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WARMLY GROUNDWATER MONRURING AND <br /> MOHITOFING WELL INSTALLATION FIFORT <br /> 1399 East Yosemde Avenue Manteca,CWffomla <br /> Aegis began a program of groundwater monitoring in February 1991 Monthly depth to <br /> ' groundwater measurements and quarterly sampling of groundwater was continued until <br /> May 1992. Quarterly monitoring and sampling has continued since On June 20, 1991, <br /> Aegis installed monitoring wells MW-1 B, MW-4, and MW-5 on the site Wells MW-4 and <br /> ' MW-5 were completed with 4-inch-diameter casing to a depth of 35 feet below grade <br /> Well MW-113 was completed with 6-inch-diameter casing by 'over-coring" the former <br /> MW-1A. <br /> 4.0 GROUNDWATER MONITORING <br /> ' 4.1 Groundwater Levels <br /> ' On April 30, 1993, Aegis personnel collected measurements of the depths to liquids in the <br /> six existing wells Since the last monitoring event on January 19, 1993, groundwater <br /> levels have risen in all wells (Figure 3) an average of approximately 164 feet (Table 1) <br /> On the bass of the April 30, 1993, measurements, groundwater is estimated to flow to the <br /> southwest (Figure 4) at an average gradient of approximately 0 003 ft/ft <br /> Previous groundwater levels are summarized in Table 1 All groundwater elevation <br /> measurements were conducted according to the Aegis standard operating procedures <br /> (SOP) included as Appendix A. <br /> 4.2 Groundwater Sampling and Anai sls <br /> On April 12, 1993, Aegis personnel collected groundwater samples from monitoring wells <br /> MW-1 B, MW-2, MW-3, MW-4 and MW-5 at the project site Well MW-6 was sampled on <br /> April 30, 1993. The samples were collected according to the Aegis SOP included in <br /> Appendix A, and submitted under chain-of-custody to Pace, Inc , of Novato, California, <br /> a state-certified analytical laboratory <br /> The samples were analyzed for concentrations of <br /> total petroleum hydrocarbons (I-PH), as gasoline, by modified EPA Method <br /> 8015, and, <br /> tbenzene, toluene, ethylbenzene, and total xylenes by modified EPA Method <br /> 8020. <br /> Groundwater analytical results obtained to date, including data reported by previous <br /> consultants, are summarized in Table 2 Concentrations of TPH, as gasoline, and <br /> benzene reported for samples collected on April 12 and 30, 1993, are also shown on <br /> M Figure 5. Copes of the laboratory analytical reports and chain-of-custody forms are <br /> included in Appendix B <br /> ' 9D4MF-0MR 2 <br /> ' i <br />