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Mr. Gregg Squire • • Page 3 December 20, 2000 A barrier is proposed on the discharge or lower end of the renewable resource area to keep water out of the area during mining and to control the flow out of the area during runoff. The design concept is to use the width of the opening in the bank as the bottom width of the weir. The bottom of the weir would have a 4% slope with the beginning elevation being high enough to keep water out of the pits during mining. The flow capacity of this weir is shown on the attached printout from Haestad Methods Flow Master. The details are shown on Exhibits C-3, C-4, CS-1, and CS-2. The estimated flow going through the overflow channel is will be provided at a later date. The barriers will be located by surveying in the corners using the coordinates provided on Exhibits C-3 and C-4. The erosion protection area will be inspected annually during the low flow period and repaired as needed prior to the next high Flow season associated with runoff. Since the river is a dynamic system, channel alignments, flow depths, island configurations and other features are constantly changing. It is expected that the river will capture the renewable resource area one day because the runoff flows will be high enough to alter the channel. The 1982 topographic mapping used in the floodplain study shows a main channel of the river flowing through the proposed renewable resource area. The Colorado River experienced higher than normal flows during 1983 and 1984 that significantly altered the river channel alignment in the project area. The main channel began to flow north of the island that contains the heron rookery while the channel on the south side of the island became an overflow area. This overflow area is the proposed renewable resource area. Item 3 -Reclamation of the Renewable Resource Area if it is part of the main channel. If the Renewable Resource Area becomes part of the channel, then an inspection will be performed with DMG to see if the post-mining channel is functioning. The operator would stabilize the bank in areas that the inspection identifies as unstable and requiring stabilization. A site specific plan would be developed after the inspection based on the guidelines provided in the "In-Stream Aggregate Extraction and Reclamation Guidance Document". If no bank areas are identified as requiring stabilization, then there is no reclamation liability for the Renewable Resource Area. Item 4 -Reclamation of the Renewable Resource Area if it is not part of the main channel. If the Renewable Resource Area does not become part of the main river channel then this area will be reclaimed as a backflow area. The assumed water surface elevation of the backflow area is $333.00. The projected area of inflow is shown on Exhibits F-1 and F-2. The bank slopes will be left on a 3: I slope by the mining operation. After mining is completed and the renewable resource area is to be reclaimed, the 3:1 slopes left by mining will be prepared and seeded using the approved seed mix. It is expected that willows and cottonwoods will naturally invade the area thereby providing additional bank stabilization. See Cross Sections on Sheets CS-1 and CS-2 . After the reclaimed area has had flows through it, the 3:1 slopes will be inspected to see if additional stabilization is required beyond seeding with the approved seed mix. If any areas