Dam holds firm til the end

Jerrara Creek lapping the gardens of Terragong HouseWhile Kiama held national interest with the story of the imminent collapse of Jerrara Dam, the call to evacuate properties downstream was more of a precaution while the situation was assessed.

The situation looked more dire due to the wall having already been excavated as part of its long awaited decommissioning.

“The decommissioning project is two-thirds of the way through,” explains Kiama Council General Manager Michael Forsyth. “A section of the wall had been taken out, the channels widened and the spillway lowered.”

To do this work, the dam had been drained somewhat so that the water level was some metres below the new spillway. Even with that low starting level, the dam filled quickly from its small but steep catchment area.

“The project design for the decommissioning worked well, with all of the factors working as expected in such a scenario,” says Mr Forsyth.

The evacuation notice applied to ten properties, with two owners on higher ground choosing to stay. The students at Minnamurra Public School were also sent home due to its location near the river mouth.

Given the tragedies caused elsewhere by the speed of dam collapses, such precautions were justified.

The decommissioning of the dam is expected to be completed in four to six weeks’ time, at a total cost of $700,000.

Until the arrival of this East Coast low, August was shaping up as a dry one. In the first 24 days, we had 3.8mm of rain. In the next two, 248.4mm (9¾ inches).

 

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