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Improved Fish Passage at Little Goose Dam by Staff BPA Journal, March 2009

The U.S. Army Corps of Engineers installed a fish- friendly spillway weir at Little Goose Dam on the Snake River in Washington last month. With this new structure in place, all eight federal dams on the lower Snake and Columbia rivers have "fish slides" or other devices to get juvenile fish safely past the dam as they migrate to the ocean.

Northwest contractor Advanced American Construction built the nearly 150-ton structure under a $2 million contract with the Corps. The Corps funds these improvements to the federal dams through the Columbia River Fish Mitigation Fund, which is appropriated by Congress. BPA reimburses the U.S. Treasury for these appropriations and helps the Corps and regional stakeholders identify annual funding priorities for the proposed improvements.

The weir fits inside a dam's spillway, allowing juvenile fish to pass near the surface of the water rather than diving some 50 to 60 feet to pass through the traditional spillway opening in a typical dam. This is a more efficient and less stressful passage route for the fish and it reduces delays in the forebay of the dam. Under a separate $3.2 million contract, AAC also installed spillway deflectors in two bays at Little Goose Dam. The deflectors help direct fish departing the spillway to move more quickly toward the river and help reduce the dissolved gasses that are created by spilling water.