To watch a video of this project, visit the “article links” page under “resources” at www.pwmag.com.
The Oregon DOT (ODOT) replaced two bridges with only two weekend closures rather than rerouting traffic or causing delays for six months with single lanes. Motorists, stakeholders, and community members in nearby Elkton — population 150 — were happy with the process.
In 2003, the Oregon Legislature enacted the third Oregon Transportation Investment Act, or OTIA III, and charged ODOT with outsourcing the delivery of a 10-year, $1.3 billion program addressing 365 aging highway bridges. Oregonians have not seen an investment of this magnitude in highway and bridge construction since the state's interstate freeway system was built in the 1950s and '60s.
To implement the OTIA III State Bridge Delivery Program, we at ODOT made a monumental shift to overseeing program management. It is just one of the innovations on a program that is repairing and replacing hundreds of aging highway bridges across the state.‘GREASING THE SKIDS' WITH RAPID REPLACEMENT
Through standard testing, ODOT identified bridges across the state that needed to be repaired or replaced to prevent future freight restrictions. Five of those bridges are on Oregon 38 near Elkton, between Interstate 5 and the Oregon coast. To maintain mobility in the region, ODOT decided to replace all five bridges. Because of the topography, we faced several challenges, particularly on two of them: the 80-year-old bridges on either side of Elk Creek Tunnel.
All five bridges traversed difficult terrain, with steep gorges and winding roads. The two bridges built close to the tunnel portals were within 38 feet and 180 feet on the east and west sides, respectively. Finally, the 1,000-foot-long tunnel sits in the middle of a vital freight corridor connecting several small communities, most significantly nearby Elkton.
While planning the project, our engineers also noted that single-lane closures at the curved tunnel would not only be inconvenient, causing several months of one-lane traffic at the bridge, but could be dangerous to workers and motorists due to the lack of visibility. After identifying these challenges, we decided to prioritize freight and traffic mobility plans when selecting the winning proposal.
The design-build contracting method has several benefits including that crews can begin construction before design is finished, allowing projects to be completed faster than the traditional approach. By using design-build, we were able to identify a project team that would provide an innovative solution to deal with these unique circumstances. We solicited bids and, rather than basing our decision primarily on the lowest price as we do with traditional contracting methods, we modified the selection criteria and based 60% of our decision on the contractor's qualifications and 40% on the pricing estimate.
After examining several alternatives, we chose Slayden Construction, which proposed using a type of rapid replacement and promised a substantial public involvement component. With this type of rapid replacement, crews build a new bridge beside the old one, which remains open during construction. After the structure is completed, the old bridge is moved out of the way using hydraulic jacks, and the new structure takes its place.
Oregon 38 is a vital freight route connecting the central valley with the Oregon coast, which has an annual average daily traffic volume ranging between 4,000 and 5,000. Extensive road closures on this two-lane highway would have required significant delays, including a potential 100-mile detour. Slayden's approach reduced the amount of time the bridge was closed from ODOT's allotted six months to only four days — significantly reducing the disruption to traffic and the nearby community.
Although the upfront cost of Slayden's proposal was higher by approximately $900,000 than that of other bidders, this solution prevented extreme disruptions to traffic flow in the area.
Because rapid replacement was a more expensive solution, ODOT applied for and received a $1 million Federal Highway Administration grant to help cover the additional costs. The Federal Highway Administration's Highways for LIFE program provides state agencies with additional federal funding on projects employing unique solutions to minimize mobility issues and maximize community involvement.
T.Y. Lin International, the design consultant, had to consider both the size of the bridge as well as how it would fit into the existing alignment and substructure.