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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).

August 27

Notice of Saturday work at Seward Park construction site:
The construction team will be on site on Saturday, August 29th from 9:00 a.m. to 5:00 p.m. to continue working on installation of piles. A Seattle Public Utilities (SPU) representative will be on site during this time.

Upcoming construction in 57th Ave South near Martha Washington Park:
Construction in 57th Avenue South for the Henderson North CSO Reduction project is scheduled to begin in mid-September and is estimated to take approximately six months to complete. SPU will construct a 16,000-gallon storage pipe located in the right-of-way of 57th Avenue South (adjacent to Martha Washington Park) to reduce the frequency and amount of stormwater and untreated sewage that overflows into Lake Washington during heavy rain events. The storage pipe will be located within 57th Avenue South near an existing below ground pump station.

The construction area and the southeast entrance to Martha Washington Park will be closed to public use during this period. Construction activities will generally include excavation and removal of the existing sewer pipe and maintenance holes within the street and installation of a larger sewer pipe and maintenance holes. Additional information will be provided as construction approaches and regularly during the construction period through the project website and this email listserv.

The project team is working to minimize construction impacts where possible and create a safe work zone in the 57th Avenue South right-of-way. General impacts include:

  • Parking restrictions at the southern boundary of Martha Washington Park (eastern end of 57th Avenue South).
  • Regular work hours between 7:00 a.m. and 6:00 p.m., Monday through Friday. The contractor also expects to work on Saturdays in order to complete construction activities as quickly as possible. Certain activities may require longer hours on occasion.
  • Increased truck and construction vehicle traffic on 57th Avenue South, near the construction site.
  • The southeast entrance to Martha Washington Park will be closed (at the dead end of 57th Avenue South); however, the Park will remain open during construction.
  • Noise, dust, and vibration during construction activities.
  • Driveway access in the project area will not be impacted.

57th Ave South pre-construction drop-in session on Tuesday, September 8th, 2015:
More information about what to expect during construction in 57th Avenue South will be presented at a public pre-construction drop-in session on Tuesday, September 8th from 5:30 to 6:30 p.m. at the eastern end of 57th Avenue South (southern entrance of Martha Washington Park). This will be an opportunity to talk one-on-one with the project team and construction company.

Project goals and benefits

This project will reduce the frequency of sewage overflows into Lake Washington to no more than one per year per outfall (on average). SPU plans to complete two new underground storage facilities in North Henderson to store excess combined sewage and stormwater during major rain. The underground storage facilities are located offshore in the following locations:

  • 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.


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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