CC PACKET 09242024 - Laserfiche WebLink

Home Browse Search

September 18, 2024 City Council – City of St. Anthony Village Page 3 of 4 Reference: Environmental Conditions Summary – Proposed Tibyan Community Center, 2401 Lowry Avenue NE, St. Anthony, Minnesota (the Site) Site Soil and Groundwater Conclusion and Recommendations Previous environmental investigations have identified petroleum-related and chlorinated VOCs in soil in concentrations above respective MPCA SLVs, but below MPCA residential and industrial SRVs. The soil impacts appear to be the result of historical operation of the Site as a drycleaning facility and fueling station, as well as the continued presence of chlorinated VOC-impacted groundwater. Observed impacts are located within the upper 10 feet of the subsurface, and primarily in the northern two-thirds of the Site, or in areas of historical and current Site buildings. It is recommended that any future soil handling and management activities are performed in cooperation with an environmental professional and the MPCA-approved Response Action Plan and Construction Contingency Plan (RAP/CCP) as prepared for MPCA Site IDs BF0002310 and BF0002577. Previous environmental investigations have identified petroleum-related and chlorinated VOCs in groundwater in concentrations above respective MDH HRLs and/or HBVs. The groundwater impacts appear to be the result of historical operation of the Site as a drycleaning facility and fueling station. Observed impacts are located throughout the Site. While proposed Site plans do not include activities expected to encounter groundwater, it is recommended that if groundwater is encountered as part of future Site activities an environmental professional and the MPCA-approved RAP/CCP as prepared for MPCA Site IDs BF0002310 and BF0002577 are consulted. Site Soil Vapor Intrusion Conclusion and Recommendations Previous environmental investigations have identified petroleum-related and chlorinated VOCs in soil vapor in concentrations above respective MPCA risk screening criteria. The most elevated concentrations, with instances exceeding respective 33X MPCA industrial EISVs, have been detected in the parking areas located north and east of the Site building. However, TCE has been detected in concentrations exceeding its 33X MPCA industrial ISV in sub-slab samples collected from beneath the existing Site building. Historical corresponding indoor air samples collected while the building was in operation did not detect concentrations above respective MPCA industrial ISVs. Ultimately, as a result of the completed pathway evaluation completed between 2018 and 2020, an active vapor mitigation system was recommended to be installed in any future occupied Site building. Recent indoor air sampling completed in August 2024 following a period of vacancy at the Site building identified PCE in a concentration exceeding its MPCA industrial ISV in the main lobby area located in the northwest portion of the Site building. PCE was also detected in concentrations exceeding its MPCA residential ISV in the other two samples, and TCE was detected in a concentration exceeding its MPCA residential ISV in the main lobby. It should be noted again that samples collected while the building was occupied did not detect elevated contaminants of concern. It was also reported by Tibyan Community Center that the HVAC system in the Site building was damaged during recent vandalism and was in the process of being repaired. It is recommended that the building HVAC system is made fully functional prior to building occupancy. It is also recommended that an active vapor mitigation system is implemented in the Site building in accordance with the MPCA-approved RAP/CCP. However, a vapor intrusion building survey form completed during the August 2024 sampling not identify building conditions that would expedite vapor intrusion to the indoor air, and all historical sub-slab soil vapor samples did not contain chlorinated VOCs exceeding 33X MPCA industrial EISVs, so it is Stantec’s opinion that the building can be occupied on an industrial basis while Tibyan Community Center finalizes details and financing options to complete the active vapor mitigation system. 74