Tolt Dam Early Warning System

Photo of Tolt river

This project will improve the resiliency and reliability of the Tolt Dam Early Warning System. 

August 1, 2025 Update

Dear Carnation Community - Seattle Public Utilities is still in the process of reviewing the third-party report with our partnering agencies. We plan to post the report to this web page by mid-August and apologize for the delay. 

February 11, 2025 Update

Seattle Public Utilities has hired a panel of third-party experts (see information below about panelists) to review the Tolt Dam Early Warning (siren) System and provide suggestions for a path forward for the project.

The panel is currently:

  • Reviewing regulations that relate to dam safety, public alerting, and emergency response.
  • Evaluating past issues related to the Tolt Dam Early Warning System and how the City of Seattle responded.
  • Conducting interviews with residents, business owners, visitors, Carnation elected officials, King County Office of Emergency Management staff, agency partners, and other key stakeholders.

The panel will be in the Carnation community several times over the next few months, visiting project features and gathering information. They will develop recommendations and considerations for a path forward regarding the Tolt Dam Early Warning System. The results of that assessment will be summarized and shared in a public report on this website by July 2025. If you have any questions about this process or information to share with the panel, please contact our project team at tews.info@seattle.gov or (206) 494-5986.

Panel members:

Project Manager: Greg Richards, Gannett Fleming

Greg is a senior project manager in the dams and hydropower group of Gannett Fleming. He is a strong leader in dam safety and has led efforts related to dam failures and incidents including the development of the Association of State Dam Safety Officials’ (ASDSO) DamFailures.org website. He is experienced in the organization of multidisciplinary teams and will lead the coordination and project management aspects of this project to keep the team on track and complete the project on time.

Team Lead / Dam Safety and Risk Expert: Mark Baker, Dam Crest Consulting

Mark is an industry leader with extensive dam safety and risk experience working at US Bureau of Reclamation (USBR), the National Park Service (NPS), and Bureau of Indian Affairs (BIA). He has also performed independent dam incident investigations and led the Spencer Dam failure Investigation team. He worked extensively with USBR/BIA putting in warning systems and worked for years on improving their reliability. He understands issues related to dam failure alarms, including false alarms and response related to them. He also covered the human factors portion of Spencer Dam investigation and is a leader in that regard. He is the chair of the ASDSO Dam Failures & Incidents Committee.

Emergency Management and Public Alerting expert: Dr. John Sorensen, Independent Researcher

John is a recognized expert with decades of experience in hazard and emergency management. He has researched evacuation and warning throughout his career. He worked on HEC-Lifesim, a software widely used in the dam industry for evaluating the consequences of dam failures. He has authored several key guidelines for the US Army Corp of Engineers (USACE) on the public alert and warning for dam and levee emergencies. He was involved in the Oroville dam spillway incident to evaluate the evacuation of the downstream communities. He has done studies on false warning and the impact on evacuation.

Risk Communication expert: Prof. Ann Bostrom, University of Washington

Ann is a recognized expert in risk communication and has collaborated on investigations of public and professional communication for diverse hazards, including earthquakes, flashfloods, and hurricanes. She has contributed to numerous studies on risk perception and communications of warning systems and responses to hazard forecasts and warnings. She. has also advised several federal agencies on science and risk communication through her work on science advisory committees and on the National Academies of Sciences, Engineering, and Medicine committees.

Project description

The Tolt Dam Early Warning System alerts residents in the City of Carnation to evacuate in the unlikely event of a dam failure. The first emergency warning system for the Tolt Dam area was implemented in 1978 as a single siren controlled by King County. The City of Seattle took over responsibility for the siren system in 1981 and the first network improvement occurred in 1985. Additional improvements were made in 1993. The capital project will replace the aging system, now in its fifth generation and difficult to maintain, with state-of-the-art technology and equipment that will improve the resiliency, reliability, and security of the emergency warning system.

The project will:

  1. Replace, and improve outdated siren and supporting system components.
  2. Add redundancy, resiliency, and reliability where necessary.
  3. Address consistent evacuation procedures and protocols with additional signage.
  4. Listen and respond to community needs and suggestions.

Location

New outdoor sirens and indoor alerting devices have been installed at key locations within the inundation area. This included replacing sirens at existing sites and adding three new siren locations for sirens and additional highway messages signs.

Here are the locations where the 7 new outdoor sirens and the 4 new indoor sirens (annunciators) have been installed for phase one of the project:

  1. 35805 NE 80th St (replaced outdoor siren)
  2. 6921 Tolt River Rd NE (replaced outdoor siren)
  3. 5502 Tolt River Rd NE (replaced outdoor siren)
  4. 32421 E Entwistle St (replaced outdoor siren)
  5. Tolt MacDonald Park (new outdoor siren)
  6. Near the intersection of NE 60th St and SR 203 (new outdoor siren)
  7. Tolt Highlands Rd NE and Tolt River Road NE, City of Carnation Public Works yard (new outdoor siren)
  8. 4950 Tolt Ave –Elementary School (replaced indoor annunciator)
  9. 3740 Tolt Avenue –Middle School (replaced indoor annunciator)
  10. 3944 320th Ave NE – Bus Facility (replaced indoor annunciator)
  11. 3600 Tolt Ave – Fire Station (replaced indoor annunciator)

Community benefits

This project will improve the resiliency and reliability of the Tolt Early Warning System by upgrading it with state-of-the-art technology and equipment and adding more redundancy in the system. When the project is completed, stakeholders and residents in the Carnation area will have a new emergency warning system that better meets the needs and expectations of the community.

Community engagement and project materials

The project team provides bi-weekly updates to Carnation City officials, updates this website regularly, and sends informational emails to subscribers.

Please subscribe to the project email list to receive these updates.  

ALERT King County: To stay informed about potential hazards and threats that impact the Carnation area, including status updates on the Tolt warning system, sign up for ALERT King County.  

All materials PDF format unless noted as video.

Additional alerts and warning systems

The combination of outdoor and indoor siren locations is designed to reach as many people as possible in the Carnation area and is just one component of the emergency notification plan for the Tolt Dam. Other alert and warning systems that will be used in the event of an emergency include:

  • ALERT King County notifications sent to everyone who is signed up
  • Wireless Emergency Alerts sent to all available mobile devices in the area, similar to Amber Alerts. Double check that emergency and/or public safety alerts are enabled on your phones.
  • On-the-ground evacuation notices made by local police and firefighters in Carnation, including knocking on doors and loudspeaker messages
  • Emergency TV and radio alerts made to the Puget Sound area
  • Social media alerts posted by local agencies
  • National Oceanic and Atmospheric Administration (NOAA) and National Weather Service (NWS) weather radio warnings delivered
  • Local community notifications from family, friends, coworkers, and neighbors

Engagement & Collaboration

Community Outreach and City Council Updates: 2021-2024

Phase 1, Siren Replacement Project*

  • Design: 2021
  • Permits & Final Design: 2021-2022
  • Construction & Commissioning: 2023-2024 (we are here).

*SPU is actively working to boost volume and clarity on the new system by reprogramming the spoken voice, installing more powerful speakers for all the sirens, and adding two new siren locations: one at Tolt MacDonald Park and one at NE 60th.

Phase 2, Other Project Components**

  • Design: 2021
  • Permits: 2022-2024
  • Advertisement & Contracting: 2024
  • Construction & Commissioning: 2024

**Phase 2 components include digital highway message and fixed evacuation signs, additional indoor sirens, microwave link and data network improvements.

SPU is coordinating closely with contractors, vendors, and permitting authorities to complete this project. This information will be updated if supply chain challenges, permitting requirements, or other impacts change this schedule.

Seattle Public Utilities (SPU) owns and operates the Tolt Reservoir and Dams, located 16 miles upstream from the City of Carnation on the South Fork Tolt River. The reservoir stores 57,900 acre-ft of water to supply 30% of the drinking water for 1.6 million people in the greater Seattle area. Seattle City Light (SCL) owns and operates a system that generates power from water released from the South Fork Tolt Dam. Both SPU and SCL are bound to Federal Energy Regulatory Committee (FERC) requirements.

The Tolt Early Warning System alerts residents in the City of Carnation and in the nearby unincorporated area to evacuate in the unlikely event of a dam failure. The very first siren for the Tolt Dam area was implemented in 1978 as a single siren controlled by King County. The City of Seattle took over responsibility for the siren network in 1981 and the first improved network was installed in 1985. Additional improvements were made in 1993. The aging system, now in its fifth generation, is being replaced.

Public Utilities

Andrew Lee, General Manager and CEO
Address: 700 5th Avenue, Suite 4900, Seattle, WA, 98104
Mailing Address: PO Box 34018, Seattle, WA, 98124-5177
Phone: (206) 684-3000
SPUCustomerService@seattle.gov

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Seattle Public Utilities (SPU) is comprised of three major direct-service providing utilities: the Water Utility, the Drainage and Wastewater Utility, and the Solid Waste Utility.