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site remediation activities have been completed, it cannot be assigned a perfect rating under <br />Criterion 1. Nevertheless, it is also critical to attaining permanent protection of water quality in <br />the creek through other measures and this factor was thus also considered in the overall rating. <br />With respect to sustainability, pipeline diversion rates highly under Criterion 2 because although <br />costly to implement, it provides complete temporary protection and will not create any long -term <br />burdens to future generations. Once all long -term remedial measures have been completed, the <br />pipeline will be dismantled and Ralston Creek will be restored in accordance with the <br />requirements of applicable regulatory agencies and respective permitting provisions. <br />Even though the pipeline diversion will temporarily provide the highest possible level of <br />protection of water quality in Ralston Creek, it will not significantly reduce associated health <br />risks for reasons previously discussed. Exposure pathways that could present potential risks to <br />human health are largely prevented by other incidental factors, regardless of the degree of <br />reduction of uranium concentrations in the creek. However, pipeline diversion will temporarily <br />involve potential secondary/peripheral health risks to the public during construction and final <br />dismantling as materials and equipment will be transported to and from the site through <br />populated areas. Potential physical risks associated with possible industrial or traffic accidents <br />during these periods will be present, though temporary. Pipeline diversion rates slightly better <br />than mine dewatering /active treatment under Criterion 3. <br />Pipeline diversion will likely involve temporary environmental disruptions and potential impacts <br />as the pipeline will be constructed above ground on the north side of the creek and the current <br />creek channel will be modest. However, many regulatory agencies will be involved in <br />permitting and multiple layers of both short- and long -term protections will be incorporated into <br />the overall diversion plan including a design that minimizes disruption of wildlife, preservation <br />and restoration of riparian and wetlands areas, and a detailed dismantling and general <br />environmental restoration plan. Pipeline diversion rates moderately under Criterion 4. <br />Considering the preceding conceptual assessments of pipeline diversion with respect to the four <br />remedial Criteria, individual Criterion ratings for this remedial alternative have been <br />conservatively estimated as follows: <br />Criterion <br />1. Effectiveness = <br />2. Sustainability = <br />3. Health Risks = <br />4. Environmental Impacts = <br />Rating (and summary rationale) <br />9 (complete & immediate mitigation, though short term) <br />8 (reasonable cost effectiveness, no long -term O &M) <br />3 (slight increase in health risks due to the method itself) <br />5 (temporary impacts expected, restoration required) <br />Grouting /Sealing of Potential Conduits for Mine Pool Migration <br />DRMS has found that historic exploration core holes and natural faults /fractures may serve as <br />potential conduits through which mine pool water could migrate to the Ralston Creek. A <br />fundamental assumption underlying the remedial alternative of grouting /sealing potential <br />conduits for mine pool migration, such as historic exploratory core holes or faults /fractures in <br />bedrock, is that a flooded state within the mine is the only realistically sustainable option for <br />long -term management of mine water within the underground workings. Under this assumption, <br />9 <br />