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DSS: <br />The DSS channel will accommodate the largest potential runoff flows from the lazgest <br />subbasin and two adjacent subbasins. The channel is straight and relatively steep, but <br />construction space is adequate. The estimated geometry of channel DSS is a 3-ft base, a <br />1 ft depth, and 3H:1 V side slopes. Because of the potential for large flow velocities, the <br />^~ channel is expected to be lined with imported riprap material of an appropriate size (see <br />Section 4.0). However, this channel is located on U.S. BLM property and design of the <br />channel may vary in accordance with the BLM's requirements. <br />' D56: <br />The DS6 channel will be constructed along the small segment of the main mine access <br />road, just south of the Research Mine Bench. The channel is expected to have a <br />triangular-shaped or relatively narrow (small-based) trapezoidal shape. The estimated <br />geometry of channel DS6 is a 1-ft base, a 1 ft depth, and side slopes of 2H:1 V. <br />DS7r and DS7b: <br />The DS7 channel will have two designs that pertain to the Lower Bench access road <br />portion of the channel (DS7r) and the Lower Bench portion of the channel (DS7b). On <br />the Lower Bench access road the channel will be constructed on the inside of the road at <br />the toe of the adjoining slope. The channel is expected to consist of a narrow trapezoid <br />approaching a triangular shape. The estimated geometry of channel DS7r is a 1-ft base, a <br />1 ft depth, and side slopes of 2H:1 V. If necessazy, a similar approach to DS4 will be <br />followed and construction will make use of the road grade itself as part of the channel. <br />Although the calculations indicate a potential high velocity in this channel, bedrock is <br />exposed in places along this alignment and is expected to be shallow in other areas. <br />Exposed bedrock should reduce potential erosion associated with high flow velocities. <br />Where possible, vegetation will be established in the channel to increase channel <br />stabilization. <br />Channel DS7b will require a larger profile area to accommodate runoff from upper <br />discharge points DP1 and DP2. The channel will be constructed within the bench <br />materials of sand to cobble-size shale fragments along the east side of the bench neaz the <br />toe of the highwall and Upper Dump. The channel will be seeded to establish native <br />vegetation. The estimated geometry of channel DS7b is a 5-ft base, a 1 ft depth, and side <br />slopes of 8H:1 V and 3H:1 V. <br />DS8: <br />The DS8 channel will be constructed near the middle of the Lower Bench. This swale or <br />broad shallow channel will control runoff from the east half of the mine bench. The <br />channel will be oversized to accommodate additional runoff in the case that channel <br />DS7b tops its banks. The estimated geometry of channel DS8 is a 1-ft base, a 0.5 ft <br />depth, and side slopes of 3H:1 V. The channel will be constructed within the bench <br />materials of silt to cobble-size shale fragments and will be seeded to establish native <br />vegetation. <br />Western Water & Land Inc. 13 <br />