Tolt Dam Early Warning System

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

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 Replace, and improve outdated siren and supporting system components.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 proposed at key locations within the inundation area. This includes replacing sirens at existing sites and identifying new locations for sirens and highway messages signs.

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

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.  

Schedule

Siren Replacement (existing outdoor and indoor locations)

  • Quarterly community meetings begin 1st Quarter, 2021
  • Design completed 3rd Quarter, 2021
  • FCC (Federal Communications Commission) Permits issued 4th Quarter, 2021
  • Construction completed 2nd Quarter, 2022

Other Project Components (highway message signs, additional siren locations, microwave link and data network improvements)

  • Design completed 4th Quarter, 2021
  • FCC (Federal Communications Commission) Permits issued 2nd Quarter, 2022
  • Construction completed 4th Quarter, 2022

 

Background

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.