Short Takes: Winchester Bridge

September/October 2009

History in the Remaking

Oregon’s 1923 Winchester Bridge is rehabbed in just nine months to meet modern safety and capacity standards

By Jim Parsons

The new precast railing and corbels supporting the Winchester Bridge’s wider deck replicate the distinctive Tudor Gothic elements of famed bridge engineer Conde McCullough’s original design. (Photos Courtesy Ken Werner)

Project manager Brad Sullivan has a lot of respect for the 1923 builders of the Winchester Bridge, the 900-ft-long, concrete-arch structure in Douglas County, Ore., created by famed engineer Conde McCullough.

“When you consider the times and the tools they had to work with, what they did is pretty amazing,” Sullivan says. He works for Hamilton Construction Co., Springfield, Ore., a member of the Oregon-Columbia Chapter of AGC, which led the fast-track, $10-million rehabilitation of the historic bridge. The project won a 2009 Aon Build America award from AGC of America.

Completed for the Oregon Dept. of Transportation, the project included widening the deck from 22 ft to 34 ft to meet modern safety and capacity standards, installing a new precast railing to match McCullough’s original design and repairing aging concrete spandrel columns, beams and support brackets.

Because the bridge is a keystone to State Route 99, the principal north-south alternative to Interstate 5, ODOT specified a project turnaround time of just nine months. “A lot of school buses use Route 99, so it was important to minimize the effects on students as well as local businesses by getting everything done in one season,” Sullivan says. The sensitive environment of the North Umpqua River added another constraint. Prohibited from erecting in-stream structures, the team used a suspended scaffold system for the below-deck repairs and pressure washing. The platform also provided a work surface for the overreach system used to replace support brackets and support deck forming.

As another environmental safeguard, a pond-liner drainage canal installed below the deck channeled concrete cutting and drilling slurry to a sanitary sewer system. Looking for opportunities to help ODOT streamline the project, the team recommended using fiber-reinforced polymer to repair unsound concrete elements, a faster, less-costly alternative to installing new rebar and concrete.

To meet the demands of a nine-month highway-closure window, a suspended scaffolding system helped expedite work above and below the deck without affecting the scenic North Umpqua River. (Photo Left & Middle Courtesy of Hamilton Construction Co.; Right Courtesy of Ken Werner)

Other innovations were spontaneous. When core drilling for the new support bracket anchors revealed sections of rebar not shown on the 1920s-era plans, the project team applied ground-penetrating radar to avoid other hidden “surprises.”

Relocating the anchors eliminated the need for 3⁄4-in.-thick polymer concrete resin intended to seal the new precast deck and provide a smoother driving surface. Instead, a 2-in. microsilica concrete overlay was installed in the cold and damp of the southwest Oregon winter. A portable, high-output instant hot-water system and several layers of concrete-curing blankets helped maintain proper deck temperatures for the overlay.

These and other efforts shaved two weeks from the schedule, allowing the Winchester Bridge to reopen on April 27, 2008, 84 years to the day after its original completion.