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• Table 13-3 contains an inventory of culverts at the Nucla Mine. All existing culverts are adequate. Figure 13-4 and Figure 13-5 show typical installation of culverts. Other applicable methods include the use of charts developed by the Federal Highway Administration, published in Hydrologic Engineering Circular HEC-5 (FHA, 1980), and Hydrologic Design Series HDS-3 (FHA, 1980). Charts published in HEC-10 (FHA, 1978) were also used; however, exit velocities were then determined by other methods. Headwater conditions were typically examined by using HEC-5 inlet control Homographs. To be conservative and to allow for adequate freeboard, Peabody usually used 'projecting" conditions. As virtually all culverts have free outtalls, inlet control assumptions were verified by the °Pipe Flow Charts' in HDS-3. If flow in the culvert has a free surface, entrance control exists, and exit velocity was approximated by using the greater of normal or critical velocity determined by the 'Pipe Flow Charts" in HDS-3. Maint Han . -. Haul roads are inspected on a regular basis at the Nucla Mine. If, upon inspection, it is determined that repairs are needed, appropriate repairs such as, but not limited to, blading, filling of potholes, replacement of the road surfaces, revegetation of side slopes and watering for dust control, will be conducted as necessary. • Restoration. Unless WFC requests retention of haul roads for postmining land use and the Division approves such request, immediately after the road is no longer needed for operations, reclamation, or monitoring: a. The road will be closed to vehicular traffic; b. The natural-drainage patterns will be restored; c. All culverts will be removed; d. Roadbeds will be ripped, plowed and scarified; e. Fill slopes will be rounded or reduced and shaped to conform the site to adjacent terrain and to meet natural-drainage restoration standards; f. Cut slopes will be shaped to blend with the natural contours; • 13-13