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Septage Disposal at South Treatment Plant

Information about the King County septage disposal facility, including how to get permitted, acceptable wastes, directions, and the septage disposal process.

Four trucks in the disposal area at South Treatment Plant

Our facility allows four trucks to dispose of septage simultaneously. 

We operate a septage disposal and treatment facility that’s open around the clock at our South Treatment Plant in Renton. The facility accepts domestic septage (think: wastewater that comes from a residential or commercial bathroom and kitchen) and non-domestic septage (think: wastewater from a commercial facility that’s not from a bathroom or kitchen) haulers who have obtained the proper disposal permits.  

To protect our wastewater treatment process and water quality, we require haulers who want to dispose of non-domestic septage to take an extra step and obtain pre-approval to do so from the King County Industrial Waste Program. Find out more about our commercial septage disposal requirements and why they’re in place: Fact sheet: Sending commercial septage to King County's South Treatment Plant.

What is Septage? 

Septage is liquid and solid material pumped from a septic tank or other similar on-site sewage system. 

Getting permitted

Steps and information on how to get permitted to dispose of domestic (residential) and non-domestic (commercial) septage.

Acceptable wastes

A description of the types of septage that are accepted and not accepted at the septage disposal facility.

Disposal costs

Information on the 2024 rates and fees to dispose of septage at the septage disposal facility at South Treatment Plant.


Detailed driving directions on how to get to the septage treatment facility at South Treatment Plant.

Disposal process

Information on what to expect when you get to the septage disposal facility, including the process of disposing of septage and amenities we offer at the facility.

Annual Septage Haulers Meeting

The annual meeting is for Septage Haulers to be informed of program requirements and updates. King County staff are available to answer questions.