SR 520 Construction Corner

The go-to source for information on SR 520 construction


Construction overview

The SR 520 Bridge Replacement and HOV Program is reconstructing SR 520 in phases, primarily working from east to west.

The next phase of corridor improvements, the Montlake Project, started major construction in summer 2019 in Seattle’s Montlake neighborhood. You can learn more about later phases of SR 520 construction in Seattle on our Rest of the West webpage.

We designed our Construction Corner webpages to make it easier for the public to learn about any SR 520 construction that’s underway or scheduled in the weeks ahead, whether it involves highway closures, detours, nighttime work, or other community effects. The Construction Corner also describes our responsibilities and protocols for limiting the community effects of our construction.

 Construction map

Wondering if SR 520 is going to be closed for construction next weekend? Or how long a detour on your local street will last? Check our SR 520 Construction Map to learn more about SR 520 construction activities that are underway or coming soon.

You also can view Montlake Project construction photos taken 'round the clock by four mounted cameras.

Major SR 520 elements upon full completion of Seattle corridor

Map of construction in the Montlake area Bicycle/pedestrian I-5 crossing Roanoke lid Improved I-5 interchange connections Portage Bay Bridge replacement Second bascule bridge Bicycle/pedestrian land bridge Montlake interchange and LID West Approach Bridge South

Montlake Project elements (started summer 2019):

SR 520 / I-5 Express Lanes Connection Project (estimated start in 2020):

Montlake Cut Bascule Bridge Project:

Portage Bay Bridge and Roanoke Lid Project elements (estimated start 2023):

Construction site

What: Improved Montlake Boulevard/SR 520 interchange; landscaped lid with open space, direct-access bus ramps, transit plaza, multimodal connections

When: Montlake Project construction started summer 2019; 4- to 5-year duration.

Where: Between Montlake Boulevard and 24th Avenue East

Examples of what to expect: Periodic highway closures; detours (vehicles, pedestrian, bicycles); noise; construction traffic; some nighttime work

NOTE: Specific construction means and methods to be determined by contractor at a future date.

Construction site

What: Shared-use pedestrian/bicycle bridge over SR 520, connecting Arboretum with East Montlake Park and University District

When: Montlake Project construction started summer 2019; 4- to 5-year duration.

Where: Approximately one block east of 24th Avenue East

Examples of what to expect: Periodic highway closures, construction traffic, noise, some nighttime work

NOTE: Specific construction means and methods to be determined by contractor at a future date.

Construction site

What: Replacement of the 1960s-era west approach bridge with a stronger, three-lane bridge to carry eastbound traffic from Montlake to new floating bridge

When: Montlake Project construction started summer 2019; 4- to 5-year duration.

Where: Between Montlake and new SR 520 floating bridge

Examples of what to expect: Demolition of old west approach bridge; pile driving in lake; barge traffic; construction of temporary work platforms in lake; periodic highway or lane closures

NOTE: Specific construction means and methods to be determined by contractor at a future date.

What: A 30-foot- wide, landscaped crossing over I-5 for pedestrians and bike riders.

When: Project construction estimated to begin in 2023; 6-year duration.

Where: SR 520/I-5 crossing along Roanoke Street.

Examples of what to expect: Some nighttime work, construction traffic, periodic temporary lane closures on I-5.

NOTE: Specific construction means and methods to be determined by contractor at a future date.

What: Landscaped lid over SR 520 in Roanoke area, with community open space.

When: Portage Bay Bridge and Roanoke lid construction estimated to begin in 2023; 6-year duration.

Where: Between Delmar Drive E and 10th Avenue E.

Examples of what to expect: Periodic highway or lane closures; detours (vehicles, pedestrians, bicycles); noise; construction traffic; some nighttime work.

NOTE: Specific construction means and methods to be determined by contractor at a future date.

Construction site

What: A new, reversible transit/HOV ramp between SR 520 and the I-5 express lanes; a modified, reversible ramp between the I-5 express lanes and Mercer Street; restriped I-5 express lanes to retain the existing four general-purpose lanes while adding a transit/HOV lane.

When: Project construction expected to begin in 2020; connection expected to open to transit as early as 2023, and open to carpools upon completion of a new Portage Bay Bridge and Roanoke lid.

Where: Between SR 520 / I-5 interchange and I-5 / Mercer Street interchange, along I-5 express lanes.

Examples of what to expect: Periodic highway closures; detours; noise; construction traffic; some nighttime work.

NOTE: Specific construction means and methods to be determined by contractor at a future date.

Construction site

What: New, seismically improved Portage Bay Bridge, built as two side-by-side structures, with bicycle and pedestrian path on the south side of the bridge; transit/HOV lanes in both directions.

When: Portage Bay and Roanoke lid construction estimated to begin in 2023; 6-year duration.

Where: Between Boyer Avenue E and Montlake Boulevard E, over Portage Bay.

Examples of what to expect: Demolition of existing Portage Bay Bridge, periodic highway closures, construction traffic, pile driving, noise, vibration, some nighttime work.

NOTE: Specific construction means and methods to be determined by contractor at a future date.

Map of HOV connection between South Lake Union and MontLake

What: A second drawbridge over the Montlake Cut, parallel to the existing bascule bridge.

When: In late 2019/early 2020, WSDOT plans to bring together project partners, stakeholders, and the public to review current transportation needs, identify potential options that will improve mobility in the Montlake Boulevard and SR 520 corridors, and discuss this project's scope.

Where: Across the Montlake Cut, to the east of the existing Montlake Bridge.

Examples of what to expect: Periodic closures of local streets, detours, construction traffic, some nighttime work.

NOTE: Specific construction means and methods to be determined by contractor at a future date.