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r <br /> Three follow up soil borings placed in and around the former UST pit were drilled to 71.5 feet bgs <br /> in January,2008 to identify the base of soil petroleum hydrocarbon contamination and to determine <br /> if local groundwater had been impacted by petroleum hydrocarbons. Soi sample analytical sample <br /> results from soil samples collected during January 2008 from the three soil borings reported the <br /> presence of low level(<l 10 mg/kg) TPH-d and low-level(<100 mg/kg)TPH-mo in the upper 16.5 <br /> feet of the soil column adjacent to the former UST tank pit. No volatile organic compounds were <br /> reported to be present in the soil samples. <br /> A volume of initial petroleum hydrocarbon contaminated soil of approximately 400 to 700 cubic <br /> yards has been estimated to have been present prior to the UST removal. This contaminant mass was <br /> present in the subsurface_ from the surface to a maximum of 16.5 feet below ground surface. <br /> Maximum concentrations of TPH-d reported to be 9100 mg/kg. No volatile organic compounds <br /> were reported to be present. <br /> The average concentration of TPH-d in the soil mass that was excavated is estimated to have been <br /> 300 to 500 mg/kg based on,1998 and 1999 soil sample results. Soil borings drilled in January 2008 <br /> reported a maximum of 110 mg/kg of TPH-d. The site has undergone significant degradation of the <br /> petroleum hydrocarbon soil contaminant mass. <br /> Analytical sample results from the groundwater grab samples were reported to contain TPH-d at <br /> concentrations ranging from below analytical detection limits to a maximum of 150 ug/l. No volatile , <br /> organic compounds were found to be present in the water samples. <br /> A sensitive receptor survey was conducted:that indicated the nearest water supply well was the <br /> ST&E well located at 1282 Shaw Road, about 300 feet west of the former UST location. A water <br /> sample from this well was collected and analyzed for TPH-d, TPH-mo and volatile organic <br /> compounds. All analytical results were reported to be below analytical method detection limits. <br /> A review of site history and other nearby petroleum hydrocarbon sites indicated that the first <br /> water bearing zone in this portion of San Joaquin County is about 60 feet below ground surface. <br /> Groundwater flow direction is to the south to southwest at a low gradient. No other sites are <br /> Environmental\STE\PARSCR09102008.wpd 2 <br />