2007-06-19_REVISION - M1986015 - Laserfiche WebLink

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Southwestern Ecological Services 37 East Colorado Avenue Denver, Colorado 80210-3105 (303) 722-9067 Fax June 19, 2007 RECEIVED Berhan Keffelew ~UN ~ 9 2~~~ Division of Reclamation, Mining and Safety Room 215 Oivislon of Reclamation, 1313 Sherman Street ~(' Mining and Safety Denver, CO 80203 ItE: Responses to May 5, 2007 adequacy~er. Pueblo East Pit Amendment 3. M-1986-015 Dear Berhan: (toll free) Thank you for your adequacy review of the amendment to this operation. We have reviewed your comments and concerns and provide the following information to address the items stated in your letter. 1. In your opening paragraph you state that the increase in affected land is approximately 70 acres. Actually it is closer to 90 acres. 2. Item II A (Refers to Groundwater Barrier Wall on Page 25 of Exhibit D) - There is a concern expressed regarding the sheet piling option for sealing the pit. This was included in the plan fox one purpose only. That was to indicate that there is a possible option to using a slurry wall that might be feasible, provided the cost can be reduced to an amount that is lower than a slurry wall. At this point in time, the cost of the materials exceeds the cost of a slurry wall. Therefore, this option is not a proposal to use that and there was no intention that the inclusion of this option in the amendment, when approved, would result in an approval of using this option. Clearly, the reclamation costs are based solely on a slurry wall being installed. In the event that the costs for a steel wall declined to the point where it was economically feasible AND approval would be obtained from the various agencies then and only then would that be included in the plan through a permit change. Perhaps the wording on Page 25 of the Mining Plan needs to be altered to indicate more strongly that the preference is for the slurry wall. But hopefully this explanation will suffice. 3. Item II B - Because the type of streambank strengthening proposed would requite placing material into the river (below the normal high water Gne~, approval from the Corps of Engineers will be required. Whether this would be covered by a Nationwide Permit or an Individual Permit under Section 404 of the Clean Water Act depends largely on the amount of work required. But doing this work without approval would clearly be a violation of the Clean Water Act. Approval will be sought prior to doing the work. 4. Item II C - This overflow berm will actually be rather low. It will be similar to the overflow berms used in Phase 1 which did not require approval. The purpose of the berm is to provide a barrier to more or less normal overflow of the river. Based upon the height of the water during the 2006 floods, this berm should be about five feet above the natural ground elevation. In some places it might be as much as six feet, but generally it would be about four to five feet high. In Phase 1 these berms provided a perimeter road around the pit, but were never intended and were not constructed to the strength standards of a flood control levee. Furthermore the course of the river adjacent to this area is quite straight, although there is the single small "bump" referred to as a "mini- meander" in the plan. Flood waters in this area would exhibit a lazge scale flow of a primazily laminar type. During the 2006 flood, no erosion occuxxed anywhere within the Phase 2 setback and only minimal erosion occuxxed along the river bank in this area. That indicates that the flood flows through this area exhibit limited ~~~~ ~