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r � • <br /> ' 9 - Zone of Influence of Remediation System - Remediation by over excavation, <br /> • treatment and disposal of eight yards of soil under direction of San Joaquin County <br /> rEnvironmental Health Department <br /> 10 - Reports, Los and Unauthorized Release Reports—Logs of monitoring wells <br /> r MW I, MW3 and MW3, soil and groundwork data presented in Soil Contamination Map <br /> Sail and Groundwater Investigation Report - Manteca Unified School District, <br /> Agricultural Shop Building, 2901 E Louise Avenue, Manteca, California, M J <br /> r Kloberdanz and Associates, February 3, 2002 (this report) Log exploratory boring B 1 by <br /> others (Kleinfelder, November 5, 1998) Unauthorized Release Report on file with San <br /> Joaquin County Environmental Health Department <br /> rI 1 Best Available„Technology- Best available technology for shallow impacted soil was <br /> determined to be source removal by over excavation and treatment of impacted soil <br /> r12 Reasons for Non Attainment of Background Concentrations - Residual soil <br /> contamination does not pose a threat to the waters of the state <br /> r13 - Mass Balance Calculation — Diesel contamination was detected in only four soil <br /> samples collected for Iaboratory analysis at the location of the former underground <br /> r storage tank Diesel contamination was not detected at depths greater than 17 feet and <br /> only in the original tank excavation Diesel contaminated groundwater was detected is an <br /> exploratory boring constructed through the tank pit The very low concentrations of <br /> r• diesel hydrocarbons are probably soil contamination carried into the aquifer through the <br /> drilling process <br /> rThe contaminant mass estimate is based on the soil conta Z�on� ecognized in a single <br /> boring at the former location of the underground storage tank The lateral limit is <br /> provided by MW3 approximately 10 feet the west Assuming a total plume area of 176 ftz <br /> r (15 ft diameter) with a localized hot spot of 63 5 ft2 and extending vertically 2 feet below <br /> the base of the tank cavity, the following estimates of remaining contaminant mass were <br /> calculated (Table 1) <br /> r <br /> Ta ti ated Mass of Remaining Fuel Contaminants <br /> r Tph - t enzene To ueneL Ethyl Benzene Xylenes MTBE <br /> diesel <br /> Mass{lb 2 9529 �0 0000 0 000 0 000 0 000 0 000 <br /> rThe Inas estimates pre nted above are, in all probability, greatly inflated due to the <br /> effect of he spacing the control sampling locations Additional soil samples at <br /> r Iocations oser t t e tank pit would reduce the apparent area of contamination and the <br /> resulting contaminant mass calculation Pretreatment contaminant concentrations are <br /> not available <br /> r <br />