Publications Home || Browse by topic || Browse by program || Ecology website

Publication Summary

Our Ecology website has changed, which can cause broken links.
To report these, please contact us with the publication and broken link.


Guidance for Evaluating Vapor Intrusion in Washington State: Investigation and Remedial Action

Publication number Date Published Date Revised
09-09-047January 2009March 2022
VIEW NOW Guidance for Evaluating Vapor Intrusion in Washington State: Investigation and Remedial Action (Number of pages: 200) (Publication Size: 4197KB)
Note: For more information see related web content below. You may print this publication by clicking on the PDF link above.

Trouble viewing? Try these free options.
Author(s) Mark Gordon, P.E. (2022), Pete Kmet (2009) and Policy & Technical Support Unit, Toxics Cleanup Program
Description Vapor intrusion (VI) can pose a threat to people’s health. This guidance is intended to provide potentially liable persons, cleanup project managers, and consultants a practical approach for assessing VI at sites in Washington where volatile chemicals in the subsurface might pose a threat to indoor air quality. It contains:

* A process for evaluating the VI pathway during a remedial investigation and feasibility study or as part of an independent cleanup action. * Methods, techniques, and references for VI-related soil gas, indoor air, crawl space and ambient air sampling. * References to soil, groundwater, and soil gas VI screening levels as well as indoor air cleanup levels. * Options for communicating with the public when VI is impacting, or has the potential to impact, indoor air quality. * Mitigation measures and techniques to protect receptors from VI.


Mar 2022: Published final, see public comments in Attachment A. Made Implementation Memos 14, 18, 21, and 22 obsolete.

Dec 2021-Feb 2022: Reviewed/incorporated input from public comment period Nov-Dec 2021.

Nov 2021: Extensively revised and made available for public comment Nov 18 through Dec 20, 2021. Incorporated Implementation Memo Nos. 14, 18, 21, and 22. Memos will become obsolete once guidance is final.

April 2018: Changed links to spreadsheet to reflect Ecology's new website. Feb 2016: Revised with 1 change from Oct 2009: “Table B-1 is outdated and should not be used.” Provided link to 2015 spreadsheet.
The mission of the Department of Ecology is to protect, preserve, and enhance Washington’s environment. To help us meet that goal, please consider the environment before you print or request a copy.

ADA Accessibility
The Department of Ecology is committed to providing people with disabilities access to information and services by meeting or exceeding the requirements of the Americans with Disabilities Act (ADA), Section 504 and 508 of the Rehabilitation Act, and Washington State Policy #188.
Visit Ecology’s website for more information.
Contact Mark Gordon at 360-529-7727 or
Keywords Soil gas screening levels, screening levels, volatilization, sampling, vapor intrusion, mitigation, groundwater, soil screening levels, VI pathway, groundwater screening levels
WEB PAGE Vapor Intrusion

User’s Guide for MTCATPH 12.0 & MTCASGL 12.0: Workbook tools for calculating soil and groundwater cleanup levels under the Model Toxics Control Act Cleanup Regulation

Implementation Memorandum No. 22: Vapor Intrusion (VI) Investigations and Short-Term Trichloroethene (TCE) Toxicity

Focus sheet on trichloroethylene (TCE) in residential indoor air

Implementation Memorandum No. 21: Frequently Asked Questions (FAQs) Regarding Vapor Intrusion (VI) and Ecology's 2009 Draft VI Guidance

Implementation Memorandum No. 18: Petroleum Vapor Intrusion (VI): Updated Screening Levels, Cleanup Levels, and Assessing PVI Threats to Future Buildings

Implementation Memorandum No. 14: Updated Process for Initially Assessing the Potential for Petroleum Vapor Intrusion

Model Toxics Control Act Regulation and Statute: MTCA Cleanup Regulation Chapter 173-340 WAC, Model Toxics Control Act Chapter 70.105D RCW, Uniform Environmental Covenants Act Chapter 64.70 RCW