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North Henderson


North Henderson project area.

What & Why?

What's happening now?

Construction will be underway on the Seward Park site between early 2015 and mid 2017. The park remains open, but parking will be affected. View parking map (pdf).

February 11, 2015

Construction of the Seward Park portion of the North Henderson Combined Sewer Overflow Reduction project is scheduled to begin the week of February 23. The project team is working to minimize impacts where possible and create a safe work zone within Seward Park. Over the course of the project (construction through mid-2017), impacts will vary by season and the type of construction underway. General construction impacts include:

  • Closure of the tennis courts and adjacent parking lot. Signs will be installed to direct visitors to other parking lots.
  • Increased truck and construction vehicle traffic at entrance of Seward Park and nearby streets.
  • Noise, dust and vibration during construction activities.
  • Pedestrian and bicycle impacts will be minimal, aside from the closure of the tennis courts and adjacent parking lot.

Over the first few weeks the noticeable activities will include:

  • Fencing around the project site and closure of the tennis courts and adjacent parking lot.
  • Removal of the tennis courts and poplar trees to the east of the tennis courts.
  • Increased truck and construction equipment traffic.

While construction impacts will generally be confined to the fenced construction site, we remind everyone to stay safe and cautious of the construction trucks and equipment.

Project benefits

The North Henderson CSO Reduction Project (North Henderson) will reduce the amount of untreated sewage and stormwater that overflows into Lake Washington at two outfalls located offshore of:

  • Seward Park - view map of Basin 44 CSO improvements (pdf)
    The project includes additional piping, outfall replacement, with shoreline work and landscape improvements.
  • 57th Ave. S. near Martha Washington Park - view map of Basin 45 CSO improvements (pdf)
    The proposed underground facility for Basin 45 consists of a 16,000 gallon pipe and piping improvements.

The end result

To reduce the frequency of sewage overflows to no more than one per year per outfall, on average, SPU plans to complete two new underground storage facilities in North Henderson in 2017 to store excess combined sewage and stormwater during major rain.


Ask Us

Alan Lord, PE, Project Manager
(206) 233-1565

Please specify the project site with your comments:

  • Seward Park (Basin 44) or
  • 57th Ave. S. right-of-way (Basin 45)

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