2010-06-01_PERMIT FILE - C1982056A

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(9) Return of Coal Mine Waste to Abandoned Workings (a) Each plan shall describe the design, operation and maintenance of any proposed coal processing mine waste disposal facility, including flow diagrams and any other necessary drawings and maps, which must meet the standards of 2.10, for the approval of both the Division and the Mine Safety and Health Administration in accordance with 4.11.3. (b) Each plan shall describe the source and quality of waste to be stored, area to be backfilled, percent of the mine void to be filled, method of constructing underground retaining walls, influence of the backfilling operation on active underground mine operations, surface area to be supported by the backfill, and the anticipated occurrence of surface effects following backfilling. (c) The applicant shall describe the source of hydraulic transport medium, method of dewatering the placed backfill, retainment of water underground, treatment of water if released to surface streams, and the effect on the hydrologic regime. (d) The plan shall describe each permanent monitoring well to be located in the backfilled area, the stratum underlying the mined coal, and gradient from the backfilled area. (e) The requirements of 2.05.3 shall also apply to pneumatic backfilling operations, except • where the operations are exempted by the Division from requirements specifying hydrologic monitoring. TCC returns the thickener underflow generated at both Washplants I and II to the abandoned and sealed underground mine workings. When Washplant I initially began operations, the thickener underflow was partially dewatered using a filter- press, and this material was then combined with the coarse refuse and hauled to the Refuse Pile for placement. Due to handling and placement problems, TCC modified the fine refuse handling method, and began pumping the thickener underflow into the abandoned mine workings in the Eastern Mining District (EMD), as opposed to mixing it with the coarse refuse for placement on the Refuse Pile. With both Washplants I and II operating, the thickener underflow is typically a 15 to 25 percent solids, 300 to 550 gpm slurry mixture of rock and coal fines (28 mesh x 0). Exhibit 9C, Underflow Chemical Characterization, provides data on selected chemical constituents found in the thickener underflow. The water quality of the slurry is consistent with that of typical spoils water generated at the adjacent CYCC surface mine. The slurry mixture is piped to the sealed mine workings in the EMD, where the fines settle -out, and the decant water flows to a sump and is recycled back to the washplants. At the full coal fines refuse discharge rate, approximately 1.6MM ft of coal fines storage is required on an annual basis. The EMD has approximately 110MM ft of coal fines storage capacity remaining (approximately 70 -years capacity). In anticipation of possible future mining of the underlying Wolf Creek Coal Seam, TCC is shifting underground coal fines slurry placement to sealed mine workings in the Southern Mining District (SMD), which provide approximately 61MM ft of coal fines storage capacity (approximately 30- years capacity). Map 23 shows the EMD and SMD areas that have been or will be filled with fine refuse material. With the shift to the SMD, the water /solids mixture is piped from the washplants through two 6 -inch HDPE pipelines for approximately 1,800 feet to an 8 -inch cased mine borehole, located near the former CYCC Mine Office Building ( "Brown Palace ", see Map 24 for location of pipeline and borehole). The two Thickener Underflow Pipelines replace the previously used 6 -inch PVC line from Washplant I, which was cut -off, capped, and abandoned in- place. The pipelines are buried at a depth of approximately 5 feet and traverse both previously disturbed and un- disturbed areas. Installation of the two Thickener Underflow Pipelines involved: • Placement of temporary BMP's for drainage and sediment control from pipeline and construction areas • Removal and windrowing of soils materials from any new disturbance areas • Excavation of the pipeline trench, with temporary placement of excavated material adjacent to the trench • Excavation of boring/jacking pits on the edge of Haulroad B -2 and an existing drainage ditch on the north side of the existing railroad spur (as shown on Figure 49K -F1) and boring/jacking of 24 -inch secondary containment culvert under existing Foidel Creek road crossing culverts and railroad spur • Boring and casing of the Thickener Underflow Borehole TR09 -67 2.05 -97.6 11/10/09