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S• T CREEK MINING CD• P.O. Drawer "L" Fruita, Colorado 81521 (303)x58-1396 April 7, 1963 Mr. David C. Shelton, Director Colorado Mined Land Reclamation 923 Centennial Building 1313 Sherman Street Denver, Colorado 80203 Attn: Jim Herron RE: Munger Mine C-020-81 Creek Relocation and Reclamation Dear Mr. Shelton: ~~~ II~II~I~~II~~I~~ 999 uPa : s ~~~,~~~, Colo. Dept. of t•!ar.:r,:, r~asuurce~ Salt Creek Mining Company has completed an analysis of flow characteristics in the permanent relocation of Munger Creek channel passing the mine site as required by Stipulation No. 16 of Permit No. C-020-81. The analysis included review of calculations shown on Figure 2.3-3. These calculations have been modified to show a decrease in the Manning "n" from 0.055 to 0.042 as well as inclusion of a calculation of velocity. The decrease in Manning "n" is the result of a literature research which yielded the following graph by K. Strickler showing the effect of stone size upon Manning "n", shown in Appedix 1. Salt Creek intends to use 3.5 ft. diameter or larger stones as rip-rap in the diversion channel to provide adequate energy dis- sipation and preclude erosional velocity. Analysis of Figure 2.3-3 (revised) shows that the depth of flow to safely pass a 100 year 24 hour precipitation event will be 0.66 ft. The rip-rap will be larger than the depth of flow! The flow of water will then be directed around and through rip-rap creating numerous small channels whose flow characteristics can not be calculated until after reclamation. An alalysis of this trend to direct the water around and through rip-rap nearly 6 times the height of the calculated depth of flow would logically show that the Manning "n" of Figure 2.3-3 must be