Steel cages some seven stories high and weighing 25 tons each were then lowered inside the trench panels and concrete poured around it, forcing the lighter slurry up and out. Because the slurry was denser than the dirt that surrounded it, it prevented the dirt from filling the trench. To avoid flooding the site, workers dug a 3,500-foot-long, three-foot-wide trench around the perimeter of the site (comprised of more than 150 22-foot-long sections) and filled it with a slurry made from water and bentonite, an absorbent type of clay. Building the foundation of the twin towers required digging 70 feet to the bedrock and excavating more than 1 million cubic yards of dirt. The chosen site for the project was built on landfill that had gradually extended the west side of Lower Manhattan into the Hudson some 700 feet over the centuries. To build a deep foundation that wouldn't be flooded by the nearby Hudson River, engineers used an innovative ‘slurry trench’ method.Ĭonstructing what was then the tallest building in the world posed one of the most challenging foundation projects ever faced on the island of Manhattan. READ MORE: How the Design of the World Trade Center Claimed Lives on 9/11 3. In 1968, Wien even took out a nearly full-page newspaper ad with an artist’s rendition of a commercial airplane about to fly straight into the upper stories of the North Tower. Led by Lawrence Wien, an owner of the Empire State Building, the Committee for a Reasonable World Trade Center joined a growing number of critics arguing that the twin towers would be unstable at such a massive height-and unsafe in the case of an airplane collision or fire. Perhaps motivated by self-interest as well as concern, a group of leading New York City real estate developers (unsuccessfully) challenged the Port Authority to scale down its proposal for the World Trade Center beginning in 1964. The Empire State Building’s owner helped mount opposition to the World Trade Center project. Tasked with building the world’s tallest building, Yamasaki settled on a design of two towers and five other buildings that would together comprise some 15 million square feet of office space. The Port Authority chose Yamasaki based on his proposal to design a vast trade center that still had the intimate, human-focused qualities of his other designs. By 1962, when Yamasaki applied to design the World Trade Center, he had completed work on a single high-rise building: Detroit’s Michigan Consolidated Gas tower, which had just 30 stories. He started his career in New York, working for the firm that built the Empire State Building, and rose to helm his own firm in Detroit. A little-known Japanese-American architect was chosen to design the World Trade Center.īorn into a poor family of Japanese immigrants in Seattle, Washington, Minoru Yamasaki put himself through college working in fish canneries in Alaska. READ MORE: 9/11 Lost and Found: The Items Left Behind 1. Building the new towers would marshal unprecedented levels of design innovation, engineering prowess -and breathtaking risk. The twin 110-story towers at the heart of the World Trade Center were designed to surpass New York’s iconic Empire State Building-then the world’s tallest building. The vision for the seven-building complex-which would cost an estimated $470 million (more than $4 billion in today’s dollars) and include the two tallest buildings in the world-embodied that same brand of American optimism and ambition. In early 1962, when the Port Authority of New York and New Jersey officially authorized a plan to build the World Trade Center in Lower Manhattan, it came just months after President John F.

New world trade center