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Dam Safety Issue Evaluation Studies

Construction crews built a road on Hills Creek Dam so Portland District could conduct field investigations, 2016.

Project background

The U.S. Army Corps of Engineers owns and operates a large portfolio of dams that provide a variety of critical benefits to society,including flood risk management, navigation, hydropower and recreation.  However, there are risks to life and property if a dam were to fail. The Corps monitors the condition and performance of these dams, using assessments and evaluations to provide information about the structures.


The Portland District, as part of its Dam Safety program, monitors the condition and performance of the structures owned and operated by the District. These structures are within the Columbia, Willamette and Rogue river basins, and are well-designed, well-constructed and are functioning as intended. There is no evidence to suggest an emergency situation exists, or is about to occur. 

Portland District's dam portfolio includes:

  • 19 dams
  • Mount St. Helens sediment retention structure
  • Five navigation locks
  • 13 hydropower plants

It is important that residents who live downstream from a dam are aware of the potential consequences should the dam breach, not perform as intended, or experience major spillway or outlet works flows. 

Issue Evaluation Studies

The Corps uses Issue Evaluation Studies to evaluate the condition and risks associated with its dams. These assessments provide data that will give the Corps additional information to better understand conditions within the dams and in their foundations, helping to evaluate risks and determine the degree of urgency for action within the context of the Corps’ national dam portfolio.

 An IES is completed in phases, which include:

  1. Data gathering phase: field investigation, regional hydrologic analysis, regional potential seismic hazard analysis, advanced structural analysis, etc.
  2. Evaluation phase: assessing the probability and consequence of ways the dam could fail
  3. Documentation/report writing phase
  4. Decision-making phase: do we need to more evaluations, do we need to implement interim risk reduction measures, and/or do we need to fix something?

The Portland District is performing field investigations at some of its dams as part of the Issue Evaluation Studies. During these field investigations the Corps will collect data that will be used to:

  • Better understand how dam materials perform under various conditions, including  normal operating conditions, large storm events, or seismic activity
  • Measure water levels and movements within the dam
  • Update information related to seismic activity

Field investigations

Locations and timeline:

Hills Creek Dam

November 2016 - June 2017

Cougar Dam

June 2017 - December 2017

Lookout Point Dam

Completed October 2016

 

The field investigation work varies by project, and includes:

  • Drilling bore holes and excavation of test pits
  • Detailed logging of geotechnical samples
  • Installing instrumentation in select areas to measure water levels and movements within the dam
  • Lab testing on the samples to improve understanding of how these materials perform under various conditions

Routine inspections and operation of the dams will continue as usual during these studies.

Additional information

Portland District’s highest priority is ensuring the Corps’ dams are fully able to reduce flood damage to downstream communities on the Willamette and Rogue rivers, and that the Columbia River dams continue to safely function as designed. The primary objective of the Corps' Dam Safety Program is to maintain public safety by making sure the dams it owns and operates are as safe as possible, and that risks to the public are minimized. Work performed as part of the Dam Safety Program includes:

  • Periodic inspections and assessments
  • Emergency Action Plan exercises
  • Seismic and hydrologic studies
  • Foundation drain inspections
  • Survey monitoring
  • Instrumentation monitoring
  • Bridge inspections
  • Hydraulic steel structures inspections and evaluations

People living below dams need to understand their level of risk and take preparedness actions. It is always a good time to prepare for an emergency. Contact your county offices for local emergency preparedness information. All Corps dams have emergency action plans which are maintained in coordination with local emergency management officials.