As part of efforts to update the state's 20-year-old toxics cleanup law, the Washington State Department of Ecology (Ecology) is seeking public comment on vapor intrusion cleanup requirements for contaminated sites.
Vapor intrusion is the release of gaseous chemicals from the ground, which can significantly impact the indoor air quality of overlying buildings. Certain contaminants can move as vapors travel through soil from groundwater or subsurface and enter ground-level structures.
According to a statement issued by Ecology in July, the current regulations are unclear about the requirements for assessment of the vapor intrusion pathway, which is not typically evaluated unless certain triggering criteria are met.
Washington State's Model Toxics Control Act (MTCA) establishes administrative procedures for environmental cleanup of sites contaminated with hazardous material. MTCA governs the cleanup of contamination in various mediums, including groundwater, soil and air.
Although the current regulations include a general requirement that cleanup levels for a specific media do not cause violations of cleanup levels for other mediums, the regulations lack specifics. To add clarity, Ecology is considering establishing new standards for subsurface media cleanup that would protect indoor air quality from vapor intrusion.
Other statutory ambiguities in MTCA involving vapor intrusion include the lack of definitions for vapor intrustion or soil gas and its failure to state whether the vapor intrusion pathway needs to be investigated during the remedial investigation.
MTCA's lack of specificity has left regulators and developers alike uncertain about their obligations under state law. Comments gathered will be used to determine whether rule changes are needed to deal with the statutory ambiguity in MTCA and other vapor intrusion problems. A draft guidance document will be issued in early 2010 to aid in the broader MTCA revision rulemaking process, currently scheduled for completion in 2011.
To comment, email martha.hankins@ecy.wa.gov and include "VI Guidance" in the subject line. The comment period closes Nov. 30 at 5:00 p.m.
