Sunday, September 28, 2014

N. Portland Road Bridge

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Our next Columbia Slough bridge is the one carrying N. Portland Road; in the photos above, it's the bridge hidden behind the BNSF railroad bridge. I could have gotten closer to take better photos, but neither it nor the railroad bridge looked very interesting so I didn't make the detour. In retrospect I probably ought to have made the trip, since it does have a degree of historical significance. N. Portland Road is actually a state highway, OR 120, although people don't realize this because the state's never gotten around to putting up highway signs. It was built back in the 1930s to connect North Portland to the long-gone stockyards and meatpacking district. One alternate name for the road that's occasionally been used is "Swift Highway", named not for the speed limit, but for the old Swift Meat Packing Company, which built the stockyards and ran Kenton as a company town in the early 20th Century.

As a state highway, the state was responsible for building bridges on it, and for much of the 1930s tha was Conde McCullough's job. He's best known as the designer of fancy bridges along US 101 on the Oregon Coast, but as the state's chief bridge engineer even the most mundane bridges were part of his bailiwick. Obviously he wasn't the state's only bridge engineer, but he tends to get credit for anything the state built during his tenure, similar to Steve Jobs getting sole credit for various Apple products. In this case, McCullough at least invented the type of bridge used here; the department ended up building 158 bridges of this type around the state, so presumably the implementation work for each was farmed out to the department's junior engineers. The wood/concrete composite design was intended to be an affordable way to build smaller bridges, with the important side benefit of throwing some business to the state's struggling timber industry during the Depression. A historical review of the similar (and since-replaced) Vancouver Ave. bridge has a blurb about this one:

The N Portland Road bridge (formerly “Swift secondary highway”), was constructed prior to the subject bridge in 1934 using a similar composite type (Myers 1935:4). The concrete pile bent design varied slightly from the subject bridge by incorporating pointed Gothic-style arch openings. The Swift Highway connected North Portland to the Portland Union stockyards. The bridge retains less integrity than the subject bridge. Many of the understructure wood piles have steel column replacements and the handrail’s wood intermediate posts were removed and replaced by an adjacent modern rail.

Some of the replacement work happened in 2007. The bridge is a major trucking route, so it makes sense that 1930s wood beams would wear out after bearing decades of modern semi trucks. The state transferred much of the highway to city jurisdiction in 2005; from the included map in the transfer deal, it appears the deal transferred everything except the bridge (which it refers to as "Columbia Slough Bridge No. 01726"), with the agreement specifying "Said bridge shall be transferred at such time that said bridge is replaced with a bridge meeting AASHTO bridge design standards", AASHTO being the American Association of State Highway and Transportation Officials. In other words, everyone agrees the bridge needs replacing, and the city prefers that to be the state's problem, paid for from the state's budget.

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