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DIVISION OF RECLAMATION, MINING AND SAFETY <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 866 -3567 <br />FAX: (303) 832 -8106 <br />August 30, 2012 <br />Mike Thompson <br />Reardon Steel LLC <br />18050 County Road G <br />Cortez, CO 81321 <br />Re: Camp Bird Mine, Permit M- 1982 -090, Technical Revision TR -4, Adequacy Review Letter. <br />Dear Mr. Thompson, <br />STATE OF COLORADO <br />The Division has reviewed the above -named technical revision, which you submitted on behalf of Camp <br />Bird Colorado, Inc. We have identified a few technical adequacy issues that must be addressed. Many of <br />the questions relate to details pertaining to permanent structures and/or how the bond will be calculated. <br />Please respond to each of the following items. <br />To prepare the storage building site, the Graded Area #2 cap material will be stripped and stockpiled <br />against the toe of the hill. The map indicates that the stockpile will cover the existing stormwater <br />drainage conveyance ditch. Please describe how and where this stormwater control structure will be <br />replaced or relocated, if at all. <br />Graded Area #1 will be developed into a level area between stockpiles of stripped surface material and <br />the material excavated from the sediment pond. Please provide more information about the configuration <br />of the stockpiles, such as slopes and heights. A cross - section diagram of the present and proposed <br />surfaces there would be helpful (oriented at approximately NI 5 °E — S 15 °W). <br />Please provide more information about the buried pipeline, such as depth, pipe bedding, CMP joints, <br />compaction of backfill, outlet structure, etc. <br />Does the length of time water is detained in the sediment pond depend on the permeability of the earthen <br />material lining the pond structure, or on the CMP outfall pipe itself? (Or does the residence time depend <br />on both of these factors ?) <br />If the volume and detention time of the water in the sediment pond depends on the outfall pipe, please <br />provide design information about the planned elevation of the outfall pipe and the elevation of the water <br />surface at pond capacity. A cross- section diagram will be helpful here also. <br />Office of <br />Miner! 1 and Reclamation <br />Page 1 <br />COLORADO <br />D I V I S I O N OF <br />RECLAMATION <br />MINING <br />— &— <br />SAFETY <br />John W. Hickenlooper <br />Governor <br />Mike King <br />Executive Director <br />Loretta E. Pineda <br />Director <br />Office of <br />Denver • Grand Junction • Durango Active and Inactive Mines <br />