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Field Investigation Report Old Snelling Avenue and County Road E Improvements WSB Project No. R-015447-000 Page 7 3.2 Groundwater Sample Results Three (3) groundwater samples were collected from borings EB-1, EB-8, and EB-12 during this investigation. Groundwater samples were identified using the boring number (GW-1, GW-8, and GW-12). Prior to sampling, groundwater levels were measured at depths ranging from 5.10 to 9.21 feet below grade at borings EB-1, EB-8, and EB-12; groundwater was not encountered in the other 11 borings. Groundwater analytical results are summarized in Table 2, which also includes applicable MDH Health Risk Limits (HRLs) and MPCA limits for contaminated groundwater discharges, where established, for comparison purposes. A copy of the laboratory analytical report is included in Appendix C. The following is a summary of the groundwater analytical results: · No sheen was observed in the groundwater samples. · No GRO or VOCs were detected above laboratory reporting limits in the groundwater samples. · Lead was detected in each groundwater sample at concentrations ranging from 300 micrograms per liter (µg/L) to 1,580 µg/L. No HRLs or limits for contaminated discharge are established for lead in groundwater. · DRO was detected in sample GW-8 at a concentration of 244 µg/L, which was below the MPCA criteria for remedial investigation of 1,000 µg/L. DRO was not detected above laboratory reporting limits in groundwater samples GW-1 and GW-12. 3.3 Soil Vapor Results Two (2) soil vapor samples were collected from four feet below grade at borings EB-2 and EB-9 during the investigation and submitted for laboratory analysis. Soil vapor samples were identified using the boring number ((SV-2 (4FT) and SV-9 (4FT)). The soil vapor sample results are summarized in Table 3. The sampling results were compared to the MPCA 33X residential and commercial/industrial intrusion screening values (ISVs). The 33X ISVs were established to evaluate soil gas and predict the amount of a contaminant in indoor air that may result from vapor intrusion. A copy of the laboratory analytical report is included in Appendix C. The following is a summary of the soil vapor analytical results: · No elevated PID readings were observed while collecting the soil vapor samples. · 1,3-Butadiene was detected above the 33X residential ISV (9.3 micrograms per cubic meter (µg/m3)) in soil vapor samples SV-2 (4FT) and SV-9 (4FT) at concentrations of 50 and 38 µg/m3, respectively. · Nine additional petroleum VOCs were detected above laboratory reporting limits but at concentrations below the 33X residential ISVs. These compounds included benzene, ethanol, ethylbenzene, n-heptane, n-hexane, propylene, toluene (methylbenzene), m&p- xylene and o-xylene. · Three non-petroleum VOCs were detected above laboratory reporting limits but at concentrations below the 33X residential ISVs. These compounds included 2-butanone (methyl ethyl ketone (MEK)), cyclohexane, and tetrachloroethene (PCE).