Site Mitigation & Restoration Program

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

Vapor Intrusion

Public meetings for the Draft Supplemental Guidance: Screening and Evaluating Vapor Intrusion (Draft Guidance), originally scheduled in April 2020, were postponed due to the COVID 19 emergency and the Governor’s Executive Orders to protect public health by limiting public gatherings and requiring social distancing. To keep our stakeholders informed and engaged, the California Environmental Protection Agency (CalEPA) Vapor Intrusion Workgroup has developed and posted video presentations online and will host live Question and Answer Sessions in lieu of State-wide public meetings. The public comment period is extended to June 1, 2020. Additional information is provided below.

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.

To receive future notices, please subscribe to the DTSC Vapor Intrusion E-List (see description below).

Draft Supplemental Guidance: Screening and Evaluating Vapor Intrusion

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

February 14, 2020 Public Notice – February 2020 Draft Supplemental Guidance: Screening and Evaluating Vapor Intrusion [English / Spanish]

Revised – March 24, 2020 Public Notice – February 2020 Draft Supplemental Guidance: English / Spanish

New! May 4, 2020 Public Notice – Draft Supplemental Guidance – Video Presentations and Live Question and Answer Sessions [English / Spanish]

Video Presentations

A general overview and technical presentations on the Draft Supplemental Guidance are available in seven video presentations. The general overview presentation covers basic vapor intrusion information and provides an overview of the Draft Guidance. The technical presentations, provided in four modules, cover the Draft Guidance, the GeoTracker Database, and a case study. The video presentations, “Vapor Intrusion Workgroup – Presentations” are available at DTSC’s YouTube website:

New! Video Presentations – Draft Supplemental Guidance

Public Question and Answer (Q&A) Sessions – Webcast

The CalEPA Vapor Intrusion (VI) Workgroup will host live internet sessions for the public to ask questions on the YouTube video presentations, the Draft Guidance, and on vapor intrusion in general. The Q&A sessions will be held on May 14, 2020 and May 19, 2020. Participants should view the video presentations, described above, prior to the Q&A sessions.

Session dates and times, internet links for each session, information on BlueJeans video conferencing, call-in information, and information on submitting questions in advance are provided below and in the Public Notice [English / Spanish].

Two Q&A sessions will be held each day, as follows:

Afternoon Technical Session: Vapor intrusion practitioners are encouraged to attend this session to ask technical questions about the Draft Guidance and the technical video presentations provided on YouTube.

Early Evening Non-Technical, General Overview Session: This session is intended for the general public, non-technical stakeholders, and other interested parties to ask general questions about vapor intrusion and the Draft Guidance.

May 14, 2020:

Technical Q&A Session: 1:30 pm to 3:30 pm, Pacific Daylight Time (PDT)
General Overview Q&A Session: 6:00 pm to 8:00 pm, PDT

May 19, 2020:

Technical Q&A Session: 1:30 pm to 3:30 pm, PDT
General Overview Q&A Session: 6:00 pm to 8:00 pm, PDT

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.

Instructions: English / Spanish
Comment Form A (Adobe®): English / Spanish
Comment Form B (Microsoft® Word): English / Spanish

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

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

Flow Diagram of DTSC Documents
Advisory – Active Soil Gas Investigations (July 2015)
Frequently Asked Questions (FAQ’s) (August 2015)
Summary of Advisory Changes (2015)
Final Guidance for the Evaluation & Mitigation of Subsurface Vapor Intrusion to Indoor Air (October 2011; also known as the Vapor Intrusion Guidance)
DTSC’s Vapor Intrusion Guidance provides a stepwise and sometimes iterative process for the investigation of vapor intrusion and describes procedures for screening and site-specific evaluation of potential risks associated with this exposure pathway. The DTSC Screening-Level Model spreadsheets that used the Johnson & Ettinger (J&E) model to predict theoretical indoor air concentrations of contaminants from soil gas and groundwater data have been removed because they were not updated and are not based on the most current J&E model spreadsheet tool from USEPA.
Summary of Changes Between Interim Final and Final Guidance
Human Health Risk
Archived Screening-Level Model for Soil Gas Contamination
Archived Screening-Level Model for Groundwater Contamination
Vapor Intrusion Public Participation Advisory (March 2012)
DTSC developed this Advisory to help determine and implement appropriate public participation coordination and activities at sites where a potential vapor intrusion risk has been identified. The Advisory is a companion document to DTSC’s Vapor Intrusion Guidance and Vapor Intrusion Mitigation Advisory. In addition, the Advisory supplements DTSC’s Public Participation and Procedures Manual.
Vapor Intrusion: Decision Framework for Testing Indoor Air & Overview of Sampling Procedures Presented at the February 2012 CUPA Conference
Vapor Intrusion Mitigation Advisory, Revision 1 (October 2011)
Provides a framework that guides the reader through the decision process for 1) determining if mitigation is appropriate for the project site, 2) selecting a mitigation system that is protective of human health, and 3) ensuring that implementation is sustainable for the duration of mitigation. Emphasizes public participation and implementation considerations. Identifies likely technologies for vapor intrusion mitigation, but does not identify proven technologies.
Summary of Changes Reflected in Revision 1