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Section 816.71 (f) Continued. • lifts not to exceed 4 feet. The lifts which will be compac to approximately 90% of AASHTO T-99 density with the trucks and dozers to prevent the formation of excessive voids and to ensure stability. The tops of the fill will be graded no steeper than 5% to allow for proper drainage. The fills will be constructed to meet a minimum long term safety factor of 1.5 as indicated in the designs described in Exhibit 9, Excess Spoil. Detailed specifica- tions for construction of the fills, including the required degree of and methods for compaction, as well as designs for surface and subsurface drainage are prescribed in Exhibit 9, Excess Spoil. (g) The final configuration of the fill must be suitable for postmining land uses approved in accordance with Section 816.133, except that no depressions or impoundments shall be allowed on the completed fill. The completed fills will be compatible with the postmiaing land use • proposed in Section 816.133. These fills will contain no depressions oz impoundments but they will be graded to control drainage. Both fills will blend in with the existing topography and will be re- vegetated according to Sections 816.111-816.117. The average slope will be approximately 3:1 (horizontal to vertical) with benches every 50 vertical feet. This configuration will be compatible with future grazing of the area. (h) Terraces may be utilized to control erosion and enhance stability if approved by the regulatory authority and consistent with Section 816.102(b). The use of terraces in the design of the fills is described in Exhibit 9, Excess Spoil. Generally, benches will be constructed every 50 vertical feet. Considering the height of the fill, it will be necessary to decrease drainage velocities sufficiently to control erosion during revegetation on these benches. • 816-91