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© MWH IEC OVEDD <br /> BUILDING A BETTER WORLD <br /> November 17, 2008 NOV 1 9 2008 <br /> ENVIRONMENT HEALTH <br /> Steven Ross, P.E. PERMIT/SERVICES <br /> Department of Toxic Substances Control <br /> 8800 Cal Center Drive <br /> Sacramento, CA 95826 <br /> Siddharth Sewalia <br /> California Regional Water Quality Control Board <br /> Central Valley Region <br /> 11020 Sun Center Drive, Suite 200 <br /> Rancho Cordova, CA 95670 <br /> Re: Proposal for Supplemental Horizontal Injection Treatment in Horizontal Wells Beneath <br /> the Former Report Pit as part of the In-Situ Remedial Action Plan Amendment Activities <br /> Former Marley Cooling Tower Site,Stockton, California 95215 <br /> Dear Mr. Ross and Mr. Sewalia: <br /> At the request of the SPX Corporation (SPX), MWH Americas, Inc. (MWH) has prepared this letter <br /> proposing supplemental injection treatment using horizontal wells HT-1D and HT-2D, which are <br /> aligned and located beneath the former retort pit at a total depth of 40 feet below ground surface (bgs) at <br /> the Former Marley Cooling Towers Site, Stockton, California. This work is associated with the <br /> California Regional Water Quality Control Board (CRWQCB) Monitoring and Reporting Program <br /> (MRP) No. R5-2007-0126 and as part of the Waste Discharge Requirements (WDR) for the SPX <br /> Corporation — Marley Cooling Tower Company Stockton Facility, for the In-Situ Remedial Action Plan <br /> Amendment activities at the Former Marley Cooling Tower Site located in Stockton, California, with <br /> additional regulatory oversight by Department of Toxic Substances Control(DTSC). <br /> As discussed in the Remedial Action Implementation Work Plan, December 2007, re-dosing via the <br /> horizontal treatment wells may be necessary to remediate the elevated hexavalent chromium flushed <br /> down to groundwater from beneath the former retort pit area. The proposed supplemental injection <br /> treatment is based on a recent increase in hexavalent chromium reported in 41h Quarter 2008 <br /> groundwater samples collected from well MW-206, located immediately downgradient from the former <br /> retort pit(attached Figure 2). Hexavalent chromium was reported in groundwater samples collected from <br /> MW-206 at a concentration of 25,100 µg/1 in the 41h Quarter 2008 results, an increase from the 3`d <br /> Quarter 2008 results (3,240 µg/1). The attached Table provides data for MW-206 from the 3`d and 4`h <br /> Quarter of 2008. <br /> 3321 Power Inn Road TEL 9169248844 <br /> Suite 300 FAX 916 924 9102 <br /> Sacramento,California www.mwholobal.com <br /> 95826 <br />