A1

USEPA�s (OSWER) Draft Guidance forEvaluating the

Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils

An Agency-wide & State Workgroup Product

Overview Presented by:

Henry J. SchuverUS EPA � OSW � Wash. DC

For: EPA-TIO�s Internet Seminar February 11 & 12, 2003

A2

Guidance Workgroup [& contributors]OSWER�s draft-Vapor Intrusion Guidance

Paul Johnson, ASU Todd McAlary, GeoSyn Ian Hers, UBC/Golder

Andrew Fan, R3 David Bennett, OERR Dave Mickunas, EDebbie Newberry, OSWER Diane Groth, NJDEP Dom. Digiulio, ORDCraig Dukes, SC Edgar Ethington, CO Frank Kover, ORDHelen Dawson, R8 Henry Schuver, CAPB Jeff Crum, MIJohn Boyer, NJDEP Jim Weaver, ATH Matt Hale, OSWMatt Straus, OSWER Paul Locke, MADEP Ray Cody, R1Richard Mattick, OUST Ronald Mosley, RTP Sheila Gaston, COStiven Foster, ORD Tom Aalto, R8

Robbie Ettinger, Shell Leslie Hay-Wilson, SageR David Folkes, Env-GrpBlayne Hartman, HP Labs Marcia Bailey, R10 Pat Vanleeuwen, R5A. Guiseppi-Elie, Dupont Elsie Patton, CTDEP Vic Kremsec, BPTom McHugh, API Bill Wertz, NYDEC Craig Mann, EQM

A3

Introduction to Seminar

Purpose � To improve the comments received! 2-Day ORD-sponsored Seminar in Atlanta Feb. 25-26

! Overview of Guidance Framework! Primary Screening ! Secondary Screening (Dr. Helen Dawson)! Site-Specific Screening (Dr. Dom. Digiulio

� Comments Due by Feb. 27, 2003� Comment on what is written in guidance [personal]

A4

IntroductionOSWER�s draft-Vapor Intrusion Guidance (Part I-A)

! One of OSWER�s Primary Objectives� Reduce or control the risks to human health and environment

! Thus, It is necessary to:� Determine if specific exposure pathways exist

! If Pathways exist (are �complete�)+ Determine if they pose a significant risk

A5

Intent?OSWER�s draft-Vapor Intrusion Guidance (Part I-B)

! Tool� For assessing if pathway is �complete� [at a given risk level]

! Originating from site contamination [e.g., subsurface]! Single pathway [single chemical�not cumulative, & not Risk Ass.]

! For screening in (or out)� For further consideration (or not) (i.e., potential)� Not for delineating extent [whole sites/areas not single buildings]� Use changes = reevaluation

! Not regulation� Only guidance � based on current understanding� Not requirements or obligations (e.g., beyond RCRA, CERCLA)

A6

What Sites?OSWER�s draft-Vapor Intrusion Guidance (Part I-C)

! RCRA� Environmental Indicators (EI)

! Current Human Exposures (Under Control)? Determinations� RCRA Facility Investigations (RFI)

! CERCLA� Environmental Indicators (EI)� Remedial Investigations (RI)

! [Remember not risk, not cumulative agents or pathways, MCLs]! Brownfields

� Site Assessments! Not USTs

! Subtitle I (RBCA widely used, & �unique issues�)! [e.g., no bio-degradation (predicted), observed = ok]

A7

Scope?OSWER�s draft-Vapor Intrusion Guidance (Part I-D)

! Incremental Increases (in risks)� (due to subsurface � i.e., from Responsible Party)

! Residential (primary assumption)! Non-Residential too

� Not for �primarily� Occupational & Working ! Employees (w/ chem) �will generally understand �OSHA�* ! Office workers � �will generally understand �OSHA�*! Awareness of Vapor Intrusion? Recommend Notification

� Non-Residential & Not Working! Where general public may be present (schools, hospitals, stores)! Use environmental (public health protection) screening levels! Adjust:: Duration of exposure, Volume of air, Exchange rate

* CERCLA footnote � OSHA stds are not ARARs

A8

Supersedes?OSWER�s draft-Vapor Intrusion Guidance (Part I-E)

! Not - State Guidance(s) � but States my find this useful

! Yes - RCRA (EI Supplemental Vapor) Guidance (10/01)� Focused only on Current Human Exposures� Intended to catch the worst � for Environ. Indicators (EI) interim

determinations only [was flexible]� Directly addresses only residential settings

! OSWER (One Cleanup -RCRA, CERCLA, & Brownfields)� For Current and Future Exposures� Can be used for final determinations� Necessarily more prescriptive (but educational & is guidance)� Allows consideration of non-residential settings

A9

�RCRA EI Guidance�- 10/01- now superseded by OSWER

Modeling w/ measured inputs OK for EI

All Homes

Paul Johnson

Todd McAlary

Ian HersA9

A10

Continuing EvaluationOSWER�s draft-Vapor Intrusion Guidance (Part I-F)

! Guidance� Overly protective? �false positives�� Not protective enough? �false negatives�

! The answer:� OSWER � Vapor Intrusion database (VI db)

! Dr. Dawson initiated! Contractor now expanding

� dependant upon voluntary submissions! Helps us all � improved accuracy of predictions

� Less unnecessary sampling� More resources to focus on real problems� Better confidence that public is protected

IA Vapor Intrusion database frame-work by DPRA/RTI

A11

Why Concerned ?OSWER�s draft-Vapor Intrusion Guidance (Part II-A)

! Extreme cases:� Explosions� Acute health effects� Aesthetic effects (e.g., odors)

! Typically:� Low or Non-Detectable (ND) concentrations

� Often very difficult to distinguish from �background�� Chronic effects

! Risks (probabilities), given long exposure (and latency) periods

A12

How Different ?OSWER�s draft-Vapor Intrusion Guidance (Part II-B)

! Much less experience with vapors� Than groundwater or soils

! Not fully understood [a problem for final decisions]! [regulatory goal is not entertainment (risk reduction is)]

! Response options limited� Breathing harder to avoid than ingestion [> 100 x gw exposures?]

! More complex� Often indirect measurements

! �Background�� Personal living spaces, public relations & risk communication� Characterization needs [temporal nature, 2+ media, > gw alone, co-plumes]

A13

How do you use ?OSWER�s draft-Vapor Intrusion Guidance (Part III-A)

! Overall approach� RCRA (Corr. Act. Environmental Indicator) EI-like

! Analytical steps� Intended to be logically tiered � Evaluation of exposure pathway completeness (& risks)

! Record Sheets� Succinct documentation of evidence driving responses� Provide Clarity and Transparency of decisions� Professional judgment required� Technically defensible = goal

A14

How do you start ?OSWER�s draft-Vapor Intrusion Guidance (Part III-B)

� DQO (Data Quality Objectives) - App. A� CSM (Conceptual Site Model) - App. B

! Tier 1 � Primary Screening� General site knowledge

! Tier 2 � Secondary Screening� Limited site data � Conc., Depth, Soil type

! Tier 3 � Site-Specific Pathway Assessment� Detailed site-specific information� Confirmatory building-specific vapor samples

A15

3 Tiers of ScreeningOSWER�s draft-Vapor Intrusion Guidance (Part III-C)

! 1 - Primary (Q1, Q2, Q3)� Identifies potential for indoor air concerns (VOC?, Bldgs?)� Screens for obvious problems

! 2 - Secondary (Generic and Semi-Site Specific)� Q4 - Empirical observation-based attenuation factors� Q5 - JE model-based attenuation factors

(function of soil type and depth to vapor source)

! 3 - Site-Specific Pathway Assessment (Q6)� Site-specific modeling to identify �most-likely-to-be-impacted�� Air measurements (sub-slab, crawlspace, indoor) �most..� bldg

� [�more than once�] [EI (only) exception]

A16

Flowcharts for ScreeningOSWER�s - Needed to allow Closure, & Future Use

Q4 Q5 Q6

EI

-

Bldg sampling

A17

AF = 0.1 for Shallow Soil Gas Target ConcentrationAF = 0.01 for Deep Soil Gas Target Concentration �Protective� Attenuation FactorsAF = 0.001 for Groundwater Target Concentration [observation-basedPolicy]** Target soil gas concentration exceeds maximum possible vapor concentration (pathway incomplete)� The target groundwater concentration is the MCL. [floor for gw mediascreen]

Q4 - Table 2-a (10-4) [2b, 2c]

A18

Q5 - Table 3a-GW (10-4)

[3b-(SG & GW), 3c-(SG &GW)]

� The target groundwater concentrations is the MCL.�� The target concentration for trichloroethylene is based on the upper bound cancer slope factor identified in EPA's draft risk assessment fortrichloroethylene (US EPA, 2001). The slope factor is based on state- of-the-art methodology, however the TCEassessment is still undergoing review. As a result, the slope factor and the target concentration values for TCE may be revised further. (See Appendix D )

From controlled J&E model graphs

A19

What Conditions ?OSWER�s draft-Vapor Intrusion Guidance (Part IV-A)

! Suspect the presence �

! of volatile chemicals! Henry�s Law Constant (> 10-5 atm m3/mole)

[+ NAPL?]

! Source within �100� ft depth

! Buildings (existing or future) w/n �100� ft

A20

Risk Management Goals ?OSWER�s draft-Vapor Intrusion Guidance (Part IV-B)

! Guidance does NOT address this issue:� Uses consensus toxicity values

! Site evaluation should consider:� All factors, and� Professional judgment

! Recommend:� Lead regulatory authority selects:� Most appropriate values (for site evaluation)

! [100x range of (cancer) screening values in tables]! [10-6, 10-5, and 10-4 cancer risk; equally �incomplete�?]

A21

Use for Environ. Indicators ?OSWER�s draft-Vapor Intrusion Guidance (Part IV-C)

! Confirmatory sampling NOT generally needed! [Unless (more accurate) site model also predicts a problem;

! If more accurate model: � Using all Q5 model inputs (except where site-measured):

! Shows �most-likely-to-be-impacted� buildings:� Unlikely to be a problem,� Confirming an unlikely problem is really not one is not a priority

! For EI (interim) determinations (at this time)]� Recommend 10-5 cancer risks be used for EI [for VI]

! Due to practical - sampling, MDL, & �background� issues! [Better to get all sites to <10-5 than a fewer to <10-6 and others >>]

A22

Use by RCRA & CERCLA ?OSWER�s draft-Vapor Intrusion Guidance (Part IV-D)

! Current Human Exposures Under Control (EI)� RCRA (at GPRA-baseline facilities)� CERCLA (at NPL (National Priority List) sites)

! Remedial Investigations (RI)� CERCLA sites

! RCRA Facility Investigations (RFI)� RCRA Corrective Action facilities

A23

What�s Changed ?OSWER�s draft-Vapor Intrusion Guidance (Part IV-E)

! Previous Federal guidance:� Air/Superfund Guidance (1992) � Superfund Soil Screening Levels Guidance (1996)

! J&E model website spread-sheets & User�s Guide (1997)� RCRA Cor. Act. Supplemental EI Vapor Guidance (2001)

! This is �most up-to-date�� New default parameters in Q5 (also in CERCLA web site J&E)� Supplemental Guidance for SSL � consistent with this� App. E sampling methods will be continuously updated

A24

If I have Indoor Air ?OSWER�s draft-Vapor Intrusion Guidance (Part IV-F)

! Do NOT recommend sampling indoor air first� If you already have it: � Generally recommend it �be considered� [right buildings?]� If Indoor Air Quality exceeds target levels:

! Simultaneous � Tier 3 Site-Specific Pathway Assessment, and � Tier 1-2 Subsurface assessment

� Option for mechanical vapor controls � at any time! Responsible Parties may find it cost-effective to:

� Proactively:! Control potential exposures (e.g., sub-slab vapor systems), or! Sample indoor air � hopefully with regulator coordination

A25

What else to consider ?OSWER�s draft-Vapor Intrusion Guidance (Part IV-G)

! Positively pressured buildings� Indoor air quality measurements from them:

! Won�t tell much about subsurface vapor intrusion

! Likely incomplete pathway:� May be possible to show:

! Significant pressure differential from building to subsurface

� Throughout entire building� Over time

A26

Background vs Sub-surfaceOSWER�s draft-Vapor Intrusion Guidance (Part IV-H)

! Critical to consider �background� contribution (App. I)� Indoor sources (of �background� vapors) [John Boyer, NJDEP]

! Activities (smoking, craft hobbies)! Consumer products stored & used (cleaners, paints, glues)

� In homes or attached garages (auto, power equipment, pesticides)� Outdoor sources (of �background� vapors)

! Urban air! Local emissions point sources! Mobile sources

! Recommend:� Inspection, Survey, Removal (of indoor sources)� Sample outdoor air (same time as indoor)

! May be difficult to distinguish �background� from site related �

A27

BACKGROUND VOC LEVELS IN MITIGATED HOMES Redfield Facility

0.01

0.1

1

10

100

-100 0 100 200 300 400 500

Days After System Installation

Conc

entra

tion

(ug/

m3 ) 1,1 DCE

DCM

1,1 DCA

1,1,1 TCA

1,2 DCA

PCE

TCE

VC

(D. Folkes, 2000)

Note

A28

99.5% Reduction Possible

$1,000 -$2,500

Cuts off the Path-way

A29Concentration Gradient � (> two samples, in space & time)Continuous from subsurface source to receptor ?

Arrows point from high to low concentration

IAQ > std ?

Un-official Simplification:

Soil Gas >�std� ?

Groundwater >�std� ?

Crawl-space air >�std� ? Sub-slab vapor >�std� ?

AttachedGarage

�Comparisons�

Soil Gas >�std� ?

A30

Closing Overview Issues

! Vapor Intrusion Data Base: � The answer - to improved predictive power � Help us � Understanding only improves with your submissions

! Comments are due Feb. 27th

! EI approach exception: [essentially = to RCRA guidance]! Superfund spreadsheets � changed to support this:

� Non-residential X-rates, Vol., Exposure Durations (20 m3/d)! Appendices

� Wealth of information (A-I)! Highlights (from San Fran.) in Links to Additional Resources

A31

Questions on Overview ?

A32

Tier 1 (Part IV)Primary Screening

! First and highest-priority screening step! Highest potential for health effects �! are (or should be) � ! caught here

! To �quickly identify � any potential exists� &! �To help quickly screen out sites�

! Screening starts here ! If not here = unknown risks! If inappropriately screened out here = unknown risks

! If �any potential exists � unacceptable � risks�

A33

Tier 1- Primary ScreeningOSWER�s draft-Subsurface Vapor Intrusion Guidance

! �quickly identify � any potential exists�

! Q1 Volatiles?! Q2 Buildings?! Q3 Immediate concerns?

! If � not � �incomplete� � proceed to Secondary Screening

!

! [next presentation by Dr. Helen Dawson]

A34

A35

Compile Site Information

! Conceptual Site Model (CSM)! Should include possibility of vapor intrusion! See Appendix B

! Data Quality Objectives (DQO)! Scope of analytes for source (and potential

degradation products !)! Detection limits adequate?! See Appendix A

A36

Q1 Got Volatiles ?

! Chemicals of �sufficient volatility and toxicity�� See Table 1 - �Known or reasonably suspected�:� In subsurface:

! Unsaturated soils � residual NAPL vertical decent column?! Soil gas � from groundwater, soils, or �vapor clouds�! Uppermost portions of groundwater � dissolved or LNAPL! Capillary fringe contaminated? � [VOC stripper or inhibitor?]

! If �Yes� check off in Table 1� Check offs (+ potential degradation products) = Constituents

of Concern (COCs) forward! If �No� document pathway as �incomplete�! If don�t know � Should find out

A37

Q1 Table 1

! Table 1 = Lookup & Check off List = documentation

� Chemicals �that may be found� 160! Acenaphthene to Vinyl Chloride

! Sufficiently? � Toxic = �pure component� vapor with:

� (individual chemicals)! Lifetime Incremental Increase in Cancer >10-6

� or ! Hazard Index of 1 (or more) (-10) And

� Volatile = Henry�s >10-5 atm-m3/mol (-36)! [From dissolved state only?]

� Players = 114

A38

1 A chemical is considered sufficiently toxic if the vapor concentration of the pure component (see Appendix D) poses an incremental lifetimecancer risk greater than 10 -6 or a non-cancer hazard index greater than 1.2 A chemical is considered sufficiently volatile if its Henry�s Law Constant is 1 x 10 -5 atm-m 3 /mol or greater (US EPA, 1991).3 Users should check off compounds that meet the criteria for toxicity and volatility and are known or reasonably suspected to be present.

Table 1 (for Q1)

A39

Q1 Keep in Mind ?

! Data Quality Objectives (DQO) � App. A� Detection Limits� Adequacy of definition of �nature and extent�

! Groundwater � All COCs� All Areas [needed to find if a site is a problem?]� Top of the water table most important

! Vadose zone � Soils� Vapors

! Conceptual Site Model (CSM) � App. B! Relevant Methods and Techniques � App. E

A40

Q2 Got Buildings ?

! Currently (or potentially) Inhabited/able� Or areas of concern under future development

! Located �near� ?

! If �Yes� identify buildings or areas� Note whether current or future (on forms)

! EI = only concerned with current conditions

! If �No� document pathway as �incomplete�! If don�t know � Should find out

A41

Q2 Definitions

! Buildings = � w/ Enclosed air space designed for human occupancy

! �Near� = � w/n approx. 100 ft laterally or vertically of� Known or interpolated:

! Soil gas, or ! Groundwater (adjacent to soil atmosphere)

� Use professional judgment � 100 ft may not be appropriate for all sites

A42

Q2 Why is 100 ft �Near� ?

! To focus on Buildings (or areas) �most likely� � Generally decreasing conc. with distance to source� Exact distance to �negligible� concentration: � Function of:

! Chemical mobility, toxicity, persistence; Source geometry;! Subsurface material and Building characteristics, etc�

! Empirical evidence (to date) indicates 100 ft is:� Reasonable Criterion

! Reflects uncertainty in typical characterization data sets

! Practical and implement-able

A43

Q2 Keep in Mind ?

! Why >100 ft may be still �near�! �Significant� Preferential Pathways

� Natural ! Fractures, macro-pores = vertical or horizontal

� Anthropogenic! Utility conduits, subsurface drains = typically horizontal

� High gas-permeability� Sufficient volume and proximity

! To �influence� vapor intrusion

A44

Q2 Keep in Mind continued ?

! Consider:

! Mobile �vapor clouds� (gas plumes)� Landfills

! Methane carrier gas (known to be 100s ft distant)� Commercial/Industrial settings

! Dry cleaning facilities �density driven downward migration out of building

� May be transported several hundred feet from source! Gas leaks from tanks and piping

� (never was a liquid release)

A45

Q2 Keep in Mind continued p. 2 ?

To be applied to:� �Existing groundwater plumes�� �As they are currently defined�

! MCLs, State Standards, or Risk-Based Conc.! [only limited empirical evidence for concern]! [If worst is < MCL, priority is questionable (at this time)]

However - very important to recognize:Non-potable aquifers may not be defined adequately for vapor intrusion

A46

Non-Drinking Water Aquifers- Only Characterized to ? x MCLIs that a problem for screening VI potential ? Not really

C l i c k h e r e t o t y p e s u b t i t l eC l i c k h e r e t o t y p e s u b t i t l e

C l i c k h e r e t o a d d c l i p a r t

Fan, 2000

Defina, 2000

Real

Problem ?

Can ? x MCL contours (or poor characterization) be a problem for VI delineation ? YES

If there are (�most-likely�) buildings over higher conc.

A47

1,1 DCE in Indoor Air (Redfield Facility, Denver, Colo., Folkes, 2000)

REF

REF

FORMERREDFIELDFACILITY

REF

REF

REFREFREF

(µg/cubic meter)

<=0.46

0.46 to 4.5

4.6 to 45

>45

1,1 DCE RESULTS

REF REFUSED ACCESS FOR SAMPLING/NO RESPONSE

NEGATIVE NUMBER INDICATESRESULT BELOW DETECTION LIMIT

APPROXIMATE EXTENT OF DETECTED VOLATILE ORGANIC COMPOUND IN GROUNDWATER

MCL correlates OK, if gw accurately characterized

A48

Q3 Immediate Concerns ?

� Does evidence (qualitative criteria) suggest:

! Immediate action is warranted �

� to mitigate current risks?

! If �Yes� proceed with appropriate actions to:� �verify or eliminate� imminent risks

! If �No� Go on to Question 4 (Secondary Screening)

A49

Q3 Qualitative Criteria ?

! Odors � reported by occupants as:� �Chemical, solvent, or gasoline�

! Prudent to act � as odor thresholds can be �high�! Physiological effects - reported by occupants:

� �dizziness, nausea, vomiting, confusion, etc.�! Wet Basements � (i.e., vapor source inside bldg)

� Cont. groundwater very shallow � esp. LNAPL! [this is no time for extended modeling]

! Short-term Safety Concerns known/expected� Explosive, flammable, corrosive, reactive, or acutely toxic

� in building or in �drains directly connected�

A50

If NO Immediate Concerns

� Proceed to:

! Secondary Screening

� Question 4

! Next presentation by Dr. Helen Dawson, EPA - R8

A51

Questions ?

Regarding any part of Tier 1 Primary Screening

B1

EPA OSWER Draft Guidance Evaluating Vapor Intrusion from Groundwater and Soil to Indoor Air

SECONDARY SCREENING

Presented by:Helen Dawson, Ph.D.US EPA Region 8Denver, CO Dawson.Helen@epa.gov

B2

Tier 2: Secondary ScreeningOverview

! Designed to �fast-track� problem sites to a site-specific evaluation that includes indoor air sampling.

! Uses the multiple lines of evidence approach. Recommends evaluation of both groundwater and soil gas data.

! Includes preliminary review of any available indoor air data.

B3

Secondary Screening � Question 4Media-Specific Target Concentrations

! Evaluation of available indoor air data.! Risk-based indoor air target screening levels.

! Generic screening of available groundwater data.! Groundwater target screening levels.! Conservative empirical attenuation factor (1/1000).

! Generic screening of available soil gas data.! Shallow soil gas (<= 5 ft below foundation level) and

deep soil gas (> 5 ft below foundation level) screening levels. ! Conservative shallow and deep soil gas empirical attenuation

factors (1/10 & 1/100).

B4

Calculation of Indoor Air Target Screening Levels! For carcinogens:

! Ccancer (:g/m3) = [(TCR * ATc)/(EF * ED * URF)]

! TCR = target cancer risk (e.g., 1.0 x 10-5) ! ATc = averaging time, carcinogens (25,550 days)! EF = exposure frequency (350 days/year)! ED = exposure duration (30 years)! URF = unit risk factor (:g/m3)-1

! For non-carcinogens:

! Cnon-cancer (:g/m3) = (THQ * RfC * 1000 :g/mg)

! THQ = target hazard quotient (e.g., 1.0)! RfC = reference concentration (mg/m3)

B5

Calculation of Soil Gas and Groundwater Target Screening Levels

! Select indoor air target screening level.

AF = 0.1

AF = 0.001

AF = 0.01

! Shallow soil gas screening level (SGSLshallow ) is 10 times indoor air target screening level.

SVSLshallow = IASL * 10

! Deep soil gas screening level (SGSLdeep ) is 100 times indoor air target level.

SVSLdeep = IASL * 100

! Groundwater screening level (GWSL) is the aqueous concentration corresponding to a soil gas concentration 1000 times greater than the indoor air target level.

GWSL = IASL * 1000/Hc

B6

Precluding factors! Very shallow groundwater contamination

(< 5 feet below foundation level)

! Shallow contamination (< 15 feet below foundation level), AND! Buildings with significant openings to the subsurface

(sumps, unlined crawlspaces, earthen floors, etc.)! Significant preferential pathways, anthropogenic or

natural! Buildings with very low air exchange rates or very high

sustained indoor/outdoor pressure differentials.

B7

Secondary Screening � Question 4Structure

Identify source location. Groundwater evaluation Site Specific Assessment

Proceed to Question 5 or Site Specific Assessment

Groundwater Assessment Indicates Pathway Is Incomplete

Indoor air data available? Site Specific AssessmentIndoor air data evaluation

Pathway Is Incomplete

Soil gas evaluation Site Specific Assessment

Soil Gas Assessment Indicates Pathway Is Incomplete

B8

Secondary Screening � Question 4Indoor Air Evaluation

Indoor air (IA) data available?

Evaluate Subsurface Data

NO

IA Conc. > IA Target Level?

Perform Building-Specific Assessment

NO

YES

YES

IA Data Adequate?

NO

Pathway Is Incomplete

YES

B9

Indoor Air Data Adequacy! Temporal and spatial

variability! Indoor air sources

! Consumer products ! Occupant activities! Dry cleaned garments ! Construction materials

! Background! Ambient air in urban areas

! Detection limitsHelen Dawson, EPA Region VIII

Lowry Air Force Base, CO

0

10

20

30

40

50

60

Jan-00 Apr-00 Jul-00 Sep-00 Dec-00 Mar-01

Indo

or A

ir C

once

ntra

tion

(ug/

m3) UA03

UA22UA25

0.01

0 .1

1

10

100

-100 0 1 00 20 0 300 400 500

D ays A fter S ystem Insta lla tio n

Conc

entra

tion

(ug/

m3 ) 1 ,1 D C E

D C M

1 ,1 D C A

1 ,1 ,1 T C A

1 ,2 D C A

P C E

T C E

V C

0 .01

0 .1

1

10

100

-100 0 1 00 20 0 300 400 500

D ays A fter S ystem Insta lla tio n

Conc

entra

tion

(ug/

m3 ) 1 ,1 D C E

D C M

1 ,1 D C A

1 ,1 ,1 T C A

1 ,2 D C A

P C E

T C E

V C

B10

Secondary Screening � Question 4 Subsurface Data Evaluation

! Identify Contaminant Source Location

Is there contamination (vapor source) in unsaturated zone soil?

Evaluate GROUNDWATER Data. Empirical a = 1/1000

NO

Evaluate SOIL GAS Data.Empirical a = 1/10 (< 5 ft)Empirical a = 1/100 (>5 ft)

YES

Recommended

B11

Secondary Screening � Question 4Groundwater Evaluation

Do groundwater concentrations exceed target levels?

Evaluate SOIL GAS data.

YES

Are the data adequate?

Any precluding factors?

Groundwater data indicate pathway is incomplete.

Acquire needed data

Site Specific Assessment

NO

YES

YES

NONO

B12

Groundwater Data Adequacy

! Distance from receptors

! Location of screen; screened interval

! Water table fluctuations

! Recharge

Basement Slab on gradeCrawlspace

Helen Dawson, EPA Region VIII

B13

Secondary Screening � Question 4 Soil Gas Evaluation

Soil gas concentrations exceed target levels?

Proceed to Question 5

YES

Are the data adequate?NO

Any precluding factors?

Soil gas data indicate pathway is incomplete

Acquire needed data

Site Specific Assessment

NO

YES

YES

NO

B14

Soil Gas Sampling Issues! Temporal and spatial

variability! Barometric pressure

fluctuations! Surface cover! Preferential pathways! Variable soil moisture

and permeability! Variable building

depressurization! Biodegradation! Sampling equipment! Protocols

Basement Slab on gradeCrawlspace

Helen Dawson, EPA Region VIII

B15

Tier 2: Secondary Screening � Question 4 Summary

! Groundwater, soil gas, and any available indoor air data are evaluated � the multiple lines of evidence approach.

! Sites with high concentrations are �fast-tracked� to a site-specific evaluation that includes indoor air sampling.

! Data adequacy and applicability of the screening criteria are carefully evaluated before making the decision that the vapor intrusion pathway is incomplete.

B16

Measured Attenuation FactorsDatabase Summary

! 15 Sites! CO (5 Sites)! CA (1 Site)! CT (1 Site)! MA (7 Sites)! MI (1 Site)

! 15 VOCs! BTEX (5 Sites, MA)! Chloroform (1 Site, CO)! 1,1-Dichloroethane (1 Site, CO)! 1,2-Dichloroethane (2 Sites, CO)! 1,1-Dichloroethylene (5 Sites, CO)! cis-1,2-Dichloroethylene (2 Sites, CO; 1 Site,

MI)! trans-1,2-Dichloroethylene (1 Site, CO)! Tetrachloroethylene (2 Sites, CO; 1 Site, CT)! 1,1,1- Trichloroethane (3 Sites, CO;1 Site, CT)! 1,1,2- Trichloroethane (1 Site, CO)! Trichloroethylene (8 Sites, All States)! Vinyl chloride (3 Sites, CO; 1 Site, MI)

B17

Measured Attenuation Factors

Database Summary! 15 sites, 15 VOCs, 274 total residence/chemical

combinations

! 35 BTEX; 239 CHC residence/chemical combinations

! 99 sites with IA > 10-6 IA RBC(84 CHC, 14 BTEX)

! 68 sites with IA > 10-5 IA RBC

B18

Measured Groundwater-to-Indoor Air Attenuation Factors

Measured Attenuation FactorsGroundwater to Indoor Air

0.0000001

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

0% 20% 40% 60% 80% 100%

Cumulative %

Atte

nuat

ion

Fact

or IA & GW > MDL

IA > 10-6

IA > 10-5

B19

Influence of Foundation Structure?

Database

1

10

100

1000

10000

100000

1000000

10000000

0.01 0.1 1 10 100 1000

Indoor Air (ug/m3)

Gro

undw

ater

Sou

rce

Vapo

r (u

g/m

3)

BasementCrawlspaceSlab on Grade1:1

Groundwater

B20

Influence of Foundation Structure?

Lowry Air Force BaseFoundation Vapor vs Indoor Air

0.01

0.1

1

10

100

1000

10000

0.01 0.1 1 10 100Indoor Air (ug/m3)

Subs

lab

or C

raw

lspa

ce

(ug/

m3) Basement

Crawlspace1:1

B21

Influence of Soil Type?Database

1

10

100

1000

10000

100000

1000000

10000000

0.01 0.1 1 10 100 1000

Indoor Air (ug/m3)

Gro

undw

ater

Sou

rce

Vapo

r (u

g/m

3)

Silts & ClaysSands1:1

B22

Depth to Groundwater?Groundwater Indoor Air Attenuation Factor

Versus Depth to Water

1

10

100

1000

10000

100000

1000000

10000000

0.0 2.0 4.0 6.0 8.0 10.0 12.0

Depth to Water (m)

1 / A

ttenu

atio

n Fa

ctor

SandsSilts & Clays

B23

Empirical Attenuation Factors

Conclusions! Measured attenuation factors range from

10-2 to 10-7 with median values around 10-4.

! Influence of foundation type, soil type, and depth to water on the empirical attenuation factors is unclear.

! Higher ranges of attenuation factors are observed for BTEX compounds; median value is around 10-5.

B24

EPA OSWER Draft Guidance Evaluating Vapor Intrusion from Groundwater and Soil to Indoor Air

Question 5 �Semi-Site Specific Screening

Presented by:Helen Dawson, Ph.D.US EPA Region 8Denver, CO Dawson.Helen@epa.gov

B25

Secondary Screening � Question 5Overview

! Semi-site specific screening using limited site data.

! Soil type! Depth to source

! Attenuation factors based on Johnson-Ettinger Model.

! Not applicable to all sites! Attenuation factors vary with soil type and depth to

vapor source

! Only applied to sites with groundwater or soil gas concentrations less than 50 times media specific target levels.

B26

Secondary Screening � Question 5Attenuation Factors

Figure 3b- DRAFTVapor Attenuation Factors - Ground Water to Indoor Air Pathway

Basement Foundations

1.0E-05

1.0E-04

1.0E-03

1.0E-02

Depth to Contamination from Foundation (m)

Sand Sandy Loam Loamy Sand Loam

Vapo

r Atte

nuat

ion

Fact

or

7.0E-045.0E-043.0E-042.0E-04

0 5 10 15 20 25 30

B27

Secondary Screening � Question 5Attenuation Factors

Figure 3a- DRAFTVapor Attenuation Factors - Soil Vapor to Indoor Air Pathway

Basement Foundations

1.0E-05

1.0E-04

1.0E-03

1.0E-02

Depth to Contamination from Foundation (m)

Vapo

r Atte

nuat

ion

Fact

or

Sand Sandy Loam Loamy Sand Loam

2.0E-03

7.0E-04

4.0E-04

2.0E-04

0 5 10 15 20 25 30

B28

GW or SG concentrations > 50 times Q4 target levels?

Secondary Screening � Question 5Applicability Testing

Site Specific AssessmentYES

Any factors precluding use of Johnson-Ettinger model?

NO

Are depth to water and soil type adequately characterized?

NO

Site Specific AssessmentYES

Acquire needed data and re-evaluate.

NO

Proceed to data evaluation

YES

B29

Why skip Q5 if concentrations exceed Q4 screening levels by 50x?

Figure 3b- DRAFTVapor Attenuation Factors - Ground Water to Indoor Air Pathway

Basement Foundations

1.0E-05

1.0E-04

1.0E-03

1.0E-02

Depth to Contamination from Foundation (m)

Sand Sandy Loam Loamy Sand Loam

Vapo

r Atte

nuat

ion

Fact

or

7.0E-045.0E-043.0E-042.0E-04

0 5 10 15 20 25 30

Figure 3a- DRAFTVapor Attenuation Factors - Soil Vapor to Indoor Air Pathway

Basement Foundations

1.0E-05

1.0E-04

1.0E-03

1.0E-02

Depth to Contamination from Foundation (m)

Vapo

r Atte

nuat

ion

Fact

or

Sand Sandy Loam Loamy Sand Loam

2.0E-03

7.0E-04

4.0E-04

2.0E-04

0 5 10 15 20 25 30

Groundwater Soil Gas

X 20 X 50

B30

Secondary Screening � Question 5Data Evaluation

GW > TL? Groundwater AssessmentIndicates Pathway Incomplete

NONOIs there a source of contamination (vapor source) in unsaturated zone soil?

SG > TL?

Site Specific Assessment

Soil Gas AssessmentIndicates Pathway Incomplete

NO

YES

YES

B31

Tier 2: Secondary ScreeningSummary

! Groundwater and soil gas data are evaluated.

! Sites with high concentrations are �fast-tracked� to a site-specific evaluation that includes indoor air sampling.

! Data adequacy and applicability of the screening criteria are carefully evaluated before making the decision that the vapor intrusion pathway is incomplete.

B32

Evaluating Vapor Intrusion from Groundwater to Indoor Air �Reliability Assessment

Helen Dawson, Ph.D.Regional Superfund HydrogeologistUS EPA Region VIIIDenver, CO(303) 312-7841Dawson.Helen@epa.gov

B33

Reliability AssessmentApproach

! Using database, evaluate number of false negatives and false positives using:

! Empirical, screening-level attenuation factors

! JE model-derived attenuation factors as a function of soil type and depth to water

! JE model, site-specific attenuation factors

B34

Reliability Assessment

IASL<C(IA)CORRECT

NEGATIVEGWSL<C(GW)

IASL<C(IA)FALSE

POSITIVEGWSL>C(GW)IASL>C(IA)

FALSE NEGATIVE

GWSL<C(GW)

IASL>C(IA)CORRECT POSITIVE

GWSL>C(GW)

ConditionVapor Intrusion Screening LevelRelationshipMeasurement

Qualitative Evaluation Criteria

B35

Reliability Assessment

Caveats and Qualifications! False negatives can be due to �..

! Indoor air sources! Ambient outdoor sources! Groundwater sampling point distant from

structure! VOC losses in sampling groundwater or soil gas

! False positives can be due to ��! Unrepresentative indoor air measurement! Seasonal variability

B36

Reliability Assessment by Buildings

Total CP and CN

66%Total FP2%

Total FN0%

Total NA32%

R = 10-5, HI = 1

B37

Reliability Assessment by Chemical

N FP FN N FP FN N FP FN N FP FN N FP FN

VI Q4 3 13 0 0 13 0 1 26 0 0 13 0 0 13 0 0VI Q5 4 13 0 0 13 0 1 26 0 0 13 0 0 13 0 0

trans 12DCE

11DCE cis 12DCE11DCA 12DCA

R = 10-5, HI = 1

B38

Reliability AssessmentResults

! No false negatives for site buildings at any risk level.

! Limited number of false positives for site buildings.

! No false negative for chemicals at 10-5 and 10-4 risk level.

! No false negatives for chemicals at 10-6, except for 1,2-DCA and PCE at one site.

B39

Measured Attenuation Factors Versus Modeled Attenuation Factors

! Site specific, calibrated JE model (Best we can expect!)

1.00E-07

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-07 1.00E-06 1.00E-05 1.00E-04 1.00E-03

Measured Attenuation Factor

Pre

dict

ed A

tten

uat

ion

Fac

tor BTEX

Solvents

1:1

10x Overpredict

0.1x Underpredict

Data Source: Johnson et al., 2002; Hers et al., 2002

B40

Reliability Assessment

Conclusions! Preliminary evaluation of empirical attenuation

factors suggests screening level attenuation factors of 1/1000 applied to groundwater data are conservative (minimize false negatives).

! Preliminary evaluation of semi-site specific (JEM-based) attenuation factors indicates new model defaults are conservative (minimize false negative).

! The JE model when calibrated with site-specific data estimates attenuation factors with a range of +/- one order of magnitude. Therefore need safety factor of at least 10x to use as regulatory tool.

C1

Vapor Intrusion Into Indoor Air: Introduction to OSWER Guidance

An Overview of Question 6 of the Guidance �Site-Specific Assessment

February 11 and 12, 2003

Dominic DiGiulio, Ph.D.U.S. Environmental Protection AgencyOffice of Research and Development

National Risk Management Research LaboratoryAda, Oklahoma

C2

Primary Defining Characteristics of Q6

� Site-specific mathematical modeling for EI determinations

� Indoor air sampling

� Sub-slab sampling

C3

Critical Statements in Guidance

� This guidance is not a regulation. It represents current technical and policy recommendations of the Office of Solid Waste and Emergency Response (OSWER). EPA personnel and states are free to use other technically sound approaches. In addition, users are free to modify the approach recommended in the guidance.

� The guidance is designed to differentiate sites (not locations) where vapor intrusion is more likely from siteswhere vapor intrusion is less likely. The guidance is not intended to provide an approach or recommendations on how to delineate the extent of risk.

C4

Q6 Flow Chart from Guidance

C5

YES

6(a) Has the nature and extent of contamination, preferential pathways and

overlying building characteristics been �adequately� characterized to identify the

most likely-to-be-impacted buildings?

6(b) Are you conducting an EI determination using an

�appropriate� and �applicable� model?

6(c) Does the model predictan unacceptable risk?

6(d) Is subslab soil-gas data available?

6(e) Do subslab vapor concentrations exceed target levels?

6(g) Do indoor air concentrations exceed target levels?

6(i) Have background indoor and outdoor sources been �adequately� accounted for?

COMPLETE PATHWAY

Is indoor air dataavailable?

6(f) Is subslab dataadequate?

Collect subslab data.

Collect indoor air dataat various seasons.

Collect backgroundair data.

NO

YES

YES

YES

YES

YES

YES

YES

Acquire neededdata.

YES

NO

NO

INCOMPLETE PATHWAY FOR EI DETERMINATION.

(Indoor air sampling at closure.)

NO

INCOMPLETEPATHWAYNO

NO

NO

NO

NO

YES

NO

Path (EI) to an incomplete

pathway with �adequate� site

characterization �no modeled risk

6(h) Do IA conc. �adequately� accountfor seasonal variability and represent the most likely-to-be-impacted

buildings?

C6

Inherent Philosophy of Model Application for EI Determinations Associated with Vapor

IntrusionSoil-gas and/or ground-water data in conjunction with �conservative� Q4, Q5 target concentrations indicate potential exposure. Site-specific modeling (which is expected to be less conservative but more realistic) is now used to determine:

- the need for sub-slab and indoor air sampling, and- whether an incomplete pathway for EI purposes can be declared without sub-slab and indoor air sampling.

(Note, that this �does not necessarily reflect a final decision that the site is clean without confirmatory sampling.�)

C7

Site-Specific Modeling for EI Determinations

� Select an �appropriate� and �applicable� model (model selection not limited to the Johnson-Ettinger (JE) Model)

� If the JE Model is used, then EPA recommends that �site-specific information include soil moisture, soil permeability, building ventilation rate, and subslab as well as deep vapor concentrations.�

� �Model output [should] be compared with measured concentrations, fluxes and/or other model outputs�the JE model when used as a site-specific tool should be calibrated to predict within an order of magnitude the indoor air concentrations resulting from the subsurface.�

C8

The Johnson-Ettinger Model (as implemented by EPA) should not be used when any of these

conditions are present (page G-2).

� Presence or suspected presence of free or residual NAPL,� Karst or fractured geologic media,� Sites where significant lateral transport of vapors occurs,� When the building foundation is wetted by ground water,� Buildings with very low air exchange rates (e.g., < 0.25/hr),� Buildings with significant openings to the subsurface (e.g.,

sumps, unlined crawlspaces, earthen floors), � Large fluctuation in the water table,� When transient vapor transport is a factor.

C9

YES

6(a) Has the nature and extent of contamination, preferential pathways and

overlying building characteristics been �adequately� characterized to identify the

most likely-to-be-impacted buildings?

6(b) Are you conducting an EI determination using an

�appropriate� and �applicable� model?

6(c) Does the model predictan unacceptable risk?

6(d) Is subslab soil-gas data available?

6(e) Do subslab vapor concentrations exceed target levels?

6(g) Do indoor air concentrations exceed target levels?

6(i) Have background indoor and outdoor sources been �adequately� accounted for?

COMPLETE PATHWAY

Is indoor air dataavailable?

6(f) Is subslab dataadequate?

Collect subslab data. 6(h) Do IA conc. �adequately� accountfor seasonal variability and represent the most likely-to-be-impacted

buildings?

Collect indoor air dataat various seasons.

Collect backgroundair data.

NO

YES

YES

YES

YES

YES

YES

YES

Acquire neededdata.

YES

NO

NO

INCOMPLETE PATHWAY FOR EI DETERMINATION.

(Indoor air sampling at closure.)

NO

INCOMPLETEPATHWAYNO

NO

NO

NO

NO

YES

NO

Path to a Complete

Pathway with �adequate� site characterization

C10

YES

6(a) Has the nature and extent of contamination, preferential pathways and

overlying building characteristics been �adequately� characterized to identify the

most likely-to-be-impacted buildings?

6(b) Are you conducting an EI determination using an

�appropriate� and �applicable� model?

6(c) Does the model predictan unacceptable risk?

6(d) Is subslab soil-gas data available?

6(e) Do subslab vapor concentrations exceed target levels?

6(g) Do indoor air concentrations exceed target levels?

6(i) Have background indoor and outdoor sources been �adequately� accounted for?

COMPLETE PATHWAY

Is indoor air dataavailable?

6(f) Is subslab dataadequate?

Collect subslab data.

Collect indoor air dataat various seasons.

Collect backgroundair data.

NO

YES

YES

YES

YES

YES

YES

YES

Acquire neededdata.

YES

NO

NO

INCOMPLETE PATHWAY FOR EI DETERMINATION.

(Indoor air sampling at closure.)

NO

INCOMPLETEPATHWAYNO

NO

NO

NO

NO

YES

NO

Path to a complete

Pathway with �inadequate�

site characterization

6(h) Do IA conc. �adequately� accountfor seasonal variability and represent the most likely-to-be-impacted

buildings?

C11

YES

6(a) Has the nature and extent of contamination, preferential pathways and

overlying building characteristics been �adequately� characterized to identify the

most likely-to-be-impacted buildings?

6(b) Are you conducting an EI determination using an

�appropriate� and �applicable� model?

6(c) Does the model predictan unacceptable risk?

6(d) Is subslab soil-gas data available?

6(e) Do subslab vapor concentrations exceed target levels?

6(g) Do indoor air concentrations exceed target levels?

6(i) Have background indoor and outdoor sources been �adequately� accounted for?

COMPLETE PATHWAY

Is indoor air dataavailable?

6(f) Is subslab dataadequate?

Collect subslab data.

Collect indoor air dataat various seasons.

Collect backgroundair data.

NO

YES

YES

YES

YES

YES

YES

YES

Acquire neededdata.

YES

NO

NO

INCOMPLETE PATHWAY FOR EI DETERMINATION.

(Indoor air sampling at closure.)

NO

INCOMPLETEPATHWAYNO

NO

NO

NO

NO

YES

NO

Path to an incomplete

pathway with �adequate� site characterization

6(h) Do IA conc. �adequately� accountfor seasonal variability and represent the most likely-to-be-impacted

buildings?

C12

YES

6(a) Has the nature and extent of contamination, preferential pathways and

overlying building characteristics been �adequately� characterized to identify the

most likely-to-be-impacted buildings?

6(b) Are you conducting an EI determination using an

�appropriate� and �applicable� model?

6(c) Does the model predictan unacceptable risk?

6(d) Is subslab soil-gas data available?

6(e) Do subslab vapor concentrations exceed target levels?

6(g) Do indoor air concentrations exceed target levels?

6(i) Have background indoor and outdoor sources been �adequately� accounted for?

COMPLETE PATHWAY

Is indoor air dataavailable?

6(f) Is subslab dataadequate?

Collect subslab data.

Collect indoor air dataat various seasons.

Collect backgroundair data.

NO

YES

YES

YES

YES

YES

YES

YES

Acquire neededdata.

YES

NO

NO

INCOMPLETE PATHWAY FOR EI DETERMINATION.

(Indoor air sampling at closure.)

NO

INCOMPLETEPATHWAYNO

NO

NO

NO

NO

YES

NO

Path to an Incomplete

Pathway with �inadequate�

site characterization

6(h) Do IA conc. �adequately� accountfor seasonal variability and represent the most likely-to-be-impacted

buildings?

C13

Questions?

C14

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