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SITE CLOSURE EVALUATION REPORT Beacon station No.502 35 North Cherokee Lane Lodi,California Delta Project No. D093-907 of petroleum hydrocarbons in ground water have been reduced to background concentrations and no further remediation or monitoring of ground water is necessary. The Water Quality Control Plan, Central Valley Region, Sacramento River and San Joaquin River Basins (WQCP) dated December 1994, by the CRWQCB contains guidelines for evaluating sites for regulatory closure. The WQCP states in Chapter 4, Section 9 0) that soil cleanup levels are to be based on background concentrations of the individual constituents unless background levels are technologically or economically infeasible. It further states that where background concentrations are infeasible to achieve, soil cleanup levels are to be established to ensure that remaining constituents of concern will not cause ground water to exceed the applicable ground water cleanup standards or pose a threat to human health or the environment. It would appear that Ultramar has expended considerable resources and has utilized ' the best available technology to remove significant concentrations of petroleum hydrocarbons from the soil underlying the site; however, reducing concentrations of petroleum hydrocarbons in soil to background concentrations does not appear to be economically feasible. The relatively insignificant concentrations of toluene, ethylbenzene, and total xylenes which remain are present in soil at a depth of ' 26 feet bsg and ground water is present at a depth of greater than 50 feet bsg; therefore, it is very unlikely that the remaining petroleum hydrocarbons in soil would pose a threat to human health or the environment (ground water quality). It is anticipated that naturally occurring biological degradation of petroleum hydrocarbons will reduce the concentration of petroleum hydrocarbons in soil to non-detectable ' levels, if this has not already occurred. The Porter-Cologne Water Quality Control Act in Section 13267(b) provides that the Regional Water Quality Control Boards may require dischargers to submit technical or monitoring reports "provided that ' the burden, including cost of these reports, shall bear a reasonable relationship to the need for the reports and the benefits to be obtained from the reports." In Delta's opinion there is no need for, or additional benefit to be obtained from, further reporting of conditions at the site. ' For these reasons regulatory closure should be granted for this site, the existing ground water monitoring wells should be destroyed, and no further investigation or remediation should be required. In the event ' RPT 139.SJ s