It took 11 years to finish building the World Trade Centre, and at the rate of rubble-clearance it is likely to take almost seven months to remove the 1.2 million tonnes of steel, concrete and other debris which crashed from the 107-storey Twin Towers and connected buildings on September 11th.
The removal of the steel and concrete has become the biggest demolition and salvage job in the world and is proceeding at a breakneck pace. After four weeks, 200,000 tonnes have been removed and trucked or shipped to scrapyards, investigation centres or landfills.
Working around the clock, a dozen cranes, some as high as 50 storeys, pull contorted girders from the tangled mass of debris, while lines of diggers with clam-shell grabbers climb high to lift loads of twisted mesh, smashed tiles, crushed glass and pulverised concrete onto trucks.
As the site is cleared from the edge, temporary tarmacadam roads are laid into the heart of the still-smoking, 70-ft mountains of rubble. In two days this week a half-acre waste lot on West Side Highway was flattened and converted into a runway-smooth parking lot for emergency vehicles.
All around the disaster site, traffic patterns have been redrawn. There are always queues of flatbed and open trucks waiting their turn to take loads away. Rescue and recovery workers labour in shifts, even through heavy rain, assisted at night by specially-erected lights powerful enough to illuminate a giant sports stadium.
They only pause when a body is found, but the majority of the 4,815 people still missing are likely never to be found, having been consumed by fire or atomised by the weight of the falling towers. Only 417 bodies have been located and of these 366 identified.
The Port Authority of New York and New Jersey, which built six of the seven World Trade Centre buildings, has found that organising the removal of the remains of what was, for a time at least, the world's tallest man-made structure, is as complex as the 1966-1977 building programme.
"In the grossest terms, the process is very similar to what we would do if we were going to design the trade centre all over again," the authority's chief engineer, Frank Lombardi, told the New York Times.
Together, the twin towers contained 156,000 tonnes of recyclable steel, worth up to $100 a tonne, giving scrap metal merchants their biggest intake ever and creating a multi-million dollar business as a by-product of the clearance operation. One New jersey dealer, Bob Kelman of Hugo Neu Schnitzer East, said it could end up in new skyscrapers or in refrigerators or car bumpers.
"It's a very slow, very deliberate process," said Allen Morse, the top debris expert with the US Army Corps of Engineers. "It's like nothing the Corps of Engineers has ever been involved in." The Army Corps of Engineers has calculated that the site contains 308,900 tonnes of steel and 351,000 tonnes of concrete. The structural engineering company of Leslie E. Robinson Associates which helped build the Twin Towers estimates that it contained 3,881 tonnes of steel reinforcing, 47,453 tonnes of vertical steel columns, 8,462 tonnes of aluminium and glass and 48,099 tonnes of ceiling materials, flooring and partitions. The steel pieces are cut on site by ironworkers and loaded onto flatbed trucks. Each load is hosed down, recorded by a member of the National Guard to prevent fraud, and driven to special barges at Pier 25 on the Hudson and Pier 6 on the East River. By yesterday almost 12,000 truckloads had been taken from the site, of which some 2,000 was loaded onto one of 64 barges for shipment to Brooklyn and on to New Jersey or Staten Island.
At a landfill in Staten Island, some 1,500 people comb through the rubble under the supervision of the New York Police Department and the FBI, looking for personal belongings such as watches, rings and wallets, and body parts. Many distressing items have been found, such as a hand clutching a rail. The coroner is called in when human remains are found. The clearance work is being carried out by up to 1,000 New York Sanitation Department workers and a consortium of four private construction contractors.
Debris from the World Trade Centre Building 7, a 49-storey tower which collapsed after being struck by falling sections of the north tower, is being handled separately as it contained sensitive government information in several federal offices.
Three buildings around the site are expected to be demolished, adding to the clearance load, and the damaged Winter Garden atrium in the World Financial centre across West Side Highway may also have to be pulled down, so extensive is the damage from the collapse of the south tower.