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Califor Regional Water Quality O ntrol Board ry <br /> Central Valley Region <br /> Katherine Hart, Chair <br /> 11020 Sun Center Drive,#200,Rancho Cordova,California 95670-6114 <br /> Matthew Rodriquez (916)464-3291 •FAX(916)464-4645 Edmund G.Brown Jr. <br /> Secretary for http://www.waterboards.ca.gov/centralvalley Governor <br /> Environmental ProtectionR- ECEIVED <br /> 26 August 2011 0011 <br /> Lf`OONMEN-AL HEALTH <br /> Mr. Nam Baek PERMWSEAVICES <br /> Glenn.Springs Holdings, Inc. <br /> 5005 LBJ Freeway, Suite 1350 <br /> Dallas, TX '75244-6119 <br /> REVIEW OF THE SULFOLANE REMEDIAL INVESTIGATION REPORT AND WORK PLAN,' <br /> FORMER OCCIDENTAL CHEMICAL COMPANY LATHROP FACILITY, 16777 HOWLAND <br /> ROAD, LATHROP, SAN JOAQUIN COUNTY <br /> Staff of the California Regional Water Quality Control Board, Central Valley Region (Central <br /> Valley Water Board) have reviewed the July 15, 2011 Sulfolane Remedial Investigation Report <br /> and Work Plan (Work Plan) for the Former Occidental Chemical Company Lathrop Facility, <br /> 16777 Howland Road, Lathrop, San Joaquin County (Site), prepared by ARCAD,IS US, Inc. <br /> (ARCADIS) on behalf of Glenn Springs Holdings, Inc. (GSH). Historical operations onsite <br /> resulted in a release of the pesticides 1,2-dibromo-3-chloropropane (DBCP) and ethylene <br /> dibromide (EDB), and the solvent 2,3,4,5-tetrahydrothiophene-1,1-dioxide (sulfolane) to soil <br /> and groundwater underneath the Site. GSH has operated a groundwater extraction and <br /> treatment system since 1982 to remediate the groundwater. In May 2009, GSH submitted a <br /> feasibility study work plan to evaluate four remedial alternatives including natural attenuation, <br /> in-situ soil washing, in-situ chemical oxidation, and soil excavation. In that report, GSH <br /> recommended natural attenuation. In a 16 November 2009 letter, Central Valley Water Board <br /> staff approved natural attenuation as the recommended remedial alternative for sulfolane. <br /> GSH submitted the Work Plan to propose additional remediation of sulfolane in soil-to <br /> expedite the path to closure. <br /> Based on a 2008 soil investigation, GSH proposed cleanup goals of 8.6 mg/kg for sulfolane in <br /> soil and 57 pg/L for groundwater. Centrai Valley Water Board staff concurred with the <br /> proposed cleanup goals in a letter dated 16 March 2009. <br /> In April 2011, GSH performed soil and groundwater investigations onsite to assess the lateral <br /> and vertical extent of sulfolane in soil and groundwater in the vicinity of PW26. The work was <br /> performed according to the April 12,. 2011 Revised Sulfolane Remedial Investigation Work <br /> Plan. CPT borings advanced during this investigation indicate that the soil beneath the Site <br /> consists of interbedded sands, silts, and clays from the surface to approximately 90 feet below <br /> ground surface (bgs). Sulfolane concentrations above the site-specific soil cleanup goal of 8.6 <br /> mg/kg were detected from 8 locations out of 22 soil borings. Groundwater samples collected <br /> from water bearing zones at 20, 35 and 60-70 feet bgs contaminated up to 31,000 pg/L, <br /> 50,000 pg/L and 5,200 pg/L respectively, exceeding the Site cleanup goal of 57 fag/L. <br /> California Environmental Protection Agency <br /> ��Recycled Paper <br />