The vapor intrusion (VI) regulatory landscape in Michigan has been in flux for some time. The Michigan Department of Environment, Great Lakes, and Energy (EGLE) promoted its presentation of April 29, 2021 as providing clarity to the VI regulatory standards. After viewing the presentation, it did provide clarity, not necessarily of the statute or rules, but clarity in EGLE’s view and implementation of the statute and rules.
No Exits
EGLE’s presentation discussed various screening levels including Volatilization to Indoor Air Pathway Screening levels (VIAP SLs), Recommended Interim Action Screening Levels (RIASLs), and Media-Specific Volatilization to Indoor Air Screening levels (MSSLs). EGLE discussed the specific purposes of these various screening levels but spent more time on their limitations. Our takeaway is that these “screening levels” bring you into a VIAP maze with all the associated obligations and costs. Finding an exit to the maze is a much more difficult proposition.
Narrow Application
Currently, the only regulatory enforceable criteria for VI are the Part 201 Generic Cleanup Criteria (GCC) for soil and groundwater, specifically the Soil Volatilization to Indoor Air Inhalation (SVIIC) and the Groundwater Volatilization to Indoor Air Inhalation (GVIIC). However, there are specific assumptions built into the GCCs that preclude their application in NEARLY ALL situations. If the assumptions are not met, the Part 201 regulation requires that a “site-specific” evaluation be performed to evaluate vapor intrusion risk. The GCC assumptions include the depth to groundwater and specific construction details for the building.
If site conditions indicate the potential for the VIAP exposure, the VIAP SLs can be compared to soil vapor concentrations to evaluate the VIAP risk. The VIAP SLs are a “first cut” evaluation.
If you are assessing vapor intrusion (or planning to assess vapor intrusion), we strongly encourage you to have a strategy meeting with your technical and legal advisors to avoid unnecessary expenses (Image Credit: Dragun Corporation).
Site-Specific Evaluation
For sites that don’t meet the VIAP SLs assumptions, site-specific evaluation is required. The site-specific evaluation includes summarizing building construction, subsurface soil, and groundwater conditions. The resultant information is typically submitted to EGLE who perform a site-specific calculation using their computer model. The computer model data provides site-specific soil vapor concentrations that should not be exceeded. It provides a basis for determining if further investigation or VI mitigation and/or remediation is required.
VI Screening Levels Not Applicable for Compliance
EGLE has published additional screening levels, the RIASLs and MSSLs, which are used to determine the need and timing for VIAP mitigation (typically called an interim response action). If a RIASL or MSSL is exceeded, EGLE will require the site owner to perform mitigation according to a schedule. However, EGLE does not allow the RIASLs and MSSLs to be used for determining regulatory compliance.
Part 201
Interestingly, EGLE’s presentation did not discuss section 20120f of Part 201, which addresses evaluation of the VIAP using indoor air testing. EGLE’s only mention of indoor air testing is that it can’t be used because they do not have authority to develop indoor air criteria. This situation has been anticipated under 20120f (1) (d) wherein alternate criteria are allowable (i.e. USEPA VISLs) if specific criteria have not been developed.
Conclusion
We have learned a lot about the science of vapor intrusion over the years and have many tools available to scientifically evaluate and mitigate potential vapor intrusion concerns. We are concerned that EGLE is hesitant to use many of these tools that lead to scientifically sound, rational, and cost-effective vapor intrusion solutions that are good for human health, the environment, and business.
If you are not familiar with vapor intrusion, see this ~ 5-minute video.
Strategy with respect to vapor intrusion has never been more important. If you would like to discuss strategies with respect to your project, contact Jeff Bolin, Matt Schroeder, or Mark Resch at 248-932-0228.