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OLIA11TERLY GROUNDWATER IMONnURNG AND <br /> i WWATURINO WELL INSTALLATION REPORT <br /> 1399 East YOsemlte Avenue Manteca.CaliTemia <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-1 B 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 July 7, 1993, Aegis personnel collected measurements of the depths to liquids in the <br /> sax existing wells Since the last monitoring event on April 30, 1993, groundwater levels <br /> have risen in all wells (Figure 3) an average of approximately 1 49 feet (Table 1) On the <br /> basis of the July 7, 1993, measurements, groundwater is estimated to flow to the north <br /> to northwest (Figure 4) at an average gradient of approximately 0 02 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 Analysis. <br /> On July 7, 1993, Aegis personnel collected groundwater samples from all monitoring wells <br /> at the project site 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 (TPH), as gasoline, by modified EPA Method <br /> 8015, and, <br /> • benzene, 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 July 7, 1993, are also shown on Figure 5 <br /> Copies of the laboratory analytical reports and chain-of-custody forms are included in <br /> Appendix B. <br /> 90-OOF QMR 2 <br />