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1II AtilntlL Ridhheld Comp Ind 3 ARCO 595 6100 North ni w-ty 99 SCOL Wn CA oLtober 2 2000 . ranging from 38 8 ppb to 84 4ppb Groundwater analytical data is presented in Table 2 and is shown on Figure 2 Field and laboratory procedures are presented as Attachment C Groundwater sampling parameters are included on the field sheets in Attachment E The wells were surveyed relative to mean sea level by Tom Morrow Surveying, a California licensed surveyor Attachment F contains the surveyor's site plan showing the locations and elevations of the wells Groundwater Flow Direction Depth to groundwater at the site ranged from 55 72 feet bgs to 57 65 feet bgs Based on monitoring data collected on June 16, 2000, groundwater flow was to northwest with a gradient of 0 007 (Figure 3) Well Survey SECOR performed a water well survey to identify the location of permitted water supply wells within a 1/2-mile radius of the site The water well survey consisted of a review of California Department of Water Resources (DWR) files for the area Additionally, SECOR contacted the City of Stockton and San Joaquin County Public Works Department, which are the local water purveyors According to these sources, no municipal wells are operated in the survey area by City of Stockton and San Joaquin County Public Works Department A total of five wells were located within the search area An active domestic well is located on the southwest corner of the ARCO property Construction details of the well are unknown Well survey data is presented in Table 3, and well locations are shown on Figui e 4 Stockpiled Soil Approximately 10 cubic yards of soil generated during the installation of the wells was stockpiled onsite One composite sample (4 sleeves to I sample) was collected from the stockpiled soil and analyzed for TPHg, BTEX, MtBE, and total lead No compounds were detected Soil was disposed of at Vasco Road Landfill in Livermore, California Stockpiled soil analytical data is presented in Table 4 SUMMARY OF FINDINGS • TPHg was detected in I of 41 samples analyzed at a concentration of 1 88 mg/kg (B-3@40')40') Benzene was detected in 4 of 41 samples analyzed at a maximum concentration of 0 0645 mg/kg (B-3@40') MtBE was detected 2 of 41 samples analyzed at a maximum concentration of 0 308 mg1kg (MW-4@60') TAME, D1PE, EtBE, TBA, EDB and 1,2-DCA were reported as nondetectable in all samples analyzed • e TPHg, benzene, and MtBE were reported in groundwater samples from each well at maximum concentrations of 8,910 ppb, 2,3 l Oppb, and 3,200 ppb, respectively TBA and TAME were reported in well MW-4 077 41941 1"O/M111 Imt III dui