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Lower Monumental Dam Crossings Close
Until May 30 During Repairs

Walla Walla Union-Bulletin, May 1, 2022

Water runs through spillway gates of Lower Monumental Dam on the Lower Snake River in southeastern Washington. Increased spills benefit salmon. Public crossings over Lower Monumental Dam will be closed until May 30 after a safety issue was discovered.

Several spillway trunnions creating too much friction were named as the culprits.

Trunnions are pivots that allow the spillway gates to open and close, an integral component of the safe operation of a dam. If too much friction exists, it puts extra stress on the gate when it is moved, potentially leading to a failure of the spillway gate.

When it was discovered that the trunnion of one of the spillway gates had too much friction, an inspection was ordered for the remaining seven gates at Lower Monumental Dam, four of which were found to be experiencing a similar issue.

Engineers and maintenance crews have developed a remedy by drilling grease ports on the trunnions, the U.S. Army Corps of Engineers Walla Walla District wrote in a release. These ports will allow crews to grease internal bearings that were originally designed to be unlubricated.

This work is projected to be completed by May 30, and the dam crossing will be closed in the interim. While the work is ongoing, Lower Monumental will adjust spill operations for fish passage and use the remaining spillway gates to safely pass juvenile salmon.

Due to the cold start to the spring, very few fish are migrating at this time, providing the opportunity to perform the required maintenance on the gates with minimal impacts to fish, according to the release.

Public dam crossings are currently available at Lower Granite Lock and Dam and Little Goose Lock and Dam.

Related Pages:
Little Goose Dam Extends Public Dam Crossing Closure to April 22 due to Electrical Maintenance by USACE, Big Country News, 4/18/22
Little Goose Dam to Close Public Dam Crossing from April 4 - 8 to Perform Maintenance by USACE, Big Country News, 3/21/22
Little Goose Dam Closes Public Dam Crossing due to Inclement Weather by by USACE, Big Country News, 1/4/22
Temporary Closure of Little Goose Dam Scheduled for Maintenance Work by USACE, Big Country News, 7/28/21
U.S. Seeks Transformer for 810-MW Little Goose Hydro Project by Staff, Hydroworld, 4/2/15
Little Goose Dam Closed to Water Traffic by Greg Craber, Daily Fly, 9/5/18
Little Goose Dam to Have Intermittent Crossing Closures by Staff, Walla Walla Union-Bulletin, 6/4/18
Little Goose Lock Reopening Delayed Until April 11 by Matthew Weaver, Capital Press, 3/30/17

Lower Monumental Dam Crossings Close Until May 30 During Repairs
Walla Walla Union-Bulletin, May 1, 2022

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