August 28, 2017

Bike and pedestrian bridge over I-5 at Northgate gets a new, cheaper design

Images by VIA Architecture [enlarge]

The 1,900-foot bridge will span I-5 to connect the east and west sides of Northgate.

[enlarge]

An overlook above the wetlands is part of the design.

Ten lanes of busy Interstate 5 that separate the east and west sides of Northgate are a huge obstacle for pedestrians and bicyclists who want to cross.

The number of people who make the crossing will go up in 2021 when Sound Transit opens the light rail station just south of Northgate Mall.

The city of Seattle has a $37.5 million plan to help people make the trip safely: a pedestrian/bicycle bridge over the freeway, connecting North Seattle College with the future rail station. The project includes a new multi-use path along First Avenue Northeast between Northeast 92nd Street and Northeast Northgate Way.

The western approach of the bridge will connect to College Way North and North 100th Street, between a wetland area and the college. It will have an overlook for viewing the wetland below.

Earlier this year, the Seattle Department of Transportation had the team change the bridge design to save money.

Original plans for the bridge, by LMN Architects, were for a 20-foot-wide enclosed tube/truss structure running nearly 2,100 feet. Now the bridge has been narrowed to 16 feet and shortened to about 1,900 feet under a design by VIA Architecture. It is no longer enclosed.

Other tweaks include a redesigned east approach that doesn't conflict with WSDOT's park-and-ride at First Avenue Northeast, and a west approach with better sight lines and a more direct connection to the college. SDOT also decided to use a more traditional construction process.

Those changes shaved more than $20 million off the cost.

Planning and design work is expected to continue into 2018, with construction to start in early 2019. The bridge is set to open in mid-2020.

A general contractor will be picked in late 2018.

Here's the project team: VIA Architecture, PacificBridge (main structure), CivilTech Engineering (approach structure), CM Design Group (civil engineer), Osborn Consulting (drainage), HWA GeoSciences (geotechnical), Ott-Sakai & Associates (constructability), Clearway Environmental, Stepherson & Associates (communications), and Integrity Structural Engineering (quality assurance/quality control).

Funding is coming from the Move Seattle Levy, SDOT, Sound Transit, the state and local sources.

The $174 million Northgate Link station is expected to serve more than 15,000 passengers daily when it opens. It is being built by Absher Construction and was designed by Hewitt.