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001091 Final Environmental Assessment-Chapter 3-Affected Environment and Environmental Consequences Downstream hazards (i.e. bridge abutments, check structures) would continue to exist but could be signed to notify boaters of the approaching hazards. In conjunction with dam removal, one of the mitigation measure options for protecting the ability of Ute Water to pump from the Colorado River (see Page 19) would be implemented. Option 1 and 2 would have no effect on recreation. However, designs for option 3, which involves constructing a low head dam immediately downstream from the pump plant, would consider boater safety. Land and Facility Resources During construction of any of the construction alternatives, an increase in noise and traffic would occur. To date, Reclamation has not been advised of concerns for disturbances during construction. Any complaints would be resolved on a case-by-case basis. The Colorado Department of Transportation has advised Reclamation that access to the site from Interstate 70 would not be granted. Protecting Existing Structures The fish passage project could affect four existing structures in the project area; 1) the Union Pacific Railroad on the right bank of the river, 2) the Interstate 70 Highway on the left bank, 3) the Ute Water pump plant, and 4) the Colorado River Siphon located about 3,600 feet upstream from the dam. The Interstate, railroad, and siphon were built considering river flow and stream bank conditions that existed with the dam in place. Reclamation constructed the siphon, which is a pipeline under the riverbed of the Colorado River that carries water from the Government Highline Canal to the Orchard Mesa Power Canal. Two factors could affect these structures: 1) scouring of the riverbed and banks, and 2) the rate of wetting or dewatering the foundations of the railroad and Interstate 70. River scour is a function of water velocities, the size of the cobbles in the riverbed, and the size ofthe riprap along the banks. If the dam is removed, the velocities of the water in the river would increase in the vicinity of the dam. As the velocity increases, the ability of the water to scour the banks and riverbed increases. If the banks and streambed are not adequately protected, the scour could move horizontally toward the railroad and Interstate 70. If the dam is not removed correctly, riverbed scour could extend upstream and could expose and damage the siphon. Wetting (saturation of) the foundations of the railroad and Interstate 70 would weaken the foundations. If actions taken at the site raise the existing water levels, there could be impact to these structures. Since the siphon is buried beneath the riverbed, foundation wetting is not a concern. 38