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Super•Cor perfect for staged construction in difficult site with unusually high cover

March 5, 2014

With a “perfect storm” of challenging site conditions, it made perfect sense for the contractor to use a Super•Cor Structural Steel Plate solution in this Washington State Department of Transportation (WSDOT) design-build project in Spokane.


Lightweight, flexible and strong

That’s because Super•Cor had the flexibility to be built in two stages along with the highway twinning. Its lighter weight allowed it to be installed in a very difficult site — a deep hole unsuitable for larger machinery and heavy lifts. Plus, Super•Cor had the strength to handle the extremely high cover required.

North Spokane Corridor, US 2 Lowering - Spokane, WA 003web

Two-stage construction keeps the traffic moving

To keep the busy route open, a two-stage construction method was needed. The site’s narrow median made for exceptionally tight conditions. A temporary retaining wall was set up to facilitate the staged construction sequence.



As part of the US 395 North Spokane Corridor work, this US 2 Lowering project called for abandoning an older 10'x10' concrete box culvert at Deadman’s Creek. Using Super•Cor allowed the contractor to use smaller, lighter equipment to transport, stage and lift individual plates around the site. Also, the Super•Cor Arch’s wide-mouthed, open-bottom design facilitated fish and wildlife passage along the creek.

North Spokane Corridor, US 2 Lowering - Spokane, WA 004web

Steel was more economical than concrete, given the high amount of soil cover with the new highway. The only other option would have been some type of precast arch but the site was too difficult to work with such heavy lifts.


Designing to site-specific conditions

Big R’s engineering teams are accustomed to designing solutions for very unique sites such as this one. We provided the design for this structure, the footings, the engineered backfill zone and wire-faced headwalls and wingwalls.

More on Super•Cor »

Related Article: Big R brings speed to Missouri’s “Safe and Sound” program »



Project Name: NSC-US 2 Lowering
Location: Spokane, WA
Owner: Washington State Department of Transportation
Consultant/Engineer: WSDOT
Contractor: Graham Construction Management
Type of Product: Super•Cor Arch
Application: Fish Passage, replace 10' x 10' reinforced concrete box culvert
Dimensions: 30' span x 17.25' rise x 112' length
Installation time: Staged construction, first half October 2009, second half September 2010