Corps Changes Classification Of Willamette Valley’s Green Peter Dam From High Risk To Low Risk

After years of extensive studies, a risk assessment and recent rehabilitation of spillway gates, Army Corps of Engineers officials have reclassified Green Peter Dam, near Sweet Home, Ore., as a low risk dam.

Recent rehabilitation of the spillway tainter gates for trunnion friction and overall reliability have improved the risk characterization.

These efforts along with a detailed review of the dam’s hazards, performance and consequences, helped decrease risks from the last assessment, which rated Green Peter as a high risk dam. 

“We’ve made a substantial amount of progress increasing the reliability of Green Peter Dam, which is critical to reducing flood risk to people living in Sweet Home, Lebanon and Albany,” said Ross Hiner, Portland District dam safety program manager. “Our Dam Safety team is pleased with the results of this study, but we have more work ahead of us to continue assessing risks associated with the other dams in the Willamette Valley.”

In July, officials reduced the risk classification of Green Peter on the Dam Safety Action Classification (DSAC) scale, which ranges from Very High to Very Low Risk. The Corps places dams into a risk classification based on life-safety risks associated with individual dams. The risk assessments consider a combination of the potential hazards (or loadings) the dam may be subjected to in the future, the probability of various failure modes (performance given those loadings), and the potential life safety, economic, environmental, or other consequences.

The Dam Safety Program’s goal is to make Corps dams as safe as possible and minimize risks to the public.

The Portland District Dam Safety team plans on completing the following actions to further manage risk associated with Green Peter Dam:

•           Updating the dam’s Emergency Action Plan

•           Increasing monitoring

•           Improving communication infrastructure

•           Improving physical conditions of the dam

The actions are all a part of routine operations, maintenance and dam safety activities.

The studies are part of the Corps’ national Dam Safety Program, which includes periodic inspections, monitoring of dam performance, risk assessments, Emergency Action Plan exercises and engineering evaluations.

Green Peter Dam is located on the Middle Santiam River near Sweet Home, Oregon. The Corps operates Green Peter Dam and 12 other dams and reservoirs in the Willamette River Basin. All contribute to a water resource management system that provides flood risk management, power generation, irrigation, water quality improvement, fish and wildlife habitat and recreation on the Willamette River and many of its tributaries. Since their completion, the dams have cumulatively prevented more than $20 billion in flood damages to the Willamette Valley.

— CBB, Feb. 6, 2020, PORTLAND DISTRICT CORPS STUDIES VULNERABILITY OF DAMS TO CASCADIA EARTHQUAKE; EXPECTS LITTLE DAMAGE, SOME ‘DEFORMATIONS’ https://www.cbbulletin.com/portland-district-corps-studies-vulnerability-of-dams-to-cascadia-earthquake-expects-little-damage-some-deformations/

— CBB, Feb. 27, 2020, CONCERNED ABOUT EARTHQUAKES, CORPS CALLS FOR LESS FILL IN RESERVOIRS BEHIND TWO WILLAMETTE VALLEY DAMS https://www.cbbulletin.com/concerned-about-earthquakes-corps-calls-for-less-fill-in-reservoirs-behind-two-willamette-valley-dams/

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