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SITE CLOSURE REPORT <br /> General Mills, Inc <br />• ^_000 West Tumor Road <br /> Lodi, California <br /> Delta Project No D092-70$ <br /> Page 8 <br /> 3 4 2 Followinz Excavation <br /> To calculate the volume of hydrocarbons remaining in soil following excavation, the lateral extent of the <br /> remaining plume (shown as three separate areas) on Figure 11 was measured The vertical extent of <br /> hydrocarbons was assessed based on laboratory data collected during the tank removal and subsequent <br /> soil borings Cross-sections of the plume are shown on Figures 7 and 8 Utilizing the same assumptions <br /> (concentrations with depth and porosity) a remaining volume of up to 0 76 gallons of fuel oil, quantified <br /> as diesel No 6 may remain in place Calculation of the volume of hydrocarbons remaining in place are <br /> presented in Appendix B <br /> 4 0 DISCUSSION <br /> Analytical reports from environmental investigations performed at the site did not detect benzene in any <br /> of the analyzed soil samples Toluene, ethylbenzene, and total xylenes have been reported in three <br />. samples, two collected during the tank removal and one during subsequent drilling TPH as diesel has <br /> been reported in soil samples remaining in place at a maximum concentration of 990 ppm in soil boring <br /> SB-1 at 15 feet bsg This depth is immediately below the former tank excavation No soil samples <br /> analyzed below 17 5 feet bsg have reported detectable concentrations of any analyte Based on the <br /> investigations, it appears hydrocarbon containing soil is limited to the area between 15 and 18 feet bsg <br /> beneath the former tanks <br /> Ground water samples have been collected since May 1992 Initially, one year of quarterly sampling was <br /> performed Following the first year of sampling, the frequency was reduced to semi-annually Since <br /> ground water monitoring has been performed at the site, no analytes have been reported above the <br /> laboratory's limits of detection in any well <br /> 5.0 RATIONALE FOR CLOSURE <br /> The Water Quality Control Plan, Central Valley Region, Sacramento River and San Joaquin River Basins <br /> (WQCP) dated December 1994, by the California Regional Water Quality Control Board (CRWQCB) <br /> contains guidelines for evaluating sites for regulatory closure The WQCP states in Chapter 4, <br /> RPT137 SJS <br />