California State Water Board Announces Scoping Phase for New Vapor Intrusion Cleanup Requirement

On March 25, 2022, the California State Water Resources Control Board (State Water Board) issued a notice of public scoping meeting for a proposed amendment to its rules governing site cleanup. This amendment would establish “requirements for the investigation and assessment of vapor intrusion at cleanup sites statewide.”

In recent years, vapor intrusion guidance in California has been in limbo. In February 2020, the Department of Toxic Substances Control and other state agencies issued draft supplemental guidance to modify previous vapor intrusion guidance issued in 2011. One key change in the 2020 draft supplemental guidance involved the attenuation factors to be applied to site sampling results when evaluating potentially harmful vapor intrusion into buildings. The 2020 draft supplemental guidance increased the stringency of the attenuation factor to be applied, setting a 0.03 factor to be applied uniformly for screening all buildings regardless of usage. This draft supplemental guidance still has not been finalized, which has raised concerns regarding the standards for evaluating and remediating vapor intrusion. In many instances during cleanup or redevelopment, the effect is that the more stringent attenuation factor is applied — often at greatly increased cost.

The State Water Board now proposes to insert its own standard into the mix. As described in the recently issued notice, the State Water Board’s proposal seeks to address “case-by-case” vapor intrusion assessments and indicates that the State Water Board seeks uniformity in the standard to be applied in these assessments. The notice further describes that the proposed amendment “would establish state policy for water quality control that requires the use of an expeditious, consistent, and protective approach using statewide data for assessing vapor intrusion risk.”

At this point, as only a scoping meeting has been proposed, all of the details of the State Water Board’s proposed amendment are not yet available. Given the descriptions in the notice, the State Water Board may be considering setting its own attenuation factor for cleanups within its purview. This could affect sites throughout California, potentially with substantial cost effects for cleanup and redevelopment projects.

The two scoping meetings, at which the State Water Board will receive feedback on its proposal, are scheduled to occur by videoconference on April 28, 2022. The State Water Board is also accepting written comments until noon on May 9, 2022.

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