2008-04-15_REVISION - M1980244 (256)

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~,_ 1 SMITH WILLIAMS CONSULTANTS, INC. • Surface water collected alon the north end of the VLF will be routed to a sedimentation and g p as shown on Drawing A510. The sedimentation pond is designed to fully contain twice the run- - off from the 10-year, 24-hour storm event falling on the upstream watershed (see Drawing A500). The sedimentation pond is designed to be unlined to allow infiltration of water. The pond design includes a riser so that water can be pumped from the pond into the Phase IV PSSA, as needed. Design and pond sizing calculations are presented in Appendix F. Surface water collected along the south end of the VLF will be routed onto an existing bench. Since this water does not contact any mine-impacted surfaces, no sedimentation pond will be required and the water will be routed to the environment. The engineering designs contained in this document provide a detailed description of the project features associated with the Phase 5 VLF extension. In instances where the submittal of further information is warranted, Smith Williams understands that CC&V will provide IFC drawings and appropriate supporting documentation (e.g., calculations, narrative explanations, etc.) to the DBMS containing design details and changes that are based on site-specific conditions and constraints. Comparable to Amendment No. 8 activities, submittal of the IFC drawings and any • supporting information is not expected to require new approvals but is intended solely to ensure that the DBMS is aware of the phased implementation of the proposed activities. 5.6 Construction Sediment Control Sediment control during Phase 5 VLF construction activities will be the responsibility of the general contractor hired by CC&V. Typical sediment control features are presented on Drawing A270. • S:\PROJECTS\1125 CCBV PHASE 5 VLF\H2 - DESIGNWREQUA VLF\VLF PHASE 5 FINAL REPORT V2.DOC 40