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ESL - Environmental Screening Levels

Environmental Screening Levels
(Interim Final – December 2013)

The Environmental Screening Levels (ESL) document consists of a Microsoft Excel 2010 file (ESL Workbook), a User’s Guide (Screening for Environmental Concerns at Sites with Contaminated Soil and Groundwater), and Lookup Tables taken from the Excel file. This document is a technical report 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.

ESLs provide conservative screening levels for over 100 chemicals commonly 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).


The ESL Workbook is an Excel file and includes two parts: an Interactive Tool (formerly ESL Surfer) and Lookup Tables. The Interactive Tool allows users to input site-specific information and retrieve screening levels for the selected chemical and site scenario. Using the default (more conservative) inputs produces Tier 1 screening levels; using less conservative inputs produces Tier 2 screening levels. The Interactive Tool includes separate sheets for instructions, definitions, entry of the selected chemical and site-specific information, details on the resulting screening levels, and a summary of information on the chemical selected. The Lookup Tables provide the raw data used by the Interactive Tool. To use the ESL Workbook you must have Excel 2003 or later installed on your computer. Simply download the ESL Workbook from the link below then double click on the file to open the program.


The ESL User’s Guide describes how the ESL were derived and how they should (and should not) be used. The Lookup Tables from the Workbook are also provided in two PDF files.


The 2013 ESL updates make significant changes in vapor intrusion screening levels. Soil gas ESLs are revised to be consistent with DTSC’s vapor intrusion guidance and are generally about half the 2008 values. Groundwater ESLs for vapor intrusion are also about half the 2008 values, due to a somewhat more stringent indoor-air exchange rate based on DTSC guidance. Other notable changes are described in the Cover Memo (above).

The ESLs will be revised and updated on a regular basis. Updates will be posted to this website and electronic notifications sent to persons on the ESL mailing list. You can join the ESL mailing list by going to the Water Board’s website (or from the Water Board’s home page, click “Email Subscriptions”) once there, click on the ESL box under the General category.



BACKGROUND ARSENIC CONCENTRATIONS IN SOIL A master’s thesis completed in December 2011 presents the first regional estimate of background arsenic concentrations in the San Francisco Bay Region. The proposed upper estimate for background arsenic (99th percentile) within undifferentiated urbanized flatland soils is 11 mg/kg.

For further information about ESLs and risk assessment contact:


Ross Steenson
SF Bay Regional Water Quality Control Board
1515 Clay Street, Suite 1400
Oakland, CA 94612
Tel: 510-622-2445