So four kilometres of a key tributary to the Hunter River was diverted to the mine’s southern and eastern boundaries and Ulan’s expansion went ahead, with a most recent approval allowing mining until 2031 and production of up to 20 million tonnes of coal per year.

When mining finishes at Ulan the Goulburn River won’t be going back to its former course across the site. It will remain a “canyon” shape running parallel to Ulan Road, with straight sides up to 20 metres deep in places, thick reed beds to stabilise sediment and some remediated sections to reduce erosion and soften the appearance of a river reduced to a deep mine ditch.

Other Hunter waterways have been notoriously diverted or undermined, but the brutal lines of the Goulburn River on Ulan land – with the mine now owned by Glencore – are the most stark and permanent proof of the natural environment’s lost battle with coal.

“The approval and sign-off on diversion of the Goulburn River was a travesty and example of mining at its worst,” said long-time Goulburn River campaigner, environmental scientist and Goulburn River property owner Julia Imrie.

Lock the Gate spokesperson Georgina Woods said the river “is illustrative of the larger environmental challenges the Hunter is going to face in the coming decades, managing dozens of mining voids, altered streams and rivers and disturbed soils”. 

“The Goulburn River diversion mess reminds us that it takes very little time to ruin four kilometres of river, but many years of complex trial and error to remediate it,” she said.

The Goulburn River Diversion – its name since 1981 when one of Australia’s richest men, mining magnate Brian Flannery, was Ulan’s project manager – is a long way from most places, but it is also a rallying cry for environment and community groups concerned about the legacy of Hunter coal mining on the region’s waterways, including the Hunter and Goulburn rivers.

"The 30-year delay between the damage being done to the Goulburn River and the remediation project getting underway underscores a long-term risk for the rest of the region,” Lock the Gate spokesperson Georgina Woods said.

"Ulan is still operating, so Glencore is present and has cash to fund this work. How will we deal with legacy problems that arise 30 years from now? Will those responsible still be here to deal with them, and will there be money to pay to clean it up?”

It was not until 2017 – 36 years after the Diversion was approved by the NSW Government – that the NSW Department of Planning signed off on a revised remediation plan for the Diversion, after years of erosion and campaigning by environment groups.

Julia Imrie and environmental activist Bev Smiles say it was only the mine’s expansion during the coal boom that allowed remediation of the Diversion to be used as leverage, and included as a condition of consent. The condition was endorsed by a court in 2011 after Hunter Environment Lobby challenged the approval because of concerns about groundwater and emissions impacts.

The bigger battle for the Goulburn River continues, with groups increasing their demands for a full and independent study of the river headwaters in the Ulan area to include the impact of mining. The demand comes more than 30 years after the former NSW Water Resources Commission warned that just the Ulan mine would “eliminate the most worthwhile groundwater source in the area and is likely to have deleterious effects on both groundwater and surface water resources”.

There are now three large mines in the same area – Glencore’s Ulan, Yancoal’s Moolarben and Peabody’s Wilpinjong. In the 2011 Ulan Land and Environment Court case a judge noted it was indisputable the mine would cause “long-term depressurisation of groundwater within the mine footprint and beyond” which would take “a fair bit longer than 200 years for groundwater to recover”. The loss of baseflow for the Goulburn River caused by just the Ulan mine was “not a negligible impact”, the judge said.

All three mines have applied or been granted increases in the amount of treated mine water they can discharge into the Goulburn River, as their operations below the water table cause groundwater to enter the mines, in some cases beyond original modelling predictions. While Wilpinjong’s discharges must have a salinity load of 500EC or less, which is roughly the salt load of the river above the mines, Moolarben and Ulan can discharge water up to 900EC under current Environment Protection Authority licences.

For more than 30 years Julia Imrie has argued for an independent cumulative impact study on the river, which flows for 225 kilometres to become a vital part of the “flushing out” process to keep the Hunter River’s salinity at acceptable levels.

In submissions to the NSW Government she has argued the mines now control the river because of the amount of groundwater being drawn to them from surrounding areas, which is returned to the river as treated mine water with elevated salt loads.

“The water goes somewhere and comes from somewhere,” Ms Imrie said.

“The minute an expanded Ulan mine was approved the river stopped being a natural waterway because the water flow is now largely controlled by what the mine discharges.”

The Department of Planning approved a revised Glencore Goulburn River Diversion remediation plan in 2017 after the company said investigations into an approved 2011 plan found “constructability” and “environmental risk” problems.

The company committed to completing remediation work aiming to “maintain the long term geomorphological stability of the river landform, restore resilient revegetation cover throughout the channel areas and mitigate negative offsite impacts from erosion within the diversion”.

The work would “lead to improved visual amenity”, the diversion plan said.

“These objectives have been developed in the context of considering the channel as a diversion as per its original design, rather than attempting to recreate a pre-construction (pre-1980) condition,” it said.

An expert panel advised on the revised plan. Ms Imrie said the company had given some commitment to fully stabilising the diversion to protect against extreme storm events and leakage of groundwater from an old mine area.

An Environment Protection Authority spokesperson said while Moolarben had applied to increase its daily discharge limit to 20 megalitres, it had only discharged water into the Goulburn River once since 2010 following a declared natural disaster storm event.

Ulan mine was required to spend $35 million on pollution reduction works after an Environment Protection Authority assessment in 2014. The EPA recently informed the mine it will be reviewing salinity licence limits for discharges after monitoring showed average 600EC levels downstream of Ulan mine.

It said Wilpinjong’s salinity limit was set at 500EC – lower than the 900EC for Moolarben and Ulan - based on upstream water quality.