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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.
Once preliminary engineering was complete, crews began prepping the site and building the new bridge beside the old one on temporary fixed supports. This arrangement provided crews with ample space and access to typically hard-to-reach areas. It also increased their safety to be able to work off the roadway.
When the new bridge was finished in March 2008, it was time to put all of the planning into action. For the next step, crews closed Oregon 38 for a short time — between Friday evening rush hour and Monday morning commute time — to demolish the old bridge. Despite the reduced visibility, demolition of the old bridge had to take place at night for the replacement to meet the allotted four-day timetable. At 9 p.m. on Friday, crews began cutting away the guardrails and concrete that joined the existing bridge to the substructure. In just 12 hours, the new east-side Elk Creek Bridge was ready to begin its two-hour, 15-foot journey into its new home as part of the Umpqua Highway.
The next morning, as crews finished hauling away the concrete rubble, other teams arrived to complete the next portion of the roll.
Jacking the bridges into place is a specialized engineering feat, so ODOT and Slayden chose specialty contractor Mammoet, based on the company's outstanding reputation as rapid replacement experts. Mammoet pioneered the development and use of the hydraulic skidding systems that slide the bridge into place. Rapid replacement has been used for years in Europe and is gaining popularity in the United States.
Along with Link-Belt HC-238H cranes, Caterpillar D8 bulldozers, Komatsu PC300 excavators, and road graders, Mammoet used specially manufactured hydraulic jacks, controlled by a single operator, to move the bridge down the steel tracks to its final destination. These jacks raised and lowered the new east-side Elk Creek Bridge — two spans, 222 feet long, 38 feet wide, and weighing approximately 2.5 million pounds — with two motor-driven power packs that sit on the bridge deck. In spite of the magnitude of the project, the crew also attended to small details: For example, to protect Elk Creek against hazardous spills, nontoxic dish soap was used as lubrication for the shoes on the Teflon-coated skids that the bridge slid along.
By Saturday afternoon, the bridge roll was complete. Then work began to tie in the new bridge with the existing approaches. After the heavy lifting and sliding, plenty of hard work remained as Slayden worked quickly to replace other parts of the bridge, including abutments, precast end panels and wing walls, and final concrete paving. Crews spent the next 22 hours, while the highway was closed, securing the sides in place, double- and triple-checking measurements of the east-side bridge — a two-span, two-lane concrete structure using precast, prestressed bulb T-girders and a cast-in-place, high-performance concrete deck — to be sure the structure fit together properly and was ready for traffic.
The process went so smoothly that crews reopened the bridge nine hours earlier than expected, in plenty of time for Monday morning commuters.
NOTHING SUCCEEDS LIKE SUCCESS
Later, in September 2008, crews assembled for a second time to replace the longer west-side crossing, a three-span, 320-foot-long, 38-foot-wide and 3.2-million-pound steel structure with steel-plate girders and a cast-in-place, high-performance deck. Due to the length and curve of the span, the designers opted to use steel for its lightness and flexibility.
The replacement process for the second bridge was similar to that of the first; however, because the bridge was curved, it required more complex engineering. The west-side crossing sits on a 45-degree skew, requiring careful calculations to align and attach the new span, which was designed for a gentler 30-degree angle.
One of the biggest challenges in rapid replacement is connecting the new bridge to the substructure and securing it in its final position.
The west-side bridge replacement started on a Friday evening, and by 10 p.m. Sunday the road was reopened to traffic, eight hours earlier than planned.
By selecting the design-build delivery method, valuing innovation over cost alone, and using technically difficult but effective rapid replacement, ODOT was able to keep a rural community connected and freight haulers and travelers mobile.
— Lauer is the manager of the Oregon DOT's Major Projects Branch.