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USEPA�s (OSWER) Draft Guidance forEvaluating the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 [email protected]
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 [email protected]
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) [email protected]
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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