HRA PACKET 06142022 - Laserfiche WebLink

Home Browse Search

Phase II Environmental Site Assessment 2534 Kenzie Terrace WSB Project No. R-020198-000 Page 7 values, Environmental Protection Agency (EPA) Maximum Contaminant Levels (MCLs), and MPCA National Pollutant Discharge Elimination System (NPDES) General Industrial Pump-Out Permit (GIPP) criteria. For compounds where multiple HBG values or NPDES GIPP values were provided, the most stringent value provided was used for regulatory comparison. The HBG values include Health Risk Limits (HRLs), Health Based Values (HBVs), or Risk Assessment Advice (RAA) values. It should be noted that HRL, HBV, and RAA values are used as a proxy for evaluating the impacts to groundwater; however, for construction purposes the treatment limits for groundwater dewatering discharge would be established in the discharge permit for the project. Groundwater analytical results are summarized in Table 2. Concentrations that were found to exceed regulatory criteria are highlighted on Figure 4. A copy of the laboratory analytical report is included in Appendix C. The following is a summary of the groundwater observations and analytical testing results: Groundwater was encountered in boring B-1 at a depth of 22.7 feet below grade and boring B-4 at a depth of 11.8 feet below grade. Groundwater was not encountered in borings B-2 and B-3. No visual or olfactory evidence of contamination was observed in the groundwater sample. Benzene was detected at a concentration of 45.9 micrograms per liter (µg/l) in groundwater sample GW-4, which exceeds the MDH HRL of 2 µg/l. 1,2-Dichloroethane (1,2-DCA) was detected at a concentration of 68.2 µg/l in groundwater sample GW-4, which exceeds the MDH HRL of 1 µg/l. Five additional VOCs were detected at concentrations equal to or greater than the laboratory reporting limits in groundwater sample GW-4 but below regulatory criteria. No VOCs were detected at concentrations equal to or greater than the laboratory reporting limits in groundwater sample GW-1. Dissolved arsenic and/or barium were detected at concentrations greater than the laboratory reporting limits but below regulatory criteria in groundwater samples GW-1 and GW-4. No other metals were detected at concentrations equal to or greater than the laboratory reporting limits in the groundwater samples. DRO was detected at a concentration of 1,220 µg/l in groundwater sample GW-4, exceeding the MPCA criteria for remedial investigation of 1,000 µg/l and the NPDES GIPP criteria of 200 µg/l. DRO was detected at a concentration of 245 µg/l in groundwater sample GW-1, exceeding the NPDES GIPP criteria. GRO was detected at a concentration of 378 µg/l in groundwater sample GW-4, exceeding the NPDES GIPP criteria of 200 µg/l. GRO was not detected at a concentration equal to or greater than the laboratory reporting limit in groundwater sample GW-1. 3.3 Soil Vapor Results A total of four soil vapor samples were collected during the investigation and submitted for laboratory analysis for VOCs. The soil vapor samples were collected from four feet below grade. For comparison purposes, the analytical results are compared to 33 times the MPCA Residential Intrusion Screening Values (ISVs) and Expedited Intrusion Screening Value (EISVs) and 33 times the MPCA Commercial/Industrial ISVs and EISVs. The 33X ISVs and EISVs were established to evaluate soil vapor risks and to predict the amount of a contaminant in indoor air that may result from vapor intrusion.