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Rlchera D. Lemm <br />Governor <br />DEPARTMENT OF NATURAL RESOURCES <br />DevirJ H. Gelchae, Eaeculive Director <br />MINED LAND RECLAMATION DI\ <br />DAVID C. SHELTO N, Director <br />DATE: March 3, 1986 <br />T0: Peter O'Connor <br />FROM: Anne Bal dri ge ~3' ~/ <br />RE: BLUE FLAME - ADEQUACY REVIEW REGARDING SURFACE DRAINAGE <br />I have completed IRy review of the proposed drainage control system for this <br />mine. Following are rtty comments. <br />1. The design for the propoed pond is adequate, however, the pond is <br />circular and would be difficult to build. I suggest building a square pond <br />with the same depth and side slopes. The surface dimensions should be 50' x <br />50' with inside bottom dimensions of 46' x 46'. <br />2. The pond design does not include a principal or emergency spillway. A <br />principal spillway is not necessary for this small pond as long as the <br />operator commits to pumping the pond to maintain enough storage for the 10 <br />year - 24 hour storm. <br />The pond should have an emergency spillway. This spillway must be designed tc <br />pass the peak flows from the 25 year - 24 hour storm event. Using the j <br />criteria established for the 10 year - 24 hour storm the design is as follli ws. <br />L = 320 ft. <br />Z=100 ft. <br />5=31% <br />A = 1.9 acres <br />Rainfall = 2.5" <br />CN=81 <br />Runoff = 0.94" <br />No shape adjustment <br />Slope Adjustment = 1.09 <br />Q 25 years = (1.09)(4 <br />Spillway Design: <br />83 CFS/in)(0.94") = 4.95 CFS <br />h <br />I~ ~ ~ 1 <br />r <br />z <br />423 Centennial Building, 1313 Sherman Street <br />determine L using <br />broad-crested weir: <br />Q = CLH 3/2 <br />Denver, Colorado 80203 Tel. (303) 866.3567 <br /> <br />