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~J <br />1. <br />t <br />r <br /> <br /> <br /> <br />LJ <br /> <br />1 <br />L. <br />1 <br /> <br /> <br /> <br /> <br /> <br />Ground water inflow into the Orchard Valley mine occurs in <br />the following ways: <br />o dripping from the roof; <br />o inflow along the faults; <br />o seepage from ribs and floor; <br />o inflow from subsidence fractures; <br />o seepage through coal near outcrops. <br />Dripping from the roof is typically caused by the presence <br />of sandstone channels in the roof of the mined coal seam. This <br />type of inflow was experienced in various parts of the mine and <br />in the 9 East Submain, in particular. Dripping from the roof is <br />often related to roof instability problems. Water inflow in such <br />conditions is usually limited to less than one gallon per minute <br />and inflow only continues for several days. <br />Inflows related to faults are more consistent than dripping <br />from sandstone channels, however, no major quantities of water <br />inflow were encountered from faults crossed by mine workings. A <br />relatively steady inflow of approximately 2 gpm was observed from <br />a fault located at crosscut 40 on the North Main. <br />Mine inflow from the ribs and floor were experienced in the <br />BN-SE Submain around crosscuts 42 and 54, near the abandoned <br />Farmer's mine, where approximately 30,000 gallons of water <br />accumulated over two months. Approximately 150 gallons per day <br />were seeping into the mine near crosscut 20, North Intakes over a <br />period of about three months. Both of these inflows are probably <br />caused by seepage from the abandoned Farmer's mine which is <br />partially flooded. However, part of this inflow could originated <br />by seepage through the coal seam where the seam subcrops into the <br />stream bed of local ephemeral drainages. Monitoring well DH-70, <br />located in the area north of the Farmer's mine and installed in <br />perched sandstone aquifers above the mined seam did not indicate <br />any substantial drop in water level even when mining came close <br />to this well. This confirms that the occurence of water in this <br />particular part of the mine is not related to the sandstone <br />strata above the mined seam. <br />Water inflow into the mine related to subsidence effects <br />occured in the 2 1/2 West Panel. Caving of the roof strata after <br />pillar recovery at this location produced approximately 3.5 to S <br />gpm for about 60 days. The limited duration of the water inflow <br />from subsidence induced caving and fracturing confirms that no <br />significant aquifers are present above the mined coal seam. <br />water seepage into the Orchard Valley mine does not seem to <br />be highly influenced by changes in seasons. Snowmelt and high <br />runoff periods do not visibly increase the rate of mine inflow. <br />This confirms that most of the water inflow into the mine <br />2 <br />II\UB n~f. F.n CII~SI'I:f\\TS <br />