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