Updated 9/13/2014:
I have spent the past 3 days working out the dimensions of the model bridge piers. Because of space limitations, the dimensions are not and can not be 1:48 scale with the prototype. They will actually be somewhere in the 75% of O scale, but will retain accurate proportions to themselves and to the bridge model. Below are three photos centered on the piers followed by a dimensional drawing of the model.
First, a distance shot from the Ohio side of the river. Interestingly enough, there are no debris deflectors on the bridge. Upstream is to the left; downstream to the right.
Here you can see the "rings" on the pier. Each is 3' high and made of poured concrete. There is also a good view of the left bridge foot (really massive).
Finally through the dappled sunlight, we can see the railings, the bridge feet, handrails, and the red navigational warning beacon at the top of each pier. The Ohio River sees a substantial amount of towboat / barge traffic.
This is my selectively compressed drawing of the bridge pier.
The thinking is to make a longitudinal slice (split halfway down its height) of pier out of pink foam. The foam will be sealed with joint compound and sanded. Lines for the rings will be scribed into it. The "positive" will be used to make a mold. Halves will be cast using the mold with channels for the beacon light wires cut in the halves. The halves will be glued together, sealed, sanded, and then painted. At least that's Plan A for now.
We'll see how it goes.
George