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1 <br /> NSA- <br /> Working To Restore Nature <br />' FOURTH QUARTER MONITORING AND SAMPLING <br />' On October 1, 1993, groundwater monitoring was conducted at the above referenced site on <br /> wells MW2, MW3, MW4 and MW5 (Plate 1). During monitoring, the depths to water were <br /> measured, the wells were purged and samples were collected pursuant to RESNA's Quality <br /> Assurance/Quality Control Plan. Well purge logs and monitoring data are included in Appendix <br /> I <br /> Groundwater elevations have dropped an average of 1 63 feet in the wells since the July 1993 <br /> monitoring Groundwater monitoring data is summarized in Table 3 The gradient was <br />' calculated to be in a north-northeast direction at 0 004 ft/ft, which is consistent with previous <br /> gradients (Plate 3, Groundwater Gradient Map) <br /> Collected samples were analyzed for benzene, toluene, ethylbenzene, and xylenes (BTEX), and <br /> total petroleum hydrocarbons as gasoline (TPHg) utilizing EPA method 5030/8020/8015 No <br /> petroleum hydrocarbon constituents were present above method detection limits in monitoring <br />' wells MW2, MW3, MW4 or MW5 Analytical data is presented in Table 2 The laboratory <br /> data sheets and chain-of-custody documentation are included in Appendix II. Laboratory <br /> analyses were conducted by Sequoia Analytical Laboratories, Cal EPA, ELAP Certification No <br /> 1210. <br /> Additional characterization of soil pile SP2 was conducted on October 1, 1993 One four sleeve <br /> 1 composite sample was collected from soil pile SP2 (Plate 2) Petroleum hydrocarbon analytes <br /> were not present in the soils samples Chain-of-custody documentation and analytical data sheets <br /> are presented in Appendix II. <br /> RECOMMENDATIONS/CONCLUSIONS <br /> The threat of groundwater degredation formerly posed by residual soil contamination has been <br /> eliminated by the removal of impacted soil <br />' A total of 13 rounds of groundwater monitoring have been conducted at the site over a period <br /> of three years During this period groundwater impact was found to be confined to the tank pit <br /> (MW1) and was observed in downgradient wells MW2 and MW4 on only one occasion each <br /> Subsequent to excavation of the residual contaminated soil, the source of groundwater <br />' degradation, three confirmation rounds of groundwater monitoring have been conducted <br /> Petroleum hydrocarbon analytes were not present at or above method detection limits during any <br /> monitoring episode since excavation occurred <br /> RESNA requests formal closure review of the soil and groundwater investigation at JB Terminal <br />' 6700 Grantline Road, Tracy, California <br /> REPORTS\CiAsuRE FNL 3 <br />