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Former Greer Constructior* • Page 2 <br /> 15634 S. Steinegul Road June 25, 2010 <br /> reason for the permanganate formation was not explored, nor was its extended impact on the <br /> proposed pilot test. <br /> Please submit an addendum to the Study that includes the following: <br /> 1. A detailed evaluation of the possible causes for failure of the bench scale test that <br /> includes the production of permanganate and a detailed contingency plan to mitigate the <br /> generation of hexavalent chrome, bromate and permanganate. <br /> 2. Identify the specific differences in conditions that may cause a more favorable result in <br /> the proposed pilot test than in the bench-scale test. Elaborate how those differences <br /> may lead to more favorable reaction pathways that either inhibit formation of hexavalent <br /> chromium and bromate or more rapidly promote their attenuation. <br /> 3. Calculations of sorbed and dissolved contaminant masses and a description of the mass <br /> distribution to be addressed by the remediation. <br /> 4. More detailed evaluations of the four remedial alternatives taking into consideration the <br /> remaining contaminant mass, specific site conditions, cost estimates and estimated time <br /> for cleanup; as much site-specific data as possible should be utilized for this evaluation. <br /> While it may not be possible to fully address all of the issues noted above, the EHD believes <br /> each should be addressed as well as possible to better understand what controls the formation <br /> and attenuation of the undesirable byproducts in order to justify approval of a pilot test following <br /> a bench-scale test with unfavorable results. Simply put, why should a more favorable result be <br /> expected in the subsurface than was obtained in the bench-scale test? This is especially <br /> important as the domestic well for the site is virtually in the treatment area. Fortunately, <br /> contaminants have not been detected in water samples from the well to date, but the margin for <br /> error may not be large. <br /> If you have any questions please call Lori Duncan at (209) 468-0337. <br /> Sincerely, <br /> Lori Duncan, REHS Nuel C. Henderson, Jr., PG <br /> Senior Registered Environmental Health Specialist Engineering Geologist <br /> c: James Barton, PG, CVRWQCB, 11020 Sun Center Drive#200, Rancho Cordova CA 95670 <br /> Jeanne Homsey, PE, ATC, 1117 Lone Palm Avenue Ste 201, Modesto CA 95351 <br />