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• 3.0 DESIGN PARAMETERS <br />L J <br /> <br />Parameters for design were determined based on requirements set forth by OXBOW, and <br />requirements within the ~g~atione of the Colorado M1"fined Land Reclamation Bo°rd for o-I <br />Millipg, specifically Rule 4.10 and references therein. The following lists important aspects <br />of the proposed coal mine waste bank design at the Sanborn Creek Mine, and the parameters <br />that were used as constraints. <br />Type Coal mine waste bank <br />Capacity 15 to 20 years at 6,000 to 7,000 cubic yards per year <br />Slopes No steeper than 2 horizontal to 1 vertical (2:1) overall slopes <br />(Rule 4.10.4(4)), static safety factor of t.5 (Rule 4.10.412)) <br />Compaction 90 percent of the maximum dry density in accordance with <br />American Association of State Highway and Transportation <br />Officials (AASHTO) T99-74 (or ASTM D-698) in 24-inch <br />maximum thickness lifts (Rule 4.10.4(3)) <br />Haul Road 10 percent maximum overall grade (Rule 4.03.113)1, 30-foot <br />wide minimum width, safety berm, stormwater ditch <br />Diversion Ditches Flows from a 100-year, 24hour storm event (Rule 4.10.3(2)) <br />Underdrain System As required by Rule 4.10.311) <br />Sediment Pond Contain the 10-year, 24-hour storm and the associated <br />sediment, provide anon-clogging dewatering device, and an <br />emergency spillway system (Rule 4.05.8(3,4)1 <br />Overflow Spillway System A single overflow spillway able to transport flows from a 25- <br />year, 24-hour storm event (Rule 4.05.6(51) <br />Reclamation Stockpiling stripped topsail, overburden, and haul road cut <br />material in the area of the proposed coal mine waste bank, <br />covering re-contoured waste with a minimum of 4 feet of <br />cover and topsoil, then revegetating (Rule 4.10.4(5)) <br />95255l1424.RPT Coel Mine Weate Bank Design for the Sanborn Creek Mine <br />October 1998 WESTEC, Inc. <br />6 <br />