The vapor intrusion (VI) regulations throughout the United States have been under an almost continuous process of revision. Evaluation of the VI pathway in Michigan has been a topic of discussion for years. The regulated community including trade groups such as the Michigan Manufacturers Association, Michigan Chemistry Council, Michigan Chamber of Commerce, and Michigan Petroleum Association to name a few have weighed in on VI regulations as implemented by the Michigan Department of Environment, Great Lakes, and Energy (EGLE).
The heart of the VI discussion boils down to “How much testing is enough?” Further complicating the VI issue is what type of testing (i.e. soil vapor, sub-slab vapor, and/or indoor air) should be conducted and what constitutes an off-ramp or closure?
EGLE Attempts to Streamline the VI Process for Petroleum Releases
Currently, EGLE is evaluating the VI process and recently provided updated guidance to streamline the VI investigation process for petroleum releases. EGLE plans to further define the VI process and procedures. These “streamlining” efforts appear to be more intent on accommodating regulatory deadlines within Part 213 of Public Act 451 (Leaking Underground Storage Tanks) than actually providing off-ramps and closure.
EGLE’s Petroleum Vapor Intrusion Checklists
EGLE’s new guidance consists of two checklists for determining if there is “sufficient” horizontal and vertical isolation distance between a below-ground location of petroleum contamination and a building or property border.
- Precluding Factors Assessment for Petroleum Vapor Intrusion (PVI) Lateral Inclusion Zone.
- Precluding Factors Assessment for Petroleum Vapor Intrusion (PVI) Vertical Separation Distance.
In general, if certain factors are not present (e.g., no ongoing release of petroleum, no utilities going through contamination that also extend to a building, etc.) then VI remedial actions are not required for a building if the petroleum plume is more than 30 feet horizontally away from a building. While this is simplistically presented in the EGLE guidance, our experience has been that this is a more difficult hurdle than it would appear.
Evaluating the vapor intrusion (VI) pathway is increasingly important and in Michigan, becoming more complex (Photo from Dragun project site).
Petroleum Plume Below a Building
Where the petroleum plume is below the building, and depending upon site conditions, the petroleum plume must be a minimum of 5 feet below the lowest point of the building.
EGLE’s guidance/checklists contain information to verify the site conditions are appropriate for the use of the isolation distances. Examples include meeting the horizontal isolation distance requirements and having 5 feet of clean soil between the base of a building and the contaminated soil or dissolved groundwater plume. If there is a non-aqueous phase liquid (NAPL) plume, an isolation distance of 15 feet of clean soil between the base of a building and the NAPL plume is required.
More Changes for VI in Michigan Anticipated
At a recent Michigan Manufacturers Association meeting, EGLE representative Mr. Josh Mosher indicated EGLE is developing distinct and separate procedures for VI evaluations with respect to petroleum and non-petroleum releases (e.g. chlorinated solvents like trichloroethylene). The new procedures have reportedly been drafted and are undergoing internal EGLE evaluation. EGLE has not provided a date for the dissemination of the procedural documents. As we understand, we may see something this summer.
The VI pathway continues to be a significant factor when evaluating sites/closing sites in Michigan and elsewhere. We continue to monitor the VI developments in Michigan and will share these changes in our blogs and newsletters. Also see our Vapor Intrusion Reference Guide: State by State. This short video provides a primer on vapor intrusion.
This blog was drafted by Mark Resch. Mark has an undergraduate degree in the geological sciences and is a senior environmental scientist at Dragun Corporation. He brings over 30 years of environmental consulting experience in vapor intrusion, groundwater investigation, site assessment, and environmental construction project management. See Mark’s Bio.
The blog was reviewed by Jeffrey Bolin, M.S. Jeff is a partner and senior scientist at Dragun Corporation. He is a published author, frequent speaker, and expert witness. His expertise in environmental due diligence, PFAS, vapor intrusion, and site assessments has led to projects in the US, Canada, and overseas. See Jeff’s Bio.
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