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Whetstone' <br />Associates <br />Technical Memorandum <br />alternative for long-term sustainable mitigation of groundwater in the alluvium and fill at the site, <br />which is currently focused on source term removal. <br />The text of Section 15 of the EPP has been substantially revised to describe the short-term pump and <br />treat measures and the approach to long-term sustainable mitigation measures. Although the <br />preferred alternative for long-term sustainable mitigation is currently focused on targeted source <br />term removal from the alluvium and fill, data from the short-term interim water treatment measures <br />will be closely evaluated with respect this strategy as well as any additional reclamation strategy(s) <br />that may be necessary to consider. A plugging and abandonment (P&A) study is also currently <br />planned as part of source term removal efforts. If water quality in Ralston Creek exceeds the <br />uranium drinking water standard of 30 µg/L after the completion of targeted source removal and <br />selected P&A measures, the Operator will work with DRMS to identify additional long-term <br />sustainable mitigation measures to address impacts to Ralston Creek. Such mitigation measures <br />could include a permeable reactive barrier, engineered wetlands, or other measures. <br />19) Regarding the proposed wetland, the process flow scheme is not clear. Is the wetland designed <br />to capture only alluvial ground water, and thus mine pool water would not be routed to the facility? <br />The wetland would be designed to capture groundwater in the alluvium and fill. As currently <br />conceived, mine pool water would not be directly routed to the wetland. To the extent that any water <br />from the mine pool is entering the alluvium and fill, that water would be collected and treated in the <br />wetland, if the wetland alternative were to be selected. <br />20) The literature suggests that proper design of a wetland is best preceded by laboratory, bench <br />scale, and pilot testing. Please provide a description of an appropriate testing program that will <br />evaluate the capability of the proposed substrate to remove the contaminants of concern at the site. <br />Since the last version of the EPP was submitted (on 4/19/10), the Operator has continued to seek <br />additional professional opinions from experts in constructed wetlands, including those from Dr. <br />Ronald Cohen, a professor of environmental science and engineering at Colorado School of Mines. <br />Dr. Cohen has extensive direct experience designing and testing wetlands remediation systems <br />specifically for the mitigation of uranium in groundwater. Should laboratory, bench scale, and pilot <br />testing become necessary as part of a selected wetland option, experts such as Dr. Cohen along with <br />groundwater engineers and other consultants as appropriate would be used to perform all requisite <br />preliminary feasibility work. <br />21) On page 15-4, Operator states that "monitoring would be performed for up to 10 years to <br />demonstrate that the wetlands are functioning as designed... " DRMS does not accept the premise <br />that any passive treatment technology could be zero-maintenance. Please provide a plan for long- <br />term maintenance and bonding of the facility as needed. <br />The 4/19/10 EPP did not assert that any long-term treatment system would be maintenance-free. <br />Nearly all passive treatments systems require maintenance, and long-term maintenance requirements <br />were considered in identifying the two treatment alternatives presented in the 4/19/2010 EPP. <br />4109C.100731 9