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Work Plan for Refined Plume Definition and Management of Floating Product-7500 W!1 th St., Tracy, CA, Page 77 .,, 10.0 WELL CLOSURES When any well installed at the 7500 West Eleventh Street site has served its designed ,^ purpose, it will be closed in compliance with the following procedures. ' 10.1 Well Closure Procedure Each well to be closed, whether it served as a groundwater-quality monitoring well, a floating product monitoring well or a floating product extraction well, including the extraction well located in the proposed backfilled floating product cut-off trench will be closed under the permit and oversight of the SJCEHD. The work will be performed by a drilling contractor holding the required C57 license issued by the California State Contractors aA Licensing Board. To initiate a well closure, it will be grouted with Type II Portland Cement, which will be conducted through the bottom of the well in a tremie pipe that will be slowly raised to the surface as the well and the annular space between the well casing and the boring •• wall are filled. Any displaced groundwater that would otherwise flow from the well will be intercepted by a w submersible or suction pump and discharged into a 55-gallon drum so that it can be retained on the site for later disposal at a permitted facility. ;- When the grout placed in the well has set, the well head cover box will be removed by excavation, as will the well casing down to a minimum depth of two feet. The resulting pit will be restored using backfilled clean soil with a covering of 6 inches of concrete or, in the case of wells not on the 7500 West Eleventh Street property itself, such other material as may be specified by the concerned property owner or the SJCPWD. 10.2 Proposed Closure of Existing Wells SJC has previously expressed concern that existing groundwater-quality monitoring wells *� MW-3A, 3B and 12A, which penetrate through the aquitards present at the bottom of the first near-surface aquifer at the Navarra Property, pose a significant and unwarranted risk to the quality of the groundwater in the deeper aquifers into which they penetrate (The San Joaquin Company 2003b, 2003c, 2002a, 2002b, 2002c). In the case of Monitoring Well MW-3B, that well penetrates through two protective aquitards and exposes two uncontaminated aquifers to the risk that their water quality may be compromised by an accidental spill of fuel hydrocarbons or other material from the tractor-trailer rigs and other heavy transport equipment that frequently pass over and park on the property. " SJC recognized the presence of a wide-spread silty clay aquitard beneath the shallow aquifer at 7500 West Eleventh Street at the time the initial small-diameter borings were drilled and soil and groundwater samples recovered during the first phase of site characterization that Iwo was conducted in April 2000. At that time, recognizing that the aquitard would protect the quality of water in the deeper aquifers, SJC's California-licensed professional engineer in responsible charge of the work, who has more than 40 years of experience in contaminant hydrogeology, directed that all small-diameter borings that had penetrated through that sic