1. Overview of US EPA’s Vapor Intrusion Guidance VAP CP Summer Coffee July 14 th, 2015 Carrie Rasik Ohio EPA CO- Risk Assessor Carrie.Rasik@epa.ohio.gov

2. US EPA’s Vapor Intrusion Guidance OSWER Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air Finalized June 2015 Replaces 2002 OSWER “Draft VI Guidance” http://www.epa.gov/oswer/vaporintrusion/

4. Document Highlights Multiple Lines of Evidence Spatial and Temporal Variability Sampling Considerations VI Chemicals of Potential Concerns VISL Calculator Revised Attenuation Factors

5. Multiple Lines of Evidence Site history, pathway completeness, media data, hydrologic and geologic information, VISL comparison, etc. Reduces false-negative/positive conclusions Greater confidence

6. Spatial and Temporal Variability Hourly, Daily, Seasonally, Buildings – “Field observations and measurements demonstrate that indoor air concentrations can exhibit significant temporal variation within a day and between days and seasons in an individual residential building (EPA 2012a; Holton et al. 2013ab)” – “Field experience indicates there may be substantial spatial variability in sub-slab soil gas concentrations even over an average-sized footprint of a residential building (EPA 2015) Can span at least an order of magnitude and often more Keep in mind when trying to determine “representative” or “reasonable worst case” exposure scenario

7. Spatial and Temporal Variability: Some Examples (not an inclusive list) Depth to groundwater Heterogeneities in the subsurface materials Weather conditions Building operations Building construction and age Interior compartmentalization Adventitious openings Developed vs undeveloped (advection)

8. Sampling Considerations at a Glance Several rounds at multiple locations – “an individual sample (or single round of sampling) would be insufficient to characterize seasonal variability, or variability at any other time scale (EPA 2015) Bulk soil not recommended quantitatively Soil gas survey – Multiple depth intervals between source and building(s), including immediately above vadose zone source – If collecting shallow- collect close to building, at depths below the respective building foundation, and no less than five feet below ground surface, depending on site-specific conditions “Near-Source” soil gas – Very useful at undeveloped properties

9. More Sampling Considerations at a Glance Sub-slab sampling – Typically 3 sub-slab samples at buildings < 1,500 sq ft – Include central locations – Measure pressure difference Indoor Air – Building survey – Time-integrated samples – Paired with sub-slab and ambient – Useful to support mitigation/remediation systems

10. VI Contaminants of Potential Concern Known or reasonably expected COPCs from a release Change in “volatile”: toxicity + Henry’s Law constant OR Vapor Pressure – Henry’s Law Constant > 10^-5 atm m^3 mol-1); OR – Vapor pressure > 1 mm Hg Current chemical list on VISL

11. Vapor Intrusion Screening Level (VISL) Calculator Excel spreadsheet List of volatile and toxic chemicals Medium-specific, risk-based target concentrations – indoor air – sub-slab/“near-source” soil gas – groundwater Derive risk/hazard from media concentrations Estimates indoor air concentrations C/I and residential scenarios Groundwater temperature adjustment Frequent toxicity data updates http://www.epa.gov/oswer/vaporintrusion/guidance.html

12. Attenuation Factors

13. Other Items of Note EPA does not recommend using OSHA PELs/TLVs Lateral inclusion zone of 100 feet Reasonable maximum exposure ICs/mitigation measures in conjunction with source remediation Cis-1,2-DCE as indicator

14. Implications on Ohio EPA DERR VI Guidance J&E Model? VISL additions from “volatile” change? Specific sampling frequency? Petroleum-Only Releases Separate Guidance? Others VAP staff will be discussing in the near future US EPA’s Guidance document and it’s implications on Ohio EPA’s document

15. Thank You!