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WEST YOST ASSOCIATES Consuitmg tiginters October 27, 2017 Project No.: 213-17-17-42 SENT VIA: EMAIL San Joaquin County Environmental Health Department Central Valley Region 1868 East Hazelton Avenue Stockton CA 95205 SUBJECT: Work Plan for Exploratory Boring, Lodi Central Plume, Lodi, California Dear Sir or Madam: On behalf of the City of Lodi, Public Works Department (City), West Yost Associates prepared this work plan to perform exploratory drilling and sampling for the Lodi Central Plume (LCP) in Lodi, San Joaquin County, California (Site). Existing extraction well EW-7, which was installed in October 2016 along with the newly constructed groundwater treatment system at 531 Church Street, does not meet the required extraction rate to hydraulically contain and capture groundwater contamination in the LCP mid-plume area and will be destroyed. Destruction of EW- 7 is covered in a separate work plan. The City is planning to install a replacement extraction well EW-7R, the location of which was approved by the California Regional Water Quality Control Board, Central Valley Region (Water Board) in a letter dated April 20, 2017. The City plans to drill an exploratory boring to characterize subsurface conditions at the planned location of replacement extraction well EW-7R prior to constructing the well. Figure 1 shows the location of existing extraction well EW-7 and replacement extraction well EW-7R. DRILLING ACTIVITIES All drilling and sampling activities will be conducted by a California licensed (C-57) well drilling contractor in accordance with California Department of Water Resources Well Standards (Bulletins 74-81 and 74-90) and the San Joaquin County Environmental Health Department Well Permit. The exploratory drilling will be conducted using a sonic drill rig. 6800 Koll Center Parkway, Suite 150 Pleasanton, CA 94566 Phone 925 426-2580 westyost.com