoride 800 SSFL Comparison ug/LFormaldehyde 100 Notification Level ug/LFormic Acid 1700000 Taste/Odor ug/LFuel Hydrocarbons, C4-C12, as heavy Hydrocarbons 500 SWGW RBSL ug/LFuel Hydrocarbons, C6-C14, as JP-4 1800 SWGW RBSL ug/LFuel Hydrocarbons, C6-C15, as JP-4 1800 SWGW RBSL ug/LFuel Hydrocarbons, C6-C16, as JP-4 1800 SWGW RBSL ug/LFuel Hydrocarbons, C6-C16, C21-C24, as JP-4 1800 SWGW RBSL ug/LFuel Hydrocarbons, C6-C17, as JP-4 1800 SWGW RBSL ug/LFuel Hydrocarbons, C6-C7 500 SWGW RBSL ug/LFuel Hydrocarbons, C6-C7, C10-C16, as kerosene 1800 SWGW RBSL ug/LFuel Hydrocarbons, C7-C10, as gasoline 5 Taste/Odor ug/LFuel Hydrocarbons, C7-C14, as JP-4 1800 SWGW RBSL ug/LFuel Hydrocarbons, C7-C16, as JP-4 1800 SWGW RBSL ug/LFuel Hydrocarbons, C8-C10, as gasoline 5 Taste/Odor ug/LFuel Hydrocarbons, C8-C12, as heavy Hydrocarbons 1800 SWGW RBSL ug/LFuel Hydrocarbons, C8-C14, as heavy Hydrocarbons 1800 SWGW RBSL ug/Lgamma-BHC 0.2 Primary MCL ug/LGasoline Range Organics 5 Taste/Odor ug/LGasoline Range Organics (C12-C14) 5 Taste/Odor ug/LGasoline Range Organics (C4-C12) 5 Taste/Odor ug/LGasoline Range Organics (C6-C12) 5 Taste/Odor ug/LGasoline Range Organics (C6-C14) 5 Taste/Odor ug/LGasoline Range Organics (C6-C7) 5 Taste/Odor ug/LGasoline Range Organics (C7-C12) 5 Taste/Odor ug/LGasoline Range Organics (C8-C11) 5 SWGW RBSL ug/LHeptachlor 0.01 Cal MCL ug/LHeptachlor epoxide 0.01 Cal MCL ug/LHexachlorobenzene 1 Primary MCL ug/LHexachlorocyclopentadiene 50 Primary MCL ug/LHexachloroethane 10 Taste/Odor ug/LHexavalent Chromium 14 SSFL Comparison ug/LHexavalent Chromium, Dissolved 38 SWGW RBSL ug/LHMX 350 Notification Level ug/LHydrazine 160000 Taste/Odor ug/LIron 4100 SSFL Comparison ug/LIron, Dissolved 4100 SSFL Comparison ug/LIsophorone 5400 Taste/Odor ug/LIsopropanol 160000 Taste/Odor ug/LJet Fuel 4 (C6-C13) 1800 SWGW RBSL ug/LKepone 0.0093 SWGW RBSL ug/LKerosene (C10-C12) 1800 SWGW RBSL ug/LKerosene (C10-C14) 1800 SWGW RBSL ug/LKerosene (C6-C14) 1800 SWGW RBSL ug/LKerosene Range Organics (C11-C14) 1800 SWGW RBSL ug/L



Analyte Comparison Value Screen Type UnitsKerosene Range Organics (C15-C20) 1800 Taste/Odor ug/LLead 11 SSFL Comparison ug/LLead, Dissolved 11 SSFL Comparison ug/LMagnesium 77000 SSFL Comparison ug/LMagnesium, Dissolved 77000 SSFL Comparison ug/LManganese 150 SSFL Comparison ug/LManganese, Dissolved 150 SSFL Comparison ug/Lm-Cresol 37 Taste/Odor ug/LMercury 0.063 SSFL Comparison ug/LMercury, Dissolved 0.063 SSFL Comparison ug/LMethacrylonitrile 2100 Taste/Odor ug/LMethane 3100 SWGW RBSL ug/LMethanol 740000 Taste/Odor ug/LMethyl ethyl ketone 3800 SWGW RBSL ug/LMethyl isobutyl ketone (MIBK) 120 Notification Level ug/LMethyl methacrylate 25 Taste/Odor ug/LMethyl parathion 2 Archived Advisory Level ug/LMethyl tert-butyl ether 5 Secondary MCL ug/LMethylene chloride 5 Primary MCL ug/LMolybdenum 2.2 SSFL Comparison ug/LMolybdenum, Dissolved 2.2 SSFL Comparison ug/Lm-Xylene 1750 Cal MCL ug/Lm-Xylene & p-Xylene 1750 Cal MCL ug/LNaphthalene 17 Notification Level ug/Ln-Butylbenzene 260 Notification Level ug/Ln-Hexane 6.4 Taste/Odor ug/LNickel 17 SSFL Comparison ug/LNickel, Dissolved 17 SSFL Comparison ug/LNitrate-N 10000 Primary MCL ug/LNitrate-NO3 45000 Cal MCL ug/LNitrite-N 1000 Primary MCL ug/LNitrobenzene 110 Taste/Odor ug/Ln-Nitrosodiethylamine 0.01 Notification Level ug/Ln-Nitrosodimethylamine 0.01 Notification Level ug/Ln-Nitrosodi-n-propylamine 0.01 Notification Level ug/Ln-Nitrosodiphenylamine 16 SWGW RBSL ug/Ln-Propylbenzene 260 Notification Level ug/Lo + p Xylene 1750 Cal MCL ug/Lo-Chlorotoluene 140 Notification Level ug/Lo-Cresol 630 SWGW RBSL ug/LOil Range Organics (C23-C32) 1800 SWGW RBSL ug/Lo-Toluidine 11000 Taste/Odor ug/Lo-Xylene 1750 Cal MCL ug/Lp,p'-Methoxychlor 30 Cal MCL ug/LParathion 40 Archived Advisory Level ug/Lp-Chlorotoluene 140 Notification Level ug/L



Analyte Comparison Value Screen Type Unitsp-Cresol 63 SWGW RBSL ug/Lp-Dinitrobenzene 1.3 SWGW RBSL ug/LPentachloronitrobenzene 20 Archived Advisory Level ug/LPentachlorophenol 1 Primary MCL ug/LPentanal 17 Taste/Odor ug/LPerchlorate 6 Cal MCL ug/LPhenanthrene 3800 SWGW RBSL ug/LPhenol 4200 Archived Advisory Level ug/LPolychlorinated biphenyls 0.5 Primary MCL ug/LPotassium 9600 SSFL Comparison ug/LPotassium, Dissolved 9600 SSFL Comparison ug/LPropachlor 90 Notification Level ug/LPyrene 380 SWGW RBSL ug/LPyridine 950 Taste/Odor ug/LRDX 0.3 Notification Level ug/Lsec-Butyl alcohol 19000 Taste/Odor ug/Lsec-Butylbenzene 260 Notification Level ug/LSelenium 1.6 SSFL Comparison ug/LSelenium, Dissolved 1.6 SSFL Comparison ug/LSilver 0.17 SSFL Comparison ug/LSilver, Dissolved 0.17 SSFL Comparison ug/LSodium 190000 SSFL Comparison ug/LSodium, Dissolved 190000 SSFL Comparison ug/LStrontium 800 SSFL Comparison ug/LStrontium, Dissolved 800 SSFL Comparison ug/LStyrene 100 Primary MCL ug/LSulfate 376000 SSFL Comparison ug/Ltert-Butyl alcohol 12 Notification Level ug/Ltert-Butylbenzene 260 Notification Level ug/LTetrachloroethene 5 Primary MCL ug/LThallium 0.13 SSFL Comparison ug/LThallium, Dissolved 0.13 SSFL Comparison ug/LTin 2.4 SSFL Comparison ug/LTin, Dissolved 2.4 SSFL Comparison ug/LToluene 150 Cal MCL ug/LTotal Dissolved Solids 500000 Recommended SMCL ug/LTotal Extractable Hydrocarbons C10-C18 1800 SWGW RBSL ug/LTotal Extractable Hydrocarbons C16-C25 1800 SWGW RBSL ug/LTotal Hydrocarbons C8-C18 1800 SWGW RBSL ug/LTotal Petroleum Hydrocarbons (as Kerosene) 1800 SWGW RBSL ug/LToxaphene 3 Primary MCL ug/Ltrans-1,2-Dichloroethene 10 Cal MCL ug/Ltrans-1,3-Dichloropropene 0.81 SWGW RBSL ug/LTrichloroethene 5 Primary MCL ug/LTrichlorofluoromethane 150 Cal MCL ug/LTurbidity 5 Secondary MCL NTU



Analyte Comparison Value Screen Type UnitsVanadium 2.6 SSFL Comparison ug/LVanadium, Dissolved 2.6 SSFL Comparison ug/LVinyl acetate 88 Taste/Odor ug/LVinyl chloride 0.5 Cal MCL ug/LXylenes, Total 1750 Cal MCL ug/LZinc 6300 SSFL Comparison ug/LZinc, Dissolved 6300 SSFL Comparison ug/L

Abbreviations:Cal - CaliforniaMCL - maximum contaminant levelNTU - nephelometric turbidity unitRBSL - risk-based screening levelSMCL - secondary maximum contaminant levelSSFL - Santa Susana Field LaboratorySWGW - site-wide groundwaterTEQ - toxicity equivalent quotientug/L - micrograms per liter

Table 3Meteorological Inputs

(Pierce College, Canoga Park, CA Meteorological Station)

Month Temp Cloud Cover

Relative Humidity

Short Wave Albedo Precip Storm

Length# of

Storms Season

(Celsius) (fraction) (fraction) (fraction) (cm/ month) (days) (storms/

month) (days)Oct 19.50 0.350 0.725 0.250 1.372 0.130 0.55 30.4Nov 14.94 0.400 0.665 0.200 6.299 0.420 1.77 30.4Dec 12.11 0.500 0.645 0.200 5.436 0.410 2.50 30.4Jan 12.28 0.500 0.650 0.200 8.407 0.570 3.50 30.4Feb 13.33 0.450 0.685 0.200 8.382 0.470 3.11 30.4Mar 14.00 0.500 0.720 0.200 7.315 0.360 3.55 30.4Apr 16.00 0.500 0.720 0.200 2.591 0.320 1.88 30.4May 18.44 0.450 0.745 0.250 0.457 0.070 0.20 30.4Jun 21.44 0.400 0.760 0.250 0.051 0.040 0.09 30.4Jul 24.67 0.300 0.770 0.250 0.010 0.010 0.09 30.4Aug 24.89 0.250 0.775 0.250 0.457 0.040 0.13 30.4Sep 22.89 0.250 0.755 0.250 0.660 0.070 0.41 30.4Avg 17.87 0.404 0.718 0.225 3.453 0.243 1.48 30.4Annual Total 41.44 17.8

Table 4Chemical and Physical Data for Preliminary Inorganic Chemicals

Vadose Zone Mass Flux to Groundwater Transport Modeling

Al Sb Be Cd Cu Pb Hg Ni AgParameter Units

Water Solubility mg/L 5.94E+04 2.30E+04 1.49E+05 1.23E+05 4.21E+05 9.58E+03 6.00E-02 4.22E+05 7.05E+04

Henry's Law Constant m3-atm/mol 2.44E-02 2.44E-02 2.44E-02 2.44E-02 2.44E-02 2.44E-02 2.44E-02 2.44E-02 2.44E-02Molecular Weight g/mol 26.98 121.78 9.01 112.41 63.55 207.2 200.59 58.69 107.87Soil Partition Coefficient L/kg 772 879 892 711 862 932 70 1,041 247Organic Carbon Adsorption Coefficient L/kg 0 0 0 0 0 0 0 0 0

Air Diffusion Coefficient cm2/sec 0 0 0 0 0 0 0.0307 0 0

Water Diffusion Coefficient cm2/sec 0 0 0 0 0 0 6.30E-06 0 0

Base Hydrolysis Rate Constant day-1 0 0 0 0 0 0 0 0 0

Neutral Hydrolysis Rate Constant day-1 0 0 0 0 0 0 0 0 0

Acid Hydrolysis Rate Constant day-1 0 0 0 0 0 0 0 0 0

Liquid Phase Biodegradation Rate Constant day-1 0 0 0 0 0 0 0 0 0

Not Proposed for Use in Vadose Zone Transport Modeling

Solid Phase Biodegradation Rate Constant day-1

Chemical Valance g/molLigand Dissociation Constant dimensionlessMoles Ligand/Mole Chemical dimensionlessMolecular Weight Ligand g/mol

Sources: Element Chemical Data - SESOIL Databases and CRC Press (1986).

Chemical Compound:

Table 5Chemical and Physical Data for Preliminary Volatile Organic Chemicals

Vadose Zone Mass Flux to Groundwater Transport ModelingTCE cis-1,2-DCE Vinyl Chloride

Parameter UnitsWater Solubility mg/L 1,100 3,500 2,800

Henry's Law Constant m3-atm/mol 1.00E-02 4.08E-03 2.70E-02Molecular Weight g/mol 131 96.94 63Organic Carbon Adsorption Coefficient L/kg 94 35.5 19

Air Diffusion Coefficient cm2/sec 0.079 0.0736 0.11

Water Diffusion Coefficient cm2/sec 9.10E-06 1.13E-05 1.20E-06

Base Hydrolysis Rate Constant day-1 6.18E-9/0 4.88E-14/0 0

Neutral Hydrolysis Rate Constant day-1 0 0 1.05E-4/0

Acid Hydrolysis Rate Constant day-1 0 0 0

Liquid Phase Biodegradation Rate Constant day-11.40E-4/ 5.73E-4/2.50E-3/0

8.62E-5/2.37E-3/0

3.3E-4/7.2E-3/0

Not Proposed for Use in Vadose Zone Transport Modeling

Solid Phase Biodegradation Rate Constant day-1

Chemical Valance g/molLigand Dissociation Constant dimensionlessMoles Ligand/Mole Chemical dimensionlessMolecular Weight Ligand g/mol

Sources: VOC chemical Data - SESOIL chemical database, CRWR (2003); USEPA (1999); SRC (1997, 1999); Howard et al (1991); CRC Press (1986)

Chemical Compound:

Table 6Physical Properties of Lithologic Units

Vadose Zone Mass Flux to Groundwater Modeling

Bulk density (g/cm3)a

Intrinsic permeability

(cm2)b

Soil pore disconnect-

edness index) Porosityc

Organic carbon content

(% weight)dRecharge flux

(cm/yr)e

Alluvium/ colluvium 1.60 1.00E-08 Adjust 0.3 0.027 6.6 - 9.4

Weathered sandstone 2.16 1.80E-10 Adjust 0.21 0.021 3.3 - 4.8

Weathered siltstone 2.15 1.80E-11 Adjust 0.186 0.41 0.07 - 0.8

Unweathered sandstone 2.42 4.20E-12 Adjust 0.136 0.021 Use weathered value

Unweathered siltstone 2.47 1.40E-15 Adjust 0.24 0.41 Use weathered value

Lithologic Properties

a - from Table 4 of App 4-O of Draft Groundwater RI Report (MWH, 2009)b - calculated from hydraulic conductivity values in Site Conceptual Model Element 2-3 (Groundwater Advisory Panel, 2009)c - from Site Conceptual Model Element 2-2 (Groundwater Advisory Panel, 2009). Rock values are matrix porosity.d - from Site Conceptual Model Element 3-3 (Groundwater Advisory Panel, 2009)e - from Table 4-2 of Appendix 6-A of Draft Groundwater RI Report (MWH, 2009)

Lithology: