41st Street Overcrossing

Everett, Washington

HWA performed a geotechnical investigation for the design and construction of a 0.5-mile extension of 41st Street, extending from I-5 over the BNSF right-of-way and onto the old Everett Landfill site.

The new roadway included a single-span bridge over Smith Avenue and a large 3-span bridge over the Burlington Northern Santa Fe (BNSF) railroad, and 8 mechanically stabilized earth (MSE) fill walls up to 30 feet tall.

For the eastern 600 feet of roadway over the old landfill, extensive evaluation of the landfill response to alternative construction methodologies was undertaken. HWA ultimately recommended that the eastern approach be constructed entirely as earth embankment, extending from the east abutment of the bridge on the west side of the landfill to the east side boundary of the landfill. Extensive analyses were performed of the landfill settlement behavior and estimates made of the magnitude and duration of consolidation and bio degradation settlements. A preload treatment program was designed for the embankment footprint and recommendations made for immediate implementation in the preliminary PS&E reporting. Close liaison with the City of Everett's environmental consultants, was provided in support of negotiations with the Department of Ecology for approvals for the preload construction, which was undertaken in 2000.

Full construction inspection was provided by HWA, including preload settlement monitoring and evaluation for a period of over 2 years. The second phase of the project, entailing construction of the bridge over the BNSF tracks and final site grading and paving, was completed in 2005.

HWA received a Gold Award at the American Council of Engineering Companies (ACEC) of Washington's 2006 Engineering Excellence Awards for Future Value to the Engineering Profession & Perception by the Public.