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Regional General Permit Notification for Grisenti Farms Gravel Pit Bank Stabilization Project Fremont County,Colorado Corps File No.RGP-37 by 24 inches and the thickness of the broken concrete would range from 4 to 12 inches. All exposed reinforcing material would be removed from the broken concrete prior to the proposed work. The bank protection would consist of placing the broken concrete in triangular wedges 6 feet wide with a 2:1 slope below the eroded banks. The concrete would be buried and native seed would be placed over the buried concrete. The proposed bank stabilization would result in an average of 0.66 cubic yard of fill per running foot being placed beneath the plane of the OHWM. In the area where the bank is eroded up to 15 feet,Transit Mix is proposing to lay back the banks to a 3:1 slope above the concrete bank stabilization and revegetate the upland slope with an appropriate native seed mix. The proposed bank stabilization would result in 0.056 acre of permanent stream channel impacts and 0.02 acre of permanent wetland impacts. Cross Vanes To direct flows to the center of the channel away from the eroded bank,Transit Mix is proposing to install four concrete vanes at 40-foot intervals along the stabilized banks of the Arkansas River. The cross vanes would consist of the same broken concrete material as the bank stabilization. The cross vanes would extend 12 to 20 feet into the channel and would gently slope downward so that during low flows,the vanes would be exposed and submerged during high flows. The concrete cross vanes would be 3 feet wide and would be installed at an angle of 30 degrees upstream perpendicular to the stream bank. Installation of the concrete cross vanes would permanently impact 0.004 acre of stream channel. Proposed Project Impacts Due to the nature of the project(bank stabilization),unavoidable impacts would occur along approximately 415 linear feet of stream channel,which includes 0.06 acre of streambed and 0.02 acre of wetlands(Figure 3;Table 2). No temporary impacts on waters of the U.S.are anticipated for the proposed activities. Construction equipment operators would make every effort to minimize disturbance limits,although minor shifts in the disturbance limits may be necessary to access the project area. Table 2.Summary of impacts on waters of the U.S.including wetlands. Permanent Impacts on Permanent Impacts on Temporary Impacts on Actnrrty Stream Channel(acre) Wetlands(acre) Waters of the U.S.(acre) 1.Bank 0.056 0.02 0.00 stabilization 2.Cross vanes 0.004 0 0.00 Total 0.060 0.02 0.00 E RO Project#7141 8 14