Laserfiche WebLink
__°61 <br />0 00 <br />1•• <br />Water Boards <br />EDMUND G. BROWN JR. <br />fv1ATTNEW RODRIQUEZ <br />5E0RET/1AV fOR <br />FWV,P0.14.1111. POOTECTION <br />Central Valley Regional Water Quality Control Board <br />April 20, 2017 <br />Andrew Richle <br />Water Plant Superintendent <br />City of Lodi <br />2001 W. Turner Road <br />Lodi, CA 95242 <br />REVIEW OF RECOMMENDED LODI CENTRAL PLUME MID-PLUME REPLACEMENT <br />EXTRACTION WELL LOCATION, LODI, SAN JOAQUIN COUNTY <br />Staff of the California Regional Water Quality Control Board, Central Valley Region (Central <br />Valley Water Board) reviewed the April 18, 2017 Technical Memorandum Recommended Lodi <br />Central Plume Mid-Plume Replacement Extraction Well Location prepared by West Yost <br />Associates on behalf of the City of Lodi (City). The memorandum provides an update on the <br />recent installation of a new groundwater extraction and treatment (GWET) in the middle portion <br />of the Lodi Central Plume. The memorandum includes recommendations for the location and <br />construction of a new extraction well to replace a recently installed extraction well that was <br />found to have an unexpectedly low yield. The memorandum results and recommendations were <br />also discussed during a March 29, 2017 meeting between the City and Central Valley Water <br />Board staff. <br />In April 2011, groundwater remediation in the Central Plume began at the source area with a <br />GWET system that pumped from two source area groundwater extraction wells (EW-4 and EW- <br />5). These wells were turned off in November 2011 due to low concentrations of PCE in the <br />influent. Both EW-4 and EW-5 were constructed with screens starting below 100 feet deep, <br />while PCE pollution at the source area appeared to be predominantly in shallower groundwater. <br />The source area GWET system was restarted in April 2012 with newly installed EW-6, which <br />was constructed with a screen from 50 to 90 feet deep. The influent concentrations of PCE in <br />EW-6 started at 2,100 micrograms per liter (pg/L), decreased to 100 pg/L by January 2013, and <br />further decreased to 32 pg/L as of July 2014. In August 2014, EW-6 was shut down and post- <br />shutdown sampling indicated steady or decreasing PCE concentrations. Between April 2011 <br />and July 2014, extraction wells EW-4, EW-5 and EW-6 removed approximately 26 pounds of <br />PCE from groundwater in the Central Plume source area. <br />Currently, the highest concentrations of PCE in the Central Plume are located down gradient of <br />the source area in the middle portion of the plume. To address the PCE mass in the middle <br />portion of the plume, the City installed a single new 6-inch diameter extraction well near the <br />,AHE E. LoNen..by ScD, P.E.. CHAIR I PAMELA C. CHEEDON P.E., SCEE. EXECUTIVE OFFICE, <br />11020 Sun Center Dnve 0200. Rancho Cordova, CA 95670 www.waterboarde.ca.govicentraivaney <br />FIFCVCI.F0 PAP1,1