THE US ARMY CORPS OF Engineers’ (USACE) final report on improving salmon passage through the lower Snake river dams is now available on the USACE website (

The feasibility report and environmental impact statement provides supporting documentation on USACE’s selection of major system improvements as the preferred alternative to decommissioning. This is now known as the adaptive migration alternative. Key factors in selecting the alternative include: •High juvenile and adult salmon survival rates through the lower Snake river dams.

•Flexibility in optimising survival in changing river conditions.

•Uncertainty in current biological information on the effects of alternatives.

Minimal economic impacts and compatibility with the National Marine Fisheries Service and US Fish and Wildlife Services 2000 Biological Opinions on operation of the Federal Columbia river power system were also a consideration, said Lonnie Mettler, project manager for the feasibility study.

‘Adapting the dams with various operational and structural configuration changes for improving fish passage better describes this alterative,’ added Mettler. ‘The survival of both juvenile and adult salmon passing through the lower Snake river hydro system is already high for a majority of flow years.’

Operational changes proposed include improving the coordination and implementation of spill, flow augmentation and juvenile fish transportation.

Structural changes include proposing spillway improvements, upgraded adult fish passage systems, upgraded juvenile fish facilities and additional fish transportation barges. Proposed long-term improvements include turbine upgrades, removable spillway weirs and surface bypass structures.