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Mayo and Associates, LC <br />~~ The fault was first encountered in the mine in January 1990. Substantial groundwater <br />inflows of several hundred gallons per minute occurred in each of the entries. The water <br />discharging from the fault was entirely from the roof and appeared to be related to a <br />large, overlying sandstone channel. A small synthetic fault with Less than 5 feet of offset <br />associated with the Roans Canyon Fault was subsequently encountered in April 1940. <br />Peak discharge was estimated as 5,000 gpm (Semborski, Personal Communication, <br />1997). The last measurement of discharge from the fault zone, from an established <br />monitoring point, was 150 gpm. <br />Groundwater from the Roans Canyon Fault was encountered with a series of test wells <br />including TW-10, a 1,100-foot long horizontal hole drilled into the fault system in the <br />Deer Creek Mine. It was apparent during drilling that groundwater issuing from TW-10 <br />was from a sandstone channel that had been highly fractured. Ubiquitous iron oxide in <br />the fractured sandstone indicated that water in the fracture had been in communication <br />with atmospheric gases {Semborski, Personal Communication, 1997). Although TW-10 <br />is under considerable cover (1,200 feet), it is located near cliff faces. The cliff face rocks <br />are extremely fractured and open to recharge water. The average temperature of <br />groundwater from TW-10 is 7.7°C while the average temperature of other groundwaters <br />in the Deer Creek Mine is 11,8°C. <br />The discharge rate from TW-10 declined from about 80 gpm in 1989 to about 5-6 gpm in <br />1997. Groundwater sampled from this location in 1996 contained anthropogenic "C and <br />had a 3H content of 20.8 TU. These data and the relatively cold water temperature <br />Evaluation of Potential Groundwater Inflows 35 February 24, 2004 <br />Associated with E Seam Mining, <br />West Elk Mine, Somerset, Colorado <br />