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A New Bridge on Old Olympic Highway

The new McDonald Bridge is safer, wider, and more earthquake resistant.

On 1 May 2018, the McDonald Creek Bridge on Old Olympic Highway between Sequim and Port Angeles, Washington, opened to much community celebration, homemade pies, and the approval of old pioneer families still living in the area. Despite delays in construction caused by snow and bad weather, the project nevertheless stayed within budget and offers a bridge that is safer, wider, and more earthquake resistant than the old bridge that was built in 1957.

The Old Olympic Highway is almost parallel to Highway 101 and sits on the northernmost edge of the Olympic Peninsula, connecting the growing town of Sequim to the city of Port Angeles on the northern coast of Washington State. When Clallam County identified the need to seismically retrofit the bridge to current Washington State earthquake codes, BergerABAM was selected to conduct field investigations, environmental support, and preliminary engineering to identify the existing bridge deficiencies and the conceptual-level bridge repair and/or retrofit approaches.

Though it was technically feasible to design and build a seismic retrofit, the bridge—a three-span concrete voided flat-slab bridge supported by spindly columns—had other issues that needed to be addressed. Its narrow width (23 feet wide and 120 feet long) made it functionally obsolete. In addition, it was vulnerable to potentially destabilizing scour from the creek below near the intermediate columns, and the bridge itself was located in a dip in the road, making it difficult for drivers to see other vehicles as they approached the bridge. As this highway is also popular with bicyclists, the narrowness, approach, and difficult sight lines posed dangers for car drivers and bicyclists alike.

Based on this assessment, BergerABAM recommended to the County that the bridge be replaced rather than seismically retrofitted, and the County agreed. BergerABAM’s team designed a 40-foot-wide, 140-foot-long, precast/prestressed concrete girder bridge with a cast-in-place concrete deck, which eliminated the need for any piers near the creek and helped avoid some environmental impacts. The design improved the sight lines along the old highway and also included civil drainage design. BergerABAM was also responsible for construction administration, inspection services, and design construction support services. Though the initial estimate for project completion was eight months, bad weather conditions delayed the construction two more months. Nevertheless, the project stayed within budget.

As a necessary alternative route to much of Highway 101 along the north coast of Washington State, the local community welcomed the completion of a wider, stronger, and safer McDonald Creek Bridge over the Old Olympic Highway in their 1 May celebration of the bridge’s opening.

For a look at the deconstruction of the old bridge and the construction of the new one, Clallam County has posted a video of the process at the following link. https://vimeo.com/270272547