South Park Water Quality Facility

Photo of northern part of South Park.
This project will improve water quality in the northern part of South Park.

Project description

Improving chronic flooding and drainage issues in South Park 
SPU will build a water quality facility to treat stormwater from the drainage system before it flows into the Duwamish Waterway. Before we can operate the new water quality facility, we must construct a pump station that will ultimately send flows to the water quality facility.

What's happening now?

SPU is currently selecting water quality treatment technology, project site, and creating initial facility layout, sizing and operation plan.

Community benefits

When complete, this project will clean stormwater before it flows into the Duwamish Waterway. Combined with the pump station, this project will allow the system to accommodate the expansion of the drainage improvements being planned in South Park.

Community engagement

SPU is committed to providing timely information and updates on project activities. Sign up for South Park project updates.


  • Options evaluation, property acquisition


  • Design and construction

Seattle Public Utilities is currently working on three stormwater projects in northwest South Park’s lower industrial basin to reduce flooding and improve water quality in the Lower Duwamish Waterway.

  1. A drainage and roadway project to construct streets and a drainage system to improve chronic flooding and drainage issues.
  2. flood control pump station to overcome the flooding effects of high tide.

SPU originally decided to build a stormwater treatment facility in the 7th Ave S drainage basin because of the industrial nature of the lower (and northern) portion of the basin, and because the system drains into the Duwamish Waterway, which has poor water quality. Large-scale, centralized treatment of municipal stormwater is a new and emerging approach to addressing polluted stormwater runoff. At that time, SPU selected a treatment technology based on what was available and created a design for the combined water quality facility and pump station.
As more data became available about the performance and maintenance requirements of the treatment technology selected, SPU decided to take another look at other available and more effective treatment technologies. SPU is currently selecting a treatment technology for the water quality facility.
From the pump station, stormwater will be sent through the water quality facility, where it will be treated to remove a variety of pollutants that are common in urban stormwater runoff. The treated stormwater will then be released through the existing outfall to the Duwamish Waterway, resulting in cleaner water and a healthier Duwamish Waterway.

Public Utilities

Andrew Lee, General Manager and CEO
Address: 700 5th Avenue, Suite 4900, Seattle, WA, 98104
Mailing Address: PO Box 34018, Seattle, WA, 98124-5177
Phone: (206) 684-3000

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Seattle Public Utilities (SPU) is comprised of three major direct-service providing utilities: the Water Utility, the Drainage and Wastewater Utility, and the Solid Waste Utility.