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Mr. Tom Kaldenbach <br />April 5, 2013 <br />Page 9 <br />table (i.e., the plan view area of the backfill, 4730 ft2). The calculated maximum seepage rate <br />(Q) is 6,622 ft3 /day or 34.4 gpm.] <br />As this analysis demonstrates, the backfill material will not become saturated and will not exert <br />hydraulic head on the two sealed bulkheads on the Steve Level. <br />25. Please add to Exhibit E a prediction of water quality discharges from the mine site that are <br />expected to occur during the time period when the water treatment plant will be moved from its <br />current location to the flat area near the Steve Portal. Please include a description of the water <br />quality control plan that will be followed during that time period. <br />Cotter intends to ensure that there are no adverse changes to water discharges from the mine site <br />during any phase of construction or operation. As such, Cotter plans to site the RO treatment <br />system in close proximity to the Steve Portal, which will enable Cotter to dismantle the IX <br />building and treat what is expected to be minimal water collected via the installed array of sumps, <br />using the RO system. <br />26. Please identify the criteria that must be met before ceasing the mine pool pumping that <br />maintains the mine pool elevation at an elevation at least 150 feet below the Steve Level. <br />Please see Cotter's response to this comment submitted to DRMS on March 8, 2013, in reply to <br />AM -04 adequacy review comments regarding accelerated dewatering and in -situ treatment. <br />27. (This comment is intended to address comment 3, from DRMS's August 29 letter.) Returning <br />reverse osmosis (RO) concentrate to the water in the underground workings of a uranium mine, <br />while performing in -situ biologic treatment on the water, is a unique approach to mine water <br />treatment. The outcome of this approach may be unpredictable. Please provide a description of <br />a. Previous barrel testing of in -situ biologic treatment (see Section 10.2.2 of Schwartzwalder <br />Mine Hydrologic Evaluation of Mine Closure and Reclamation, 2007) <br />Please see Cotter's response to this comment submitted to DRMS on March 8, 2013, in reply to <br />AM -04 adequacy review comments regarding accelerated dewatering and in -situ treatment. <br />b. A plan for conducting pilot -scale testing of disposing RO concentrate and in -situ biologic <br />treatment inside the pumped down mine pool prior to full -scale disposal and treatment inside the <br />pumped down mine pool <br />Please see Cotter's response to this comment submitted to DRMS on March 8, 2013, in reply to <br />AM -04 adequacy review comments regarding accelerated dewatering and in -situ treatment. <br />c. The expected secondary effects resulting from the creation of strongly reducing conditions in <br />the mine pool <br />Please see Cotter's response to this comment submitted to DRMS on March 8, 2013, in reply to <br />AM -04 adequacy review comments regarding accelerated dewatering and in -situ treatment. <br />d. The expected effect of RO treatment residuals on the mine pool treatment process <br />