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3. Health Risks 10 Assumed to be of paramount importance <br />4. Environmental Impacts 7 Assumed secondary relative to health risks <br />The weighting factor was multiplied by a qualitative numeric rating for each remedial criterion <br />and individual scores were then summed to enable semi - quantitative comparisons between <br />remedial alternatives. Rating values were based on the following qualitative assessment scheme: <br />Rating Description: No fit Low fit Fit Good fit Excellent fit <br />Rating Scale: 1 3 5 7 10 <br />Relevant information and assessments, rationale, and ratings for each criterion and remedial <br />alternative are presented in the following sections. <br />Mine Dewatering /Active Water Treatment <br />The Division has concerns that small amounts of mine pool water are seeping into the alluvial fill <br />and impacting water quality in the creek, and also that there are potential conduits for migration <br />of mine pool water to other locations downstream of the site (e.g. along the Schwartz Trend). <br />The Division acknowledged that no evidence exists for the migration of mine pool water along <br />downstream conduits, but believes that impacts to the creek will eventually occur in these areas <br />if the mine is not dewatered. The Division's concept behind mine dewatering is to reverse local <br />hydraulic gradients towards the mine pool. <br />The Division has also indicated that mine dewatering with active treatment of mine water is <br />considered a temporary measure until a long -term solution to the mine pool can be developed <br />and implemented. This suggests that the Division agrees with Cotter that mine dewatering is not <br />a realistic long -term strategy because it is not sustainable (Criterion 2). A potential long -term <br />strategy has not been identified or proposed by the Division, nor has the duration of "temporary" <br />or "short- term" been defined with respect to mine dewatering /active treatment. <br />The Federal Remediation Technologies Roundtable, a technical consortium of experts from the <br />U.S. Environmental Protection Agency (EPA), Department of the Interior, Department of <br />Defense (DOD), Department of Energy (DOE), and the National Aeronautics and Space <br />Administration (NASA) rate groundwater pump- and -treat technologies as "below average" for <br />evaluation categories pertaining to sustainability and effectiveness including: 1) treatment of <br />radionuclides in groundwater, 2) time to reach remedial objectives, 3) operation and maintenance <br />requirements, and 4) costs relative to other available remedial technologies (FRTR, 2008). <br />Quantitative effectiveness (Criterion 1) could be partially satisfied by a temporary mine <br />dewatering /active treatment strategy, however, groundwater travel times suggest that such a <br />strategy may not be immediately effective in protecting Ralston Creek from uranium currently <br />residing in bedrock and alluvial fill groundwater systems. A new study from the U.S. Geological <br />Survey (Cain et al., 2011) has modeled potential travel times for mine pool water to reach <br />Ralston Creek adjacent to the mine. Under the most conservative scenario modeled (which <br />assumes highest hydraulic conductivities and lowest porosities), travel times ranged from 0.3 to <br />111 years, with a mean travel time of 4 years and median travel time of 41 years. <br />3 <br />