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1 <br /> FINAL FEMEDtA710N PLAN <br /> 1399 East Yosemite Avenue Manteca CaOornia <br /> ' 2 2 Subsurface Utilities <br /> Underground utilities are present beneath the site The locations are shown on Figure 2 <br /> ' Prior to beginning fieldwork, Underground Service Alert will be contacted and the <br /> underground utilities will be marked <br /> ' 2.3 Soil Conditions <br /> The soil profile consists of a yellowish-brown, fine- to medium-grained silty sand This <br /> sand is underlain by fine- to coarse-grained sand that ranges in color from white to dark <br /> yellow-brown This sand is underlain by dark yellow-brown, fine-grained silty sand and <br /> clayey silt This unit is, in turn, underlain by a silty clay Beneath the clay is a fine- to <br /> ' medium-grained sand <br /> 2 4 Petroleum Hydrocarbons in Soil <br /> ' Analytical results obtained during the site investigation indicate the soil beneath the site <br /> contains concentrations of a) benzene, toluene, ethylbenzene, and total xylenes (BTEX), <br /> ' and b) total petroleum hydrocarbons (TPH), as gasoline To date, a total of twenty soil <br /> samples from sod and monitoring well borings drilled by ETS, Delta, NGA, and Aegis have <br /> been submitted and analyzed for BTEX and TPH, as gasoline Table 1 summarizes soil <br /> analytical results collected to date An inferred zero line of petroleum hydrocarbons in soil <br /> was included in Aegis' "Problem Assessment Report," dated November 12, 1991 <br /> ' The estimated quantity of TPH, as gasoline, in soil is 1,924 pounds This estimate was <br /> derived by plotting soil sample analytical results, collected during the investigation, on soil <br /> ' depth interval maps and contouring TPH concentrations as shown in Figures 3 and 4 <br /> Concentrations within a 5-foot-thick interval of soil, centered between the 15 and 20-foot <br /> j depths, were multiplied by the area within each of the respective contour intervals The <br /> TPH concentration at the point midway in the contour interval area (i e , the average <br /> ' concentration) was used to calculate the volume of TPH, as gasoline, for the particular <br /> area between the contours The resulting volumes of TPH were then summed to derive <br /> ' the total estimate of TPH in the soil This estimate will be used as a guide for evaluating <br /> the efficiency of remedial actions at the site (Appendix A) <br /> 1 <br /> 149 <br /> 90-098F RPT -3 <br />