MDEQ has proposed to use a new tiered process for vapor intrusion, as recommended by the CSA. The Soil and Groundwater Volatilization to Indoor Air Criteria (SVIIC or GVIIC) in the 2013 rules are replaced by the Volatilization to Indoor Air Screening Levels and Criteria in the proposed rules. The proposed Volatilization to Indoor Air Screening Levels and Criteria protect for chronic exposures, in general, but also protect for acute toxicity for those volatile hazardous substances that have short-term health effects .
The tiered approach will reduce the number of site-specific evaluations that require a Department review by providing “off-ramps” at each tier:
VI Tier 1:
- Initial generic screening levels.
- Exceedances do not result in facility status, and DEQ will not use this Tier to require remedial action.
- If exceeded, further assessment through the tiered process is needed.
VI Tier 2:
- Incorporates facility-specific geologic and hydrogeological conditions
- Compliance with VI Tier 2 criteria results in unrestricted residential closure.
- Exceedances result in facility status.
VI Tier 3A:
- Incorporates land use and building-specific information for generic criteria.
- Identifies the need for response activity or a site-specific evaluation completed in VI Tier 3B.
VI Tier 3B:
- Site-specific alternative approach.
- Requires Department approval to implement.
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