Updated July 29, 2026

This page provides in-depth information about some of the larger construction efforts related to the SR 520 Portage Bay Bridge and Roanoke Lid Project. It will be updated when significant construction elements call for additional information.

Daytime regrade of Boyer Hillside begins this summer

Learn why we’re removing and replacing soil on the hillside and what to expect

Photo (looking northwest) of the Boyer Hillside just north of the existing Portage Bay Bridge. (July 2026)

What to expect

On July 22, crews began working around the clock to remove the upper layer of weak soil on the Boyer Hillside between the East Roanoke Street alley and SR 520 (near the Boyer Stairs). Crews are using excavators, bulldozers and dump trucks to remove this soil. They will then place new soil that’s better suited to support new permanent infrastructure in the area and improve the overall stability of the hillside

Community update

While Skanska originally estimated they’d need to remove nearly 30,000 cubic yards of soil, crews will now only remove 20,000 cubic yards. Additionally, soil conditions have allowed Skanska to excavate soil faster than expected. Based on this progress, along with feedback from the community, we’ve made several key adjustments to our approach. This will allow us to reduce the impacts on the community and still complete the work on time. 

We’ve updated this page to share what we’ve adjusted and what you can expect.  

Phasing: Our original approach involved doing this work in two phases around the clock. In Phase I, crews would excavate the weak soil, and in Phase II, crews would return and place new, stable soil. Starting in August, crews will begin doing Phase I and Phase II at the same time, immediately replacing soil once it’s been excavated.

Truck reduction: Crews have also made enough progress (removing 12,000 cubic yards as of July 29) that they no longer need to excavate soil at night. Starting Monday, August 3, work will shift to daytime hours and weekdays only. This includes trucking only during daytime lane closure hours of 9:30 a.m. to 3:30 p.m.

Duration: We estimate these adjustments, combined with our initial progress, can reduce the overall timeline from four months to just over two months.

Construction of the southwest work trestle: Crews will proceed with construction of the southwest work trestle with a goal of having it ready for use by mid-September. For future excavation or construction needs, we will prioritize using the work trestle as a haul route over city streets where possible.

Why are we doing this?

The Boyer hillside is a historic landslide area. Our preliminary design included installing underground landslide mitigation walls to strengthen the hillside and protect  the new bridge and infrastructure. Installing these walls requires building access roads, drilling, concrete work and excavation in the area.

After additional analysis and design, Skanska identified an improved construction method. This method removes the upper, unstable layer of soil to reduce the number of underground mitigation walls. This provides a more efficient and sustainable construction approach.

We recognize this approach differs from what we originally planned. However, we believe this construction method provides greater benefits for the community by improving hillside stability, reducing construction risk, shortening the construction schedule and decreasing the amount of permanent infrastructure required on the hillside.

Graphic showing the work area and planned route for dump trucks during these first two phases of work.

Phases of work

The updated phasing sequence is as follows:

Future phases (estimated timing 2028): Once the Boyer hillside soil removal and replacement work is finished, crews will complete a similar sequence of work under the existing SR 520 bridge between Boyer Avenue East and Delmar Drive East. We anticipate this phase of work will happen in 2028, following the completion of the new westbound Portage Bay bridge. We will share more information on this phase once it is available.

Above: Map showing the haul routes crews will use for this phase of work.

Construction effects

Truck traffic

• Neighbors will hear and see excavators and a steady flow of dump trucks while crews remove soil on the hillside. Dump trucks will enter and exit the work zone during the lane reduction hours of 9:30 a.m. to 3:30 p.m.
• We anticipate peak levels of truck traffic to be four to five trucks per hour during the above-mentioned hours. The peak number of trucks within the highest-activity 24-hour period would reach a maximum of 40 within the hours listed.
• Daily truckloads will fluctuate. Typical haul days during soil removal are expected to be fewer than 40 truck trips per day and will not occur every day. 
• While this method will increase truck traffic on Boyer for a shorter period, it is about 160 fewer daily trucks than the estimated peak Portage Bay Project construction truck traffic included in our 2011 Final Environmental Impact Statement.

Construction noise mitigation

• Using white-noise backup alarms.
• Not using compression brakes, as required in the MPPCNV.
• Lining dump truck beds with noise-abatement materials and covering the loads during transport
• Adding additional acoustic blankets around the work zone to help limit some of the noise heard by neighbors.

Additional mitigation: We’ll spray drier soils with water to mitigate dust.

Environmental review and impacts:

WSDOT and the Federal Highway Administration completed a NEPA/SEPA reevaluation of this change. The reevaluation concluded that changes from the alternative method will not result in additional effects beyond those described in the FEIS, Record of Decision (ROD), and subsequent Environmental Reevaluations. This includes effects on ecosystems, visual resources, cultural resources, noise and vibration, air quality, water quality, geology and soils and hazardous materials. You can find the reevaluation here.

Original construction method and impacts on the neighborhood

As we’ve shared, we are building the new Portage Bay bridge in a historic landslide area, with a known history of landslides dating back to the 1930s. Below is an overview of what the original construction method would have involved and its anticipated impacts on the neighborhood:

• Our preliminary design included building underground landslide mitigation walls on the Boyer hillside to protect the new bridge and stabilize the hillside. This would have required installing about 100 reinforced concrete drilled shafts into the ground. The shafts would be between four and six feet in diameter.
• Crews would first construct switchback access roads up the hillside to allow heavy construction equipment to access the new wall locations. This would require excavating the soil, which would then be trucked off-site along Boyer using the same route as the regrade.
• New steel casings – like those you see being installed for the Roanoke lid – would then be delivered by crane on Boyer Avenue. The casings would be vibrated into the ground over 100 feet. Crews would excavate the soil in the casing and haul it away by trucks on Boyer.
• Next, rebar cages would be installed in the casing and filled with concrete. This would require a concrete pump truck stationed on Boyer Avenue, with concrete delivery trucks coming back and forth on Boyer Avenue to fill the pump. It takes about a day for multiple trucks to deliver and pour enough concrete to fill one shaft.
• At minimum, neighbors would experience vibration from the casing installation and continuous concrete and dump truck traffic going to and from Boyer Avenue for at least six to nine months for this operation alone.

The alternative Boyer Hillside regrade method will reduce the number of drilled shafts from the original design by 65–85%.

Parking restrictions

To support the Boyer Hillside regrade work, we will be extending the hours of our current parking restrictions on the east side of Boyer Avenue East between East Roanoke Street and Portage Bayshore Condominiums, as well as the west side of Boyer Avenue East just south of SR 520 to Portage Bayshore Condominiums. Parking will be restricted 24 hours a day, Monday through Friday.

These restrictions are expected to be in place while we remove soil from the hillside.