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<br /> <br />Central Valley Regional Water Quality Control Board <br />10 March 2021 <br /> <br /> <br />Andrew Richle <br />Water Plant Superintendent <br />City of Lodi <br />2001 W. Turner Road <br />Lodi, CA 95242 <br /> <br />CONCURRENCE WITH CPSA GWET AND SVE SYSTEMS DECOMMISSIONING <br />ACTIVITIES WORK PLAN, CITY OF LODI CENTRAL PLUME SOURCE AREA, LODI, <br />SAN JOAQUIN COUNTY <br /> <br />Central Valley Water Board staff has reviewed the 4 March 2021 CSPA GWET and <br />SVE Systems Decommissioning Activities Work Plan (work plan) prepared by Civil <br />Hydro Tech (CHT) on behalf of the City of Lodi (City) for the Lodi Central Plume Source <br />Area (CSPA) in Lodi. The work plan provides a plan for performing the closure activities <br />associated with the decommissioning of the CPSA Groundwater Extraction and <br />Treatment (GWET) and Soil Vapor Extraction (SVE) systems. The work plan was <br />submitted in accordance with the 18 May 2020 letter from Central Valley Water Board <br />staff that generally concurred with the recommendations in the 12 May 2020 Central <br />Plume Source Area Groundwater Extraction and Soil Vapor Extraction Systems Closure <br />Report. That letter also summarized the rationale for the decommissioning of the <br />remediation system that operated from 2011 to 2019. <br /> <br />In the work plan, CHT proposes to remove all remediation equipment and to abandon <br />all GWET and SVE wells in accordance with the methods provided in the work plan. A <br />limited soil excavation will also be conducted to remove residual tetrachloroethene <br />(PCE) soil contamination along the sewer line in an alleyway where the PCE leakage <br />occurred. The residual PCE in this area has been delineated by several soil vapor <br />samples that show PCE in soil vapor up to 153,000 micrograms per cubic meter. The <br />locations of the GWET wells, SVE wells, equipment (TS-1), piping, and the proposed <br />soil excavation are shown on Figures 2 and 3 of the work plan. <br /> <br />The soil excavation will be approximately 100 feet by 6 feet to a depth of 5 feet with a <br />volume of approximately 115 cubic yards. Following excavation, sidewall samples will <br />be collected from the perimeter of the excavation at lineal intervals of approximately <br />20 feet and bottom samples every 500 square feet of excavation bottom. Excavated <br />soil will be stockpiled, sampled, and covered. Based on the results of soil profiling, the <br />soil will be transported to an appropriate landfill for disposal. Following completion of