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k <br /> C A M B R I A <br /> January-16'2000 <br /> Ms Lori Duncan <br /> San Joaquin County Public Health Services <br /> 304 E Weber Street <br /> Stockton, California 95202 <br /> Re Quarterly Monitoring Report - Third Quarter 1999 <br /> Shell-branded Service Station <br /> 6131 Pacific Avenue <br /> Stockton, California <br /> SAP Code 136149 <br /> Incident No 98996189 <br /> Dear Ms Duncan <br /> This report describes the recently completed activities associated with groundwater <br /> monitoring and sampling at the referenced site (Figures 1 and 2) This report was prepared to <br /> meet quarterly reporting requirements issued by the Regional Water Quality Control Board, <br /> Central Valley Region and San Joaquin County Public Health Services (SJCPHS) <br /> . Quarterly Monitoring & Sampling Summary <br /> Groundwater monitoring and sampling for the third quarter of 1999 are summarized below <br /> • Blaine Tech Services, Inc (Blaine), of San Jose, California measured groundwater <br /> levels and collected groundwater samples from wells MW-1 through MW-7 and <br /> VEW-2 on August 20, 1999 Samples were transported to Sequoia Analytical located <br /> in San Carlos and Morgan Hill, 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 /> (Figure 2) Groundwater flow direction ranges from southwesterly to northeasterly at <br /> approximate hydraulic gradients ranging from of 0 001 to 0 004 <br /> Oakland CA <br /> Sonoma CA . TPHg was detected in groundwater samples collected from the site at concentrations <br /> Portland OR <br /> S e a t t l e WA ranging from <50 0 to 110,000 ppb, and benzene concentrations ranging from <br /> <0 500 to 3,240 ppb MTBE (by EPA Method 8020) was not detected in any of the <br /> Cambria wells MTBE (by EPA Method 8260) was detected in wells MW-1, MW-4 and <br /> Environmental VEW-2 at concentrations ranging from 3 53 to 67 2 ppb Monitoring well MW-4 <br /> Technology,Inc <br /> contained DIPE and TAME concentrations of 45 2 ppb and 89 1 ppb, respectively <br /> 'Serkms Street Methanol concentrations were less than 1,000 ppb in all groundwater samples <br /> P O Box 259 <br /> Sonoma CA 95476 <br /> Tel(707)935-4850 <br /> Fax(707)935-6649 <br /> I <br />