Brownfields_Content Page_Vapor Intrusion Resources For Environmental Professionals

Vapor Intrusion Resources For Environmental Professionals

Screening for the vapor intrusion (VI) pathway must be conducted at every contaminated site in Wisconsin. The need to investigate VI is elevated when screening indicates the potential for VI is present, especially when trichloroethylene (TCE) is present due to its potential for acute (short-term) and chronic health risks. Mitigation is the process of interrupting the VI exposure pathway such that the vapors no longer affect occupants. Mitigation is not a form of remediation.

This webpage includes resources for environmental consultants to screen the vapor pathway, assess vapor risk and investigate and mitigate vapor intrusion at specific buildings. Additional information about dry cleaning contamination is available on the dry cleaning contamination webpage.

The Responsible Neighbor, a Vapor Intrusion Story - this video for consultants and responsible parties shows how good communication with neighboring property owners affected by environmental contamination benefits everyone involved with an environmental cleanup.
 

Guidance & Forms

Guidance On Addressing Vapor Intrusion

Primary DNR VI Guidance
Supplemental DNR VI Guidance
DHS Guidance
EPA Guidance
ITRC Guidance

The Interstate Technology and Regulatory Council (ITRC) is a state-led environmental coalition working to create innovative solutions and best management practices.

Screening Levels

Wisconsin Vapor Quick Look-Up Table of Indoor Air Vapor Action Levels (VALs) And Vapor Risk Screening Levels (VRSLS)

Indoor air vapor action levels (VALs) are based on U.S. EPA's Regional Screening Level Tables, applying a 1 x 10E-5 excess lifetime cancer risk or a hazard index of 1 for non-carcinogens. The Quick Look-Up Table includes volatile organic compounds (VOCs) that are frequently encountered on remediation sites. The table is updated periodically, primarily when the U.S. EPA updates its tables based on inhalation toxicity data.

The Wisconsin Vapor Quick Look-Up Table Indoor Air VALs and VRSLs (RR-0136) - (updated July 2024) provides:

  • Indoor air VALs for VOCs frequently encountered on remediation sites;
  • Sub-slab vapor risk screening levels (VRLs) for three building categories (residential, small commercial and large commercial/industrial);
  • Attenuation factors for five screening media (crawl space, sub-slab, soil gas, groundwater and sanitary sewer gas).

The table also provides additional instructions and formulas for:

  • Determining VALs and VRSLs for other chemicals using the U.S. EPA's Vapor Intrusion Screening Level (VISL) Calculator.
  • Calculating groundwater VRSLs.
  • Converting units of data [e.g., parts per million by volume (ppbV) to micrograms per cubic meter (µg/m3)].

Although U.S. EPA's VISL Calculator began reporting results with three significant figures in 2020, the DNR continues to apply VALs and VRSLs with two significant figures. This resulted in minor updates to some VALs and VRSLs on the table beginning with the September 2021 publication. This publication is updated periodically based on the changes to U.S. EPA's Vapor Intrusion Screening Levels (VISLs). Any value on the table that is updated from the previous version is bolded.

History of Changes To VALs, VRSLs and Attenuation Factors For Common VOCs

Wisconsin's VALs and VRSLs have changed over time because of updates to U.S. EPA's risk calculations and default attenuation factors. This table, Guidance: History of Changes to VALs, VRSLs and Attenuation Factors for Common VOCs (RR-0137) [PDF], is a quick reference to the historical values with dates when changes occurred, intended to help users understand the basis for past decisions at sites.

Using U.S. EPA's Vapor Intrusion Screening Level (VISL) Calculator To Determine WI VALs and VRSLs

The U.S. EPA Vapor Intrusion Screening Level Calculator (VISL) and VISL User Guide may be used to calculate VALs for compounds not listed in the WI Vapor Quick Look-up Table. The user should:

  1. Adjust the default hazard quotient to 1, the default target risk to 1x10E-5 and choose the risk scenario (residential or commercial).
  2. Select one or more individual chemicals in the selection field.

The calculator will provide the target indoor concentrations for the carcinogenic and noncarcinogenic endpoints for the individual chemical(s) selected using a default attenuation factor of 0.03. The VAL is equal to the lesser of the two values rounded to two significant figures. More detailed instructions are listed on the Wisconsin Vapor Quick Look-Up Table (RR-0136), which is updated periodically based on changes to U.S. EPA's VISLs. Any value on the table that is updated from the previous version is bolded.

Health Information

Health

The DNR partners with the Wisconsin Department of Health Services (DHS) and local health departments regarding short-term (acute) and long-term (chronic) risks to human health related to vapor intrusion, as well as determining appropriate immediate and interim recommendations (e.g., ventilation, mitigation) at affected sites. DHS and local health departments assist the DNR, responsible parties and environmental consultants with health risk communications, including supportive literature.

DHS fact sheet specific to the health concerns of trichloroethylene (TCE) in the air of buildings where the chemical may have unexpectedly traveled (e.g., residences, schools, daycares, businesses that do not use TCE):

DHS two-page fact sheet specific to the health concerns of TCE when used as a chemical in the workplace:

Below are communications from the DHS clarifying when exposure to TCE presents an acute health risk and providing health-based recommendations for how to evaluation whether immediate or interim actions are needed to protect public health.

For more information about vapor intrusion and health, visit the following resources:

Community Outreach

Community Outreach

An effective outreach strategy that anticipates the needs and concerns of affected property owners and the community at large is important when vapor intrusion is involved. When citizens are well-informed about the issues surrounding a site, their questions and concerns can be more effectively addressed. Early two-way communication is essential for a successful investigation and mitigation effort. The following model letters and fact sheets are available for use with your outreach communications.

Template/Model Letters

The DNR created template letters to help environmental professionals communicate vapor intrusion investigations with affected property owners in plain, easily understood language. Because of the complex nature of vapor intrusion investigations, it is not possible to create a template letter for every situation. These template letters are yours to use as you see fit, in whole or in part.

Request For Access To Sample
Sample Results
Request To Install Mitigation System

DNR Fact Sheets

These fact sheets are intended to help environmental consultants and responsible parties communicate critical information about the vapor intrusion pathway to affected property owners. The fact sheets can be used in conjunction with template letters or as stand-alone documents.  When planning an outreach strategy, decide which fact sheets and other tools best support the information you want to communicate to neighbors and other interested parties.

DNR Videos

Like the fact sheets above, these videos are intended to help environmental consultants and responsible parties communicate critical information about the vapor intrusion pathway to affected property owners. These videos should be used in conjunction with fact sheets or other documents.

Active Notification & Telemetry

Continuous monitoring of an active vapor mitigation system (VMS) is important to ensure that the system continues to work as designed. A backup power system safeguards operations of an active VMS in the event of a loss of power.

An active notification primarily measures fan vacuum. Telemetry systems can measure additional parameters (including fan amperage, sub-slab/indoor air pressure differential, temperature and barometric pressure) at sampling intervals determined by the operator. Active notification systems may include:

  • Audible alarms
  • Visual indicators
  • Telemetry systems

Using telemetry allows remote notifications of a VMS failure via an automated phone message, email or text to individuals who may be offsite.

Best Practices For Active Notification And Backup Power At Sites With Active VMS
(Based On Health Risk And Land Use)

Type Of Health Risk Land Use

Audible Alarm/
Visual Indicator

 Telemetry Backup Power
Chronic All Recommended Optional Optional
Acute All except multi-family Recommended Optional Optional
Acute [including due to trichloroethylene (TCE)] Multi-family Recommended Recommended Recommended

Contact the DNR project manager if you have questions regarding whether site-specific conditions may warrant continuous monitoring of the active VMS. For additional information regarding best practices from the American Association of Radon Scientists and Technologists (AARST), see AARST Radon Standards.

*Chronic health risks represent the potential for health impacts over longer exposure durations, and acute health risks represent potential health impacts over shorter exposure durations. For TCE, an acute health risk exists when the contaminant concentration is at or above the vapor action level (VAL) or the vapor risk screening level (VRSL) and people who are or may become pregnant are present. For other compounds, the contaminant concentration indicating an acute health risk is three times the VAL or VRSL for non-carcinogens, or 10 times the VAL or VRSL for carcinogens (non-carcinogen or carcinogen via the inhalation pathway).

See Guidance: Wisconsin Vapor Quick Look-Up Table, Indoor Air Vapor Action Levels And Vapor Risk Screening Levels (RR-0136) for VRSLs for common contaminants.

When using a telemetry system for active notification, consider the following best practices:

  • Program each pressure gauge/transmitter for the telemetry system individually to provide alerts when operating parameters are outside the range of acceptable VMS performance.
  • Set telemetry alert thresholds to capture a percent change in pressure from the established baseline measurement of a given fan/extraction point.
  • Send alerts via telemetry within four hours of VMS system failure for set parameters or with a deviation of 20% change in the vacuum measured in the riser just below the fan.
  • Notify the individual(s) responsible for the VMS within four hours of a system where TCE is a contaminate of concern, or within 24 hours for other contaminants.
  • Develop an operation, monitoring and maintenance plan for the system that includes:
    • Schematic and photographs of system elements, including the location of all sensors and communication hubs.
    • Parameters measured, including vacuum for each system fan and others, as applicable: sub-slab/indoor air pressure differential, fan amperage, barometric pressure, temperature, humidity and airflow.
    • Parameter sampling frequency (i.e., how often the system reports the parameter to the responsible individual).
    • Parameter measurement sensitivity (e.g., inches water column (WC) for vacuum).
    • Notification trigger for each parameter (e.g. inches WC for vacuum) and rationale for the chosen values.
    • Notification delay: the length of time after an alarm is triggered before a notification is sent through the telemetry system. The delay is intended to minimize false alarms yet provide notification quickly enough to minimize impacts to indoor air.
    • Backup power protocol if the primary power fails (e.g., low battery alarms, battery backup and backup generator for the VMS).
    • System provider and specifications.
    • Method of notification (e.g., email, phone message and text message) and individual(s) notified.
    • Anticipated follow-up actions for each parameter.
Training

DNR Webinar Training

The Remediation and Redevelopment Program provides web and teleconference-based training sessions that cover a variety of technical and policy issues. Visit the RR Program training library to access the presentations and find vapor intrusion-related topics.

2014 Vapor Intrusion Outreach "Toolkit"

Anticipating the needs and concerns of affected property owners and the community at large is critically important whenever vapor intrusion is involved. Clear and effective communication with them should be one of the goals of any outreach plan. To help with those efforts, the DNR created a comprehensive toolkit of vapor intrusion communication materials to increase the consistency and effectiveness of communications between responsible parties and the public.

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.

2011 Webinar PowerPoint Slides
2011 Webinar Presentation Videos
Other Resources

Websites

CLU-IN
Workshops and Conferences

Publications

Department of Defense Environmental Security Technology Certification Program (ESTCP)
Naval Facilities Engineering Command (NAVFAC)
American National Standards Institute (ANSI) / American Association of Radon Scientists and Technologists (AARST)
American Petroleum Institute
Electric Power Research Institute (EPRI)

Webinars

Interstate Technology & Regulatory Council (ITRC)
Strategic Environmental Research and Development Program (SERDP) and Environmental Security Technology Certification Program (ESTCP)
Contacts

For more information, contact DNR's vapor intrusion experts.

For more information, contact