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TDS <br />U <br />SO <br />Mo <br />Mn <br />Ra 226 <br />As <br />Ba <br />Fe <br />Cl <br />Mr. Tom Kaldenbach <br />April 5, 2013 <br />Page 3 <br />3. c. The expected secondary effects resulting from the creation of strongly reducing conditions in <br />the mine pool <br />Please see Cotter's response submitted to comment 27 below. <br />3d. The expected effect of RO treatment residuals on the mine pool treatment process <br />Please see Cotter's response submitted to comment 27 below. <br />3. e. The expected effect of organic carbon on the RO treatment process <br />Please see Cotter's response submitted to comment 27 below. <br />4. Please add to Exhibit E the printout of results of model projections for the RO system. <br />Please see Cotter's response submitted to comment 28 below. <br />S. Please add to Exhibit E a contingency plan for disposing RO residuals outside the mine pool, <br />should pilot -scale testing or full -scale testing indicate returning the residuals to the mine pool is <br />not feasible. <br />Please see Cotter's response submitted to comment 29 below. <br />6. Please add to Exhibit E the minimum criteria that must be met before the in -situ trial is <br />terminated and full -scale in -situ treatment begins. <br />In -situ treatment of the mine pool will occur in two stages, the first being the addition of a heavy <br />organic carbon source into the mine as part of the backfill slurry during initial dewatering, which <br />is expected to take up to four months. During this initial dewatering, mine pool conductivity, <br />oxidation /reduction potential (ORP), pH, and temperature will be monitored continuously. <br />Additionally, the constituents in the chart below will be analyzed on a monthly basis to <br />supplement Cotter's current quarterly mine pool analysis, which shall continue to be performed. <br />If beneficial effects from the initial addition of the heavy carbon source are confirmed, Cotter will <br />proceed with full -scale in -situ treatment of the mine pool at a level at least 150 feet below the <br />Steve level. <br />Table 1. Constituents to be Analyzed Monthly <br />7. Please add to Exhibit E the specific criteria that must be met before ceasing mine pool <br />pumping and before ceasing ex -situ active treatment of the mine pool. <br />Please see Cotter's response to comment 26 below. <br />8. Please add to Exhibit E a commitment to submit an amendment application when you propose <br />to cease mine pool pumping and ex -situ active treatment of the mine pool. This important <br />milestone will warrant DRIVE review and notice to the public. <br />