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i <br /> en R <br /> April 15, 1997 <br /> Mr. Alex Perez <br /> Shell Oil Products Company <br /> P O Box 4023 <br /> Concord, California 94524 <br /> RE: Semi-Annual Monitoring Report - First Quarter 1997 <br /> Shell Service Station <br /> 7910 Lower Sacramento Road <br /> Stockton, California <br /> WIC #204-7524-0808 <br /> Dear Mr Perez <br /> This Semi-Annual Monitoring Report describes the recently completed activities associated <br /> with ground water monitoring and sampling at the referenced site (Plates 1 and 2) This <br /> report was prepared to meet reporting requirements issued by the Regional Water Quality <br /> Control Board, Central Valley Region and the San Joaquin County Environmental Health <br /> Division <br /> I <br /> Quarterly Monitoring & Sampling Summary <br /> Ground water monitoring and sampling for the first quarter of 1997 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-3 on February 6, <br /> 1997 Samples were transported to Sequoia Analytical (Sequoia) in Redwood City, <br /> California for chemical analysis <br /> • Enviros, Inc (Enviros) evaluated water-level measurement data and prepared a <br /> ground water contour/benzene concentration map (Plate 2) <br /> • Ground water samples collected from Well MW-I contained 2 0 ppb benzene <br /> Wells MW-2 and MW-3 were ND for TPPH and benzene MTBE concentrations <br /> ranged from 3 3 to 800 ppb <br /> Quarterly Sampling <br /> Monitoring Wells MW-I through MW-3 were sampled and analyzed for Total Purgeable <br /> Petroleum Hydrocarbons quantitated as gasoline (TPPH) according to EPA Method 8015 <br /> (Modified), and benzene, toluene, ethylbenzene, and xylenes (BTEX), and methyl-tertiary- <br /> butyl-ether (MTBE) according to EPA Method 8020 Additionally, a duplicate sample and <br /> an equipment blank were prepared and analyzed for quality control purposes <br /> Field monitoring data and chemical analytical data are summarized in Table I Blaine's <br /> quarterly ground water monitoring report is presented in Appendix A <br /> Enviros, Inc 270 Perkins Street Sonoma California Tel 707/935 4850 <br /> P O Box 259 95476 0259 Fax 707/935 6649 <br /> r <br />