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Eu -,ND G t <br />C1LIl O11M1• <br />Water Boards <br />Central Valley Regional Water Quality Control Board <br />23 August 2018 <br />Mr. Joshua Hernandez Zavala <br />General Services Department <br />San Joaquin County <br />44 North San Joaquin Street, Suite 590 <br />Stockton, CA 95202 <br />San Joaquin County Records Center, 630 North California Street, Stockton, San Joaquin <br />County <br />Central Valley Regional Water Quality Control Board (Central Valley Water Board) staff <br />reviewed the Subsurface Investigation Work Plan (Work Plan) dated 21 June 2018, submitted <br />on your behalf by Condor Earth (Condor). Condor prepared the Work Plan in response to a <br />29 August 2017 Central Valley Water Board letter. <br />In the Work Plan, Condor proposes to advance two soil borings, HA2 and HA3, using a hand <br />auger to collect shallow soil samples. Condor will collect one soil sample from each boring from <br />4.5 to 5 feet below ground surface (ft bgs). Condor will analyze soil samples for total petroleum <br />hydrocarbons as gasoline (TPH-G), TPH as diesel (TPH-D), benzene, toluene, ethylbenzene, <br />total xylenes (collectively BTEX), 1,2-dichloroethane (1,2 -DCA) <br />Central Valley Water Board staff have the following comments: <br />1. Central Valley Water Board staff concur with collection of shallow soil samples to allow <br />for comparison with low risk closure criteria outlined in the State Water Resources <br />Control Board's Petroleum Underground Storage Tank Low Threat Closure Policy <br />(LTCP). Please submit a Results Report by 30 November 2018. <br />2. In the Work Plan, Condor concluded that the lateral and vertical extent of petroleum <br />impacts to groundwater from the release at the Site have been adequately assessed by <br />existing Site data, and data collected as part of the investigation of the adjacent <br />Stallworth Auto Detail property at 602 North California St., Stockton (Stallworth <br />Property). Central Valley Water Board staff does not concur with Condor's conclusion. <br />The lateral extent of petroleum hydrocarbons in shallow groundwater has not been <br />assessed to the northeast, north, northwest, or west of well MW -1. In addition, vertical <br />delineation at the Site has not been completed, at this time it is unknown if the release at <br />KARL E. LONGLEV SCD, P.E., CHAIR I PATRICK PULUPA, ESO., EXECUTIVE OFFICER <br />11020 Sun Center Drive 0200, Rancho Cordova, CA 95670 1 www.waterboards.ca.gov/centralvallei <br />4i RECYCLED PAPER <br />