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Whetstone, <br />Associates <br />Technical Memorandum <br />landfill covers have a hydraulic conductivity less than 1x10-5 cm/sec. Soil barriers in <br />hazardous waste landfills are typically compacted to no greater than 1x10"7 cm/sec. <br />Mine Inflow. At its total maximum depth of 2,200 feet, when the mine was fully dewatered <br />groundwater inflow to the Schwartzwalder mine was only 189 gpm. These very low flow <br />rates indicate that rock mass has very low permeability, and there are no high-permeability <br />faults or conduits that could convey water to (or from) the underground workings. If high- <br />permeability conduits existed, then inflow to the mine would have been significantly greater. <br />WRT Pilot Test. Sustained pumping rates during a pilot test in July and August, 2007 (with <br />the pump set at 27 ft below the collar of the #2 shaft in the Steve Level) were only 1.2 gpm. <br />It should be noted that the entire mine workings were in connection with the shaft, with no <br />resistance to flow in the workings themselves. Calculations that evaluated the mine pool as a <br />2,200 feet deep "large diameter well" show that an overall bedrock permeability of 2.8x10-7 <br />cm/sec would produce the observed 1.2 gpm pumping rate with 14.6 feet of drawdown <br />(Whetstone, 2007). <br />Saturated Zone Above the Mine. Monitoring wells MW10 and MW11 are located on the <br />hillside above the mine (Error! Reference source not found.) and contain water because the <br />rock is too low in permeability to drain into the unsaturated workings below. The low <br />permeability of the rock mass prevents groundwater from draining from near surface, where <br />the wells are located, downward into the unsaturated upper mine workings. The same <br />process prevents groundwater in the mine pool from draining toward Ralston Creek, or any <br />other point. <br />Creek Flow. Ralston Creek was never drained during mining, although the mine was <br />dewatered to nearly 2,200 feet below the creek level. If a strong hydraulic connection <br />existed between the mine and the creek, then the creek flow would have dried up as a result <br />of mine dewatering during operations. Instead, no effect on flow in the creek was <br />discernable. <br />• Mine pool dewatering and treatment at this time will preclude the opportunity to <br />demonstrate that treatment of the alluvial groundwater will address the Ralston Creek <br />issues, and that mine dewatering and treatment are not necessary. <br />Based on technical information compiled by the Operator and its consultants, the Operator <br />believes that treatment of groundwater in the alluvium and fill will be effective in reducing <br />uranium concentrations in Ralston Creek. Further, if pumping from Sump 1 does not capture <br />sufficient alluvial groundwater to meet drinking water standards in the creek, the Operator is <br />committed to pumping and treating groundwater from additional locations in the alluvium <br />and fill. The Operator needs the opportunity to demonstrate that this approach will be <br />successful in lowering uranium concentrations in Ralston Creek at the point of compliance <br />and at the Long Lake Head Gate sampling station. <br />• The cost of treating the mine pool would be several million dollars per year. <br />4109C.100731 16