REP19780 - Laserfiche WebLink

Home Browse Search

• • Data lntervrem~ion and Lively dry with only limited wet roof areas. Areas previously mapped as wet or damp are shown on Exhibit I1. The wet areas of the 1st West Submain were thought to be associated with sandstone channels which immediately or closely overlie the coal scam and with fracture zones in the Lone Pine Gulch area. Panel iW1S Monitoring o[ well 38-H-1 during the 1990 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- foot intervals midway between the surface and the "F' seam coal. The "F" seam depth of cover is about 1000 feet at the 38-H-1 well location and averages about 900 feet over this panel. The total depth of well 38-H-1 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 1 W2S because it did not appear until retreat mining occurred in panel IW2S. During 1990, water levels in well 38-H-1 remained near pre- mining levels. Thus, data from well 38-H-1 indi- cate 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 I). 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 1 W2S Retreat mining of panel IW2S was completed in November, 1937. Very little water was encountered in this panel during development or retreat. How- ever, Ilow from panel 1 W2S appeared on the (loot of the Ist West Submain near the lW2S seals shortly after secondary mining was completed. During the 4th quarter of 1987 flow was estimated Asreumrnt far the Pcnnit and Adjacent Arear at 3 to 5 gpm. The ^ow increased to 5.5 gpm and 9.8 gpm during the 1st and 2nd quarters of 1988, respectively. Since this time the Pow declined steadily, to 1.2 gpm during the 3rd quarter of 1988 and to an unmcasurablc amount by the end of 1988. During 1989 the area outside the panel seals dried up completely. The area remained dry throughout 1990 as well. Panel.i W3S Development mining in panel 1W3S began in March, 1987. Wet 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(ovcrburdcn averages about 700 fceQ. The water is probably associated with sandstone channels directly about the coal scam 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 1 W4S Development mining began in panel 1W4S during October 1937. The "F" scam depth of cover aver- ages abotn 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 IW3S and did not produce any measurable (lows. No significant nows were encountered during retreat mining in 1939. No in-mine (lows were observed during 1990. Panel 1 W5S Development and retreat mining of this panel occurred during 1989. Theovcrburdcn continues to thin to the west; depth of cover averages about 400 feet over panel 1WSS (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 W4S. Roof drippers and wet areas occurred, but no significant inflows were encountered.