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
The vapor intrusion guiding principles are the basis for the more detailed direction and guidance outlined in the vapor intrusion BMP’s.
- Vapor Intrusion can impact indoor air quality, potentially creating health concerns.
- To have a vapor intrusion risk there must be an occupiable building and soil vapor contamination.
- Variations in soil vapor concentrations can be caused by many factors that vary seasonally such as soil moisture, frost, depth to groundwater, etc. Because of this, a minimum of two seasonal sampling events — during heating and non-heating seasons — from multiple sampling points are needed to decide there is no vapor intrusion risk.
- To be protective and account for uncertainties, mitigation decisions are based on the possibility of health risks from vapor intrusion.
- Effective public communication is essential to doing vapor intrusion work well.
- Documenting vapor investigation and mitigation decisions on maps prepared in a consistent format is an effective way to communicate the presence of a vapor intrusion area of concern and building mitigation status to a variety of stakeholders.
- The effectiveness of a mitigation system needs to be verified with confirmation testing.
- Expedited action is needed when there is increased vapor risk to sensitive people present AND exposures to contaminants above health-protection goals or greater potential for such exposures.
- A plan is needed to assure continued operation of mitigation systems.
- 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 source should be addressed with remediation, if feasible.
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