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_ J <br /> San Joaquin County <br /> °"'" .� Environmental Health Department DIRECTOR <br /> 41� <br /> .ODonna Heran, REHS <br /> 600 East Main StreetPROGRAM COORDINATORS <br /> Stockton, California 95202-3029 RobertMcClellon,REHS <br /> Jeff Carruesoo,RENS,RDI <br /> • Website: www.sjgov.org/ehd Kasey Foley,REHS <br /> CIFOR <br /> Phone: (209) 468-3420 <br /> Fax: (209) 464-0138 <br /> May 11, 2010 <br /> Mr. Carl W. Knowles, Successor Trustee <br /> Knowles Family Trust Agreement <br /> P.O. Box 640 <br /> Woodbridge, CA 95258 <br /> Subject: 102 S Wilson Way <br /> Stockton, CA <br /> The San Joaquin County Environmental Health Department (EHD) has received and reviewed <br /> Workplan for Peroxide Injection Pilot Test (WPPT), dated February 19, 2010, which was <br /> submitted to address residual petroleum hydrocarbons and fuel additives that have impacted <br /> soil and groundwater underlying your site caused by the unauthorized release from the <br /> underground storage tank (UST) system formerly on your site. By electronic mail (email) <br /> correspondence between the EHD and your consultant, Ground Zero Analysis, Inc. (GZA), the <br /> EHD obtained additional information regarding the proposed pilot test. <br /> In the WPPT, GZAA proposes to conduct a long-term pilot test of insitu chemical oxidation to <br /> evaluate its efficacy and potential byproducts by monthly injections of approximately 1,000 <br /> gallons of a 10% hydrogen peroxide (HP) solution into the subsurface utilizing vapor wells <br /> VW-1, VW-2 and VW-6. These vapor wells are all located in the core area of the plume of <br /> impacted soil and groundwater, and all have screened intervals that favorably address both <br /> impacted media. If not overly reactive, the HP solution will be increased to 20% over time. <br /> Groundwater samples representative of background conditions and test conditions will be <br /> collected and analyzed for total petroleum hydrocarbons quantified as gasoline (TPHg), <br /> benzene, toluene, ethylbenzene and total xylenes (BTEX), 1,2-dichloroethane (1,2-DCA), <br /> ethylene dibromide (EDB), general minerals, dissolved minerals (CAM-17 metals identified in <br /> California Code of Regulations, Title 22), hexavalent chromium and bromate. In addition, the <br /> samples will be monitored utilizing field instruments for pH, temperature, specific conductance, <br /> dissolved oxygen and redox potential. GZA proposes to monitor the effects of HP injection <br /> quarterly. <br /> Via email, the EHD inquired of GZA about several aspects of the pilot test, including monitoring <br /> any potential displacement or dilution of the plume of impacted groundwater as a result of the <br /> proposed pilot test injections. GZA demonstrated, also via email, such an effect would be <br /> minimal based on the relative volumes of the injectant and impacted groundwater. GZA states <br /> that the plume margins are adequately monitored to detect any displacive plume migration. <br /> In WPPT, GZA did not provide a cost-effectiveness comparison of HP injection to other <br /> potentially effective remedial technologies. The site conceptual model (SCM) previously <br /> prepared by GZA, states that most of the impacted soil is now in the saturated zone, at depths <br /> Work Plan Approval Letter 0510 <br />