2015-03-31_REVISION - C1981008 (2)

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COLORADO Division of Reclamation, Mining and Safety Department of Natural Resources 23 March 2015 To: Brock Bowles From: Robin Reilley Re: RE: New Horizon Mine (C1981 -008) Technical Revision TR 67 Dear Brock, I was asked to review the New Horizon Mine Technical Revision 67 which is incorporating the restoration plan of the BB Road west of 27.00 Road as approved by Montrose County and an update of the as -built drawing for Pond 008. Rules: 2.05.3 -(4), 4.03 -(4), 4.05.6, 4.05.9- (2)b,c Sediment Ponds: 1. The proposed as -built Map 2.05.3(3) -4 -2) shows a storage capacity of 0.063 AC /FT at elevation 5647.0 ft (bottom of pond) while the sedcad of March 2006 shows 0.00 ac /ft at the same elevation. Please clarify the proper storage capacity at the 5647.0 ft elevation for Pond 8. 2. Regarding the update of the as -built drawing of Pond 008, the Map 2.05.3(3) -4 -2 shows the drainage area to be 102.9 acres but the sedcad was run using 110.436 AC (Attach men tments 2.05.3(3) -4 -2 and 2.05.3(3) -4 -4). Please clarify the proper acreage for the drainage basin for Pond 8. In Attachmentments 2.05.3(3) -4 -2 and 2.05.3(3) -4 -4 of the approved permit, the units are inconsistent across the two analysis. The inconsistencies are in total area (AC vs SQ FT), gross erosion, total yeild, run -off volume, sediment volume and total volume. The Division cannot complete its review of the culvert change for Pond 8 with the curently approved sedcad runs. Please make units consistent across the input and output datasets in Attachmentments 2.05.3(3) -4 -2 and 2.05.3(3) -4 -4 and re- submit the sedcad runs of the Pond Volume Calculations for both the 10 and 25 year 24 hour events. 4. At the bottom of MAP 2.05.3(3) -4 -2, Exhibit 2.05.2 -18 is referrenced for more detail about the discharge structure of Pond 8. The Division was not able to located Exhibit 2.05.2 -18 in the permit but was able to review the discharge structure on Map 2.05.3(3) -4 -3. Please clarify the correct drainage structure detail map for Pond 8 on Map 2.05.3(3)4 -2. 5. With regards to the restoration of the BB Road west of 27.00 road sedcad analysis by the Division indicated that the proposed restoration was consistent with Rules 2.05.3 -(3)c Operation Plan, 4.03 -(4) Roads; and that the designs were consistent with the 10 and 24 year 24 hour events. Sincerely, of coLO� 1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http: / /mining.state.co.us I ryes o`N John W. Hickenlooper, Governor I Mike King, Executive Director I Virginia Brannon, Director * I87_6