Laserfiche WebLink
LJ <br />that time it showed virtually no response to room-and-pillar mining. In February 1988 longwall <br />panel 1 was mined to within about 900 feet of this hole. Obviously, longwall mining disrupts the <br />' mined zone more than room-and-pillar mining, and the water level in TW2-17M did show a <br />response to mining at that time. The water level showed a decline of approximately 5 feet during <br />' this period. <br />As noted above, the 35-4M location is within LW-7 and was mined through in October 1994. The <br />' hole is venting air and has been capped. <br />Hole 2-7M is apparently more sensitive to room-and-pillar mining. The water level in this hole <br />has been dropping since mid-1987 when room-and-pillar mining approached to within about 700 <br />feet. This area was mined past in June 1988 and the water level has continued to drop, although <br />' no monitor holes were intercepted underground. In April 1990, LW3 was mined past this location. <br />The water level had dropped beyond our measurement capability from March 1990 through July <br />1994, however, the new equipment shows a dry blockage at 437 feet. Longwall panel 4 was <br />mined past this location in August 1991. <br />The hydrographs of the 'lower sandstone facies' are designated by the letter 'L' following the hole <br />number. The original hole 2-17L was plugged in eady fall 1985 as ft was feared the mine would <br />intercept it. As it fumed out, the hole was never encountered in the workings. As required by <br />' CMLRD, a new hole was drilled and completed in the 'lower sandstone facies'. From the time <br />the new hole was completed, the water levels in this hole have fallen. During May 1986, mining <br />' in gate road 2nd East intercepted an exploration hole, (21012-9) that had been drilled in 1978. <br />This hole had been plugged with heavy mud but leaked from both the mine roof and floor when <br />the hole was intercepted. Water flow from the hole in the roof was about 3 gpm (gallons per <br />' minute) and was plugged with a packer. The flow from the hole in the floor was on the order of <br />1 gpm and was plugged by pumping an expanding grout into the hole. This exploration hole is <br />located about 1500 feet from 2-17L and the leak in the floor may have reduced the piezometric <br />pressure in the 'lower sandstone facies• at 2-17L During March of 7987, another exploration <br />hole (21012-10) was intercepted by mining in gate road 3rd East. This hole also leaked at about <br />' the same rate from roof and floor. The hole in the roof was plugged with expanding foam grout. <br />The hole in the floor was plugged with Portland Cement pumped down a one inch line to about <br />100 feet. The leaks in both 21012-9 and 21012-10 are probably responsible far the fall in water <br />' levels detected at 2-17L during the fourth water year. Mining of LW-1 approached to within 500 <br />feet of this hole in February 1988. During this monitoring period, the water level ranged from <br />' 402.6 to 405.9 feet. Perhaps the combination of leaking exploration holes and floor cracking as <br />coal was removed by the longwall have reduced the piezometric pressure enough to drop the <br />water level to this point. <br /> <br /> <br />9 <br />1 <br />