Monday, March 15, 2010 Previous editions
Saturday, November 21, 2009
THE ESB has defended its decision to release millions of tonnes of floodwater from the Inniscarra dam.
A spokesman said they had to act to safeguard the massive structure after unprecedented amounts of rainfall put the dam under severe pressure.
He said if they hadn’t acted when they did, the flood which swamped Cork city would have been up to 33% worse.
"This was a once in 800-year flood event. If we weren’t there, you would have had 800 tonnes of water per second coming down the valley," he said.
"The ESB is responsible for maintaining the dam and making sure the dam is safe and that flood waters are discharged safely."
Weeks of sustained and heavy rainfall have seen water levels in the 306 square mile Lee Valley rise to unprecedented levels.
The ESB has been releasing excess water through its dams at both Carrigadrohid and Inniscarra in recent days to maintain the levels.
Because the water was released gradually, there was little or no effect downstream.
But the situation reached crisis point on Thursday after four inches of rain fell over the course of a few hours and the dam came under increasing pressure.
The volume of water flowing through the Lee channel at that point surged from 535 tonnes per second at peak flow to an incredible 800 tonnes per second – an estimated six times the usual flow rate.
As the situation escalated, the ESB alerted all relevant agencies on Thursday morning about their plans to release massive amounts of water.
"Personnel at Inniscarra dam informed Cork County Council, Cork City Council, and the emergency services," a company statement said.
"In addition, ESB issued a media alert, warning of the danger of severe flooding in the Lee Valley between the Inniscarra Dam and Cork city, approximately eight miles away.
"ESB is fully satisfied that it discharged all its obligations in terms of managing the flood situation at the dams and in notifying the relevant statutory bodies."
Floodwater peaked on Thursday night and, while very large flows were still being experienced yesterday, engineers at the dam said the level of water being released was reducing.
"However, the evolving weather situation is being closely monitored," the company said.
There are two hydro-electric dams on the River Lee. The first, at Carrigadrohid, has one generating unit with a capacity of 8MW.
The second, and largest, is at Inniscarra. It has two generating units – one with a capacity of 15MW and the other with a capacity of four megawatts.
The two dams have a combined capacity of 27MW and produce almost 80 million units of electricity a year.
Power is generated at 10.5 kilovolts and transformed up to 38 kilovolts for local distribution and to 110 kilovolts for long-distance transmission.
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