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1 <br />1 <br />Hole 2-7M is apparently more sensitive to room-and-pillar mining. The water level in this hole <br />' had dropped in mid-1987 when room-and-pillar mining approached to within about 700 feet. <br />This area was mined past in June 1988 and the water level had continued to drop, although <br />' no monitor holes were intercepted underground. In April 1990, LW3 was mined past this <br />location. The water level had dropped beyond our measurement capability from March 1990 <br />through July 1994, however, the new equipment shows a dry blockage at 437 feet. Longwall <br />' panel 4 was mined past this location in August 1991. Hole 35-4M cannot be monitored <br />because it is venting gas and is presumed dry. <br />' The hydrographs of the "lower sandstone facies" are designated by the letter "L" following the <br />hole number. The original hole 2-17L was plugged in early fall 1985 as it was feared the mine <br />' would intercept it. As it turned out, the hole was never encountered in the workings. As <br />required by DMG, a new hole was drilled and completed in the "lower sandstone facies". <br />' From the time the new hole was completed, the water levels in this hole have fallen. During <br />May 1986, mining in gate road 2nd East intercepted an exploration hole, (21012-9) that had <br />been drilled in 1978. This hole had been plugged with heavy mud but leaked from both the <br />' mine roof and floor when the hole was intercepted. Water flow from the hole in the roof <br />was about 3 gpm (gallons per minute) and was plugged with a packer. The flow from the <br />' hole in the floor was on the order of 1 gpm and was plugged by pumping an expanding <br />grout into the hole. This exploration hole is located about 1500 feet from 2-17L and the <br />leak in the floor may have reduced the piezometric pressure in the "lower sandstone facies" <br />' at 2-17L. During March of 1987, another exploration hole (21012-10) was intercepted by <br />mining in gate road 3rd East. This hole also leaked at about the same rate from roof and <br />' floor. The hole in the roof was plugged with expanding foam grout. The hole in the floor <br />was plugged with Portland Cement pumped down a one inch line to about 100 feet. The <br />leaks in both 21012-9 and 21012-10 are probably responsible for the fall in water levels <br />detected at 2-17L during the fourth water year. Mining of LW-1 approached to within 500 feet <br />of this hole in February 1988. During this monitoring period, the water level ranged from <br />' 408.0 to 423.0 feet. Perhaps the combination of leaking exploration holes and floor cracking <br />as coal was removed by the longwall have reduced the piezometric pressure enough to drop <br />the water level to this point. <br /> <br />1 <br />1 <br />1 <br />e <br />