The Northgate neighborhood in Seattle is undergoing rapid urban development. With new and planned mixed use infill development and a new light rail station currently under construction, upgraded pedestrian and bicycle improvements are needed to better connect the surrounding neighborhoods. One key identified connection is across Interstate 5 at 100th Street N via a pedestrian and bicycle bridge. This connection will relink the western neighborhoods and North Seattle College to the future rail station, transit center, bicycle pathways, and commercial core of the area. The bridge will also become a new, iconic gateway into Seattle that will enhance the surrounding landscape and ecology.
The 2,060 foot long bridge structure will be comprised of four major components. To the east, an approach ramp and a span over 1st Ave NE will connect the structure directly to the mezzanine ticketing level of the new light-rail station. To the west, two primary highway spans will connect to a curving approach ramp that meets grade on the campus of North Seattle College.
Over its length, the structure will traverse a variety of urban, infrastructural, and ecological conditions. The bridge is designed to unite these varying environments in a singular, unified gesture, enhancing the contrast of these experiential conditions to create a unique pedestrian and bicycling experience within the city.
The structural geometry of the primary spans is made possible by the development of custom cast steel connections, designed to facilitate in the fabrication and ongoing maintenance and inspection of the structure. The resulting form is a tubular structural network that will support the twenty-foot wide walking surface while simultaneously integrating guardrails, throw barriers, handrails, lighting, and drainage systems into a singular, iconic gesture. The structural form will also serve to frame distinctive views of the surrounding context on either side of the highway; the vibrant, multi-modal transit network to the east, and the quiet, pastoral nature preserve to the west.
The project will not only reconnect the neighborhoods on either side of I-5, but will also augment the local ecological systems through an integrated landscape design. New and existing vegetated areas will accommodate an advanced stormwater management system featuring vernal ponds and swales on both sides. The project stands to substantially enhance the natural habitats of local wildlife as well as the growing pedestrian and bicycle infrastructure of Seattle.