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_ ... .... .. .. .. Third Quarter 1997 Status Report - Former Discovery Chevrolet r.. October 17, 1997 Previous Environmental Work Based on information supplied by Ms. Nokes, we understand that the three USTs were` removed in April 1993. Four soil samples were collected from the base of the gasoline UST excavation at depths of approximately 4 to 10 feet below ground surface (bgs), 'one soil sample was collected from beneath'the.product dispenser at approximately 5.5 feet bgs, and one soil sample was collected from the base of the waste oil UST excavation at approximately 7.5 feet bgs. Groundwater was not encountered during UST removal. Information supplied by SICEHD indicates that the product piping that ran from the gasoline USTs to the dispenser, located inside the service bays, was left in place beneath the concrete apron outside the shop building. Petroleum hydrocarbons were detected in all soil samples collectedduring the UST removal. Soil samples collected from the' gasoline UST excavation contained Total Petroleum Hydrocarbons as gasoline (TPHg) at concentrations ranging from 920 to 4,400 part .per million (ppm). : Benzene was detected in all these soil samples at concentrations ranging from. 5.9 to 39 ppm. Total lead was detected in two'of these soil samples at concentrations of 19 and 4.0 ppm. TPHg and benzene were detected in the. soil sample collected beneath the product dispenser at concentrations of 21 and 0.88. ppm, respectively. TPHg, Total r=. Petroleum Hydrocarbons as Diesel (TPHd), and,benzene were detected in the soil sample from the waste oil excavation at concentrations .of 31, 270 and 0.18 ppm, respectively. Te'trachlororoethene (72 parts per.billion, or ppb), lead (7.8 ppm), and chromium (4.2 ppm). were also detected in this sample. Based on results of soil sample analyses `from thea UST removal, GSI performed a preliminary site assessment to further evaluate hydrocarbons in the soil and to evaluate Whether hydrocarbons had impacted groundwater beneath. the site. Three on-site groundwater monitoring wells were installed at the,locations shown on the Site PIan (Figure 2) in September 1994. One soil sample from-approximately 10 bgs in each soil boring was submitted for analysis. TPHg were detected in the soil sample from boring MW-1 (340 ppm) and MW72 (240 ppm). The benzene concentrations in these samples were 3.9 and 2.4 ppm, respectively. Petroleum hydrocarbons were not detected in the soil sample from boring MW-3. Groundwater in the newly installed wells was"measured between 9.97 and.10.49 feet bgs, and appeared to flow north-northeast at a gradient.of 0.003. Floating product was not observed in the monitoring wells.' TPHg was detected in.the groundwater sample collected from well MW-1 (640 parts per billion, or ppb) and MW-2 (7,200 ppb). The benzene concentrations in these samples were 35 and 370 ppb, respectively. Petroleum hydrocarbons were not detected in the groundwater sample collected from well MW-3. Results of that investigation were reported in, GSI Report No. 8146.701-1, Preliminary Environmental . Investigation Report, dated December 7, 1994. Depth-to-groundwater and chemical analytical data are summarized in Table 1. , 8146.04-3 2