Minneapolis Bridge Collapse: Day Two

President Bush will address the tragedy in a few minutes. Update: He noted that they spoke about the collapse in a Cabinet meeting, that Secretary Peters is in Minneapolis, and that he thanks fellow Americans for "lifting up" in prayer those involved. I'm surprised the remarks were so brief.

Right now, there are four dead and more than 60 injured. There are 20 still missing.

There's video from a security cam of the collapse, as it happened.

Minneapolis denizen, Lileks:

I’ve driven across this bridge every few days for thirty years. There are bridges, and there are bridges; this one had the most magnificent view of downtown available, and it’s a miracle I never rear-ended anyone while gawking at the skyline, the old Stone Bridge, the Mississippi. You always felt proud to be here when you crossed that bridge, pleased to live in such a beautiful place. Didn’t matter if it was summer twilight or hard cold winter noon - Minneapolis always seemed to be standing at attention, posing for a formal portrait . We’ll have that view again – but it’ll take a generation before it’s no longer tinged with regret and remembrance. We’ll pass on the usual Good Morning message today. It’s not a good morning.

Keep everyone there in your prayers.

The White House said today that the bridge had "structural deficiencies," according to a 2005 report.

White House press secretary Tony Snow said the Interstate 35W span rated 50 on a scale of 120 for structural stability.

"This doesn't mean there was a risk of failure, but if an inspection report identifies deficiencies, the state is responsible for taking corrective actions," he said. The bridge was 40 years old.

Here are the stats on this formerly majestic bridge.

Claim to fame: was built with a single 458 foot long steel arch to avoid putting any piers in the water to impede river navigation.

A University of Minnesota Civil Engineer in a report to MN-DOT recently noted that this bridge is considered to be a non-redundant structure. That is, if any one member fails, the entire bridge can collapse. A key factor is that there are only four pylons holding up the arch. Any damage to any one pylon would be catastrophic. The textbook example of a non-redundant bridge is the Silver Bridge over the Ohio River. It failed shortly before Christmas in 1967 resulting in 46 deaths. A single piece of hardware failed due to a tiny manufacturing defect. But that piece was non-redundant, and the entire bridge collapsed into the icy river. Today, bridge engineers design bridges so that any single piece of the bridge can fail without causing the entire bridge to collapse. It is tragic that the I-35W bridge was built a few years too early to benefit from that lesson.

The drop was the equivalent of about five stories. Construction workers on the bridge, one of whom is unaccounted for, report "riding the bridge" down to the water. Absolutely frightening.