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previously reported for the Fish Creek Borehole. TCC will continue to monitor the concentration, and anticipates the concentration to return to historic levels by late summer, 2000 or 2001. • In regazds to future impacts, TCC will not discontinue pumping of the underground sump for the extended periods of time. This will eliminate the potential for the above situation to occur in the future. Once mining is completed at the facility, no further discharging will occur. Based upon this, there should be no impact to the postmining land use. (9) ReWrn of Coal Mine R'asle to Abandoned Workings (a Each plan shall describe the design. operation and maintenance of am' propused coal processing mine waste disposal facility, including Flow diagrams and any vlher necessary drawim~s and maps, which must meet [he standards of 2.10, for the approval of both the Division and [he Mine Safety and Health Administration in accordance with 4.11.3. (b) Each plan shall describe [he source and qualih~ of waste to be stored. area to be backlilled. percent of the mint roid to be tilled, method of constmcting underground retaining walls, influence of the backfilling operation on active underground mine operations, surface area to be supported by the backlill, and the anticipated occun~ence of surface effects following backfillinR. (c) The applicant shall describe the source of hydraulic trmtspon medium, method of dewa[erine the placed backlill. retainment of water underground, treatment of water if released to surface streams, and the etTect on the Irodrvlo¢ic regime. dl The plan shall describe each permanent monitoring well to be located in the backlilled area. the stratum underlying the mined coal. and gradient from the backlilled area. • (e) fhe requirements of 2.053 shall also apply to pneumatic backfilling operations, except where the operations are exempted by [he Division from requirements specifying hydrologic monitoring. RESPONSE TCC is planning on returning the thickener underflow generated at the Prep Plant to the abandoned workings located in the Eastern Mining District. The location of the area to receive the underflow is shown on Map 23. In the plant the thickener underflow goes to a filter press for dewatering, and then this material is combined with the course refuse and hauled to the refuse pile for placement. It is TCC's intent to pump the thickener underflow into the abandoned mine works as opposed to mixing it with the course refuse for placement in the refuse pile. The thickener underflow is typically a 25 percent solids (17.8 tons per hour), 214 gallons per minute flow mixture of ash and coal fines (28 mesh x 0). The mixture would be piped to the abandoned works located in the EMD, where the fines would settle out and the water would be recycled back to the wash plant via the mine sump for settling. Map 24 shows where the water will be pumped back outside and recycled to the plant. The quality of the thickener underflow that will be piped to the underground workings is typically 25 percent ash and 75 percent coal fines material (28 mesh x 0). Also, Exhibit 9C, Underflow Chemical Characterization, provides data on selected chemical constituents found in the underflow. The underflow is moved in a slurry flowing approximately 214 gallons per minute. The water quality of the slurry is the typical spoils water generated at the adjacent Colorado Yampa Coal Company. It is TCC's intent that the water used to slurry the mixture underground will be recycled to the plant as make-up water. • Map 23 shows the area that will be filled with the refuse material over the next 20-year period. The percent of the EMD abandoned workings that will contain these refuse fines, after the typical annual production for a 20-year period, will be 1.63 percent. This is based on 25,000 tons of refuse fines generated per year and TR 01-39 2.05-97.1 09/17/01