Seattle leaders to fix false alarm problems at Tolt Dam

New system will be installed in October; Carnation will hold annual evacuation drill.

Representatives for the mayor of Seattle came to the Carnation City Council meeting Sept. 19 to apologize for recent failures on the Tolt Dam Warning System and announced a series of changes aimed at mitigating future mishaps.

“There’s no sugar coating it, we are making mistakes,” Marco Lowe, Chief Operating Officer for the City of Seattle, told the Carnation Council. “We have to stop.”

The meeting comes as Carnation officials have publicly expressed displeasure with recent failures of the dam’s warning system over the past month, including a recent speech at the Seattle City Council meeting. They are imploring the city of Seattle, which owns the dam, to take recuperative action.

The group of Seattle leaders, who gave a presentation to the council, announced a two-pronged approach to quell a recent string of false and missed alarms of the dam’s emergency warning system.

The warning alarm is designed to sound during a failure of the Tolt Dam — which would inundate the city under an estimated 30 foot wave — but has gone off erroneously three times in the past few months and six times in the past three years.

Some of those false alarms, including the most recent one on Aug. 22, came as technicians were performing work on the alert system and accidentally sent off the alarm.

Seattle Public Utilities (SPU), the agency that manages the dam and provides it with around-the-clock monitoring, is in the process of replacing the dam’s old warning system, installed in the late 1970s, which they say is difficult to maintain and has led to many recent false alarms.

Andrew Lee, general manager of SPU, called the recent false alarms unacceptable, and said technicians would work “expeditiously” to change over to a more stable alert system.

“This is absolutely unacceptable for me as the leader of utilities, it’s unacceptable to you, and it is unacceptable to all the residents and businesses it’s impacted,” he said. “We can and we will do better.”

SPU has been performing regularly scheduled weekly tests on both the old and new systems each Wednesday as it looks to phase in a new alert system. Lee said SPU will fully switch over to the new system by Oct. 18, with the old system last sounding on Oct. 11.

SPU officials said the new system will be the single most important step to preventing future false alarms.

“The vast majority of issues with false alarms have been due to the old system,” said Josh Campbell, project manager for the warning system update. “Simply put, it’s an outdated system that is difficult to maintain and has too many variables that can lead to a false alarm.”

During the August incident, for example, technicians were repairing an old siren antenna downtown when they accidentally pushed the siren button and triggered a false alarm. The input was canceled, but it was too late to cancel the siren command, Campbell said.

The new system is less prone to these mishaps, requiring the button be held for at least a second, Campbell said. The new system also allows for SPU staff to see almost in real time if there’s local activation of the siren.

Additionally, Campbell said, SPU has instituted additional precautionary measures when technicians perform work on the old alert system, including notifying Carnation City Manager Ana Cortez of planned maintenance and disconnecting speaker amplifiers during that work.

In the event of another false alarm, SPU also committed to directly communicate with Cortez and broadcast “all clear” messages over the warning system’s sirens, alerting residents the dam is safe.

Implementation of the new alert system is part of phase 1 of the SPU’s overhaul of the Tolt Dam Warning System. Through 2024, they will continue adding additional sirens, static evacuation signs and making other infrastructure improvements.

Be Dam Ready

Recent advocacy for dam improvements comes as Carnation is prepared to host Be Dam Ready, its annual dam evacuation drill, on Sept. 30.

New for this year’s event, a listening session will be held at 10.m. for residents to voice their concerns about recent false alarms. Local, state, federal and Tribal leaders as well as a representative from Seattle Mayor Bruce Harrell’s office have been invited.

Cortez, the city manager, said members of the Seattle City Council — who were also invited — will not be attending, but acknowledged Council President Debora Juarez has asked for a written report of the event.

“They are paying attention to it because you educated them,” Cortez told the city council. “For most of them [the false alarms] was news and now it isn’t. That is reassuring.”

The evacuation drill begins at 12:30 p.m.