2012-07-24_REVISION - M1977300 - Laserfiche WebLink

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ARCADIS The Reclamation Plan should discuss how the full -scale in -situ system will be optimized based upon the results of the small -scale test. Figure 2 of the Reclamation Plan indicates that there will be a decision point in the mine pool treatment plan to "Assess In -Situ Pilot Trial Results," and to either "Accept" or "Reject" the in -situ approach. The Reclamation Plan needs a more detailed description of how this pilot (presumably Action 3 above) will be conducted, what data will be gathered, and the criteria for accepting or rejecting the approach based upon the pilot results. Extending the duration of the pilot testing may also prove useful for designing the full -scale system. Parameters to be monitored during the small -scale testing include sulfate /sulfide, pH, oxidation - reduction potential (ORP), nitrate, ferrous /ferric, dissolved oxygen, and total organic carbon. Additional parameters should be added, including arsenic, manganese, and radium concentrations. These parameters should be monitored throughout the full -scale treatment. Finally, the proposed measure of long -term geochemical stability is to analyze for uranium. Although not specifically detailed in the Reclamation Plan, the success of the treatment approach during all phases of in -situ mine pool treatment would be better understood by subjecting samples to analysis for the extended water quality suite described above. Recommendations: Recommendations related to bench -scale and pilot -scale testing include: • Conduct bench -scale testing prior to implementation of the small -scale and full -scale treatment. The additional time and expense invested in bench -scale testing will help Cotter to better understand the system conditions prior to full -scale testing, which will likely reduce the Tong -term treatment costs. • A more detailed description of the small -scale testing and the criteria for accepting or rejecting the approach should be included in the Reclamation Plan. • Establish more clearly defined benchmarks to guide the decision making process throughout each stage of the in -situ treatment. • Engage stakeholders in the process, particularly at key decision making points (e.g., completion of bench -scale testing, completion of pilot -scale testing, following the initial full -scale treatment, once stable long -term conditions have been achieved). • The long -term monitoring program should include sampling and analysis of the mine pool water quality (as discussed in Section 6.0 -Water Quality Monitoring Plan). Bench testing will provide a basis for the design of the in -situ mine pool treatment trial. In a properly controlled experiment, the testing can also help determine to what degree the RO concentrate may be inhibiting to the treatment process. Given the nature of the mine pool, a complete understanding of byproduct release/ secondary water quality effects may not be achieved from a bench test, however testing will help to determine at what level these effects may be anticipated. Conceptually, the testing would include collection of a limited volume of mine pool water and mine rock, and in a microcosm test, combination of the water /rock and addition of organic carbon. Some treatments Page. 13/16