Saturday, September 27, 2014

MLK Columbia Slough Bridge

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For several years now, one of this humble blog's ongoing projects has involved bridges. I started out with Portland-area Willamette River bridges, and once I'd done posts about those I ended up doing bridges on the Columbia, Clackamas, and Sandy Rivers too. I've also done bridges in the Columbia Gorge (and there may still be a few of those that I've missed), as well as a bunch of bridges in Cleveland from a trip there a few years ago. I also recently found some lists of Portland-area bridges that local governments believe are historically significant, so I've covered a couple of those too. A few months ago it occurred to me that there were a decent number of bridges on the Columbia Slough, in N/NE Portland, and I could visit a lot of them just by walking the Columbia Slough Trail. None of them are really visually stunning, but some at least have a bit of historical significance. Case in point, the bridge shown above, which carries MLK (a.k.a. state highway OR-99E) over the Columbia Slough. Its Bridgehunter page describes it:

The Columbia Slough Bridge on OR 99E was constructed in 1916 as part of the Interstate Bridge project. The bridge features built-up steel plate girder main spans and the same decorative steel railing found on the 1917 Interstate Bridge over the Columbia River. The bridge was likely designed by consulting firm of Waddell and Harrington just like the Interstate Bridge located just a short distance to the north.

The 304-foot original portion of the bridge features four steel plate girder spans with two main spans of 77.3-feet and two side spans of 76.2-feet. In 1951 the original 44-foot wide structure was widened to 58-feet by the Oregon State Highway Department to accommodate another traffic lane. The new portion of the bridge has a different span layout featuring two 140-foot plate girder mains spans and reinforced concrete approach spans at each end of the structure. The total length of the widened portion of the bridge is 362.5-feet.

In other words, this bridge was a minor project by a very famous bridge design firm. They were the same company behind the Interstate Bridge (obviously), as well as the Hawthorne and Steel Bridges in downtown Portland, the Union St. Bridge in Salem, and the Columbia River Highway bridge over the Sandy River in Troutdale. Oh, and the 12th Ave. Viaduct over Sullivan's Gulch / I-84, near Lloyd Center, which counts as another minor project.

A July 1916 Oregonian article on the near-complete Interstate Bridge mentions the slough span briefly as a remaining to-do item, due to problems with the initial construction done there:

When the water falls sufficiently, a pier will be erected in Columbia Slough to replace the one destroyed by the shifting of the bottom of the slough on account of the tremendous pressure of the big fill at that point. Not until this pier is built can the girder spans across Columbia Slough be placed.

Other than a few traffic accidents, the bridge apparently hasn't been newsworthy since its construction. I suppose if they ever get around to replacing the current Interstate Bridge, this little bridge would be left around as the last surviving piece of the original project. At that point the bridge might come be seen as an interesting historic artifact. But given the recent cancellation of the Columbia River Crossing project, that day isn't likely to come anytime soon.

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