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In December 1989, Applied GeoSystems began qt arterly monitoring of the ground-water <br /> quality at the site. The direction of ground-water now across the site was evaluated to be <br /> to the northwest, and the average gradient was evaluated to be 0.0012. Laboratory analyses <br /> of ground-water samples collected during the subsequent year of monitoring (1990)indicated <br /> concentrations of dissolved hydrocarbons had dec eased to below Maximum Contaminant <br /> Levels (MCL's) established by the California Dep rtment of Health Services for drinking <br /> water_ In addition, the ground-water flow direction and gradient had remained fairly <br /> consistent. Therefore, Applied GeoSystems recommended the wells be sampled semi- <br /> annually during 1991 to verify hydrocarbon concen rations remained below MCL's for over <br /> a period of 1 year. Data collected during the June 1991 monitoring event indicated <br /> hydrocarbons were not detected in ground-water samples and the ground-water flow <br /> direction remained constant. Data collected during the December 1991 monitoring event <br /> indicated concentrations of TPHg, TPHd, benzen ethylbenzene, and total xylene isomers <br /> were not detected, with the exception of one sampl with a TPHg concentration of 200 parts <br /> per billion (ppb). Toluene was detected in the samples from. the three wells at <br /> concentrations ranging from 0.8 ppb to 5.7 ppb. herefore, dissolved hydrocarbons have <br /> been either not detectable or below their respecti a MCL's for nearly two years. <br /> On the basis of information accumulated to date, i is my opinion and that of my consultant, <br /> RESNA, that no further environmental work is necessary at this site. Based on the results <br /> of the ongoing investigation, we formally petition the California Regional Water Quality <br /> Control Board, Central Valley Region, to close the site to further environmental work. No <br /> environmental work is currently being performed at the site. We look forward to your <br /> response. Please call if you require any further iriformation. <br /> Sincerely, <br /> Gary Bb <br /> oy <br /> cc: Mr. Keith Romstad, RESNA Industries, Sacramento <br /> Ms. Linda Turkatte, San Joaquin County <br />