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eN <br /> er IAN <br /> I <br /> .0 S y OF PREVIOUS INVESTIGATIONS <br /> Previous assessments at the facility have included 1) ERM West <br /> (September 1989), 2) Kleinfelder, Inc. - (May and June, 1490), and 3) <br /> Leedehill-Herkenhoff, Inc. (October 1990) , These assessments have <br /> identified a petroleum hydrocarbon plume associated with the <br /> previously excavated product storage tanks at the facility. <br /> 4.1 Previous Investigations Phases I - IIx <br /> In September 1989, ERM - Wast of Sacramento, California, conducted a <br /> �- Phase Y Environmental Site Assessment which included a site visit and <br /> a survey of surrounding land uses. <br /> A second phase of investigation included a soil gas survey around the <br /> former storage tank area and pump islands by Kleinfelder, Inc. Soil- <br /> gas samples were collected from 15 locations at the site and analyzed <br /> for total hydrocarbons, and benzene, toluene, ethylbenzene and <br /> xylenes by gas chromatography. Findings from this investigation <br /> determined that.,petroleum hydrocarbon concentrations were detected in soil-gas from the area where the former tanks had been excavated. <br /> Petroleum hydrocarbons were also detected in soil-gas samples up to <br /> 60 feet west and 50 feet southeast of the tan' excavation and <br /> adjacent to the underground piping which leads from the tank areE. to <br /> the easterly pump island. A detailed summary of findings cou be <br /> found in Kleinfelder's Soil-Gas and Storage Tank Assessment:•report <br /> dated June 14, 1990. <br /> A third phase of site investigation was performed by Leedshill- <br /> Uerkenhoff, Inc. in which eight soil boringsand three groundwater <br /> monitoring wells were drilled and sampled to determine subsurface <br /> conditions at the site (Figure 5) . In addition to the gasoline <br /> plume, <br /> the used-oil tank failed a precision tank test on June 5, <br /> 1990. The contents of the used-oil tank were removed and-disposed-of- <br /> "--- dank inlets were then capped and the tank has been out <br /> Of service since that time. Lithologic logs from the soil borings <br /> and monitoring wells are included as Appendix I. Soil .samples were <br /> ... - Neper-Paint Property _ 473 <br /> nAPnss�.xrP 3 <br />