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Notice of Public Workshop and Opportunity for Comment, on Maine DEP Guidance
The Maine Department of Environmental Protection (DEP) is providing a 30-day public comment period and holding a public workshop on proposed revisions to its Supplemental Guidance for Vapor Intrusion (VI) of Chlorinated Solvents and other Persistent Chemicals. The guidelines are for the investigation and mitigation of risks potentially posed by vapors intruding into living spaces from subsurface chemical releases. DEP’s proposed guidelines are intended to supplement the United States Environmental Protection Agency’s (EPA) recently published guidance, “Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface to Indoor Air” (June, 2015). The EPA guidance focused on large, complex VI sites, which are rare in Maine. The proposed DEP supplement offers reasonable, cost-effective alternative approaches to sites with 10 or fewer inhabitable buildings at risk. Both guidances apply to sites with subsurface chlorinated solvents or similarly persistent and volatile chemicals. VI from chemicals that decay relatively rapidly in the subsurface, such as petroleum compounds, are not within the scope of the proposed DEP guidance, nor is VI risk from polychlorinated biphenyls (PCBs), hydrogen sulfide, and elemental mercury. The guidance recognizes that VI science is rapidly evolving, and recommends using multiple lines of evidence and a concise conceptual site model to make risk-based decisions.
The proposed guidelines will supersede DEP’s Vapor Intrusion Evaluation Guidance of 2010, which will be retracted. The proposed guidelines will also alter the VI portions of the 2013 Maine Remedial Action Guidelines for Sites Contaminated with Hazardous Substances (RAGS). The specific portions of the RAGs proposed for alteration are shown with revision marks in a document that can be obtained at the link below.
Maine DEP is also providing a 30-day public comment period and holding a public workshop on proposed revisions to guidelines for chemical and media specific clean-up levels to prevent long-term risks that could be posed to public health from a chemical release. The Maine Remedial Action Guidelines for Sites Contaminated with Hazardous Substances (RAGS) were last revised in 2013, and in a revision proceeding parallel to this one, are proposed to be updated for changes in Vapor Intrusion approaches. While the RAGs are under revision for VI, the DEP is soliciting comments on updates in two other areas where science has advanced since the last RAG revision. DEP is proposing to:
See DEP Opportunity for Comment page for copies of draft guidance: http://www.maine.gov/dep/comment/comment.html?id=654109