A juvenile bypass system orifice at Little Goose Lock and Dam became plugged early yesterday because of abnormally high seasonal debris from the lower Snake River, according to U.S. Army Corps of Engineers officials. The inadvertent orifice plugging caused an estimated 2,240 juvenile salmon and steelhead to perish. Millions of juvenile fish migrate downstream this time of year at Little Goose.
The plugged orifice was discovered at about 7 a.m. yesterday morning, May 3. During the current prime season for juvenile fish migration, the Corps periodically checks the juvenile bypass system on a 24-hour-a-day basis, including orifice inspections, for operational compliance.
Once the problem was discovered, the orifice was immediately backflushed to remove debris, and fish resumed their passage downstream.
The juvenile bypass system routes juvenile fish around the dam for sampling, barging or release back into the river. Little Goose Dam’s juvenile bypass system contains 36 orifices designed to attract juvenile fish out of a collection channel with lights. Juvenile fish then enter the bypass channel, swim into the bypass pipe, and travel to either the Juvenile Fish Facility or back to the river.
To help prevent future similar incidents, the Corps will monitor the orifices every two hours, 24 hours per day, to keep them free of debris.
Snake River flows have been very high this year due to heavy precipitation and runoff. Corps’ dams on the lower Snake River have seen higher-than-normal river debris come through the area.
