Communities devastated by some of the worst floods in living memory were tonight bracing themselves for a further deluge.
Towns across Connacht and Munster were facing multi-million euro clean-up bills as forecasters warned of four hour downpours in some areas tomorrow.
More than 110 soldiers in off-road trucks and flat bottomed boats were deployed to the worst hit areas, assisting rescues in Cork city and Ballinasloe.
A further 300 personnel and the Air Corps will remain on standby throughout the weekend.
“The critical point in Cork is the Mercy Hospital and that’s the focus of our attention,” an Army spokesman said.
ESB claimed it was forced to open Inniscarra Dam on Cork’s River Lee after torrential rain raised water levels.
But businesses and residents claimed the energy giant failed to issue adequate warnings.
The 300-bed Mercy Hospital, just yards from a bend in the Lee, and UCC bore the brunt of the deluge after the force of water flattened a quay wall.
Troops, ferrying patients in and out of the Mercy by boat, brought one family from as far as Fermoy to visit a dying relative.
Health chiefs were forced to shift A&E patients on to higher floors.
All of the northside and the central southside of Cork city were left without water and UCC has been forced to close for at least a week.
Co Galway was also severely affected with swathes of farmland left underwater.
In Gort a family of five – including an 87-year-old woman – were airlifted to safety during an early morning rescue operation as flood waters surrounded their home.
In Ballinasloe about 200 people were evacuated as the Suck burst its banks.
Another 150 homes had their electricity supply disconnected for safety and residents were warned to boil all drinking water.
The Army spokesman said soldiers were operating in three feet of water.
“The conditions are difficult but we have the equipment there to deal with it,” he added.
Councillor Michael Mullins said the flooding in the town was horrendous.
“The main problem is the sheer volume of rain that has fallen,” the councillor said.
“I spoke to one man who said about 50 years ago he remembered the square being this badly flooded, but we have never seen anything like this in recent years.”
Rail and bus services had been suspended in the county and the main Dublin to Galway road closed.
The National Roads Authority was later forced to open 26km section of the new M6 motorway to bypass the badly affected Craughwell and Loughrea areas and ease the build up of traffic on the cross-country route.
A second 5km section, bypassing Ballinasloe, is also expected to open.
Elsewhere, local authorities and emergency volunteers, including the Irish Red Cross, evacuated people stranded in homes and businesses which were destroyed by rising waters.
Bantry, Clonakilty, Ennis and Clonmel and hundreds of rural homes were also preparing for a massive clean-up.
An Post said deliveries were hampered while Eircom revealed more than 20,000 customers were without a phone line in parts of Cork, Ennis, and Cavan.
“Our crews have identified a number of vulnerable and threatened sites around the country and are maintaining surveillance and patrols on these areas to manage and respond to any increase in risk,” said an eircom spokesman.