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Built in 1965, South plant treats the wastewater for about 839,000 people living east and south of Lake Washington.


  • South plant was built as a secondary treatment plant and completed in 1965.
  • In 1986, a new effluent discharge pipeline and outfall was completed to eliminate discharges to the Green/Duwamish River and carry treated wastewater 12 miles to a deep-water outfall in Puget Sound.
  • In 1997, South plant began producing reclaimed water.
  • In 2001, the South plant was expanded to its current capacity of 115 million gallons per day of average wet weather flow and 325 million gallons per day during peak storms.

Regional system history

In 1958 voters approved the creation of a regional wastewater treatment system to clean the wastewater being generated from the developing cities. Metro was formed as the organization to build and manage this system and was later merged with King County. More regional wastewater system history.

Construction of the Renton (South) Treatment Plant in the 1960's.South Treatment Plant under construction in the 1960s.

View more photos on our Flickr site .

Contact us

24 hour emergency and odor reporting:   206-263-1760
Administration:  206-263-1810

1200 Monster Road SW
Renton, WA 98057

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