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CALIFORNIA GEOPHYSICAL GROUP, INC. O Box 578341, Modesto, CA 95357 Tel (209) 527-1247 Fax (209) 527-4810 February 14 , 1997 ' Public Health Services San Joaquin County P.O. Box 388 Stockton, Ca 95201 ' RE: Quarterly Report January, 1997 Darpetro Service Station 749 E. Charter Way Stockton, Ca. Site # 1060 I The site was sampled on January 28, 1997 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 custodies are attached. Table 1 lists the water levels and depths to water, since January 26, 1990. Table 2 lists the hydraulic gradients and bearings and ' Table 3 list the chemical analyses taken each quarter. Also attached is a plot of the water table contours on October 28, 1996 . The water purging was performed with a decontaminated pump. This was performed and the measured field parameters stabilized during the purging. Water samples were taken with a decontaminated ' bailer. See protocols. Water samples were placed in appropriate glass containers with teflon-lined lids. Wells MW-1, 2 and 3 were not measured or sampled, authorized by Mr. Steve Sasson, the county regulator. ' FINDINGS The groundwater flow is to the Northeast at a gradient of 0.0014 Ft/Ft, The groundwater level has risen about 2 .7 feet, since the ' last quarterly reading. The water this quarter is the highest it has been at this site since January, 1990. Figure 1 shows the water table elevations. ' Benzene contamination is present in all of the wells above the California Action Levels. Also the oxygen levels were measured ' using a YSI Model 51B oxygen level meter. The meter was calibrated the day before performing the testing. The oxygen level was measured 5 feet below the surface of the water table. The chemical MTBE was not tested for this quarter. It was tested for three times this year and no MTBE was found. Page 1