Wallace Tunnel Upgrade

By Jere Hough Meteorologist / Feature Reporter

The Wallace Tunnel is safer with a new system to deal with excess water. Wallace Tunnel Upgrade

Published: Thu, October 02, 2008 - 2:34 pm Last Updated: Thu, October 02, 2008 - 3:34 pm

Jere Hough

Hurricane Katrina flooded downtown Mobile. The Bankhead Tunnel's flood gates had been closed for the storm. But during and after Katrina, the Wallace Tunnel stayed open.
There are grates at both ends of the tunnel that capture any water as it flows into the tunnel, and beneath the highway, troughs carry the water to a set of pumps that move the water to Mobile Bay.
But in the wake of Katrina a pipe broke.
Nick Amberger, an engineer with the Alabama Department of Transportation tells what happened. "When it broke it allowed water, the waters that had come into Mobile Bay, to backfeed into the Tunnel and started filling parts of it up."
The existing pumps couldn't keep up, and water got very close to, but never actually reached, the roadway.
Amberger continues, "We had the help of the Mobile Fire Department along with three fire trucks and a whole bunch of firehose to get the water up and out of the tunnel."
Meteorologist Jere Hough stands in the area under the roadway. "This is the air duct below the highway. During Katrina it flooded up to the ceiling here. Obviously after the storm plans were made to revise the pumping system."
A flooded air duct creates another problem. Car exhausts contain dangerous carbon monoxide. Huge fans at each end of the half-mile-plus tunnel force a constant supply of fresh air up into the tunnel...removing it before it can accumulate. Clearly nothing should inhibit the free flow of the air.
And storm surge flooding? The Alabama Department of Transportation thinks it ready if there's another Katrina. Amberger says, "We can handle a little over sixteen feet."
The new pumps can work under water if needed, and move enough water to fill 20x40 ft. swimming pool in less that four minutes.
Incidentally at its lowest point, the tunnel drops to about 90 feet below the surface.