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- ✓1 EDMUND G.BROLYN.JR. <br /> / OOVCRNOR <br /> C A L I I O R N I A MMTHE'.V RODRIOUEZ <br /> EECRETARV FOR <br /> WaterBoards ER'JiRORMENTAL PFDTECIION <br /> i Central Valley Regional Water Quality Control Board <br /> i <br /> 25 September 2018 <br /> Mr, Roger Smith <br /> Glenn Springs Holdings, Inc. <br /> 5005 LBJ Freeway, Suite 1350 <br /> Dallas, TX 75244-6119 <br /> REVIEW OF SITE CHARACTERIZATION WORK PLAN, AND SITE CHARACTERIZATION <br /> WORK PLAN ADDENDUM, FORMER OCCIDENTAL CHEMICAL CORPORATION FACILITY, <br /> LATHROP, SAN JOAQUIN COUNTY <br /> Staff of the California Regional Water Quality Control Board, Central Valley Region (Central <br /> Valley Water Board) has reviewed the Site Characterization Work Plan (Work Plan), dated 22 <br /> June 2018, and the Site Characterization Work Plan Addendum (Addendum), dated 10 <br /> September 2018. The Work Plan and the Addendum were prepared by Geosyntec Consultants, <br /> Inc. (Geosyntec) on behalf of Glenn Springs Holdings, Inc., (GSH) for the former Occidental <br /> Chemical Corporation manufacturing facility (Site). The Site is located at 16777 South Howland <br /> Road in Lathrop, San Joaquin County. The main chemicals of concern associated with the Site <br /> j are 1,2-Dibromo-3-chloropropane (DBCP), ethylene dibromide (EDB), and 2,3,4,5- <br /> tetrahydrothiophene-1,1-dioxide (sulfolane). <br /> The original Work Plan has already been approved in an email dated, 27 June 2018. This letter <br /> serves as a formal approval of the Work Plan and the Addendum. <br /> The Work Plan and the Addendum proposes to advance 10 soil borings 1 to 10, and install <br /> groundwater monitoring wells to understand the vertical and lateral extent of the sulfolane plume <br /> between the onsite source area and the municipal water supply wells. The data will also be <br /> used to evaluate potential remedial alternatives to protect the private water supply wells and <br /> municipal water supply wells. <br /> The Addendum proposes a revised monitoring well design that was presented in the original <br /> Work Plan based on the requirements from San Joaquin County Environmental Management <br /> Department (County). The County has required that the cement grout annular seal be poured in <br /> a single lift for all monitoring wells. Therefore, all monitoring wells will be constructed with low- <br /> carbon-steel casings and stainless-steel screens instead of Schedule 80 PVC to avoid <br /> compromising the integrity of the well casing due to heat generation during curing of the grout. <br /> jKARL E. LGNGLEY SCD, P.E.,CHAIR I PATRICK PULUPA,ESQ.,CXECUTIVE OFFICER <br /> i <br /> 11020 Sun Center Drive it200,Rancho Cordova,CA 95670 I www.waterboards.aa.gov/centralvalley <br /> `�RECYCLED P-PER <br />