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<br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1313 Sherman 6[., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 866-3567 <br />FAX: (303) 832-8106 <br />November 19, 2002 <br />Mr. Eric Reckentine <br />Land Manager <br />Lafarge West, Inc. <br />1590 W. 12u' Avenue <br />Denver, CO 80204-3410 <br />RE :East Rigden Pit, Technical Revision No. TR-2, Adequacy Review, Permit No. M-1979-097 <br />Class: Revision, Type-Seq.: TR-2 <br />Dear Mr. Reckentine: <br />DIVISION OF <br />MINERALS <br />GEOLOGY <br />RECLAMATION <br />MINING•SAFETY <br />Bill Owens <br />Governor <br />Greg E Wakher <br />Executive Director <br />Ronald W. Cattany <br />Acting Division Director <br />The Division has reviewed your technical revision request for the East Rigden Pi[ regazding stability plans <br />and specifications for the Poudre River at Rigden Btidge. Listed below are adequacy review comments. <br />Please provide a response to [he comments listed below on or before the December 4, 2002 decision date. <br />1. Please provide specifications for "Type M" riprap to be applied azound vazious support stations. Other <br />technical information that will be useful is the volume of riprap needed, [he method of placement such <br />as end dumped or selective placement, and the level of hydrologic protection provided by the T ype M <br />riprap, ie: what is the hydrologic flow even[ and velocity that [he riprap is designed to withstand? <br />Please respond. <br />2. Please clarify whether the 5:1 slope between support stations 1+00 and 2+00 is already present or <br />whether the operator will need [o construct such a slope as part of the stabilization plans. Also, what <br />is the design purpose of the 5:1 slope? <br />3. Please clarify the reason for change in the limit of proposed concrete rubble. <br />4. If available, please define the flood stage elevation of the Poudre River at or near Rigden Bridge for <br />the 100-yeaz 24-hour flood event. <br />5. Please provide a discussion and timetable for all stabilization work to be done. <br />Once again, the Division will look forwazd to your response on or before December 4, 2002. Please call <br />me a[ (303) 866-3567 if you have any questions. <br />Sincerely, <br />Thomas A. Schreiner <br />Environmental Protection Specialist <br />