111111111111111111111111111111111111111111111 …holme roberts and owens, (mr. daniel j. dunn), 1700...

111111111111111111111111111111111111111111111 1086766 - R8 SDMSDEPARTMENT OF THE ARMY

BASE REALIGNMENT AND CLOSURE ROCKY MOUNTAIN ARSENAL

5650 HAVANA STREET, BUILDING 129 /y/;~' COMMERCE CITY, COLqRADO 80022-1748

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DAIM-ODB-RM 2 December 2008

MEMORANDUM FOR U.S. Environmental Protection Agency, (Mr. Greg Hargreaves), Region VIlJ, Mail Code 8EPR-F, 1595 Wynkoop Street, Denver, Colorado 80202- 1129

SUBJECT: Explanation of Significant Differences (ESD) for Munitions (Testing) Soil Remediation Project Rocky Mountain Arsenal Federal Facility Site

I. Enclosed for your information is the signed Explanation of Significant Differences (ESD) for Munitions (Testing) Soil Remediation Project Rocky Mountain Arscnal Federal Facility Site. Revision O. The final draft ESD was provided for review and comment on 3 September 2008.

2. If you have any questions, please contact Mr. James 1. Green at 303-289-0412.

Enel ~ nt

EXPLANATION OF SIGNIFICANT DIFFERENCES FOR MUNITIONS (TESTING) SOIL REMEDIATION PROJECT

ROCKY MOUNTAIN ARSENAL FEDERAL FACILITY SITE

Prepared by: Tetra Tech EC, Inc.

Prepared for: Rocky Mountain Arsenal Committee

Department of the Army Shell Oil Company

U.S. Fish and Wildlife Service U.S. Environmental Protection Agency

Colorado Department of Public Health and Environment

This document is the property of Rocky Mountain Arsenal Remediation Venture Office and was prepared by Tetra Tech EC, Inc. It is provided on the condition that it will neither be reproduced, copied, or issued to a third party; will be used solely for the intended purpose; and will be used solely for the execution or review of the engineering, remediation, and/or construction of the subject project.

Revision Prepared By Reviewed By .r;" Approved By Date Pages Affected 0 S.AChe~ M. Filipowitc ~

J. eoen J,.. / M. Dollar ir)::>

November 3, 2008 All

Rocky Mountain Arsenal Explanation of Significant Differences Munitions (Testing) Soil Remediation Revision 0 WBS 2.03.12.02 . November 3, 2008

CONTENTS

1.0 INTRODUCTION I

2.0 SITE HISTORY, CONTAMINATION AND SELECTED REMEDy 3

2.1 RMA Operational History : 3 2.2 Definitions 4 2.3 Munitions Testing Area History and Contamination Summary 4

2.3.1 CSA-2c 5 2.3.2 ESA-Ia, ESA-Ib, ESA-lc and ESA-Id 6 2.3.3 ESA-4a 6 2.3.4 ESA-4b 7 2.3.5 MT29-1 8 2.3.6 BA 10, Surface Bum Area 8 2.3.7 BT32-10 8 2.3.8 BA 9a, Parcel 2 8 2.3.9 DREZ 9

2.4 Summary of the Selected On-Post Remedy 9 2.5 Summary of the Selected Remedy for Munitions Testing Soil 9 2.6 Munitions Testing Remedy Implementation 10

3.0 BASIS FOR THE ESD 10

3.1 Soil Volume Decrease due to TCLP Sampling 11 3.2 Soil Volume Increase due to Boundary Modifications 13 3.3 Debris Removal from CSA-2c 14 3.4 ESA-4a Boundary Modifications 14 3.5 Additional MEC Remediation Areas 16

3.5.1 BA 10 Surface Burn Area 16 3.5.2 BT32-10 16 3.5.3 CSA-2c 17 3.5.4 BA 9a, Parcel 2 : 18 3.5.5 DREZ 18

3.6 Additional Scope for ESA-4b 19 3.7 Basis for Cost Change 21

4.0 DESCRIPTION OF SIGNIFICANT DIFFERENCES 22

4.1 Changes to Munitions Testing Project Remediation 22 4.2 Summary ofCost Change 23

5.0 SUPPORT AGENCY COMMENTS 23

6.0 PUBLIC PARTICIPATION COMPLIANCE 25

7.0 STATUTORY DETERMINATIONS 26

8.0 REFERENCES 27

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Table 2.6-1

Table 3.1-1

Table 3.7-1

Table 4.1-1

Table 4.1-2

Figure 1.0-1

Figure 1.0-2

TABLES

Munitions Testing Project Implementation

Sample Results and Comparison to TCLP Limits

Summary of Costs for Munitions (Testing) Soil Remediation

Changes to Excavation Volumes for Munitions Testing Soil Remediation Sites

Changes to MEC Remediation Areas for the Munitions Testing Project

FIGURES

Rocky Mountain Arsenal Regional Reference

Rocky Mountain Arsenal Munitions Testing Project Areas

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ACM

BA

bcy

CCR

CDPHE

CERCLA

CFR

COC

CSA

DCN DDESB

DMM DREZ

ELF EPA

ESA

ESD

EZ

HE

HH HWL

JARDF

MEC NCP

NPL NW

OU

PMC

PI

QA

RAB

RCRA

RI RMA

ROD

ACRONYMS AND ABBREVIATIONS

Asbestos-Containing Material

Borrow Area

bank cubic yard(s)

Construction Completion Report

Colorado Department of Public Health and Environment

Comprehensive Environmental Response, Compensation and Liability Act

Code of Federal Regulations

Contaminant of Concern

Central Study.Area

Design Change Notice

Department of Defense Explosives Safety Board

Discarded Military Munitions

Demolition Range Exclusion Zone

Enhanced Hazardous Waste Landfill

U. S. Environmental Protection Agency

Eastern Study Area

Explanation of Significant Differences

Exclusion Zone

High Explosive

Human Health

Hazardous Waste Landfill

Joint Administrative Record Document Facility

Munitions and Explosives of Concern

National Contingency Plan

National Priorities List

Northwest

Operable Unit

Program Management Contractor

Priority I

Quality Assurance

Restoration Advisory Board

Resource Conservation and Recovery Act

Remedial Investigation

Rocky Mountain Arsenal

Record of Decision


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SC&A

SEC

SET SQCSR

SW

TCHD

TCLP

UXO

Sanford Cohen and Associates

Site Evaluation Criteria

Summary and Evaluation Team

Soil Quantity Calculation Summary Report

Southwest

Tri-County Health Department

Toxicity Characteristic Leaching Procedure

Unexploded Ordnance


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1.0 INTRODUCTION This Explanation of Significant Differences (ESD) documents a significant change in a portion of the remedy for the Munitions (Testing) Soil Remediation, referred to in the rest of this document as the Munitions Testing Project, of the Rocky Mountain Arsenal (RMA) Federal Facility Site. The RMA On-Post Operable Unit (OU) is a federally owned facility located in southern Adams County, Colorado, approximately 10 miles northeast of downtown Denver, directly north of the former Stapleton International Airport and west of Denver International Airport as shown on Figure 1.0-1. The RMA On-Post OU site encompasses approximately 5.6 square miles and is currently on the U.S. Environmental Protection Agency (EPA) National Priorities List (NPL) for environmental cleanup as a result of contamination released during previous RMA operations. The Munitions Testing Project consists of twelve separate areas located in the northeast part of the On-Post OU as shown on Figure 1.0-2.

The Record of Decision (ROD), which describes the remedy for the entire On-Post OU ofRMA, was signed by the U.S. Army (Army), the EPA, and the Colorado Department of Public Health and Environment (CDPHE) on June II, 1996 (FWENC 1996b). The selected remedy includes 31 cleanup projects for soil, structures, and treatment of groundwater contamination (pMRMA 2006). As the site-wide remediation is completed, most of the On-Post OU ofRMA will become a National Wildlife Refuge, as provided for in Public Law #102-402.

The Army is the lead agency for RMA and is issuing this ESD as part of its responsibilities under Section 117 of the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) of 1980, as amended by the Superfund Amendment and Reauthorization Act of 1986, and pursuant to the National Contingency Plan (NCP), 40 Code of Federal Regulations (CFR) Section 300.435(c)(2)(i). The NCP requires an ESD when the remedial action taken differs significantly from the remedy selected in the ROD with respect to scope, performance or cost. Regulatory Agency oversight is conducted by the EPA, CDPHE, and Tri-County Health Department (TCHD). The TCHD oversees local public health and environmental issues in Adams, Arapahoe, and Douglas Counties.

This ESD summarizes modifications to the remedy for the Munitions Testing Project that result from new information developed by the Army since the ROD was signed. Significant changes include decrease in soil remediation volume, increase in project area for Munitions and Explosives of Concern (MEC) remediation, and increase in project cost. These changes, while resulting in the need for an ESD, do not alter the overall hazardous waste management remedy that was selected in the ROD. The remedy requirements in the ROD include locating unexploded ordnance (UXO) using geophysical survey, excavation ofUXO for detonation or other demilitarization process, and excavation of munitions debris and associated soil in excess of TCLP criteria with disposal in the on-site hazardous waste landfill (HWL). During design of the remedy for the Munitions Testing Project, soil sampling and toxicity characteristic leaching procedure (TCLP) evaluation were conducted to determine the volume of soil in excess of TCLP criteria. The results indicated that none of the soil in contact with the munitions debris exceeded the regulatory levels. Therefore, according to the ROD, the soil did not present a risk and did not require removal resulting in a decrease in soil remediation volume. Also during design, the lateral and vertical boundaries of remediation areas were modified based on extensive field


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investigation of debris distribution. These boundary changes were applied to visually impacted burn areas and generally resulted in larger remediation areas and increased remediation volume. However, the volume decrease due to TCLP evaluation was much greater than the volume increase due to boundary adjustments, resulting in an overall 61 percent decrease in munitions debris and associated soil volume.

Where soil removal was not required, remediation of munitions debris was accomplished through geophysical anomaly location, characterization and removal. During debris removal from Central Study Area (CSA)-2c, Asbestos-Containing Material (ACM) was identified mixed within the soil. Therefore, initial efforts at CSA-2c included'munitions debris removal and ACM removal. Also, CSA-2c was identified in the ROD as a munitions debris area and a potential biota risk soil area. Subsequent to initial munitions debris and ACM removal efforts, biota soil excavation was conducted. During biota soil removal, additional ACM was identified and removed, resulting in additional scope for the Munitions Testing Project.

Remediation ofMEC was performed throughout the Munitions Testing Project area in accordance with the ROD. However, the total project area in the ROD was approximately 55 acres, including approximately 42 acres for Eastern Study Area (ESA)-4a, Munitions Impact Area. During project implementation, the ESA-4a remediation area was expanded several times based on new information developed during extensive site record reviews and geophysical surveys. The final remediation area for ESA-4a was expanded to over 224 acres, a more than five-fold increase. In addition, several areas were identified with MEC potential that were not included in the ROD. Due to their close proximity and similar historical use as munitions testing areas, these areas were added to the Munitions Testing Project and include an expanded area around CSA-2c, Borrow Area (SA) 9a Parcel 2, a surface burn area located within BA lOin Section 31, an area surrounding trench BT32-1 0 in Section 32, and an exclusion zone surrounding the Section 29 RMA Demolition Range. Overall, the Munitions Testing Project MEC remediation area expanded to 710 acres, a more than ten-fold increase.

These scope changes lead to significant cost growth for the project. The ROD-estimated cost for implementation of the Munitions Testing Project was $2.75 million. Project costs for the remediation scope identified in the ROD decreased approximately $0.5 million, primarily due to elimination of soil excavation, based on soil sampling and TCLP evaluation, for ESA-4a. However, additional project scope far outweighed the savings from the initial remediation. The most significant cost growth factor was the expansion of ESA-4a MEC remediation area and addition of the Demolition Range Exclusion Zone (DREZ). Together these areas contributed $3.7 million to the overall project cost increase. Additional remediation requirements for the RMA Demolition Range contributed another $0.6 million. Other scope additions contributing to the overall cost increase include removal of ACM from CSA-2c ($0.2 million) and the addition ofBA 9a Parcel 2 and CSA-2c MEC remediation ($0.3 million).

Overall, project costs increased from a ROD-estimated $2.75 million to approximately $7.03 million. This represents a cost increase of approximately 155 percent over the ROD estimate. These changes, while resulting in the need for an ESD, do not alter the overall hazardous waste management remedy that was selected in the ROD.


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This ESD will become part of the Administrative Record as required by the NCP, 40 CFR 300.825(a)(2) (EPA 1990). The Administrative Record is available to the public at the Joint Administrative Record Document Facility (JARDF) that is located on the RMA in Building 129, Room 1010. The JARDF is open Monday through Friday between Noon and 4 pm or by appointment. The telephone number for the JARDF is 303-289-0983.

2.0 SITE HISTORY, CONTAMINATION AND SELECTED REMEDY

2.1 RMA Operational History The RMA was established in 1942 by the Army to manufacture chemical warfare agents and agent-filled munitions and to produce incendiary munitions for use in World War 11. Following the war and through the early 1980s, the facilities continued to be used by the Army. Beginning in 1946, some facilities were leased to private companies to manufacture industrial and agricultural chemicals. Shell Oil Company, the principal lessee, manufactured pesticides from 1952 to 1982 at the site. Common industrial and waste disposal practices during those years resulted in contamination of structures, soil, surface water, and groundwater.

The On-Post au is one of two operable units at RMA. The Off-Post au primarily addresses groundwater contamination north and northwest ofRMA. The On-Post au addresses contamination within the approximately 26.6 square miles ofRMA. As of August 2006, approximately 21 square miles of the On-Post au have met cleanup requirements and are no longer part of the NPL site. Implementation of the remedy for the remaining approximately 5.6 square miles is ongoing and is scheduled for completion in 2010.

The contaminated areas within the On-Post au included approximately 3,000 acres of soil, 15 groundwater plumes, and 798 structures. The most higWy contaminated areas were identified in South Plants (the central processing area, Hex Pit, Buried M-I Pits, and the chemical sewers), Basins A and F, the Lime Basins, the Complex (Army) Trenches and the Shell Disposal Trenches. The primary contaminants found in soil and groundwater in these areas are organochlorine pesticides, solvents, metals, and chemical warfare agent byproducts.

The areas with the highest levels and/or the greatest variety of contaminants are located.in the central manufacturing, transport, and waste disposal areas. The highest contaminant concentrations tend to occur in soil within five feet of the ground surface, although exceptions are noted, particularly where burial trenches, disposal basins, or manufacturing complexes were located.

The characteristics and locations of the groundwater plumes suggest that the greatest contaminant releases to the groundwater have occurred from Basin A and the Lime Basins, the South Plants chemical sewer, the South Plants tank farm and production area, the Complex (Army) and Shell Trenches in Section 36, and the former Basin F. The Motor PoollRail Yard and North Plants areas have been other sources of contaminant releases to the groundwater.

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2.2 Definitions The tenns "unexploded ordnance" (UXO) and "ordnance and explosives" presented in the ROD refer to hazardous military munitions. Based on Department of Defense direction, the new tenn MEC has replaced the previously mentioned tenns when describing hazardous military munitions (DA 2005). The updated defInitions are provided below:

Discarded Military Munitions CDMM)

Military munitions that have been abandoned without proper disposal or removed from storage in a military magazine or other storage area for the purpose of disposal. The tenn does not include unexploded ordnance, military munitions that are being held for future use or planned disposal, or military munitions that have been properly disposed of consistent with applicable environmental laws and regulations (10 U.S.C. 2710 [e] [2D.

Munitions Constituents

Any materials originating from UXO, DMM, or other military munitions, including explosive and non-explosive materials; and emission, degradation, or breakdown elements of such ordnance or munitions (10 U.S.C. 2710 [e] [3D.

Munitions and Explosives of Concern CMEC)

This tenn, which distinguishes specifIc categories of military munitions that may pose unique explosives safety risks, means:

(a) UXO, as defIned in 10 U.S.C. 101 (e) (5);

(b) DMM, as defmed in 10 U.S.C. 2710 (e) (2); or

(c) Munitions constituents (e.g., mT, RDX), as deflned in 10 U.S.C. 2710 (e) (3), present in high enough concentrations to pose an explosive hazard.

Munitions Debris

Remnants of munitions (e.g., penetrators, projectiles, shell casings, links, fIns) remaining after munitions use, demilitarization or disposal.

Unexploded Ordnance CUXO)

Military munitions that:

(a) have been primed, fuzed, armed, or otherwise prepared for action;

(b) have been fIred, dropped, launched, projected, or placed in such a manner as to constitute a hazard to operations, installations, personnel, or material; and

(c) remain unexploded whether by malfunction, design, or any other cause (10 U.S.C. 101 [e] [5] [A] through [CD.

2.3 Munitions Testing Area History and Contamination Summary The Munitions Testing Project consists of seven ROD-identifIed areas and fIve additional areas identifIed during design or implementation located in the northeastern portion of RMA as shown on Figure 1.0-2. These areas were used historically for the testing and destruction of conventional, non-chemical munitions and typically contain slag, debris, and potential MEC and


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Rocky Mountain ArsenaJ Explanation of Significant Differences Munitions (Testing) Soil Remediation Revision 0 WBS 2.03. 12.02 November 3, 2008

therefore represent potential physical hazards. The following ROD-identified areas are included in the Munitions Testing soil remedy:

• Site CSA-2c, Munitions Test Site

• Site ESA-I a, Surface Burn Site

• Site ESA-Ib, Surface Burn Site

• Site ESA-I c, Surface Burn Site

• Site ESA-Id, Surface Burn Site

• Site ESA-4a, Munitions Impact Area

• Site ESA-4b, Demolition Area

One additional Munitions Testing area identified in the ROD, the Munitions Incineration Site (CSA-2d), was transferred to the Existing (Sanitary) Landfills Remediation Project due to proximity to the Section 36 landfill and was remediated as part of that project (TtFW 2004b).

During design and implementation, five additional areas were identified for remediation under the Munitions Testing Project:

• MT29-1, Surface Debris Site

• BA 10 Surface Burn Area

• BT32-10, Target Characterization and Recovery

• BA 9a, Parcel 2

• DREZ

A summary of the information collected during the Remedial Investigation (RI)/Feasibility Study process can be found in various Contamination Assessment Reports, the RI Summary Report (Ebasco 1992) and in thtl Detailed Analysis of Alternatives Report (FWENC 1995). A summary of use and contamination history for each area is provided below.

2.3.1 CSA-2c Area CSA-2c, Munitions Test Site 36-6, was used in the 1940s for static proof testing of 100pound M47 incendiary bombs filled with napalm. The area, located in Sections 25 and 36, consisted of a graded field with approximate dimensions of 900 feet by 900 feet. The bombs were detonated on a concrete pad in the center of the site. After detonation, remaining components of the M47 bomb were gathered and salvaged. The RI for this area was performed in the summer of 1986 and included soil sampling and a geophysical investigation. Soil sample results did not indicate concentrations of contaminants of concern (COC)s exceeding the human health (HH) site evaluation criteria (SEC). Geophysical survey results provided no evidence of disposal trenches (ESE 1988£). A large magnetic anomaly was identified in the northeast portion of the site; however, this area was later identified as a shallow trash pit containing nails, concrete and pieces of copper wire. After completion of the RI, two small areas within Munitions Test


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Site 36-6 boundary were identified for remediation. A November 1997 site visit found no surface disturbances or metal debris by which to confirm the site boundaries (FWENC 1999a).

2.3.2 ESA-la, ESA-lb, ESA-lc and ESA-ld

In 1957, four areas in the northeast portion ofRMA were designated for demilitarization ofM76 incendiary bombs. These areas, identified in the RI as ESA-1a, ESA-1b, ESA-Ic and ESA-1d, were placed symmetrically around the intersection of Ninth Avenue and F Street as shown on Figure 1.0-2. The M76 bombs were 500-pound bombs filled with PTl, a complex paste mixture of magnesium dust, magnesium oxide, carbon, petroleum distillate and asphalt. More than 22,000 bombs were destroyed by controlled detonation in the four demolition areas between 1957 and 1959 (ESE 1987). Scrap metal remaining following demolition was gathered and salvaged.

The RI for these areas was conducted in the summer of 1986 and consisted of soil sampling and a geophysical investigation. Soil sample results did not indicate concentrations of COCs exceeding the HH SEC. A geophysical survey was conducted at each area to identify areas of metal disposal. At ESA-I b and ESA-I d the geophysical survey was conducted in two phases. Following the first stage, approximately 6- to 12-inches of debris and soil were removed and a second survey was completed to identify potential areas of buried metal. Results from the geophysical surveys confirmed that metal debris and slag material was generally confined to the upper one foot of soil (ESE 1987, ESE 1988a, ESE 1988c, ESE 1988g). There was no evidence of burial trenches within these areas. These areas were identified as munitions debris and potential UXO areas in the ROD. A November 1997 site visit found these areas covered with slag, charred soil and scattered metal debris (FWENC 1999a). Soil mounds generated from soil and debris removal during the RI at ESA-1 b and ESA-I d were still present.

2.3.3 ESA-4a

Site ESA-4a, located in the southeast quarter of Section 30, was used as a mortar impact area from 1946 until the early 1950s. The 4.2-inch mortar shells contained high explosive, white phosphorus, or smoke filler, or were 'dud' practice rounds. The mortar rounds were fued from a site due west of this site, near the western limits of Section 26. Historical information and evidence, described in the RI reports for the sites in this project area, support the belief that 4.2inch mortar rounds were the only military munitions fued into this area.

This area was initially identified as Site 30-1 for the RI and encompassed the entire southeast quadrant of Section 30. The Phase I investigation was conducted in spring 1986 and consisted of soil sampling and a geophysical investigation (ESE 1988h). Phase II was completed in the spring of 1988 and consisted of additional soil sampling in geophysical anomaly areas identified during Phase I (ESE 1988b). Soil sample results did not indicate concentrations of COCs exceeding the HH SEC. Geophysical results did not identify any concentrated areas of buried metal debris within ESA-4a. Field observations revealed many small shallow depressions, about six-feet wide and three-feet deep, which were originally thought to be characteristic of impact craters. A large number of small pieces of shrapnel were found in and around these craters. A surface sweep conducted over a one-acre area to characterize the debris at this site recovered 14 fuzes, 20 blasting caps, two 40mm grenades, and one dud smoke grenade (ESE 1988h).


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Two areas ofnote are also located within the ESA-4a boundary. The Demil Facility (Site 30-5) was used to remove fuze and burster assemblies from various munitions. The explosive components were detonated in Section 30. The Demil Facility operated between 1962 and 1969. The buildings and foundations were dismantled in 2000. The size of this facility is approximately one-acre. The Rosenzweig Homestead is also located within ESA-4a east of the Demil Facility near F Street. The homestead is approximately two-acres in size and consists ofremnants of a farmhouse, storage silo, barn, fences and underground appurtenances.

During the Rl, an evaluation of Site 30-1 noted the location of impact craters and a concrete bunker used to observe mortar impacts. The concrete bunker had observation windows facing northwest and northeast suggesting that the main impact range was north of the bunker (ESE 1988h). A 42-acre parallelogram was used to bound the mortar impact area and the site was designated ESA-4a. This main impact area was identified as the primary area where MEC was expected to potentially exist and was incorporated in the ROD as the ESA-4a remediation boundary.

2.3.4 ESA-4b

Area ESA-4b, Demolition Area, is located in the northwest quarter of Section 29. The area covers about 4.5 acres and was surrounded on all four sides by berms 6- to 8-feet high. ESA-4b was used in the late 1960s and early 1970s for the demolition and disposal of rocket motors, rocket propellants, miscellaneous explosives, and incendiary devices such as 500-pound M76 bombs. This area was also used during the 1970s to detonate small quantities of explosives confiscated by local law enforcement agencies (ESE 1988e). In 1985, the Army discontinued all explosive disposal operations on the RMA Demolition Range.

The Rl for this area was included as part of a much larger investigation area, 29-4, and was completed in two phases. Phase I was conducted in sununer 1986 and consisted of soil sampling and a geophysical investigation. Phase II was completed in the spring of 1988 and included exploratory trench excavations and additional soil sampling (ESE 1988d). Soil sample results did not indicate concentrations of COCs exceeding the HH SEC. Geophysical survey results did not provide evidence of large-scale disposal of 500-pound bombs; however, field observations revealed abundant surficial metal debris and a IS-foot by 30-foot by 6-foot-deep pit containing metal debris, including a 55-gallon drum (ESE 1988e). Therefore, this area was identified as a munitions debris and potential UXO area in the ROD.

In November 1999, the RMA Demolition Range was formally reactivated per the Department of Defense Explosives Safety Board (DDESB)-approved Site Safety Submission for Reactivation of Demolition Range (DDESB 1999). Since remedy operations began, the RMA Demolition Range has facilitated the disposal of more than 9,000 MEC recovered from various RMA locations. During Program Management Contractor (pMC) operation of the RMA Demolition Range, explosive disposal techniques (e.g., placement of donor explosives) were used with the objectives of completely disposing each MEC and effectively reducing the potential for kickout during each disposal event. Once the characterization of the DREZ began in July of 2005, the PMC started employing engineering controls to contain potential kickout per Use ofSandbags for Mitigation ofFragmentation and Blast Effects Due to Intentional Detonation ofMunitions


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(USACE 1998) during all explosive disposal operations performed on the RMA Demolition Range.

2.3.5 MT29-1 Site MT29-1, a surface debris area, is located in the northwest quarter of Section 29, northeast of ESA-Ic. This area was investigated as part of the larger 29-4 area and was later identified as ESA-4c. Field observations during the RI noted a trench containing empty decontamination fluid drums, metal lids, miscellaneous metal debris and a mound containing wire and miscellaneous metal debris (ESE 1988e). Soil sample results did not indicate concentrations ofCOCs exceeding the HH SEC. Because the debris identified was not munitions related, the ROD did not identify this area for remediation. However, based on results from the geophysical survey completed in 1998, a field reconnaissance was performed to investigate the geomagnetic features indicated by the survey. Although most of the debris was identified as non-munitions-related, the presence of munitions debris was verified and the area was added to the Munitions Testing Project for remediation (FWENC 1999a).

2.3.6 BA 10, Surface Burn Area BA 10, Surface Burn Area, is located in the east-central area of Section 31. The area is approximately 200-feet by 200-feet. BA 10 is being developed as a borrow source for use by several remediation projects. During characterization of soils in BA 10, munitions debris resulting from an E-139 bomblet was found on the surface in the former burn area. As a result, the area was added to the Munitions Testing Project (FWENC 2003a).

2.3.7 BT32-10 Site BT32-10 was a burn pit located approximately 400 feet west of Burial Trenches site ESA2a-6 in the west-central part of Section 32. This site was discovered during examination of historical aerial photographs dated from 1956 through 1962 and was added to the Burial Trenches Project (FWENC 2000b). Remediation consistent with the Burial Trenches remedy was performed in 2000. During the initial remediation, MEC was recovered from the area surrounding BT32-1 O. Unlike other trenches in the Burial Trenches Project, the surface area surrounding the BT32-1 0 trench was not addressed by geophysical survey/target removal. As a result, additional work was required to address the ground surface surrounding the trench. This additional work was incorporated into the Munitions Testing remedy (TtEC 2005b).

2.3.8 BA 9a, Parcel 2 BA 9a, Parcel 2 is a 15.72-acre site located in the southeast comer of Section 25 on RMA, just east of the North Plants Haul Road and north of 8th Avenue (Figure 1.0-2). BA 9a, Parcel 2 was not identified in the ROD as a potential munitions response site or remediation area. Subsequent to the ROD, this area was classified as a Priority I (PI) soil area and was identified for remediation to mitigate potential risk to biota. As indicated on Figure 1.0-2, a portion of BA 9a, Parcel 2 lies within the footprint of the revised CSA-2c boundary. As a result, pre-remedy RMA operations conducted in this area may have impacted portions of the borrow area. In addition, construction of the North Plants Haul Road traversed through BA 9a. The PI soil along the haul road route was removed prior to haul road construction and was stockpiled within Parcel 2.


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2.3.9 DREZ The DREZ is the 2,500-foot exclusion zone which surrounds the RMA Demolition Range (ESA4b). The DREZ was designated as a single munitions response site due to the potential impact of explosive demolition events held on the RMA Demolition Range (pre-Remedy and Remedy Support). For this reason the history of the RMA Demolition Range directly impacts a portion of the history of the DREZ. The history of the RMA Demolition Range is provided in Section 2.3.4 of this document. In summary, the RMA Demolition Range was historically used for the demolition and disposal of rocket motors, rocket propellants, miscellaneous explosives, and incendiary devices such as 500-pound M76 bombs. In addition, the range was used during RMA remediation to dispose of more than 9,000 MEC recovered from various RMA locations. These demolition and disposal activities resulted in the potential for MEC in the DREZ from kickout. The DDESB-approved Site Safety Submission for use of the RMA Demolition Range during remediation established the DREZ at 2,500 feet based on the selection of a 4.2-inch mortar as the munition with the greatest fragmentation distance (DDESB 1999).

2.4 Summary of the Selected On-Post Remedy The overall remedy required by the 1996 ROD for the On-Post OU includes the following:

• Interception and treatment of contaminated groundwater at the three existing on-site treatment plants

• Construction of a new Resource Conservation and Recovery Act (RCRA)- and Toxic Substances Control Act-compliant HWL on-post

• Demolition of structures with no designated future use and disposal of the debris in either the new, on-post HWL or the Basin A consolidation area, depending upon the degree of contamination

• The contaminated soil at RMA is addressed primarily through containment in the on-post HWL or under caps/covers, or through treatment depending upon the type and degree of contamination. Areas that have caps or covers require long-term maintenance and will be retained by the Army. These areas will not become part of the wildlife refuge.

• The Basin A disposal area is used for consolidation of biota risk soil and structural debris from other RMA contamination areas and is covered with a soil cover including a biota barrier.

2.5 Summary of the Selected Remedy for Munitions Testing Soil The ROD identifies the following major remedial actions for the Munitions Testing Project:

• Locate UXO using geophysical survey. Excavate and transport off post for detonation or other demilitarization process. Detonate on post if the UXO is unstable.

• Excavate munitions debris and associated soil in excess of TCLP and dispose in the onsite hazardous waste landfill.

• Revegetate all disturbed areas.


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2.6 Munitions Testing Remedy Implementation

The remedial design for the Munitions Testing Project was combined with the Burial Trenches project and was completed in 1999 (FWENC 1999a). The Munitions Testing remedy was implemented in four parts over an eight-year period. The initial project effort, Part I, completed the ROD-identified remediation requirements. Subsequent project efforts were added as new information was developed that resulted in additional remediation requirements. The [mal part of the project, remediation and closure of the RMA Demolition Range (ESA-4b), was delayed to allow for continued use of the range to support MEC demolition requirements for the remainder of the remedy projects. A summary of the Munitions Testing Project implementation is provided in Table 2.6-1.

Table 2.6-1: Munitions Testing Project Implementation

M~nitions Testing Project Part

Remediation Area

Start Date Finish Date Constr~ction Completion Report (CCR) Reference

Part I CSA-2c ESA-Ia ESA·lb ESA-lc ESA-Id ESA-4b MT29·1

April 13,2000 November 8, 2000 and

September 9, 2003'

March 26, 2004 (TtFW 2004c)

Part II ESA-4a BAIO

BT32-IO

May 1,2002 April 17, 2007 February 5, 2008 (TtEC 2008e)

Part IIJ DREZ' BA9a, Parcel 2

CSA-2c SWfNW

June 29,2005 February 6, 2007 March 10, 2008 (TtEC 200Bd)

Part IV ESA-4b' May 1,2007 March 25, 2008 August 18, 2008 (TtEC 2008a)

'The initial scope of work for CSA-2c was completed in November 2000. Additional scope, including biota soil removal and ACM removal, was completed in 2003.

'Engineering controls were implemented prior to DREZ remediation, to contain kickout.

'ROD-identified soil and munitions debris removal were completed in November 2000 under Part I; however, use of the RMA Demolition Range continued to support remediation activities. Additional remediation to complete range closure was completed under Part IV in March 2008.

3.0 BASIS FOR THE ESD For the Munitions Testing Project, there were several significant changes identified during remedial design and implementation compared to the remedy description in the ROD. These changes, discussed in the following sections, include decrease in soil volume associated with munitions debris based on TCLP testing, boundary changes for surface burn areas and resultant soil volume increase, additional scope for CSA-2c, expansion of ESA-4a remediation area, the addition of several munitions response areas, additional scope for ESA-4b, and overall project cost increase.


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Rock)' Mountain Amnal Explanation of Significant Differences Munitions (Testing) Soil Remediation Revision 0 WBS 2.03.12.02 November 3,2008

3.1 Soil Volume Decrease due to TCLP Sampling For the Munitions Testing Project, the ROD requires "Removal and landfill of munitions debris and nearby soil in excess of TCLP." During design, existing data and site conditions were reviewed to determine the amount of soil exceeding the TCLP criteria. Soil sampling was conducted in Munitions Testing sites during the RI and although the total metal sample analysis from the RI suggested an exceedance ofTCLP criteria was unlikely, TCLP analysis was not performed. As a result, the ROD provided conservative estimates of soil volumes based on potential TCLP exceedances for the selected remedy as described below.

The ROD volumes for munitions debris and associated soil are based on the entire site areas designated as potential debris areas. The volumes were then calculated by multiplying the potential debris areas by 1 ft (depth). Volume calculations are presented in the Soil Quantity Calculation Summary Report (SQCSR) (FWENC 1996a). The ROD indicates that the resulting volumes are considered the "maximum potential debris volume." For most of the Munitions Testing sites, visual inspection of the site confirmed that munitions debris, slag and charred soil were evident over the entire site area. However, at sites ESA-4a and CSA-2c the actual occurrence of debris was relatively sparse. Therefore, determination of the actual soil exceeding TCLP criteria was warranted during the design to revise the maximum potential volume presented in the ROD. A sampling program was developed to assess the levels of metals in soil and the results were used to determine whether, and to what extent, soil should be excavated along with the metal debris.

Sample locations for the TCLP sampling program were selected based upon the presence of munitions debris. Because the soil directly beneath the metallic munitions debris has the highest probability of exceeding TCLP regulatory levels, this soil was targeted for sample collection and analysis. This biased sampling approach was selected to produce results that would indicate the worst-case scenario of affected soil volumes. A Schonstedt magnetic locator was used to locate pieces of metallic debris within the site boundaries. Twenty locations were identified for sampling. Samples collected in ESA-4a were considered representative for both ESA-4a and CSA-2c since site conditions were similar.

Sampling was conducted during the summer of 1998. The metallic debris was set aside to allow access to the underlying soil. Soil samples were collected from two depths at 20 locations. The first sample was obtained from soil in the range of 0- to 3-inches directly below each metal debris item. About one foot of soil was then removed and another sample was taken from a depth of 12- to IS-inches below the metal debris. This second sample was reserved and would only be analyzed if the shallow sample exceeded the criteria. These additional samples were intended to provide an indication of the depth of contamination if the surficial samples exceeded the TCLP criteria.

All 20 soil samples were delivered to the RMA Environmental Analytical Laboratory for total waste analysis for TCLP-listed metals (arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver). The results of the TCLP sampling program are described in the ESA-4a: Munitions Impact Area Sampling and Analysis Results (FWENC 1998). The RCRA "20 times rule" was applied to the analytical data and the results were compared to the TCLP regulatory


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action levels. Because the TCLP method uses a sample dilution of 20 (100 grams of soil in 2000 ml of extraction fluid), sample concentrations can be divided by 20 to determine the maximum theoretical leachate concentration. If the maximum theoretical leachate concentration is less than the TCLP regulatory limit the sample cannot fail TCLP even if all the analyte were to be recovered during the extraction procedure. Table 3.1-1 presents the total metals analysis results, the TCLP criteria and the 20 times evaluation.

In order to provide an additional quality check, two samples (split from the 0- to 3-inch samples) were sent to an off-site lab for TCLP analysis. The two samples were selected because they had the highest metal concentrations (particularly lead and chromium) from the total waste analysis. The TCLP analysis confmned that all TCLP-listed metals were below the regulatory limits. In fact, the results were below the reporting limits for all metals except barium, indicating very little leachable metal in the ESA-4a soils. In addition, the TCLP analysis confmned the appropriate use of the "20 times rule" for the total analysis. Complete results of the TCLP sampling program are described in the ESA-4a: Munitions Impact Area Sampling and Analysis Results Report (FWENC 1998).

Table 3.1-1: Sample Results and Comparison to TCLP Limits

Analyte Number of Detections

Maximum Detection (mg/kg)

Maximum Leachate

Concentration (mglL)'

TCLP Regulatory

Limit (mglL)

Percent of 20 times

TCLPLimit (%)

Arsenic 20 5.82 0.29 5.0 5.8

Barium 20 163 8.15 100.0 8.2

Cadmium 1 0.498 0.025 1.0 2.5

Chromium 20 16.5 0.825 5.0 16.5

Lead 20 31 1.55 5.0 31.0

Mercmy 1 0.167 0.008 0.2 4.2

Selenium 0 NA NA 5.0 NA

Silver 0 NA NA 5.0 NA

'Maximum theoretical leachate concentration aSsumes 100 percent of the analyte is recovered in the leachate and is derived by dividing the maximum analyte concentration by 20, reflecting the 20 to I weight ratio of extraction fluid to solid used in the TCLP test method.

Results of the analysis show that none of the soil associated with the munitions debris have concentrations of metals exceeding the TCLP regulatory levels. Also, concentrations ofRMA COCs were below the ROD-identified HH SEC. In addition, total metal concentrations from the existing RI data (16 samples) were reviewed and compared to TCLP criteria using the "20 times rule." There were no exceedances of the TCLP regulatory limits. Based on the sample results, excavation in sites ESA-4a and CSA-2c was limited to debris removal and soil excavation was eliminated (FWENC 1999a). These changes resulted in a volume decrease of 69,468 bank cubic yards (bey). All debris was removed and disposed at the HWL, as required.


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3.2 Soil Volume Increase due to Boundary Modifications As discussed above, the ROD requires "removal and landfill of munitions debris and nearby soil in excess ofTCLP." For most of the Munitions Testing sites, visual inspection of the site confirmed that munitions debris, slag and charred soil were evident over the entire site area. As a result, the TCLP criteria was not applied due to the visual impact the burn area had on the soil, and the entire site was excavated to the extent of the debris and charred material.

The ROD and SQCSR present site boundaries for the Munitions Testing sites and requires the excavation of munitions debris and associated soil to a depth of one foot (FWENC 1996a). During design, Sanford Cohen and Associates (SC&A) conducted a magnetic geophysical survey that included all of the Munitions Testing Project area (SC&A 1998). The results of the geophysical survey were used to identify possible areas of metallic debris within or adjacent to the ROD site boundaries. A field reconnaissance was then performed to validate the geophysical survey results and determine the extent of debris at the sites. Based on these observations, site boundaries for ESA-Ia, ESA-Ib, ESA-Ic, and ESA-1d were enlarged to encompass the entire debris area (FWENC I999a). In addition, an area of debris was identified northeast ofESA-lc and was added to the project as site MT29-1. Although this area was identified during the Rl and excluded from remedy in the ROD, the design included the site based on the presence of munitions debris similar to the other sites being remediated.

Site boundaries at one site, ESA-4b Demolition Area, were decreased using historical site information and the 1998 geophysical survey data to limit the area to the top of the perimeter berm surrounding the demolition area. The revised boundary more accurately encompassed the area of historical activity and extent offerrous anomalies present at the site. The boundary modification at this site resulted in a volume decrease compared to the ROD.

Exploratory excavation was also performed during design to verify the ROD-defined excavation depths for the Munitions Testing sites. Observations made during the exploratory excavations indicated the presence of debris, slag and charred soil to a maximum depth of 9 to 10 inches. Based on these observations, the ROD-defined excavation depth of I foot was retained.

In addition, the design specified that the debris and soil excavation in these sites be continued beyond.the design boundaries if necessary to ensure removal of all munitions debris and charred soil. In some areas, excavation continued beyond the design depth to allow complete removal of all visible debris. Debris removal continued beyond the design boundaries for all six sites. Following excavation, the site was inspected for evidence of remaining debris, ripped to a depth of 18 inches and inspected again for debris. Any additional debris found during inspection was removed and disposed in the HWL.

Final remediation volumes were calculated based on pre- and post-excavation surveys of the sites. Changes in the site areas, excavation depths and visual debris removal resulted in increased remediation volumes for five sites and a decrease in remediation volume for one site. Overall, the remediation boundary changes for these six sites resulted in a volume increase of 15,137 cubic yards above the ROD volume.


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Rocky Mountain Menal Explanation of Significant Differences Munitions (Testing) Soil Remediation Revision 0 WBS 2.03.12.02 November 3, 2008

3.3 Debris Removal from CSA-2c The ROD identified CSA-2c as both a potential UXO/munitions debris area and a potential biota risk soil area. As discussed in Section 3.1, soil analysis completed during remedial design indicated that soil associated with munitions debris did not exceed TCLP criteria. Therefore, soil excavation for purposes of removing munitions debris associated with soil was eliminated. Also during design, SC&A conducted magnetic geophysical surveys over portions ofSections 25 and 36 including CSA-2c (SC&A 1998). Results of the geophysical survey were used to identify locations of potential subsurface MEC. Based on the geophysical results, 14 anomalies were identified within the ROD site boundary. During anomaly characterization, two characterization points located in the western CSA-2c area were found to contain ACM mixed within the soil. As a result, the project scope was modified to include ACM removal (FWENC 2000a). Approximately 105 bcy ofACM was removed during August 2000 (TtFW 2004c).

Subsequently, in 2003, biota risk soil was excavated from CSA-2c in accordance with the ROD. During biota risk soil excavation, the subcontractor encountered construction debris in the eastern CSA-2c area, which contained both friable and non-friable ACM. The project scope was again modified to incorporate removal ofACM and construction debris based on visual observation of debris (FWENC 2003b). Approximately 613 additional bey ofACM and debris were removed and disposed at the HWL (TtFW 2004c).

3.4 ESA-4a Boundary Modifications The remedy identified in the ROD for ESA-4a included locating MEC using geophysical survey with subsequent removal and destruction, as well as excavation of munitions debris and associated soil in excess of TCLP. As discussed in Section 3.1, excavation of soil was eliminated based on sampling completed during design that demonstrated the concentrations of contaminants in soil did not exceed TCLP criteria. Removal of MEC and munitions debris remained as remedy requirements for ESA-4a.

As discussed in Section 2.3.3, the ROD identified a 42-acre area for ESA-4a remediation. During remedial design, a magnetic survey was performed by SC&A over much of the northeast quadrant ofRMA including ESA-4a (SC&A 1998). Results of the geophysical survey were used to identify apparent subsurface anomalies that have the geophysical signature of potential MEC. Anomaly characterization was performed by Ordrem International in the summer of 1999 and was conducted in two phases. The Phase I characterization was performed to evaluate the accuracy of the geophysical survey and to gain additional information on the occurrence and distribution of MEC. Characterization was biased toward targets with confidence ranking of? or above (thought most likely to be an item of concern) throughout the eastern portion ofRMA, including 5 targets located in ESA-4a. The Phase II effort included location, excavation and characterization of 161 targets in ESA-4a. Seventy-four of the targets were characterized as munitions debris and two targets were MEC. The remaining targets were characterized as miscellaneous debris or geologic anomalies (FWENC 1999b). Based on the anomaly characterization efforts, the design indicated that remedy requirements to remove MEC and munitions debris in ESA-4a were complete.


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In late 2001, the RMA Surrunary and Evaluation Team (SET) discovered a draftsman's sketch (circa 1945) indicating the mortar impact area may have extended beyond the previously investigated ROD site limits (HESS 2002). In January of2002, the SET recommended expanding the remediation area. Site ESA-4a was subsequently expanded to the limits shown in the 1945 sketch by extending 303 acres to the southeast and 7 acres to the west (FWENC 2002e). Anomaly characterization was completed for 35 targets located in the expanded area. Of these, three targets were 4.2 inch smoke mortars that were characterized as UXO and 17 targets were classified as munitions debris. While characterizing these targets, 14 additional targets were discovered within the original ROD boundary that had not been investigated by Ordrem International. Eight of these targets were fence posts; the remaining six were identified as targets and characterized. One of the six targets resulted in the clearance of three 4.2-inch highexplosive (HE) mortars. The mortars had apparently been through an unsuccessful explosive countercharge procedure. One round was empty (munitions debris), one was full of HE (MEC) and the other was half full of HE (MEC). The remaining five targets were either geology related or munitions debris.

Due to concerns that additional MEC may exist in areas outside the 42-acre ROD boundary and the additional 1003 acres, the boundary of ESA-4a was again expanded to include most of Site 30-1 resulting in a revised area of approximately 212 acres (FWENC 2002d). Revision of the Munitions Testing remedy to the expanded ESA-4a boundary also included a requirement to complete a new geophysical survey over the entire expanded site boundary followed by target clearance and a subsequent quality assurance (QA) geophysical survey over the same area with additional target clearance (FWENC 2002b).

Prior to conducting the geophysical survey, a surface sweep was completed to remove visible metallic debris from the survey area. Following the surface sweep, the initial geophysical survey was completed in the fall of2002. Target characterization activities began in 2003 and, following an iterative process that led to an accepted munitions response action, were completed in November 2005. A detailed description of the project activities chronology is provided in the ESA-4a Munitions Response Report (TtEC 2006a). Due to the number ofMEC recovered in close proximity to the southeast comer ofESA-4a, the site boundary was expanded to the southeast an additional 12.4 acres (TtFW 2004d). A complete discussion of the project boundary modifications is included in the Munitions Testing Part II CCR (TtEC 200ge). The geophysical survey and target clearance process developed for ESA-4a was applied to the expanded area, bringing the total ESA-4a remediation area to 224.4 acres. A description of the clearance activities performed and MEC recovered is presented in the ESA-4a Munitions Response Report (TtEC 2006a).

During the initial target characterization, II areas were identified as potential demolition! burn/burial pits. Because of the density of metallic debris in these areas, individual tai"gets could not be identified from the geophysical data. A "mag and dig" process, using magnetometers and electromagnetic detectors, was used to identify anomalies for removal. with hand tools. A description of the characterization of the demolition! burn/burial pits is presented in the Munitions (Jesting) Site ESA-4a Demolition/Burn/Burial Pit Report (TtEC 2006b).


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Roc""')' Mountain Arsenal Explanation of Significant Differences Munitions (resting) Soil Remediation Revision 0 was 2.03.12.02 November 3. 2008

Two other large anomalous areas were identified based on the initial geophysical data where individual target selection would be ineffective for clearance. These areas, the Rosenzwieg Homestead and the RMA Demil Facility, were cleared using magnetometers and electromagnetic detectors to screen the soil and identify debris. Although some munitions debris was identified in these areas, no MEC was recovered.

Following initial target characterization and clearance of the demolitionlburn/burial pits, Rosenzwieg Homestead and Demil Facility, a QA geophysical survey was conducted over the entire ESA-4a area. A final surface sweep was also conducted following seedbed preparation of the area. The surface sweep consisted of a visual sweep of the area to remove any remaining debris.

A complete description of the MEC recovered during ESA-4a characterization and remediation is presented in the ESA.-4a Munitions Response Report (TtEC 2007c). All MEC recovered were considered unsafe for off-site transportation and were disposed on site per RMA Standard Operating Procedure for MEC Disposal by Detonation (TtEC 2007f). Munitions debris was disposed at the on-site HWL or Enhanced Hazardous Waste Landfill (ELF). Approximately 52 bcy of munitions debris was disposed at the HWL (TtEC 2008e).

3.5 Additional MEC Remediation Areas During implementation, the following five additional areas were identified with the potential for MEC. These areas were added to the Munitions Testing Project and remedial activities were identified to satisfy remediation requirements identified in the ROD for Munitions Testing sites. A description of the rationale for addition to the Munitions Testing Project and summary of remediation activities is provided for each area.

3.5.1 BA 10 Surface Burn Area

BA 10 was identified as a source of borrow soil for use as backfill, gradefill and cover soil for various RMA remediation projects. During characterization of soils in BA 10, munitions debris resulting from an E-139 bomblet was discovered. Subsequent inspection of the area resulted in identification of a 200-foot by 200-foot surface bum area for remediation (FWENC 2003a). A visual surface sweep was conducted, aided by handheld magnetometers, to identify and remove MEC and surface debris. No munitions debris or MEC were recovered. Approximately 57 pounds of trash and debris were removed. Following debris removal, visually impacted bumt soil was removed and disposed at the HWL (TtEC 2008e).

3.5.2 BT32-10

Remediation of the BT32-1 0 trench was completed under the Burial Trenches Project in 2000 (FWENC 2002a). During the Burial Trenches remediation, two MEC were recovered from the BT32-10 area. Unlike other trenches in the Burial Trenches Project, the surface area surrounding the BT32-1 0 trench was not addressed by geophysical survey/target removal. Therefore, the area surrounding the trench was incorporated into the Munitions Testing remedy (TtEC 2005b).

An initial geophysical survey was conducted in October 2005 over approximately three acres surrounding the trench; however, the results of the initial survey indicated that the anomalies


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Rocky Mountain Arsenal Explanation of Significant Differences Munitions [resting) Soil Remediation Revision 0 WBS 2.03.12.02 November 3, 2008

were too dense to pennit effective target selection. Due to the high density of anomalies, the first anomaly clearance effort was modified to use the standard "mag and dig" process using an electromagnetic detector to identify and remove debris (TtEC 2005a). During the "mag and dig" operations, a total of 2,260 pounds of munitions debris and miscellaneous debris was removed. No MEC were recovered during this operation. In November 2005, a second geophysical survey was completed. All targets identified from the geophysical survey were cleared and no MEC were recovered (TtEC 2007d). All munitions and miscellaneous debris recovered during intrusive operations were disposed at the HWL (TtEC 2008e).

3.5.3 CSA-2c

As discussed in Section 3.3, anomaly characterization and debris removal was performed over the ROD-ide.ntified CSA-2c area in 1999. During the SET review of Sections 25 and 36, aerial photography showing the extent of the M47 munitions testing area was overlaid with the geophysical data from the 1998 SC&A survey. Based on the historic use as a test site and the presence of geophysical anomalies within the historic test area, the entire test area, approximately 18.7 acres, was identified for characterization of all geophysical anomalies to minimize the potential for future MEC hazards (HESS 2002). This additional anomaly characterization was performed during February of2002 (FWENC 2002c, 2002f).

The concern for potential MEC hazards in CSA-2c was renewed in 2005 after discovery of several burster tubes in BA 9a, Parcel 2, which overlaps the expanded CSA-2c area. Review of site history indicated that MEC and munitions debris could be present on the surface due to kickout resulting from test pad operations. The area of concern was identified within the

. firebreak visible in 1940s aerial photographs. Recent remedy efforts were also considered in determining the extent of the areas which needed additional characterization. The northeast and southeast portions of CSA-2c overlap BA 9a, Parcels 3 and 4. Because these areas had been identified as PI soil areas and I foot of soil had been removed during a separate remedy effort, additional characterization was considered unnecessary. The northwest (NW) and southwest (SW) portions ofCSA-2c overlap a residual ecological risk soil area labeled 36NE-3. Because soil removal had not been performed in these areas, CSA-2c NW and SW were identified for additional characterization.

In November 2005, site characterization was performed for CSA-2c SW to assess the potential for additional MEC and determine additional remediation requirements. A visual surface sweep, assisted by magnetometer and electromagnetic detector, was conducted to identify anomalies. Approximately every third anomaly identified using the hand-held detectors was excavated and characterized. The site characterization resulted in the recovery of one MEC item, a burster tube from a 4.2-inch mortar. Additionally, approximately 1, I00 lbs of munitions debris, primarily from the M47 Incendiary Bomb, were recovered during the site characterization (TtEC 2006c).

Based on the results of the characterization, munitions response for CSA-2c SWINW was added to the Munitions Testing Project remedy requirements (TtEC 2006d). The additional munitions response actions included a geophysical survey over the CSA-2c SWfNW area and characterization of targets identified based on the survey data. Although the site was characterized past the firebreak to the expanded CSA-2c boundary, the boundaries of CSA-2c


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SWfNW for munitions response were limited to the ftrebreak based on the location of the recovered MEC and the lessening amount of munitions debris recovered near the firebreak. The resulting area for geophysical survey and anomaly clearance was approximately 4.8 acres for CSA-2c SWfNW (TtEC 2007b). Disposal of munitions debris from CSA-2c SWfNW was combined with BA 9a, Parcel 2 as discussed in Section 3.5.4.

3.5.4 BA 9a, Parcel 2

In August 2005, activities began to remove P I soil from BA 9a, Parcel 2 for use as gradefill in Basin A. This activity was stopped due to the unearthing of 10 sections of explosive-filled (tetryl pellets) M4 Bursters for the M47 Incendiary Bomb. All intrusive operations in the borrow area were suspended until an investigation into the potential to recover additional MEC could be completed. In August of 2005, the PMC performed a site characterization of BA 9a, Parcel 2 consisting of a visual surface sweep assisted by magnetometer and electromagnetic detector (TtEC 2006c). Approximately every third anomaly was excavated and characterized to determine the potential for MEC recovery in BA 9a, Parcel 2. Three MEC were recovered during the site characterization, which subsequently led to the inclusion of BA 9a, Parcel 2 into the Munitions Testing Project (TtEC 2006d).

Remediation of BA 9a, Parcel 2 consisted of target characterization using the "mag and dig" process to detect subsurface anomalies. The entire area was swept using a hand-held magnetometer and/or electromagnetic detector. All anomalies detected were immediately characterized. In addition to the surface ofthe borrow area, the "mag and dig" process was applied to the P I soil stockpile present within Parcel 2. Once the stockpile was cleared to a depth of 18 inches, a six-inch to one-foot lift was removed. This process was repeated until the entire stockpile was cleared and removed to grade. A final sweep was then conducted over the stockpile footprint (TtEC 2007b).

As a result of BA 9a, Parcel 2 and CSA-2c SWfNW munitions response efforts, approximately 10,000 Ibs of munitions debris were recovered and disposed in the HWL (TtEC 2008d). All MEC recovered during the BA 9a, Parcel 2 and CSA-2c SWfNW munitions response efforts were not considered safe for off-site transportation and were disposed on site per RMA Standard Operating Procedure for MEC Disposal by Detonation (TtEC 2007£).

3.5.5 DREZ As discussed in Section 2.3.9, the DDESB-approved Site Safety Submission for use of the RMA Demolition Range during remediation established an exclusion zone (EZ) surrounding the Demolition Range at 2,500 feet (DDESB 1999). However, the DREZ was not identified in the ROD as a munitions response site. During the execution of the Munitions Testing Project it was determined that pre- and post-remedy RMA explosives disposal operations may have affected the DREZ and therefore additional consideration regarding the potential to recover MEC during future use of the area was necessary.

In an effort to prepare for the eventual closure of the RMA Demolition Range, past and present explosives demolition events were considered and it was determined that site characterization of the DREZ would need to be included within the scope of Munitions Testing Project. This site


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characterization was intended to assess the level of MEC (i.e., kickout) within the DREZ and develop a path forward that would assist future closure of the RMA Demolition Range. Site characterization was conducted over 18.4 acres of the DREZ and consisted of a magnetometerassisted surface sweep followed by geophysical survey and target characterization (TtEC 2005c). A total of 66 MEC and approximately 2,500 pounds of munitions debris were recovered during the DREZ characterization (TtEC 2006g). The characterization results indicated a potential to rec9ver MEC within the boundaries of the DREZ and that clearance of the DREZ was warranted.

Once the characterization of the DREZ began in July of2005, the PMC started employing engineering controls per Use ofSandbags for Mitigation ofFragmentation and Blast Effects Due to Intentional Detonation ofMunitions (USACE 1998) during all explosive disposal operations performed on the RMA Demolition Range. This effort essentially contained potential kickout during RMA explosive disposal events and minimized the likelihood of introducing additional MEC to the DREZ.

Based on the results of the DREZ characterization, remediation activities were implemented for the DREZ consisting of a magnetometer-assisted surface sweep, initial geophysical survey with target characterization, and a QA geophysical survey with target characterization. The southwest section of the DREZ was excluded since the area had been previously addressed under the ESA4a munitions response efforts (TtEC 2008e) and Burial Trenches remediation ofBT30-1 (TtFW 2004a). The resulting DREZ remediation area is approximately 432 acres.

Prior to conducting the geophysical survey, a surface sweep was completed to remove visible metallic debris from the survey area. Following the surface sweep, the initial geophysical survey was completed and targets were identified for characterization. Following initial target characterization, a QA geophysical survey was conducted over a portion of the DREZ. Based on the location ofMEC recovered from the initial geophysical survey, the QA survey was focused on the area closest to the Demolition Range. An area surrounding trench BT29-2 was also included based on the recovery ofMEC in that area. The total QA geophysical survey area was approximately 114 acres (TtEC 2006g).

A complete description of the MEC recovered during DREZ characterization and remediation is presented in the DREZ Munitions Response Report (TtEC 2007c). All MEC recovered were considered unsafe for off-site transportation and were disposed on site per RMA Standard Operating Procedure for MEC Disposal by Detonation (TtEC 2007f). Approximately 31,500 pounds of munitions debris was recovered and disposed at the HWL during DREZ munitions response efforts (TtEC 2008d).

3.6 Additional Scope for ESA-4b The ROD identified ESA-4b, the Demolition Range, for remediation as part of the Munitions Testing Project. Remedy requirements included screening for munitions and removal of one foot of munitions debris and associated soil. During the summer of2000, ESA-4b was remediated in accordance with the ROD and the Burial Trenches/Munitions Testing 100 Percent Design Package (FWENC 1999a). This effort consisted of a surface inspection for MEC, excavation of munitions debris and associated soil including the earthen berms surrounding the site and one


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foot of soil from the site surface, and inspection of the surface following excavation. Site boundaries were modified during design as discussed in Section 3.2.

In addition, to support the overall RMA remediation effort, ESA-4b was formally reactivated to function as the explosive disposal area for MEC recovered during the remainder of the RMA remedy (DDESB 1999). As a result, final remediation of the site was delayed until explosive disposal operations were completed (FWENC 2003c). During remedy support operations, the RMA Demolition Range facilitated the disposal of more than 9,000 MEC recoverecj from various RMA locations. Explosive disposal operations were concluded at the RMA Demolition Range in the spring of 2007.

As discussed earlier, the DDESB-approved Site Safety Submission also established a 2,500 foot EZ surrounding the Demolition Range. During the DREZ munitions response effort, the EZ required to continue RMA Demolition Range operations was reduced from 2,500 feet to 200 feet. This reduction was possible because of the implementation of DDESB-approved Engineering Controls (USACE 1998) and the relocation of the disposal pit to a 10-foot by 10foot disposal area in the center of the RMA Demolition Range. The new EZ for explosives disposal events conducted on the RMA Demolition Range extended 200 feet from the IO-foot by IO-foot disposal area; however, the 200-foot EZ did not extend beyond the boundary of the 4.5acre RMA Demolition Range.

Remediation activities for range closure began in May 2007 and consisted of a surface sweep, initial geophysical survey with target characterization, mag and dig operations for areas of high anomaly density, and a QA geophysical survey with target characterization (TtEC 2007e). For range closure activities, the site boundary was revised to match the boundary of the surrounding DREZ (TtEC 2006£). Prior to the geophysical survey, a surface sweep was conducted to remove surface debris and reduce the number of anomalies. The initial geophysical survey was also completed in May 2007 (TtEC 2008c).

The initial geophysical survey of the Demolition Range identified a dense anomalous area in the western portion of the site where the original demolition pits were located. Due to the anomaly density in this area, the mag/dig technique was used to detect subsurface anomalies. The area was swept with a hand-held magnetometer and/or electromagnetic detector and all anomalies detected were characterized immediately. The QA survey was completed in September 2007. All MEC recovered were disposed at the Demolition Range (TtEC 2008c). In addition, approximately 7,000 pounds ofmunitions debris was removed and disposed at the ELF (TtEC 2008a).

During initial target clearance operations, some targets were identified that possessed characteristics of demolition or burn sites. These areas were excavated and identified for soil sampling to determine whether the soil was contaminated as a result of demolition activities. Soil samples were collected from all 14 excavation pits and 10 of the soil stockpiles generated during the excavations. Results indicated that the soil contained elevated levels of mercury exceeding the biota risk criteria. In addition, three samples exceeded 20 times the TCLP regulatory criteria for RCRA Hazardous Waste (TtEC 2008b). Expanded sampling was conducted to further


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delineate the extent of biota risk soil, including composite surface samples collected over the entire Demolition Range. Based on the results of the sampling, remediation of biota risk soil was added to the project scope (TtEC 2007a). Approximately 6,600 bcy of biota risk soil was removed and disposed at Basin A. An additional 175 bcy of soil with concentrations indicating potential characteristic hazardous waste were disposed in the ELF. All stockpiled soil was also disposed in the ELF, primarily because of the potential for the stockpiled soil to contain munitions debris (TtEC 2008a).

3.7 Basis for Cost Change Project implementation costs have increased significantly compared to the 1996 ROD estimate as a result of additional project scope. Initial remediation costs decreased primarily due to elimination of soil excavation, based on TCLP sampling, for ESA-4a. However, additional project scope far outweighed the savings from the initial remediation. As described in the preceding sections, scope additions to the Munitions Testing Project include the addition of ACM removal from CSA-2c, boundary modifications for the surface burn areas, addition of MT29-1, expansion of ESA-4a remediation area, requirement for an expanded geophysical survey over the ESA-4a area, the addition of five new remediation areas (BA 10, BT32-1 0, BA 9a Parcel 2, CSA-2c SWfNW, and the DREZ) requiring geophysical survey and target clearance, and added remediation requirements to ESA-4b.

During Part I, all ROD requirements were completed except for the geophysical survey and MEC clearance for ESA-4a. Elimination of soil excavation from ESA-4a, which comprised 77 percent ofthe total ROD project volume, resulted in significant cost savings. However, this savings was somewhat offset by remediation volume increases for the surface burn areas (ESAIa, ESA-Ib, ESA-Ic and ESA-Id) and the addition ofMT29-1. The savings for the RODidentified excavation requirements is estimated at $521,000. Removal of ACM and construction debris from CSA-2c was also completed under Part I and contributed approximately $218,000 in additional cost. Overall, Part I of the project was completed at a savings of approximately $303,000 from the ROD estimate.

During Part II, geophysical survey and MEC clearance was completed for ESA-4a. Although a geophysical survey and site characterization were completed prior to the Munitions Testing design, concerns over the possibility of MEC existing in areas outside the ROD boundary resulted in expansion of the remediation boundaries and requirement for an expanded geophysical survey and target clearance. This increased scope resulted in a significant cost increase for the project. The BA 10 Surface Burn Area and BT32-1 0 surface remediation were also completed under Part II. Although costs for these areas were not tracked separately from the overall Part II cost, the two additional remediation areas contributed to the cost increase. Overall, the cost for completing Part II of the project was approximately $2.2 million higher than the ROD estimate.

Remediation activities completed under Part III and Part IV of the project were not identified in the ROD and represent scope additions for the Munitions Testing Project. Under Part III, geophysical survey and target clearance of the DREZ contributed approximately $1.5 million in additional cost. Remediation ofBA 9a Parcel 2 and CSA-2c SWfNW added another $332,000.

MWlitions Testing £SO.doc

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Remediation ofESA-4b, under Part IV, resulted in an additional $460,000 for MEC clearance and debris removal, and $103,000 for biota soil excavation.

Overall, project costs increased from a ROD-estimated $2.75 million to approximately $7.03 million. Table 3.7-1 provides a summary of project costs corresponding to each of the four implementation parts of the project.

Table 3.7-1: Summary of Costs for Munitions (Testing) Soil Remediation

Munitions Testing Project Part

Remediation Area ROD Estimated Cost

Actual Cost Difference

Part I CSA-2c, ESA-1a, ESA-1b, ESA-1c, ESA-1d, ESA-4b,

MT29-1 _._ ....... _......._---CSA-2c BiotalACM

$1,885,087

----- -_. ---- -- -- ---$14,545

$1,364,312

--- - -- --- -_ .... -$232,055

-$520,775

--_. ---- --- -- --_.... $217,510

Part II ESA-4a BA 10

BT32-10

$853,864 NA NA

$3,026,2261 $2,172,362

Part III DREZ BA 9A, Parcel 2 CSA-2c SWfNW

NA NA

$1,516,740 $332,438'

$1,516,740 $332,438

Part IV ESA-4bMEC ESA-4b Biota

NA NA

$459,717 $103,090

$562,807

Total $2,753,496 $7,034,578 $4,281,082

ICost for remediation of BA 10 and BT32-1 0 were 'incorporated into the remediation cost for ESA-4a.

'Remediation ofBA 9a, Parce12 and CSA-2c SWfNW was a single effort, therefore costs are combined.

4.0 DESCRIPTION OF SIGNIFICANT DIFFERENCES 4.1 Changes to Munitions Testing Project Remediation Several changes to the Munitions Testing Project were identified during remedial design and implementation. During design, soil sampling was conducted in areas without dense debris to demonstrate that concentrations of metals in soil do not exceed the TCLP regulatory criteria. This resulted in a 69,468 bey decrease in soil volume associated with munitions debris. Also during design, remediation boundaries were revised based on the presence of munitions debris, slag and charred soil and one remediation area was added. These boundary changes resulted in an increase in remediation volume of 15,137 bey. Together, the design revisions resulted in a decrease in excavation volume of 54,331 bey, or a 61 percent decrease compared to the ROD estimate. A summary of remediation volume changes is included in Table 4.1-1.

As project implementation proceeded, several changes to the project scope for remediation of MEC were identified. The ESA-4a remediation area was expanded several times based on new information developed during extensive site record reviews and geophysical surveys, resulting in an increase in remediation area from 42 to 224 acres. In addition, five areas were identified with MEC potential that were not included in the ROD. These areas include an expanded area around


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CSA-2c, BA 10 surface burn area, an area surrounding trench BT32-1 0, BA 9a Parcel 2, and the DREZ. The DREZ in particular resulted in a significant scope change, adding 432 acres to the remediation area. Overall, the Munitions Testing Project MEC remediation area expanded from 55 acres to 710 acres, a more than ten-fold increase. A summary of remediation area changes is included in Table 4.1-2. All MEC recovered were considered unsafe for off-site transportation and were disposed on site. Approximately 54,000 pounds of munitions debris was disposed at the HWL or ELF. A summary of munitions debris recovered for each area is included in Table 4.1-1.

4.2 Summary of Cost Change The baseline estimated cost for implementation of the Munitions Testing Project was $2.75

. million based on cost estimates presented in the ROD (FWENC 1996b). The baseline estimate represents original ROD estimated costs reorganized to reflect implementation project descriptions in the Remediation Design and Implementation Schedule (pMRMA 2007). The final cost for implementation of the Munitions Testing Project is estimated at $7.03 million. Some initial cost savings were realized with the elimination of soil excavation, based on TCLP sampling, for ESA-4a. However, these savings were somewhat offset by increased remediation volumes for the remaining ROD-identified areas. Combined, these changes resulted in an initial cost savings of approximately $0.5 million.

The primary contributor to the project cost increase is the remediation effort required to complete geophysical survey and target clearance over the expanded potential MEC areas. The ROD identified approximately 55 acres for the Munitions Testing Project as potential MEC areas; however, expansion of ESA-4a and identification of new remediation areas resulted in over 710 acres for remediation. The expansion of the remediation area for ESA-4a resulted in approximately $2.2 million in additional costs and the addition of the DREZ added approximately $1.5 million. Additional sites BA 9a, Parcel 2 and CSA-2c SWINW contributed another $0.3 million to the project cost. Continued use of the RMA Demolition Range, ESA-4b, to support disposal of MEC recovered during remediation resulted in an additional $0.5 million in remediation costs for range closure. Additional cost growth was realized due to remediation of ACM discovered in CSA-2c, which added approximately $0.2 million, and removal of biota risk soil from ESA-4b, which contributed an additional $0.1 million. Overall, these factors result in a cost increase of approximately $4.3 million above the ROD-estimated cost, or an approximate 155 percent increase.

A review of the range of alternatives evaluated in the ROD for the Munitions Testing Project indicates that the other four site-wide alternatives (not selected) would likely have experienced similar cost change. All site-wide alternatives presented in the ROD included the same remedy selection for the Munitions Testing Project, consisting of geophysical survey for potential MEC areas and excavation ofdebris and associated soil exceeding TCLP criteria. Scope changes and associated cost growth discussed in this ESD would have been encountered under each scenario; therefore, all alternatives would have likely experienced the same cost growth.

5.0 SUPPORT AGENCY COMMENTS The EPA, CDPHE, and TCHD have reviewed this ESD. Comments from these Agencies have been incorporated into the document.


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Table 4.1-1: Changes to Excavation Volumes for Munitions Testing Soil Remediation Sites

ROD-Prescribed Remedy

Modification ROD-Prescribed Remediation Volume (bcy)

Actual Remediation Volume (bcy)

Percent Difference

Remove munitions debris and soil that exceeds TCLP and dispose in the onpost landfill.

Reduction: Volume decrease due to TCLP soil sampling. The TCLP analysis detennined that soil in contact with scarce munitions debris had metal concentrations below TCLP action levels. These soils were left in place and surface metal debris was removed from this area.

Site ESA-4a CSA-2c

Volume' 68,658

863

Site ESA-4a CSA-2c

Volume' 52

1

Enhancement: Volume increases due to horizontal boundary changes. Field inspections of the remediation sites resulted in changes to the remediation areas and volumes; one new site was added.

Site ESA-Ia ESA-Ib ESA-lc ESAcld ESA-4b

Volume' 2,711 2,198 1,814 2,682 9,848

Site ESA-Ia ESA-Ib ESA-Ic ESA-ld ESA-4b MT29·1

Volume' 5,200 4,900 5,365 6,595 9,565 2,765

Total Munitions Debris/Soil Volume Change. All excavated munitions debris and associated soil was disposed in HWL or ELF.

88,774 34,443 - 61 %

Addition: Volume increase due to debris removal from additional remediation areas. These areas were identified during design or implementation as having potential for presence of MEC.

Additional Munitions Debris Volume. All munitions debris was disposed in HWL or ELF.

Site Volume' BAlO 57lbs BT32-10 2,260 Ibs BA9a P2 and CSA-2c 10,0001bs DREZ 31,500 lbs ESA-4b 7,0001bs--_. _. _. -_..-_. _. _.. -- - _. - - -_. _.. _.

SO,8171bs

Excavate biota risk soil from CSA-2c and dispose in Basin A

No Change. Biota risk soil was removed as required from CSA-2c.

Addition: Add biota soil removal from ESA-4b.

Site CSA-2c

Volume 863

Site CSA-2c

ESA-4b

Volume 925

6,775'

Tolal Biola Soil Volume Change 863 7,694 +792%

Addition: ACM and miscellaneous debris were identified and removed from CSA-2c.

CSA-2c 718

IVolumes presented include munitions debris and associated soil. 'Volume represents munitions debris only; no soil removed. 'Munitions debris volume estimated as pounds of debris recovered; no soil removed. 'Approximately 175 bey of potential characteristic hazardous waste soil were disposed in the ELF.


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Table 4.1-2: Changes to MEC Remediation Areas f

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