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Pump Station and Water Quality Facility

This project is a first step toward protecting people from flooding and protecting the Duwamish Waterway from polluted stormwater runoff.


The North West industrial and residential area of South Park experiences chronic flooding for three reasons:

  1. The main drainage pipe to the Lower Duwamish Waterway is underwater during high tide. This causes water to back up in the drainage system and sometimes flow back out of inlets and catch basins, flooding the neighborhood.
  2. Not all streets in the area have a drainage collection system. Additional connections cannot be built until the pump station is installed so that the pipes can drain at high tide.
  3. Many private properties in the basin do not have drainage pipes connected to the public drainage system. Some properties are lower than the street or there is no collection system in the street to connect to.

Pump Station

The pump station will make it possible to pump stormwater from the existing drainage system during high tide when the outfall to the Lower Duwamish Waterway is underwater.

Water Quality Facility

From the pump station, stormwater will be sent through the facility where it will be filtered to remove a variety of pollutants that are common in urban runoff. The stormwater will be released through the existing outfall to the waterway. This will result in cleaner water and a healthier environment.

Project Site

The site for this project was selected because of its location on the main stormwater drainage pipe where it empties into the waterway. The facility will be located along the edge of 7th Avenue South near Riverside Drive and on adjacent land parcels already owned by Seattle Public Utilities.

The project will have underground equipment and above-ground structures including a small electrical controls building and a concrete structure, about 12 feet tall, 50 feet wide and 110 feet long. The facility will be fenced for security and will have security lighting. It will be run remotely so staff will only visit the site periodically to check and maintain it.

Project Update - Oct. 4, 2013

What’s Next?

SPU is in the process of evaluating stormwater treatment technologies for the South Park Pump Station. Project design and construction are delayed because our technical team is reevaluating appropriate technology in light of new information on the performance and maintenance needs of the selected treatment technology that indicate it might not perform as effectively or affordably as anticipated. In addition, the technical team is evaluating new technologies which have recently become available.

SPU follows a deliberate process for making transparent decisions fully informed by:

  • Project Risks
  • Financial, environmental, and social impacts and benefits
  • Project Life-cycle Cost

In light of the new information, SPU is evaluating treatment technologies to balance water quality treatment and protection of the Duwamish River with project costs. We need to compare options based on the new information. 

Current planning calls for this analysis to be complete in summer of 2014, and the design process will move forward in as soon as possible after a decision is made.

To ask questions or let us know what you think, email the project manager or give her a call: Sheila Harrison, (206) 684-5899.