Tolt Dam Early Warning System

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

December 12, 2023 update:

New Sirens to Begin Sounding Off for Weekly Tests as Early as December 13

Seattle Public Utilities (SPU) is continuing upgrades to the new Tolt Dam Early Warning System.

To help boost the volume and expand the reach of the system, over the past two weeks, crews added two new sirens and relocated one siren. Pending final installation, all three of the new siren locations will begin sounding off for the weekly tests as early as December 13.

  • The two new sirens were installed at Tolt MacDonald Park and near the intersection of NE 60th St and SR 203.
  • The siren near Tolt River Rd and 334th Ave NE was relocated to the City of Carnation's Public Works yard about 1,000 yards west.
  • Crews also reprogrammed the spoken voice from male to female to increase clarity. They also upgraded all existing outdoor sirens with more powerful speakers. As speaker installations are complete, SPU will begin incorporating the upgraded speakers into the weekly Wednesday noon tests.

Listen to a recording of the weekly Wednesday noon test.

Phase 2 enhancements will continue in 2024 and include additional indoor alerting devices, new static evacuation signs, and highway message signs. These components are expected to be completed by the end of 2024.

For the latest information about the project, please continue to check this website and subscribe to the project email list.  

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 Replace, and improve outdated siren and supporting system components.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 (outdoor siren)
  2. 6921 Tolt River Rd NE (outdoor siren)
  3. 5502 Tolt River Rd NE (outdoor siren)
  4. 32421 E Entwistle St (outdoor siren)
  5. Tolt MacDonald Park (outdoor siren)
  6. Near the intersection of NE 60th St and SR 203 (outdoor siren)
  7. Tolt Highlands Rd NE and Tolt River Road NE, City of Carnation Public Works yard (outdoor siren)
  8. 4950 Tolt Ave –Elementary School (indoor annunciator)
  9. 3740 Tolt Avenue –Middle School (indoor annunciator)
  10. 3944 320th Ave NE – Bus Facility (indoor annunciator)
  11. 3600 Tolt Ave – Fire Station (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 team plans to update the Carnation City Council and hold a community meeting in Spring 2023. Stay tuned for more information about these events as they are confirmed online.

Please subscribe to the project email list to receive up-to-date information throughout design and construction. 

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.

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 1.5 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.