After assurances mining's return to the Braidwood district wouldn't damage the environment, it did just that in 2013 as soon as earthworks began. Then, after saying final processing of ore using cyanide would not be done on site, that is precisely what Unity is asking permission for in its latest planning application.

Unity Mining wants to do final processing of gold concentrate on site, but downstream, critics say this will create an even greater risk of pollution for their farms and water catchments for the South Coast.

When Unity Mining shelved plans to truck ore from Majors Creek to process at Parkes it said in 2013 it was looking at other options. "The final processing isn't resolved, except it certainly won't be done at Majors Creek," a Unity spokesman had said at the time.

Despite that assurance Unity is now proposing producing unrefined gold bars at the Dargues mine site, near Majors Creek, which requires a carbon-in-leach processing plant and cyanide as a leaching agent to remove the gold from the ore. The modification includes expanding a huge tailings dam from 9 to 16 hectares.

Concerns of heavy rain washing pollutants downstream are well founded, given the miner's guilty plea in the Land and Environment Court to polluting Spring and Majors Creek three times in 2013.

Unity had failed to install adequate sediment and erosion controls. After the heavy rain, muddy water was allowed to discharge from the construction site into the creeks. Unity was ordered to pay $103,000 for creek restoration work, and $93,000 for the Environmental Protection Authority's legal costs.

Unity says it has consulted on its latest plans through face-to-face meetings with community members around the mine site and discussions with land owners, government agencies and authorities.

The proponent says it has revised groundwater modelling, and has found peak inflows to the mine would be higher than originally modelled, but the modification would not result in adverse impacts on the surface water environment within and surrounding the project site.

Unity Mining's chief executive Andrew McIlwain says cyanide is common in the gold industry, and its bad reputation comes from the Second World War and spy movies, not the mining industry.

Unity Mining says mining and subsequent selling of gold ore will generate jobs and stimulate activity in Majors Creek and Braidwood communities, worth between $6 million and $10 million a year, and three times that amount at a state and national level.

But these are trifling figures when weighed against the worth of clean water catchments and food production downstream.

Landholders say if the modification is approved, instead of being trucked elsewhere, heavy metals will sit in a bigger tailings dam at the top of the Majors Creek/Deua/Moruya catchment, above Eurobodalla's water supply, and farms, businesses and households.

Unity is relying on environmental consultants to press its case for modification, but cannot rely on its recent track record at Majors Creek for government approval.