This program replaces an existing diamond interchange at NE 116th Street and I-5 with a new single-point urban interchange, providing much needed capacity and safety improvements. Major elements of the project included replacing a three-lane bridge with an eight-lane, 150-foot-long bridge over I-5, realignment of 34th Avenue NW and Quil Ceda Boulevard, realignment and restoration of Quilceda Creek through the interchange, two new 18-foot-diameter fish passable culverts, a new two-lane 125-foot-long bridge over Quilceda Creek, a new roundabout, retaining walls, noise walls, stormwater treatment ponds, LED street lighting, and new signal systems. Parametrix led and performed the design, environmental documentation, and permitting. Responsibilities included:
- Traffic analysis and preparation of an IJR
- WSDOT Channelization Plans for Approval
- Geometric design
- Interchange alternative analysis
- Stormwater treatment and infiltration design
- Signal and illumination design
- Structural design
- Public involvement and project stakeholder coordination including FHWA, BIA, WSDOT, Snohomish County, Community Transit, and City of Marysville
- Environmental assessment, NEPA and SEPA documentation
- Biological assessment, stream and wetland design, and wetland mitigation site design
- Preparation of PS&E to WSDOT standards
- Construction management
The bridge over I-5 is a two-span, precast, prestressed, concrete girder bridge. Because of poor soils and the potential for liquefaction during a seismic event, the foundations consist of 8-foot-diameter shafts extending 100 feet deep. This regionally significant project was built in phases to match funding availability while making incremental improvements without throwaway work between phases. The majority of the project costs were funded through leveraging grants and other nontribal funds.
