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Jonas & Associates Inc. <br /> ' previously Both wells were constructed using 2-inch casings with 0 O1-inch slots <br /> (PG&E, 1988) <br /> ' Figures 3-3 and 3-4 are potentiometric surface map showing relative groundwater <br /> elevation contour (solid) lines interpolated from water level measurements taken on <br /> January 11, 1988 and February 26, 1988 Extrapolated water levels are depicted <br /> ' with dashed contour Imes Hydraulic gradient analysis of the water level data <br /> collected at the facility from January to March 1988 indicated that groundwater flow <br /> beneath the Site was in a north-northeasterly direction This information <br /> substantiated conclusions formed from the soil vapor survey and implied that, <br /> unless reversals in hydraulic gradient had occurred in the past, the elevate levels of <br /> gasoline hydrocarbons found in soil at OW-3 (south of the tank site)were not related <br /> to the former UST Hydrocarbons detected in this area were reported to be <br /> probably the result of a small isolated spill (PG&E, 1988) <br /> ' 3 2 1 TPH-G - 1988 Analytical Results <br /> ' Results of chemical analyses performed on soil samples collected during this <br /> investigation are summarized in Table 3-5 Figure 3-5 shows the estimated <br /> horizontal TPH-G isoconcentration lines for soils in the vicinity of the former UST, <br /> based on results of the 1988 investigation (PG&E, 1988) <br /> TPH-G were detected at levels under 1,000 ppm (to a maximum concentration of <br /> 840 ppm) in soil samples collected during this investigation The highest <br /> concentrations were found in soil located within a few feet to the north-northeast of <br /> the former UST site at depths near the encountered water table (approximately 7 <br /> feet below ground surface), and dropped off rapidly above and below this level Low <br /> levels of TPH-G were detected in soils approximately 80 feet to the northeast of the <br /> former UST location (OW-5) <br /> ' It was estimated that, with the possible exception of a very small volume of soil <br /> immediately adjacent to the former UST location, no soils had TPH-G <br /> concentrations at or above 1,000 ppm <br /> Results of laboratory analyses performed on groundwater samples collected during <br /> ' this investigation are summarized in Table 3-6 Figure 3-6 shows the estimated <br /> horizontal TPH-G isoconcentration lines for groundwater in the vicinity of the former <br /> UST, based on results of the 1988 investigation TPH-G were detected in <br /> ' groundwater samples collected during this investigation, approximately 10 feet to <br /> 10 <br />