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West Elk Mine <br />with the fault zone (oriented in a N60°E direction) occurred while driving the #6 Entry <br />between cross-cuts #16 and #17. At this location the mining encountered a series of <br />small faults containing little water. The largest displacement was approximately 2.5 feet <br />with the upthrown side to the southeast. <br />After mining the #16 and #17 cross-cuts between the #5 and #6 Entries, mining was <br />advanced along the #5 Entry into the fault between cross-cuts #17 and #18. The fault <br />displayed a similar orientation and had an apparent displacement of approximately 6 <br />feet in one area. The fault dip angle was estimated to be 65° to the northwest, again <br />with the upthrown block to the southeast. Water was initially encountered on March <br />16, 1996 at an estimated rate of 350 gpm increasing to a maximum rate of <br />approximately 800 gpm within 48 hours, primarily from the roof and floor. This inflow <br />rate dropped to nearly 350 gpm by the end of March 1996, and dried up completely <br />after the #4 Entry was advanced through the fault. <br />MCC worked quickly to contain and control the inflow for the safety of the miners and <br />to restore mining in the section. Pumps and piping were installed to discharge the flows <br />from the mine. Because of the unprecedented flows, cross-cut #17 was pushed <br />northward across the remaining B East Mains into the southeast corner of the lONE <br />longwall panel tailgate. This area was mined to create a temporary small capacity <br />sump (NE Tailgate sump) from which the water could be pumped to other areas of the <br />mine prior to its eventual discharge out the portal. All discharges from the mine were <br />contained and treated (i.e., chemical addition, flocculation, sedimentation) in ponds <br />MB-1 and MB-2R before being released in accordance with NPDES/CDPS permit <br />requirements. <br />The ground surface above the fault is in the upper reaches of Sylvester Gulch. Several <br />days of investigations were made during the spring of 1996 to assess whether there was <br />any surface evidence of the fault or surface impacts from the fault inflows. In the <br />general vicinity of the surface projection of the fault, there is a significant sandstone <br />outcrop forming the east side of Sylvester Gulch. More than 1,000 feet of this outcrop <br />was inspected along its base and from across the drainage to assess whether an offset in <br />the unit could be detected (i.e., surface indication of the fault). No evidence of the fault <br />was observed. Many of the spring and seep locations in the valley were also visited to <br />observe flows and assess the general temperature (by touch) of the spring water. In all <br />cases, the waters encountered in Sylvester Gulch were observed to be considerably <br />colder than the water emanating from the fault, and the observed surface flows in <br />Sylvester Gulch were considerably less (<1 cfs) than those observed flowing into the <br />mine (<4.5 cfs) upchannel from the fault location. There was no change in the flow <br />regime of Sylvester Gulch in the vicinity of the fault. <br />Previous work by the USGS in 1989 suggests that Sylvester Gulch is a fracture- <br />controlled drainage along its north-south reach prior to its confluence with the North <br />Fork. The N60°E orientation of the BEM Fault is counter to this and crosses the <br />. drainage with no obvious surface evidence (stratigraphic or topographic). MCC had <br />not observed the fault or groundwater in previous exploration in the area or from <br />2.05-250 Revised June 1005 PRlO; Rev. March 2006; Rev May 2006 PRIO <br />