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Third Quarter 199.8 Status,Report'—Former Discovery Chevrolet k, J. September 14, 1998 i 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 ppin. TPHg arid-benzene were detected in the soil-'sample collected beneath the product dispenser at concentrations of, 21 'and 0.88 ppm,, respectively. TPHg, .Total - 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., `.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 . 12) in.Se tember 1994. One soil sample' from approximately b s 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 ppiri).. The benzene.concentrations in these samples were 3.9 and 2.4 pprn, respectively. Petroleum hydrocarbons.were not detected in the soil sample from boring ng 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 T.able 1. . ` Quarterly monitoring and sampling of -the monitoring wells begin . in March 1995.. 'Historically, depth to groundwater, has fluctuated between 9.25 -and 11.53 feet bgs: - Groundwater appears to flow toward the north-northwest at a gradient of approximately : 0.003 to 0:005. Floating'product has not been observed in the monitoring wells.: TPHg, BTEX, or Oil and Grease have riot been detected. in well MW-3. TPHg or benzene have nev.er been detected in-well MW-5'. TPHg concentrations in wells MW-1 and MW-2 have ranged from '60 to 17,000 ppb, and benzene concentrations have ranged from 1:1,to•3,100 948146.45-7 2