Laserfiche WebLink
Future Inflow EstimatesAll of the future mining will be in areas of high cover with almost all of it under greater <br />than 1000 feet and small areas of 700 to 1000 feet of cover. None of the future mining will be in areas of steep dip <br />• or large structural flexure. All future mining areas will be more than 3000 feet from a subcrop of the coal. <br />Therefore, it is not anticipated that any new sieniflcant sustained flows will be encountered. Therefore, additional <br />inflows are expected to be the same or lower than those measured per unit areas in outer pans of the mine. Since <br />the average cover in the NMD and NWMD will be greater than ]000 feet, lower unit inflows are anticipated. <br />Using the factor of 0.027 gpm/feet developed for the WMD, the inflow to the EMD (excluding 6 Right) will <br />increase to 85 gpm due to the additional 400 acres to be affected plus 200 gpm from the 6 Right inflow for a total <br />of 285 gpm. The additional approximately 10,000 acres of the NMD and NWMD will yield an estimated 270 <br />gpm. When these estimates were compared against measured mine discharges and water balance calculations a <br />good match was found. The estimated total ground water inflow will increase from 365 gpm in 1998 to the 655 <br />gpm at the end of mine life (Exhibit 49, Table E49-4). <br />Mine Water Balance The inflows and outflows from the mine can be estimated to determine a mine water balance. <br />Historically two different mine water balance conditions have existed: I) when water has been stored in the sump <br />at the northwest comer of the WMD and 2) when all water that entered the mine has been pumped out. From the <br />beginning of mining to July 1996, the mine has been kept dewatered except for the sealed 1st South Panels. From <br />Ju y 8 to August ] 998, the northwest corner of the WMD was allowed to flood with groundwater inflow to the <br />SWD d other water pumped into the SWD from the NMS and the EMD. Since August ] 998, some pumping of <br />e sump has been conducted. <br />The water balance consists of these main components: <br />• Groundwater inflow to the workings <br />• Water pumped into workings for use by the equipment for water sprays and cooling <br />• • Water pumped out of the workings via Site 109 (NMS) and Site 1 IS (at the Fish Creek Borehole, <br />located in the WMD) <br />• Water removed from the mine as added moisture [o [he coal <br />• Water added to storage in the underground sump at the Fish Creek Borehole, located in the WMD. <br />The water balance for water years 1989 to 1998 is presented in Exhibit 49, Table E49-3 and shown on Map 16. <br />The water balances were calculated beginning when long-wall mining started. The inflows to the MNS were <br />estimated to be constant at 45 gpm based upon past mine inflow studies. For years ]989 to ]993 inflows to the <br />WMD were calculated based upon the total of the other inflows minus the outflows. In 1994, the pool at the Fish <br />Creek borehole began to expand. For water years 1994 to 1998 the excess inflow was assigned to the sump and <br />the WMD, inflow was estimated [o be 55 gpm based upon the Mine Inflow Surveys. <br />The inflows to the EMD were estimated from the areas mined and the actual inflow measured. In ]995 <br />approximately 200 acres were affected by longwall mining yielding an estimated 5 gpm. Some fault inflows <br />where encountered at the end of the water year. In 1996, approximately 800 acres in the EMD were affected by <br />mining yielding approximately 20 gpm including the fault inflows. ]n ] 997, excluding the inflows from 6 Right, a <br />total of approximately ]400 acres were affected for 35 gpm plus 10 gpm from the Southeast Submains. In 1998, <br />excluding the inflows from 6 Right, a total of approximately 2000 acres were affected yielding an estimated 55 <br />gpm plus 10 gpm from the Southeast Submains, which are located in the EMD. All the water that flows from the <br />active longwall and continuous miner equipment plus all the inflows to the EMD excluding the 6 Right inflow are <br />collected in a sump at ]0 Right. The sump has been maintaining a constant pool level by pumping at <br />approximately 170 gpm since 1998. The estimated inflows to this area are 65 gpm from groundwater and 1 I 1 gpm <br />from the equipment for a total of ] 76 gpm. Since these two figures closely match, the EMD portion of the water <br />balance appears to be reasonable. <br />r1 <br />U <br />TR99-32 2.05-137 APJPJR®VED F[B 0 8 2000 1/3/00 <br />