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California Regional Water Quality Con rol Board <br /> Central Valley Region .e¢+ <br /> v Katherine Hart,Chair <br /> Arnold <br /> Linda S. Adams 11020 Sun Center Drive#200, Rancho Cordova,California 95670-6114 Schwarzenegger <br /> Secretary for Phone(916)464-3291 •FAX(916)464-4645 Governor <br /> Environmental http://www.waterboards.ca.gov/centralvalley <br /> Protection j <br /> Ms. Stephanie McKenna <br /> October 2010 <br /> Chevron Environmental Management Company UCf 2, 7 2010 <br /> 6001 Bollinger Canyon Road ENVIRUN!VitiV I HEALTH <br /> San Ramon, CA 94583 PERMIRERVICES <br /> DIRECTIVE LETTER, FORMER UNOCAL STATION #0187, 437 EAST MINER AVENUE, <br /> STOCKTON, SAN JOAQUIN COUNTY, CASE NOS, 390698 <br /> In a letter dated 10 September 2010, the San Joaquin County Environmental Health <br /> Department (SJCEHD) approved a workplan for a pilot study at this site, and added the <br /> condition that a permit for injections be submitted (must be obtained) or that Regional Board <br /> (staff) approval be given (to proceed with the pilot study without a permit). On <br /> 30 September 2010, Chevron Environmental Management Company (Chevron) consultant <br /> Arcadis submitted a complete Notice of Intent for Regional Board Waste Discharge <br /> Requirements R5-2008-0149 (NOI), to inject magnesium sulfate (Epsom Salt) and a tracer dye <br /> (fluoriscein) into the petroleum hydrocarbons groundwater plume at the above SJCEHD lead <br /> case. The pilot study injection is designed to produce sulfate, and to induce anaerobic <br /> degradation by sulfate-reducing bacteria that are present in groundwater. Approximately <br /> 13 grams (g) of Epsom salts will be mixed with each liter (L) of tap water, with an initial volume <br /> of 1 ,500 to 2,500 gallons of mixture injected per well, for a total of five injection wells. The <br /> fluoriscein, to be added to the initial injected mixture at a concentration of 40 milligrams per L, <br /> will be used to determine a dose response (time to reach) for five monitoring wells, existing <br /> U-3 and U-4, and new U-27A', U27B', and U-27B, to be located approximately 10 feet from <br /> three of the five injection points. The initial injection data will be used to design the Epsom <br /> salts solution concentrations and mixture quantities, and frequencies of future injections. In <br /> addition to petroleum hydrocarbons, the proposed permit monitoring will also track changes in <br /> sulfide/sulfate and salts concentrations. Background concentrations sampling will occur in <br /> November 2010. The NOI did not provide a time frame (duration) or number of injections for <br /> the pilot study. <br /> The first pilot study injection may proceed as previously approved by SJCEHD, prior to <br /> obtaining the injection permit. Subsequent pilot study injections will require my evaluation of <br /> the initial data and my written notice to proceed. Please provide the initial injection data <br /> (results) to me by email with a schedule for subsequent injections. You may contact me <br /> rQnarding questionphone at (916) 464-4615; or by e-mail at j_barton(a�waterboards.ca.gov. <br /> s' ,(l�j S�J�i <br /> James L.L. Barton, P.G. <br /> Engineering Geologist <br /> cc: Lori Duncan, San Joaquin County Environmental Health Department, Stockton <br /> Toyna Meyers, Arcadis, 950 Glenn Dr., Ste. 125, Folsom 95630 <br /> California Environmental Protection Agency <br />