The building team for the eight-acre urban park of the $700-million National September 11 Memorial & Museum—the emotional focal point of the $19-billion World Trade Center redevelopment in Lower Manhattan—is obsessed with something as mundane as surfaces: ground, water, stone and metal.
But the team has a huge burden on its shoulders, one that goes deep down. In the hubbub of activity at the 16-acre WTC site, crews have to deliver 80% of the structured park—a giant green roof topping the site's five-level basement— in pristine condition for the looming Sept. 11 ceremonies marking the 10th anniversary of 9/11.