2020-08-20_REVISION - C1980007 (36)

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recharge areas have limited areal extent due to the steep dips of outcrops and the narrowness of the stream valleys; consequently, little recharge occurs. 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. The Mesaverde Formation is cut by fractures and faults that extend vertically to the surface. The faults and fractures produce narrow bands of permeability and provide the primary ground water flow path in the areas. When faults and fractures are encountered in mines in the North Fork region, they generally produce mine inflows. The flow characteristics of each mine inflow associated with faults and fractures depend on 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 1985 have shown that the primary source of inflows are from fractures in areas of low overburden. As previously described in this document, MCC encountered large inflows of water after mining through a fault/fracture system while conducting development mining in the B-seam in 1996 and early 1997. Significant mine inflows have not been experienced recently; as of the date of this findings document mine inflows have not satisfied the criteria for monitoring and sampling (discernable flows >5 gpm for>7 consecutive days) since water year 2011. Groundwater in the area can be expected to flow generally in a downdip (northward) direction, parallel to bedding, toward the deeper part of the Piceance Basin. Data from monitoring wells generally indicate downdip flow, although some closely spaced wells in the Barren Member have highly variable water levels. Some wells are dry, indicating no groundwater flow. Dry wells and variable water levels may result from areal variation in permeability. Generally, springs in the permit area seem to act independently of the bedrock water zones and appear to be surface features related to weathered and fractured bedrock. Springs tend to exhibit highly seasonal flow and discharge only during spring snow melt. Springs recharge and discharge in relatively small areas. 39