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Ditch No. 1 has been designed to provide a flow capacity equal to <br />• the capacity of the unmodified stream channel immediately upstream <br />of the structure. The portion of the channel downstream from Ditch <br />No. 1 was previously modified during construction of Highway 110. <br />Following mining activities, Ditch No. 1 will be revegetated in <br />accordance with the vegetation plan described in the Mining and <br />Reclamation Plan. Where possible, temporary revegetation will be <br />established during mining to minimize contributions of suspended <br />solids and to enhance overall stability of the structure. As shown <br />on the Post-Mining Topography Map (Map 14), Ditch No. 1 will be <br />established as a permanent diversion to route Coal Gulch surface <br />drainage through the area of the Coal Gulch Mine. The <br />configuration of the permanent drainage provides a stream gradient <br />and alignment which is geomorphically stable for the area. No <br />artificial structural controls will be utilized in the permanent <br />reconstruction channel. As a result, Ditch No. 1 will re-establish <br />• the drainage channel of Coal Gulch through the area previously <br />disturbed by mining operations. <br />4. The following comments apply to Ditch No. 2: <br />a. Comments 3 a and be above also cooly to Ditch No. 2. <br />Response: Similar design methods have been utilized far Ditch No. <br />2 as discussed in 3 a and 3 b of these responses. <br />b. Will the entire length of the channel be placed in bedrock, if <br />not, what measures will be utilized to stabilize the channel <br />and protect it from erosion. If the entire length is bedrock, <br />it appears that the roughness coefficient is incorrect. <br />Response: The entire length of Ditch No. 2 is placed in bedrock. <br />Increase of Manning's n from 0.025 to 0.035 to accommodate the <br />• bedrock channel does not change the channel design given the design <br />freeboard of 1.0 feet. <br />-$- <br />