Environmental Screening Levels

Environmental Screening Levels

The Environmental Screening Levels (ESLs) provide conservative screening levels for over 100 chemicals found at sites with contaminated soil and groundwater. They are intended to help expedite the identification and evaluation of potential environmental concerns at contaminated sites. ESLs address a range of media (soil, groundwater, soil gas, and indoor air) and a range of concerns (e.g., impacts to drinking water, vapor intrusion, and impacts to aquatic life). These ESL documents are prepared by staff of the San Francisco Bay Regional Water Quality Board (Water Board). Information provided in the document is not intended to establish policy or regulation. Also note that, in general, ESLs are not used at sites that are subject to the Low-Threat Underground Storage Tank Closure Policy.

Contents and Update Process

Environmental Screening Levels (ESLs) Content

Update Process

Major updates and minor revisions to the ESLs will be posted to this website when needed. The current major update (e.g., Feb 2016) and minor revision (e.g., Rev #) version is listed on the top of the Table Index and in the footer of each sheet within the ESL Workbook. The following link (ESL Status Sheet) provides the current revision number and lists the most recent changes for that revision.

Electronic Mailing List for Updates

When ESLs are updated or revised, we send an email notification to those are on the ESL mailing list. You can join the ESL mailing list by clicking the link below. Once there, check the ESL box under the General category. 

San Francisco Region 2 – Email Subscription Form

Vapor Intrusion Updates

The State Water Resources Control Board, the San Francisco Bay Regional Water Quality Control Board, and the Department of Toxic Substances Control (DTSC), are currently developing a supplemental vapor intrusion guidance document for conducting uniform vapor intrusion evaluations in California. This guidance document will serve as a 2018 Supplement to existing guidance documents. This guidance will provide information on the following topics:

  • Soil gas, subslab, indoor air, and outdoor air sampling recommendations that are focused on understanding spatial and temporal variability
  • Sewers as a potential migration route and pathway of exposure
  • Recommendations for use of USEPA 2015 attenuation factors to screen buildings
  • Risk management framework for vapor intrusion
  • California-specific vapor intrusion database

The Supplemental VI guidance is anticipated for release to the public in mid-2018. Following release, DTSC and the Water Boards will hold public workshops likely in Northern and Southern California. Actual dates will follow once the document is completed. Click here to view a presentation with updates on the supplemental vapor intrusion guidance document prepared for the November 2017 Groundwater Resources Association Dry Cleaner Conference.

Technical Resources




For further information about ESLs and risk assessment contact:
  • Nicole Fry
    SF Bay Regional Water Quality Control Board
    1515 Clay Street, Suite 1400
    Oakland, CA 94612
    Tel: 510-622-5047
    Email: ESLs.ESLs@waterboards.ca.gov