California has proposed new statewide vapor intrusion guidance that will make an already aggressive approach to regulation and management even more rigorous. If the guidance in its current form is finalized, it will mean more conservative screening levels, more extensive sampling at sites, and may ultimately lead to more cleanup and mitigation required and at more sites.
Prospective purchasers and lessees of commercial property in California should look closely at vapor intrusion issues early during due diligence. Understanding the potential costs that more aggressive screening and mitigation may add to a project—and devising a smart strategy to minimize those costs—will be key to a project's profitability.
Vapor intrusion occurs when toxic vapors move from contaminated groundwater and soil, intrude into a building, and impact indoor air quality. Vapor finds its way indoors through a variety of pathways, such as cracks in foundations and basements, sewers, drain lines, access vaults, and any other opening in a building envelope. Vapor migration is influenced by climate, building conditions, HVAC operation, and other natural and human-caused factors.
To address increasing concern regarding vapor intrusion, California Environmental Protection Agency, the Department of Toxic Substances Control (DTSC), the State Water Resources Control Board, and the San Francisco Bay Regional Water Quality Control Board issued draft supplemental vapor intrusion guidance—Draft Supplemental Guidance: Screening and Evaluating Vapor Intrusion. It is intended to promote state-wide standard practice and consistency for screening buildings for vapor intrusion. This supplements existing information and should be used in tandem with DTSC 2011 Vapor Intrusion Guidance and San Francisco Bay Regional Water Board 2014 Interim Framework.
The draft supplemental guidance provides information and recommendations concerning factors that influence how quickly contamination attenuates over time. It establishes a standardized evaluation process for determining whether vapor intrusion is likely to affect buildings located near a contamination source, and considers sewers located underneath buildings potential pathways for vapor to intrude into buildings.
A final revised proposal is expected by late fall or winter. Additional policies or regulations related to the guidance are likely forthcoming but will require separate rulemakings or proceedings.
With this new vapor intrusion guidance, California once again finds itself pushing the envelope on environmental regulation. Property owners and developers will be watching closely to see if other states follow will suit.
Holland & Hart law clerk Bret Huffaker also contributed to this article.