by TIM BOND
Tuesday night SDOT held an open house for the proposed Northgate Station pedestrian bridge. It showcased three design alternatives and provided a brief funding update. The bridge itself will be 15-20 feet wide and have an overall length of 1800-2200 feet depending on the alignment. The trek from the station to College Way would be about 1/4 mile; the current trip is about 1.2 miles via either the north on Northgate Way or via the south on 92nd. 7,000 daily crossings are expected once Lynnwood Link comes online. The student population of North Seattle Community College is 14,000 plus about 400 staff. The bus stops in front of NSCC see about 600 daily riders today.
The bridge will connect at three points: ground level on the west side of I-5, ground level on the east side and at the mezzanine level of Northgate Station. For the west side there are two options: at the end of 103rd at College Way (W1) and at 100th (W2). For the east side: 1st and 103rd (E1), 1st and 100th (E3) or half way between the two (E2).
The bridge deck will be about 40 feet off the ground and the western approach would gently slope down. The east approach will cloverleaf and touch down on the west side of 1st. A cycle track is to be constructed running on the west side of 1st between 103rd and 92nd. A multi-use path is being constructed on the east side of 1st from 103rd to Northgate Way. There is a planned, unfunded greenway along 100th between College Way and Fremont Ave.
Design option 1: Cable stayed bridge
This option is the most minimalist in design, using a V-shaped center column. A local example (on a much larger scale) is the SR-509 bridge in Tacoma. The artist’s rendering does not include the WSDOT-mandated throw barrier, which will likely add visual clutter.
Design option 2: Tied arch (like the DNA bridge)
The artist’s renderings only show the tubular structure; the final result would likely end up looking like Elliott Bay’s Helix Pedestrian Bridge–complete with screens and all.
Design option 3: Tube/truss
This option looks somewhat like a Chinese finger trap. Of the three designs, this is the only one with any allowance for overhead weather protection. The design is more enclosed than open, which would more seamlessly integrate the throw barrier.
Current estimates put this project at $25m. SDOT and ST have each committed $5m but ST will put their portion towards other improvements that if a funding agreement isn’t secured by July 31, 2015. In April, the city, Metro, ST, WSDOT and NSCC requested a USDOT TIGER grant for $15m and should be hearing back in a few months. If the grant is not awarded, the city will continue to pursue other grants (and may apply for another TIGER grant next year). SDOT had no clear plan if the ST deadline expired with incomplete funding.
SDOT will release a refined list of proposed alternatives in the fall and a report with a preferred bridge type and alignment at the end of the year.