Gold mine expansion put on hold after vent shaft released 18 times the regulatory limit of carcinogen

One of the world’s largest gold mines is set to put its expansion permit on hold after failing to meet a key condition for its production increase.

Newcrest’s Cadia Valley Operations (CVO) near Orange was found non-compliant by an independent air quality audit which found a vent shaft was emitting 18 times what is legally required to be safe levels of the carcinogen respirable crystalline silica.

In a statement, NSW’s Department for Planning and the Environment said they are investigating the matters raised in the independent audit report in conjunction with the NSW Environment Protection Authority (EPA).

In December 2021, a delegate from then Planning Secretary Rob Stokes approved the mine’s Modification 14, which aimed to fix the collapse of the northern Tailings dam and increase ore production from 32 million tonnes per year (TPA) to 35 million TPA.

A key condition for approving the change was that an independent air quality assessment report be approved by the planning secretary before production could ramp up.

The Zephyr Environmental Independent Air Quality Audit was commissioned by Cadia and approved by the Planning Secretary in February and completed in August of this year.

A final report in October 2022 provided two non-compliance findings not approving the Company’s increase in production.

Unbraked Windbreaker

The report found that CVO had failed to provide the department with an air quality validation report by March 2022.

Evidence has also been found of increased emissions from ventilation shafts, or “rises” in the mine ventilation network that draw in polluted air from Cadia’s underground mining operations and disperse it into the atmosphere.

VR8-1, known as the “Crusher Vent” because it extracts contaminated air from where ore is pulverized underground, emits 360 milligrams of particulate matter per cubic meter of air, including known carcinogenic respirable crystalline silica – 18 times the regulatory limit of 20 mg/m3. Oversize was also found at Vent Shaft 3 (known as VR3-1).

Neither VR3-1 nor VR8-1 were found to have dust mitigation measures in place such as mist sprays, dust collectors or a “scrubber system” used for crusher vents like VR8-1 which handle large amounts of particulates.

In response to the report’s findings, Cadia acting general manager Mick Dewar said the company had taken a number of mitigation actions.

“In addition to implementing short-term controls, such as additional dust suppression sprays on the two vent risers and additional surface air quality monitoring,” said Mr. Dewar

“Cadia has established a dust working group and commissioned a technical study supported by the University of Wollongong to implement dust control technologies at the source to further reduce particulate matter emissions through the air vents.”

Mr Dewar also said the company is “working proactively and constructively with the department to address these non-compliances and continues to communicate openly and transparently with the local community”.

Air pollution underestimated

The independent air quality audit, hailed as a community win when it was announced last year, has previously provided elusive details on dust formation and drift.

By examining the dust dispersion modeling used in the first Modification 14 project proposal by Cadia and his consultants, the audit was also able to identify a “significant” underreporting of particulate matter.

Resident group Cadia Community Sustainability Network (CCSN) said these historical gaps in the company’s monitoring and modeling made it all but impossible to get an accurate picture of community exposure.

“We all expected and trusted Cadia to comply with Australian environmental laws and health and safety standards,” said CCSN Chair Gemma Green

“We believe a license to mine our national resource is a privilege, especially when that resource is in close proximity to people’s homes.”

Mr Dewar said the potential excess of particulate emissions from two vent risers was only recorded at source.

“Exceedances were not detected at any of the four external air quality monitoring sites that are part of Cadia’s comprehensive air quality monitoring network.”

A timeline for granting the production increase is not known, with a spokesman for DPIE telling ABC they expect Newcrest to provide solutions first.

“The department has obtained additional information from the applicant on how the matters raised in the audit will be addressed and when those actions will be implemented,” the spokesman said.