Saturday, November 01, 2014

I-5 Columbia Slough Bridge

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The next Columbia Slough bridge on our mini-tour is the I-5 Columbia Slough Bridge. When highway traffic reports use the dreaded phrase "northbound traffic backed up past the slough bridge", this is the bridge they're talking about. I haven't actually paid attention to traffic reports in a while, since I live in downtown Portland and walk to work. It's possible this phrase is less common than it once was; the bridge was widened in 2008-2010 as part of ODOT's I-5 Delta Park project. The project removed a notorious traffic bottleneck for Clark County commuters by widening this stretch of freeway from two lanes to three in each direction. Somehow they managed to do this without shaving off parts of the adjacent Columbian Cemetery just south of the bridge. The project's final "Revised Environmental Assessment and Finding of No Significant Impact" included a few provisions for coexisting with the cemetery, such as not running pile drivers during funerals.

Even the widened freeway is still puny by the standards of nearly any other city. The Oregon side of the metro area has a general policy of freeways having no more than three traffic lanes per direction, so this is as big as I-5 is likely to get barring an unlikely tectonic shift in local attitudes toward cars. As predicted, the traffic bottleneck simply shifted south to another section of two lane freeway around the Rose Quarter / convention center area. There have been suggestions about widening the freeway there too, and potentially capping it and putting parks or buildings on top. That would probably just push the bottleneck somewhere else again. But I do generally like the idea of capping freeways and hiding the ugliness away underground, so maybe there would be an upside to the idea. My understanding is that the widening was also supposed to be a prerequisite to the now-abandoned Columbia River Crossing, which would have been a ginormous replacement for the current Interstate Bridge.

Anyway, these photos were taken from the new stretch of Columbia Slough Trail that opened in early 2014, so you can see what the bridge looks like from the side and underneath, in case you were curious. It's sort of a utilitarian, unmemorable bridge, but it's interesting that they blended the expansion with the existing bridge so it isn't immediately obvious that it was widened. If you look closely at the bridge supports you can see a line between older & newer concrete where the outside lanes were added.

The library's Oregonian database indicates that ODOT proposed the bridge in May 1962, as part of what was then called the "Minnesota Freeway" project. (I-5 south of downtown was called the "Baldock Freeway" and I-405 was sometimes the "West Hills Freeway" and other times the "Foothills Freeway". All of these names have long since fallen out of use.) A photo spread in March 1964 shows the bridge under construction, and another photo in July of that year shows the bridge nearing completion. By 1981 (when the bridge was only 17 years old), Multnomah County and ODOT were already wringing their hands about it, but at the time they couldn't afford to do anything about it. It was already over capacity in 1981, but they went around in circles for another 25 years before figuring out how to make it happen. I suppose impatient people don't last long in the civil engineering business.

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