Vapor intrusion guidance

The MPCA has developed best practices for vapor intrusion mitigation and public communication work used by the agencies and our contractors. The procedures and documents were developed working closely with the Minnesota Department of Health, environmental consultants under contract to MPCA, and expert practitioners in radon mitigation.

Investigation and mitigation decision

• Vapor investigation and mitigation decision best management practices (c-rem3-06e)
• Appendix A — Minnesota soil gas list — TO15 (c-rem3-06f)
• Appendix B — Video: MPCA sub-slab sampling methodology (5 min.): demonstrates steps for collecting a representative sub-slab vapor sample from beneath a building's concrete floor.
• Appendix C — Recommended number of samples per building foundation size (c-rem3-06h)
• Appendix D — Vapor intrusion building survey form (c-rem3-01a)

Map templates

• Introduction to vapor intrusion map templates (c-s4-10)
• Vapor intrusion map templates (*.zip)

Building mitigation

• Vapor mitigation best management practices (c-rem3-06)
• Pre-mitigation diagnostic checklist (c-rem3-06a)

  Attachment A
• Active mitigation system installation checklist (c-rem3-06b)

  Attachment B
• Post-mitigation diagnostic checklist (c-rem3-06c)

  Attachment C
• Post-mitigation confirmation sampling checklist (c-rem3-06d)

  Attachment D

Parking facilities and vapor mitigation

Soil vapor contaminated with non-petroleum and petroleum related VOCs may enter parking facilities and then adjacent occupied spaces. The MPCA has developed a summary of readily available literature, codes, parking facility products, experiences with parking facility forensic investigations, and discussions with design engineers.

• Parking facilities and vapor intrusion mitigation (c-rem3-06i)

Intrusion screening values

Chemical-specific, risk-based inhalation screening criteria for volatile compounds, used to evaluate indoor air quality.

• Intrusion screening values (ISVs) for vapor intrusion risk evaluation (aq1-36)
• Intrusion screening values Technical Support Document (c-rem3-12)

Communications and public outreach

• Vapor communications and public outreach best management practices (c-rem3-06j)

Communications resources

• Vapor intrusion 101 (WiDNR) — Using a hand-drawn/animation technique, this video introduces the concept of vapor intrusion to people who may be unfamiliar with it by showing the root cause, how it spreads underground, and what can be done about it.
• Understanding your vapor intrusion test results (c-s1-07a)
• The responsible neighbor: A vapor intrusion story (WiDNR) — A video for consultants and responsible parties shows how good communication with neighbors benefits everyone involved with an environmental cleanup.
• Example of final property summary report (c-rem3-07)
• Vapor intrusion information sheets (MDH) — Key information on vapor intrusion, health, and TCE/PCE for residential and commercial building owners and occupants. Information is in multiple languages and can be used for vapor intrusion outreach and notification.

Vapor intrusion guiding principles

These vapor intrusion guiding principles are the basis for the more detailed direction and guidance outlined in the vapor intrusion BMPs.

• Underground chemical vapors can migrate from the source of contamination through the soil and building foundations into indoor air creating a health concern.
• The primary goal of vapor intrusion work is to identify and address potential human health risks.
• Effective public communication is an essential aspect of vapor intrusion work. This includes public awareness of health risks from vapor intrusion, vapor intrusion areas of concern, areas where mitigation has been installed and areas where more testing is needed.
• All people should be notified when they own or spend significant time in a building with a potential vapor intrusion risk.
• Prompt and effective notifications are needed when indoor air data shows that vapor intrusion may affect the quality of the air people breathe.
• All people should be given the opportunity to self-identify as a sensitive individual.
• Building mitigation decisions are based on current and future possibilities of a health risk from vapor intrusion.
• Multiple factors contribute to variations in soil vapor contaminant levels.
• Seasonal sampling from multiple sampling points are needed to determine there is no vapor intrusion risk.
• The effectiveness of a mitigation system needs to be verified with confirmation testing.
• Expedited action is needed when the data indicates the potential for a short-term health risk.
• A plan is needed to assure continued operation of mitigation systems until data shows continued operation is no longer needed.
• Future property owners need to be notified of the presence and need for continued operation of mitigation systems or unresolved vapor intrusion risks.
• When there is a source creating vapor contamination, the best practice is to remediate the source if feasible.
• The obligation for addressing the possibility of vapor intrusion into a building and the source of the contamination are different for Superfund responsible parties compared to non-responsible voluntary parties and property owners.
• A clear and predictable process is important for timely facilitation of property transactions.