2015-02-26_REVISION - C1982056 - Laserfiche WebLink

Home Browse Search

majority of this water is recycled. Mine Water Balance: System inputs and outputs for the mine can be estimated to determine a mine water balance. Historically (1983 through August 1998) two different mine water balance conditions have existed: 1) When water has been stored in the sump at the northwest corner of the SWMD and 2) When all water that entered the mine has been pumped out. From the beginning of mining to July 1996, the Mine was kept dewatered except for the sealed 1 -South Panels. From July 1998 to August 1998, the northwest corner of the SWMD was allowed to flood, with groundwater inflow to the SWMD and other water pumped into the SWMD from the NMD and the EMD. Since August 1998, sealed workings in the southern portion of the EMD have been established as a temporary water storage area. Some pumping of and discharge from the SWMD and EMD sumps has occurred to maintain the water level in the flooded workings below the seals. With installation of the new longwall in 2006 and the new washplant in 2007, mine water use increased to the point where only intermittent discharge was necessary to maintain stable water levels. Therefore, a simplified mine water balance, developed in early 2007, reflected the practical reality that any difference between system inputs and outputs results in a corresponding increase or decrease in mine water storage levels. In 2008, changes in MSHA regulations re: water stored in sealed mine areas, and an unanticipated rapid rise in water levels, resulted in changes in mine water handling practices. The unanticipated rise in water levels in the sealed underground mine workings is believed to have resulted from several factors, including; coal fines discharge rates that were greater than anticipated during start-up of the new washplant; reduced discharge rates at the Fish Creek borehole due to maintenance issues with the water - treatment system; a historic error in the reference datum for water level measurements; and a "break- over" of water impounded underground when the water level reached a high point in the sealed mine workings, with resultant rapid filling of downgradient areas. Several overland pipelines were installed, providing the capability to transfer water from either the Fish Creek or TORT dewatering wells to the Area 1 Pit for storage, use, or discharge through Sedimentation Pond D. Discharge was also initiated on a temporary basis from the IORT dewatering installation to Foidel Creek. While the water balance has changed over time with development of new mining areas and changes in storage, use, and discharge, it generally consists of the following primary components: System Inputs • Groundwater inflow to the mine workings • Water contributions from the potable water well • Operational use from Pond A and the Area I Pit System Outputs • Surface moisture shipped with the coal product • Mine ventilation losses • Washdown water discharged through the sedimentation ponds (or lost to evaporation) • Evaporative losses from the surfaces of all mine impoundments System Balance * Mine water discharge (previous historical and current intermittent practice) • Changes (positive or negative) in the volume of water stored in sealed mine workings • Mine water recycled through the mine dewatering wells and mine water handling and treatment system The water balance for water years 1993 to 2002 is presented in Exhibit 51, Table E51 -3. The original water balance was calculated shortly after longwall mining started. The inflows to the NMD were estimated to be constant at 45 gpm, based upon past mine inflow studies. For years 1989 to 1993 inflows to the SWMD were calculated based on the total of the other inflows minus the outflows. In 1994, the pool at the Fish Creek borehole began to expand. For water years 1994 to 2002, the excess inflow was routed to the sump, increasing the stored water volume, and the SWMD inflow was estimated to be 55 gpm, based on mine inflow surveys at the time. TR13 -83 2.05 -137 11/03/14