Draft Environmental Assesment and Finding of No Significant Impact Gunnision River Activities February 1995

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CHAPTER 2 - PROPOSED ACTIONS AND ALTERNATIVES Proposed Actions Two actions are proposed. One is to construct a fish passageway around the east side (right abutment) of the Redlands Diversion Dam. The other is to provide water when needed from the Aspinall Unit under an interim (temporary) water agreement as needed to operate the fish passageway and maintain downstream flows. Flows required to operate the passageway would either be released from water stored in the Aspinall Unit or consist of natural Gunnison River flows in excess of the needs of the senior downstream Gunnison River Basin water rights, including the Redlands Diversion Dam and the city of Grand Junction. Fish Passageway Design The proposed concept for the fish passageway is a concrete chute, 6 -feet wide and 350 -feet long, routed around the Redlands Diversion Dam and the city of Grand Junction's pump station located on the right bank of the river (Figure 1). The chute will be divided into a series of small pools by baffles; the water flow through the chute will be approximately 25 cfs. The upstream entrance to the fish passage will have a log boom and trash rack to prevent debris from entering. There will be a forebay (widened section of fish passage) near the upper end that allows fish to be trapped and separated before they move upstream into the river. Non- native fish will be returned to the river downstream from the diversion dam. Successful use of a passageway by razorback suckers and Colorado squawfish is currently undocumented; and water flow velocities, barriers, and attraction to the fish passage entrance may control whether passage is successful. Therefore, the passageway will be designed to incorporate measures for added flexibility in controlling water velocities and entrance conditions. The design will allow for variation in baffle spacing, pool length, height of water drop between pools, and water flow rates in order to test various conditions. Monitoring performance of the passageway and fish behavior under variations in the passageway will help determine the design parameters necessary for successful passage. This facility will serve as an example for future passageway facilities within the Colorado River Basin by helping develop specific design criteria for endangered fish. An existing sediment bar along the east bank of the river will be dredged as necessary at the upper end of the fish passageway to facilitate water movement. A 42 -inch bypass pipe will be constructed underground and adjacent to the chute. This bypass pipe will carry water (approximately 75 cfs) into the river below the Redlands Diversion Dam to attract fish to the passage structure and to maintain habitat downstream. A 12 -inch pipe will also parallel the fish passage to return non - native fish captured in the fish trap, thus preventing them from moving 5