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CTL/Thompson also performed a stability analysis of the Lorencito Canyon Mine waste to <br />is be processed at the New Elk Mine and stored in the RDA. Results of this study are also <br />presented in Exhibit 30, Geotechnical Study — Coal Processing Waste Bank. <br />The Development Waste Pile west of the mine entrance been successfully reclaimed. A new <br />development waste disposal area (DWDA) is necessary to accommodate the waste rock <br />excavated during development and preparation of areas incident to underground mining. The <br />refuse material is expected to be identical to the material in the reclaimed waste disposal <br />area. Experience on site dictates that the makeup of these materials is not indicative of the <br />components of that would potentially lead to acidic runoff or adversely affect groundwater <br />quality. The mine has a long history of stockpiling coal without encountering spontaneous <br />combustion. <br />The development waste, ditch, and pond cleanings will be permanently stored in the new <br />DWDA located south of Highway 12. This area was previously permitted as the clean coal <br />stockpile area as shown on Map 11 Surface Facilities and Roads East Portal. The <br />storage capacity of the area is 72,100 BCY. Refer to Figure 13 for the plan and section view <br />of the proposed DWDA. The overall pile height will be 30 ft tall. Each loft bench will be <br />placed in up to 1 ft lifts and compacted with a track dozer. Setbacks of 20 ft for each bench <br />will result in an overall slope of 2.0(H):I(V) during construction. <br />Compaction testing was conducted by CTL/Thompson, Inc. of the New Elk Coal Waste <br />Development pile at approximately 3 month intervals in June, September, November of <br />1995 and March of 1996. The results are included in Exhibit 31 as documentation <br />supporting a permit revision. "Compaction Test Results New Elk Mine Development Waste <br />• Pile CTL/Thompson job No. 22905 ". CTL/Thompson observed pile conditions and <br />excavated four test pits. The results indicated that the waste dump was stable if compacted <br />to at least 90% of standard Proctor maximum dry density (ASTM D 698). A <br />CTL/Thompson evaluation at that same time of alternatives for the disposal of pond <br />dippings and ditch cleaning material indicated that the materials could be disposed of on the <br />development waste pile provided they are adequately drained and compacted. <br />(9) Return of Coal Processing Waste to Abandoned Workings <br />The New Elk Mine Preparation Plant receives mined coal from the Lorencito Canyon Mine. <br />As the coal is washed, refuse is deposited in the thickener, dewatered by the belt press, and <br />sent by conveyor to the Refuse Disposal Area. Handling of these fines has caused problems <br />for the operating efficiency of the Prep Plant. Basin is proposing to dispose of these fines by <br />pumping a refuse /water slurry into the abandoned New Elk Mine and recovering clear water <br />from gravity dewatering for returned use in the Prep Plant. <br />• <br />TR -53 <br />2.05 -44 <br />Revised 1/6/11 <br />