Green Bay drivers were treated to an unwelcome surprise yesterday, when the discovery of a dramatically sagging pier on the heavily trafficked Leo Frigo bridge (named after a cheese magnate, because Wisconsin) forced its indefinite closure. The incident coincided with a new AP report about the deteriorating state of American bridges, which seems like a perennial source of national hysteria these days. But we shouldn't regress to river-fording just yet.
The recent AP report looked at 607,380 bridges based on the latest study by the National Bridge Inventory, a database that the Federal Highway Administration uses to keep track of every American bridge and tunnel that supports car traffic. The NBI rates each structure on a scale from one to ten, and categorizes them using terms like "structurally deficient,” meaning there’s some defective element, or "functionally obsolete,” which means there’s a non-structural shortcoming. The NBI matters to cities and states because it helps determine whether or not they’ll receive federal funds to help repair their bridges—but as of late, it’s become a bellwether for critics who argue we’re not doing enough to repair our aging infrastructure.
Leo Frigo by Todd Sanders on Flickr.
According to this year’s report, 65,605 American bridges are structurally deficient and more than 20,000 are “fracture critical.” It sparked dozens of other articles, mostly detailing the specific bridges in each state and city that made the critical list. While there’s certainly no one arguing that we shouldn't spend to repair aging infrastructure, there were also some dissenting voices in the crowd—mainly, engineers who argued that the report misinterpreted the NBI classification system.
For instance, the “fracture critical” designation refers to bridges where, if one particular support fails, the entire structure could be at risk. As many pointed out, even brand-new bridges can be deemed “fracture critical” for design reasons. Bridge engineer Andrew Hermann had the following to say to Raw Story:
There’s a little distortion in those facts. Yes, we have over 65,000 bridges that are structurally deficient and over 20,000 that are fracture critical, but fracture critical is really an engineering term. A bridge could be declared structurally deficient because of its deck, because of the piers that hold it up, because of the waterway. It could also be due to an analysis of the structure and the superstructure, but there’s five categories, of which two would only apply to the fracture critical. The misleading thing is that a bridge could be structurally deficient for a number of reasons way beyond the fracture critical.
In Wisconsin, where this week’s closure took place, the NBI singled out 60 bridges as “structurally deficient.” But according to local news reports, Leo Frigo, wasn’t on that list; it was deemed adequate at the last inspection, though there were small cracks noted. For now, the DOT will inspect it again to find out whether something was missed—or whether this is a new development.
Either way, today's story proves that keeping track of every bridge in the US is a hugely complex (and long-term) logistical nightmare—and neither the media nor the NBI can predict every failure.
Lead image: Screen shot by ABC 2 WBAY.