The Port Authority’s foundation work finished in 2009 and, although arbitration was still months from resolution, Tishman’s construction contract for the tower started in January 2010.

As of last year, the Port Authority had already preleased about 60% of the building’s space, provided a master lease for the tower, and begun supporting the issuance of Silverstein’s Liberty Bonds to finance a portion of the project.

With the complicated relationship between Silverstein and the Port Authority, managing these three buildings has been a tricky business, particularly for construction manager Tishman, which has long-standing relationships with both parties.

Mennella acknowledges that this situation has been a “challenge,” but contends that the company keeps a wall between the two camps.

“We have very strict conflict limits,” he explains. “There are only two individuals, myself and one other person, who are allowed to traverse across projects between Silverstein and the Port.”

The need to maintain that separation became most apparent during times of intense negotiations. “We did have, at times, Tishman people on the Port side of the arbitration and Tishman people on the Silverstein part of the arbitration,” he says. “But we have been able to manage that and keep that firewall separate. We’ve been able to keep our head very much in the game. It’s a challenge, but the project is the motivation.”

Regardless of past conflicts, crews take pride in seeing the towers go vertical, Mennella says. His first job at Tishman was on tower five of the original World Trade Center in the early 1970s, and the redevelopment of the site is no ordinary business transaction for him.

“If you’ve been a New Yorker all your life and in construction all your life, [the World Trade Center] is a pretty critical place to be,” he says. “You want to see this thing happen successfully.”