Big Changes from the SF Bay Water Board: New Environmental Screening Levels (ESLs) Released
Big changes are flowing in from the San Francisco Bay Regional Water Quality Control Board (Water Board) with the release of updated Environmental Screening Levels (ESLs)—and if you’re involved in site investigations, cleanups, or property transactions, this is news you’ll want to pay attention to. We’re here to break down what’s new and how it might impact your projects.
Major Updates to Environmental Screening Levels (ESLs)
As of July 2025, the San Francisco Water Board has released a major update to its Environmental Screening Levels. This comprehensive revision is designed to improve environmental risk assessments by incorporating the latest science, refining tools, and providing more streamlined guidance for practitioners.
The updates include:
- A revised ESL Workbook
- Updated summary tables
- An expanded User’s Guide
These tools are intended to better support environmental professionals in evaluating and managing contaminated sites.
What’s New? A Quick Look:
A major focus of this update is the expansion of ESLs related to per- and polyfluoroalkyl substances (PFAS). ESLs for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) have been updated, and 14 additional PFAS compounds have been added to the ESL framework.
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The current list now includes the following 16 PFAS compounds:
- Perfluoropropanoic acid (PFPrA)
- Perfluorobutanoic acid (PFBA)
- Perfluoropentanoic acid (PFPeA)
- Perfluorohexanoic acid (PFHxA)
- Perfluoroheptanoic acid (PFHpA)
- Perfluorooctanoic acid (PFOA)
- Perfluorononanoic acid (PFNA)
- Perfluorodecanoic acid (PFDA)
- Perfluoroundecanoic acid (PFUDA)
- Perfluorododecanoic acid (PFDoDA)
- Perfluorotetradecanoic acid (PFTeDA)
- Perfluorooctadecanoic acid (PFODA)
- Perfluorobutane sulfonic acid (PFBS)
- Perfluorohexane sulfonic acid (PFHxS)
- Perfluorooctane sulfonic acid (PFOS)
- Hexafluoropropylene oxide dimer acid (HFPO-DA)
You can view the updated ESL tables here.
More Key Changes to Know
In addition to the expanded PFAS list, here are a few other important updates:
- New toxicity values have been introduced for human health risk assessments.
- Updated input values now apply to aquatic habitat considerations.
- Petroleum hydrocarbon fractions have been revised to reflect current data.
- Soil leaching tools now include all modern leaching scenarios, and Table S-4 has been updated accordingly.
- New short-term exposure levels for elemental mercury have been added.
Notably, there were no changes to two commonly referenced Tier 1 ESLs:
- Tetrachloroethene (PCE)
- Trichloroethene (TCE)
These contaminants remain key concerns in soil, groundwater, soil vapor, and air investigations.
Need More Info?
For detailed guidance or to download the latest materials, visit the SFBRWQCB Site Cleanup Program or contact the Board directly at RB2-ESLs@waterboards.ca.gov.
And of course, the team at McAlister GeoScience is here to help you navigate these changes and support your Environmental Site Assessment (ESA) needs.
References
-
San Francisco Bay Regional Water Quality Control Board
Environmental Screening Levels (ESLs)
https://www.waterboards.ca.gov/sanfranciscobay/water_issues/programs/esl.html
Accessed July 2025.
– Includes the updated ESL Workbook, Summary Tables, and User’s Guide for environmental risk screening. -
California State Water Resources Control Board
Site Cleanup Program Overview
https://www.waterboards.ca.gov/water_issues/programs/site_cleanup_program/
– General information about the State’s site investigation and cleanup programs. -
United States Environmental Protection Agency (EPA)
PFAS Explained
https://www.epa.gov/pfas
– Comprehensive background on per- and polyfluoroalkyl substances (PFAS), including health effects, regulation, and scientific resources.