20th Ave S Drainage Improvement Project

Project Location

20th Ave S., between S 124th St and S 120th St.

Project Overview 

This project was first included in the 2012 Burien Storm Drainage Master Plan. Video inspections of the drainage pipes along 20th Ave S revealed numerous deficiencies in the conveyance system requiring repair or replacement.

This project consists of decommissioning or removing the majority of the existing drainage system on the east side of 20th and installing a new piped system on the west side of the street, with several pipe crossings to connect existing private drain lines back into the public drainage system.

Improvements include:

  • Removal or abandonment of approx. 900 linear feet of existing storm pipe on the east side of 20th
  • Repair of approx. 350 linear feet of existing storm pipe on the east side of 20th
  • Installation of approx. 870 linear feet of new storm pipe on the west side of 20th
  • Installation of 8 pipe crossings of 20th to reconnect existing private drain lines from east side properties
  • Restoration of affected areas and property frontages
Black and white map detailing 20th Ave S Proposed Storm Drainage Project Site Plan.Download full size image.

Project Status

Scheduled Start Date: Fall 2022 (construction)
Scheduled Completion Date: Project construction was completed in January 2023.

Neighborhood Impact 

Construction work will occur primarily on one side of 20th Ave S at a time, for removing or installing pipe. It is expected that the contractor will allow local traffic to pass, but there may be short delays for maneuvering equipment, etc. Short-term full road closures will likely occur while the road crossings are installed. Access will be maintained throughout the rest of the street during these closures.

Access to all properties will be maintained for the duration of the project work, though vehicular access may be limited during the workday while active construction is occurring in front of homes and driveways. Residents will be encouraged to either park elsewhere on the street during these times, or move vehicles out of driveways in the morning to prevent access issues.

Additionally, storage of construction equipment and project materials will likely take place along portions of 20th Ave S for the duration of the project. This will likely limit available parking on the road shoulders, but access to driveways will be maintained.

Project Manager

Dan O’Brien

Stormwater Engineer

(206) 241-4647

[email protected]


Updated May 8, 2023