The Indoor Inhalation Exposure Route Heather Nifong Illinois EPA May 5, 2008

Risk-Based Cleanup for Vapor Intrusion in Illinois Began developing approach in early 2006 Builds on work of U.S. EPA and several states Uses existing three-tiered approach in place for other exposure routes (TACO) Reviewed by the Site Remediation Advisory Committee (a legislatively mandated stakeholder group)

Risk-Based Cleanup for Vapor Intrusion in Illinois Remediation objectives (ROs) developed by applying a modified Johnson and Ettinger model to calculate attenuation factor and perform equilibrium conversions. ROs available for volatile chemicals in soil gas, soil and groundwater; choice of residential or industrial/commercial land use. If demonstrate compliance with (1) soil gas or (2) soil and groundwater, then site’s okay.

Risk-Based Cleanup for Vapor Intrusion in Illinois The indoor inhalation route may be excluded if: Volatile chemicals are not present, Existing or potential buildings and man-made pathways are not, and will not be, located over contaminated areas, or An approved building control technology (BCT) is in place and operational.

Challenges Use of soil gas data Selection of building-specific default parameters Design criteria for BCTs Effect on formerly remediated sites

Use of Soil Gas Data Initially resisted calculation of soil gas ROs Limited use at current sites No standardized sampling protocol Risk-based cleanup regulations traditionally avoid site characterization requirements so as not to interfere with individual programs (LUST, VCP, RCRA)

Selection of Building-Specific Default Parameters Less flexibility in Tier 2 than anticipated Wanted to prevent excessive institutional control requirements Fixed parameters for building height, width and length; air exchange rate; slab thickness, etc. Do allow for distinctions between slab-on- grade and basements, residential and industrial-commercial

Design Criteria for BCTs Should active mitigation systems qualify for No Further Remediation Letters? (yes) What about buildings not yet constructed? (approved BCT in place and operational prior to human occupancy) How detailed should the institutional control be? (o & m requirements, provisions for inoperability)

Effect on Formerly Remediated Sites Closed sites will not be re-opened – unless new site-specific information indicates a indoor inhalation problem Sites active at the time the rules take effect will have to account for the indoor inhalation exposure route, regardless of their progress toward cleanup

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