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South Treatment Plant earns recognition for long-term permit compliance


Commitment to environmental excellence and an outstanding record of permit compliance earned King County’s South Treatment Plant its 19th Platinum Peak Performance Award from the National Association of Clean Water Agencies.


King County's South Treatment Plant in Renton earned the Platinum Peak Performance Award from the National Association of Clean Water Agencies for outstanding compliance with its state and federal permit requirements.

The award honors South Plant’s 19 consecutive years of meeting or surpassing its effluent discharge limits established by National Pollutant Discharge Elimination System (NPDES) permit under the federal Clean Water Act and the state’s Water Pollution Control Law. 

To comply with state and federal discharge permit effluent requirements, South Plant must remove various pollutants from the wastewater in order to meet set limits for biochemical oxygen demand, total suspended solids, fecal coliform counts and total residual chlorine. The permit conditions also require the plant to conduct regular sampling and testing of both its untreated and treated wastewater.

South Plant also earned the Department of Ecology’s “Outstanding Performance Award” for perfect compliance with all permit conditions in 2014. 

In service since 1965, King County’s South Treatment Plant in Renton protects public health and water quality for about 700,000 people in communities south and east of Lake Washington. The plant treats an average of 90 million gallons of wastewater each day, with a capacity to treat up to 300 million gallons during severe storms.

The plant site also hosts the award-winning Waterworks Gardens Park, where art, technology and nature join in a unique way. The park’s extensive network of wetlands acts as a natural treatment system to clean stormwater runoff from the plant site. Waterworks Gardens is open to the public year-round from dawn to dusk.

Additional information about the South Treatment Plant is available online.