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CALIFORNIA GEOPHYSICAL GROUP, INC, <br /> O Box 578341, Modesto, CA 95357 Tel (209) 527-1247 <br /> August 13, 2004 Fax. (209) 527-4810 <br /> FE 2 <br /> Public Health Services R EC E N!F3 r <br />' San Joaquin County <br /> 304 East Weber Ave 3rd Floor AUG 2 4 2004 <br />' 'Stockton, CA 95202 ENVIRONMENT I-iEALTH <br /> RE Quarterly Report July 2004 <br /> PERMIT/SERVICES <br /> Darpetro, Inc USA Service Station <br /> 749 E Charter Way <br />' Stockton, CA <br /> Site No 1060 <br /> This site was sampled on July 19, 2004 Sherwood Labs of Hilmar, California analyzed <br />' the samples, their reports are attached <br /> Table 1 lists the history of the water table depths, elevations, water analyses and oxygen <br />' levels at this site since January 26, 1990 Table 2 lists the hydraulic gradients and <br /> bearings Sampling protocols are included <br /> FINDINGS <br /> The groundwater gradient bearing is N 75 E and the gradient is 0 0032 Ft/ft See Table 2 <br />' and Figure 1 <br /> Each well was measured for depth of water prior to any wells being purged The depth to <br /> water in the first measurement is written and noted on the sample sheets <br /> The groundwater in wells MW-1, MW-5, MW-6, MW-7, MW-8, MW-9, MW-10 and MW-11 <br /> were above California Drinking Water Standards for benzene The benzene plume <br /> appears to be flowing north around well MW-1 Wells MW-7 and MW-9 are contaminated <br /> from sites, west of this site See Figure 2 <br /> The wells which had TPH are MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, MW-7, MW-8, <br /> MW-9 MW-10 and MW 13 Wells MW-4, MW-7 and MW-9 are contaminated from sites <br /> entering this site from a source to the west of this site See Figure 3 <br />' MtBE was recorded in wells MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, MW-7, MW-8, <br /> MW-9, MW-11 and MWA 3 Perhaps the MtBE in well MWA 1 is coming from the site on <br /> the southeast corner of Charter Way and Grant Street <br /> I Dissolved oxygen levels were recorded this quarter The measured levels are shown on <br /> Table 1 and Figure 5 <br /> We have received the letter dated July 6, 2004 from the Environmental Health Department <br /> San Joaquin County granting approval of our work plans dated 07 May 2004 and 19 May <br /> 2004 to drill soil gas samples around the tanks and pumps and boring B-4 and monitoring <br /> well MW-14 to further define the horizontal and vertical extent of the contamination at this <br />