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Mr. Tom Kaldenbach March 8, 2013 Page 4 Other than the dissolution of metal oxides in the mine wall rock, which will be addressed through pre - filtration processes in the RO treatment plant, there is no expected effect of organic carbon on the RO treatment process. As noted in response "d" above, the organic carbon will increase the density of the RO Slurry and hasten the deposition of the beneficial carbon source at the bottom of the mine pool. 28. (This comment is intended to address comment 4 from DRMS's August 29 letter.) Please provide a printout of results of model projections for the RO system. Attachment 2 to this letter is a printout of the Toray Industries, Inc. modeled results of specified RO treatment on Schwartzwalder mine water. Specifically, Item 3, on page two shows constituent concentrations in the mine water (feed) and the resultant concentrations post treatment in both the RO Retentate and the RO product or permeate. 29. (This comment is intended to address comment 5 from DRMS's August 29 letter.) Please provide a contingency plan for disposing RO residuals outside the mine pool, should pilot - scale testing or full -scale testing indicate returning the residuals to the mine pool is not feasible. Returning RO residuals to the mine pool, incorporated in backlit( slurry, under a UIC permit by rule. is not only feasible but desirable. Further, Cotter is not convinced a feasible off -site option exists. The RO Retentate prior to barium chloride addition will be water with dissolved constituents present, including sulfates, manganese, uranium, radium and molybdenum. Cotter is not aware of commercial off -site disposal options for such a mixture of materials. Cotter has previously evaluated on -site storage in ponds with water content reduced via evaporation. However, it is neither certain that regulatory approval for such an undertaking can be achieved from the multiple agencies involved nor that the placement of ponds is achievable considering site geography. 30. Please describe your involvement with EPA regarding the UIC permitting requirements fbr the work proposed in your submittal. Cotter is working closely with EPA regarding the UIC permitting framework and requirements. It has provided additional information to EPA in response to an EPA request for information. 31. Please provide a contingency plan and schedule for a scenario in which UIC permitting cannot be completed in time for meeting the schedule shown in Figure 3. In the event that an extension of the March 31, 2013 date in the September 18, 2012 Mined Land Reclamation Board ("MLRB ") Order is needed, Cotter will pursue such an extension at the March 2013 MLRB meeting. 32. Please commit to having the installation of the well in the south waste rock pile overseen by a knowledgeable a trained hydro- geologist /geologist, and also commit to utilizing experienced personnel for correctly installing the well.