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�+ CALIFORNIA GEOPHYSICAL GROUP, INC, <br /> P O Box 691 , Poway, CA 92074 Tel (619) 486-1323 <br /> FAX (619) 486-4936 <br /> May 12 , 1994 <br /> 1 � <br /> Public Health Services <br /> San Joaquin County <br /> P.O. Box 20091 <br /> Stockton, Ca 94-347 -?6-2.-o <br /> 1 <br /> RE: Quarterly Report May 1994 <br /> Darpetro Service Station _NVIRONMENIH <br /> 749 E. Charter Way PFRMI1 'SERVICES <br /> Stockton, Ca. <br /> Site # 1060 <br /> The site was sampled on April 27, 1994 and the laboratory <br /> analyses of the water samples were done by Sherwood Labs of <br /> Hilmar, California. The water table measurements, sampling <br /> parameters and chain of custody are attached. <br /> 1 <br /> Table I lists the history of the water analyses taken at the site <br /> since Jan. 26, 1990 . Table II is the history of the water table <br /> measurements, and Table III list the history of hydraulic <br /> gradients. Attached is one water table elevation plot showing <br /> the approximate groundwater gradient. <br /> The water samples were obtained by using a pre--cleaned steel <br /> bailer and new section of rope. This was performed after the <br /> measured field parameters had stabilized during the purging <br /> operation. See protocols. Water samples were placed in <br />` appropriate glass containers with teflon-lined lids. <br /> FINDINGS <br /> The groundwater flow has shifted slightly to the East at a <br /> gradient of 0. 0069 Ft/Ft. The groundwater level has risen about <br /> 1.00 feet since the last reading. The groundwater contamination <br /> level is less in well MW-7 than the last quarter. California <br /> Geophysical Group believes that the contamination at well MW-7, <br /> may have a source other than the Exxon service station site. <br /> In addition, well MW-4 has less contamination than from the past <br /> quarter. However, MW-5 and MW-8 both have higher levels of <br /> contamination. This increase in contamination could be due to <br /> I the shift of the gradient to the East. <br /> On February 10 , 1994 , we performed an air permeability test on <br /> the unsaturated zone at this site. We connected a Rotron vacuum <br /> blower to wells MW-6 and MW-5 and measured the vacuum in wells <br /> MW-3 , MW-2 and MW--1 . From the readings obtained during the <br /> 46 survey we have plotted the vacuum versus the distance from the <br /> extraction well . This is Figure 2 . The original vacuum in the <br /> extraction well was 81 inches of water. The effective radius of <br /> I <br />