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• <br />Memo to Steve Renner - 3 - January 4, 1989 <br />D.7.4,2 - Process Solution Ponds <br />10. The design parameters for sizing the pond capacity as stated are <br />appropriate. The components and corresponding volumes are itemized on <br />page D-40. A comparison to the water balance simulation provided in <br />Appendix G, however, shows the 52 acre-feet capacity to be exceeded at <br />times by the combination of draindown (ranges 24-28 ac-ft) and 100-year <br />storm (ranges 29-41 ac-ft ). In order to support the design principal for <br />containment, please submit either a revised pond capacity volume or model <br />documentation which indicates sufficient pond capacity will ire provided. <br />11, Considering no emergency pond has been provided in the design, and that <br />the pond will be constructed as an embankment with 20-foot depth, further <br />documentation on pond stability should be submitted. No technical <br />specifications on pond construction are provided in Appendix N. What <br />materials, construction techniques, compaction and compaction testing <br />will be used to construct the ponds? Based on the design parameters <br />chosen, will the embankments be stable under the slope and piezometric <br />head conditions expected? Please provide all documentation used to <br />support the conclusion from the pond stability analysis. <br />D.8 -Project Water Balance <br />12. How was the rate of draindown {10 gallons/ton ore} determined? Were the <br />column leach tests used to derive this parameter value? <br />13. A review of the report used to obtain the 100-year, 24-hour precipitation <br />value of 2.9 inches confirmed this value as appropriate. However, in <br />Exhibit G a value of 3.2 inches was used. How Can this incon;:istency be <br />explained? <br />14. In the water balance model output, a draindown of 2 acre-feet from the <br />deactivated part of the heap is shown. What pad area, ore volume and <br />denaturation rate corresponds to this draindown volume? <br />15. At the time of detoxification and decommissioning of the heap, it appears <br />only the solution volume contained in circulation from the final stage of <br />700,000 tons is available for use in rinsing the heap. As the entire <br />7,000,000 tons on the pad will need to be rinsed, what volume of water <br />will 6e required, where will this come from and what amount of time will <br />be required to rinse the entire heap? Will the ponds provide sufficient <br />storage capacity at this condition? Where are these volumes sown in the <br />water balance calculation in Appendix G? <br />16. Can the evaporation volume required near shutdown be accomplished in the <br />two month time period as shown on the model output in Appendix G? <br />