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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).

March 16, 2015

Construction at the Seward Park portion of the project continues, with the following activities scheduled for the next several weeks:

  • Removal of the tennis courts and poplar trees to the east of the tennis courts to clear the area for construction of utilities and the storage tank.
  • Installation of electrical power at the construction site.
  • Increased truck and construction equipment traffic.

While Seattle Public Utilities (SPU) worked to reduce the number of trees that need to be taken down, some will need to be removed to construct the storage tank and adjacent shoreline enhancements. Many of the trees will be reused for shoreline and natural area habitat. In addition, the City has a "2 for 1" tree replacement initiative that requires City projects to replant two trees for every one tree removed. Many new trees will be planted as part of restoration of the construction; the remainder will be planted in Seward Park following construction.

Work in 57th Ave S, adjacent to Martha Washington Park:

  • Construction of the underground facility near Martha Washington park is scheduled to begin in summer 2015. The work will take place in the right-of-way on 57th Ave S and will consist of piping improvements. Work is anticipated to take approximately six months to complete.
  • 5560 S Holly St property: This City-owned property was purchased for the project. Project design changes allowed for the property to be declared excess to SPU’s needs. The City Council has approved legislation for the property to be sold through a competitive process. The property has been listed for sale. Offering information can be obtained through your own broker or through James Tjoa and Associates RE/MAX Metro Realty, 206-726-6230,

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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