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SUNDAY MINE COMPLEX-HYDROGEOLOGIC REPORT <br /> have required observation of water levels since before mining extended into the Salt Wash <br /> aquitard. <br /> Based on the limited description of dewatering operations that may have occurred (CDM, 2009 <br /> and CDM and Denison 2012), it seems unlikely that any potentiometric surface depression <br /> impact was substantial. At the writing of this report, PRM has not proposed plans to dewater <br /> portions of the mines, but is focusing instead on mining in unsaturated areas of the Salt Wash. <br /> 11.4 Groundwater Velocity and Travel Time <br /> Groundwater flow velocity is of interest in addressing the potential for travel time of potential <br /> dissolved contaminants of concern to possible points of exposure to receptors. A worst case <br /> scenario may be seen where groundwater flow from the SMC is to the southwest or west toward <br /> potential receptors located in Disappointment Valley and the Dolores River. Average linear <br /> groundwater velocity (vx) is a one-dimensional parameter used to describe lateral flux of water <br /> across a unit cross sectional area of pore space along a downgradient flow path. v, is <br /> calculated by the equation: <br /> vx = K • ah <br /> ne 31 <br /> where: K = hydraulic conductivity (ft/day) <br /> ne = effective porosity <br /> 8h/31 = hydraulic gradient (ft/ft) (Fetter, 1993) <br /> Hydraulic conductivity, K, is directly proportional to vX. The hydraulic conductivity for sandstones <br /> of the Morrison Formation in the vicinity of the SMC was estimated by Jobin (1962)to be 1.11 x <br /> 10"4 centimeters per second (cm/s) or 0.31 ft per day (ft/d) (converted from darcy permeability). <br /> Slug tests conducted for this report indicated that K values were locally much lower, ranging <br /> from 5.41 x 10"' cm/s (0.001534 ft/d) to 1.79 x 10-6 cm/s (0.005066 ft/d). Effective porosity, the <br /> porosity through which flow can occur, is estimated at 0.16 based on work done by Keller <br /> (1960). The hydraulic gradient is considered to be small based on the heads measured between <br /> the mine workings and the river. Conservatively, the hydraulic gradient was selected to be 0.01, <br /> which is equivalent to a head difference of 195 ft between the flooded workings of the West <br /> Sunday Mine and the Dolores River. The estimated distance from the flooded workings to the <br /> Dolores River is 19,000 ft (3.6 miles). Based on a range of these parameters, the following <br /> Western Water& Land, Inc. 44 <br />