Demonstrating compliance with the vapor intrusion pathway for acute vapor hazards at leaking underground storage sites in Michigan may now be less work. The Michigan Department of Environment, Great Lakes, and Energy (EGLE) recently determined that potential risks from acute petroleum hydrocarbons at leaking underground storage tank sites can be evaluated the same as other hydrocarbons at those sites.

In 2021, EGLE released an addendum to its 2013 Vapor Intrusion Guidance Document for acute vapor hazards associated with petroleum releases. That addendum was intended to assist liable parties in demonstrating compliance with Section 21307 of Michigan’s Natural Resources and Environmental Protection Act.

Section 21307 requires acute vapor hazards associated with a release from an underground storage tank system to be evaluated. Based on EGLE’s evaluation of data from over 90 petroleum-contaminated sites, EGLE concluded that the likelihood of an acute indoor air exposure from a petroleum hydrocarbon is extremely low. And based on that evaluation, EGLE has determined the sampling plan outlined in the 2021 addendum is unnecessary.

Rescinding the 2021 addendum should allow for a more consistent and uniform approach to addressing the vapor intrusion pathway at leaking underground storage tank sites in Michigan. Going forward, the potential risks from acute petroleum hydrocarbons can be treated the same as other hydrocarbons, which should eliminate the need for the rigorous sampling plans that were called for under the addendum.