Rebuilding the World Trade Center site 

Source: ReutersThe World Trade Center twin towers

As the eighth anniversary of the September 11 attacks approaches, the rebuilding of the World Trade Center site has lagged. So far only the steel frame of one of the four planned office towers has risen just above ground level.

Some questions and answers about the 6.5-hectare property in lower Manhattan:

What are they trying to build?

On the site where the Twin Towers and other World Trade Center buildings stood, plans call for four skyscrapers including One World Trade Center, formerly called the Freedom Tower, which will be the size of one of the former Twin Towers but with a much taller antenna.

There will also be a memorial and museum with reflecting pools built on the footprints of the Twin Towers and waterfalls cascading into a subterranean visitor space.

When will it all be built?

The landowning agency, the Port Authority of New York and New Jersey, says One World Trade Center, the memorial and the museum will be finished in 2013.

A mass transit hub, whose elaborate design by Spanish architect Santiago Calatrava has been repeatedly simplified, should be done by 2014.

Less certain is the future of the three other skyscrapers being built by Larry Silverstein, the developer who signed a 99-year lease on the World Trade Center complex two months before it was destroyed. Silverstein and the Port Authority are waiting for arbitrators to settle their latest clash over financing and delays.

What's the dispute all about?

Silverstein says the Port Authority should guarantee his bank loans because its repeated delays caused him to miss the top of the real estate market. The Port Authority wants to limit its commitment because its transportation projects must come ahead of speculative offices buildings that banks are not willing to finance.

What's taking so long?

Former mayor Rudolph Giuliani, the Republican who left office 3-1/2 months after the attacks, said the site should remain a memorial to the nearly 3,000 victims. But the Port Authority and Silverstein were eager to replace all of the World Trade Center offices and shops and the mass transit links.

While those concerns played out, Silverstein and his insurers warred for years in court over how much he was owed.

Then feuds over the design - and security - intensified.

After Berlin-based architect Daniel Libeskind won a public competition, his novel design for a twisting Freedom Tower was modified by Silverstein's architect, David Childs, amid concerns about whether it could be built.

The New York City police department then raised concerns about security.

Another obstacle has been the complexity of fitting so many interdependent buildings into a small space and rebuilding without halting service on the underlying subway line.

New York City Mayor Michael Bloomberg has also pinned some of the delays on the changing cast of politicians. New York state went through three governors in little more than a year.

What are the consequences of the delays?

The rebuilding of the World Trade Center was supposed to symbolise the nation's resilience in the wake of the attacks of September 11, 2001. "The void in the skyline over my shoulder has become a hole in our hearts," Bloomberg said.

Bloomberg, who is seeking a third term as mayor in the November election, says delays could jeopardise New York City's standing as a world financial capital.

Is there demand for all that commercial space?

A study the Port Authority commissioned estimated it could take up to three decades to lease all of the planned offices because demand has withered due to the recession.

Just as lower Manhattan was recovering from the devastation of the attacks, the recession hit.

The vacancy rate for downtown Manhattan rose to 8.7% in the second quarter from 8.1% in the first quarter, according to commercial real estate firm Cushman & Wakefield. Analysts say the rate could keep rising until banks and brokerages resume hiring.

Silverstein says the Port Authority has taken much too gloomy a view of when the downtown office market will revive.