King County wastewater system resuming normal operations after extreme rain

King County's wastewater treatment system is again resuming normal operation four days after a severe storm brought torrential rain that battered regional sewer and stormwater facilities.

The county's South Treatment Plant in Renton recorded its highest flow ever on Monday, treating 241 million gallons of wastewater in a 24-hour period. The plant usually treats about 115 million gallons a day during rainy weather.

West Point Treatment Plant in Magnolia far exceeded its maximum design capacity of 440 million gallons a day, recording a peak flow of 475 million gallons. The plant, which handles both stormwater and wastewater for much of Seattle, normally treats about 133 million gallons of wastewater on an average rainy day.

After the storm, sewer utility crews responded to stormwater and wastewater overflows in Seattle's Myrtle Edwards Park, Shoreline's Hidden Lake neighborhood, and in Renton just south of Kennydale, which occurred when sewer pipes were overwhelmed by extreme high flows after more than 4 inches of rain pummeled the area in just 24 hours.

Crews also responded to overflows in Kenmore, Bothell, Kirkland, and Juanita.

To protect public health, King County posted beaches and affected areas as closed, took water samples, and told health and regulatory agencies about the overflows.

The county's Wastewater Treatment Division protects public health and water quality by serving 17 cities, 17 local sewer utilities and more than 1.4 million residents in King, Snohomish and Pierce counties. Formerly called Metro, the regional clean-water agency now operated by King County has been preventing water pollution for more than 40 years.