Spillway Gates

In 2010, dam safety climbing inspections of the Foster Dam spillway gates identified alarming structural damage to the Tainter gates.  The damage was a warning sign of potential overstressing of the gate strut arms due to increased trunnion friction.

Increased trunnion friction was the culprit at a failure of the Folsom Dam spillway gates in 1995.  Trunnion friction was not a mechanism well understood at the time of the original design of the dams and modern design guidance requires this to be considered. After careful analysis of the gates at Foster Dam and ​the others within Portland District, the need for major repairs was clear.  

Rapid repairs of the Foster dam gates included strengthening the gate structure as well as improving the trunnion materials to reduce the friction.  Since 2010, similar repairs have been made across the dams in the Willamette Valley.  The repairs have included structural strengthening of the gates, upgrades of the mechanical components, and electrical reliability improvements.  The spillway gate rehabilitation and reliability improvements have been completed at a majority of Willamette Valley dams, or are currently underway.  The table below provides an updated status as of January 2020. For more information, read an article about spillway gate repairs here.

For current and projected Willamette reservoir and river elevations and flows, visit our Water Management page or the Northwest River Forecast Center

Spillway gate repair status

Spillway gates issues

graphic showing structural problemsOur Dam Safety program has found that most of our dam’s spillway gates are aging and may not operate properly when water levels are high and placing significant pressure on the gates. This may result in a gate failing to open, or becoming stuck in the open position. Such failures could compromise our ability to manage water releases from that dam.

We assessed the gates in 2010, which resulted in the replacement or repair of critical components and development of a prioritized plan for long-term rehabilitation of the gates.  All of Green Peter, Foster, Big Cliff, Lookout Point, Dexter and Fall Creek dams' spillway gates have been strengthened.  Rehabilitation of Blue River and Hills Creek dams' gates are in progress and scheduled for completion in Fiscal Year 2018. The need for longer term gate rehabilitation work remains at four dams in the Willamette Valley.


For more information about the Willamette Valley dams’ gates, see: 

Reservoir teacup diagrams

Visit river basin “teacup” diagrams for real-time reservoir levels. Each project’s smaller “teacup” includes observed inflow, precipitation levels and its specific rule curve. The diagrams also show releases from dams for the past seven and 30 days: