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City of Ramsey Project B1700969 March XX, 2017 Page 10 DRAFT ■ DRO was detected at concentrations of 240 µg/L, 300 µg/L, and 310 µg/L in groundwater samples S-6W, S-8W, and S-9W, respectively. These concentrations exceed the provisional MDH HBV of 200 µg/L for total petroleum hydrocarbons. F.S. Soil Vapor Analytical Results A summary of the soil vapor analytical results is provided in Table 3. The complete laboratory reports with chain -of -custody forms are included in Appendix D. For comparison purposes, Table 3 includes Intrusion Screening Values (ISVs). ISVs were developed by the Minnesota Pollution Control Agency (MPCA) in coordination with the Minnesota Department of Health (MDH) as screening values for evaluating vapor intrusion risks from VOCs identified in indoor air. The potential for indoor air to be impacted by soil vapor intrusion can also be assessed using ISVs. Concentrations of VOCs in air or soil vapor and ISVs are expressed in units of micrograms per cubic meter (µg/m3). Per 2016 MPCA guidance, soil vapor results are compared to 33X ISVs to assess vapor intrusion risk. According to the guidance, soil vapor concentrations greater than 33X ISVs indicate a vapor source with potential vapor intrusion risk is present. A Site with contaminant concentrations greater than 33X ISVs would typically require either mitigation or additional assessment of potential pathways and receptors to better quantify risks, which might include collection of sub -slab or indoor air samples. The following provides a summary of the soil vapor analytical results. ■ Tetrachloroethene (PCE or PERC) was detected at a concentration between its Residential and Industrial ISV. ■ No other VOCs were detected at concentrations greater than Residential ISVs. BRAUN INTERTEC