Have you ever heard of the Lake Pontchartrain Causeway? It is a bridge in Louisiana that spans 23.87 miles and connects the cities of Metairie and Mandeville. It is not just any bridge; it is the longest bridge over water in the world and an incredible feat of engineering.
History
The idea for the bridge was first proposed in the early 20th century, but it wasn't until the 1950s that construction began. The bridge was opened in 1956, and at the time, it was only about half the length it is today. It wasn't until the 1960s that the bridge was expanded to its current length.
The modern causeway started to take form in 1948 when Ernest M. Loëb Jr. envisioned the project. Due to his lobbying and vision, the Louisiana Legislature created what is now the Causeway Commission. The Louisiana Bridge Company was formed to construct the bridge, which in turn appointed James E. Walters Sr. to direct the project. Ernest M Loëb was assisted by his nephew, Ernest M. Loëb III, in planning the construction of the bridge.
The idea of a bridge spanning Lake Pontchartrain dates back to the early 19th century and Bernard de Marigny, the founder of Mandeville. He started a ferry service that operated into the mid-1930s. In the 1920s, a proposal called for the creation of artificial islands that a series of bridges would then link. The financing for this plan would come from selling home sites on the islands.
Engineering
The bridge is made up of two parallel spans, each consisting of more than 9,000 concrete pilings. The pilings are sunk deep into the lake bed and support 8,000 prefabricated concrete segments that make up the bridge deck. The spans are separated by a 250-foot-wide navigation channel, which allows ships to pass underneath the bridge.
One of the most impressive aspects of the bridge is its continuous concrete railings, which stretch the entire length of the bridge and provide added safety for drivers. The railings are designed to withstand hurricane-force winds and the impact of a fully-loaded tanker ship.
Dr. Maxwell Upson, the Chairman of Raymond Concrete Pile Company, one of the largest contracting companies for foundations in the United States, was an innovator in the field of prestressed concrete, particularly in pile fabrication and installation. He saw prestressed concrete as a way to break down the barriers that once limited how piles could be installed. Before Dr. Upson's research, most concrete piles were square with dimensions of 24 inches or less. He saw the potential for using piles with dimensions of 36 to 54 inches. Using smaller pile segments and prestressing technology, he revolutionized the way piles were manufactured.
Louisiana soil, which is made up of soft clays and silts, does not develop large tip-bearing capacities and requires that piles be driven deep until sufficient resistance is developed to support the load. Therefore, these large, prestressed hollow piles were ideal for developing the foundation for a bridge since they could withstand the hammer blows needed to drive the piles deeper into this type of soil.
Once they decided that these larger hollow cylindrical prestressed concrete piles could be used for their bridge foundation, the civil engineers needed to develop a design and method of construction. Given that the contract required the construction of the 24-mile span in only 23 months, the engineers devised a rather simple structure - two piles straddled by a bent cap supporting the ends of two 56-foot decks. This simple layout is repeated over and over. By making the components (piles, bent caps, and decks) identical, Upson, Blessey, and the engineers at Palmer and Baker could employ the theories of mass production to build this bridge.
A concrete casting plant was built at the northern end of the bridge; the components were prefabricated and then barged out via the Lake to the construction site. This assembly-line process significantly reduced both the construction cost and the installation time. The record shows that the bridge was constructed in fourteen months from the time the first piles were driven on May 23, 1955. The original (now Southbound) span opened to traffic on August 30, 1956.
Fun Facts
The bridge is so long that for most of its length, drivers can't see land on either side.
The bridge is a popular spot for fishing, and there is even an annual fishing tournament held on the bridge.
The bridge has been featured in several movies, including the 2011 film "Contraband."
Conclusion
The Lake Pontchartrain Causeway is truly a wonder of engineering and a testament to human ingenuity. Whether you're driving across it or just admiring it from afar, it's impossible not to be impressed by this incredible feat of construction.
With its fascinating history and innovative design, the Lake Pontchartrain Causeway is a must-visit destination for engineering enthusiasts and anyone looking for a unique experience. So next time you're in Louisiana, be sure to take a drive across the Lake Pontchartrain Causeway and experience it for yourself!