Tolt Dam fails another weekly test following windstorm

Seattle Public Utilities will be presenting to the Carnation City Council on Jan. 19.

The Tolt River Dam warning system failed to activate during a regular weekly test for the third time in the last several months, concerning King County Councilmember Kathy Lambert.

In a statement, Lambert called it part of a “pattern of failures” that erodes the public’s trust and confidence in the dam, which is owned by the City of Seattle. The dam’s reservoir provides water to 1.5 million residents in the area.

If the dam were to fail, the city of Carnation could be flooded with more than 30 feet of fast-moving water in a matter of minutes. In addition to the instances of the alarm failing to activate during tests, last July, the system sent out a false alarm, which led to unnecessary evacuations.

“Since that time, the warning system has failed to activate during its routine weekly test on two separate occasions,” Lambert said in a statement. “Over 1,500 residents of Carnation and the surrounding unincorporated areas rely on the warning system to provide accurate and timely alerts in the event of a dam failure.”

In a statement, Seattle Public Utilities, which maintains the dam, said the utility experienced an audio issue on Jan. 13 with its weekly alarm test following the severe windstorm that moved through Puget Sound earlier this week. It resulted in scattered power outages across the region.

“While the alarm did not sound on Wednesday (Jan. 13) during the weekly test, dam safety monitoring was never interrupted. (Seattle Public Utilities) continues to monitor the dam 24/7 using various technology, including cameras and sensors installed along the Tolt Dam,” the statement reads.

Shortly before the test on Jan. 13, staff conducted a weekly internal test and detected a potential issue related to the audio part of the alert test. Partner agencies were notified, including the city of Carnation.

If there were an emergency, the statement reads, an emergency action plan would be activated that includes King County, Carnation and NORCOM to “communicate timely information to the public.”

The statement also addressed the July 28 false alarm, and states that the utility investigated the issue and replaced a control panel. Staff also met with Carnation officials to discuss the incident and plan short-term repairs and long-term upgrades.

“(Seattle Public Utilities) is prioritizing a system upgrade to the Tolt Dam warning system. Staff have begun designing the system upgrade and are expediting implementation for 2022,” the statement reads.

Seattle Pubic Utilities staff will also be making a presentation at the Carnation City Council meeting on Jan. 19.