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SR 520 – Montlake Project – New eastbound bridge

The project is replacing the old, structurally vulnerable eastbound bridge. WSDOT collaborated closely with community stakeholders and the Seattle Design Commission on the design of the future bridge. It will be similar to the design of the westbound bridge.

Bridge demolition

Section of old eastbound bridge to be demolished
To be most efficient in construction — and to minimize effects on neighbors — crews use trestles and temporary work platforms along with large blue gantry cranes to remove the old bridge. Here, a concrete saw is cutting the bridge deck into pieces small enough to be trucked away.
Barriers and bins used to contain debris from bridge demolition
Debris is carefully contained in this environmentally friendly operation that reduces dust and water contamination.
Section of old bridge removed by crane
The old bridge is broken into large sections, which are transported off-site for demolition.
Removed bridge section awaits transport
Crews prepare a section of old bridge to be trucked away.
Section of old bridge and truck to transport it
Cranes lift the sections of the bridge onto trailers.
Old section of bridge loaded onto truck
Trucks transport the bridge sections off-site to be crushed and recycled.

Bridge construction on Lake Washington

Uninstalled casings for new bridge supports
Eight-foot-diameter casings are used as molds for concrete bridge supports. Each casing is specially made. They are different lengths, depending on the depth of the water and the soil type. This one has just been delivered to the site.
Supports for new bridge driven with vibratory hammer
Crews use a large vibratory hammer to install steel casings into the bottom of Lake Washington. Using this method reduces the potential for noise. Neighbors may feel vibrations as the casings are installed.
Soil auger digs into lakebed
After the casings are vibrated into the ground, soil is removed with this large auger.
Rebar cage installed for bridge supports
After the soil is removed, a rebar cage is inserted in the casing, then it is filled with concrete.
Pre-assembled bridge supports lifted in by crane
The bridge supports that we can see above water are assembled off-site and brought in for installation.
New bridge supports visible above water
The bridge starts to take shape as support structures are installed above water.

Boater safety

The Montlake Project will require crews to work both in and over Lake Washington. During certain periods of construction, cranes and other equipment will limit water access under the SR 520 bridges.

Boaters and kayakers should note:

  • At least one navigation channel will always be open to boaters.
  • When a channel or pathway is blocked, boaters should navigate through the open area.
  • Look for signs and markers to stay safely away from construction.
Map showing safe zones for boaters around construction
For safety, users of kayaks and canoes should stay at least 100 feet from active construction, as marked on this map.