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August 3, 1999 <br /> Mr Harlin Knoll <br /> San Joaquin County Environmental Health Division <br /> 304 East Weber Avenue <br /> Stockton, California 95201 <br /> Re Quarterly Monitoring Report - Second Quarter 1999 <br /> Shell-branded Service Station <br /> 4445 Pershing Avenue <br /> Stockton, California <br /> Incident #98996182 <br /> SAP 4136142 <br /> Dear Mr Knoll <br /> This Quarterly Monitoring Report describes the recently completed activities associated with <br /> groundwater monitoring and sampling at the referenced site (Plates 1 and 2) This report was <br /> prepared to meet quarterly reporting requirements issued by the Regional Water Quality <br /> Control Board, Central Valley Region and San Joaquin County Public Health Services <br /> • Quarterly Monitoring & Sampling Summary <br /> Groundwater monitoring and sampling for this quarter is summarized below <br /> • Blaine Tech Services, Inc (Blaine) of San Jose, California measured groundwater <br /> levels in Wells MW-1 through MW-4, and collected samples from Wells MW-1 <br /> through MW-4, VEW-1, and VEW-2 on May 28, 1999 Samples were transported to <br /> Sequoia Analytical (Sequoia) of San Carlos, California for chemical analysis <br /> • Cambria Environmental Technology, Inc (Cambria) evaluated water-level <br /> measurement data and prepared a groundwater contour/chemical concentration map <br /> (Plate 2) Groundwater flow direction varies beneath the site, flowing north, <br /> northeast, and south from a hydraulic ridge located around Wells MW-2 and MW-4 <br /> Oakland CA The hydraulic gradient ranges from 0 004 to 0 01 <br /> Sonoma CA <br /> Portland OR <br /> S e a t t I e WA • TPPH was not detected in any of the wells sampled Benzene was detected in Wells <br /> (VEW-1 and MW-1 at concentrations of 0 736 and 0 688 ppb, respectively MTBE <br /> Cambria was detected in MW-2 at a concentration of 17 5 ppb, MTBE was not detected in <br /> Environmental <br /> Technology,Inc Wells MW-2 through MW-4, VEW-1 or VEW-2 <br /> oeykins Street <br /> P 0 Box 259 <br /> Sonoma CA 95476 <br /> Tel(707)935-6850 <br /> Fax(707)935-6649 <br />