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ARCADIS <br />After the first 2 years of treatment, the frequency and amount of treatment that will be needed to maintain <br />uranium concentrations at or below the 90 percent reduction goal will be assessed. The Reclamation Plan <br />includes costs to conduct the initial treatment (2 years) and maintain the mine pool via in -situ treatment <br />over another 2 years. <br />Data Adequacy: The Reclamation Plan should address the pathways that affect the mine pool elevation <br />in the long term. The most appropriate action is to pump down the mine pool that will lower the driving <br />head for mine pool water to discharge into the alluvium. The Reclamation Plan should detail the long -term <br />maintenance activities to be conducted and should establish performance criteria that define conditions to <br />be met before in -situ treatment maintenance activities are terminated. <br />Recommendations: As previously recommended, Cotter should develop a conceptual site model that <br />includes details of the pathways that affect the mine pool elevation. <br />6.0 WATER QUALITY MONITORING PLAN <br />Overview: Seven new bedrock wells are planned to be installed at the site to improve the hydrogeologic <br />characterization and understanding of nature and extent of contamination. Two bedrock wells will replace <br />wells MW -10 and MW -11 to better evaluate background groundwater quality in mineralized bedrock near <br />the mine. As described in the EPP review, that the existing background wells are compromised, and their <br />water quality data are suspect. Two bedrock wells will be installed east of the mine area near the <br />downgradient boundary. Another two bedrock wells will target the Illinois fault zone, which was identified <br />in the EPP review as a possible conduit from the mine pool to the alluvium and the creek. One alluvial well <br />will be installed at the toe of the South Waste Rock Pile to assess potential impacts of waste rock leachate <br />on the alluvial groundwater. <br />Data Adequacy: The additional wells proposed by Cotter should be sufficient to address data deficiencies <br />and will result in a more defensible conceptual site model. Long -term monitoring of mine pool should be <br />conducted following the sampling and analysis schedule provided in the Reclamation Plan for SW -ADL <br />and SW -BPL (weekly dissolved uranium and field parameters, and monthly extended suite analysis with <br />additional analyses suggested for the small -scale treatment phase). <br />Recommendations: Proceed with the water quality monitoring program detailed in the Reclamation Plan <br />with long -term monitoring of the mine pool water quality. The duration and extent of the monitoring <br />program should be based on meeting established performance criteria. Cotter should also consider <br />installing the monitoring well into the alluvium beneath the South Waste Rock Pile to characterize the <br />groundwater quality underneath (see Section 4.2 -Waste Rock Piles). <br />7.0 REFERENCES AND INFORMATION CONSIDERED <br />Page: <br />15/16 <br />