Launch Slideshow

Image

New procurement method deployed for bridge replacement

New procurement method deployed for bridge replacement

  • Image

    http://www.pwmag.com/Images/tmp20B%2Etmp_tcm111-1356761.jpg?width=300

    true

    Image

    300

    The new Willamette River Bridge is 50% complete. The southbound structure (foreground) stands in striking comparison with the original bridge (background). Photos: Oregon DOT

  • Image

    http://www.pwmag.com/Images/tmp20C%2Etmp_tcm111-1356762.jpg?width=300

    true

    Image

    300

    The new structure is a pair of arched bridges that touches down in the Willamette River once. The concrete arches get their shape and strength from cages made from “#18 vert;” at 13 pounds/foot, the largest rebar available. With such a heavy frame, the arch ribs will tip the scales at more than 11 million pounds (photo below explains how they'll be supported). Here, two crew members put the finishing touches on an arch reinforcement cage.

  • Image

    http://www.pwmag.com/Images/tmp20D%2Etmp_tcm111-1356763.jpg?width=300

    true

    Image

    300

    With the formwork removed, the beauty and grace of the new Willamette River Bridge is revealed. The weight of the concrete arches is fully supported by large caissons poured deep in the ground on either bank and in the middle of the river.

  • Image

    http://www.pwmag.com/Images/tmp20E%2Etmp_tcm111-1356764.jpg?width=150

    true

    Image

    150

    Beams of light fall on the southbound bridge, highlighting its elegant arches. Here, crews finalize the new bridge columns and prepare to install the bridge deck.

  • Image

    http://www.pwmag.com/Images/tmp20F%2Etmp_tcm111-1356765.jpg?width=150

    true

    Image

    150

    Residents of Eugene and Springfield, Ore., track the project's progress from a pedestrian viaduct that crosses the river.

  • Image

    http://www.pwmag.com/Images/tmp210%2Etmp_tcm111-1356766.jpg?width=475

    true

    Image

    475

    Before and after: When Oregon's 50-year-old Willamette River Bridge (inset) was deemed structurally deficient, the state used construction manager/general contractor (CM/CG) for the first time to replace the original I-bulb structure with a more attractive deck-arch design pictured in the rendering at top of page. Rendering: OBEC Consulting Engineers

  • Image

    http://www.pwmag.com/Images/tmp211%2Etmp_tcm111-1356767.jpg?width=150

    true

    Image

    150

    Completion of the new southbound bridge (shown here from the west) marks the halfway point of the Willamette River Bridge replacement, which is scheduled to be finished in 2013.

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.