2010-03-31_REVISION - M2001069 (4)

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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 COLORADO D I V I S I ON OF RECLAMATION MINING SAFETY APR 05 2010 Bill Ritter, Jr. March 31, 2010 Governor Division of fiswctam"on, Kning rid Safety Harris D. Sherman Tiffany Hawkins Executive Director Asphalt Constructors, Inc. Ronald W. Cattany 7040 West US Highway 160 Division Director Alamosa, CO 81101 Natural Resource Trustee Re: Del Norte West Valley Pit, Amendment AM-1, Permit M-2001-069, Second Adequacy Review Letter Dear Ms. Hawkins, Thank you for the packet of adequacy response materials, which were received here on March 31, 2010. Review of those responses indicates that the cover letter answered most of the questions and the exhibits are generally adequate; however there are a few points that still require clarification before the application may be considered for approval. Please provide responses to each item in the paragraphs below, and identify each by the exhibit to which it pertains. Portions of the application and its exhibits that are considered adequate at this time do not appear in this letter. Exhibit C - Pre-mining and Mining Plan Maps (Rule 6 4 3) Thank you for preparing the series of mining maps, reflecting the phased progression of mining through the site. The topsoil stockpile location within each active phase is noted along the exterior perimeter, as well as the direction of mining. I would like to make one additional comment concerning the new maps, to which you need not respond or provide further revised maps: immediately inside the permit boundary line in each active phase is the (proposed) access road, and immediately toward the inside of the road is the topsoil stockpile. It is presumed by this office (because it is not shown) that the edge of the pit will be located a short distance (or immediately) inside the topsoil stockpile. Please be reminded that the top edge of the pit must not encroach too close to the topsoil stockpile or to the permit boundary. It is important that sufficient setback distance be left, unmined, outside the pit to allow room for equipment maneuvering during highwall slope reduction and for respreading topsoil. All pit activities must be contained inside the permit boundaries. Exhibit D - Mining Plan (Rule 6.4.4) There is still some ambiguity in the detail of what gradient the pit slopes will be maintained at during mining. Recall our inspection observation of the vertical highwall on the north side of Phase III. Your cover letter stated that this was left vertical since it was temporary and mining would continue north into the next phase. Statements within this exhibit reflect that 3:1 slopes will either be created during mining, or be created during reclamation. Either way is fine, but it needs to be clarified which, since it affects the reclamation bond. If the plan commits to 3:1 slopes during mining, it will be a permit condition and the bond will be calculated thus, and you must ensure that they do not exceed that gradient. If mining highwalls will be vertical, that should be stated (for example, a commitment to have no more than 600 linear feet of vertical highwall at any time, with all others sloped at 3:1). Please clarify. Office of Office of Mined Land Reclamation Denver • Grand Junction • Durango Active and Inactive Mines