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Mayo and Associates, LC <br />'• Ground water enters the PacifiCorp mines through three pathways (Mayo and Associates, <br />1997a, b,c): <br />I. roof inflows from sandstone channels in the Blackhawk Formation, <br />2. floor seeps, from the Spring Canyon Member of the Staz Point Sandstone, and <br />3. fault-related damage zone of the Roans Canyon Fault. <br />Energy West has monitored groundwater inflows into each of its mines since 1979. <br />Inflows aze described below. <br /> <br /> 3.2.1 Sandstone Channel Groundwater <br />t The most common source of groundwater entering the mine environment is from <br /> sandstone channels that overlie the coal seams. This water issues from both roof bolt <br /> holes and from post mining fractures that form in the sandstone. Detailed mapping by <br /> Energy West in the Deer Creek, Trail Mountain, and Cottonwood mines illustrate the <br /> braided character of the channels (Figure 8). The channels maybe several miles long, up <br /> to 1000 feet wide, and are commonly 25 to 30 feet thick. Varying amounts of water <br />' saturation of the channel sands and interfluvial clays result in wet and dry regions in the <br /> mines. <br />It is common in `vet"portions of the mines for roof-drip groundwater to be encountered <br />at the mining-face during mining operations. Most roof drips typically aze short lived, <br />persisting for only a few weeks before the flow completely ceases. Thus, the roof drips <br />'• appeaz to "dry up"behind the mining operations. The dischazges from these short-lived <br />Evaluation of Potential Groundwater Inflows 27 February 24, 2004 <br />Associated with E Seam Mining, <br />West Elk Mine, Somerset, Colorado <br />