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• have a softy factor of 1.0, which means it would fail within a <br />short time and possibly result in a life-threating situation on <br />the County road below. In addition to these factors, there is <br />simply not enough usable dirt to completely backfill the <br />highwall. The approximate volume required is as shown below; <br />Cross-Section Area of Fill for Grade #2 = 15$ square feet. <br />Volume Needed = 15$ square feet x $50 feet (length of bench) <br />= 134300 cubic feet <br />= 4974 cubic yards <br />Plate P.-1 shows the locations of pits dug in the yard area to <br />determine the availability of usable fill. The Apex #2 Mine, <br />located at this site since the 1960's, re-worked much of the fill <br />with coal so that almost all of the dirt contains a considerable <br />amount of coal and cannot be used for backfilling. Each pit was <br />dug to a maximum depth of 5.0 feet. The results of the testing <br />and the areas of good fill are shown on Plate R-1. <br />The volume of good fill available for backfilling is shown <br />below; <br />Area 1 = 350' x 47' x 5' _ $2250 cubic feet = 3046 cubic yards <br />Area 2 = 200' x 40' x 2' = 16000 cubic feet = 592 cubicy_, <br />Total Available = 363$ cubic yards <br />In addition to the 4974 cubic yards needed to completely <br />backfill the bench, 2100 cubic yards are needed to backfill the <br />area above the mine office to approximate original contour. <br />Clearly, the amount of uncontaminated fill available is not <br />enough to completely backfill the bench. Also, at a slope of <br />1.OH:1.OV, it would be difficult to revegetate, and will not be <br />compatible with the post-mining land use. <br />If the entire highwall was to be reclaimed to a slope of <br />2H;1V, compaction could be achieved and the slope would be <br />stable. However, as is seen by Grade #3 on Cross-Section R-1, the <br />backfilIed slope would entirely cover Routt County Road 29. Also, <br />the amount of fill needed is many times more than that which is <br />available. <br />It is proposed that the the actual reclaimed slope be done <br />according to Grade #~. This is very similar to the plan which Has <br />e;<isted in the permit for at least 5 years except that the slope <br />is 2H;1V instead of 1H;1V. The 2H;1V slope is the best overall <br />slepe for reclaiming as much of the highwall as possible yet <br />providing good compaction, slope stability, good revegetation <br />potential and compa+.ibility with the post-mining land use of <br />gra~irg. From past experience with 2H:1V slopes in compacted <br />fil?, i?. is normal tc e:.<pect the s=ope safety factor to be 1.7 or <br />7.~. <br />L_J <br />1 C'~x~ 18~A <br />