The project is about a third complete, with 30 of the 87 pre-fabricated wall extensions installed and construction started on the auxiliary spillway on Bulgas Road and a concrete spilling basin at the foot of the dam wall. 

The L-shaped wall extensions, weighing eight to 13 tonnes each and pre-fabricated at Clergate Road, will raise the dam wall by three metres and the spillway by a metre, raising the dam’s capacity by 10 per cent.

The upgrades will allow the dam to withstand a one-in-a-million-year flood. At this level, the water would reach 15 centimetres below the crest of the wall.

Orange mayor John Davis said the safety upgrades would add to water security.

“We needed water security and this is part of it. It just gives us that extra volume of water because we do have droughts,” he said.

“If we do find that we’re pumping [from the stormwater harvesting system or the Macquarie pipeline] and we’re at 65-70 per cent, this 10 per cent will help.”

He said the project was running on time and on budget so far.

Member for Orange Andrew Gee said the project could have been achieved sooner if it had not rained each time it was put on the agenda.

“We can’t afford to think like that anymore, we saw in the last drought how close we came to running out of water here,” he said.

“Some of the greatest accelerators and handbrakes on economic growth in this country is water security.”

Foundations for a secondary dam wall have been laid near Bulgas Road, which will eventually feature a series of concrete fuse gates. 

During extreme flood events, gates will open to control the release of floodwaters.

The concrete stilling basin will be anchored by a series of holes drilled 20 metres into the bedrock to prevent floodwaters undermining the dam wall’s strength.

danielle.cetinski@firfaxmedia.com.au