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S 'Z <br />SMITH WILLIAMS CONSULTANTS, INC. <br />~• <br />The Phase 5 VLF design also includes closure underdrains. The purpose of the closure <br />underdrains are to provide a means to drain accumulated precipitation water from the VLF at and <br />during the post closure period (after the ore heap has been rinsed), to prevent overtopping of the <br />PSSA embankment. The closure underdrains consist of a blanket drains that are located beneath <br />the PSSA. During the post closure period, the blanket drains beneath the PSSA will be used to <br />convey accumulated water within the PSSA into the Phase IV VLF and the diatreme (see <br />Drawing A355). Each blanket drain consists of a 3-foot-thick layer of drainage gravel <br />(underdrain fill) enclosed in a geotextile. During the closure period, after the target <br />concentrations have been met in the VLF and the PSSA water level has been reduced to a <br />maximum level of 8 feet, the PSSA liner system will be punctured by drilling borehole through <br />the PSSA and into the blanket drains. This will facilitate long-term drainage of the PSSA. <br />4.12 Technical Specifications <br />Technical specifications for the Phase 5 VLF are provided. in Appendix H. The specifications <br />are based on the currently approved specifications by the DBMS in connection with Amendment <br />Nos. 6, 7, and 8 (CC&V, 1993, 1998, 2000). <br />C7 <br />• <br />S:\PROJECTS\1125 CC&V PHASE 5 VLF\H2 - DESIGMAREQUA VLF\VLF PHASE 5 FINAL REPORT V2.DOC 2p <br />