WILLAMETTE RIVER BRIDGE REPLACEMENT
Location: Eugene, Ore.
Owner: Oregon DOT
A&E firm: OBEC Consulting Engineers, Eugene, Ore.
Contractor: Hamilton Construction, Springfield, Ore.
Budget: $204 million
After serving West Coast travelers for nearly 50 years, the Interstate 5 bridge over the Willamette River in Eugene, Ore., was in dire need of replacement. During a preliminary inspection in 2002, Oregon DOT engineers identified shear cracks severe enough to require posting weight limits; heavy-haul trucks had to be rerouted 200 miles around the structure until we could complete a temporary replacement in 2004.
Part of the $1.3-billion, 10-year Oregon Transportation Investment Act III State Bridge Delivery Program, the new bridge was going to be a complex project for a number of reasons. Not only is it the largest bridge replacement in our history, it also had the potential for major environmental and community impacts. The new bridge will span nearly 2,000 horizontal feet, 700 of which cross the river. It's flanked by parks on either side and serves two communities with highly engaged residents: Eugene and Springfield.
The National Environmental Policy Act (NEPA) required us to prepare an environmental assessment for the new structure. By the time the finding of “no significant impact” was signed, we had approximately five years to complete design and construction within the state program's legislatively mandated deadline. We had no choice but to accelerate the construction schedule.
We could have used design-build contracting to speed up delivery, as we have on hundreds of bridges across the state, but that would have meant sacrificing control over design decisions.
After analyzing the various procurement methods and researching projects done by other state agencies for vertical construction, we chose to use construction manager/general contractor (CM/CG), otherwise known as construction manager-at-risk (CM@R), for the first time.
Knowing that the Oregon Administrative Rules accommodate alternative contracting methods, we began to assemble an exemption proposal that would meet its requirements, which include ensuring fairness to the contracting community, not hampering competition, and providing value to the state.
To ensure the construction industry was on board, we discussed the concept with members of the Associated General Contractors and the American Council of Engineering Companies. Based on their input, we developed an exemption application that met state criteria and secured signed contracts with the design firm and contractor by the time of the NEPA finding, leaving us poised to start design work almost immediately.
Procurement through CM/GC
Because the design firm and contractor would work in tandem with us for the length of the project, we needed to select the strongest possible team. Unlike design-bid-build, which awards the contract to the lowest-price bidder, contractors don't provide a traditional bid. Other values influence the selection. When evaluating the prime contractor candidates, we looked at organization and key personnel expertise; understanding of CM/GC roles, responsibilities and goals; and proposed project approach in addition to bid value.
The partnership between the owner, architect/engineer, and contractor depends heavily on their qualifications and, more importantly, on their ability to collaborate. If one isn't a good partner, the process suffers. Our contractor, Hamilton Construction, and our architecture and engineering (A&E) firm, OBEC Consulting Engineers (OBEC), have been outstanding partners.
In the CM/GC method, the prime contractor is involved throughout the process, giving the A&E firm and the owner input on the design as it evolves. By working with us and our consulting engineers throughout the design phase, Hamilton Construction helped ensure the chosen design would play to its strengths, making the bridge easier to build and ultimately giving us greater value for our investment.
Though we're only halfway finished with the project, this constant collaboration has proven its value several times.
As we developed the type, size, and location of the new bridge, our dynamic public involvement process required immediate responses about construction impacts and pricing. Hamilton quickly and accurately provided us information to keep engagement moving forward. This same interaction carried us into the local, state, and federal permitting processes, allowing us to move quickly into building the initial structure: the temporary work bridge.
During design, the community wanted to weigh in on the new bridge style. Hamilton provided input on cost, schedule, and feasibility; OBEC modified the design based on community needs. The resulting deck-arch design pleased both the CM/GC team and local stakeholders.
We used CM/GC to manage risk and control costs. In design-build, the owner mitigates, accepts, or passes risk on to the contractor. If the owner decides to pass the risk on, the contractor has to price it. With this project, Hamilton Construction stripped a lot of risk from the price, and we held the price of risk as a contingency, which lowers the price. If the risk materializes, we'll expend the funds; if not, we'll keep them.
CM/GC also reduces the number of change orders, largely because the contractor is involved in the project design. The conditions associated with the construction are clear, risks are identified and appropriately assigned, and the design is tailored to the contractor's capabilities.
Hamilton took a huge change in stride when finishing the arches on the southbound structure of the bridge. True arches theoretically experience only compression, no bending forces. This project doesn't have true arches — their rise is too flat. To minimize bending forces and induce compression into the arches, our design calls for the arch halves to be jacked apart at the peak.
The jacking forces and distance were calculated; however, when executed on the southbound bridge arch spans, the distance was different than anticipated, causing changes to the spandrel columns that support the deck. With design-bid-build, the contractor would consider that a change and expect compensation. Anticipating the possibility, Hamilton could adapt without requesting a change in compensation or time, which kept us on time and on budget.
Three lessons learned
We've already learned a number of things that will make our next CM/ GC project that much more effective:
The Federal Highway Administration (FHWA) holds CM/GC Peer Exchanges and provides data on implementing the CM/GC contracting method. For more information, contact the FHWA Innovative Contracting Engineer (email@example.com). The Utah and Arizona DOTs also have extensive experience in CM/GC and are willing to provide advice.
—Cox (firstname.lastname@example.org) is assistant branch manager of the Oregon DOT's Major Projects Branch and project manager for the I-5 Willamette River Bridge project.
To see an exclusive slide show of the Willamette River Bridge under construction, click here.