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• The nominal road width was selected as 50 feet. A safety berm is <br />provided on the outside edge of the road. A drainage ditch will be <br />constructed on the inside edge. The 50 feet width, which includes <br />shoulders, is a nominal maximum value. The actual width will vary <br />depending on field conditions. The minimum road width will be about 35 <br />feet. Where natural slopes are steep, the road width will be reduced to <br />minimize the amount of disturbed area. We estimate that the average <br />road width after construction will be about 40 feet. <br />The haul road will be constructed using materials from both the <br />foundation excavation and from the pit. The adverse dip of the <br />sandstone foundation rocks north of Pit No. 4, require a benched haul <br />road foundation. After stripping of topsoil, the surface colluvial <br />materials will be removed to expose the sandstone. The sandstone will <br />be excavated to form a series of benches varying in width from about <br />15 to 20 feet. The bottom bench will be excavated below the leve] of <br />the existing slope to form a key trench. The top bench will form the <br />inside edge of the road as well as the drainage ditch. This arrange- <br />ment is shown on Figure 3. <br />The material placed above the benches will be compacted rock and <br />colluvium from adjacent road excavations. Since this material will <br />not be sufficient to complete the section, additional sandstone rock <br />will be hauled from the pit. Material from the pit will consist of <br />• interburden located between the 2nd and 4th coal seams. This is a <br />hard, fine-grained sandstone, which has been subject to less <br />weathering than the sandstone foundation rock. <br />The cross-sections shown on Figures 3 and 4 in the maps and exhi- <br />bits section have been selected so as to require more fill material <br />than is available from the foundation excavation for the road. This <br />has several advantages. The chosen section minimizes the amount of <br />exposed cut slope. Since these cut slopes can sometimes become <br />unstable, the section we have selected tends to increase the <br />stability. Importing a hard durable rock for the road fill will <br />improve the stability and internal drainage. <br />The overburden and interburden in the pit will bulk during <br />excavation. This bulking will exceed the volume of coal which will be <br />removed. By removing material from the pit, the volume of overburden <br />to be returned to the pit during reclamation will more closely balance <br />the volume of material removed during mining. This will allow the pit <br />to be reclaimed to its premining condition. <br />The road embankment slope was selected as 1.5 horizontal to 1 ver- <br />tical in order to minimize the area disturbed by construction of the <br />haul road. This slope was the subject of a geotechnical stability <br />analysis. <br />• The stability analysis uses a conservative set of assumptions to <br />model a "worst case" condition. The fill material was assumed to be <br />cohesionless, with a friction angle of 35°. The section used in the <br />analysis is shown on Figure 5. <br />8-81 III-8 <br />