Site Mitigation & Restoration Program

We protect and maintain California’s land and places
by setting strict standards for land restoration and cleanup

Vapor Intrusion

Draft Supplemental Guidance: Screening and Evaluating Vapor Intrusion

Due to the COVID-19 public health emergency, the public comment period is extended to June 1, 2020, and the original public information meetings scheduled for April 2020 are postponed until further notice. DTSC and the Water Boards are committed to protecting public health, and the uncertainty surrounding transmission of the COVID-19 virus and the known effects on vulnerable populations in our community warrant exercising extreme caution.

The Department of Toxic Substances Control (DTSC), State Water Resources Control Board, and San Francisco Bay Regional Water Quality Control Board have developed supplemental vapor intrusion guidance for conducting vapor intrusion evaluations in California.

The Draft Supplemental Guidance: Screening and Evaluating Vapor Intrusion was released for review and public comment on February 14, 2020. As stated above, the comment period is extended to 12:00 noon on June 1, 2020.

Public meetings are postponed until further notice. To receive future notices, please subscribe to the DTSC Vapor Intrusion E-List (see description and link, below).


The Draft Supplemental Guidance provides information on the following topics:

  • Soil gas, subslab, indoor air, and outdoor air sampling recommendations that are focused on understanding spatial and temporal variability
  • Recommendations for use of USEPA 2015 vapor intrusion attenuation factors
  • Risk management framework for vapor intrusion
  • California-specific vapor intrusion database in Geotracker

New! February 2020 – Draft Supplemental Guidance: Screening and Evaluating Vapor Intrusion

New! Executive Summary Fact Sheet: English / Spanish

Revised Public Notice – February 2020 Draft Supplemental Guidance: English / Spanish

Public Information Meetings and Webinar Locations

Postponed until further notice.

Public Comments

Comments on the Draft Guidance may be submitted electronically or by mail using one of the Comment Forms provided or by letter. Please see Instructions below for information on how to submit comments.

Mail to:

State Water Resources Control Board, Division of Water Quality,
CalEPA VI Workgroup, Attention: Abe Waggoner,
1001 I Street, 15th Floor, Sacramento, CA 95814

OR

Email to: DWQ-vaporintrusion@waterboards.ca.gov

Vapor Intrusion Fact Sheet

New! Vapor Intrusion and Your Health Fact Sheet (general overview of vapor intrusion): English / Spanish

Vapor Intrusion E-List

Subscribers will receive e-mail notifications regarding news on topics relevant to vapor intrusion—the migration of volatile contaminants through soil and into buildings and potentially causing unacceptable chemical exposure for building occupants. Topics include subsurface investigations and evaluation of potential exposure and human health risk from vapor intrusion.

Subscribe to DTSC Vapor Intrusion E-List.

Vapor Intrusion Guidance Documents

Other Vapor Intrusion Resources