The Atchafalaya Basin Bridge
The Atchafalaya Basin Bridge is a twin bridge that crosses over the basin on I-10, a major highway between Baton Rouge and Lafayette. A twin bridge is one in which two parallel bridges of similar size run side by side. The Atchafalaya Basin Bridge is one of Louisiana's busiest bridges. It's unclear exactly when bridge construction began, but both parts of the structure were built at the same time, and the bridge was open for traffic by 1973. When you drive on it, it seems to go on for a long time. The bridge is elevated in places, and you might notice that you're driving right by treetops. But why, if it's on low ground? Well, several rivers weave under the bridge and in some places it was built high enough to allow barges and tow boats to pass underneath.
The bridge is around eighteen miles long and made of a stringer design, meaning it uses a series of parallel steel beams to support a concrete deck. It's not a particularly attractive bridge, but serves an important purpose for this part of the state. Also known as the 'Swamp Expressway,' it includes two exits off the bridge into sparsely populated, rural bayou areas. The twin bridges merge when crossing Whiskey Bay Pilot Channel, a canal dredged in the 1930s for shipping traffic.
Building the Bridge
The saturated soils and winding riverbeds of the Atchafalaya Basin presented real challenges for the bridge's design and construction. Before work on the bridge began, a canal had to be dug through the swamp to the bridge's future location. This enabled barges with cranes to get to the work site and for the transport of needed materials as construction moved forward. Workers operating the cranes did all their work from the barges.
Boh Brothers Construction Co. from New Orleans did some of the work on the bridge structure, because they were experts in land and marine pile driving, a process that uses a machine to drive heavy poles into the ground to support the foundation of the structure. For the Atchafalaya Basin Bridge, the poles supported concrete columns that had to be put into place before the bridge deck could be installed. Then, pre-cast cement segments were manufactured at a factory on Lake Pontchartrain and floated to the bridge site by barge. Cranes lifted the segments onto the support columns.
Facts About the Bridge
Let's now go over some key facts about the bridge. The Atchafalaya Basin Bridge is a little over 96,000 feet in length and is one of the longest bridges in the U.S. as well as one of three very long bridges in Louisiana. The bridge is owned by the State of Louisiana and maintained by the Louisiana Department of Transportation and Development, and it has more than 30,000 vehicles cross it each day.
Lesson Summary
Let's review…
The Atchafalaya Basin Bridge carries highway I-10 across the Atchafalaya Basin, a vast river swamp environment in south-central Louisiana. The approximately eighteen-mile twin bridge, with two similar bridges running parallel to each other, is among the longest in the United States. The bridge has a stringer design, which uses a series of parallel beams to support a concrete deck. To build it, a canal first had to be dug to get construction equipment and materials to the site. Among the builders was a New Orleans company with experience in pile driving, a process in which poles are sunk into the ground to help support a foundation. When the support columns were in place, pre-cast segments for the deck were brought to the site by barge and installed to actually form the bridge.
