FLOODWATER is estimated to breach the unfinished wall of the new Cotter Dam by 7pm tonight, says ACTEW managing director Mark Sullivan.

Earlier this afternoon Mr Sullivan tweeted a series of photographs showing floodwater dangerously nearing the top of the unfinished 40-metre high wall at the new dam construction site.

The old Cotter Dam wall, at 30 metres in height, has been completely subsumed by flooding water.

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All workers have been evacuated from the site, with only five workers remaining to observe the outflow.

Mr Sullivan said ACTEW have done “a lot of calculations” but there is no immediate threat to the structure of the dam.

“The structure itself is entirely safe, the big cranes are safe, there’s nothing in terms of a threat,” he said.

Mr Sullivan said ACTEW has a safety plan for such an event, which involves creating a channel for water flow over the centre piece of the dam.

“The only danger is what happens downstream,” he said. “Ramps that could easily be washed away.”

This is the third time the new Cotter Dam has overflowed; it happened twice in 2010, when the dam wall was lower,and both times caused “havoc on their environment plan”.

“Every day we don’t work up there it’s costing us $150,000, and that’s without damage costs,” he said.

“It will probably take us at least a week before we start work on the site again…

“But when this is about nature; we just do everything we can to keep things safe and secure.”

[box type=”info” style=”rounded” border=”full”]Keep an eye on the dam yourself with Dam Cam.[/box]