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Lower Screening Levels Call for Higher Levels of Due Diligence

Updated: Feb 2, 2022

By Beth Koh (May 6, 2019)

At a recent Alameda County Bar Association event spotlighting Bay Area environmental regulators, invited guests were polled on the hot topic in their respective areas of regulation. The most-repeated answer: vapor intrusion.

With the updating at the beginning of this year of environmental screening levels (ESLs) by the San Francisco Regional Water Quality Control Board, and anticipated guidance on vapor intrusion investigations to be released soon, vapor intrusion is indeed a topic of heightened concern.

For property transactions, the lower ESLs for soil vapor for such chemicals as trichloroethylene (TCE) and tetrachloroethylene (PCE) will have an effect on the level of environmental due diligence you will want to conduct for a particular site. For example, how does a site’s potential “Historical Recognized Environmental Condition” (HREC) stand up against these new ESLs? The ASTM standard recognizes an HREC as a prior release remediated or addressed to the satisfaction of a regulatory agency without being subject to further controls (e.g., maintenance, engineering, or use restrictions). But sites are being re-evaluated – and could be re-opened – due to more strict screening levels. So even if a particular condition might not quality as an HREC or (current) recognized environmental condition under the ASTM standard, it might be prudent to assess whether site-specific information could trigger a re-opening. Under the newly expanded regulation of vapor intrusion, due diligence should include a closer examination of sites where you may have been in the clear before.


Beth Koh is Of Counsel at Environmental General Counsel. She handles a wide range of environmental and health and safety matters, including Prop 65.

The opinions expressed are those of the author and do not necessarily reflect the views of the firm, its clients, or any of its or their respective affiliates. This article is for general information purposes and is not intended to be and should not be taken as legal advice.

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