Ames Lake Trestle Bridge Replacement Project

Project overview

This project replaces the 100-year-old Ames Lake Trestle Bridge with a wider structure and straighter bridge approaches. The improvements are designed to increase sight distance for drivers and provide a safe, unrestricted crossing for trucks and vehicles of all sizes. In addition, the new bridge will be designed to have less environmental impact on Ames Creek and the surrounding wetlands.

The new bridge is being built in the same location as the existing bridge and will have no weight restrictions. The road will be closed for the duration of the new bridge construction and traffic must use an alternate route. Construction began on June 24, 2024. The new bridge should be mostly complete in early March 2025.

The bridge crosses Ames Creek on Ames Lake-Carnation Road NE, in rural unincorporated King County between Redmond, WA and Carnation, WA. View larger image (347KB)

Why is King County replacing the bridge?

The Ames Lake Trestle Bridge was built 100 years ago and was originally designed with narrow lanes for much smaller vehicles compared with what we see on the road today. The bridge has a posted weight restriction for specific large trucks and specialized hauling vehicles. Replacing the bridge will provide a safer, unrestricted crossing for the community.

The original timber piles that support the deck are decaying. Over time, the poor condition of the piles could prohibit large trucks and emergency vehicles from crossing, which eventually would require the bridge to be shut down completely.

Project timeline

Summer 2024:

• The project began on June 24, 2024. It will take approximately eight (8) months to complete.
• During construction, Ames Lake-Carnation Road NE, between W. Snoqualmie Valley Road NE and NE 52nd Street, will be closed to all vehicles, bicycles, and pedestrians at the bridge location. 
• There will be no posted detour as there are many alternate routes available in the area. All traffic, including emergency vehicles and school buses, must use an alternate route for the entire eight-month-long construction period. The project team will notify Google Maps of the closure. 

Fall 2024 thru winter 2025:

• The bridge will be under construction and closed to all traffic, including emergency vehicles and school buses, through early March 2025. 
• The new bridge is anticipated to be complete in early March 2025.

Spring 2025:

• Major construction complete.

Map of alternate routes to use during construction

The roads shown in purple above are all the alternate routes that can be used when Ames Lake Trestle Bridge is under construction. About 1,900 vehicles cross this bridge daily and there is no official detour route for this project. We are coordinating with school districts and emergency services. Additionally, WSDOT is aware of the project, and we will monitor conditions.   View larger image (946KB)

What to expect during construction 

The project team is protecting the trees in the creek and will work to prevent dust and dirt caused by construction work from spreading in the air.  In addition, people living near the work area might experience the following while the bridge is being removed and replaced:

• Noise and odor from sawcutting, jackhammers, excavators, generators and pumps.
• Trucks hauling materials to and from the construction site. 
• Large construction cranes in the roadway. 

After the new bridge is opened to traffic, crews will continue low impact restoration work including plantings and site clean-up.

Future bridge layout

The new Ames Lake Trestle Bridge will be wider, straighter and safer than the existing bridge. There also will be improved visibility for oncoming traffic. All of these improvements will allow those coming out of adjacent driveways to see farther down the road. 

The new bridge will be in the same place as the existing bridge. Building it in the same spot requires less ground shoring and leveling (grading). It also minimizes the size of the retaining walls that will be required.

Environmental improvements

The new bridge is designed to minimize and prevent environmental impacts on Ames Creek and the surrounding wetlands.

This project will:

• Improve fish and wildlife habitat.
• Improve water quality.
• Reduce erosion.

Project budget

The estimated cost of this project is $10.8 million. It is funded through local King County sources.

Photos

October 2024 – A crewmember uses a vibrating compactor to apply even pressure and compact the fill behind the wall reinforcement panels. This helps make the soil stronger by bringing its particles closer together, increasing friction between them when pressure is applied, and reducing unwanted sinking or settling. 

October 2024  – Crews place structural earth wall panels along the edges of the bridge approach. These panels help hold the soil in place, prevent erosion, and provide a stable base for the bridge by distributing the weight evenly.

October 2024 – Crews build wood formwork on the north abutment wall. This wall will perform the important duties of connecting the northern bridge approach to the bridge and channeling the force of moving objects on the bridge to the ground. 

October 2024 – A crewmember inspects the foundation for the northern abutment wall, which is comprised of three buried 5-foot diameter concrete shafts that extend 60 feet into the ground. The deep structure is topped off with concrete, and crews will begin building up the abutment wall after the concrete cures. 

October 2024   – The wood forms of the southern abutment wall, which contained the concrete as it hardened, has now been removed. This wall is strong and stable, and ready to support the new bridge approach. 

September 2024 – Another view of the south facing abutment wall. The wall also functions as a retaining wall, as it stands between the approach embankments and the bridge structure.  

September 2024 – Crews built the frame for the south abutment wall of the new bridge.

September 2024 – Crews build the foundation for the southern abutment  wall, which will be more stable after it is filled with concrete. Abutment walls perform a very important role in a bridge’s supportive foundation by transferring the weight of the structure & traffic to the ground.

August 2024 – Large steel pipes, known as “telescoping casings,” are installed into the drilled shaft with a crane. These pipes help to prevent the deep soil from caving in after the opening has been drilled. 

August 2024 – Crews use a giant drill to dig 75 feet deep in the earth. This is the first of three shafts that will be drilled on each side of the bridge. 

August 2024 – Plastic tarps cover both slopes to protect existing soil and prevent erosion caused by weather. The orange fencing serves a similar function by blocking erosion from entering the stream. 

August 2024 – The project’s stream restoration is complete and ready for native spawning fish this fall. This work included the strategic placement of large logs to slow rushing water and mimic the natural flow of the stream. 

July 2024 – Crews take the final major step in bridge demolition by removing the existing creosote-treated timber piles. 

July 2024 – Crews have been careful to protect the wetlands below the bridge during construction. The tarping under the bridge helps to control erosion and reduce disruption to the environment. 

Two engineers inspect the Ames Lake Trestle Bridge from the bucket of an under-bridge-inspection-truck (UBIT) truck.

One of three official blue and yellow Ames Lake Trestle Bridge Project information signs located along Ames Lake-Carnation Road NE. Photo taken in November 2023.

A view of the Ames Lake Trestle Bridge as seen from Ames Lake-Carnation Road NE while heading south toward NE Union Hill Road. The bridge’s complete wooden support system, which spans the creek, remains hidden beneath the road and out of view from passing traffic. Photo taken in November 2023.

Most vehicles weighing more than 19 tons are currently too heavy to cross the Ames Lake Trestle Bridge. This sign, pictured above, provides details about which types of trucks are restricted from using the bridge. The new replacement bridge will not have any weight restrictions. Photo taken in November 2023.