Evaluation of Subsurface Vapor Intrusion to Indoor Air:

1. Evaluation of Subsurface Vapor Intrusion to Indoor Air: A Developing Technical and Regulatory Landscape

2. Outline • What is Vapor Intrusion? Why Should You Be Concerned? • Federal Draft Vapor Intrusion Guidance • Various States’ Vapor Intrusion Guidance • Comparison of Numerical Standards • Current Approach in California • Mitigation Alternatives • Future Trends • Questions

3. Vapor Intrusion: What Is It? Vapor Intrusion is the migration of volatile chemicals from the subsurface into overlying buildings.

4. Why is the Pathway of Concern? • Safety Hazards (e.g., explosion) • Health Risks • People spend > 90% of their time indoors • Often cannot see, smell, or taste VOCs • Acute and chronic effects • Risks may greatly exceed those due to other direct-contact pathways • Ingestion and/or dermal contact with soil • Ingestion of groundwater

5. Why Should You Be Concerned? • Regulations/guidance Being Developed (State of Flux) - Various Evaluation Approaches Throughout the U.S. • Likely Require Additional Evaluation • May Result in Reopening of Previously Closed Sites • May Require Mitigation Measures Where Previously Not Required • Potential Increase in Future Liability/Risk

6. USEPA Draft Vapor Intrusion Guidance • Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils, November 2002 • Only Residential Receptors • Tier 1 - Primary Screening • Identifies potential for indoor air pathway • Screens for immediate/acute problems • Tier 2 - Secondary Screening • Generic screening values (empirical) • Semi-site specific screening values (modeled) • Tier 3 - Site-Specific Assessment • Indoor air and/or sub-slab measurement • Site-specific, calibrated modeling

7. Proposed Revisions to USEPA Vapor Intrusion Guidance Obtained from Helen Dawson’s presentation at AEHS in March 2005

8. Major Proposed Revisions to USEPA Guidance • Revision of list of potential chemicals of concern • Addition of non-residential receptor evaluation • Less conservative attenuation factors for some media at screening level • More user-friendly and comprehensive calculation spreadsheet including sensitivity analysis • More site-specific parameters allowed in modeling • Information regarding evaluation of indoor air data using multiple lines of evidence

9. Interstate Technology & Regulatory Council (ITRC) • State-led coalition objective to achieve regulatory acceptance of environmental technologies • Technical work teams develop guidance and classroom and Internet-based training • General survey findings: • 39 of 43 states: vapor intrusion is a current concern being addressed • 6 of 43 states: vapor intrusion regulation in codified into law or regulation • 7 additional states have defined policy • 26 states: operating under information procedures • Most preferred sample method: soil gas/subslab sampling followed by indoor air; least preferred method: flux chambers Obtained from ITRC Vapor Intrusion Team March 2005 presentation

10. History of VI Guidance Development NYSDEC Endicott, NY VI Project Federal Guidance MA DEP IA Sampling Guide & Proposed Revisions MI DEQ Revisions PA DEP Volatilization Criteria CO DPHE IA Guidance NYS DEC Draft Policy CA DTSC VI Guidance NYS DOH IA Background Study CT DEP Numerical Standards MI DEQ Volatilization Criteria NH DES Standards NH DES Residential IA Assessment Guide CO DPHE IA Analysis Guide NYS DOH Draft SVI Guidance Upcoming Guidance: NJ DEP IN DEM? TX CEQ? NYS DOH Updated IA Background Study CT DEP Proposed Revisions MA DEP Numerical Standards CO DPHE Redfields, CDOT Sites Michigan Science Board Evaluation NYS DOH IA Sampling Guide NJ DEP IA Sampling Guide IL EPA IA Testing SE Rockford Site 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

11. Not evaluated Defers to federal program Developed/developing program with varied flexibility Developed program with varied flexibility, including numerical standards/screening criteria Conservative program with substantial regulatory oversight Currently developing guidance No guidance; pathway not evaluated currently State Vapor Intrusion Guidance

12. Target Residential Indoor Air Concentrations

13. Reasons Indoor Air Targets Vary • Target risk levels (especially cancer risk level) • Toxicity factors (especially carcinogenic unit risk) • Background values • Odor thresholds • Analytical quantitation limits • Exposure factors (i.e., exposure duration, inhalation rate, body weight) • Groundwater targets: Even wider range of variability due to State-specific default geologic and building assumptions

14. Trichloroethylene Target Indoor Air Concentrations (10-6 to 10-4 risk) (H. Dawson, EPA Region 8, Technical Publication, “Trichloroethylene Inhalation Toxicity Values andCorresponding Risk Based Indoor Air Concentrations,” 26 January 2005) Ranges of target indoor air concentrations corresponding to 10-6 to 10-4 cancer risk levels for different TCE toxicity values.

15. Preference for Measurement vs. Modeling Not evaluated Modeling recommended prior to indoor measurements (federal approach) Indoor or sub-slab measurements desired Not applicable; pathway not evaluated currently

16. States Utilizing Indoor Air Background Not reviewed, VI guidance does not currently exist, or background not considered Indoor air background considered quantitatively (in standards or evaluation) Indoor air background considered qualitatively (Weight of Evidence approach) Defers to federal program (background considered but included in Risk Assessment)

17. OSHA Applicability Not evaluated OSHA regulates workplace (current federal position) Hazardous waste program regulates workplace Hazardous waste program regulates if subsurface VOCs differ from workplace; OSHA regulates if subsurface VOCs are same as workplace

18. California Interim Final Vapor Intrusion Guidance • Interim Final Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air, February 7, 2005 • Comments due by August 15, 2005 • 11 Evaluation Steps (Very Prescriptive): • Steps 1 – 3: Identify source, characterize site, identify whether vapor intrusion is complete pathway • Step 4: Imminent hazard? • Step 5: Preliminary screening evaluation • Steps 6 and 7: Additional data collection and site-specific evaluation (modeling) • Steps 8, 9, and 10: Indoor air sampling (existing buildings) • Step 11: Mitigation and long-term monitoring

19. California Interim Final Vapor Intrusion Guidance – Noteworthy Items • Chemicals: Number larger than LARWQCB soil gas list, SFRWQCB soil gas ESLs, USEPA list; includes semi-volatile organics (e.g., DDT) [Table 1] • Temporal: 2 soil gas events [page 5] • Vertical: Soil gas samples collected at minimum of 5 and 15 to 20 feet; if groundwater contamination also at capillary fringe and half-way to surface • Lateral: demonstrate “clean zone” of 100 feet beyond extent of soil gas plume [page 6] • Number of samples: Recommended numbers/locations for soil gas and indoor air samples

20. California Interim Final Vapor Intrusion Guidance – Noteworthy Items • Utility corridors: Assessment required [page 24] • Flux chamber: Not recommended [page 11] • Non-detects: Evaluate vapor intrusion even if concentrations in soil gas are non-detectable if chemicals known to exist in subsurface (?) [page 7] • Groundwater impacts: Estimate risk from both soil gas and groundwater data [page 8] • Soil matrix: Not recommended, unless soil gas samples cannot be collected due to low permeability conditions; only by Method 5035A [page 9] • Biodegradation: Consideration of zone of biodegradation [page 42]

21. California Interim Final Vapor Intrusion Guidance – Noteworthy Items • Indoor air screening criteria: SB32 CHHSLs [page 13] • OSHA PELs: Not appropriate, with exception of operating RCRA facilities [page 17] • Modeling: Parameters for existing and future residential and commercial buildings [Table 3] • Indoor air sampling: Option after modeling indicates possible indoor air risk; confounding factors [page 52] • Public outreach: Recommended for indoor air sampling [page 44] • Mitigation/engineering controls: Suggested alternatives [page 35]

22. Soil Vapor Intrusion Mitigation • Excavation • Sub Slab Depressurization Systems • Sub Slab Vapor Barrier Installation • Engineering Controls • Positive Pressure Ventilation • Increased Air Exchange Rates

23. Summary • Vapor intrusion is a hot topic for regulators on the federal, state, and local level • Soil gas sampling generally required as part of site characterization • Guidance is becoming more conservative; however, chemicals in indoor air may not be distinguishable from background • Key policy issues include regulatory inconsistency, background interferences, OSHA applicability, changing toxicity values (e.g., TCE, naphthalene) • Regulatory compliance is not always the driver - third party liability or redevelopment often drives vapor intrusion assessments

24. Future Trends • Collection of biodegradation parameters (O2, CO2) in soil gas and vertical profiling • Toxicity value adjustments leading to further more mitigation/remediation • Proactive installation of vapor removal/mitigation systems in lieu of sampling • Re-opening of No Further Action determinations (e.g., New York State DEC Draft Program Policy) and increased public awareness

25. Contact Us Rich Rago, Senior Scientist Haley & Aldrich 860.282.9400 rrago@haleyaldrich.com