Metropolitan King County Council will consider a call by some members Monday to appoint a third-party investigator to find out what happened in the catastrophic flood at West Point wastewater-treatment plant.

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Amid dueling calls for an independent investigation into the flood that extensively damaged the West Point wastewater-treatment plant, King County wastewater managers Tuesday revealed preliminary findings into the causes of the flood.

While still ongoing, the review, so far, points to failed float switches that allowed raw sewage and stormwater to keep pouring into the plant at maximum flow during a rainstorm. That happened even as crew members struggled to restart failed pumps that were supposed to be taking treated water from it.

The result, as minutes ticked by, was a catastrophic flood as wastewater surged into the plant uncontrolled and cascaded down the stairs to destroy electrical panels, wiring, motors and more in the region’s largest wastewater-treatment plant.

West Point treatment plant

‘Lucky no one died’: What caused the catastrophic flood at West Point


The trouble started when a fault in the electrical supply to the effluent pumps caused them to shut down shortly after 2 a.m. on Feb. 9.

Crew members relied on float switches, which are supposed to trip automatically, to shut off incoming flow as wastewater rose in primary-treatment tanks. They wanted to contain the wastewater in the plant for treatment, once they got the pumps going again, rather than shunt it untreated to Puget Sound through an emergency bypass, said Christie True, director of the King County Department of Natural Resources and Parks.

The crew did not realize that the switches had failed and that flow was still coursing into the plant. They eventually manually shut down the pumps as wastewater flooded the tanks. An automatic gate also opened, shunting raw sewage and stormwater away from the plant into the emergency bypass and into Puget Sound. But by then, the damage to the plant was already done.

True said the crew on duty acted as they should have and the failings were electrical and mechanical.

The review is ongoing. So far, neither the incoming power supply nor the transformers seem to have been at issue.

True said the county is hiring a third-party consultant to investigate the incident, in addition to the review being done by the department and its staff and consultants.

That angered some on the Metropolitan King County Council, which Monday will consider a proposal by three members who want to commission a consultant to conduct a review for the council.

Several members said they felt that they had not received enough information in a briefing held last week on the flood by wastewater managers, and that they had not even known the department was coming out with its preliminary findings.

Any review commissioned by the department and reviewed by it is “the fox guarding the chicken house,” said Councilwoman Jeanne Kohl-Welles, who called for the council’s independent review, along with council members Rod Dembowski and Kathy Lambert.

“We don’t want them sugarcoating anything. We want to be the ones leading it,” said Lambert, incoming chair of the Regional Water Quality Committee.

Work to restore the plant is ongoing. Cleanup is completed, and repair of motors damaged during the flood is at about 80 percent. A team of consultants is working on the physical restoration of the plant while two other teams are determining how to maintain and restart secondary treatment at the plant, which is required by the plant’s state permit.

True set a tentative restart date for the plant of April 30. Meeting that goal depends partly on how well biological systems idled while the plant is damaged can be coaxed back into performance of secondary treatment.