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iiiiiiiiiiiiiiu m <br />999 <br />CLINTON W. MEHRING. PRESIDENT <br />E. R. MIGHELL. EXEC. VIDE PRESIDENT <br />H. F. BISHOP. V ICE PRESIDENT <br />A. J. DEUTSC H.TREASURER <br />J. H. TURNER. SECRETARY <br />TIPTON AND KALMBACH, INC. <br />ONE PARK CENt R4L.5 VITE ilGl <br />1519 4RAPAROE STREET <br />DENVER,COLORADO e0202 <br />PNONC 130]1 ST2-tlOBI <br />May 20, 1981 <br />Mr. Richard Atkinson <br />Colowyo Coal Company <br />5731 State Highway 13 <br />Meeker, Colorado 81641 <br />Dear Mr. Atkinson: <br />Subject: Colowyo Streeter Gulch Fill <br />Revisions due to Leander Fill <br />CABLE: <br />4RT:P - DENVER <br />Twx: <br />910-9]I~29~0 <br />As requested we have reviewed the effect of modifying the Streeter Gulch fill by <br />filling onto the property recently acquired from :~Ir. Leander, on the Streeter Gulch <br />ditch design and on the operation of the Streeter Gulch Sedimentation Pond. Our findings <br />on these items are as follows: <br />Streeter Gulch Ditch -- The changed mine fill configuration increases the <br />area to be rec aimed within the Streeter Gulch drainage area by 74 acres, <br />but the total drainage remains as previously computed as the additional area <br />to be covered with fill is within the Streeter Gulch drainage area boundary. <br />Detail of the composition of the Streeter Gulch drainage area far the previous <br />plans is as follows: <br />Streeter Gulch Drainage Area (acres) <br />Previous Pan Revised Pan <br />Drainage area <br />Pre-Mining 1424' 1424 <br />Post-Mining <br />Reclaimed 1049 1123 <br />Undisturbed 318 244 <br /> 1367 1367 <br />The hydrologic conditions for runoff remain essentially the same, with the <br />runoff curve number (CN) estimated to be 67 for both the reclaimed and <br />undistrubed areas, resulting in a computed design flow of 22 cfs for the 100- <br />year design storm for both the previous and revised plans. A portion of the <br />lomtion of the ditch changes, as the revised fill covers some of the present <br />lomtion of the ditch. With the location change certain changes result in <br />the ditch hydraulics which are covered in the enclosed computations. The <br /> <br />i <br />