Millions of gallons of untreated wastewater and stormwater began dumping into Puget Sound Thursday after high tides and heavy rains overwhelmed a King County wastewater-treatment center in Seattle.
Flooding at West Point Treatment Plant in Magnolia's Discovery Park caused damage that apparently fried an electrical circuit and triggered a system shutdown, a spokesman said.
That has caused the county to operate the facility much of Thursday in "emergency bypass mode" — dumping untreated effluent directly into Puget Sound.
Officials were still calculating how much untreated wastewater had flowed into Puget Sound. Doug Williams, a spokesman for the county's Department of Natural Resources and Parks, estimated more than 150 million to 200 million gallons, with that number likely to grow.
By Thursday night, Williams said the plant was partially back on line and was providing initial treatment to some of the water which had been flowing untreated into the Sound or diverted to other treatment plants.
The dumped sewage is a mix of about 90 percent stormwater and 10 percent wastewater, he said.
The county has managed to divert nearly 200 million gallons of sewage water headed for West Point to four other treatment facilities, Williams said.
Chris Wilke, executive director of Puget Soundkeeper, an environmental watchdog group, said the amount of untreated sewage dumped so far comprises about one-fifth of the typical overflow amount for the area's sewers annually.