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West Elk Mine <br />and slug test analysis. Transmissivity values from pumping tests were estimated from Lohman <br />(1975), using the following equation: <br />Q _ 4 ~r T <br />s 2.301og~o C2.25Tt} <br />lrS)) <br />Where: <br />Q = dischazge (gaUday) <br />T = transmissivity (gaUday/ft) <br />r = radius of the well (ft) <br />t = duration ofpumping (days) <br />s = drawdown (ft) <br />S = storage coefficient (estimated 0.001) <br />The following sections discuss each of the monitored formations within the pemut azea and their <br />hydrogeologic characteristics. For the most part, the bedrock units represent the inactive <br />groundwater zone particularly at depths greater than about 500 feet below the ground surface <br />and a distance of approximately 1,000 feet inward from exposed cliff faces. The colluvium <br />and alluvium, along with the near surface exposures of the bedrock units, represent the active <br />groundwater zone. <br />Rollins Sandstone <br />• In the past, the Rollins Sandstone was thought to be a potential aquifer of regional importance, due <br />to its azeal extent. However, more recent data and analyses indicate that the Rollins Sandstone is <br />not a regional aquifer (Mayo, 1998). Additional discussions are provided in Exhibits 17A,18, and <br />18B. <br />MCC has constructed four monitoring wells completed in the Rollins Sandstone. These wells <br />include R-1, LP-1, SOM-128-H, and So.W-3 (See Map 34). No water was ever noted in LP-1 <br />primarily because the Rollins Sandstone is exposed to the atmosphere upgradient of this area. LP-1 <br />was removed from the monitoring program in June 1998 when the Lone Pine Gulch ventilation <br />portals were closed and reclaimed. SOM-128-H and So.W-3 were also removed from the <br />monitoring program in 1999. Monitoring well So.W-3 was rendered useless when B Seam mining <br />cut through the well. <br />Considerable hydrogeologic pazameter estimations have been conducted on the Rollins Sandstone <br />in the vicinity of the mine, particularly in the areas associated with the BEM and 14HG Faults. <br />As shown in Table 5, a pumping test conducted on monitoring hole R-1 for just the Rollins <br />Sandstone portion of the well indicates that the formation was capable of producing only <br />approximately 3 gpm. Mayo and Associates (1998) reports both horizontal and vertical <br />hydraulic conductivity values for various intervals within the Rollins Sandstone. In general, <br />horizontal hydraulic conductivity values range from 1.0 x 10-0 to 1.2 x 10"Z ft/d while measured <br />vertical values ranged from 1.7 x 10-0 to 1.8 x 10"Z ft/d. <br />~~ <br />1.04 -63 Revised November 1004 PRI G <br />