1998-02-22_GENERAL DOCUMENTS - M1983052

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Knight Pksold Ms. Christina L. Kamni ar -2- January 28, 1998 Environmental Protection Specialist 3) Evidently, some acid either in the rock or the treatment process used up calcite and dolomite, and yields a residue that produces a lower pH than the original rock. The observations regarding the lower pH in the residue is correct. The material does appear lose the ability to buffer the solution to a neutral pH. Although the buffer capacity may be reduced in the process, the material does not generate acid. This is based on the observation that the pH of the solution added to the residue for the SPLP testing was at 5.00 +/-0.05. The final pH of the leachate was 5.4. This is evidence that the residue material is either benign or has a slight buffering capacity. 4) Nitrogen components decrease while Na, 7DS and some of the radionuclides increase. This does not appear to comport with gravity separation processes that are described in the permit documents. The processing of the ore which will occur in Wyoming does not include gravity separation for recovery of the metals. The new process consists of a form of chloride leaching. Because of this, the Na and chloride levels increase. The increase in TDS is C�, accounted for by the increase in sodium and chloride. The increase in the radionuclides, �a vrt specifically gross alpha, is a result of the increase in TDS. Testing for gross alpha is °Q� �yV, affected by the TDS. When TDS is high, the sample requires dilution to obtain a gross 7� , alpha reading. By diluting the solution, the +/- error for the sample increases. The +/- t error for the three ore samples ranges from 2.2 to 2.8. The +/- error for the residue sample, which has a TDS nine times higher than the ore samples, is 8.2. 5) Given the complimentary increase in Na and Cl, it seems feasible that alkaline chlorination may be involved,- however, the latest revisions to the permit indicate that the operation will not use chemicals that could make the operation a DMO. Perhaps this issue needs to be addressed further. DMG obviously is not opposed to chemical processing as long as there are adequate on-site protections, but any on-site processing must at least be identified in the permit. The proprietary process being developed by Elkhead Joint Venture is a form hloride leaching process which accounts for the increased Na and Cl in the residue. As previously mentioned, Elkhead Joint Venture understands that the DMG will likely need to know the process prior to allowing placement of tailings back in the pits. The processing will occur in Wyoming, but if revisions need to be made to the existing permit in regard to processing, we will submit the needed request for those revisions.