SEATTLE - A pump failed early Thursday morning at the West Point Treatment Plant during a heavy rainstorm, forcing crews to divert untreated sewage and stormwater into Puget Sound.
Officials said the pump failure set off a chain reaction of problems at the plant, which effectively shut it down.
As of Thursday evening, King County had no projection for when the plant would be working again.
The county estimates that between 150 million and 200 million gallons were diverted from the plant directly into Puget Sound, attracting a flock of seagulls around the outfall about three quarters of a mile offshore.
County officials estimate that most of it, as much as 90 percent, is stormwater, like runoff from roofs and streets.
As little as 10 percent is untreated sewage.
"Nevertheless, we're not happy about that, it's not right, it is serious and we need to fix it," said Mark Isaacson, the head of King County's Wastewater Treatment Division.
Isaacson said it was not known what caused the pump to fail.
"We've not had an event like this ever before," Isaacson said.
Complicating matters, the plant is largely underground and became flooded in the storm.
That means tunnels connecting parts of the plant are inaccessible because of high water and would be dangerous for workers because of the potential for electrocution.
County officials were using pumps to lower the water level, which they will need to do before they can even assess the damage.
King County is diverting as much wastewater as possible to other plants, but officials did not have an estimate for how much was being successfully sent elsewhere.
Warning signs are up on beaches at Discovery Park, and officials are testing the water quality.
Millions of gallons of sewage into Puget Sound
Millions of gallons of raw sewage are dumping into Puget Sound after an equipment failure at King County’s West Point Treatment Plant near Seattle’s Discovery Park.
A shutdown occurred when too much incoming wastewater and stormwater -- during heavy rain and very high tides -- started to flood the plant at about 2 a.m. Thursday.
To protect the treatment plant from major flooding that could severely damage equipment, West Point is operating in emergency bypass mode -- meaning untreated sewage is being discharged through an outfall about three-quarters of a mile offshore and 240 feet deep in Puget Sound.
Since the failure, about an estimated 100 million gallons of raw untreated wastewater has gone into the Sound.
King County said it has notified health and regulatory agencies, and is sampling water quality and posting signs warning people to avoid contact with the water over the next several days.
Crews are working to restore operations and clear water from the plant. Their current estimate to restart the plant is 4 p.m. Thursday.
West Point treats wastewater from homes and businesses in Seattle, Shoreline, north Lake Washington, north King County and parts of south Snohomish County.
Other overflows reported in King County
Heavy rain causes overflow into Lake Washington
Heavy rains caused an overflow into Lake Washington from King County’s Medina Pump Station in Bellevue.
Large volumes of rain have exceeded the capacity of the pump station. The overflow is expected to stop when the system returns to design capacity.
Thirteen other overflows reported after heavy rain
As of 11 a.m. on Thursday, 13 other sewage outflows were reported across King County. See an interactive map of overflows below.
© 2018 Cox Media Group.