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GAVIN NEWOOM <br /> 111x e•.) GOVERNOR <br /> W� <br /> PAuronxlA JMRED AITARY MENFELD <br /> Water Boards ENVIRONME fOn <br /> ENVIRONMENTAL PROTECTION <br /> Central Valley Regional Water Quality Control Board <br /> 30 December 2019 <br /> Lori Toccoli <br /> Mcllrath Family LTCPTP <br /> P.O. Box 326 <br /> Stockton, CA 95201 <br /> RESPONSE TO CLOSURE REQUEST AND WORK PLAN, JAMAR SERVICE, 4075 E. <br /> MAIN STREET, STOCKTON, SAN JOAQUIN COUNTY, LUST CASE #391042 <br /> Central Valley Regional Water Quality Control Board (Central Valley Water Board) staff <br /> reviewed the following documents submitted on your behalf by ATC Group Services Inc. <br /> (ATC) for the Jamar Service underground storage tank petroleum release case at 4075 E. <br /> Main Street in Stockton (Site): <br /> • Revised No Further Action Request & First Semi-Annual Monitoring Report 2019 <br /> (Revised Closure Request), dated 9 November 2019; <br /> • Work Plan for Additional Off-Site Assessment Activities (Work Plan), dated 11 <br /> November 2019. <br /> In the Revised Closure Request, ATC uses statistical and regression analyses to model the <br /> Site plume and the expected maximum future downgradient extent of methyl tert butyl ether <br /> (MTBE) in groundwater. While ATC's statistical analysis does indicate an increasing trend in <br /> MW-10C MTBE concentrations, ATC states that the regression analysis modeling indicates <br /> that MTBE will not adversely affect any downgradient domestic water supply wells or other <br /> sensitive receptors. ATC also evaluates Site conditions against criteria established in the <br /> State Water Resources Control Board's Low Threat Underground Storage Tank Case <br /> Closure Policy (LTPC). ATC concludes that Site conditions meet all of the General and <br /> Media-Specific criteria of the LTCP, and recommends case closure, following additional <br /> assessment of downgradient groundwater conditions to confirm the accuracy of their <br /> modeling. <br /> To confirm the accuracy of the modeling, in the Work Plan ATC proposes to advance a cone <br /> penetrometer test (CPT) boring approximately 350 feet east (downgradient) of MW-6C, to a <br /> total depth of 110 feet below ground surface (bgs; groundwater zone C). ATC proposes to <br /> collect lithological data using CPT technology, and to collect a groundwater sample from total <br /> depth. <br /> Central Valley Water Board staff has the following comments: <br /> KARL E. LONGLEY SCD, P.E., CHAIR I PATRICK PULUPA, ESC., EXECUTIVE OFFICER <br /> 11020 Sun Center Drive 0200, Rancho Cordova, CA 95670 1 www.waterboards.ca.gov/centrolvalley <br />