TOTEM LAKE CONNECTOR
Kirkland, Washington.
BEST PROJECT
Sent by: COWI North America Inc.
OWNER: City of Kirkland
DESIGN/STRUCTURAL COMPANY: COWI North America Inc.
GENERAL CONTRACTOR: Kraemer North America LLC
CIVIL ENGINEERING: I
GEOTECHNICAL/ENVIRONMENTAL ENGINEERING: GeoEngineers Inc.
ARCHITECT/PUBLIC PROGRAMMING: Perkins Eastman (formerly VIA)
CONSTRUCTION MANAGER: David Evans & Associates
LIGHTING/ELECTRICAL DESIGN: DMD & Associates Electrical Consultants Ltd.
SURVEY AND MAPPING: 1 Alliance (now Atlas)
SUBCONTRACTORS: Malcolm Drilling; Transcon Co.; Pacific Steel Group; BendTec
A 795m bicycle and pedestrian bridge now connects to the Cross Kirkland Corridor through one of the city’s most complicated and busy intersections. The $13.6 million bridge includes five truss spans, including two over traffic, while another six spans form the north loop ramp over the wetlands.
Commercial development surrounds the project site, which has been identified for possible future transit facilities. The connector grade separates this path from traffic and includes a 14-foot bridge deck, as well as a wider rest area above the traffic island at the intersection. It’s also an example for other adjacent cities, which are following in Kirkland’s footsteps to create a continuous path along the corridor.
Levels and approach layouts were established to provide a constant and gradual slope for pedestrians and cyclists while minimizing impacts on the environment and other infrastructure. Vierendeel’s arched armors are composed of pipe members, with the armor planes unfolded to minimize the footprint below the deck.
Photo courtesy of David Evans & Associates
Previously, the intersection was a major impediment to trail users and the redevelopment of the neighborhood was just beginning. From the beginning of the design, the project team had to address a multitude of site constraints, including property access, a wetland, ditches, existing buried utilities, and multiple power transmission lines aerial The congested site also had heavy traffic and potentially hazardous materials from an abandoned railroad. The team developed an alignment to avoid major conflicts with each of these elements.
To minimize impacts within the wetlands, steel Y-piers were designed on individual drilled shafts, allowing for site-wide planting and restoration. Although a smaller sanitary sewer was relocated, the north buttress was designed around a critical Northshore Utility District sewer that remained in place.
Photo courtesy of COWI North America Inc.
Meanwhile, keeping the loop ramp light helped significantly with seismic design because the soils throughout the northern loop ramp were poor and subject to liquefaction and lateral spread during an earthquake. The design took advantage of the geometric stiffness of the loop ramp and rigid north buttress to keep pier footprints small.
The design team saw an opportunity with retaining walls throughout the approaches to put sustainability at the forefront of the design. Instead of traditional concrete-faced walls, the team chose mechanically stabilized earth (MSE) walls with vegetation, which also allowed for the installation of stormwater infiltrations under the approaches. The approaches were also paved with porous hot mix asphalt (HMA) to reduce the amount of runoff. Two stormwater infiltration ponds are located under bays one and three.
Photo courtesy of COWI North America Inc.
Ensuring pedestrian comfort in the long stretches of such a slender structure was another challenge. The gangways extend 20 feet outside and 12 feet inside the loop ramp deck, centered on the pier closest to the wetlands. Although not commonly used in transportation structures, the solution was to leave room at the end of each gazebo for vibration dampers, specifically calibrated to prevent the build-up of pedestrian-induced vibrations.
