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~~,,. <br />' about 18 feet. This hole continues to exhibit a somewhat erratic water level. Future monitoring will <br />perhaps clarify the cause(s) of these changes. <br />Hole 2-7M is apparently more sensitive to room-and-pillar mining. The water level in this hole has <br />' been dropping since 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 has continued to drop, although no <br />' monitor holes were intercepted underground. In April 1990, LW3 was mined past this location. The <br />March 1990 water level had dropped beyond our measurement capability and remained so during <br />this monitoring period. Longwall panel 4 was 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 early fall 1985 as it 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 the <br />' new hole was completed, the water levels in this hole have fallen. During May 1986, mining in gate <br />road 2nd East intercepted an exploration hole, (21012-9) that had been drilled in 1978. This hole <br />' had been plugged with heavy mud but leaked from both the mine roof and floor when the hole was <br />intercepted. Water flow from the hole in the roof was about 3 gpm (gallons per minute) and was <br />plugged with a packer. The flow from the hole in the floor was on the order of 1 gpm and was <br />plugged by pumping an expanding grout into the hole. This exploration hole is located about 1500 <br />feet from 2-17L and the leak in the floor may have reduced the piezometric pressure in the "lower <br />sandstone facies° at 2-17L During March of 1987, another exploration hole (21012-10) was <br />' intercepted by mining in gate road 3rd East. This hole also leaked at about the same rate from roof <br />and floor. The hole in the roof was plugged with expanding foam grout. The hole in the floor was <br />plugged with Portland Cement pumped down a one inch line to about 100 feet. The leaks in both <br />21012-9 and 21012-10 are probably responsible far the fall in water levels detected at 2-17L during <br />the fourth water year. Mining of LW-1 approached to within 500 feet of this hole in February 1988. <br />t During this monitoring period, the water level remained beyond the capability of the monitoring <br />equipment (deeper than 300 feet). Perhaps the combination of leaking exploration holes and floor <br />cracking as coal was removed by the longwall have reduced the piezometric pressure enough t <br />drop the water level below 300 feet. Monitoring of this hole will con4nue to see if it recovers. <br />%• , <br />Monitor holes 2-7L.and TW2-7L are on the same location and apparently also responded to the two <br />leaking exploration holes. Longwall panel 3 was mined past this location in April 1990 and the water <br />' level has since dropped below 300 feet. Longwall panel 4 was mined past this location in August <br />1991. The water level in these two holes remained below 300 feet during this monitoring period. <br /> <br /> <br />10 <br />/• <br />1 <br />