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N ~,, ,, ~,°. DEPARTMENT OF NATURAL RESOURCES <br />* f ii, } ' Dwla H. p~teM4 Ea~cuUv~ Olhtlor ~~ <br />• *, .' •;,~` MINED LAND RECLAMATION DIVISION • <br />~ DAVID C. BHfIISON, Dlnator <br />i <br />plph Ora 0. Lamm <br />ponmor <br />DATE: March 3, 1986 <br />T0: Peter O'Connor , <br />~~ i <br />FROM: ;Anne Baldrige ~ ~j <br />'~ ~~ <br />RE: BLUE FLAME - ADEQUACY REVIEW REGARDING SURFACE DRAINAGE ~ <br />I have completed my review of the proposed drainage control system for this <br />mine. Following are my comments. <br />1. The design for the propoed pond is adequate, however, the pond is i <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 De 50' x <br />50' with inside bottom dimensions of 46' x 46'. <br />2. The pond design does not include a principal or emergency spillwa ~ A <br />• principal spillway is not necessary for this small pond as long as tfie <br />operator commits to pumping the pond to maintain enough storage for thg 10 <br />year - 24 hour storm., <br />The pond should have an emergency spillway. This spillway must be designed to <br />pess 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 asfollaws, <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)(4,83 CFS/in)(0 <br />Spillway Design: <br />~ 1~ ,n ~ , <br />?: - L' _~ <br />423 Centennial Building, 7313 Sherman Street <br />94") = 4.95 CFS <br />determine L using <br />broad-crested weir: <br />Q = CLN 3/2 <br />Denver, Colorado 80203 Tel. (303)i666-3567 . ; <br />