2012-08-03_PERMIT FILE - C1981012A (3)

Home Browse Search

CTL /Thompson also performed a stability analysis of the Lorencito Canyon Mine waste to be processed at the New Elk Mine and stored in the RDA. Results of this study are also presented in Exhibit 30, Geotechnical Study — Coal Processing Waste Bank. The Development Waste Pile west of the mine entrance been successfully reclaimed. A new development waste disposal area (DWDA) is necessary to accommodate the waste rock excavated during development and preparation of areas incident to underground mining. The refuse material is expected to be identical to the material in the reclaimed waste disposal area. Experience on site dictates that the makeup of these materials is not indicative of the components of that would potentially lead to acidic runoff or adversely affect groundwater quality. The mine has a long history of stockpiling coal without encountering spontaneous combustion. The development waste, ditch, and pond cleanings will be permanently stored in the new DWDA located south of Highway 12. This area was previously permitted as the clean coal stockpile area as shown on Map 11 Surface Facilities and Roads East Portal. The storage capacity of the area is about 95,000 BCY. Refer to Figure 13 for the plan and section view of the proposed DWDA. The overall pile height will be 30 ft tall. Each 10 ft bench will be placed in up to 1 ft lifts and compacted with a track dozer. Setbacks of 20 ft for each bench will result in an overall slope of 2.0(H):1(V) during construction. Compaction testing was conducted by CTL /Thompson, Inc. of the New Elk Coal Waste Development pile at approximately 3 month intervals in June, September, November of 1995 and March of 1996. The results are included in Exhibit 31 as documentation supporting a permit revision. "Compaction Test Results New Elk Mine Development Waste Pile CTL/Thompson job No. 22905 ". CTL/Thompson observed pile conditions and excavated four test pits. The results indicated that the waste dump was stable if compacted to at least 90% of standard Proctor maximum dry density (ASTM D 698). A CTL/Thompson evaluation at that same time of alternatives for the disposal of pond dippings and ditch cleaning material indicated that the materials could be disposed of on the development waste pile provided they are adequately drained and compacted. DWDA #2 is at full capacity. NECC needs a temporary pile as a transition to DWDA #3. A temporary pile is located north and east of the stockpiles shown on Map -11, Sheet 3. Development waste will be stockpiled for at least 30 days, and until such time that final approval is received for Technical Revision No. 65 (DWDA #3). Material will be placed in two foot lifts and compacted as stated above in reference to DWDA #2. A new DWDA (DWDA #3) is planned for the area west of the west mine fan. The storage capacity of the west pile is about 155,000 CY. Refer to Map 12 for the plan and profile sections of the proposed West DWDA. The overall pile height will be a maximum of 90 feet. Material will be placed in up to 2 ft lifts and compacted to achieve at least 90% of standard Proctor maximum dry density (ASTM D 698). The pile will have 3H:1 V side slopes, and one 15' bench. The bench will slope back toward the pile at 2% and to the runoff collection ditches at 2 -5 %. Design recommendations for the West DWDA are included as Exhibit 43. The West DWDA will be constructed in accordance with the design recommendations. DWDA #3 is located over a historical mine structure referred to as a rail/rope slope. Prior to placement of waste at DWDA #3, the rail slope should be demolished in accordance with the recommendations included in Exhibit 43. (9) Return of Coal Processing Waste to Abandoned Workings The New Elk Mine Preparation Plant receives mined coal from the Lorencito Canyon Mine. As the coal is washed, refuse is deposited in the thickener, dewatered by the belt press, and sent by conveyor to the Refuse Disposal Area. Handling of these fines has caused problems for the operating efficiency of the Prep Plant. Basin is proposing to dispose of these fines by pumping a refuse /water slurry into the abandoned New Elk Mine and recovering clear water from gravity dewatering for returned use in the Prep Plant. TR -65 2.05 -44 Revised 07/25/12