SITE INFORMATION AND CORRESPONDENCE

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FROM 1997 1-14 17:43 #888 P.04/24 Februan- 14. 1997 Pa,e A well survey (EA. 1985) was performed for the site using data from the California State Department of Water Resources (D\WR). Using these data, seven water wells were identified within 1/2 mile of the site. The closest well is a domestic well located at 919 Center Street approximately 1,700 feet south (upgradient) of the Chevron station (Figure 1). Stockton community water supplies were also surveyed as part of defining the physical characteristics of the site. Stockton receives its drinking water supply from the surface water of New Hogan Reservoir and groundwater at various locations throushout the City and San Joaquin County. Based on a list of active water-supply wells provided by California Water Services, there are two additional groundwater-supply wells located between a 1/2-to 1-mile radios of the site. These wells are located on Ellis Street east of Bonnie Lane, and at Commerce Street and Wyandotte Street, A list of private and municipal wells, and available well construction detail information is presented in Table 1. Well locations are shown on Figure 1. PREVIOUS SITE INVESTIGAnONS November 18, 1987. A soil vapor contaminant assessment(SVCA)was performed on site by EA. Ten sample points were driven to depths ranging from 3 to 8 feet bgs at locations in the area of the waste-oil tank, dispenser islands, and the gasoline UST complex. Petroleum hydrocarbons were not detected above i part per trillion (ppm)in the 21 soil vapors samples collected. February 24, 1988. One 1,000-gallon fiberglass waste-oil UST and three 10,000-gallon fiberglass gasoline USTs were excavated and removed during the site demolition activi- ties. No holes were observed in any of the tanks. Laboratory results indicated that the soil sample collected beneath the waste oil tank (Sample WOF#1)reported 26 ppm of high-boiling point hydrocarbons and 10 ppm of low-boiling point-hydrocarbons. No chlorinated solvents, benzene, toluene, ethylbenzene, and xylenes(BTEX compounds), or polychlorinated biphenyls (PCBs) were detected (Table 2). After removing the three 10,000-gallon gasoline USTs,the northeast portion of the tank pit was overexcavated to a depth of 25 feet bgs- One soil sample(AOP#1)was collected from the bottom of the gasoline tank overexcavation and reported high- and low-boiling point hydrocarbons at 55 and 340 ppm,respectively, but no benzene was detected (Table 2). September 1988. .Oil Equipment Services performed further overexcavation to a maximum depth of approximately 26 feet bgs in the northeast corner of the tank pit. Concentrations of petroleum hydrocarbons ranged from non detectable to 6240 ppm TPPH-g. According to data obtained from the SJCEHD,the samples were analyzed by 32013379+ciostRE3