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25. The Division disputes that the bedrock surrounding the mine pool is of low <br />permeability. The Division asserts that the packer tests performed by the Operator are <br />unlikely to be representative of the entire hydrogeologic system. The Division provided <br />evidence that fractured igneous and metamorphic rock can have a hydraulic conductivity <br />100,000 times greater than the packer test results (the 22 packer test results gave a geometric <br />mean hydraulic conductivity of 4.7 x 10"7 cm/sec). The Division provided evidence that the <br />rock mass hydraulic conductivity falls within the range of sandstone. (Division power point <br />presentation, Range of Values of Hydraulic Conductivity and Permeability, from Freeze & <br />Cherry, 1979.) <br />26. Another possible conduit for contaminated water is possible unplugged <br />boreholes. All of the historic boreholes have not been accounted for - some may have caved <br />in. How any unplugged boreholes are contributing to the flow of contaminated water is <br />unknown. The Operator discusses the boreholes in the EPP. The Operator states "[p]otential <br />conduits from the flooded mine workings to the alluvium included historical exploration <br />boreholes that were drilled into the deposit from the valley floor ... [d]rill holes, near- <br />surface fractures, or rock foliation could provide potential conduits for low rates of flow <br />from the mine to the valley floor alluvium." EPP pp. 9-4 and 9-5. <br />27. The Operator and the Division also dispute what effect the geologic formation <br />known as the Schwartz Trend may have on the movement of mine pool water to Ralston <br />Creek and Reservoir. "At the mine site, the Schwartz Trend is characterized by brittle <br />fracturing and is the primary host for uranium." EPP p. 8-32. The Schwartz Trend intersects <br />Ralston Creek about 1,900 feet southeast of the mine. However, the total dissolved solids <br />(based on electrical conductivity tests at the point where Ralston Creek flows over the 300- <br />foot wide exposure of Schwartz Trend rocks) abruptly increase where the creek crosses the <br />Trend. EPP p. 8-32. The Division asserts that the cone of depression has not fully recovered <br />to allow contribution from the mine pool to Ralston Creek via the Schwartz Trend. <br />However, future contribution is inevitable because of the direction of the hydraulic gradient. <br />28. There is no dispute that while the mine was dewatered a cone of depression <br />formed, lowering the groundwater level and creating a hydraulic gradient away from Ralston <br />Creek. <br />29. There is also no dispute that with the mine flooded, the hydrostatic gradient is <br />restored. "[W]ater moving through fractures generally moves from areas of high topographic <br />relief to areas of low topographic relief. The dominant natural direction of groundwater flow <br />in the deep bedrock is generally eastward." EPP p. 8-40. In other words, water flows from <br />high to low. The Operator notes "[w]hen the flooded mine pool reached the 6540 level in <br />about February 2007, the groundwater gradient was essentially zero (no driving head <br />between the creek and the mine pool). Since that time, a low hydraulic gradient has existed <br />from the mine to the creek." EPP p. 9-4, fn. 17. The groundwater hydraulic gradient is from <br />the mine pool to Ralston Creek and Reservoir. The Division asserts that "[e]xpecting water <br />in the mine pool to migrate in the direction of the hydraulic gradient is an application of <br />basic ground water hydrology and scientific common sense." <br />Cotter Corp. <br />Schwartzwalder Mine 5 <br />M-1977-300 <br />MV-2010-018