Lower Snake River Juvenile Salmon Migration Feasibility Study
The Study
The Corps of Engineers, in response to the National Marine Fisheries Service 1995 Biological Opinion, Reinitiation of Consultation on 1994-1998 Operation of the Federal Columbia River Power System and Juvenile Transportation Program in 1995 and Future Years, is studying structural alternatives to improve the migration of juvenile salmon (listed under the Endangered Species Act) through the Lower Snake River Project.
Throughout the study process, we will define alternatives, provide a comprehensive evaluation, prepare a document for regional coordination, and prepare a document for Congressional authorization and appropriations.
The study includes engineering work; biological investigations (i.e., effects to salmon and steelhead, resident fish, and wildlife); effects on recreation, cultural resources, and water quality; and socioeconomic effects, including implementation costs, navigation, irrigation, and power. Also included is the development of an environmental impact statement and public involvement, both of which are essential to the National Environmental Policy Act process.
Study Objectives
The proposed alternatives include: 1) the existing condition; 2)maximum transport of juvenile salmon; 3) system improvements that could be accomplished without a drawdown; and 4) dam breaching.
Every FR/EIS has a starting point from which all other alternatives are measured. Alternative 1 is the baseline or no action alternative under which the Corps would continue operating the four lower Snake River dams according to their current configuration, including all fish passage programs now in operation. More than 50 percent of the fish would be transported via truck and barge, while the remainder would migrate in-river. This alternative does not mean that no further improvements would be made. The Corps, as part of its ongoing development plans and in response to changes in agency requirements, plans to improve technology at the dams to promote fish passage. The Corps' current plan calls for turbine improvements, structural modifications to fish facilities at Lower Granite Dam, new fish barges, adult fish attraction modifications, a new trash boom at Little Goose Dam, modifications to fish separators, added cylindrical dewatering screens, and more or improved spillway flow deflectors.
Most of the improvements planned for Alternative 1 would also be included in Alternative 2. The emphasis in this alternative, however, is on operating the existing facilities to maximize the passage of fish through the existing collectors into trucks or barges for transport downriver. Voluntary spill to bypass fish would be minimized. Fish would be collected in the existing facilities and transported past the dams. Under this alternative, there would be no need to modify spillway flow deflectors, because voluntary spill would be minimized. Some juvenile fish would still pass through the dam turbines.
This alternative, like Alternative 2, also maximizes transport of juveniles. It differs from Alternative 2 in that it incorporates a full-length surface bypass collector at Lower Granite Dam, which is the first dam juvenile fish encounter, thus the logical point to collect the fish. This new collection technology, in combination with existing bypass screens, would increase collection capability at Lower Granite Dam to 90 percent or higher and minimize the number of dams, bypass systems, and reservoirs that juvenile fish encounter. This bypass collector would span the powerhouse and work in conjunction with the existing extended submerged bar screens to divert fish from the turbines. At Lower Monumental and Ice Harbor, the existing submerged traveling screens would be replaced with bar screens to improve the collection or bypass of juvenile fish that originate from tributaries below Little Goose Dam.
This alternative consists of breaching the four dams and creating a free-flowing 140-mile stretch of river. This would involve removing the earthen embankment section of each dam and eliminating the reservoirs behind the dams. Under this alternative, all facilities for transporting fish would cease to operate. A free-flowing river can be achieved by removing only the embankment. The powerhouses, spillways, and navigation locks would not be removed, but would no longer be functional, eliminating power production and commercial navigation.