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1 RR I? Beacon Station No.696 2448 West Kettleman Lane Lodi,California ' Delta Project No.D093-916 Page 6 5-1 MASS BALANCE CALCULATIONS,SOIL ' During August 31 through September 8, 1994, six soil confirmation borings were advanced at locations indicated on Figure 4. Laboratory analysis of samples submitted reported TPH as gasoline to be below the laboratory's limit of ' detection of 1 mg/kg in all samples except those collected from confirmation borings CB-4, CB-5, and CB-6. Confirmation boring CB-5 had TPH as gasoline reported in the sample at 45 feet bsg at 39 mg/kg and below the laboratory's detection limits in all other samples from the boring. Confirmation boring CB-6 had TPH as gasoline reported in the sample at 45 feet bsg at 7.4 mg/kg and below the laboratory's detection limits in all other samples from the boring. ' Based on soil boring results and sample analyses conducted, it has been calculated that 1,300 gallons of TPH quantified as gasoline and 9.8 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 B. The initial soil borings indicated that impacted soil was encountered from 2 to 49 feet bsg. The impacted soil was subdivided into five ten-foot thick intervals. These subdivided intervals are illustrated on Figure 8. Following approximately 5 years of SVE operation, it was estimated that approximately 557.5 gallons of TPH as gasoline and 0.11 gallons of benzene remain in soil underlying the site. This estimate is based on the results from confirmation soil borings CB-1 through CB-6. The calculations illustrating petroleum hydrocarbon impacted soil remaining following remediation are included in Appendix C. The residual layers of impacted soil used to calculate the remaining mass balance are illustrated in Figure 12. The mass balance estimation indicates a 57 percent reduction in TP14 as gasoline and a 99 percent reduction of ' benzene at the site in the soil. The percent reduction estimations for TPH as gasoline and benzene are included in Appendix D. 5.2 MASS BALANCE CALCULATIONS.GROUND WATER Based on the January 11, 1988, quarterly ground water monitoring data, approximately 13.6 gallons of TPH quantified as gasoline and 1.94 gallons quantified as benzene were present in ground water at that date. The ' RPTOQ1.916