1985-05-29_REVISION - C1981012 - Laserfiche WebLink

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.~ , Ms. Candace Thompson Colorado Mined land Reclamation Division 1313 Sherman Street Denver, Colorado 80203 wyom~~ F~ co~Mr • 12055 W. Second Place • P.O.Box16696 • Lakewood. Colorado 80215 • Telephone (303)989-5037 May 29, 1985 iii iiiiiiiiiiiu iii 999 ,~ .. .::~ Re: Technical Revisions -New Elk Mine Permit C-012-81, Thickener and Plant Discharge Plan. Dear Ms. Thompson: As promised in my letter to you dated April l2, 1985, Wyoming Fuel Company (WFC) is hereby submitting our request for a technical revision to Permit No. C-012-81 to provide for plant and thickener discharge into Pond 006. The proposed plan utilizes Pond 007 to contain all surface runoff from drainages originally routed to Pond 006 (except • small area immediately east of the preparation plant) as well as from drainages originally routed to Pond 007. Pond 006 will then accomodate only plant and thickener discharges and runoff from areas immediately adjacent to the pond. The attached calculations confirm that Pond 007 (as-built) has sufficient capacity to contain 1'0-year, 24-hour storm event runoff from Pond 006 and Pond 007 drainage areas, a total of 6.6 acre-ft. In addition, the Universal Soil Loss Equation is used to estimate sediment yield from these areas at .3 acre-ft/year (.9 acre-ft for 3 years) at a conservative 1.0 sediment delivery ratio. The total required capacity for Pond 007 is therefore 7.5 acre-ft. As shown by the attached stage volume curve for Pond 007, 9.2 acre-ft of storage is available in Pond 007, allowing a surplus of l.7 acre-ft. The attached calculations also confirm that the emergency spillway is adequate for passing peak 1.9= , ~ `'~ year, 24 hour flows from both drainage areas while maintaining l-ft freeboard. Additional discharges into Pond 007 will include washdown from the breaker building and silos, sump discharge from the clean coal reclaim tunnel, discharge from a dewatering well near the clean coal reclaim tunnel, and possibly effluent from a new sewage treatment plant planned for construction in late 1985. With the exception of the sewage treatment plant effluent, these additional discharges will be infrequent, of short duration and of relatively small magnitude. The surplus capacity in Pond 007 should be more than adequate to handle the additional water volumes and sediment loads generated by these sources.