Construction begins on Silverstein’s WTC 3 and 4 towers

After a five-year delay, construction on World Trade Center towers 3 and 4 has begun. The $20 billion Silverstein Properties project, which also includes tower 2, is slated to be complete by 2012. The towers will create 7.6 million square feet of office space, which could ease Manhattan’s office space shortage. The Port Authority is the only anchor tenant lined up, and there are concerns that the softening economy could complicate leasing out all the space.