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Tuesday, October 24

The New Braunfels Ave bridge debacle

About a year ago we started the process of replacing the old New Braunfels Avenue overpass - the old one was damaged and prone to getting hit by semi trucks. These bridge replacements are typically done in halves so we continue to carry traffic on the bridge while it's being built.
A few weeks ago we finished the first new half of the bridge and demolished the remainder of the old bridge. The new bridge had everything - sidewalks and decorative arches included.
It looks ... well, terrible.
No two ways about it, the concrete barrier along the new portion of the overpass we're building over I-35 near the Government Hill neighborhood didn't turn out the way it was planned.
First of all, the structural integrity of the bridge is fine - the issue is purely aesthetic. It's still super embarrassing for everyone involved. With that preface, let's get through the brass tacks here.

What in the heck happened?
The arched windows of the bridge rail are made by pieces of Styrofoam inside the concrete forms. When concrete was poured these Styrofoam chunks shifted. In some cases they shifted a lot. Nobody could see what was happening until the forms were removed, which happened the weekend we demolished the remainder of the old bridge.

Who was supposed to be watching this thing?
We have a consultant group watching our construction activity on this project. SAM-Construction Services has a team overseeing the work done by CRG, our prime contractor. In order to avoid project lag they asked Bexar Metro Area Engineer Eddie Reyes if they could demolish the old bridge the same weekend they had the new portions structurally ready for traffic - something that had initially been planned to happen at least a week prior to the demo work.
Since the problem happened inside a concrete form, nobody could see the issue until the forms were wrecked. The foam cutouts couldn't be observed; there was no way to know things had floated so far out of whack.

Did TxDOT pay for it?
Project Engineer Jon Green says we only paid labor costs and for some materials; we haven't paid for the whole bridge rail. That payment will come when the rail is reconstructed correctly.

How are we fixing this?
By time this defect was discovered the old bridge had already been demolished and we needed to be able to put traffic on the new bridge, where folks are driving today. With the tight constraints of the bridge we simply don't have enough workspace to solve the problem yet.
The good news: once the remaining half of the bridge is constructed we can move traffic away from the defective rail and reconstruct it. That will be done at CRG's cost.
In the meantime the project team is re-thinking the way the forms are made to prevent this frustration from happening on the other bridge rail.

What is the bridge going to look like?
This is answered better with some pictures - you should be able to click to enlarge.
Here's the overall bridge overview:
And the detail of the arches:
No, the arches won't be pointy:
Then there's the detail of the caps breaking up the archways:
And the center column of the bridge: