ULAN coal mine can extract an extra 6 million tonnes of coal after the Independent Planning Commission said concern about mine discharge salt levels into the Goulburn River was a matter for the Environment Protection Authority.
The giant Glencore mine between Denman and Mudgee said the approval would result in an extra four months of coal production at the complex which has approval to continue underground coal mining until 2033.
Increasing underground panels would maximise coal production and provide further security for the mine's 930 workers, provide another $40 million in royalties to the NSW Government and was unlikely to have significant environmental effects, Glencore said.
The Department of Planning told the commission the modification of the original mine approval was in the public interest.
But objectors say bigger issues about water and the cumulative impacts of three very large mines close to the Goulburn River were not addressed by the company or the department.
Objectors including Hunter Communities Network spokesperson Bev Smiles, Goulburn River resident Julia Imrie and Mudgee District Environment Group said issues including the current leakage of saline water into the river from the project's east void required action before further expanding mining.
Objectors also raised concerns about the cumulative impact of mining on the Goulburn River, the iconic landform known as The Drip, and the need for the salinity load impact of mine discharges to be considerably reduced.
Ms Imrie, who with husband Colin Imrie has owned property neighbouring The Drip and the Goulburn River since the 1970s, and is completing a doctorate on water impacts within the area, said The Drip's future remained uncertain because coal mining had trumped environmental concerns in the Goulburn River area for decades.
"Open cut and longwall coal mining in the headwaters of the river at Ulan have been extracting increasing amounts of groundwater and intercepting rainfall runoff for many years," Ms Imrie said.
"Water excess to mine needs at Ulan and Moolarben mines is discharged, partially treated, down the river.
"Plans for more underground mining close to the river puts it at further risk."
Plans for more underground mining close to the river puts it at further risk.Julia Imrie
The Independent Planning Commission acknowledged saline water leakage from the Ulan mine into the Goulburn River was "an existing situation that requires management from the proponent" but said surface water discharge levels would not change because an extra 6 million tonnes of coal is mined.
The commission said salinity discharge limits were set by the EPA, a cumulative impact assessment of mine impacts on water supplies would require the participation of Ulan plus nearby Wilpinjong and Moolarben.
In its decision published on July 17 the commission said it was required to assess a mine proposal on its merits.
The cumulative impact of mines is a responsibility of the NSW Government.
A four-kilometre diversion of the Goulburn River in the 1980s to accommodate mining needs at Ulan was slammed by Ms Imrie as a "travesty and example of mining at its worst".
Glencore continues attempts to remediate the river "canyon" left after the Goulburn River was diverted from its natural course to follow the mine's southern and eastern boundaries under previous owners.