2013-09-16_PERMIT FILE - C1982057A

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Design and as-built reports, when applicable, for the following sedimentation ponds are provided in this tab: I D Name Location Design (Tab 13) (As-Built) Sedimentation Structure 005 North II-W Attachment 13-3 TR-19lTR-59 Sedimentation Structure 006 (Phase II) II-W Attachment 13-4 TR-14 Sedimentation Structure 006 and Pre-Settling II-W Attachment 13-4C TR-29 Basin (Phase I~ (Design) Sedimentation Structure 006 (Phase ~ II-W Attachment 13-4E TR-48 Sedimentation Structure 009 North II-W Attachment 13-5 TR-17 Sedimentation Structure 015 II-W South Attachment 13-56 TR-35 Sedimentation Structure 016 II-W South Attachment 13-56 TR-381TR-40 Sedimentation Structure 017 II-W South Attachment 13-5B PR-04 Stock Tanks SCC constructs stock tanks in the reclaim areas at the Seneca operations. These small tanks will benefit both livestock grazing and wildlife utilization and will enhance the interim and final postmining land use of the reclaimed areas. The stock tanks slow the peak runoff from precipitation events and snowmelt and help to minimize erosion in the reclaimed areas. M Design and Construction. The stock tanks are small structures to enhance the postmine livestock and wildlife utilization. The capacity of these tanks is less than two acre-feet and the vertical height of the embankments is five feet or less, as measured from the upstream toe to the bottom of the emergency spillway. The drainage area for each tank is large enough to maintain an adequate supply of water into the tank. All stock tank locations are in drainages that are ephemeral -typically only flowing during spring snowmelt season or in response to low frequency summer thunderstorms. All stock tanks will meet the design criteria specified in Rule 4.05.9. All impoundments intended for retention as permanent postmining features shall comply with applicable State Engineer rules and regulations. Access to the tank sites, in reclaimed areas, during the construction phase will be along drainage bottoms or along temporary two-track roads to minimize damage to vegetation. If necessary, access routes will be reseeded with an approved seed mix. All topsoil will be salvaged prior to stock tank construction and spoil material will be used for construction of the embankments. After construction, topsoil will be replaced on the embankment and adjacent disturbed areas above the elevation of the emergency spillway. Each site will be seeded with the approved seed mix. There are eight (8) existing stock tanks at Seneca II-W: T-1, T-2, T-3, T-5, T-18, T-20, T-22, and T-24. Three additional stock tanks, T-25, T-26 and T-27, will be constructed in the sourthern final reclaimed mine area. The locations of the stock tanks, including T-25, T-26 and T-27, are shown on Exhibit 13-2 and 20-2, Postmining Topography and Drainage. Stock tanks T-1, T-2, T-3, T-22 and T-24 were constructed in 1991 and have been maintained in accordance with the methodology presented in this TR-59 9 Revised 05/07