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APPENDIX BIRISK BASED CORRECTIVE ACTION TIER 1 AND '[ 2 ANALYSIS SITE CLOSURE EVALUATION REPORT Former Beacon Station No 695 900 South Cherokee Lane Lodi, California Delta Project No D093-915 Page 9 influent petroleum hydrocarbon concentrations decreased to a level at which economic and efficient operation of the catalytic oxidizer could no longer be achieved Table 9 presents a summary of petroleum hydrocarbon removal for the period of May 1993 through February 1996 During the period that the SVE system operated (July 1991 to February 1996) approximately 122,690 pounds (19,885 gallons) of vapor equivalent gasoline has been removed from soils underlying the site Figures 18 and 19 show the approximate lateral extent of vadose soil containing petroleum hydrocarbons quantified as gasoline and diesel following remediation Figure 20 shows the traces of cross-sections on Figures 21 through 24 showing the approximate vertical extent of vadose soil containing petroleum hydrocarbons quantified as gasoline and diesel following remediation It is worth noting generally speaking that according to West laboratory all the conformation samples collected in March 1996 (SB-1 through SB-6) were depleted in the volatile fraction even in samples that reported TPH as gasoline in the thousands of mg/kg range Also it appears that the most highly elevated levels of TPH as gasoline and TPH as diesel are in less permeably materials (i a silts and clays) 5.0 MASS BALANCE CALCULATIONS SOIL Based on soil boring results and sample analyses conducted, it has been calculated that 17,306 gallons of TPH quantified as gasoline and 18 gallons quantified as benzene were present in soil underlying the subject site prior to SVE remediation The calculations estimating the mass of petroleum hydrocarbon impacted soil prior to remediation are included in Appendix D The initial soil borings indicated that impacted soil was encountered from the surface to 69 feet bsg The impacted soil was sub-divided into seven ten-foot thick intervals These subdivided intervals are illustrated on Figure 25 Following approximately 2 years of soil vapor extraction system operation, it was estimated that approximately 1,839 gallons of TPH as gasoline and 2 7 gallons of benzene remain in soil underlying the site This estimate is based on the results from confirmation soil borings SB-1 through SB-6 As noted RPT001 915