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USA 65 Qtr report 7/21/92 • Methods and Procedures The ground water was sampled in six monitoring wells by a Western Geo-Engineers (WEGE ) geologist, working directly under the supervision of California Registered Geologist #3037 . Using a resistance probe, WEGE personnel measured the depth to ground water prior to sampling each well . Each well was purged before collecting water samples. MW1, MW2, MW3, MW5 , MW6 and MW7 were sampled after purging the wells of enough water that temperature, pH and conductivity stabilized. This data is presented in Appendix A. The purged water was contained in a labeled, secured 55 gallon drum on site. From the well information a ground water contour surface was plotted and a flow direction Inferred. This is presented in Figure 4C. The wells were allowed to recover after purging. A water sample was then collected with a fresh bailer. Each sample was divided among four 40-m1 VOA vials. The vials are supplied by the laboratory or a chemical supply company and are pre-cleaned to exact EPA protocols. The sample vials were labeled as to station, well, time, and sampler, and documented on the chain-of-custody sheet; they were then placed into an ice chest and cooled to 4°C with ice. The samples were delivered to a California State Certified Laboratory and signed over to the lab using standard chain-of-custody procedures. CHEMICAL ANALYSIS RESULTS The samples were analyzed at Matrix Environmental Laboratories (DHS#359 ) for Total Fuel Hydrocarbons (gasoline) with BTEX distinction, utilizing EPA Methods 5030 and 502, respectively. As noted under Purpose and Scope above, water samples were collected from MW1, MW2 , MW3 , MWS , MW6 and MW7 . Of these laboratory analyzed samples, all samples were Below Reportable Limits (BRL) . The analytical results and the pertinent gathering data are listed in Table 1, and the laboratory report is included in Appendix C. HYDROCARBON CONTAMINATION The wells sampled during this monitor round Indicate non detect for petroleum hydrocarbons. It is unclear, with the limited samples available, what effect the partial discharge of the ground water table in this area has had upon natural bio- degradation taking place at the site. While the overall ground water gradient remains low, with a slope of . 0025 , it has decreased slightly ( from . 003 in February, 1992 ) with a decrease of approximately 3 . 5 feet in ground water elevation. The aquifer test data along with the lithologic cross section and hydraulic gradient (Problem Assessment Report, December 5 , 1989 ) across the site infer that velocities of the ground water are such that natural bio-degradation is taking place. • 3