2009-03-02_PERMIT FILE - C1980004A (6)

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TABLE 3.1-1 MC'CLANE CANYON MINE RECLAIMED CREEK CHANNELS RIP RAP SITING CALCULATIONS • Stream Base Slope of Velocity Flow D10 D20 D50 D100 Segment Width Channel Quantity (DSOr~) (DZO2) (t.25•D5o) R-2 8 0.17 6.69 14.23 0.25 0.38 0.75 0.9 R - 5 12 0.12 7.34 34.80 0.17 0.25 0.50 0.6 R - 6 12 0.10 8.07 55.88 0.17 0.25 0.50 0.6 R - 8 12 0.08 8.43 69.39 0.25 0.38 0.75 0.9 R - 13 14 0.03 5.58 75.35 0.17 0.25 0.50 0.6 The rip rap sizes shown above are developed from " OSM's Surface Mining Water Diversion Design Manual" Figures 5.3 thru 5.7 utilizing the design procedures contained within the man ual. RIP RAP INSTALLATION & KEY CUTS Where the calculations have indicated that rip-rap will be required in a channel the entire lenght of the channel will be rip rapped. Key cuts will be used at the beginning and end of the area to be armored to ensure that the rip rap will not be undercut but the water flowing in the channel. The key cut will be twice as wide • and deep as the DM,vc• The key cut will also be excavated into the sides of the channel the same distance. FILTER DESIGN Design of the filter layer is dependent upon the soil characteristics of the channel base. The final design will be done after the channels as the channels are created. The size characteristics vary greatly within the project area. The upper areas near the mine site have sufficient coarse material in the soil to make a filter layer possibly unnecessary given the small size of the rip rap. The lower portions of the project area have soils that may have textures fine enough to require a filter layer. It is expected that The stream reaches R-2, R-5, R,6 and R-8 will not require a filter because of the coarseness of the base material. Stream Reach R-13 will likely need a filter layer since it will be in the alluvial silts near East Salt Creek. As the channels are being constructed, soil samples will be collected for analysis. The gradation of the sample will be analyzed. The results of analysis will be subjected the following Corps of Engineers and Bureau of Reclamation Filter Gradation Specifications. Dls (filter) /Des (base) < 5 5 <Dis (filter) / Dts (base) < 40 Dso (filter) /Dso (base) < 40 • If the analysis indicates that the use of a filter is required, a filter will be installed. The results of the analysis will be submitted to the DMG when available. The depth of the filter layer will be nine inches or DMnx of the filter material, which ever is largest. Mc Vol I Table 3.1-1 Page 2 11 - 98