Photo looking South at the Lower Duwamish Waterway. South Park Bridge is shown in the distance. Shoreline is busy with ships and industry.

Construction News

We Are Cleaning Up the Lower Duwamish Waterway

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The second season of cleanup construction for the upper reach is complete!

Project contact information:

1.888.561.LDWG (1.888.561.5394)

What’s happening now:

August 2026 update

LDWG is preparing to begin the third season of construction in the upper reach of the waterway to remove contaminated sediment. To protect certain fish species, in-water construction will occur October 2026 through February 2027.

Starting as soon as October 1, the construction contractor, Pacific Pile and Marine, will begin dredging contaminated sediment near parks and homes in South Park. The community can expect multiple barges and equipment working on the water, lights for safe work during dark hours, and typical construction equipment noise.  Season 3 construction hours will be during both daytime and nighttime, Monday – Saturday. Hours will vary depending on the tides and the type of work being done.

We do not expect this season’s construction work to require extended South Park Bridge closures. Extended bridge closures are when the bridge is closed to people driving, walking, or biking for a longer duration than what is needed for routine bridge openings for vessel passage.  

The sediment cleanup is organized into Sediment Management Areas (SMAs). At one cleanup area, SMA 5, cleanup work will be done from private property on land, instead of from the water. SMA 5 is just north of Slip 6. When work happens at SMA 5 later this season, there may be short-term impacts or closures to the public sidewalk that is next to the cleanup area. This is to keep the public and crew safe. We will let the community know in advance about this work. 

Follow along with weekly construction updates by signing up for LDWG’s Email Newsletter.

Read the Season 3 Construction Handout: English | Spanish | Khmer | Vietnamese

You can reach out to our team should you have questions or concerns. Reach out to us at info@ldwg.org or 1-888-561-LDWG (1-888-561-5394).

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Lower Duwamish Waterway Upper Reach Cleanup Areas

As of March 6, 2026

Map of the Upper Reach of the lower Duwamish waterway that shows sediment management areas (SMA). This map shows SMAs that are colored green are completed cleanup areas. SMAs that are grey will be worked on in a future construction season.

What to Expect During Construction

Construction will take place in specific areas within the waterway’s upper reach, which extends from the South 102nd Street bridge downstream to the Duwamish Waterway Park.

In general, the public can expect to see:

  • Construction equipment working on the river, including tugboats, excavators on barges, and barges carrying material to and from work areas. 
  • The contractor will use barges to move dredged sediment from cleanup areas to the Duwamish Reload Facility (operated by Waste Management) located at 7400 8th Avenue South to transfer sediment from barge to railcars. The material will then be transported to a regulated landfill.  
  • People in smaller boats observing, doing surveys, monitoring water quality, and collecting samples.  
  • Lights for safe work during dark hours and noise related to construction equipment. 
  • Construction happening during both daytime and nighttime hours, with schedules shifting based on tides and the type of work being conducted.

Construction photos

A piece of construction equipment on an empty barge.
An empty barge at SMA 12B (Geosyntec, March 2, 2026)
Photo showing sheen recovery crews adjusting and maintaining oil-containment booms and bubble curtain used to capture and manage sheens observed as a result of dredging SMA 12B. Image shows three vessels, a boom on the water, and building in background. Looking north.
Sheen recovery crews adjusting and maintaining oil-containment booms and bubble curtain used to capture and manage sheens observed as a result of dredging SMA 12B (King County, January 23, 2026).
Photo of three people wearing safety vests. The people are looking at sediment core samples on a table. They are outside.
Crew processing sediment core and preparing samples for laboratory analysis to verify that contaminated sediment has been adequately removed (Geosyntec, December 27, 2025).
Photo of barge on waterway with two piles of large, clean rock.
Clean rock for the third and final layer of the engineered cap at SMA 12B (Geosyntec, February 26, 2026)

About the Construction 

King County, as a member of LDWG, hired Pacific Pile and Marine as the lead contractor to carry out cleanup construction in the upper reach.  

Construction in the upper reach is taking place during the construction season over three years, ending in February 2027. The construction season is typically October through February each year. In-water construction activities are restricted to these months to protect certain fish species.  

Since fall 2024, LDWG has removed nearly 80,000 cubic yards of contaminated sediment from the waterway, filling 1,129 railcars. In total, 17 of the 26 sediment management areas are now complete following Season 2.

After the Lower Duwamish upper reach cleanup is complete, construction will continue downstream toward the south end of Harbor Island over the next decade. You can read more about the pollutants we will clean up from the river on our About the Contamination page.

Learn more about the Lower Duwamish Waterway Superfund Site cleanup on the EPA website. 

Planned Construction Activities

You can expect the following construction activities:

  • Staging of equipment and materials: Setting up, organizing, and storing materials before use in construction.
  • Offloading: Transferring materials like dredged sediment from one mode of transportation to another, such as from a barge to a truck or train.
  • Transporting materials: Transporting dredged materials and debris from one location to another, including by barge, rail, or truck.
  • Disposing of contaminated materials: Disposing of contaminated materials at a permitted commercial landfill.
  • Surveying and inspections: Documenting the condition of the work sites and surrounding areas, as well as the progress of construction before, during, and after construction (including taking photographs).
  • Removing piling and debris: Temporarily removing the piling that supports Tribal fishing, removing piles no longer in use, and removing any debris from dredged areas.
  • Installing replacement piling and reinforcing structures: Replacing any Tribal fishing piling that are temporarily removed for construction access. Reinforcing any shoreline bulkheads to allow dredging next to the bulkhead.
  • River sampling: Collecting water samples to confirm that dredging is being conducted as required, to comply with water quality standards.
  • River sediment sampling: Collecting sediment samples to confirm dredging has removed the contaminated sediment as required.
  • Site cleanup and demobilization: Removing construction equipment and materials from the work site.

Communications and construction timeline for the Upper Reach

Timeline overview from 2024 to 2027:

  • Contracting and Bid: Q1 2024 – Q2 2024
  • Contractor hired: Q3 2024
  • Construction Submittals: Q3 2024
  • Pre-construction Outreach: Q3 2024
  • Construction Season 1: Q4 2024 – Q1 2025
  • Construction Season 2: Q4 2025 – Q1 2026
  • Construction Season 3: Q4 2026 – Q1 2027
  • Ongoing Community Outreach and Communications: Q4 2024 – Q1 2027

How EPA, LDWG, and the contractor will work to reduce the impact of cleanup construction on the community.

LDWG and the construction contractor, with the oversight of the EPA, will work to learn about and mitigate community concerns as practical through digital and in-person outreach such as responding to project emails and the project phone line, and by speaking with people at community events.

We are dedicated to limiting the impacts of construction on those who work, live, play, and gather in the area.

We welcome the community to contact the Cleanup Outreach Team with any concerns related to the cleanup. You may reach us via email at info@ldwg.org or by phone at 1-888-561-LDWG.

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