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• selected locations to reduce flow velocities in steeper portions of the channel and ensure stability. These <br />check dam locations will be field located during the channel re-construction activities. The SEDCAD4 <br />demonstration is located in Tab 13, Facilities; Attachment 13-12, Drainage and Sediment Control Plan. <br />In addition to re-constructing YPM-12, a sediment pond (Pond 011A) will be constructed at the upper end of <br />the channel (in a previously disturbed area) to provide a location for sediment retention and to serve as an <br />energy dissipater for runoff until vegetation is established in the channel. <br />In order to stabilize watersheds and associated post mine channels, runoff control structures may be <br />constructed. Snowmelt and sudden, intense summer thunderstorms produce runoff in excess of the normal <br />anticipated volumes. To stabilize the channels these extra-ordinary flows can be controlled with various <br />measures including runoff control structures built in the watersheds. These structures will be constructed <br />as needed to promote stabilization of the area and are located up-gradient of existing sediment ponds with <br />approved CDPS permits. Figure 20-2, Typical Runoff Control Structure, shows a generalized configuration <br />of the structures that could be placed along the postmining channels when problem areas are encountered. <br />These structures will be field located and constructed as needed and will not impound water. Attachment <br />20-2 contains the slope stability evaluation. <br />• Disturbance Area <br />The maximum extent of all areas anticipated to be disturbed by mining, facility, and access construction, <br />and all reclamation activities at Yoast have been identified and are entirely encompassed within the <br />disturbance boundary as depicted on Exhibit 12-1, Operations Plan. The extent of this boundary was <br />conservatively defined, and may include areas, particularly in the vicinity of roads and impoundments, that <br />will not be affected by any disturbance. An affected lands boundary map was not generated. The affected <br />lands could be considered the area between the disturbance boundary and the permit boundary. The area <br />within the mining disturbance boundary includes the area mined, the area upon which spoil is deposited <br />and graded, and where final highwalls have been reduced. <br />A total of 2,318.3 acres are contained within the Yoast permit boundary. Exhibit 12-1, Operations Plan, <br />depicts areas that could potentially be disturbed during the life-of-mine operations. The boundaries shown <br />on this map were drawn to allow some degree of flexibility in operations. That is, if a haulage road had to <br />be moved due to field adjustments, or a highwall reduction area required additional slope area, these <br />operations could be conducted without revisions to the permit. In actuality, haul road disturbance is <br />confined to a corridor approximately 100 feet to 200 feet wide. The permitted mine disturbance acreage of <br />1,019 acres reflects the shaded area as shown on Exhibit 12-1, Operations Plan, including the areas <br />• associated with the North Entrance Road. This area is conservatively overestimated for the reasons stated <br />above. <br />TR-43 11 Revised 9/09