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SECOR www.secor.com <br /> INTERNATIONAL 3017 Kilgore Road,Suite 100 <br /> S E C O R INCORPORATED Rancho Cordova,CA 95670 <br /> 916.861-0400 TEL <br /> 918.(861-04330 FAX <br /> July 22, 2004 `— E `! <br /> AUG 1 6 2004 <br /> Mr. James Barton ENVIRONMENT HEALTH <br /> Central Valley Regional Water Quality Control RWQCB PERMIT/SERVICES <br /> 11020 Sun Center Drive, Suite 200 <br /> Rancho Cordova, CA 95670-6114 <br /> RE: Field Test Program for Evaluation of Oxidation Capacity of Groundwater <br /> 7-Eleven Store#14117 <br /> 2725 Country Club Boulevard <br /> Stockton, California 95204-3937 <br /> SECOR Project No.: 77EL.14117.04.0104 <br /> Dear Mr. Barton: <br /> This field test program, prepared by SECOR International Incorporated (SECOR) on behalf <br /> of 7-Eleven Inc., proposes evaluating the oxidation capacity of the groundwater resource at <br /> 7-Eleven Store #14117 (Figures 1 and 2). Mr. Michael Infurna of the San Joaquin County <br /> Environmental Health Department (SJCEHD) responded to SECOR's submittal of a Work <br /> Plan for Interim Remediation and Oxygen Injection Feasibility Test, commenting that the <br /> Central Valley Regional Water Quality Control RWQCB (RWQCB) has recently advised that <br /> a Waste Discharge evaluation may be required to inject oxygen into groundwater. <br /> Furthermore, SECOR understands that the RWQCB is considering bench scale testing as a <br /> means to evaluate potential impacts to groundwater quality from oxygen injection. <br /> SECOR proposes the installation of one oxygen injection test well and injecting oxygen to <br /> evaluate potential impacts to groundwater quality resulting from (1) reactions between the <br /> injected oxygen and the groundwater, and (2) reactions between the injected oxygen and <br /> the subsurface lithologies. Such a program will effectively address concerns of the <br /> RWQCB regarding potential impacts to groundwater quality from oxygen injection and <br /> results will be more applicable and representative compared to bench scale testing. <br /> GENERAL PROJECT APPROACH <br /> Oxygen injection is utilized as a remedial method to enhance biodegradation of dissolved <br /> petroleum hydrocarbons. However, there is concern that injection of oxygen into <br /> groundwater may promote oxidation of dissolved constituents and/or oxidation of the <br /> aquifer lithologies and impact water quality through production of oxidized species, e.g., <br /> Cr207 2 or Cr04 2, both forms of Cr+6 stable in aqueous environments and which are <br /> considered a health hazard. In addition, oxidation of dissolved constituents may promote <br /> formation of insoluble precipitates, e.g., Fe00H, that impair aquifer characteristics and foul <br /> well screens. <br /> Reaction of groundwater and aquifer lithologies with injected oxygen is minor due to the <br /> capacity of the dissolved oxygen to remain at high concentrations and the limited radius of <br /> influence as it migrates outward from the injection well through the aquifer. The aquifer <br /> would also tend to buffer the oxidation reactions such that reaction products would be <br /> I:\7-Eleven\7-11 Stores\14117\Workplans <br />