Oregon's Bridges: Coos Bay Bridge

As we continue our study of bridges along Oregon's coast, we come to the Coos Bay Bridge twenty miles south of the Umpqua River Bridge. It's amazing that the state of Oregon was able to build five long span bridges along it's coast in a single year and build a highway between California and Washington State in about a decade. In one fell swoop, people were able to drive along the coast from San Francisco to Seattle. I wonder how the money, material, and labor became available to get so many handsome bridges built in such a short time?

The Coos Bay Bridge (also called the McCullough Memorial Bridge) is a steel, cantilever truss bridge with a 793 ft main span, 458 ft long side spans, and thirteen reinforced concrete arch approach spans for a total length of 5305 ft. The steel truss segment was designed with curved top and bottom chords to match the arches of the concrete approach spans. It was the largest of the five bridges built as part of the Oregon Coast Bridges Project and cost slightly over $2 million in 1936.

Oregon's Bridges: Coos Bay Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Oregon's Bridges: Umpqua River Bridge

The Umpqua River Bridge has two 154 ft long reinforced concrete bow string arch spans on each side of a central, 430 ft long steel through truss swing span. It's the longest swing bridge in Oregon, one of only five still on the State highway system, and of historical significance for the technology it uses.

This bridge was built in 1936 by Teufel and Carlson of Seattle and designed by Oregon's chief bridge engineer, Conde McCullough. As you may have noticed, the Umpqua River Bridge is just one of several monumental bridges built along Oregon's coast (on US 101) and completed in 1936 as part of the Oregon's Coast Bridge Project. The swing span was built to allow the passage of tall sailing ships that were once common along Oregon's coast and the Umpqua River. This bridge was added to the National Register of Historic Places in 2005. Note the unusual barrier rail with concrete pylons at the ends of the bridge.

Like yesterday's Siuslaw River Bridge, the Umpqua River bridge is located several miles from the mouth of the river because a huge sandbar (the Oregon Dunes National Recreation Area) is along the coast. I may as well mention that the Cascadia Subduction zone also runs parallel to Oregon's Coast. It produced a huge earthquake and tsunami in 1700 and is expected to produce another large earthquake every 300 to 600 years. The worst-case scenario would be that the earthquake would damage bridges, preventing people fleeing the coast from reaching higher ground when the tsunami waves strike the coast. However, the state of Oregon should be credited for developing tsunami evacuation routes all along the coast.

Oregon's Bridges: Umpqua River Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Oregon's Bridges: Siuslaw River Bridge

Continuing south along the Oregon coast is the city of Florence and the Siuslaw River Bridge. This is one of Conde McCullough's most ornate creations. A 140 ft long steel, bascule bridge was built between two 154 ft reinforced concrete bow string arches, which are connected to 20 concrete girder approach spans. Among the decorative features on this bridge are obelisks that support the movable span, pylons at the far ends of the arch spans, an ornamental railing, arch shaped two-column piers, X-bracing connecting the arch ribs, and haunched girders on the approach spans.

The Siuslaw Bridge has a total length of 1568 ft and it was built in 1936 by the Mercer-Fraser Company of Eureka, California. The bridge would be at the mouth of the Siuslaw River except there is a giant sandbar that makes it flow another four miles before it finds the Pacific. The city of Florence is on the north side of the river and has a population of about 8000 people. The economy used to be based on logging and fishing but now its mostly supported by tourism and by retired people moving into the area. Perhaps the movable bridge span was to allow the passage of boats loaded with timber from Oregon's interior.

We can see timber piles sticking out the river where a dock once stood. The river was crossed by a ferry before the bridge was built.

Oregon's Bridges: Siuslaw River Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Arch Bridges: Alsea Bay Bridge

Oregon is fortunate to have many lovely bays along its coast. It is also fortunate to have had Conde B McCullough as the chief bridge engineer when US101 was being constructed during the Great Depression. As a result, there are a dozen beautiful bridges crossing the rivers and bays along Oregon's coast.

However, when the existing Alsea Bay Bridge began to deteriorate due to the saltwater environment, an equally handsome and innovative bridge, designed by Semyon Treygor at HNTB was built in 1991. The main span is a 450 foot long reinforced concrete through-arch with long approaches supported on 'Y' shaped piers. The replacement bridge was built with a thicker concrete cover to resist the salt-water spray. All that is left of Conde McCullough's original bridge are the concrete viewing platforms at each end of the new bridge.

Arch Bridges: Alsea Bay Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution 3.0 United States License.