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• the center and includes a scour basin, energy dissipator, which transitions the flow to the <br />reconstructed arroyo. This approach will allow existing arroyos to be transitioned into the <br />reconstructed drainage at the upper end of the mined area. <br />If the drop height exceeds 10 feet, then an optional method to control flow down the <br />restored highwali is to construct a detention pond above the slope. The pond would reduce the <br />peak runoff rates for up to the 100-year event and allow the flow to be conveyed in a pipe with a <br />scour basin energy dissipator at the outlet. An example of how the pond could be configured is <br />provided on Figure 1 I. <br />Preserve and Restore Existing Stock Ponds. Existing stock ponds will be preserved or <br />reconstructed as part of reclamation. The existing stock pond in Arroyo "A" will be preserved <br />throughout the mining operation. Activities within Arroyo "A" watershed aze limited to <br />construction of the access road and the railroad spur with culverts, and some mining in a <br />relatively small area (that is, 24-acres) to the east of the arroyo drainage. Refer to Exhibit D-1 <br />and D-2 for more detail of the relationship between Arroyo "A" and the mining activities. <br />The existing stock pond in Arroyo "E" will be preserved through approximately yeaz 10, <br />after which mining will progress through the pond. The stock pond will be restored to its <br />existing capacity by excavation and a small embankment during reclamation. <br />• <br />SWMP BC June 28 2002.doc, 06/28/02 1 I <br />