ARCHIVED REPORTS_XR0004266 - Laserfiche WebLink

Home Browse Search

1 Report of Findings Frontier Transportation 0702-177 September 5, 2002 Page 5 diameter and 6 inches long. Soil samples were screened for petroleum hydrocarbons in the field using a PID. A total of sixteen (16) soil samples collected from newly installed monitoring wells MW- 3R,MW-12, and MW-13, which were analyzed for TPH-g, BTEX, and MTBE using EPA methods 8015 and 8021B. Soil samples that identified detectable MTBE concentrations by 8021B were confirmed using EPA method 8260B (See Table 4 for Soil Boring Sample Results and Appendix B for Laboratory Analytical Reports). Soil sample analysis results identified impacted soil from monitoring well MW-13 only. Soil sample results from MW-3R identified trace benzene as 6 µg/kg at 20' bg, MTBE as 78 at 15' bg, and 170 at 20' bg. No other detectable concentrations of TPH-g and BTEX were identified in soil samples collected from MW-3R. Soil samples collected from monitoring well MW-12 contained no detectable concentrations of TPH-g, BTEX, and MTBE. TPH-g ' concentrations were identified as 2 mg/kg at 5' bg and 700 mg/kg at 10' bg in soil collected from monitoring well MW-13. However, concentrations of TPH-g were not detected(<1 mg/kg) in MW-13 from 15' bg to 40' bg. The maximum BTEX concentration in soil from MW-13 was identified as 115,000 µg/kg at 10' bg. BTEX concentrations decrease at 15' bg to<17 Mg/kg, ' but then increase to 227 µglkg at 20' bg. At 40' bg, BTEX concentrations attenuate in soil to <12 µglkg. Concentrations of MTBE were identified at a maximum of 25,000 µg/kg in soil from MW-13 at 10' bg. MTBE attenuates to 11 µg/kg at 40' bg in soil from MW-13. 5.0) CONCLUSIONS ' Based on the excavation pit results, petroleum hydrocarbon impacted soil was identified mostly along northern and eastern sidewalls below the water table. Visual inspection identified no significant soil contamination until groundwater was reached. Groundwater appeared to be moving through horizontal stringers of fine-grained silty sand. Soil sample results identified significant concentrations of petroleum hydrocarbons still left in place along the northern and ' eastern sidewalls. In addition, soil sample results from well installation identified impacted soil in MW-13 located northwest of the excavation pit. It is therefore concluded that the majority of impacted soil is localized to the depth of groundwater and the lateral extent of this impacted soil ' has not been defined to the northwest, northeast, and southeast of the excavation pit. 6.0) RECOMMENDATIONS BEII recommends that soil excavation be performed up to 15' bg north from the former BEII excavation pit(See Figure 5 for Proposed Excavation Area). The recommended excavation would be performed the exact same way, including the pit size. This will prevent the pit from