Laserfiche WebLink
Section A and B of the access road collection ditch are designed to pass peak <br />flows from a 10-year, 24hour storm event. Section A is a trapezoidal channel <br />with 4.0 foot bottom width and 2H:1 V sideslopes. Section B is a V-ditch with <br />2H:1 V sideslopes. Both ditch sections are cut into the lower soil horizon which <br />contains significant amounts of gravel and cobble-sized rocks. These materials, <br />combined with limited flow velocities should provide adequate protection to <br />prevent channel erosion and scour. Detailed design information for the access <br />road ditch is included in Exhibit 19, Drainage and Sediment Control Plan. <br />Following approval of the permit revision, EFCI will proceed with field modifications <br />on Segment A of the access road collection ditch. Modifications will be completed <br />within 60 days following approval. <br />A 21-inch CMP culvert has been installed where the haul road turns toward the <br />coal refuse stockpile area, as shown on the Drainage and Sediment Control Map, <br />(Map 20). The culvert has been designed to pass peak flows from a 10-year, 24- <br />hour storm event. Culvert calculations are included in Exhibit 19, Drainage and <br />Sediment Control Plan. Due to EFCI's anticipated equipment loads, the culvert is <br />• designed with a minimum cover of one foot of compacted fill. Both cover material <br />and culvert specifications reflect consideration of equipment and cover loads to <br />prevent culvert collapse. In order to insure continued effectiveness and prevent <br />potential erosion, any trash or debris which may accumulate in either ditches or <br />culvert inlets will be removed in conjunction with regular haul road maintenance. <br />Surfacing <br />The refuse pile haul road is surfaced with approximately 4 - 6 inches on minus 3/4- <br />inch gravel to provide a smooth, durable operating surface, minimize required <br />maintenance, and prevent rutting and erosion. Gravel surfacing materials were <br />obtained on-site and consist of decomposed granodioritic materials. Surfacing <br />materials were selected for their durability and strength under load and do not <br />contain any know acid or toxic forming components. <br /> <br />c:~seovn-zz <br />~oiuiss i::a~,m tR 4.03-5 Revised -October 1995 <br />