Original WTC Construction
Ground was broken on August 5th, 1966. The project began with excavation six stories down to bedrock where the towers’ footings would stand. Crews dug around the PATH train tubes within the site, removing one million cubic yards of earth that would eventually form Battery Park City.
Site preparations were vast and included an elaborate method of foundation work for which a “bathtub” had to be built 65 feet below grade. The bathtub was made of a bentonite (absorbent clay) slurry wall meant to keep out groundwater and the Hudson River. Tie-backs were inserted through the wall and anchored at an angle in the earth behind them.
The foundation construction was just a fraction of many innovations masterminded by Yamasaki and team. Among them were the Twin Towers’ high-speed elevators, sky lobbies, and a “hollow tube” building model that distributed weight from the inner core across floor trusses to the exterior’s closely spaced steel columns. The load-bearing exterior also served as bracing against wind. Floor trusses and exterior-wall panels were prefabricated before being lifted and bolted into place, speeding construction.
The first tenants moved into 1 WTC, the north tower, in 1970, and two years later into 2 WTC. The Port Authority’s construction costs totaled more than $900 million.
To supply power to the 10048 zip code—which was dedicated solely to the WTC site—Con Edison built an electrical substation across Vesey Street in 1967. Atop the substation developer Silverstein Properties built a 47-story, red masonry tower, known as Seven World Trade Center, in 1987.