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selected locations to reduce flow velocities in steeper portions of the channel and ensure stability. <br />These check dam locations will be field located during the channel reconstruction activities. The SEDCAD <br />demonstration is located in Tab 13, Facilities, Attachment 13-12, Drainage and Sediment Control Plan. <br />In addition to reconstructing 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 <br />an energy dissipator for runoff until vegetation becomes reestablished in the channel. <br />In order to stabilize watersheds and associated postmine channel, 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 channel, these extraordinary flows can be controlled with various <br />measures including runoff control structures built in the wetlands. These structures will be constructed <br />as needed to promote stabilization of the area and would be located upgradient of existing sediment ponds <br />with approved CDPS permits. Figure 20-2, Typical Runoff Control Structures, shows a generalized <br />configuration of the structures that could be placed along the postmining channels when problem areas are <br />encountered. These structures will be field located and constructed as needed and will not impound water. <br />Attachment 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, <br />that will not be affected by any disturbance. An affected lands boundary map was not generated. The <br />affected lands could be considered the area between the disturbance boundary and the permit boundary. The <br />area within the mining disturbance boundary includes the area mined, the area upon which spoil is <br />deposited 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 <br />shown on this map were drawn to allow some degree of flexibility in operations. That is, if a haulage <br />road had to be moved due to field adjustments, or a highwall reduction area required additional slope <br />area, these operations could be conducted without revisions to the permit. In actuality, haul road <br />disturbance is confined to a corridor approximately 150 feet to 200 feet wide. The permitted mine <br />disturbance acreage of 1,018 acres reflects the shaded area as shown on Exhibit 12-1, Operations Plan, <br />including the areas associated with the North Entrance Road. This area is conservatively overestimated <br />for the reasons stated above. <br />TR -43 11 Revised 09/09 <br />