09-01-2010, 10:15 PM
Fire is a possibility, but I am thinking that the original bridge was built sometime ago, and as locomotives and loaded car weights went up, they refurbished the bridge to handle the heavier traffic. I am imagining that the engineering department determined that the six large-diameter poles per bent, with the bents 14 feet apart, was plenty enough for the increased capacity needs, but the rest of the bridge was no longer strong enough. So, they removed the deck, cut off the poles, and added the pre-cast concrete toppers on them. Then the 4 I-beams on top of that, then a new deck.
Three Foot Rule In Effect At All Times