Dam Safety

Dear City of Carnation residents:

The normally scheduled Wednesday at noon alarm test of the Tolt Dam Warning System did not sound on January 13, 2021. Seattle Public Utilities (SPU) apologizes for any confusion or concern this might have caused.

The storm system from the previous night resulted in scattered power outages and SPU believes it affected the January 13 testing.

About an hour before the noon test was scheduled to occur on January 13, SPU began notifying our partner agencies, including the City of Carnation, about the possibility that the alarm would not sound.

We want to reassure you that dam safety monitoring was never interrupted, and SPU continues to monitor the dam 24/7 using various technology, including cameras and sensors installed along the Tolt Dam.

Thank you for your patience as our engineers continue to address the issue. If you have any questions or concerns, please contact our Dam Safety Supervisor Taryn Sass at (206) 850-9737 or Taryn.sass2@seattle.gov.

Program overview

SPU is dedicated to ensuring that all dams are designed, constructed, operated, and maintained with your utmost safety in mind. SPU continually inspects, evaluates, and documents the design, construction, operation, maintenance, rehabilitation, and emergency preparedness for each dam.

The mission of the SPU Dam Safety Program is to ensure safe operation of the dams and the Cedar Moraine embankment managed by SPU. The program goal is to:

  • Comply with strict federal and state regulatory requirements.
  • Inspect, monitor, maintain and operate the dams to minimize the chances of loss of water supply or flooding downstream, and prevent these conditions from developing if possible.
  • Respond to dam emergencies by using rehearsed emergency action plans and other tools.
  • Develop emergency action plans in partnership with other agencies.
  • Ensure that the Tolt Dam and Lake Youngs Dam Failure Warning Systems are being operated and maintained appropriately.
  • Plan and invest in state-of-the-art surveillance and monitoring equipment to ensure safe dam operations, which allows the City to respond to emergency conditions.

Dam monitoring and emergency action plans

SPU has comprehensive dam safety, monitoring and surveillance equipment in place. Scientific instruments are installed to continuously monitor dam performance by measuring reservoir levels, groundwater within dams, and stream flows. Operation crews perform daily visual inspections on all dams and report unusual conditions and high instrument readings to dam engineers. Federal and state regulators work with our SPU staff to perform annual inspections to ensure safe operating conditions.

All our dams meet current engineering standards and are in compliance with state and federal regulations.

SPU has developed emergency action plans for each high hazard dam facility. These plans are updated on an annual basis, in partnership with local emergency management agencies, King County, the National Weather Service, and state and federal dam regulators.

Related links

Cedar River Watershed (Seattle Public Utilities)
Tolt River Watershed (Seattle Public Utilities)
Take Winter By Storm! (Regional Public Information Network)
Howard Hanson Dam (U.S. Army Corps of Engineers)

For more information about our Dam Safety Program, contact Taryn Sass at (206) 850-9737 or Taryn.sass2@seattle.gov.

For concerns about issues at the Lake Youngs facility or perimeter, please call the Lake Youngs desk at (206) 684-3933.
For emergency related questions, please contact your local emergency management agencies.