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Mayo and Associates, LC <br />I • <br />3.2.3 Fault Zone Groundwater <br />Groundwater has been encountered in 3 faults in the Energy West mines. These include <br />the Pleasant Valley Fault in the both the Deer Creek and Cottonwood/Wilberg Mines, and <br />the Roans Canyon Fault and the Left Fork Graben in the Deer Creek Mine (Figure 10). <br />Fault water has also been encountered along the Joes Valley Fault system in the Genwall <br />Crandall Canyon Mine (Mayo and Associates, 1997a, 1997b). The groundwater flow <br />regimes associated with each of these faults are described below. <br />3.2.3.1 Pleasant Valley Fault <br />The Pleasant Valley Fault System, which extends for 20 miles north of the PacifiCorp <br />~• mines, is a major north-south trending fault that is responsible for the Pleasant Valley <br />graben (Figure 10). In the PacifiCorp mine azea vertical fault displacement is less than <br />150 feet. The fault was exposed in both the Wilberg and Deer Creek Mines although the <br />graben begins north of the mines. The fault was first encountered in the early 1970s by <br />Peabody Coal Company during the construction of rock slopes and has been encountered <br />i in at least four different locations in the Wilberg Mine. When the fault was first crossed <br />during mining, groundwater discharge primarily occurred as floor upwelling in the <br />Wilberg mine and as roof drips in the Deer Creek Mine. The dischazge rate was small <br />and never exceeded 50 gpm in any location. PacifiCorp's initial monitoring location in <br />the Wilberg Mine discharged 50 gpm. Within 2 or 3 months, the flow from the fault had <br />diminished greatly and the sampling point became only a puddle on the floor (Semborski, <br />Evaluation of Potential Groundwater Inflows 33 February 24, 2004 <br />Associated with E Seam Mining, <br />® West Elk Mine, Somerset, Colorado <br />