USACE Portland District Spillway Gate Rehabilitation Program

Abstract

The U.S. Army Corps of Engineers (USACE) Portland District has 90 spillway radial Tainter gates. There are 42 gates at the 11 Willamette Valley Basin projects, 5 gates at the two Rogue Basin projects, and 43 gates at the two Columbia River projects. Since 2001, there have been various studies, inspections, and incidents that have prompted the Portland District to become concerned about the structural integrity and mechanical and electrical reliability of these gates. In 2008, load induced buckling was observed on three of the four Tainter gate end frames at Foster Dam, which led to emergency repairs. Additional observations of buckled Tainter gate strut arms at Dexter Dam in December 2009 required repairs and created urgency with respect to documenting the risk to the downstream population at all District projects. These events led to a comprehensive assessment of the Tainter gates in the Willamette Valley and Rogue Basin projects, which was implemented in 2010. The comprehensive assessment included a gates specific potential failure modes analysis (PFMA); structural, mechanical, and electrical assessments; identification of interim risk reduction measures (IRRMs); and analysis of impacts of the interim risk reduction measures. As part of this assessment, the District developed a tool for prioritizing projects for gate repair based on the results of the assessment. Since identifying the issues with Tainter gates, Portland District has implemented IRRMs, taken a systems-based approach to repairs, and implemented a capitalization program to improve gate reliability. Repairs are complete or underway at 36 of the 42 Tainter gates in the Willamette Valley. A study is underway to address reliability of regulating outlets, and future studies are planned for Columbia River spillway gates.