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State Route 520 Montlake Project online open house – Construction activities

Sidewalks and trails during construction

There are many trails and sidewalks to use during construction, and we do our best to limit interruptions and detours. Please practice social distancing and stay six feet away from other users while on the trails. Crews are required to adhere to specific safety protocols that help ensure the health and safety of workers on site.

There will be intermittent closures and detours as needed. During construction:

  • The 24th Avenue East bridge is closed to pedestrians and bicyclists and will reopen as part of the new Montlake lid. Detour routes are currently available along Montlake Boulevard East and on a temporary path under SR 520.
  • The Foster Point Trail tunnel under SR 520 will be removed in early 2021, though the trail will remain. The new bridge will be elevated and will not require a tunnel for the trail crossing underneath.
  • The Bill Dawson Trail connection is expected to be closed for several weeks in early 2021 to prepare for the trail tunnel under Montlake Boulevard.
  • The section of the SR 520 Trail along the Montlake Boulevard westbound off-ramp may occasionally be closed or narrowed. Use caution and watch for signs.

The sidewalk on Lake Washington Boulevard between Montlake Boulevard and 24th Avenue East is expected to be open through the end of the year while work at the intersection of Montlake and Lake Washington boulevards is inactive. Closing the sidewalk made space to work on a 54-inch water line under SR 520. Crews used a method called “jack and bore” to drill an underground hole horizontally between two points. This method reduced the number of full SR 520 closures and disturbances above ground. Work will continue in this area in early 2021, resulting in sidewalk closures.

54-inch water line map


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.

Boater navigation map


To help drivers get to where they’re going during construction, we opened a temporary eastbound on-ramp from Lake Washington Boulevard to eastbound SR 520 in fall 2019. The ramp will be open until summer 2022.

Closures on SR 520 and local streets will usually be at night and on weekends to avoid creating traffic backups. Drivers should expect intermittent daytime lane closures on neighborhood arterials, as well as on the ramps to and from SR 520 during off-peak hours. For the most up-to-date information about road and highway closures, visit the SR 520 Construction Corner.

Shifting traffic for the Montlake lid construction

In fall 2019, crews shifted traffic to make space to build the central support wall of the future Montlake lid.

By summer 2020, the central support wall was in place, and crews shifted traffic close to it to make space to build the exterior support walls. That’s the traffic configuration we’re in now.

The next major shift will be in spring 2021, when crews will move both Montlake Boulevard and 24th Avenue East onto the new Montlake lid. This will give them space to remove and reconstruct both the Montlake Boulevard and 24th Avenue East overpasses. Part of that work involves closures of SR 520 to deliver and set large, heavy girders to support the overpasses.

Traffic shift 1
Traffic shift 2
Traffic shift 3