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Mayo and Associates, LC <br />• <br />~~ <br /> <br />I~ <br /> <br />i <br /> <br />1 <br /> <br />vertical displacement (Davis and Doelling, ]977; Danielson and Sylla, 1983). Joes <br />Valley fault forms the eastern edge of the Joes Valley graben. <br />Groundwater inflows have occurred in the vicinity of Joes Valley Fault (Mayo and <br />Associates, 1997a, b). These inflows have been small (i.e., 50 - 300 gpm) and locally <br />ceased as down dip sections of the fault were encountered or as the system naturally <br />dewatered. Water dischazged from the mining face, from the mine roof about 200 feet <br />from the fault, and from fractured coal in the floor along an exposed reach of the fault in <br />the mine. The upwelling water did not appear to be under significant confining pressure <br />and the inflow rates were small. <br />A in mine groundwater sample collected from Joes Valley Fault -Main West fault had a <br />14C age of 2,500 yeazs and did not contain 3H . A sample collected from a well <br />completed in the underlying Spring Canyon Member of the Staz Point Sandstone, MW-7 <br />that is located 200 feet from Joes Valley Fault, had a'4C age of 5,000 years and did not <br />contain 3H. A sample collected from a fractured sandstone channel in the mine roof, 5`h <br />West fault, located about 300 feet from Joes Valley Fault, had a radiocarbon age of 3,500 <br />yeazs and a minor 3H content (0.95 TLT). Because the Joes Valley Fault forms the eastern <br />boundary of the Joes Valley Graben, locally the fault damage zone is under tension. The <br />3H content of the 5`" West fault sample suggest a small amount of vertical leakage from <br />the neaz surface environment. <br />Eva]uation of Potential Groundwater Inflows 39 <br />Associated with E Seam Mining, <br />West Elk Mine, Somerset, Colorado <br />February 24, 2004 <br />