Laserfiche WebLink
5 <br /> foot intervals at the boundary of the Site, RI soil sampling was conducted in a biased manner. <br /> Biased samples were collected to delineate areas where impacted soil was identified during <br /> previous investigations conducted at the Site. A total of 13 soil borings were installed at the Site. <br /> Soil samples were collected by hand auger and direct push probe technology at various locations. <br /> Soil samples were analyzed for PAH,TPH, Title 22 Metals, and VOCs. <br /> Soil Gas Sampling. Soil-gas samples were collected from 15 soil-gas probes installed during the <br /> RI. Soil-gas probe construction and sampling was conducted in accordance with the DTSC <br /> Advisory—Active Soil Gas Investigations (DTSC, 2003). Soil-gas probes were positioned at five <br /> bgs and samples were collected into pre-cleaned, six-liter, flow-controlled, evacuated SUMMA® <br /> canisters. Samples were analyzed for VOCs by USEPA Method TO-15 plus naphthalene with <br /> isobutane as a tracer(leak detector). <br /> Groundwater Sampling. Groundwater samples were obtained from five monitoring wells(TW-1 <br /> through TW-5) installed at the Site. Wells TW-1 through TW-4 were installed as part of the SI <br /> conducted at the Site in 1988 and TW-5 was installed as part of the RI. Prior to sampling, all <br /> wells were developed until groundwater parameters had stabilized. A minimum of 7 days after <br /> development was allowed prior to sampling of the five groundwater wells. Groundwater samples <br /> were analyzed for PAH, TPH,Title 22 metals, and VOCs. <br /> 3.4 Analytical Results <br /> Soil. A total of 71 samples were collected as part of the RI and analyzed for PAHs using United <br /> States Environmental Protection Agency(EPA)Method 8310;TPH as gasoline, diesel and motor <br /> oil using EPA Method 8015 Modified; and for Title 22 Metals using the EPA Method 6010/7000 <br /> Series. Additionally, 11 samples were analyzed for VOCs using EPA Method 8260. Results <br /> from these samples showed localized MGP and gasoline UST related soil contamination <br /> including: PAHs, TPH(gasoline,diesel and motor oil),various metals and VOCs. The following <br /> is a brief description of impacts identified at the Site. <br /> PAH analyses were conducted on 71 soil samples, including eight duplicate samples, collected <br /> during the RI. A total of 24 soil samples(including duplicates) at the Site contained carcinogenic <br /> PAHs (CPAHs), expressed as benzo(a)pyrene[B(a)P] equivalents, above the calculated detection <br /> for B(a)P equivalents of 0.00285 milligrams per kilogram (mg/kg). However, only five of these <br /> 24 samples had concentrations greater than the presumed cleanup criteria of 0.9 mg/kg for B(a)P <br /> equivalents. These samples, along with samples collected during previous investigations, were <br /> primarily confined to depths shallower than three feet bgs. Samples collected in the northeastern <br /> portion of the Site in Grid Bl exhibited the highest CPAH and B(a)P equivalent concentrations. <br /> A total of 43 samples had non-carcinogenic PAHs (NCPAH) detections above laboratory <br /> reporting limits (RLs). The highest NCPAH concentrations were also reported in Grid Bl at <br /> depths shallower than 3 feet bgs. At two locations, E3-1 and Bl-1, TPH/PAH impacts have not <br /> been delineated laterally; however, vertical delineation of PAH impacts have been achieved <br /> across the entire Site. <br /> Results for TPH analyses in soil showed that nine of the 71 samples analyzed for TPH as <br /> gasoline (TPH-g) had detectable concentrations ranging from 0.61 to 860 mg/kg. The highest <br />