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CTL /Thompson also performed a stability analysis of the Lorencito Canyon Mine waste to <br />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 IOft 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 removes coarse and fine impurities from the coal. <br />Fine refuse is collected in the thickener, dewatered by a belt press, and sent by conveyor to <br />the refuse disposal area. Handling of these fines has caused problems for the operating <br />efficiency of the Prep Plant and refuse disposal area. To the extent practicable, the <br />Applicant will dispose of these fines by pumping a refuse /water slurry into abandoned <br />portions of the Allen Seam and recovering clear water by a pump located north of the <br />preparation plant. <br />MR -95 2.05 -44 Revised 08/24/11 <br />