The US-395 Corridor Project is an effort to address increasing congestion and improve traffic movement through metropolitan Spokane. As part of the $3.3 billion highway project, the Washington State Department of Transportation (WSDOT) needed a structure to span a Burlington Northern Santa Fe (BNSF) railroad track and support a new stretch of Highway 395 above.
A conventional girder bridge was initially proposed for the project. Typically, when projects of this scope require BNSF involvement and approval, conventional beam bridges are often utilized due to ventilation concerns. BNSF requested a structure with a clearance large enough to accommodate a second railroad track in the future; however, several project factors led WSDOT and consulting engineer HDR to consider other alternatives.
The conventional bridge would have allowed for construction of just one lane of US 395 at a time over the structure. The second lane would have to be constructed at a later date, pushing back project completion time. Additionally, the curve of the railroad tracks and skew of the roadway above would have required a massivesized structure and a lengthy and complicated construction process.
WSDOT, working with Contech, began investigating prefabricated tunnel options using either a concrete or a steel plate arch system. Plans were submitted to BNSF Railway for each solution. BNSF accepted plans for a BEBO® Arch System, a buried concrete structure, which provided a number of solutions.
“BEBO offered the best crash worthiness of the tunnel options, a necessary consideration for potential train derailment inside the tunnel,” said Paul Weber with HDR, Inc. “The precast structure also allows the railroad tracks to remain in service during construction. Installation of the precast units is flexible enough to allow crews to stop work while trains are passing through, then immediately resume work once the train is past.”