2011-03-22_PERMIT FILE - C1981033A

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2.05.3(4) Sedimentation pond and diversion ditch removal are discussed in Section 2.05.4. The location of the sedimentation pond and diversion structures are shown on the Sedimentation Control Plan, Exhibit 11-1. This exhibit also shows the location of the watershed boundaries from which, along with other sources, the design criteria was established. Generally, the pond and spillways were sized and constructed according to such hydrological factors as required sediment storage volume and the volume and rate of flow generated by the design storm event. The pond, spillways, and construction methods were designed according to such engineering factors as structural integrity, slope and surface stability. The pond was designed to have adequate height, size and shape to provide sufficient volume for sediment and retained water. Spillways and outlet devices were selected that would handle the design storm events and provide sufficient outflow rates. The pond was designed under the direction of a qualified, registered professional engineer. • The purpose of the sedimentation pond is not only to provide a final measure to prevent additional contributions of sediment outside the permit area, but also to provide a means of compliance with all applicable effluent limitations, especially with respect to total suspended solids. The effluent quality is regulated by Rule 4.05.2, and by the National Pollutant Discharge Elimination System (NPDES) Permit. The NPDES Permit was issued by the State of Colorado, Department of Health under the National Pollutant Discharge Elimination System, established as a result of the Clean Water Act (33 U.S.C. Section 1251, et sea). A copy of the NPDES Permit is presented in Exhibit 4, Permits for Mining. The engineering parameters for the sedimentation pond and diversion ditches are included in Exhibit 11, Drainage and Sediment Control Plan. • 2.05-23 Rev. 11-09-93