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

Publication number Date Published Date Revised
18-09-047November 2018October 2019
VIEW NOW This publication is historical. It is unavailable on our website. To request a copy, please use the contact listed below.
Author(s) Ed Jones (Hazardous Waste and Toxics Reduction) and Mark Gordon, P.E. (Toxics Cleanup Program)
Description This memo applies to any cleanup site where trichloroethene (TCE) is a subsurface contaminant of concern and a vapor intrusion (VI) pathway is being evaluated. Trichloroethene is a chemical also known as trichloroethylene or TCE.

In 2009, the Washington State Department of Ecology published Draft Vapor Intrusion Guidance, publication no. 09-09-047. This memo supplements the draft 2009 VI guidance. While much of the draft guidance is applicable to sites where TCE VI is a possibility, this memo addresses several issues that were not previously considered. This includes: 1) response speed, 2) focus on women of childbearing age, and 3) type of public outreach.

The memo also provides Method B and C indoor air action levels, as well as soil gas and groundwater screening levels to help evaluate whether there is the potential for short-term TCE risks to occur.


This memo was originally published as a draft for public comment on November 21, 2018. In October 2019, we finalized it based on comments received during the draft memo’s public comment period (from November 21, 2018 through Monday, January 7, 2019), and based on comments received from Seattle & King County Public Health and Ecology staff after the comment period closed.
NOTES This publication has been replaced by a new publication. In March 2022, this document was incorporated into “Guidance for Evaluating Vapor Intrusion in Washington State: Investigation and Remedial Action,” which is available at
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.

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Keywords air contamination, trichloroethylene (TCE), Vapor Intrusion (VI), volatile organic compounds (VOC), soil contamination, groundwater contamination, indoor air quality, Subsurface vapor, Vapro Intrusion pathways, trichloroethene (TCE)
WEB PAGE Vapor Intrusion

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

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