Laserfiche WebLink
The minimum width will be the width of the natural downstream channel. The riprap will be sized in <br />• the field by SCC's project engineer based on the "as-built" slope of the culvert and final configuration <br />of the exit channel slope area. The sizing shall be based on the Federal Highway Administration's HEC <br />No. 11 "Use of Riprap for Bank Protection" or other standard methods. Alt culverts will have a <br />minimum cover of 12 inches. Culverts and drainage ditches will be maintained periodically to prevent <br />accumulation of debris on the culverts inlets and outlets. The general design procedures used in the <br />design of culverts is contained in Attachment 13-1 <br />Tables 13-5 and 13-6 contain an inventory of existing and proposed culverts at the Seneca II-W Mine. <br />All existing culverts are adequate. Figure 13-3 and Figure 13-4 show typical installation of culverts, <br />Other applicable methods include the use of charts developed by the Federal Highway Administration, <br />published in Hydrologic Engineering Circular HEC-5 IFHA, 19801, and Hydrologic Design Series HDS-3 <br />(FNA, 1980). <br />Charts published in HEC-10 IFHA, 1978) are also used; however, exit velocities must then be <br />determined by other methods. Headwater conditions are typically examined by using HEC-5 inlet <br />control Homographs. To be conservative and to allow for adequate freeboard, SCC usually uses <br />"projecting" conditions. <br />As virtually all culverts have free outfalls, inlet control assumptions can be verified by the "Pipe Plow <br />• Charts" in HDS-3. If flow in the culvert has a free surface, entrance control exists, and exit velocity <br />can be approximated by using the greater of normal or critical velocity determined by the "Pipe Flow <br />Charts" in HDS-3. <br />Monitoring. A section of the Haul Road G alignment traverses the sideslope of a hill. Although the <br />stability analyses indicate that the road cut will be stable, as an added safety measure, SCC will <br />monitor the slope above and below the road alignment. Rebar will be driven into the ground at <br />locations indicated on Drawing No. 9111-5, Attachment 13-36 (Ivey Reportl. These monuments will <br />initially be surveyed after installation prior to road construction. End-of-construction conditions are the <br />most critical periods for cuts in clays. Therefore, the monuments will be surveyed for movement <br />immediately after the cuts have been completed. They will be surveyed monthly for the first quarter <br />and quarterly on the same schedule as Pond 005. If no movement is detected after one year, <br />monitoring will be suspended, upon approval by the Division. <br /> <br />27 Revised 01/06/94 <br />