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C c~RUs <br />~ Yampa Valley <br />Tony Waldron <br />Ret~l.amation Specialist <br />Mind Land Reclamation Division <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />February 6, 1992 <br />Cyprus Yampa Valley Coal Corporation <br />29587 Routt County Road #27 <br />Oak Creek, Colorado 80467 <br />303-879-3800 <br /> <br />= EB 1 3 199? <br />Mir.sd Land <br />Dear Mr. Waldron; <br />Re: Substitution of Materials, Minor Revision 92-72 (Addition of <br />Sump D-4, Culvert D-7-A, and Ditch D-7): Permit C-82-056 <br />Per our discussion of 6 February, TCC is submitting the enclosed <br />page Ex 8-10(b) and the related Sedcad sizing for Culvert D-7-A. <br />These materials are to replace the previously submitted materials <br />relating to Culvert D-7-A, and reflect the use of a pair of 36 inch <br />diameter cmp culverts at location D-7-A rather than the previously <br />submitted pair of 36 inch smooth metal pipe culverts. Please note <br />that the total design flow to the culverts is 46 cfs, but a value <br />of 23.3 cfs per culvert was utilized in order to smooth the data <br />and provide ~? accurate minimum sizing. <br />As previously discussed, please note that the sizings for <br />Ditch D-7 and Cu~vert D-7-A include the peak flow from the Ditch D- <br />3 rerouting proposed in Technical Revision 92-13. This will allow <br />TCC to plan for the future re-routing of Ditch D-3 should the <br />technical revision be approved. <br />i~ <br />Should you have any questions or comments, please contact me at <br />your convenience. <br />S~ e~ME~9 1 `~ ~ <br />Marcus A. d eton <br />Environmental Specialist <br />