Laserfiche WebLink
Exh. 7-23I-3 Revision Date: 4/28/22 <br />Revision No.: TR-154 <br />Stockpile Pond. The location of these temporary channel is shown on Map 41B and Figure 7-23I- <br />4. The ditches will be constructed concurrent with reclamation activities in the applicable <br />watershed, and they be retained until Phase II bond is granted for the entire watershed reporting to <br />both ditches. The ditches will be configured as follows: <br />D-5 Ditch <br />Station <br />Peak <br />Flow <br />(cfs) <br />Average <br />Slope (%) <br />Channel <br />Type <br />Side <br />Slopes <br />Erosion <br />Protection <br />Total <br />Depth <br />Station 0+00 <br />to 21+41 50.74 2.0 Trapezoidal <br />5’ bottom 2H:1V None 3’ <br />D-7 Ditch <br />Station <br />Peak <br />Flow <br />(cfs) <br />Average <br />Slope (%) <br />Channel <br />Type <br />Side <br />Slopes <br />Erosion <br />Protection <br />Total <br />Depth <br />Station 0+00 <br />to 21+41 18.51 6 Trapezoidal <br />5’ bottom 2H:1V None 3’ <br />Permanent Post Mine Channels <br />The Section 25 Pond watershed is comprised of seven post-mining channels which are Little <br />Collom Gulch, Sage Draw, Grouse Draw, Sharpie Draw, Lower, Middle, and Upper Bobcat <br />Draws respectively. The locations of these post mine channels are presented on Map 41B and <br />Figure 7-23I-5, and the channel profiles are presented on Map 33C. <br />Little Collom Gulch <br />The area contributory to Little Collom Gulch is greater than one square mile, and the lower portion <br />of the channel passes over a permanent valley fill; therefore, the modeled storm event required by <br />rule is the 100-year 24-hour event. The entire length of Little Collom Gulch will be riprap lined. <br />Four stock ponds LCG-1, LGC-2, LCG-3, and LCG-4 will be constructed inline in the channel to <br />reduce peak flows from larger storm events and provide a water source to support the post mine <br />land use. <br />A SEDCADTM model (100 Year 24 Hour Channel Demonstration) has been included which <br />evaluates the peak flow for each of the channel. The minimum channel configurations for Little <br />Collom Gulch are summarized below. <br />Little Collom Gulch <br />Station <br />Peak <br />Flow <br />(CFS) <br />Average <br />Slope (%) <br />Channel <br />Type <br />Side <br />Slopes <br />Minimum <br />Depth <br />(Feet) <br />Erosion <br />Protection <br />Station 0+00 <br />to 10+00 <br />(LCG-1) <br />31.06 16.6 Trapezoidal <br />15’ bottom 3H:1V 4.0 Riprap, <br />D50 = 6”