New York at risk of flooding
New Yorkers trying to come to terms with both massive loss of life and the devastation of Manhattan may now be facing yet another calamity - flooding.
Engineers are warning that the walls of a giant concrete box, 20 metres deep, which acted as the foundations of the World Trade Center, are in danger of collapse.
This would allow the Hudson River, which runs on one side of the island, to flow into the site, and from there into the entire New York subway system.
The warning came as New York Police Commissioner Bernard Kerik gave the bleakest assessment yet of the chances of pulling anyone alive from the rubble that was once the World Trade Center.
"I think with every day, every hour and every minute that goes by, that hope diminishes. Right now it's not looking too good," said Commissioner Kerik.
Weakened foundations
Emergency workers are faced with an increasingly daunting task.
Engineers believe that only the debris of the towers is holding the foundations up and removing that rubble could make them collapse - under pressure as they are by the water and mud that surrounds them.
If they do, there is a real danger that water from the Hudson River could flood the metro station under the WTC and then flow along its tunnels into the main subway system.
In order to reduce this risk, emergency workers are having to excavate the site very carefully and shore up the walls as they go.
Small amounts of water, presumably from rain, fractured pipes and fire hoses, have already trickled down to what remains of the underground station.
Giant plugs
Contractors are planning to block the water by inserting giant concrete plugs into the ends of the tunnels underneath the remains of the centre.
The emergency teams' task is made all the harder by the dawning reality that they are likely to be finding bodies rather than survivors.
Workers have retrieved just 218 bodies from the wreckage of the twin towers, in which more than 5,000 people are missing. No-one has been pulled out alive since last Wednesday, a day after the attack.
There had been great anticipation that people trapped in the seven basement storeys of the World Trade Center - once shops and car parks - might have survived.
"The heat at the lower levels is very extreme," rendering the chances of finding survivors "very slim", said Commissioner Kerik.
On Wednesday workers retrieved the bodies of two colleagues, two policemen who were caught in the collapsing building as they assisted with evacuation.
The total number of missing currently stands at 5,422, with just 152 out of the 218 bodies identified.
Posters of missing people are plastered around New York, and makeshift memorials have sprung up in front of police and fire stations.
Hopes and fears
Many people seeking their missing loved ones do not know whether to give up hope.
Jennifer Liang, wife of fireman Kevin Bracken who was buried under the north tower when it collapsed, has accepted that her husband will never come back.
But she also realises that colleagues still searching for him need to have hope that he is alive.
"It's difficult for me when they say that perhaps they'll find him," she said.
"They are there all the time, risking their own
lives in holes in the rubble and they need to
believe that there is still hope."
-- Anonymous, September 20, 2001