2010-09-13_REVISION - C1981019 - Laserfiche WebLink

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STATE OF COLORADO DIVISION OF RECLAMATION, MINING AND SAFETY Department of Natural Resources 1313 Sherman St., Room 215 Denver, Colorado 80203 Phone: (303) 866-3567 FAX: (303) 832-8106 13 September 2010 COLORADO DIVISION OF RECLAMATION MINING SAFETY Bill Ritter, Jr. Governor Mr. Ryan Pawlowski Mike King Colowyo Coal Company, LP Executive Director 5731 State Highway 13 Loretta E. Pineda Meeker, CO 81641 Director Re: Colowyo Mine C-1981-019 Preliminary Review - Technical Revision 87, North Tributary, East Pit Ditch Dear Mr. Pawlowski: The Colorado Division of Reclamation, Mining and Safety (Division) has completed a preliminary review of the Colowyo Coal Company, LP's (Colowyo) proposed realignment of the North Tributary, East Pit Ditch. This preliminary review deals only with the proposed realignment of the North Tributary, East Pit Ditch, as shown on proposed Map 12. The Division will complete its preliminary adequacy review of the entire revision and send it under a separate cover; however, the Division is sending these comments in the interest of promptly resolving the North Tributary, East Pit Ditch issues. The Division is concerned about the proposed realignment of the lower portion of the North Tributary, East Pit Ditch. It appears that the actual post-mining topography between approximately stations 4+50 and 7+50 of the channel profile is higher than the approved post-mining topography (PMT), resulting in that portion of the ditch not being topographically controlled. (The attached portion of proposed Map 12 shows the actual contours, from the May 2010 flight, and the approved contours, based on Map 19.) The proposed Map 12 contours support what is seen in the field, a fairly gentle sloping area dropping off steeply to the edge of the drainage. The approved post-mining topography map (Map 19) shows a valley, albeit a shallow one, in this area. The elevation difference in this area is only around 10 feet. Given the variation between the actual PMT and the approved PMT for which the ditch plan was based, the Division can see why it is difficult to realign the ditch in the field. If the post-mining topography was graded as shown on Map 19, proper ditch alignment would be obvious on the ground. Additionally, a review of approved Maps 12, 19 and 41 raises questions about the labeled disturbed area. These maps show that the original approved North Tributary, East Pit Ditch alignment is within the current disturbed area. Colowyo has said and pointed out in the field that the approved alignment is `outside' the disturbed area. It is important for the maps to reflect the actual conditions so that the Division can accurately evaluate the areas for permitting purposes. Office of Office of Mined Land Reclamation Denver 9 Grand Junction • Durango Active and Inactive Mines