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5ECONO QUARTERLY GROUNDWATER MOMTOFONG R BWT OF 1992 <br /> 1605 South E3 Dorado Street Stockton Callfomla <br /> On July 2 and 3, 1991, Aegis conducted sod boring, sampling, and installation of <br /> monitoring wells MW-1, MW-2, and MW-3 (Figure 2) Results of the investigation were <br /> I reported by Aegis to Exxon in a "Phase I Subsurface Investigation Results Report," dated <br /> September 13, 1991 <br /> IOn December 17, 1991, the top-of-casing well elevations for MW-1, MW-2, and MW-3 <br /> were resurveyed by Tom O Morrow, Inc , of West Sacramento, California <br /> 4.0 GROUNDWATER MONITORING <br /> 41 Groundwater <br /> I On April 22, 1992, Aegis personnel collected measurements of the depths to groundwater <br /> in wells MW-1, MW-2, and MW-3 Since January 17, 1992, groundwater has risen in all <br /> three wells (Figure 3) ranging from 1 06 to 1 08 feet (Table 1) On the bass of the <br /> April 22, 1992, measurement, groundwater is estimated to flow to the east at an average <br /> gradient of 0 0008 ft/ft Figures 4 is a potentiometric surface map of the shallow <br /> water-bearing zone on April 22, 1992 <br /> Previous groundwater levels are summarized in Table 1 Ali groundwater elevation <br /> measurements were made from the referenced wellhead elevations, measured to the <br /> nearest 0 01 foot, and conducted according to the Aegis standard operating procedures <br /> (SOP) included as Appendix A <br /> 4.2 _Water Sampling and Analysis <br /> On April 22, 1992, Aegis personnel collected groundwater samples from the three wells <br /> at the site The samples were collected according to the Aegis SOP included in <br /> Appendix A, and delivered under chain-of-custody to Pace Laboratories, Inc , of Novato, <br /> California, a state-certified analytical laboratory The samples were analyzed for <br /> I concentrations of a) TPH, as gasoline, by EPA Method 8015, b) BTEX by EPA <br /> Method 8020, and c) total lead by EPA Method 7421 The analytical results are <br /> summarized in Table 2 The analytical reports and chain-of-custody form are included in <br /> Appendix B Concentrations of TPH, as gasoline, and BTEX reported in Table 2 are also <br /> shown on Figure 5 <br /> I <br /> 91-044A OMR 7 <br /> I <br />