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The following paragraphs describe outlet construction design for the discharge points at <br />the mine: <br />~ DP1 and DP2: <br />Discharge at points DP1 and DP2 will occur at the brow of the Upper Bench where shale <br />bedrock is exposed, forming acliff--face down to the Lower Bench. Discharge from DP1 <br />is expected to enter a sharp steep gully at the boundary of the Upper Dump and exposed <br />outcrop. Discharge from DP2 is expected to runoff the rock cliff-face and cascade down <br />' to the Lower Bench to the south of the former L-1 Portal. Runoff from both discharge <br />points is expected to migrate to channel DS7b. Because of the exposed bedrock at these <br />discharge points, no erosion mitigation will be constructed at the outlet locations. <br />DS5 and DP3: <br />DP3 discharges runoff from channels DS4, DSS, and DS6, a total potential flow of <br />approximately 81 cfs (sum of Qf) or 102 cfs (sum of Qd). The outlet will consist of a <br />straight extension of channel DSS into and along the axis of the natural ephemeral <br />drainage below the Reseazch Mine Dump. The DS5 channel slope in the mine access <br />' road area where DSS is joined by DS4 and DS6 is approximately 6.4% (S = 0.0643) and <br />has an estimated velocity of 5.2 ft/s. At discharge point DP3 this slope increases to <br />approximately 59% (S = 0.5952) in the direction of the dump face and natural channel. <br />The estimated runoff velocity in the DP3 channel on the dump face is 12.7 fUs, over <br />twice the estimated velocity in the upstream portion of the channel. <br />Currently, the U.S. BLM has asked that GSHI reclaim this azea by pulling back the <br />existing Research Mine Bench and sidecast material from the access road and <br />recontouring the area to better blend with the existing cut. The DSS channel will be <br />constructed within the existing fill in this azea so as to create a Swale that follows the axis <br />of the natural drainage. Riprap sizes for the upper (less steep) portion of channel DSS is <br />estimated to be 0.7 ft. Riprap sizes for the lower (steeper) portion of channel DP3 is <br />estimated to be 2.0 ft. Tables 5 and 5.1 show the riprap sizing calculations for DS5 and <br />DP3. <br />DP4: <br />DP4 is at the confluence of DS7b and DS8 on the Lower Bench. The estimated discharge <br />is approximately 117 cfs with a flow velocity of approximately 6.5 fUs in DS7b upstream <br />of the outlet. The channel slope in DS7b upstream of the dischazge point is <br />approximately 2.2 % (S = 0.022) and approximately 28 % (S = 0.28) on the outlet slope <br />on the north face of the Lower Bench (dump). The velocity on the outlet slope is <br />estimated to be 16.8 ft/s. <br />A riprap apron will be constructed at the confluence of DS7b and DS8 at least 20 feet <br />upstream of the grade inflection point. Tables 5 and 5.1 show the riprap sizing <br />calculations for DP4. The estimated riprap size for channel DS4 is estimated to be 1.8 fr. <br />Western Water 8 Land Inc. 15 <br />