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INFerfifflar.c. SACRAMENTO 2.4 Geohydrolagy According to the most recent ground water contour map available to the Stockton Department of Public Works, ground water is present at a depth of approximately 60 feet below the surface, which is approximately 12 feet below MSL. The ground water flow direction is to the west. Ground water is used for agricultural purposes throughout the rural area surrounding the Pacific Bell facility. The nearest ground water well is located 50 feet south of the tank excavation site and is used by Pacific Bell in their facility operations. The exact depth of water that the well is producing from has not been made available to Versar. 3.0 SUMMARY OF PREVIOUS WORK In April , 1988, a 1,000-gallon underground diesel storage tank located along the southwest side of the building at the Pacific Bell Stockton facility was removed by LBME Corporation. The tank had been in place since 1964 when the site was first developed and had reportedly contained diesel fuel during its entire history. During the tank removal , two soil samples were taken from beneath the tank in the excavation pit, after which the excavation was filled. The soil samples were analyzed by Eureka Laboratories, Inc. , for TPH using EPA Method 8015M and for benzene, toluene, ethylbenzene, and xylene (BTEX) using EPA Method 8020. Laboratory analysis for TPH of soil samples one and two identified diesel fuel , at levels of 2,980 mg/kg and 1,000 mg/kg, respectively. Sample one also contained 0.013 mg/kg of xylene and 0.015 mg/kg of ethylbenzene, while sample two contained 0.0120 mg/kg of xylene and 0.025 mg/kg of ethylbenzene. The chain of custody and laboratory analytical results are included in Versar's Site Assessment report which is enclosed here as Appendix A. The results of the laboratory analyses of the soil samples were reported to the SJLHD in a report from LBME Corporation dated May 12, 1988. Included in the LBME report was a work plan for preliminary 6