Logistical blunders could add millions to the cost of SOM’s One World Trade Centre, in the latest of a string of problems to hit the Ground Zero complex.

The loading dock beneath the 104-storey 1WTC tower will not be finished in time for tenants to install their equipment. A temporary station is in the way and cannot be dismantled until work on a permanent station is completed.

So the Port Authority of New York and New Jersey is having to build five temporary loading bays above ground, costing millions of dollars.

“Several years ago there was a design miss,” said Patrick Foye, executive director of the Port Authority. “Should it have been caught? The answer is, probably.

“We and the other concerned stakeholders believe this will be a short-term issue and will not impede completion of the site or tenants moving into the buildings.”

The Wall Street Journal reported earlier this week that the cost of 1WTC – formerly known as the Freedom Tower – had soared to $3.8 billion, $700 million more than the last public estimate in 2008. Foye refused to confirm this.

1WTC is already 90 storeys high, 60% let, and on track to be completed by the end of the year.

But other buildings in the Ground Zero complex are facing bigger problems.

Foster and Partners’ 2WTC, which is intended to be the second-tallest building on the site, at 88 storeys, is to be temporarily capped at ground level because of a lack of tenants.

The same problem is also threatening to truncate Rogers Stirk Harbour and Partners’ 80-storey Three World Trade Centre at just seven storeys. A Port Authority financing agreement means developer Silverstein Properties must stop building at podium level if it cannot find tenants for at least 10 floors. The rest of the tower could be built when the market recovers.

Work on Aedas’s National September 11 Memorial and Museum and its entrance pavilion by Snøhetta has also ground to a halt because of a dispute over who should pay for infrastructure costs.

Mayor Michael Bloomberg said it was now impossible for the museum to open as planned on the 11th anniversary of the 2001 terrorist attacks.