TEMPORARY REPAIRS to breaches in New Orleans' floodwalls could stay in place until at least next spring, a senior engineer working on the repairs said this week.
'We are trying to base the levee repair plan on the risk of damage from future storms, which means seeing out the current hurricane season and possibly even waiting until after the spring Mississippi water rise for more permanent work, ' said US Army Corps of Engineers New Orleans district commander and district engineer Colonel Richard P Wagenaar.
The Corps of Engineers has been charged with the task of co-ordinating the 'unwatering' of New Orleans - plugging the breaches and pumping water out of the city.
Early work has focused on closing breaches near Lake Pontchartrain to stop water flowing into the city.
These breaches - one at the 17th Street canal and two at the London Avenue canal (see map) - have been closed. Engineers have used a combination of 3,000kg sandbags dropped from Chinook and Blackhawk helicopters and a dumped mixture of large rocks - known as riprap - and crushed asphalt.
Wagenaar said closing the breaches was a matter of urgency and sandbagging was the only viable option.
He added: 'When we first flew over 17th Street and saw the hole, it was surrounded by water on all four sides and we knew we couldn't get there by land or bridge.
'The only option we had was air and time wasn't on our side.
'We had to do something and the solution we picked has worked.' Sheet piling was subsequently used to stop water flowing into the canals from Lake Pontchartrain.
Wagenaar insisted it would have been impossible to use sheet piles to repair the floodwall damage because his teams could not get vital plant to the site.
'We use sheet piling all the time. The problem was that we couldn't get the cranes in.' The riprap and crushed asphalt was also used to build an access road through the foul-smelling water filling gardens backing onto the breach on the London Avenue canal at Robert E Lee bridge.
The access road also helped plug the Robert E Lee breach, and was being built at a speed of 133m per day. Work was carried out-non stop through the searing heat of day and under armed guard at night.
As NCE went to press the road had not yet reached Mirabeau bridge, where the second breach on the London Avenue canal had been closed with sandbags alone.
The practice of dumping rocks on top of sandbags has, however, been criticised by the New Orleans Sewage & Water Board's general superintendent Joe Sullivan, who worked with the Corps of Engineers and contractors to plug the breaches.
He said: 'I'm unhappy with the fact that they've put riprap in the hole, because it means we can't drive sheet piling straight down.
'I know this couldn't be done at the time, and they said it was urgent, but it's going to mean driving the sheet piling down at a later date in a bowed out section - built around the riprap.' JM