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9 <br /> I <br /> reported within the survey area. Details of this investigation can be found in SECOR's <br /> October 10, 2001 , Well Search Report. <br /> 2002 Monitoring Well Installation: In February 2002, SECOR installed groundwater <br /> monitoring wells MW-5 and MW-6B to approximately 50 fbg, and wells MW-6A and MW-7 to <br /> 20 fbg. TPHd was detected in two soil samples at concentrations of 22 mg/ kg in MW-5 and <br /> 46 mg/ kg in MW-7, both collected at 10 fbg. TPHg in soil was detected at a maximum <br /> concentration of 620 mg/ kg in MW-5 at 5 fbg. Benzene was detected at a maximum <br /> concentration of 0.34 mg/kg in MW-7 at 10 fbg. MTBE was detected only in the soil sample <br /> from MW-5 at 35 fbg, at a concentration of 0.0014 mg/ kg. Details are included in SECOR's <br /> July 26, 2002, Site Assessment Report. <br /> 2003 Transducer Study: In January 2003, SECOR installed pressure transducers with built-in <br /> data loggers in site monitoring wells MW-5, MW-6A, and MW-613 to assess hydrogeologic <br /> communication between the shallow aquifer, through which all site wells are screened, and the <br /> deeper aquifer beneath the Corcoran clay located between approximately 400 and 500 fbg, in <br /> which the City of Tracy's Ball Park Well is screened (570 to 732 fbg) . Displacement versus time <br /> plots indicated that water levels increased in deeper-screened site wells MW-5 and MW-613 <br /> when the Ball Park Well pump was operational, and decreased when the pump was turned off. <br /> SECOR attributed this relationship to mechanical, rather than hydrogeological processes. No <br /> significant influence was noted in shallow well MW-6A. Activities are detailed in SECOR's <br /> July 3, 2003, Transducer Stud. <br /> 2007 Case Closure Request and Sensitive Receptor Survey: In August 2007, CRA submitted a <br /> case closure request and conducted a sensitive receptor survey for wells within a 1/2-mile radius <br /> of the site. According to DWR records, no domestic or municipal supply wells were located <br /> within the search radius; though one irrigation well was identified approximately 0.23 miles <br /> east-northeast (crossgradient) of the site. The closure request and well survey are included in <br /> CRA's August 27, 2007, Case Closure Request. <br /> 632271 (4) 2 CONESTOGA-ROVERS & ASSOCIATES <br />