The twin towers were a financial boondoggle. To make matters worse, there were design problems. Any good sailor knows of galvanic corrosion between aluminum and steel, especially in a marine environment. As winds blew across the Hudson, the aluminum exterior sheathing began to separate from the interior steel beams. The face of the WTC began to fall off. Tenants would not tolerate the tremendous noise of repair. The sensible financial move for the Port Authority was to demolish the buildings. Due to the asbestos insulation, according to one source, the EPA would not permit the buildings to be imploded conventionally. They would have to be taken down by 2007 beam by beam, floor by floor, at a projected cost of $20 billion.