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information contained in the Annual Hydrology Reports prepared for <br /> the mine, mining activities in both the F and B seams appear to have <br /> had no impact on groundwater in the Rollins Sandstone to date. <br /> The majority of Mountain Coal Company's hydrologic monitoring <br /> concentrates on mine water discharges and wells associated with B- <br /> Seam mining. Disturbances and changes to water quality, if they occur, <br /> will be manifested in B Seam discharge water and B Seam monitoring <br /> wells prior to any potential impacts to the Rollins Sandstone. The B <br /> Seam is separated from the Rollins by siltstones, shales, and another <br /> coal seam. It is unlikely that the Rollins Sandstone would be used as a <br /> primary drinking water source because of its great depth outside stream <br /> valleys and the ready availability of better quality surface water near the <br /> stream valleys. <br /> MCC has mapped the B Seam overburden thickness with potential areas <br /> of groundwater inflow highlighted. These areas of potential inflows, <br /> similar to the F Seam, are associated with fracture zones beneath <br /> drainages and near outcrops and areas of low overburden. A map of <br /> the potentiometric surface of the B Seam has been produced and can be <br /> reviewed in Exhibit 17A of the permit document. <br /> MCC has made inflow estimates for the B Seam mine plan that held <br /> true during the last five-year permit term. The "probable maximum" <br /> estimate of mine inflow shows a peak or initial inflow rate of about 15 <br /> gallons per minute (gpm) and a long term steady rate of about 10 gpm. <br /> This estimate is based on a rate of mining of 1.4 million tons per year <br /> and no ventilation portals extended to the northern outcrop. Recent <br /> experience shows that mine inflows have the potential to be much <br /> higher, at least for short periods of time, as indicated by measurement <br /> of inflows of as much as 2,500 gpm encountered in April 1996 while <br /> mining through a fault/fracture system in the B Seam. <br /> An estimate of mine inflow for the projected life of mine was also <br /> completed. This case showed an initial inflow rate of about 45 gpm and <br /> a long term steady inflow rate of about 30 gpm. Maximum inflow is <br /> estimated to be 100 gpm. This case was based on a mining rate of 2.8 <br /> million tons per year, installation of a ventilation portal along the <br /> outcrop, and an increased inflow constant for unknown conditions. <br /> On the north side of Jumbo Mountain, colluvium from an ancient <br /> landslide that removed the minable portion of the B Seam lies directly <br /> atop the lower portions of the B Seam. Water could be expected to <br /> infiltrate through the colluvium and migrate from bedrock units into the <br /> colluvium, emerging as springs or seeps down-dip of the proposed <br /> mining. <br /> 39 <br />