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14:001 <br />Water Boards <br />EDMUND G. Gnown. <br />GOVERNOR <br />...cs, MATTITE: FO FLODRIOUEZ <br />SECRETA <br />ENVIRONMENTAL PROTECTION <br />S. . <br />Central Valley Regional Water Quality Control Board <br />September 27, 2017 <br />Andrew Richle <br />Water Plant Superintendent <br />City of Lodi <br />2001 W. Turner Road <br />Lodi, CA 95242 <br />REVIEW OF WORK PLAN FOR DESTRUCTION OF MID-PLUME EXTRACTION WELL EW-7, <br />LODI CENTRAL PLUME, LODI, SAN JOAQUIN COUNTY <br />Staff of the California Regional Water Quality Control Board, Central Valley Region (Central <br />Valley Water Board) reviewed the September 21, 2017 Work Plan for Destruction of Mid-Plume <br />Extraction Well EW-7 prepared by West Yost Associates on behalf of the City of Lodi (City). The <br />work plan provides details for the planned destruction of recently installed extraction well EVV-7 <br />that was found to have an unexpectedly low yield. <br />In October 2016, the City installed EW-7, a 6-inch diameter extraction well near the intersection <br />of Church Street and West Tokay Street to address tetrachloroethene (PCE) mass in the middle <br />portion of the Central Plume. A treatment system was constructed on the adjacent Needham <br />Elementary School property. This location is approximately 2400 feet down gradient of the <br />Central Plume source area. PCE at this location is encountered primarily in the intermediate <br />depth zone between 75 and 125 feet. Extraction well EW-7 was constructed with a screen <br />interval of 75 to 125 feet and a planned extraction rate of 50 gallons per minute. However, when <br />tested during startup, EW-7 was found to yield less than 1 gallon per minute. Therefore EW-7 <br />could not meet its design purpose of capturing and containing the PCE contamination in the <br />mid-plume area. <br />The City plans to drill and install a replacement extraction well for EW-7 in October 2017 as <br />approved by Central Valley Water Board staff in a letter dated April 20, 2017. To destroy the <br />existing low yield extraction well, the City proposes to over-drill the well to the total borehole <br />depth using a sonic drill rig. The existing well materials will be removed and neat cement will be <br />placed in the borehole through the drill casing. The documentation of the destruction of EW-7 <br />will be submitted along with the report of installation of the replacement extraction well EW-7R. <br />Central Valley Water Board staff concurs with the proposed destruction of extraction well EW-7. <br />Please notify Central Valley Water Board staff at least one week prior to conducting the field <br />activities. <br />KARL E. LONGLEY ScD, P.E., CHAIR I PAMELA C. CREEDON P.E., BCEE, EXECUTIVE OFFICER <br />11020 Sun Center Drive 4200, Rancho Cordova, CA 95670 ! wwv...waterboards.ca.govicentralvalley <br />C,‘, RECYCLED PAPER