Sunday, January 01, 2017

Denver Ave. / Columbia Blvd. bridge

Several years ago, this humble blog featured a lot of posts about bridges. It was a good subject for an ongoing project: They photgraph well, they often have interesting history to dig up, and esoteric engineering details to nerd out over, and there's a limited supply of them, enough to sustain an interesting project, but few enough that you'll eventually run out and you can call it done. That is, unless you're willing to go further and further afield, or write about increasingly small and esoteric bridges that nobody in their right mind would possibly be interested in. Or you can do what I did, which is call it done, but continue on down the rabbit hole anyway.

You can probably guess where this is going: I outdid myself and found a really super esoteric bridge and wrote an entire blog post about it, and I feel like I need to apologize in advance for just how esoteric it is. This one may actually look vaguely familiar, in the unlikely event you've been following the ongoing bridge project all this time. We covered the Denver Avenue bridge over the Columbia Slough back in 2014, along with the Vanport Bridge next door that's used by the MAX Yellow Line. This time we're looking at the Denver Ave. bridge/viaduct over Columbia Boulevard & a Union Pacific rail line, a bit south of the slough bridge. I suppose I just assumed this was all one structure, and the Columbia Blvd. part was just the southern approach to the slough bridge, but there's actually a short bit of road separating them. The state's 2013 Historic Bridge Inventory assures that although the two structures look identical, structurally and legally they are two separate bridges. From the bridge inventory:

In the late 1920s, increased traffic on the West Side Highway led to a major revision in how the highway approached the Interstate Bridge, then the only Portland area crossing into Washington State. Prior to this redesignation, the West Side Highway ended at downtown Portland, with only the Pacific Highway continuing over the bridge. These new bridges were designed to match those on the Pacific Highway, and continued to be a major part of the approach until the construction of I-5. They both feature a unique baluster railing, which is now mostly hidden behind protective wooden paneling.

In a couple of these photos you can sort of see the "unique" baluster, which is somewhat less distinctive than it sounds, unfortunately. Since these photos were taken, ODOT performed a major renovation on this bridge as well as the slough one, and both now sport modern, safe, and non-distinctive railings. As far as I know, ODOT didn't bother saving a chunk of the old one for posterity; it's just gone. In any case, the bridge inventory also includes a few dry stats, in case Obscure Portland Bridges is ever a pub trivia category:

Bridge Number: 04518
Lat/Long: 45 35 09, -122 41 13
Description: Thirteen 71-ft reinforced concrete girder and floorbeam system spans with curved haunches

In case you were curious, "curved haunches" is a technical term in bridge engineering, and was not intended as an insult. The state's 2012 Bridge Condition Report notes that that the slough bridge proper (bridge number 04517, if you were wondering) dates to 1916, with steel construction, while the Columbia/Union Pacific part dates to 1929, with concrete construction. So I suppose there would have been a surface level intersection & railroad crossing here before the current bridge. I'm not sure why this would be useful information, unless possibly you need to date an old photo or it's part of a trivia question, but hey.

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