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AO <br /> General Shale <br /> Building The American Dream® <br /> January 26, 2018 RECEIVED <br /> Colorado Department of Natural Resources FEB 0 7 2018 <br /> Division of Reclamation, Mining and Safety <br /> 1313 Sherman Street, Room 215 DMSION OF RECLAMATION <br /> Denver, Colorado 80203 MINING AND SAFETY <br /> Attention: Mr. Michael A. Cunningham <br /> Subject: Corrective Action Technical Revision 02 Adequacy Review No. 1 <br /> Chieftain South Mine, Permit No. M-1981-148 <br /> Dear Mr. Cunningham: <br /> General Shale Brick, Inc. (General Shale) is in receipt of your Technical Revision 02 Adequacy <br /> Review No. 1 letter dated January 4, 2018. General Shale is has the following responses in bold <br /> to your comments in italics: <br /> 1. The Operator is proposing to construct a temporary stormwater diversion ditch along the <br /> southern permit boundary to divert stormwater. The Division requests the following <br /> information: <br /> a. Specify the size of the storm event for which the stormwater diversion channel was <br /> designed. The Division requires temporary stormwater structures to be designed <br /> for a 25 year/24-hour storm event, while permanent stormwater structures must <br /> be designed for 100 year/24-hour storm event. <br /> The stormwater diversion channel was designed for a 100-year/24-hour storm <br /> event. <br /> b. Specify how long the temporary stormwater diversion channel will remain in place. <br /> The temporary stormwater diversion channel will remain in place until mining is <br /> complete and final reclamation begins for the entire mine site. <br /> c. Provide the results of any analyses which were used to design the stormwater <br /> diversion ditch. <br /> Please see enclosed preliminary drainage study by HMD Water. <br /> d. Clarify if the stormwater diversion ditch will be earth-lined. <br /> The outer slope will have riprap, the center of the ditch and the inner slope will <br /> be earth lined. The earth-lined areas will be seeded and turf reinforcement mat <br /> will be installed to minimize erosion. Please refer to enclosed Final Stormwater <br /> Drainage Channel Design drawing C-03 Plan and Profile, Drawing C-05 Ditch <br /> Details 1 and Drawing C-06 Ditch Details 2. <br />