Vapor Intrusion

Vapor Intrusion Program


What is Vapor Intrusion (VI)?

Vapor intrusion (VI) is the migration of vapor-forming chemicals from a subsurface source such as the soil and/or groundwater into the indoor air of an overlying building -- similar to the seepage of radon gas into homes. It migrates up through the air space in permeable soils, open fractures in bedrock or clay tills, utilities, sumps, or cracks in the building foundation. Vapors can travel along preferential pathways such as along porous soil surrounding utility pipes and cracks in the foundation and gaps of buildings where pipes enter the basement.

Trichloroethylene (TCE) in Air

Air contaminated with TCE is of serious concern due to the health dangers it poses when it's inhaled. Since it volatilizes very easily into the air, vapors contaminated with TCE can migrate from the TCE-impacted soil or groundwater underneath homes and buildings and migrate into the indoor air

TCE is a health concern because it is characterized as “carcinogenic to humans” by all routes of exposure (USEPA 2005b Guidelines for Carcinogen Risk Assessment).  In addition, it poses a noncancer toxicity (findings based on the 2011 IRIS Study) to the central nervous system, kidney, liver, immune system, male reproductive system, and the developing embryo/fetus (recent findings have indicated that fetal heart defects may result if pregnant women are exposed to TCE in their earliest stages of gestation).  The most common sources of non-occupational exposure to TCE are ambient air and drinking water.

Industrial uses of TCE are varied and include being used as a degreasing solvent for metal parts during the manufacturing process, as an extractor of caffeine from the coffee bean, and as an inhalant analgesic in childbirth (historically). It is a breakdown compound of tetrachloroethene (PCE), a common dry cleaning solvent that is also sometimes found in the soil and groundwater.

Supplemental Guidance: Screening and Evaluating Vapor Intrusion

The Department of Toxic Substances Control (DTSC), the State Water Board, and the San Francisco Bay Regional Water Quality Control Board (SF Bay Regional Water Board) are currently developing a supplemental vapor intrusion guidance document for conducting uniform vapor intrusion evaluations in California.  This guidance document, when finalized, will serve as a 2018 Supplement to existing guidance (namely, DTSC 2011 Vapor Intrusion Guidance and SF Bay Regional Water Board 2014 Interim Framework). It provides detailed 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 attenuation factors
  • Risk management framework for vapor intrusion
  • California-specific vapor intrusion database

The Supplemental VI Guidance Document is under development and should be available to the public in the Winter of 2018 as an Interim final document.  Presentations on the topic have been conducted at two recent, industry conferences (2018 AEHS Conference Presentation and 2018 CUPA Conference Presentation).  DTSC and the Water Boards are planning public training likely in Northern and Southern California.  When the actual dates are established, they will be posted below.


Trichloroethelyne Factsheet

Trichloroethelyne (TCE) Fact Sheet (Coming Soon)

Access Agreement Template

Access Agreement Template (Coming Soon)


Geotracker ESI is the largest receiving system nationally for analytical and field data for cleanup sites. This powerful web application is used for secure reporting of laboratory data, field measurement data, documents and reports.
Geotracker is a map-based information database that provides online access to environmental data for sites, including DoD sites (open or closed) under the water boards' oversight
Geotracker GAMA system consists of groundwater sampling data and water level information.
Envirostor is a similar database for sites under the Department of Toxic Substances Control (DTSC) oversight.

VI Contacts

Water Boards

Lead Contact:
Tina Ures
Engineering Geologist
State Water Resources Control Board
Phone: (916) 341-5749

Water Board Group Members
Cheryl Prowell
Senior Water Resource Control Engineer
San Francisco Bay Regional Water Quality Control Board

Ross Steenson
Senior Engineering Geologist
San Francisco Bay Regional Water Quality Control Board

Water Board Public Outreach
Marina Perez
Public Participation Specialist
Department of Health Services

Steve McMasters
Senior Engineering Geologist
State Water Resources Control Board

Nicole Fry
Research Scientist III
San Francisco Bay Regional Water Quality Control Board


Claudio Sorrentino
Senior Toxicologist
Department of Toxic Substances Control

Dan Gallagher
Senior Haz Substances Eng Geologist
Department of Toxic Substances Control

Barbara Renzi
Associate Toxicologist
Department of Toxic Substances Control




Research Articles

Waterboards Cleanup Programs