2015-02-02_REVISION - M1992045 (3)

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Channels (Figure E-1a) • Channels Figure 4.2 and 4.3 ) Upper Cache Creek Basin Trapezoidal Channel -100 year- _ 24 hour storm — Channel Trapezoidal Slope =10% will be constructed with an four foot bottom -16 feet wide- 2.00 feet deep with 3(H):1(V) slopes will convey approximately 265 at a peak flow velocity of 13 fps. (Rip rap sizing (D -50) for the 10 year storm will range from 0.75 -1.0 feet) • Lower Upper Cache Creek Basin Trapezoidal Channel -100 gear -24 hour storm — Trapezoidal Channel Slope —3% will be constructed with an four foot bottom -21.5 feet wide- 2.25 feet deep with 3(H):1(V) slopes will convey approximately 220 cis. (See Table 5 -2) at a peak flow velocity of 7.9 fps. (Rip rap sizing (D -50) for the 10 year storm will range from 0.75 -1.0 feet) • diddle Cache Creek Basin Trapezoidal Channel -100 year -24 hour storm — Trapezoidal Channel Slope =10% will be constructed with an 6 foot bottom -19 feet wide- 2 feet deep with 3(H):1(V) slopes will convey approximately 330 cfs. (See Table 5.3) 14 fps. (Rip rap sizing (D -50) for the 10 year storm will range from 0.5. -0.75 feet). In Middle Cache Creek stream segment (Figure 4 -2) a diversion (Figure 44) is proposed to return the stream channel to approximate pre -mine alignment and at an estimated gradient of 12 %. • Lower Cache Creek Basin Trapezoidal Channel -100 year -24 hour storm — Trapezoidal Channel Slope =90/o will be constructed with an six foot bottom -18 feet wide- 2 feet deep with 3(H) :l(V) slopes will convey approximately 316 cfs. (See Table 54) 13 fps. (Rip rap sizing (D -50) for the 10 year storm will range from 0.75 -1.0 foot). Culverts 5 ear -24 hour storm • Eighteen inch culverts will be used, as necessary, within the project area. The culverts will be installed with a maximum gradient 0.03 feet per foot gradient which are capable of carrying 9.9 cfs -with a 5.6 fps flow velocity Table E -2.5 Upper Basin -Five year -24 hour storm will generate a peak flow of approximately 6 cfs. (SCS, 1975) (Table E2 -6), c. Channel Construction Channels will be constructed in areas identified on Figure F -2 using the design criteria summarized on Tables E2 -2 through E2 -5. Channels (including realignment- [diversion]) will be constructed using BMPs presented in Exhibit E- Attachment B and supplemental design sheets. 11.0 A. December 28, 2014 Colorado Division of Reclamation Mining and Safety Gold Basin Mine, inc. Gold Basin Mine Granite, Colorado