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Mr. Gregg Squire • • Page 2 December 20, 2000 The operator intends on mining the Renewable Resource Area in two phases. The first phase is in the southern end of the area in the section of the overflow channel that receives the most flow and contains approximately 17.00 acres. If the river rechazges the initial mining area in sufficient quantity, then the phase 1 area will be extended into the phase 2 area to mine the remaining 6.53 acres on subsequent passes. The phases are shown on Figures C-l, C-2, C-3, C-4, F-l, and F-2. Item 2 -Renewable Resource Area barrier stabilization design. The renewable resource concept is effective if the river flow has the ability to enter an area where the velocity will slow with little or no impedance. Velocity can be controlled through ati area by creating a larger cross sectional area, providing a flow control device on the discharge end of the area, or both. Recognizing the need to prevent the main river channel from realigning into the renewable resource area during normal runoff events, it is proposed to stabilize the barrier for the upstream end of the Renewable Resource Area by either of the following methods, 1. creating a gradual slope to the pit bottom from the inside edge of the barrier or 2. mining up to the edge of the barrier and using armoring on the inside edge of the barrier. In alternative 1, mining would stop approximately 50 feet from the edge of the barrier and existing river bottom material would be graded from the inside edge of the barrier to a point 100 feet away from the barrier. The resulting slope would be approximately 6% which is relatively flat when compared to an 33% slope. The native material slope is used to provide a gradual transition to the pit bottom ttrereby lessening the erosive force of the water. See Exhibit CS-2. [f alternative 1 does not provide sufficient erosion protection during runoff flows, then the operator will install armoring along the inside edge of the 150 feet barrier. The armoring would be installed using the following riprap specification. Type VH Dw = 24„ Smaller Than Given Size B Wei ht Intermediate Rock Dimension inches 100 42 50-70 33 35-50 24 2-10 9 The inside slope of the barrier will be 3:1. The armoring will be extended along the full length of the barrier and anchored into the ground that will not be disturbed by mining on each end. The armoring will go from the top of the barrier to a depth that is three feet below the pit bottom. Pit run substrate will be used for bedding material. A geotextile fabric will be installed below the bedding material. Atypical section is shown in Exhibit CS-2. The proposed location of the armoring is shown on Exhibits C-3 and C-4.