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QUARTERLY REPORT <br /> for <br /> Former Mobil Station 04-NP4 <br /> 2375 Tracy Boulevard <br /> Tracy, California <br /> August 5, 1992 <br /> INTRODUCTION <br /> This report presents results of June 1992 quarterly ground water monitoring and sampling <br /> performed by Alton Geoscience and remediation status at former Mobil Station 04-NP4, <br /> 2375 Tracy Boulevard,Tracy, California. The site is currently an operating BP Oil Company <br /> station A site vicinity map is shown in Figure 1. <br /> In 1986, four underground storage tanks (USTs) were removed from the site <br /> Concentrations of petroleum hydrocarbons were detected in the subsurface Kaprealian <br /> Engineering, Inc. (KEI) subsequently installed Monitoring Wells MW-1 through MW-4 In <br /> 1987, COY installed an additional four wells; MW-5 through MW-8. Alton Geoscience was <br /> retained by Mobil Oil Corporation in 1990 to perform a supplemental site investigation As <br /> part of the continuing site characterization, another four monitoring wells, AMW-1 through <br /> AMW-4, were installed During October 1991, Alton Geoscience installed Wells AMW-5 <br /> and AMW-6. <br /> SUMMARY OF REMEDIATION ACTIVITIES <br /> Installation of the ground water automatic recovery system (ARS) was completed in <br /> May 1992. A site plan with ARS layout is shown in Figure 2. Sampling and monitoring of <br /> ARS performance are conducted and reported in accordance with National Pollutant <br /> Discharge Elimination System (NPDES) permit compliance requirements. As of June 17, <br /> 1992, 6,900 gallons of ground water was removed and treated, at an average pumping rate <br /> of 0 052 gallons per minute, from MW-5. <br /> FIELD PROCEDURES <br /> On June 24 and 25, 1992, Alton Geoscience monitored and sampled ground water <br /> Monitoring Wells AMW-1 through AMW-6, MW-1 through MW-4, and MW-6 through <br /> MW-8. Ground water samples were collected from all wells not containing downhole <br /> pumping equipment or free product. Alton Geoscience ground water monitoring and <br /> sampling protocol is presented in Appendix A. Ground water field survey forms presenting <br /> field measurements and observations are presented in Appendix B. <br /> 1 ' <br />