Early work updates

Early work begins at Harbor Island this fall

Starting as early as November 2026, Sound Transit crews will begin bi-directional load testing on Port of Seattle property in the south end of Harbor Island. The results will help guide the design of a future bridge over the Duwamish River for the West Seattle Link Extension. We are sharing this information early so businesses, tenants, marina users, and the Port have time to understand the work and ask questions before construction begins.

  • When? Work will begin as early as November 2, 2026 and last about four months. Crews will typically work weekdays between 7 a.m. and 7 p.m.
  • Where? Southwest corner of Harbor Island (see work area map below).

What to expect

Neighbors and people traveling through the area should expect:

  • Restricted access to the work areas for the duration of the work.*
  • Reduced parking in the areas surrounding the construction site.
  • Repurposed areas around the work area to store construction equipment and materials.
  • Increased noise from construction activity during working hours.

*See the work area map below for closure locations and access details.

Work area map

Map of the load testing work area at the southwest corner of Harbor Island. The drilling site and equipment storage are along the west side, next to the Jim Clark Marina. Trucks use a route along the west and south edges that is closed to the public. Parking and access to Jim Clark Marina are to the west, a pedestrian access path runs alongside the truck route, public access continues on the road to the east, and a second work area sits in the southeast corner next to restroom access for Harbor Island Marina. Access to all marinas and docks will be maintained during work.
Map of the work area, closures and access routes (select to enlarge)

How we’re minimizing impacts

Sound Transit is working with the Port of Seattle to maintain access to businesses and marina facilities during load testing and to reduce impacts where possible. Check back on this page for more information and updates during testing.

What is bi-directional load testing?

Bi-directional load testing is a method of measuring how much weight bridge foundations can safely support by applying pressure within a test foundation shaft and measuring how the ground responds. This work helps the project team confirm soil conditions and foundation designs for the future light rail bridge over the Duwamish River.

Please note that crews will use a drilling rig to dig into the ground, with the support of trucks and monitoring equipment. You may see and hear the drill operating, as well as trucks bringing materials and equipment in and out of the site.

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Work activities will take place in the following stages

  1. Weeks 1–2

    Step 1: Prepare work area

    Crews set up work area and prepare for construction.

  2. Weeks 3–6

    Step 2: Build shaft

    Crews will use a drill rig to build the shaft, an underground hole, and then install testing mechanisms. The shaft is then filled with concrete.

  3. Weeks 7–8

    Step 3: Test setup and testing

    Crews perform the load testing and collect data.

  4. Weeks 10–14

    Step 4: Restore work area

    After completing testing, crews will remove all equipment from site and restore the work area.

View a PDF version of this construction alert