2016-02-26_REVISION - C1981008 (10)

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COLORADO Division of Reclamation, Mining and Safety Department of Natural Resources 1313 Sherman Street, Room 215 Denver, CO 80203 February 26, 2016 To: Brock Bowles From: Jason Musick RE: New Horizon Mine, C-1981-008 TR -70, Adequacy Review Memo Per your request, I have reviewed the proposed new sediment pond (Pond 016) and the proposed new postmining drainage which includes the new Tailwater and the channel below the tailwater ditch designs associated with the above referenced revision. The review included the proposed designs to determine if the if the demonstrations meet the design criteria for Rules 4.05.3 and 4.05.6. Based on the Division's review of the existing Pond(s) 009, 012, 013, 015, and new Pond 016 designs, the ponds are designed and constructed to meet the revised postmining drainage requirements for the newly modeled and proposed postmining topography delineated watersheds. The Division has the following adequacy comments: 1. Approved Attachment 2.05.3(3)-1 provides collection/ diversion ditch and culvert design parameters for the New Horizon Mine. Based on a review by the Division, a revised Attachment 2.05.3(3)-1 was not included which would contain the addition of the proposed collection ditch below the Tailwater ditch. In addition, there is no discussion of the existing Tailwater Ditch in Attachment 2.05.3(3)-1. Please revise Attachment 2.05.3(3)-1 to include all proposed ditches and culverts throughout the mine site or provide revised text to discuss the omission of the designs in Attachment 2.05.3(3)-1 and inclusion in another portion of the PAP. Approved Map 2.05.3(3)-1 delineates Ditches C-10 draining a basin of 5.2 acres to Pond 013 and D1 W draining a basin of 25.1 acres to what appears to be Pond 015. Both C-10 and D1 W are not identified on the proposed revised Map 2.05.3(3)-1 submitted with the TR -70 application. Based on the contour of the land it may be the case that ditches C-10 and D1W may not be required; however, a discussion as to the prevention of disturbed area run-off from the west side of the permit to Pond 013 was not included. Please provided a revised Map 2.05.3(3)-1 to include these ditches or provide a revised Attachment 2.05.3(3)-1 providing a justification and noting that these ditches are no longer required. 1313 Sherman Street, Room 215, Denver, CO 80203 P 303.866.3567 F 303.832.8106 http://mining.state.co.us John W. Hickenlooper, Governor I Mike King, Executive Director I Virginia Brannon, Director