Laserfiche WebLink
• <br />Mountain Coal Company <br />West Elk Mine <br />Exhibit 69 <br />Slope Stability [mprovements <br />other surface irregularities. The excess material cut from the trench drains will be utilized <br />for regrading the slope. <br />This work will occur within previously disturbed areas; therefore, no topsoil salvage will <br />be necessary. The trench drain construction and slope regrading will be completed ftrst, <br />and depending on the effectiveness of this construction, the retaining wall, as discussed <br />below, may be necessary to "hold" the Landing #2 light-use road. <br />Retaining Wall <br />• <br />A retaining wall will be constructed, if necessary, along the outside edge of the Landing <br />#2 light-use road above the Sylvester Gulch Substation. The location of the wall is <br />shown on Figure 1. The retaining wall will be constructed of 27 steel piles anchored 10 <br />feet into bedrock. The steel piles will be placed on an 8-foot spacing with 8-inch by fl- <br />inch timber lagging spanning between the piles from bedrock elevation to the elevation of <br />the Landing #2 light-use road. The timber lagging will be exposed. Figure 2 shows the <br />construction details for the wall. The alternate section as shown on this figure will only <br />be utilized if during construction MCC encounters a deeper colluvium layer than was <br />indicated by drilling information. If a deeper colluvium layer is encountered, the <br />colluvium will be excavated below the 16-foot level and replaced with low strength <br />concrete, to improve the strength and stability of the mass behind the wall, and to ensure <br />that the wall will function as designed. <br />The retaining wall will also be constructed within previously disturbed areas; therefore, <br />no topsoil salvage will be necessary. Any excess soil material cut to prepare for the wall <br />will be included with the regrading work associated with the trench drain project <br />described above. <br />Final Reclamation <br />The trench drains will remain at final reclamation. At final reclamation MCC will install <br />a collector drain across the bases of the 24 trench drains to ensure that the trenches will <br />continue to drain to an open ditch and not through the backfill to be placed for <br />reclamation. The collector drain will be constructed to drain to the north and then to the <br />east of the substation and daylight into the road ditch along the Sylvester Gttlch road. <br />This road will remain upon final reclamation. The collector drain will be constructed <br />with the same specifications as the 24 trench drains, except that the collector drain will be <br />3 feet wide, 8 feet deep and approximately 500 feet long. The trenches will be backfilled <br />with approximately 335 CY of/a-inch washed rock and 110 CY of 12-inch riprap. <br />MCC will only remove the portion of the retaining wall that is above bedrock upon final <br />•_ reclamation. Approximate material quantities for this work, assuming that the alternate <br />piles will be required (i.e. assuming worst-case), includes: 761 linear feet (LF) of steel <br />2 Oct'.1998 MR25E <br />