Ever see the frame of a 40 year-old car from Minnesota?
Or Chicago? Or New York?
Or anywhere they use salt on the roads?
It should be no surprise this bridge rotted out.
The only surprise will be if any other old bridges actually don't cave in too.
http://www.freerepublic.com/focus/f-news/1874950/posts?page=154#154
There are a couple of photos in the link above, #154 and #167, that give a good perspective of the bridge and the current flowing from the dam above the bridge......
It should be no surprise this bridge rotted out.
The only surprise will be if any other old bridges actually don't cave in too.