Tolt Dam Early Warning System

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

November 27, 2023 update:

New Sirens, Upgrades, and Reprogrammed Voice

Seattle Public Utilities (SPU) is continuing upgrades to the new Tolt Dam Early Warning System, which will improve the volume and clarity of the system. 

Starting the week of November 27 through early 2024, crews will be on site to complete various improvements including:

  • Reprogramming the spoken voice from the male voice to a female voice to increase clarity. Residents may begin hearing the female voice as early as November 29 when the weekly Wednesday Noon test is conducted.
  • Upgrading all existing outdoor sirens with more powerful speakers
  • Installing two new outdoor sirens. Once installation and testing are complete, the new sirens will help increase the reach of the warning system and will be included in the weekly Wednesday noon tests. The new sirens will be installed at the:
    • Tolt MacDonald Park
    • Intersection of NE 60th St and SR 203  
  • Relocating the siren near Tolt River Road and 334th Ave NE to the City of Carnation's Public Works yard about 1,000 yards west

This work will resemble utility pole work and may include machinery, possible tree trimming on site, and some evening and weekend work. Construction for these improvements is expected to be completed by early 2024.

Phase 2 enhancements will continue in 2024 and include additional indoor alerting devices, new static 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 are being installed at key locations within the inundation area. This includes replacing sirens at existing sites and identifying new locations for sirens and highway messages signs.

Here are the locations where the 4 new outdoor sirens and the 5 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.    334th Ave NE and Tolt River Road NE (outdoor siren)

6.    4950 Tolt Ave –Elementary School (indoor annunciator)

7.    3740 Tolt Avenue –Middle School (indoor annunciator)

8.    3944 320th Ave NE – Bus Facility (indoor annunciator)

9.    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.