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313 <br /> April 15, 1997 <br /> Mr. Alex Perez <br /> Shell Oil Products Company <br /> P O Box 4023 <br /> Concord, California 94524 <br /> RE: Quarterly Monitoring Report - First Quarter 1997 <br /> Shell Service Station <br /> 4445 Pershing Avenue <br /> Stockton, California <br /> WIC #204-7524-2408 <br /> Dear Mr Perez <br /> This Quarterly Monitoring Report describes the recently completed activities <br /> associated with ground water monitoring and sampling at the referenced site (Plates <br /> 1 and 2) This report was prepared to meet quarterly reporting requirements issued <br /> by the Regional Water Quality Control Board, Central Valley Region and San <br /> Joaquin County Public Health Services <br /> Quarterly Monitoring & Sampling Summary <br /> iGround water monitoring and sampling for the first quarter of 1997 are summarized <br /> below <br /> • Blaine Tech Services, Inc (Blaine) of San Jose, California measured <br /> ground water levels and collected samples from Wells MW-I through <br /> MW-4 on February 25, 1997 Samples were transported to Sequoia <br /> Analytical (Sequoia) of Redwood City, California for chemical analysis <br /> • Environ, Inc (Enviros) evaluated water-level measurement data and <br /> prepared a ground water contour/benzene concentration map (Plate 2) <br /> Ground water flow direction is predominantly to the northeast at an <br /> approximate hydraulic gradient of 0 01 <br /> • Ground water samples collected from Wells MW-1 through MW-4 were <br /> ND for TPPH and BTEX compounds MTBE concentrations ranged from <br /> ND to 9 1 ppb A ground water contourlbenzene concentration map is <br /> presented on Plate 2 <br /> Quarterly Sampling <br /> Monitoring Wells MW-1 through MW-4 were sampled and analyzed for Total <br /> Purgeable Petroleum Hydrocarbons quantitated as gasoline (TPPH) according to <br /> EPA Method 8015 (Modified), benzene, toluene, ethylbenzene, and xylenes <br /> (BTEX), and methyl-tertiary-butyl-ether (MTBE) according to EPA Method 8020 <br /> Enviras, Inc 270 Perkins Street Sonoma California Tel 7071935 4850 <br /> P 0 Box 259 95476 0259 Fax 707/935 6549 <br />