Technical Description:
• BEBO
® Bridge Concrete Arch System
• Span: 54’
• Rise: 26’-4”
• Length: 48’
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A structure crossing Wildcat Creek along U.S. Highway 12, the southernmost route across the Cascade Mountains in Rimrock, Washington, was deteriorating and needed to be replaced. Originally constructed in 1936, the original concrete structure was in ill repair and it was no longer feasible to continue patching the large holes forming in the bridge deck. Since U.S. 12 is a busy thoroughfare, Washington State Department of Transportation (WSDOT) decided that the project would best be served as a Design-Build replacement project. It was imperative that a replacement bridge be installed as quickly as possible while also minimizing impact on the traffic, the community and the environment.
"WSDOT wanted work done by October before weather made construction too difficult," stated Richard Patterson, Design Manager with Stantec. "They needed something fast... that kept us away from a lot of cast-in-place work; we couldn't wait the week to 10 days for concrete to cure. So we went with precast."
As stated above, a cast-in-place concrete bridge was considered but, in the end, it was decided that a 54' span x 26'-4" rise BEBO® Bridge Concrete Arch System, 48' in length with precast MSE walls from Reinforced Earth Company (RECo), was the best solution for its ability to meet all of WSDOT's demands. The precast buried structure option not only saved time during the installation but it also reduced the budget by $4 million. Additionally, the precast option offers better quality control since it is manufactured off site and a smaller footing than a conventional bridge. The large clear span inherent in the design reduces settlement, contamination and impacts to Wildcat Creek, while providing passage for fish and other wildlife. Long-term benefits include less maintenance and at a initial cost savings.
In order to minimize impact on motorists and road closure times, the original plan to install a temporary bridge was nixed and instead, the road was closed fully while the original structure was demolished and the new structured was installed. This new buried structure option meant that the road was closed for only 17 days rather than three months. In fact, the most challenging part of the project was the careful planning to ensure that all of the precast units arrived on the site in the correct order. Just a week before the road closure was scheduled to begin, a local forest fire caused a month long delay so the deliveries were rescheduled.
Eliminating the need for a temporary bridge and decreasing the length of construction resulted in a positive effect on the surrounding environment as well. In-water work was minimized and many trees and an owl habitat located adjacent to the habitat was left undisturbed. Since fewer materials were used, there was less waste. Furthermore, fewer trucks were needed to transport the precast concrete arch bridge sections to the site in relation to a cast-in-place option, reducing the carbon footprint of the project.
"WSDOT is pleased with the results of this bridge replacement," concluded Scott Golbek, WSDOT's Project Engineer. "This is the first Design-Build administered project for the South-Central Region. The goals established for this project, including minimizing impacts, collaboration and environmental compliance, have all been successfully met."
This project received numerous awards including recognition by Roads & Bridges magazine as one of the 2019 Top 10 Bridges, the Associated General Contractors (AGC) of 2019 Washington Highway Transportation under 5 Million Build Washington award, the WSDOT/AGC 2019 Partnership for Excellence in Contract Administration Statewide Design-Build less than $30 million award and the American County of Engineering Companies (ACEC) Best in State: Gold award for unique or innovative applications.
Technical Description:
• BEBO
® Bridge Concrete Arch System
• Span: 54’
• Rise: 26’-4”
• Length: 48’
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