Since the McArthur River was diverted to make way for the McArthur River zinc and lead mine in 2007, Indigenous leaders including Jack Green living downstream at Borroloola depend on an annual independent monitor report on the mine to alert them to problems. 

"I am worried about what they are going to do, when they close down, they could walk away and leave us with problems," he said.

The independent monitor system was established as a condition of the Northern Territory government's 2006 approval for the mining company to divert the McArthur River so it could expand the mine from an underground to an open cut operation.

The special monitoring system put in by the Northern Territory government just for this mine has been particularly important for the past seven years after the mine's waste rock dump began spontaneously combusting.

In 2018, when environmental consultant Erias Group was carrying out the independent monitor role, its last report detailed a catalogue of continuing problems including that the waste rock dump was still leaking acid and reacting at 70 degrees Celsius.

The following year, the government appointed a new monitoring company, Advisian.

This year, Advisian reported the mine had a high level of compliance and environmental performance and the McArthur River was healthy.

Tender documents obtained by the NT Environment Centre under Freedom of Information show the government changed the scope of the monitoring from an environmental assessment to a compliance audit, and accepted a much cheaper tender.

It had estimated the monitoring cost would be $2 million for three years, but accepted Advisian's tender to do it for $350,000 for the same period, noting that there were "significant changes to the outputs required".

The Mines Department recommendation to appoint Advisian said: "The proposed cost … is 80 per cent lower than the estimate.

"The reason for the significant disparity is … due to a refinement of the scope."

"Previously, the independent monitor had a very wide scope to scrutinise the impacts of this mine and to identify risks," the Environment Centre's Director Kirsty Howey said.

"Now we see the reduction of the scope to essentially what's a tick and flick exercise against a variety of conditions that are imposed by the government.

"That's not independent, it's not rigorous, and there are serious questions about whether it is possible to do very much at all with that amount of money."

The government wrote into the contract that it can order that "any error, ambiguity or deficiency … shall be corrected or clarified".

"The department seems to have retained the ability to have the final say on what that independent monitor report says and that means that you just can't call it an independent report at all," Ms Howey said.

In its tender, Advisian said it would work to increase community trust in the mine.

"If we are finding engagement mechanisms are not supporting improved trust levels between the local community, McArthur River Mine and government, we will … identify alternative engagement options," it said.

Gavin Mudd is an associate professor of environmental engineering at RMIT University who has studied the independent monitor's role for years.

"It was always expected to be an independent umpire looking at the scientific data and providing a clear, neutral view on what that data shows, like: Why? What does it mean?" he said.

Advisian referred the ABC's request for comment to the NT government.

The ABC asked the NT government for a response on August 12.

Several days later, the NT government provided a statement saying on August 13, it had approved an extra $1 million for Advisian's monitoring, and it has raised the contract to a total of $1.5 million over three years.

The government said that was because it realised more hours than first allocated were needed to carry out the monitoring work.

However, Kirsty Howey is calling on the federal government, which already monitors the NT's Ranger uranium mine beside Kakadu National Park, to step in and take over the same role for the McArthur River Mine.

"We need a Commonwealth intervention to be able to monitor this mine properly," she said.