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Kathy Welt and Christine Johnston March 7, 1997 (DRAFT) Page 5 from the fault. Approximately 260 acre-feet was returned to the North Fork via MCC's treatment system in MB-1 and MB-2R. The remaining water (40 acre-feet) has been pumped into the NW Panel sealed sump starting in November 1996. Assuming that the rest of the mine had inflows similaz to previous years (i.e., 12 gpm or 19 acre-feet per yeaz), the cumulative inflows to the mine from groundwater in 1996 totaled approximately 320 acre-feet (averaged over the year this is equivalent to about 200 gpm). Lab analysis showed the fault water chemistry to be typical of other bedrock water obtained from MCC's B-Seam monitoring wells (e.g., JMB-12). While some exploration and monitoring wells did show high temperatures at depth (a possible indication of the higher than expected temperature of this fault water), few of them indicated any inflows, let alone the flows which were encountered in the B East Mains fault. IV. NATURE OF NORTHWEST (NWl AND NORTHEAST (NE) PANEL SEALED SUMPS As a result of the unprecedented inflow of groundwater into the mine from the B East Mains fault, MCC began using the volume created by the previous mining of 1NW through 7NW longwall panels as temporary storage. As more information was obtained relative to the volume and characteristics of this groundwater inflow, and given the essential need to avoid overloading the mine water treatment system associated with ponds MB-1 and MB-2R, MCC decided to continue the use of this area as a "large capacity sump." This report focuses on the NW and NE Panel sealed sumps. There are tour small capacity sumps utilized during the mining operation throughout the mine that have a cumulative capacity of less than ] 0 acre-feet. By contrast, the combined capacity of the NW and NE Pane] sealed sumps, below the elevations of the seals, is over 800 acre-feet. In both the NW and NE Panel sealed sumps, the floor elevations drop to the northeast, sitnilaz to the dip of the coal seam. The resulting storage area, in plan view, matches the panel outline on the north and east with a southwestern boundary perpendicular to the dip of the coal seam (i.e., from northwest to southeast). The southwestem boundary is predicated by the elevation of the existing or proposed seals, as shown on Figure 2. Because of the dip of the coal seam, the deepest portion of each sump is potentially in the northeast comer; this elevation is 60 feet below the seals in the NW Panel sealed sump and 120 feet below the seals in the NE Panel sealed sump. The storage capacity in the NW Panel sealed sump at the lowest seal elevation is approximately 415 acre-feet, assuming a collapsed material porosity of 20 percent in the longwall panel area and 100 percent porosity of the development mining area. Using observed inflow rates from the B East Mains fault in 1996, the estimated time to fill the NW Panel sealed sump at an average inflow rate of 235 gpm (March to December 1996) is 1.1 years. The NE Panel sealed sump will be utilized after the NE Panels have been fully mined, probably in early 1998. The NE Panel sealed sump will have an estimated storage capacity of approximately 400 acre-feet. Using similar assumptions (235 gpm) to those used for the NW Panel sealed sump, the time to fill the NE Panel sealed sump area will be about l year. Together, the NW and NE Panel sealed sumps have a storage capacity of more than 800 acre-feet before the lowest seal elevations are reached. If the seal elevations aze reached, it will be necessary