Replacing 5000-lb (2268-kg) Trunnion Pins on a Giant Radial Spillway Gate

Tainter Gate 12 at Wanapum Dam had been out of service for 4 years, limiting the crucial ability to pass flows on one of the nation’s largest rivers. In early 2020, workers observed rotation of a trunnion pin indicating high friction. The gate was immediately placed in emergency-use-only status, but then repairs were delayed by COVID and competing priorities. 

When efforts were jump-started in 2023 with a new commitment to the FERC, we made it our goal to craft an exemplary project plan that got the task done and accommodated project risks. Planning required intensive historical research and reconnaissance of our spillway and stored equipment. 

Ultimately, the project was successfully completed within the allotted time window. Our on-going goal is to document the process, share it widely within and outside our organization, and better prepare ourselves and others for similar work in the future.