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J <br />V <br />• <br />CLINTDN W MENgING. Pq E$ID ENT <br />E R rnID Hf LL. EXEC VIDE PRESIDENT <br />H. F. BISHOP. VICE Pq E$IDENT <br />A. J. DEU TSCH.Tq EA$UPER <br />J. H.TU PNfR, aECgETA RT <br />TIPTON AND KALMEBACH, INC. <br />O+[ PAwe CCNTReL.SUirE ~e0~ <br />15y ewewA"OE $Tw CET <br />DENV ER,COLORADO 80202 <br />PHOrvE f]p]1 5T2-ap61 <br />September 27, 1982 <br />Mr. Rich Atkinson <br />Colowyo Coal Company <br />5731 State Highway 13 <br />Meeker, Colorado 81641 <br />Subject: Colowyo Mine Permit Aprlication <br />• <br />Dear Mr. Atkinson: <br />cAa Le: <br />•gTIP - DENVER <br />TWX: <br />910 B]1'25ep <br />The additional description for the rock protection for the mining area ditches for <br />the Colowyo mine permit application as discussed with you and the Colorado Mined Lond <br />Reclamotion Division is as follows: <br />Mining Area Ditches -- Rock Protection <br />Rock protection of the ditch cross section has been used for the <br />constructed Streeter Gulch ditch and is included in the design section for <br />the Gulch A ditch. The rock protection will be composed of a well <br />graded mixture consisting of rocks having length, width and thickness <br />dimensions as nearly equal as practical, and with most of the rocks of <br />size given by the Formula: v = 2.57 Yd or larger (from p, 208 of USBR <br />Engineering Monograph No. 25 Hydraulic Design of Stilling Basin and <br />Energy Dissipators) where: <br />v =average channel velocity in feet per second <br />d =diameter of rock in inches (specific gravity 2.65) <br />With this formula, required rock diameters for various stream <br />velocities are: <br />Stream Velocity <br />(ft~sec) <br />Rock Diameter <br />(inches) <br />• 6 6 <br />8 10 <br />10 16 <br />12 22 <br />/ `~ <br />