The MPCA has developed procedures for vapor intrusion mitigation and public communication work that will be used by MPCA and our contractors for doing these aspects of vapor intrusion work. 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.
Vapor intrusion guiding principles — Version 4.0
The vapor intrusion guiding principles are the basis for the more detailed direction and guidance outlined in the vapor intrusion BMP’s.
- 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.
- 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.
Investigation and building mitigation decision best management practices
- Best Management Practices for Vapor Investigation and Building Mitigation Decisions (c-rem3-06e)
- Appendix A — Minnesota Soil Gas List — TO15 (c-rem3-06f)
- Appendix B — Sampling Methodology
- MPCA Sub-slab Sampling Methodology — This video demonstrates the steps for collecting a representative sub-slab vapor sample from beneath a building's concrete floor slab.
- Appendix C — Recommended Number of Samples per Building Foundation Size (c-rem3-06h)
- Appendix D — Vapor Intrusion Building Survey Form (c-rem3-01a)
Building mitigation best management practices
- Attachment A — Pre-Mitigation Diagnostic Checklist
- Attachment B — Active Mitigation System Installation Checklist
- Attachment C — Post-Mitigation Diagnostic Checklist
- Attachment D — Post-Mitigation Confirmation Sampling Checklist