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South Treatment Plant, also referred to as South Plant, is located in Renton and is part of King County's regional wastewater treatment system. South Plant was built in 1965.

January 2023 Update

View the Winter 2023 newsletter to learn more about how South Plant protects public health and the environment, turns waste into valuable resources, and offers education and training programs to the community.

We want to hear from you: Our goal is to protect public health and the environment while being a good neighbor. Please take the South Treatment Plant Near Neighbor Survey to share your thoughts and experiences with us. We will use the survey results to give you information that matters to you and your community.

This survey is also available in: Spanish (Español) , Vietnamese (Tiếng Việt) , Simplified Chinese (简体字) and Traditional Chinese (繁體字) . Survey closes April 30, 2023.

aerial view of the treatment plantSouth Treatment Plant in Renton. View more photos on our Flickr site .

South Plant treats wastewater for about 839,000 people living in Auburn, Kent, Renton, Bellevue, Issaquah, and Sammamish, 24 hours a day, 365 days a year. During the dry months, about 90 million gallons per day of wastewater gets treated. About 300 million gallons per day can be treated during the rain/storm season. South Plant also recovers valuable resources from the treatment process, including recycled water, biogas, and Loop biosolids.

Learn more

Contact us

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

1200 Monster Road S.W.
Renton, WA 98057

Directions and map, and septage disposal map

If you’d like to receive email or text updates on the South Treatment Plant:

La planta de tratamiento sur del condado de King limpia un promedio de 90 millones de galones de agua que usamos todos los días en nuestros hogares, escuelas y negocios. Nuestro objetivo es proteger la salud pública y el medio ambiente siendo un buen vecino. 
Nhà Máy Xử Lý Nước Thải Phía Nam Quận King hoạt động với công suất có khả năng làm sạch trung bình 90 triệu gallon nước mà chúng ta sử dụng hàng ngày tại nhà, trường học và doanh nghiệp. Mục tiêu của chúng tôi là bảo vệ sức khỏe cộng đồng và môi trường, đồng thời trở thành một người hàng xóm thân thiện.