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j aj <br /> July 15, 1998 <br /> Mr. Alex Perez <br /> Equilon Enterprises, LLC <br /> P.O. Box 8080 <br /> Martinez, California 94553 <br /> Re: Quarterly Monitoring Report - Second Quarter 1998 <br /> Shell-branded Service Station <br /> 4445 Pershing Avenue <br /> Stockton, California <br /> WIC #204-7524-2408 <br /> Dear Mr. Perez: <br /> I <br /> This Quarterly Monitoring Report describes the recently completed activities associated with <br /> ground water monitoring and sampling at the referenced site (Plates t and 2). This report <br /> was 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 8r Sampling Summary <br /> Ground water monitoring and sampling for this quarter are summarized below: <br /> • Blaine Tech Services, Inc. (Blaine) of San Jose, California measured ground water <br /> levels and collected samples from Wells MW-1 through MW-4, VEW-1, and VEW-2 <br /> on May 20, 1998. Samples were transported to Sequoia Analytical (Sequoia) of <br /> Redwood City, California for chemical analysis. <br /> • Cambria Environmental Technology, Inc. (Cambria) evaluated water-level <br /> measurement data and prepared a ground water contour/chemical concentration map <br /> (Plate 2). Ground water flow direction appears to vary at the site flowing <br /> Oakland„ CA predominately north and south of Well MW-4 at an approximate hydraulic gradient <br /> Sonoma, CA <br /> Portland, OR of 0.004. <br /> Seattle, WA <br /> • TP�PH and benzene were not detected in Wells MW-1 through MW-4 and VEW-2. <br /> Cambria Well VEW-1 contained TPPH and benzene at concentrations of 58 ppb and 0.69 <br /> Environmental <br /> Technology, Inc. ppb, respectively. Wells MW-3, MW-4, VEW-1, and VEW-2 contained MTBE at <br /> concentrations ranging from 3.5 ppb to 21 ppb. MTBE was not detected in Wells <br /> 270 Perkins Street <br /> P.O. Box 259 MW-I and MW-2. <br /> Sonoma,CA 95476 <br /> Tel(707)935-4850 <br /> Fax(7a7)935-6649 <br />