The rock ramp will reduce the risk of drowning at the weir, while the fishway will help with the migration of the fish.

Council's director technical services Stewart McLeod said while the weir has served Dubbo well, there had been significant safety issues.

"Since 1942 unfortunately nine people have drowned at this location at different times," he said.

"There was half a dozen people who drowned quite early on in the life of the weir. It then went for about 40 years without a fatality but in 2008 and then again in 2011 very unfortunately two young Dubbo men drowned and the community became quite concerned with the safety of the weir."

The rock ramp was the preferred option chosen by council and the stakeholders during a value management study in 2013.

"After the drownings happened, especially the second drowning in 2011, a lot of thought started to go into do we need the weir, what do we need to do to make the weir safer. The conclusion was very clear that for water security for Dubbo the weir was essential. We couldn't just demolish it," Mr McLeod said.

As well as the rock ramp, the buoys upstream and downstream would be replaced as another added safety feature to prevent swimmers and boats nearing the rock ramp.

Construction started in March, and unless there was a flood in the river, Mr McLeod said it would be completed by mid-September. 

He said while there had been a "worrying time" for two or three weeks when there was more seepage than expected, David Payne Constructions had managed to find a solution to the problem.

"It's radical work to be filling the river. It's radical work to be doing this fishway in general anyway. It is just a fact of life that we knew from 2013 onwards if we could get this done by 2016 we would be making good progress," Mr McLeod said.

However, people had been very excited, with council receiving nothing but positive comments on the work, he said.

Western Plains Regional Council administrator Michael Kneipp said it was terrific to see the tender awarded to a local contractor.

"For a job of this complexity, to be able to award it to a local business is just fantastic. I think that's great policy," he said.

Mr Kneipp said with safety paramount it was also good to see council taking leadership on the issue.

"It's vital to the water supply for Dubbo both to domestic households and industry in Dubbo and of course the environmental considerations are paramount as well; even thought the weir is there we've mimicked the natural flows as much as possible so that we can preserve fish habitat," he said.