I’ve spent a lot of posts explaining a bit about what engineers do, but let’s dive deep this time. I’m going to tell you a little about how I spend my days on a project by project basis. Today I’m going to start with a project that ties into the recent Metrocenter theme I’ve had going on.
After the Corps of Engineers finished raising and rebuilding the Metrocenter levee, they were confident it would stand up just fine to a 100 year storm. However, someone quickly came to the conclusion that stopping at 100 year protection wasn’t enough given the potential for up to $4 billion. If Katrina taught us anything, it’s that when a levee fails, it fails hard. The levee itself is high enough to hold back a 500 year flood on the Cumberland (with the help of the reservoir system), but there are a few holes in the protection at some strategic points.
The primary hole in the flood coverage is actually a bridge on Interstate 65. If you look at the old maps from my previous posts you can see a drainage stream of some kind and a rail line running under the bridge footprint. Those may have been in place when the bridge was built in 1969, but these days there’s nothing running under the bridge except a buried gas line. As best I can tell there may have been two railroad tracks servicing the Marquette Cement Yard, but they were removed when Metro bought the property in the mid 1990’s. Frankly, I’m not sure the tracks were there even then, because the ground under the bridge is at least 25 ft higher than the parking lot just to the north (where a rail line would go).
This is where I come into the picture. The Corps and Metro asked the state department of transportation if they could build a small ridge under the bridge to keep water out. It seems the river was backing up the low ground just south of the I-65 embankment and if the river got high enough it could pour through the bridge and into the low ground inside Metrocenter. During the process of getting this project approved, the May 2010 flood happened and the Corps had to call out volunteers to lay sandbags under the bridge. They tell me that water got up to the bottom layer of sandbags.
My job as a hydraulic/bridge engineer was to look over their plans and make sure that the bridge wouldn’t be compromised and the project wouldn’t create a new flooding issue. It was a fairly simple assessment. The area under the bridge was already a high point, it just needed to be raised a little further, and the construction plan just consisted of bringing in soil and compacting it in the right spot. With the rail line gone the bridge could be completely torn out and filled in if not for the traffic disruption it would cause on I-65. So state approval was simple enough.
The major problem arose because the Interstate system is actually owned by the federal government. States only manage them on behalf of the federal government, so this project required approval from the Federal Highway Administration. They just happen to have a policy against using road embankments as a levee despite the fact that this one already is being used that way. It took a lot of negotiation (the bureaucratic equivalent of slamming your hand in the car door) but the project was finally approved and construction is essentially complete. Between this project and Metro’s efforts to replace the pump system Metrocenter is even more protected than it was during 2010.
So there you have it. One project in my life. It started out quite interesting and ended up with fingers stuck in car doors, but it’s actually one of the simpler projects I’ve been involved with. Mostly because someone else was doing all the design work.