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CALIFORNIA GEOPHYSICAL GROUP, INC. IO Box 578341, Modesto, CA 95357 Tel (209) 527-1247 February 25, 1996 Fox (209) 527-4810 Public Health Services San Joaquin County P.O. Box 2009 Stockton, Ca 95307 RE: Quarterly Report January, 1996 Darpetro Service Station 749 E. Charter Way Stockton, Ca. Site # 1060 IThe site was sampled on January 24, 1996 and the water samples were sent to Sherwood Labs of Hilmar, California, who forwarded them to Associated Laboratories. The water table measurements, sampling parameters and chain of custody are attached. Table I lists the history of the water analyses taken at the site I since January 26, 1990. Table II is the history of the water table measurements, and Table III list the history of hydraulic gradients. Attached is one water table elevation plot showing the approximate groundwater gradient. Also attached are four plots one for each of the BTEX chemicals showing the isoconcentrations on January 24 , 1996. The water samples were obtained by using a pre-cleaned bailer. This was performed after the measured field parameters had stabilized during the purging with a pump. See protocols. Water samples were placed in appropriate glass containers with teflon- lined lids. Wells MW-1 , 2 and 3 were measured for depth of water only. Mr. Steve Sasson, the county regulator, authorized us to not sample these wells, since they are located near other wells and no additional information would be obtained. FINDINGS The groundwater flow is to the Northeast at a gradient of 0. 0019 Ft/Ft. The groundwater level has risen about 1. 1 feet, since the last quarterly reading. Figure 1 shows the water table elevations. Gasoline contamination is present in all of the wells above the California Action Levels. We have prepared isoconcentration Plots of Benzene, Toluene, Ethylbenzene and Xylenes. They are 61 shown on Figures 2 , 3 , 4 and 5. Page 1