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IP-RZ, <br /> GAVIN NEWSOM <br /> GOVERNOR <br /> C0.LI i0 R LI I• JAIREo NFELD <br /> SECRETARRY FOR <br /> Water Boards ENVIRONMENTAL PROTECTION <br /> Central Valley Regional Water Quality Control Board <br /> May 18, 2020 <br /> Andrew Richle <br /> Water Plant Superintendent <br /> City of Lodi <br /> 2001 W. Turner Road <br /> Lodi, CA 95242 <br /> REVIEW OF CENTRAL PLUME SOURCE AREA GROUNDWATER EXTRACTION <br /> AND SOIL VAPOR EXTRACTION SYSTEMS CLOSURE REPORT, LODI, SAN <br /> JOAQUIN COUNTY <br /> Staff of the California Regional Water Quality Control Board, Central Valley Region <br /> (Central Valley Water Board) reviewed the May 12, 2020 Central Plume Source Area <br /> Groundwater Extraction and Soil Vapor Extraction Systems Closure Report prepared by <br /> Civil Hydro Tech on behalf of the City of Lodi (City). The report presents the results of <br /> indoor air and soil gas sampling in the Central Plume source area and includes a plan to <br /> close out the existing remediation systems and conduct targeted remediation and <br /> continued monitoring. <br /> The Central Plume source area is generally located within the City block bounded by <br /> Pine Street, Church Street, Pleasant Avenue, and Oak Street. Between 2003 and April <br /> 2011, five soil vapor extraction (SVE) pilot studies were performed within the Central <br /> Plume source area. These pilot studies removed a total estimated tetrachloroethene <br /> (PCE) mass of 15,385 pounds. In April 2011, the City started up the current SVE <br /> system that includes eighteen SVE well pairs at nine locations, two blowers, and three <br /> 8,000-pound vapor phase granular activated carbon vessels. As of September 2018, <br /> the current SVE system removed an estimated PCE mass of 2,363 pounds. In February <br /> 2019, the City shut down the SVE system and collected rebound samples in March <br /> 2019. <br /> In April 2011, the groundwater extraction and treatment (GWET) system started <br /> pumping from two groundwater extraction wells (EW-4 and EW-5) but was turned off in <br /> November 2011 due to low concentrations of PCE in the influent. The GWET system <br /> was restarted in April 2012 with newly installed EW-6. The highest influent <br /> concentration of PCE observed from EW-4 and EW-5 was 8.0 micrograms per liter <br /> KARL E. LONGLEY SCD, P.E., CHAIR I PATRICK PULUPA, ESQ., EXECUTIVE OFFICER <br /> 11020 Sun Center Drive#200, Rancho Cordova, CA 95670 1 www.waterboards.ca.gov/centralvalley <br />