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For information on vapor intrusion, contact:
Terry Evanson
Remediation & Redevelopment Program
608-266-0941

Vapor intrusion

Chemicals used in commercial activities – such as dry cleaning chemicals, chemical degreasers and petroleum products such as gasoline – are sometimes spilled or leaked into soil and groundwater. These chemicals, known as volatile organic compounds (VOCs), often become gases or vapors, which can travel from contaminated groundwater and soil and enter buildings. This process is known as vapor intrusion.

Homeowner resources

Resources for property owners

To learn the basics about how vapor intrusion occurs, visit EPA's Basic Information for Vapor Intrusion [exit DNR].

The Wisconsin Department of Health Service’s vapor intrusion fact sheet (Health Hazards: Vapor Intrusion [exit DNR] ) discusses vapor intrusion and investigation as well as how indoor air quality in homes can be improved, regardless of the source of chemical vapors.

Professional resources

Resources for environmental professionals

DNR vapor intrusion guidance
  • Addressing Vapor Intrusion at Remediation & Redevelopment Sites in Wisconsin (RR-800) [PDF] - This guidance document describes the process responsible parties and consultants should use to address the vapor intrusion pathway at contaminated properties. Vapor intrusion refers to the migration of volatile contaminants through soil, utility corridors, and other pathways to enter occupied buildings. The guidance sets out a stepwise approach for screening, investigating, evaluating vapor risk, remediating and mitigating this pathway. Conditions under which sites with vapor intrusion can be closed along with examples applying the principles set out in the guidance are included.

Please note: The Remediation & Redevelopment (RR) Program is revising its approach regarding the timing of collecting sub-slab vapor and indoor air samples in "residential settings" (e.g., home and schools). Current guidance allows sub-slab vapor samples to be collected followed by indoor air sampling if vapor risk screening levels (VRSL) are exceeded in sub-slab vapors. The RR program now strongly encourages responsible parties to collect concurrent sub-slab and indoor air samples in buildings with residential settings. Addressing Vapor Intrusion at Remediation & Redevelopment Sites in Wisconsin (RR-800) [PDF] contains further information.

Evaluation of the vapor migration pathway

Vapor migration is a contaminant migration pathway that needs to be evaluated like other pathways, and is required by s. NR 716.11(5)(a) and (b). DNR encourages environmental professionals to use EPA's Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils [exit DNR] and ITRC's Vapor Intrusion Pathway: A Practical Guide [exit DNR] for more information. Please note that the vapor screening levels found in Tables from EPA's 2002 guidance are out of date. To determine Wisconsin's vapor action levels for indoor air and vapor risk screening levels for sub-slab, soil gas, and groundwater, please use EPA's Regional Screening Level Tables [exit DNR]. More information on risk screening levels can be found in DNR's vapor intrusion guidance (RR-800) [PDF].

Additional guidance
EPA guidance
DHS guidance
ITRC guidance

Other resources

Naval Facilities Engineering Command (NAVFAC)
American Petroleum Institute
Electric Power Reserach Institute (EPRI)

Screening levels

Quick look-up table for indoor vapor action levels for selected VOCs

Indoor air vapor action levels (VAL) are based on U.S. EPA's Regional Screening Level Tables [exit DNR], applying a 1 x 10-5 excess lifetime cancer risk. The "Quick Look-Up Table" below also provides information on how to convert indoor air concentration units and how to calculate groundwater to indoor air screening values. This table is updated semi-annually.

Please Note: With the recent changes to both TCE & PCE, the non-carcinogenic values (HI=1) control the indoor air screening levels for these chemicals, NOT the life time cancer risk of 10-5. The EPA RSL tables use the notation c** to indicate that the non-carcinogenic (HI=1) value for a chemical is LESS THAN 10 times the life time cancer risk level of 10-6. Because Wisconsin uses a 10-5 life-time cancer risk screening level for indoor air, the value for the non-carcinogenic end point (HI=1) is lower than the carcinogenic end point.

Vapor Intrusion Screening Level Calculator by U.S. EPA

The Office of Superfund Remediation and Technology Innovation (OSRTI) developed a spreadsheet tool called the Vapor Intrusion Screening Level (VISL) Calculator and VISL Users Guide that: (1) lists chemicals considered to be volatile and sufficiently toxic through the inhalation pathway; and (2) provides VISLs for groundwater, soil gas and indoor air, based on U.S. EPA Risk Screening Tables. Wisconsin DNR screening levels can be calculated from the U.S. EPA VISL by changing the target risk for carcinogens from 1.00E-06 to 1.00E-05.

Training

2011 Vapor Intrusion Issues in Wisconsin - FET Webinars

In March 2011, staff from the RR Program participated in two Federation of Environmental Technologists (FET) webinars about vapor intrusion issues in Wisconsin. The agenda, PowerPoint presentation slides and videos of the presentations are available below.

PowerPoint slides
Video presentations

Contacts

If you have general questions you may contact DNR's Terry Evanson (608-266-0941). For site specific questions please contact a DNR regional project manager.

DNR Region Contact Person Telephone Number
Northern Phil Richard 715-762-1352
Northeast Jennifer Borski 920-424-7887
South Central Jim Walden 608-267-7572
Southeast Pam Mylotta 414-263-8561
West Central Tom Hvizdak 715-421-7850

To determine which project manager you should contact please see the Remediation and Redevelopment Program's regional map.

Last revised: Tuesday April 16 2013