US EPA has finally released draft guidance documents for assessing and mitigating vapor intrusion risks from chlorinated solvents and petroleum contamination – documents that many industry analysts believe will likely result in stricter clean up and monitoring requirements at contaminated sites and add more sites to the Superfund list.
Officials appear to have dropped prior draft language from its chlorinated solvents guide for calculating limits to protect against health hazards from short-term exposure to toxic levels of contamination in indoor air, an issue that officials have long been struggling to address. EPA also appears to have reduced its recommended clean-up standard for the amount of clean soil that the agency deems necessary to protect buildings overlying petroleum contamination, reducing the “separation distance” in half from 30 feet to 15 feet.
Vapor intrusion occurs when vapors rise from contamination below ground into buildings through dirt floors, utility line openings, or other pathways. EPA generally did not account for such exposure pathways when it crafted its waste clean-up programs in the 1980s and 1990s, but subsequent research showed potential risks – forcing the agency to develop screening and other assessment methods.
The agency has struggled to craft guidance and other policies to address the issue, leaving many states and businesses to use conservative models for estimating risks of vapor intrusion. The effort to develop guidance accelerated after an Inspector General’s report in 2009 recommended EPA create a separate guidance to address vapor intrusion from petroleum contamination and that failure to complete the guidance was costing EPA leadership on the issue.
In addition to the two guidance documents, EPA is also working to develop a rule allowing contaminated sites to be listed on the Superfund National Priorities List (NPL) based solely on potential exposure to vapor intrusion, though the measure’s fate is uncertain due to strong industry opposition. Late in 2012, US EPA issued guidance requiring regional officials to ensure when conducting mandatory five-year reviews that remedies at sites already listed on the NPL, adequately address risks of vapor intrusion and are protective.
An industry source criticizes the new requirement claiming that it will likely force an assessment of the adequacy of remedies at scores of sites where clean-up plans were already selected or even constructed and could force additional clean-up requirements.
EPA will accept public comment on the guidance documents until May 24 at regulations.gov (EPA-HQ-RCRA-2002-0033).
For more information or for assistance with assessing and mitigating vapor intrusion risks from chlorinated solvents and petroleum contamination, contact Principal Geoscientist Gerry Kirkpatrick, P.G. at 610-935-5577.