Thirty-four homes were issued with alarms in 2012, which Orange City Council could trigger if evacuation was needed, but member for Orange Andrew Gee said the $18.94 million project would make a difference.

“I think those people are going to be absolutely delighted when the dam is strengthened, because it’ll give them a little bit more peace of mind and they won’t have to worry about their alarms so much,” he said.

Mr Gee said the state government would contribute 20 per cent of the cost, up to $3.8 million.

Work will include raising the spillway by one metre and the adjacent dam walls by three metres to increase water capacity by 10 per cent, strengthening the dam wall by anchor-bolting the structure to the rock foundations and rebuilding the western auxiliary spillway to release water in a controlled way in the event of a one in 500-year flood.

The dam’s outlet tower will be refitted so valves releasing water to the water treatment works can be operated automatically. Currently a staff member must climb internal ladders to manually open and close valves at different depths.

The dam can currently only withstand a one in 200-year flood, but will be improved to cope with a one in one million-year flood.

The tender documents have been sent to nine construction companies that will compete for the contract. 

Council infrastructure committee chair and councillor Reg Kidd said the strengthening would comply with requirements set by the state government’s Dams Safety Committee, which has spent recent years inspecting the state’s council-owned dams.

“It’s a very sophisticated engineering job to do the actual work,” he said.

However, he assured residents the dam wall did not present a danger in the meantime.

Orange mayor John Davis called it the total package.

“There’s one thing that’s certain, we’re going to have droughts, that’s a fact of life,” he said. We’d hope that we’d never use the extra capacity, but the realities are we probably will.”

Tenders will close in six weeks’ time.

The council anticipated work could start in October, with completion due in the first half of 2016.