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GRANITE CONSTRUCTION, FRENCH CAMP r WKA No. 2088.04 December 2, 1993 Page 2 A more detailed discussion of the laboratory results and observations during tank removal is contained in our Soils Sampling and Testing report, dated May 12, 1992, on file with San Joaquin County Environmental Health Division (EHD). Based on analysis of samples obtained during removal of the USTs, a workplan was prepared January 28, 1993 to investigate the extent of soil and ground water contamination in the vicinity of the former diesel and unleaded gasoline USTs. Additionally, excavation was proposed to remove trace levels of motor oil contamination from beneath the former waste oil tank. In accordance with the workplan, 15 borings were constructed in the vicinity of the four former ,.. diesel and gasoline USTs and the former dispenser island. Two additional borings were constructed at an approximate 30° angle from vertical to evaluate soils beneath the former waste oil tank (site conditions prevented the excavation and removal of the remaining motor oil contamination). Additionally, three monitoring wells (MWI through MW3) were installed at the locations shown on Plate 2. Analytical results of soil samples obtained from soil borings in the vicinity of the four former underground storage tanks revealed moderate to moderately high concentrations of gasoline at depths ranging from approximately 15 feet to 25 feet below site grade. The area of �.. contamination was estimated to encompass approximately 9,500 square feet. We also estimated that remediation by excavation would require removal of approximately ten feet of "clean" overburden soil (estimated at 4,000 to 4,500 cubic yards) to access the contamination. The casing elevation of each monitoring well was surveyed and depth to ground water measurements were obtained. The ground water flow direction was calculated from these data to be toward the northeast. Analytical results of the ground water sample obtained from monitoring `1 well MW-3 revealed that gasoline contamination was present in the ground water beneath the site. Based on the laboratory analysis, we recommended the installation of three additional wells downgradient from the USTs to help delineate the lateral extent of contamination. The laboratory results of soil samples obtained from the two angle borings (B1 and B2) indicated that the soils beneath the 2,000-gallon waste oil tank located adjacent to the easterly side of the WALLACS•iCUHL Lo Er A=s�UCYA�E�11�iL.