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The MPCA Voluntary
Investigation & Cleanup Program (VIC) is now offering two additional
letters as part of Technical Assistance services. Program applicants can
request these letters by selecting ‘Technical Assistance’ during the on line
enrollment, and then specifying the request for these letters in their cover
letter or past/proposed actions letter. Details about both of these letters are
provided below.
1. Completion of Soil Vapor Assessment (when building mitigation is not necessary)
Upon completion of a soil vapor assessment in accordance with the MPCA’s vapor intrusion best management practices (BMPs), a voluntary party may be eligible for a determination by the MPCA that no further investigation of soil vapor is necessary under the current site conditions and land use. This determination is appropriate when a No Action determination for soil vapor is not possible due to unresolved impacts extending beyond the boundaries of the voluntary party’s site; however, a soil vapor assessment has demonstrated that mitigation of the on-site building(s) is not necessary. Per the MPCA vapor intrusion BMPs, two seasonal rounds of sampling at least 30 days apart are necessary to assess vapor intrusion risk at a site and determine that there is not a vapor intrusion area of concern* (VI AOC) present and/or that building mitigation is not necessary. Questions regarding the sampling density and locations necessary for a VI AOC investigation should be directed to the assigned Project Manager or to the Vapor Specialist Team at 651-757-2040. Provided that two seasonal rounds of sampling at the appropriate sampling density demonstrates that vapor intrusion is not a concern at the Site, a vapor mitigation system will not be required. The MPCA may then issue a determination documenting that the vapor assessment was conducted properly and state that no further vapor assessment will be required for the current site conditions and land use. Other requirements for this determination include:
- another media (groundwater or soil) has been investigated to locate any potential sources for soil vapor contamination at the site,
- all conditions of the voluntary party’s No Association Determination (NAD) or Retroactive NAD have been satisfied,
- fully define the extent and magnitude of the soil vapor release at the site in accordance with the BMP.
Potential off-site soil vapor impacts will be referred to the MPCA’s Site Assessment program for further investigation. An institutional control may be necessary to document soil vapor contamination at the site. Additionally, this determination will not form any conclusions regarding groundwater or soil contamination that may or may not exist at the Site.
*Important: If vapor concentration(s) exceed the applicable screening criteria during a VI AOC investigation, AND the exceedance is within 100 feet of an inhabitable on-site building, the MPCA will require a building-specific investigation encompassing sub-slab sampling consistent with Appendix C of the Investigation and Mitigation BMP.
2. Completion of vapor mitigation response actions for on-site building(s)
Upon completion of a soil vapor assessment that results in the mitigation of an on-site building, a voluntary party may be eligible for a determination by the MPCA that building mitigation activities were successfully completed in accordance with an MPCA-approved response action plan and that no further investigation of soil vapor is necessary under the current site conditions and land use. This determination is appropriate when a No Further Action determination for soil vapor is not possible due to unresolved impacts extending beyond the boundaries of the voluntary party’s site; however, a soil vapor assessment has characterized the soil vapor at the site and resulted in building mitigation. Vapor mitigation is necessary when a voluntary party conducts a vapor assessment and identifies potential vapor intrusion risk for an on-site building. Once the vapor mitigation system is installed, verification testing is necessary per MPCA’s vapor mitigation BMP (https://www.pca.state.mn.us/sites/default/files/c-rem3-06.pdf) to confirm the mitigation system is effectively preventing vapor intrusion. A mitigation system operation and maintenance plan and an Environmental Covenant are necessary to ensure the long-term effectiveness of the mitigation system and to provide notice to future property owners. As with the completion of soil vapor assessment determination, the requirements for this determination also include;
- investigation and analysis of another media (groundwater or soil) to locate any potential sources for soil vapor contamination at the site,
- all conditions of the voluntary party’s NAD or Retroactive NAD have been satisfied,
- fully define the extent and magnitude of the soil vapor release at the site in accordance with the BMP.
Potential
off-site soil vapor impacts will be referred to the MPCA’s Site Assessment
program for further investigation.
If
you have questions regarding this message, please contact any of the following:
Gary
Krueger (gary.krueger@state.mn.us,
651-757-2509)
Chris
Formby (christopher.formby@state.mn.us,
651-757-2712)
Andrew
Nichols (andrew.nichols@state.mn.us,
651-757-2612)
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