2001-12-11_REPORT - C1980007 - Laserfiche WebLink

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• u Nydrolo~c Agra fnrnprcrarion and /mpocr Atrct~mrnr for Pamir Arca and Adjacrnr Arcm This new area was relatively dry with only small damp roof areas. Areas previously mapped as wet or damp are shown on Exhibit 11. Most areas were dry. The wet areas of the 1st West Submain were thought to be associated with sandstone channels which immediately or closely overlie the coal seam and with fracture zones in the Lane Pine Gulch area. Panel 1W1S Monitoring o[ well 38-H-1 during the 1989 water year indicates well water levels were still at pre- mining levels. The water level in this well dropped about 100 feet from January to July 1987 while retreat mining was occurring (November 1986 to March 1987). Well 38-H-1 is screened at three 20-toot intervals midway between the surface and the "F' seam coal. The "F' seam depth of cover is about 1000 Ceet at the 38-H-1 well location and averages about 900 feet over this panel. The total depth of well 38-H-I is 580 feet. No water was observed in the mine during devel- opment or retreat mining. Water observed in adjacent areas was thought to be coming from panel 1W2S because it did not appear until retreat mining occurred in panel 1W2S. During 1989, water levels in well 38-H-1 remained near pre- mining levels. Thus, data from well38-H-1 indicate groundwater in the barren member above the rubble zone will not suffer long-term impacts from secondary mining. Wells 38-H-2 and 38-H-3 provided little useful information (see hydrographs in Appendix 1). Subsidence apparently damaged the casings of both wells and connected them with the mine ventila- tion system. In well 38-H-2 the casing was ob- structed at 415 feet below the surface. Panel 1W2S Retreat mining of panel 1W2S was completed in November, 1987. Very little water was encountered in this panel during development or retreat. How- ever, Oow from panel 1 W2S appeared on the Moor of the 1st West Submain near the 1W2S seals shortly after secondary mining was completed. During the 4th quarter o(1987 Clow was estimated at 3 to 5 gpm. The flow increased to 5.5 gpm and 9.8 gpm during the 1st and 2nd quarters of 1988, respectively. Since this time [he flow declined steadily, to 1.2 gpm during the 3rd quarter of 1988 and to an unmeasurable amount by the end of 1988. During 1989 the area outside the panel seals dried up completely. Panel 1W3S Development mining in panel 1W3S began in March, 1987. Wct and damp roof areas were encountered from approximately 11 crosscut to 24 crosscut. These wet areas (roof drippers) produced very little Oow but were fairly extensive over a wide area. Some were associated with a badly fractured immediate mine roof (overburden averages about 700 feet). The water is probably associated with sandstone channels directly above the coal seam and with Lone Pine Gulch features. Retreat mining was completed during September 1988. To date, no evidence of water is visible near the panel seals or in adjacent areas. Panel 1W4S Development mining began in panel 1W4S during October 1987. The "F' seam depth oC cover averages about 500 feet over this panel. Roof drippers and wet areas were encountered in roof fractures and near the sandstone channel margins. The wet areas were not as large as those present in panel 1W3S and did not produce any measurable flows. Retreat mining was completed during 1989. No significant flows were encountered. Panel 1WSS Development and retreat mining of this panel occurred during 1989. The overburden continues to thin to the west; depth of cover averages about 400 feet over panel 1 WSS (ranging from <200 feet to 750 feet at the southern panel end). Coal height also thins to the west. Mining conditions were similar to those in panel 1 W45. Roof drippers and wet areas occurred, but no significant inflows were encountered. After the panel was retreat mined, a small wet area developed on the floor in the 1st