Remembering 9/11 – The all important slurry wall

Posted By on September 11, 2014

how-the-world-trade-center-slurry-wall-works-3While thinking about those who lost their lives on September 11, 2001 in 2014, I thought about symbols of strength and endurance that are highlighted in displays at the 9/11 Memorial Museum. One such unseen design element was that of underground “slurry walls” built in 1964. Thanks to the engineers and architects who designed the base for the World Trade Towers, many lives and definitely more devastation was prevented. While reading, one realizes just how close New York City came to having the Hudson River flood, not only the Twin Towers site, but possibly much of lower Manhattan including the subway lines. Because so much of NYC is underground, sophisticated plans were created prior to building the World Trade complex. In the design, a “slurry wall” was trenched and cabled to bedrock up to 80 feet under the ground. In some areas the “special powdered clay containing bentonite trucked from Wyoming”  had to be worked around the 100 year old subway tunnels. This “slurry” was saturated with water and applied to the walls of the excavated trench and reinforced with concrete to create a waterproof barrier … purposed to hold back the Hudson River. This 3 foot thick underground wall encircled the basement of the towers and “stretched for 3,500 feet.” (LINK)

As the 9/11 Memorial Museum FAQ states:

Had it breached, lower Manhattan and the subway lines that run through it might have been flooded, and the destruction could have been even more unimaginable. In the original master plan for the new World Trade Center, architect Daniel Libeskind felt that the slurry wall, in its ability to withstand the forces of destruction, itself had become a symbol of the strength and endurance of our country and its foundational values.


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