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Memorandum LAIVEAN <br />555 Montgomery Street, Suite 1300 San Francisco, CA 94111 T: 415.955.5200 F: 415.955.5201 <br />To: Mr. Nathan Casebeer <br />Regional Water Quality Control Board Central Valley Region <br />From: Varinder Oberoi, PE — Langan Engineering and Environmental <br />Noel Liner, Project Geologist — Langan Engineering and Environmental <br />Date: 26 January 2017 <br />Project: Lodi Central Plume — Mid-Plume Area Remediation <br />Subject: Workplan: <br />Subsurface Exploration for Evaluation <br />of Mid-Plume Replacement Extraction Well <br />This memorandum has been prepared on behalf of the City of Lodi (City) to act as a workplan <br />for siting of a new extraction well to contain and treat TCE and PCE impacted groundwater that <br />has moved downgradient and beyond the Lodi Central Plume (LCP). This memorandum is being <br />issued to request regulatory concurrence for proposed exploratory drilling activities in siting a <br />replacement extraction well for the recently installed groundwater treatment system at 531 <br />Church Street. A description of the current status of the project and proposed activities are <br />presented below. <br />Current Status <br />In June 2016, the City completed construction of a granular activated carbon groundwater <br />treatment system at 531 Church Street, in the central mid-plume portion of the groundwater <br />plume. The final plans for the extraction system were transmitted to you by email on Thursday <br />December 03, 2015 from Lyman Chang of the City. Extraction well EW-7 was installed to a <br />depth of 135 feet by sonic rotary drilling adjacent to the treatment system in order to capture <br />and supply groundwater to the treatment system. The groundwater well has since been <br />discovered to be in poor hydraulic communication with the surrounding formation, and is unable <br />to function as intended. Attempts to revitalize the well by additional well development have <br />failed to produce satisfactory results. Therefore, a second phase of work is being undertaken to <br />evaluate and identify the optimum replacement location of the proposed LCP mid-plume <br />extraction well EW-7. <br />Exploratory Borings <br />Langan proposes to advance cone penetration test (CPT) borings at the following two locations: <br />Tokay Street (between Church and School Streets), and <br />The intersection of Spruce and School Streets. <br />LANGAN