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• Pond embankments, slopes, spillways and construction methods have been designed according <br />to such engineering factor as structural integrity and ability, slope and surface stability, <br />adequacy in height, size and shape to provide sufficient volume for sediment and detained water <br />and selection of proper spillways and outlet devices, passing of design storm events and proper <br />outflow rates. <br />The purpose of the sedimentation ponds is not only to provide a final measure to prevent <br />additional contributions of sediment outside the permit area, but also to provide a means of <br />compliance with all applicable effluent limitations, especially with respect to total suspended <br />solids. The effluent quality is regulated by Section 4.05.2 and by the Chimney Rock Mine's <br />National Pollutant Discharge Eliminations System (NPDES) Permit (Exhibit 8.) <br />The engineering design parazneters incorporated into the consttuction of the sedimentation <br />control structures are described in Exhibit 7, Sediment Control Design Criteria. Other <br />engineering design parameters for the various interceptor ditches, riprap, and terraces are also <br />depicted in E.~dtibit 7, Sediment Control Design Criteria. No permanent impoundments aze <br />planned for the site. <br />Three small area exemptions (SAE) have been approved on the mine site as depicted on the <br />Drainage Control Map (Map 8). These areas include the reclaimed explosive storage area (as <br />approved in Minor Revision Number 35) the AVF area below Pond 002 (as approved in <br />Technical Revision Number 20) and the Pond 005 sediment cleanings (as approved in Technical <br />Revision 27). Facility design information associated with the sediment trap and the Pond 005 <br />• sediment cleanings (TR-27) approved in TR-20 is contained in Exhibit 7. <br />The Stollsteimer Creek crossing culvert is a temporary structure and is planned to be removed <br />during reclamation activities proposed for the fall of 1991. <br />Topsoil (Removal and Storaa~e <br />Drainage Control Map (Map 8) depicts the locations and volumes of soil stockpiles. Kaiser <br />proposes to limit the amounts of topsoil to be replaced in order to insure placement of soil over <br />the entire area disturbed as a result of mining operations. Placement of approximately 6 inches <br />of soil over the entire mined area was found to be acceptable. Topsoil stockpile locations <br />include the following: <br />Stockpile A - 10,000 cubic yards <br />Stockpile A will be retained for reclamation of the sediment ponds. All other stockpiles have <br />been utilized for reclamation of the surface facilities and Revision 1 mined areas during the fall <br />of 1991. <br /> <br />2.05-3 <br />