Tolt Dam Early Warning System

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

August 18, 2025 Update: Third-Party Review Report Now Available

Dam safety

The Tolt Dam has been and continues to be safe. The City of Seattle monitors the dam 24/7, 365 days a year with around-the-clock system operators and daily in-person safety checks at the site. Automated continuous monitoring of reservoir level, upstream and downstream river flows, and dam safety sensors are also a part of the 24/7/365 dam safety watch. 

Tolt Dam Early Warning (Siren) System

The Tolt Dam is equipped with an Early Warning System intended to alert downstream residents in the City of Carnation and surrounding areas in the unlikely event of a dam emergency. The warning system has four indoor and seven outdoor sirens (see siren and annunciator locations on this page).

Under the State law (RCW 38.52), emergency management including alerting and evacuation of local residents for all pertinent hazards is the responsibility of local jurisdictions. The City of Carnation is responsible for emergency management within its incorporated limits while King County is responsible for the unincorporated areas.

The City of Seattle, as the owner and operator of the Tolt dam, is responsible for safety of the dam and notifying emergency management agencies of any emergency related to the dam. The City of Seattle works closely with the City of Carnation and King County on emergency preparedness related to the Tolt dam. 

In 2020, the City of Seattle began a project to replace the aging early warning system with state-of-the-art technology and equipment that will improve the resiliency, reliability, and security of the system.

Siren system status

As a reminder, in collaboration with the City of Carnation and King County Office of Emergency Management, the warning system was turned off in March 2024. The City of Seattle is currently working with both agencies on short- and long-term plans for the system, including when to turn the system back on.

In the unlikely event of a Tolt Dam emergency, the City of Seattle will promptly notify the King County Office of Emergency Management, City of Carnation and other emergency management agencies. In turn, they will provide public notifications using existing emergency notification systems including the Wireless Emergency Alert system, King County ALERT notifications, Reverse 911 phone calls, and weather radio notifications. These systems are consistent with current emergency notification practices and have been in place long before the sirens were turned off in 2024 and will continue to be used. 

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.

Third-Party review report

In 2024, the City of Seattle, with concurrence from the City of Carnation, voluntarily hired an independent panel of experts to review the Tolt Dam Early Warning (siren) System. The scope of this work included reviewing the following items:

• Tolt Dam Early Warning System and siren sounding incidents
• Dam safety assessments
• Emergency management roles and responsibilities, and public alerting
• Public communication

The panel was responsible for evaluating them with respect to current regulations and industry best practices and provide findings and recommendations for a path forward.

The City of Seattle, City of Carnation, and King County Office of Emergency Management reviewed the draft report for technical comments and clarifications. The independent team considered and addressed the comments as appropriate while maintaining their independence. In addition, the City of Carnation provided comments about the report.

The panel has completed their review and prepared a full report, executive summary, and a statement about the July 4, 2025, Texas floods.