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0 <br />cotter <br />Via Email <br />49April 21, 2015 <br />Michael Cunningham <br />Division of Reclamation, Mining & Safety <br />Department of Natural Resources <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />pA e 1 C177•306 <br />Subject: I&Reply to DRMS's Comments in Letter to John Hamrick dated April 1, <br />Dear Mr. Cunningham: <br />Please find below, Cotter Corporation's (N.S.L.) ("Cotter") reply to each of your comments <br />on our TR -22 request that you sent in the subject letter. I first list the comment from DRMS <br />followed by Cotter's response. <br />The proposed grouting plan calls for re -boring and grouting boreholes which were <br />drilled in the Sump 10 Area in 2012. The existing boreholes have been identified as <br />the source of water seeping into the Sump 10 Area. Please indicate if water was <br />seeping into this area prior to drilling the boreholes in 2012. If so, please specify the <br />approximate amount of water which was inflowing into the sump. <br />Water was being captured and pumped from the Sump 10 area prior to drilling the <br />boreholes in 2012. However, the rate of inflow could not be quantified Cotter can report <br />the volume of water pumped from Sump 10 to the Water Treatment Plant ("WTP') for the <br />first four months of 2012 was approximately 24 gpnc This rate of pumping from Sump 10 <br />varied substantially as a result of operational conditions at the site (WTP operational <br />status, other sump conditions and weather related runoff and alluvial flow), and should <br />not be considered a reliable indicator of inflow into the Sump 10 area <br />2. The proposed grouting plan calls for grouting 19 holes in the first phase of the <br />project. The Operator has stated that after 2-3 days, an inspection of the Sump 10 <br />Area will be made to determine the effectiveness of Phase 1 and that based on the <br />results up to 19 additional holes may be drilled and grouted. Please specify the <br />criteria which will be used to determine if Phase I of the grouting program is <br />effective. <br />The effectiveness of Phase I will be based on the visual observation, estimated flow rates of <br />any seeping water in the grouting area and the results of the packer testing performed on <br />each Phase I borehole. The packer testing will measure the permeability of the area <br />adjacent to the borehole. This data will be evaluated by the grouting contractor and Cotter <br />Cotter Corporation (N.S.L.) Telephone (720) 554-6200 <br />7800 E. Dorado Place, Ste. 210 Fax (720) 554-6201 <br />Greenwood Village, CO 80111 <br />