The SR 520 bridge and structures are vulnerable to windstorms and earthquakes and must be replaced.
As part of the Bridge Replacement and HOV Project, crews will replace the SR 520 bridge and make other transit, HOV and community enhancements from I-5 in Seattle to the eastern shore of Lake Washington.
Project area map
What is the current status of the Bridge Replacement and HOV Project?
New! - View informational videos of the three west side design options:
The Bridge Replacement and HOV Project is currently under environmental review. As part of the supplemental draft environmental impact statement, the project team is evaluating three design options:
Option A - Most similar to today's configuration, with the addition of a second Montlake drawbridge over the Montlake Cut.
Option K - Includes a tunnel under the Montlake Cut and a single point urban interchange below the SR 520 roadway.
Option L - Includes a diagonal drawbridge over the Montlake Cut and a single point urban interchange above the SR 520 roadway.
Each option includes:
- Replacing the vulnerable SR 520 floating bridge.
- Two general-purpose lanes and one HOV lane in each direction.
- A bicycle and pedestrian path.
- A reversible direct HOV access ramp at the I-5/SR 520 connection.
- Lids at I-5 and 10th Avenue E. and Delmar Drive E.
Graphics and traffic analysis of each option are available below.
These options were developed as part of mediation process (pdf 420 kb) that included elected officials, local, federal and state agencies, neighborhood representatives, local organizations and WSDOT.
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What is included in a new floating bridge?
Conceptual graphic of the new SR 520 bridge
Regardless of which west side design option is chosen, crews will replace the vulnerable SR 520 bridge. The new SR 520 floating bridge is being designed to withstand 95 mph winds, and will also include these mobility benefits:
- Two general-purpose lanes in each direction.
- One HOV lane in each direction.
- Improved, wider shoulders.
- A bicycle and pedestrian path.
- Improved transit service.
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What is included in each option?
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Option A
Features include:
- A seven-lane Portage Bay Bridge including a westbound on-ramp at Montlake Boulevard E connecting to an auxiliary lane.
- An interchange at Montlake Boulevard E. similar to today’s configuration with two transit stops and access to and from SR 520.
- A lid over SR 520 at McCurdy Park.
- A stormwater treatment pond.
- A westbound off-ramp at Montlake Boulevard E.
- An eastbound on-ramp to SR 520 from Montlake Boulevard E.
- A transit-only direct access off-ramp to access Montlake Boulevard E. from the inside HOV lane.
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Option K |
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Features include:
- A six-lane Portage Bay Bridge.
- A lid over SR 520 at Montlake Boulevard E.
- Stormwater treatment ponds.
- Access to a tunnel under the Montlake Cut.
- A new interchange east of Montlake Boulevard E. under the SR 520 roadway, with:
- Access to eastbound and westbound SR 520.
- Direct HOV access ramps on and off SR 520 from the inside HOV lanes.
- Access to the University District through tunnel under the Montlake Cut from SR 520.
- Access to the Washington Park Arboretum through a connection to Lake Washington Boulevard E.
- A land bridge over SR 520 at Foster Island.
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Option L |
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Features include:
- A six-lane Portage Bay Bridge.
- A lid over SR 520 at Montlake Boulevard E.
- Stormwater treatment ponds.
- Access to a new bascule bridge at the east end of the Montlake Cut and south ramp connection to Lake Washington Boulevard.
- A new interchange east of Montlake Boulevard E. above the SR 520 roadway, with:
- Access to eastbound and westbound SR 520.
- Direct HOV access ramps on and off SR 520.
- Access to the University District from a new bascule bridge.
- Access to the Washington Park Arboretum through a new SR 520 south ramp connection.
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Printable diagrams of each option:
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How would traffic perform in each of these options?
The project team has performed preliminary traffic modeling to simulate traffic through the project area in 2030. View a summary document (pdf 39 kb).
Preliminary findings:
- Safety would be improved with all three options by improving the design for on- and off-ramp connections, shoulder widths, and sight distances.
- Transit service on the SR 520 corridor would be similar with all options.
- Transit travel times in the Montlake area perform the same as or better than today in most routes, with the exception of northbound on Montlake Boulevard.
- Option A would have the highest local congestion, but this increase could be reduced by including Lake Washington Boulevard on-ramps.
- Option K would provide the most improvement for local congestion.
- Option L would operate better than Option A because of the separation between freeway and local traffic.
Additional information is available below or in presentation slides available in the Program Library:
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