SR 520 Construction Corner

The go-to source for information on SR 520 construction

Note: The Construction Corner's current content is for testing purposes only and may change before this site goes live.

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Construction overview

We are reconstructing SR 520 in phases, primarily working from east to west. The next phase of corridor improvements will be in the Montlake area. We expect Montlake Project construction to start in early 2019. 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.

 Current construction

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

Major SR 520 elements upon full completion of Seattle corridor (estimated 2027-2029)

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 (estimated start early 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 expected to begin in early 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 expected to begin in early 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 expected to begin in early 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.

What: Construct a reversible lane dedicated for buses and carpools between the SR 520/I-5 interchange, the I-5 express lanes to downtown Seattle, and the Eastside.

When: Portage Bay Phase construction estimated to begin 2020 to 2022; 6-year duration. TBD by contractor

Where: SR 520/I-5 interchange

Examples of what to expect: Demolition of portions of the existing E Roanoke St overpass, periodic closures of SR 520 and local streets, detours, 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. WSDOT is working with the city of Seattle and community stakeholders to refine the new bridge’s design.

When: WSDOT is working with the city of Seattle and community stakeholders to determine project timing.

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.

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.