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Well Installation Report ARCO Facility No.5469 Stockton., California Page 3 Monitoring wells were developed on June 21, 2000 using a surge block and groundwater pumping. On June 23, 2000, Delta returned to the site to measure water levels and collect 1� urge groundwater sam les. A disposable Teflonrm bailer was used to collect each groundwater sample. The groundwater sampling field data sheets are included in Attachment B. Field data sheets fromm well development and groundwater sampling are also presented in Attachment B. Analytical results of monitoring well groundwater samples are presented in Table 2. Certified analytical reports and chain-of-custody documentation are presented in Attachment C. Developed wells will be incorporated into a quarterly groundwater monitoring program. Morrow Surveying Inc. of West Sacramento, a California licensed professional land surveyor, established top-of-well-casing mean sea level. elevations in July 2000. Well casing elevations were established to the nearest O.OI-foot, referenced to City of Stockton Benchmark 492, elevation 16.64 feet Laboratory Analysis The groundwater and selected soil samples were analyzed by Sequoia Analytical, Inc. (Sequoia), . a California Department of Health Services-certified laboratory. Strict chain-of-custody procedures were followed from the time the soil samples were collected until the time the samples were handed over to the laboratory. The groundwater samples and selected soil samples were analyzed for TPHG using USEPA Method 8015/8020 DHS/LUFT, and benzene, toluene, ethylbenzene, and total xylenes (BTEX) using USEPA Method 8260A. In addition, select samples were analyzed for fuel oxygenates methyl-tert butyl ether (MTBE), tert-butyl alcohol (TBA), di-isopropyl ether (DIPE), ethyl tert-butyl ether(ETBE), tert-amyl methyl ether(TAME); and for methanol, ethanol, I,2-dichioroethane (1,2-DCA), and ethylene dibromide (EDB) using EPA Method-8260A-00A Soil sample analytical results are presented in Table 1 and groundwater samp e-analytical results are presented in Table 2. The certified analytical results with chain-of- custody documentation are included in Attachment C. Discussion of Findings The soil borings primarily encountered clayey silt, silt, and silt with sand from ground surface to 61.5 feet bgs (maximum depth explored). A silty sand layer, approximately 4 feet thick was encountered at well locations MW-1, MW-3, and MW-4 at depths ranging between approximately 38 and 53 feet bgs. During drilling, groundwater was encountered between approximately 37 and 41 feet bgs. Figure 3 presents two geologic cross sections of the site. Surface traces of cross-sectional profiles are shown on Figure 2. . Soil samples collected for laboratory analysis from well locations MW-1, MW-2, and MW-3 did not contain TPHG, BTEX, or fuel oxygenates above the laboratory detection limits. Methanol +I d'