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Ochil . 2001 10 : 26AM CONERRTH TECHNOLOGIES No - 6747 P . 2 / 14 <br /> CONDOR EARTH TECHNOLOGIES INC. <br /> 188 Frank West Circle <br /> October 10, 2001 Suite <br /> Stockton , CA 95206 <br /> (209) 234-0518 <br /> FAX (209) 234-0538 <br /> Jeffrey C. F. Wong <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> 304 E. Weber Avenue, Third Floor <br /> Stockton, California 95202 <br /> Re: Deep Well Screen Interval <br /> Canepa's Car Wash, 6230 Pacific Avenue, Stockton, CA <br /> Site Code: 1229 ; Condor Project No. 1707 <br /> ]Dear Mr. Wong: <br /> Condor Earth Technologies, Inc. (Condor) completed the cone penetrometer testing (CPT) investigation <br /> at Canepa' s Car Wash on Pacific Avenue in Stockton on September 28 . One of the primary reasons for <br /> this investigation was to determine the screen interval for deep wells to be installed at the site [between 70 <br /> and 120 feet below ground surface (bgs)] . The deep wells were intended to monitor the vertical extent of <br /> petroleum contamination at the site. As a result of the CPT investigation, Condor is proposing a change <br /> in the previously-submitted work plan. Based on the CPT results, Condor is now proposing to construct <br /> one deep monitor well in only one of the three areas investigated with CPT (within the center of the <br /> shallow groundwater plume near the facility fuel pumps). <br /> The CPT investigation involved four borings in each of three locations. The first boring at each of the <br /> three locations used CPT logging equipment to log the borehole. No groundwater samples were collected <br /> from these borings used to log the subsurface. The subsequent three borings at each of the three locations <br /> were used to collect discrete water samples at three depths below 70 feet based on subsurface lithology <br /> investigated by the initial logged boring. The approximate locations of the borings are shown in an <br /> attached figure. These borings were designated HP 1 , HP2 and HP3 (from deepest to most shallow) for <br /> those installed near the fuel pumps, HP4, HP5 and HP6 for those installed in the northeast portion of the <br /> site, and HP7, 1IP8, and HP9 for those installed in the northwest portion of the site. The depth of the <br /> water samples was based on apparent lenses of permeable material between 70 and 120 feet bgs. The <br /> water samples were analyzed for TPH-G, 13TEX, and the six gasoline oxygenates including MTBE. No <br /> analytes were detected at or above the laboratory reported detection limits in any of the groundwater <br /> samples collected from the northeast and northwest boring clusters (HP4 through HP9). In the borings <br /> near the fuel pump island (HPI through HP3 ), BTEX and TPH-G were detected at low concentrations in <br /> the middle groundwater sample collected from between 101 and 110 feet bgs (HP2). No analytes were <br /> detected at or above the laboratory reported detection limits in the shallower sample collected between 91 <br /> and 95 feet bgs (HP3 ) and the deeper sample collected between 120 and 125 feet bgs (HPI ). <br /> The detection of TPH-G and BTEX in the middle horizon (HP2) and the absence of contamination in the <br /> shallower and deeper horizons (HP3 and HP 1 , respectively) indicate that the results for the middle <br /> ENVIRONMENTAL E GEOLOGICAL ENGINEERING V GEOTECHNICAL <br />