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C J <br />plcn~r0 D. Lamm <br />Qovanor <br />1.,I. <br />;'DEPARTMENT OF NATURAL RESOURCES <br />! Dwla M. OsIGneL Ex~cully~ Dlnaror <br />MINED LAND RECLAMATION D11 <br />DAVID C. BHELTO N, Dlr~etor <br />DATE: March 3, 1986 <br />T0: Peter O'Connor ~~ <br />FROM: ;Anne Bal dri ge A't3S' ~j <br />~, <br />RE: BLUE FLAME -ADEQUACY REVIEN REGARDING SURFACE DRAINAGE <br />I have completed my review of the proposed drainage control system for this <br />mine. Following are my comments. <br />I <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 end side slopes. The surface dimensions should be 50' x <br />50' with Tnside 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 far this small pond as Tong 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 <br />criteria established for the 10 year - 24 hour storm the design is as follows. <br />/ L 320 ft. <br />/Z=100 ft. <br />iS=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)(4.83 CFS/in)(0 <br />Spillway Design: <br />r~ <br />I~ ~ Z <br />• 1 <br />-L_•-~ <br />94") = 4.95 CFS <br />determine L using <br />broad-crested weir: <br />Q = CLH 3/2 <br />~~) <br />,., <br />~! <br />423 Centennial Building, t313 Sherman Street Denver, Colorado 80203 Tel. (303) 866-3567 <br />