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Drawing down the mine pool would not have a "pump back" effect for any mine pool water <br />currently residing between the mine and the creek. Historical mine pumping records clearly <br />indicate that pumping from the mine pool did not dry up (or pump back) water in the alluvium. <br />Therefore, if the mine pool were drawn down, corresponding reductions in uranium <br />concentrations in the creek may not be realized for years because uranium that currently resides <br />between the mine and the creek would not be captured (or pumped back) by mine dewatering. <br />Lag times in groundwater flow could undermine a key premise and objective of temporary mine <br />dewatering (to rapidly improve water quality in the creek). <br />Reasons that mine dewatering /active treatment could only partially satisfy Criterion 1 with <br />respect to any water seeping into the alluvial fill include the fact that solid source term materials <br />outside of the mine would still need to be addressed, and that there are additional delays that <br />would undermine rapid improvements in water quality. Active water treatment would take at <br />least a year to implement due to the complexities of identifying and testing treatment methods <br />for all required constituents, followed by engineering, permitting and construction. In addition, <br />active treatment of mine pool water would require management of large amounts of <br />contaminated sludges at the active surface environment which itself would introduce new <br />potential threats to human health and water quality in the creek. <br />With respect to addressing any downstream impacts that could occur due to potential conduits <br />along the Schwartz Trend or elsewhere, temporary dewatering /active treatment would not <br />address Criterion 1. This is because such migration could take decades to centuries to manifest, <br />if at all (Cain et al., 2011). Under a reversed hydraulic gradient mitigation strategy, only long- <br />term dewatering could realistically address this concern. The concept of a reversed hydraulic <br />gradient to a depth of 500 feet below the Steve Level rates poorly under both Criterion 1 <br />(effectiveness) and Criterion 2 (sustainability). <br />Another important consideration for mine dewatering /active treatment is the fact that this <br />strategy would create problems or impediments with respect to other remedial measures that will <br />be necessary for overall reclamation of the mine site, including long -term management of mine <br />water, remediation of solid source term materials in the alluvial fill, and investigation and <br />mitigation of any impacts related to the waste rock piles. In essence, mine dewatering /active <br />treatment would undermine overall efforts to fully remediate the site with long -term mitigation <br />strategies. <br />For example, drawing down the mine pool could inhibit or eliminate the ability to identify any <br />potential conduits for seepage from the mine pool into the alluvial fill through core holes or <br />faults /fractures, and would thus undermine the opportunity to permanently grout /seal such <br />migration pathways. Furthermore, expansion of water treatment facilities and construction of <br />retention ponds (estimated to be approximately 7 acres which would cover the entire site) could <br />only happen after solid source term materials in the alluvial fill have been removed. Otherwise, <br />impacts to water quality in Ralston Creek from this source would continue despite mine <br />dewatering and active treatment of mine pool water. Either of these circumstances would cause <br />significant or even major delays in permanently attaining water quality standards in Ralston <br />Creek (Criterion 1). <br />4 <br />