Minnesota bridge was blown up

Overview
Summary: the Minnesota bridge was blown up, rather than collapsing accidentally. (This is an original hypothesis which I haven't yet seen anywhere else, as of 2007-08-03; it is very likely wrong. -W.)

Hypothesis: The bridge was destroyed as part of a campaign to discredit science and engineering in the US. The Bush administration has always been anti-science; this was exacerbated by reputable scientists and engineers finally getting involved in the 9/11 Truth movement, which threatened to make such inquiries respectable and worthy of being taken seriously.

Conclusion: Accident waiting to happen, not malice.

Evidence

 * One short section of bridge collapsed separately from the water span. How could this happen naturally? (Possibly horizontal strain from the main span collapsing... but it feels suspicious.)
 * The suddenness of the collapse seems wrong. You would expect one join to start tearing first, or something... (again, a completely non-engineering, non-scientific observation...) The only video of the collapse doesn't show the side which apparently failed... but the bridge collapses straight down (echo of the descriptions of WTC collapses -- or just tired old conspiracy hack-phrase?) (On closer inspection of the video loop, it sometimes seems that what initially failed was the center of the span (the top of the shallow arch), which might explain the north-south symmetricity of the collapse but not necessarily the east-west. However, it also sometimes looks like both ends of the main span descend abruptly by maybe 5-10 feet, simultaneously, and that this is what initiates the main collapse.)

Main flaws

 * The one known video of the collapse shows clearly that there was no noticeable dust prior to the roadbed hitting the river; if structural members had been severed by explosions, there probably would have been. (Perhaps explosion dust was trapped on the underside and only emerged after the air was forced out by impact with the water? The video was slightly above the level of the roadbed, and might not have been able to see anything happening underneath)
 * The Department of Homeland Security stated that they believed the collapse was an accident; if they had wanted to "use" this explosion for some larger agenda, surely that would have included claims of terrorism? (Paranoid second-guessing: maybe they're waiting until later to come back and bring up "new evidence" showing terrorism... conveniently timed to coincide with an election or something...)
 * Bridge collapses not caused by any external force (earthquake, flood) or impact do happen every few decades; this is the first such collapse since 1983, which followed one in 1967. A 1991 evaluation of the bridge cited several serious structural problems. "The report also noted a concern about lack of redundancy in the main truss system, which meant the bridge had a greater risk of collapse in the event of any single structural failure." A 2005 report stated that the bridge was in possible need of replacement. So... this is not an unprecedented event.