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Former Discovery Chevrolet <br /> September 26, 1995 <br /> Previous Environmental Work <br /> Based on information supplied by Ms. Nukes, we understand that the three USTs were <br /> removed in April 1993. Four soil samples were collected from the base of the gasoline UST <br /> excavation at depths of approximately 9 to 10 feet below ground surface (bgs), one soil <br /> sample was collected from beneath the product dispenser at approximately 5.5 feet bgs, and <br /> one soil sample was collected from the base of the waste oil UST excavation at <br /> approximately 7.5 feet bgs. Groundwater was not encountered during UST removal. <br /> Information supplied by SJCEHD indicates that the product piping that ran from the gasoline <br /> USTs to the dispenser, located inside the service bays, was left in place beneath the concrete <br /> apron outside the shop building.. <br /> Petroleum hydrocarbons were detected in all soil samples collected during the UST removal. <br /> Soil samples collected from the gasoline UST excavation contained Total Petroleum <br /> Hydrocarbons as gasoline (TPHg) at concentrations ranging from 920 to 4,400 part per <br /> million (ppm). Benzene was detected in all these soil samples at concentrations ranging from <br /> 5.9 to 39 ppm. Total lead was detected' in two of these soil samples at concentrations of 19 <br /> and 4.0 ppm. TPHg and benzene were detected in the soil sample collected beneath the <br /> product dispenser at concentrations of 21 and 0.88 ppm, respectively. TPHg, Total <br /> Petroleum Hydrocarbons as Diesel (TPHd), and benzene were detected in the soil sample <br /> from the waste oil excavation at concentrations of 31, 270 and 0.18 ppm, respectively. Lead <br /> and chromium were detected in this sample at concentrations of 7.8 and 9.2 ppm, <br /> respectively. <br /> Based on results of soil sample analyses from the UST removal, GSI performed a <br /> preliminary site assessment to further evaluate hydrocarbons in the soil and to evaluate <br /> whether hydrocarbons had impacted groundwater beneath the site. Three on-site <br /> groundwater monitoring wells were installed at the locations shown on the Site Plan (Figure <br /> 2) in September 1994. One soil sample from approximately 10 bgs in each soil boring was <br /> submitted for analysis. TPHg were.detected in the soil sample from boring MW-1 (340 <br /> ppm) and MW-2 (240 ppm). The benzene concentrations in these samples were 3.9 and 2.4 <br /> ppm, respectively. Petroleum hydrocarbons were not detected in the soil sample from boring <br /> MW-3. Groundwater in the newly installed wells was measured between 9.97 and 10.49 feet <br /> bgs, and appeared to flow north-northeast at a gradient of 0.003. Floating product was not <br /> observed in the monitoring wells. TPHg was detected in thegroundwater sample collected <br /> from well MW-1 (640 parts per billion, or ppb) and MW-2 (7,200 ppb). The benzene <br /> concentrations in these samples were 35 and 370 ppb, respectively. Petroleum hydrocarbons <br /> were not detected in the groundwater sample collected from well MW-3. Results of that <br /> investigation were reported in GSI Report No. 8146.701-1, Preliminary Environmental <br /> Investigation Report., dated December 7, 1994. Depth-to-groundwater and chemical <br /> analytical data are summarized in Table 1. <br /> 8146.02-3 2 <br /> k <br />