2013-07-16_REVISION - C1982056 - Laserfiche WebLink

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��1111 Peabodq Twentymile Coal, LLC �" 29515 Routt County Road 27 Oak Creek, C RECEIVED �+ `IVED 970.879.38000 80467 Mr. Jason Musick, Environmental Protection Specialist JUL 16 2013 July 11, 2013 Division of Reclamation, Mining, and Safety 1313 Sherman Street, Room 215 DIVISION OF RECLAMATION Denver, Colorado 80203 MINING AND SAFETY (303) 866 -3567 X 8134 RE: Twentymile Coal, LLC - Foidel Creek Mine (Permit No. C -82 -056), Technical Revision (TR12 -81) — CRDA Ditch Modification Technical Adequacy Responses Dear Mr. Musick: We received your Technical Adequacy comments on the above - referenced revision, and proceeded with review and updating of the two referenced maps (Map 24 and Drawing C -102), in order to respond to the comments. In the course of our review, further questions arose relative to both effective drainage controls for the CRDA Expansion, and the relationship between the interim drainage controls and the progressive advance of refuse placement. Additional survey data was obtained, and the planned modifications to Interim Ditch RDA -4a were modified to best balance effective drainage control with the ongoing CRDA expansion activities. We also determined that it would make more sense to route the drainage from Ditch RDA -4a under the CRDA Access Road and drop it through an existing rocky drainage channel into the Area 1 Pit, rather than run it all the way down the hill in a ditch paralleling the road. Given changes in ditch location and gradient, the SedCAD runs include riprap designs based on maximum slopes for each segment (refer to Drawing 2d). Given these considerations, in addition to the updates to Map 24 and a series of drawings which replace Drawing C -102. included with this response package are revised permit text, maps, and the revised SedCAD runs. Consistent with the original TR12 -81 application: In order to construct the realigned portion of Ditch RDA -4a and prevent loss or contamination of the soil material resource, TC will recover soil and suitable material from the area between the existing and realigned portion of the Ditch and the area where the realigned Ditch will be constructed (maximum distance is now approximately 400 feet). The recovered materials will be transported and placed in the existing nearby soil and suitable material stockpiles. Given that these materials were already scheduled to be recovered from the CRDA Expansion footprint, designed stockpile quantities will not change. In order to assure effective drainage flows, the material excavated to construct the realigned portion of the Ditch will be replaced in the corresponding segment of the existing ditch and regraded. Since the proposed Ditch modification will not involve any disturbance beyond that already approved for the CRDA Expansion JR09- 67), this revision should have no impact on the bond reclamation liability. We would like to proceed with this project as soon as possible, to take advantage of favorable conditions during the remainder of the 2013 construction season. We, therefore, appreciate your consideration, cooperation, and assistance in facilitating timely review and approval of this revision application. After you have opportunity to review the accompanying information, please feel free to contact me with any questions or to discuss submittal materials or related matters. Best regards. Twentym i lv erT ry rettle n Manager Fjrv' onmen al Affairs