2000-03-10_GENERAL DOCUMENTS - C1980007

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The deeply incised channels of these tributaries restrict the width of the alluvium, while [he stream gradient and the presence of resistant sandstone in the stream channels limit the thickness and downstream extent of the alluvium. Occurrences of groundwater have been noted in the Mesaverde Fotmation based upon information obtained from drilling, experience in the mines, and from the presence of springs and seeps in the region. This information also indicates that the only potential regional bedrock aquifer in the general area is the laterally continuous Rollins Sandstone. The laterally discontinuous lenticular sandstones within the Upper Mesaverde Formation support only localized groundwater flows. Recharge to the Rollins Sandstone occurs along outcrops, along subcrops beneath stream alluvium and in the channels of the North Fork and its tributaries. However, due to the steepness of the topography in the outcrop areas (i.e., sandstones are ledge formers) and the narrowness of the stream valleys, these local aquifers receive little recharge. Some recharge to the continuous units and much of the recharge to the more discontinuous, lenticular units will come directly from the percolation of snowmelt and precipitation downward through sandstone lens and along fractures. The same is true in the Jumbo Mountain area. Of 112 exploration drill holes at the West Elk Mine that were drilled prior to the mine opening, only three of the holes produced water from the F Seam at a production rate of 3 gpm or less. Three other holes in the Barren Member had rates of about 0.75 gpm. Some fractures and faults transect the Mesaverde Formation and extend vertically to the surface. These faults and fractures produce narrow bands of secondary permeability within the rock strata. Due to the low permeability of the rock strata within the Mesaverde Formation, these faults and fractures provide the primary path through which water flows both vertically between rock strata and horizontally within rock strata. When faults and fractures are encountered within the mines in the North Fork region, they generally produce mine inflows. The flow characteristics of each mine inflow associated with faults and fractures depend upon the lateral extent and the proximity of the fault or fracture to a stream valley. All inflows from these sources are characterized by an initial surge of water which then either decreases or ceases completely with time. Locally, water flow through fractures probably occurs more rapidly, as suggested by the seasonal fluctuation in discharge rates of some springs in the mine plan area. Mine inflow studies conducted as recently as 30