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Environmental Assessment Report 3 Chevron U.S.A. Products ComE2ny, 139 South Center Street,Stockton,CA January 25,19% with flush threads. A#3-sand filter pack was installed in the annulus from the bottom of the borehole to 2 feet above the top of the well screen, followed by a well seal consisting of a 2-foot thick bentonite layer overlain by neat cement(grout) to ground surface. The well was secured by a locking expandable well cap and fitted with a traffic-rated well box set in concrete. Details of well construction are presented on the drilling log (Appendix B). The completed well and existing wells were surveyed by Morrow Surveying for horizontal position and elevation relative to mean sea level datum using a City of Stockton benchmark as a reference (Appendix C). Elevations were obtained for tops-of-well-casing and the well box rims. Figure 1 shows the location of the new well relative to previously installed monitoring wells at the site. Figure 1 shows the location of the new well relative to previously installed monitoring wells at the site. On December 28, 1995,well MW-7 was developed by Groundwater Technology using a PVC bailer. Prior to development activities, depth to water was measured in the new well relative to top-of-well- casing to determine the static water level (Table 1). The new well was manually developed using a surge block and bailer in order to remove fine-grained sediment. Approximately 10 well volumes of water was extracted from the well. All water generated during development was placed into appropriately labeled U.S. Department of Transportation-approved 55-gallon drums and transported to the Chevron Richmond refinery for recycling. 3.0 RESULTS OF SOIL SAMPLE ANALYSES Laboratory analytical results for soil samples collected on November 29 - December 1, 1995, are summarized in Table 2. The highest concentrations of hydrocarbons among all analyzed samples were 1.4 milligrams per kilogram (mg/kg, equivalent to parts per million, or ppm) benzene and 640 mg/kg TPH-G in the sample collected at a depth of 40.5 feet BGS from boring SB-9, Copies of laboratory analyses reports and chain-of-custody manifests for the soil samples collected November 29 - December 1, 1995, are included in Appendix D. 4.0 RESULTS OF "GRAB" GROUNDWATER SAMPLE ANALYSES Table 3 presents a summary of laboratory analytical results for"grab"groundwater samples collected on November 30 and December 1, 1995. Concentrations of TPH-G were reported at 1,900,000 micrograms per liter (ug1L, equivalent to parts per billion, or ppb) in sample GW-7A, and at 260,000 ug1L in sample SB9-GW, although concentrations of benzene in each of samples GW-7A and SB9-GW 006BEAq,*ptrChv 64r � _ =11TECHNOLOGY