 Dear neighbors,
Big things are happening this month! Slurry wall construction begins in Ballard, and we're moving into Fremont.
Ballard
It's time to start our slurry wall! What does that mean exactly? You'll start to see a lot of large equipment and trucks moving in and out of the site. Here's why:
 A slurry wall is a thick, reinforced-concrete circular ring structure used to support excavation and underground construction. In Ballard, we'll use a slurry wall to support the 100-ft deep and 90-ft wide vertical shaft excavation. Our vertical shaft will eventually bring stormwater and sewage flows into the new storage tunnel and will hold pump station equipment. Initially, the Ballard vertical shaft will also be the launch point for the tunnel boring machine.
The slurry wall ring is formed by constructing 18 separate vertical panels; 9 large primary panels and 9 smaller closing panels (the primary panels are white and the closing panels are blue in the diagram above).
At a high-level, these are the steps to form a panel:
- Excavate and install guide walls to outline the future slurry wall. Guide walls are about 4-ft deep (we completed this activity a few weeks ago). In the diagram above, the guide walls are shown in green.
- Excavate in-between the guide walls down to the appropriate slurry wall depth, forming a deep and narrow vertical trench. Our trenches will be 210-ft deep and each section will take about three to four days to dig out. You can expect a slight uptick in truck traffic during this work as it'll take about 20 trucks per day to haul off trench soils.
- Fill the guide wall trench with slurry (cement mixture).
- Place a large steel rebar cage into the slurry-filled trench. This is where the crane comes in. These cages are 80-ft long!
- Pour concrete around the steel cage to form a support wall or panel (blue and white sections in the diagram) for the vertical shaft excavation. As you might imagine, filling in trenches this deep takes a lot of concrete. We'll have 18 days of big concrete pours to fill each of the 18 panels. On these days, there will be about 70-85 concrete trucks entering and exiting the site and crews will likely work longer hours. The slurry is displaced and pumped out.
- Repeat!
We anticipate slurry wall construction to take about three months. As referenced above, near-term anticipated construction impacts include:
- very heavy truck traffic on Shilshole Ave NW and 24th Ave NW; please pay attention to flaggers.
- parking restrictions along the east side of 24th Ave NW so construction trucks can exit the work site.
- noise and vibrations related to excavation and concrete pours.
Check out these photos of work that was accomplished over the past few weeks.
East Ballard
Construction in 11th Ave NW and NW 45th St (near Fred Meyer) is now anticipated to begin in late May or early June. One of the first activities you'll see is the crew setting up the Burke-Gilman Trail detour on the north side of NW 45th St.
We'll share more detailed schedule information when we're nearing mobilization. If you want a sneak peek, visit our website.
Fremont
Construction in Fremont, near NW 36th St and 2nd Ave NW, is anticipated to begin May 18. During the first few weeks of work, you can expect to see crews:
- Close NW 36th St between Leary Way NW and 3rd Ave NW and set up the construction site
- Remove trees onsite
- Remove an existing sidewalk on NW 36th St and existing utilities
- Install stormwater control and soil monitoring equipment
- Remove existing asphalt
- Install a temporary storm drain bypass
For more information, please visit our website.
Wallingford
Construction of the 12-ft screen wall is underway! See photo below taken on the site looking east. Over the next few weeks, you'll see screen wall equipment removed from the site. Additional construction activities are slated to begin at this site in August. Why the gap in schedule? To be most efficient, we used the same crew and equipment to put up our Ballard and Wallingford screen walls, but we won't be ready to begin additional activities in Wallingford for a few months.
We'll send more information about upcoming activities in Wallingford once we're closer to re-mobilization. Can't wait that long? Visit our website.
Queen Anne
Construction in North Queen Anne is planned to begin in August 2020 and will take place near West Ewing Mini Park and along 3rd Ave W.
See our latest fact sheet for more information.
COVID-19 construction update
At the City of Seattle, we are continuing to follow guidance from federal, state, and local leaders and our public health partners regarding COVID-19. State officials have determined that work on public works projects can continue during the Governor’s stay-at-home order provided that appropriate safety measures are in place.
Seattle Public Utilities is continuing with essential public works projects to the greatest extent practicable during these times. The health and safety of our workers and the public is our first priority. Our contractors have updated their Health and Safety Plans to incorporate best management practices with respect to COVID-19 throughout our construction work sites. If a situation arises where a contractor is unable to maintain these practices on a work site, or the Governor orders that public works projects must stop, the contractor shall temporarily suspend work until the work can be performed safely and legally.
We will notify you if there are any changes to the project schedule or planned work.
You can learn more about COVID-19 at www.kingcounty.gov/covid.
Additional community resources can be found at www.seattle.gov/mayor/covid-19.
Contact us
Please email SPU_ShipCanalProject@seattle.gov with questions or comments or call (206) 701-0233. You can also find information online at spushipcanal.participate.online/.
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