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I <br /> Wesitem F9e9itrrtal pperalions <br /> . EA ENGINEERING. Sr 41 ut.yene aIijorn <br /> in SCIENCE, AND �!. ) uta~ tte,Califarnis 545,9 <br /> (415)283-7077 <br /> TECHNOLOGY. INC. <br /> 31 March 1989 <br /> Yi, 1 r <br /> l <br /> 1990 J <br /> Kay Huffman <br /> Engineer, <br /> WeI <br /> st West Central DivisionChevron <br /> P.O. Box 5004 <br /> San Ramon, California 94583-0804 <br /> RE: Quarterly Sampling and Analysis of Groundwater <br /> Former Chevron SS 9-7780 <br /> 3246 E. Fremont Street <br /> Stockton, California <br /> Dear Kay: <br /> As requested by Chevron U.S.A. Inc. , EA sampled the groundwater <br /> at former Chevron Service Station (SS) 9--7780 in Stockton, <br /> California. The groundwater from three monitoring wells was <br /> sampled according to standard protocols on 22 March 1989. No <br /> water was found in four of the seven monitoring wells on-site. <br /> . The. samples were submitted under chain of custody to Pace <br /> Laboratories where the samples were analyzed for total petroleum <br /> hydrocarbons by DHS-modified EPA Method 8015 and for benzene, <br /> toluene, ethylbenzene, and xylenes by EFA Method 8020. The <br /> analytical results from this recent sampling are tabulated in <br /> Table 1 and are compared with previous analyses in Table 2. <br /> The depths to groundwater at this site have been variable. As <br /> indicted on Table 3, the depths to groundwater in early 1988 were <br /> 44 . 53 to 48.00 feet below the top of casing; between February <br /> 1988 and April 1988, the indicated direction of groundwater flow <br /> had shifted from northwest to south-southwest. The flow direc- <br /> tion determined from elevations of the top of the groundwater in <br /> three wells on 22 March 1988 appears to be to the east, although <br /> the gradient is nearly flat (0.0006) . <br /> Concentrations of benzene greater than 0.0007 mg/L have EA3not yet <br /> been detected at the property fr�e�lsatntheeither <br /> Broadway Hatchery, <br /> The proximity of a water supply <br /> 3206 E. Freemont Street is still a concern. Concentrations of <br /> petroleum hydrocarbons in the groundwater closer to the original <br /> location of the underground storage tanks could not be determined <br /> because of the lack of water in those wells; the depths to <br /> groundwater have apparently increased during the recent drought, <br /> dropping the top of groundwater below the bottom of four moni- <br /> toring wells. <br /> BALTIMORE 0 CHICAGO 0 CINCINNATI 0 LINCOLN 0 NEW YORK 0 SAN FRANCISCO <br />