THE FULL extent of damage to New Orleans' infrastructure will only become known when flood water has been removed from the city, engineers said this week.
'Once this has been done, engineers will find that the ground has moved a lot. It was inundated so there will be extra subsidence and ground swelling, ' said ICE vice president and Jacobs Babtie director Gordon Masterton.
'As the areas are pumped dry the ground will change again and foundation strata will be significantly affected, as will the sewerage and water pipes, ' he said.
The clean-up will be further complicated by fluvial sediments, deposited throughout the city. Water supply mains will also have to be cleaned out and repaired.
Engineers were this week assessing pumps used to power the New Orleans drainage system to see how to restart them after the floods.
The pumps were disabled when their electrical systems became flooded after the hurricane.
'We want to start these pumps slowly to watch the impact on the system, ' said US Army Corps of Engineers engineer Greg Breerwood.
New Orleans has a network of 320km of canals connected to 22 major pumping stations which are used to remove water from the canals when levels get too high. They can pump up to 132.5Mm 3 of water per day into the Mississippi river or Lake Pontchartrain.
Five mobile pumps have also been brought in to the city to help empty it of floodwater. The US Army Corps of Engineers estimates that drainage could take as long as three months.
Only then will engineers begin to understand the extent of the damage.
mage is widespread across the state of Louisiana.
Ken McCool, manager at American Water Works Association (AWWA) Mississippi section, has been working with the US military's Emergency Support Function group, headed by the US Army Corps of Engineers.
'We have 800 waste water works in Mississippi, 120 of which are in the affected area.
More than half of those are down.
There are also 180 water treatment works that are down, mainly in coastal locations, ' he said.