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al y Fourth'Quarter 1996 Status Report 7 Former Discovery Chevrolet January 3, 1997 Previous Environmental Work i 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 9 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 SJCEHD'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 collected during 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 6f-,21. ,and 0.88 ppm, respectively. TPHg, Total _i Petroleum.Hydrocarbons as Diesel (TPHd),,and benzene were detected in the soil sample from the:waste oil excavation at'concentrations.of 31, 270 Wand 0.1.8 ppm, respectively. Tetrachlororoethene (72 parts per billion;'.or ppb),lead (7.8 ppm), and chromium (9.2 ppm} ` were also detected in this.sample ' Based on results of soil sample analyses from the 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 Plan (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 MW-2 (240 ppm). The benzene,con centrations 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. flaw 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 thesesamples 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 GS1 Report:No. 8146,701-1, Preliminary. Environmental Investigation Report, dated December 7;, 1994." , Depth-to-groundwater and chemical analytical data are,summarized in Table ' 8146.03 2 i I