COMPLIANCE INFO_FILE 7 - Laserfiche WebLink

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generally to the north-northeast with slight seasonal variations and with a relatively flat gradient, typically in the range of 0.004 to 0.006 feet/feet. Aquifer parameters of hydraulic conductivity, transmissivity and storativity vary and typically range from 8 to 140 feet/day; 79 to 3,700 square feet/day; and 0.0014 to 0.13, respectively. Nature and Extent of Impact The area of greatest known impact by VOCs to soil and ground water at the site is centered in the area extending from the concrete pads to the Engine House, and from the railroad tracks to the oil/water separators. Several potential sources of these impacts include the Engine House pit located inside the Engine House; the sump located immediately adjacent to and on the south side of the Engine House; the former industrial wastewater lines which extend from the sump to the former Toxic Pits Cleanup Act (TPCA) ponds and across both ends of the concrete pads; the above ground storage tanks (converted to the oil/water separator); and general spillage to the ground. Impacts by halogenated VOCs (HVOCs) are believed to be related to past maintenance operations associated with the Engine House. Impacts by aromatic VOCs (AVOCs) are believed to be associated with former fueling operations. The extent of VOC impacts to A-Zone ground water and vadose zone soil is shown in Drawing G-1 and Drawing G-2. Summary of Soil Impacts in the Vadose Zone A remedial objective for this remedial action is to remove chemical constituents in vadose zone soil which represent a source of impacts to A- zone ground water at the site. To determine the placement of extraction wells, laboratory analytical data for AVOC and HVOC concentrations in vadose zone soil was reviewed. This data indicates that HVOC impacts at the site are centered in the vicinity of TW-1. Total HVOCs have been found in soil at concentrations up to 583 mg per kilogram (mg/kg) in the vicinity of well TW-1. Total HVOCs in soil decrease to generally non detectable concentrations at a radial distance of approximately 75 to 100 feet from TW-1, although several soil monitoring points at distances greater than 100 feet from TW-1 indicate the presence of HVOCs in soil at greater than non-detectable concentrations. Most notably, a soil sample collected at MW-14B contained total HVOCs at a concentration of 65 mg/kg, while a soil sample collected at SB-6 contained total HVOCs at a concentration of 98 mg/kg. 2-2