Call it Underground Zero. In the middle of the World Trade Center site in Manhattan, workers are performing an intricate balancing act with steel and concrete, excavating beneath an active subway line while a number of other projects progress around them. The top-down permanent underpinning of the subway tunnel will create much-needed space for a new nearby iconic transit station as well as other facilities.
No. 1 subway line runs through a structural box on grade that traverses north-south about 1,000 ft across Ground Zero, just feet from a Port Authority of New York and New Jersey-run trans-Hudson subway line. Crews are excavating below the box in approximately 14-ft increments, working through a forest of rebar and about 500 minipiles, a vestige of a former reconstruction effort.