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e\P%iedA5092\gWMV--P <br /> 10 UN'I ROIIDUMOIC <br /> The site is a concrete and asphalt paved truck fueling facility dispensing regular and <br /> unleaded gasoline and diesel fuel from sic fuel islands (Figure 1 - Site Plan w/ Ground- <br /> Water Elevation Data). The underground tank cluster hes east of the fuel islands and <br /> consists of five tanks: two 10,000-gallon diesel tanks manifolded together, one 8,000-gallon <br /> diesel tank, one 8,000-gallon regular gasoline tank, and one 7,500-gallon regular gasoline <br /> tank. 'There is also a 2,001)-gallon unleaded gasoline tank approximately 30 feet south of <br /> the larger fuel island in the center of the site. <br /> A site assessment was requested by the San Joaquin County Department of Public Health <br /> Services/Environmental Health Division (PSIS) because of tank testing failures and <br /> unauthorized fuel releases at the site. In May 1990, Environmental Science & ]Engineering, <br /> Inc. (ESE) drilled and sampled soil borings around the product lines and underground fuel <br /> assess the vertical and lateral extent of hydrocarbons in the soil. The results of this <br /> tanks to ass y <br /> investigation are presented in ESE's "Report of Site Assessment", dated June 14, 1990. <br /> Figure 2 - Approximate Extent of Soil Containing Hydrocarbons shows that hydrocarbons <br /> extend to at least 50 feet deep, but are apparently restricted to the area around the product <br /> lines and underground tanks. Because of the depth of hydrocarbons in the subsurface soil, <br /> ti <br /> a ground-water investigation was recommended. <br /> a <br /> 2.0 GROUND-WATER INVESTIGATION <br /> One ground-water monitoring well, UST-1 was drilled and sampled on September 20, 1990 <br /> downgradient and within ten feet of the area of deepest penetration of hydrocarbons in the <br /> soil (Figure 2), following a revised workplan approved by San Joaquin County Department <br /> of Public Health Services, Environmental Health Division. <br /> s <br /> 2.1 Drilling and Soil Sampling Procedures <br /> Well UST-1 was drilled with 10-inch diameter hollow-stem augers for construction of a 4- <br /> inch diameter monitoring well. Soil samples were obtained at 10-foot intervals in three b- <br /> 1 <br />