Tahmoor coal mine operators have introduced new protocols to avoid a repeat of last year’s incident that caused two miners to be trapped underground.
Two men were stuck 160 metres underground and rescued eight hours later following the mechanical failure of a lift at the SIMEC Mining facility on September 5.
No-one was hurt during the incident.
The Department of Planning and Environment’s resources regular conducted an investigation. Their findings revealed the likely cause was an unbalanced counterweight.
SIMEC Mining chief operating officer Matt Reed said his company worked closely with regulator through the investigation which was “very efficient in identifying the root cause”.
Mr Reed said SIMEC had already introduced control measures to prevent a re-occurrence of the September incident.
“The safety of everyone involved in our business is a priority,” he said.
“This process has enabled learning outcomes that can be shared across industry.”
Representatives from the Tahmoor colliery and the Construction, Forestry, Maritime, Mining and Energy Union (CFMEU) assisted the Department of Planning with the investigation.
Department of Planning chief compliance officer Anthony Keon said the incident’s most likely cause was a misaligned winder counterweight which struck a water ring 240 metres below the surface and ripped it from the shaft’s wall.
“The water ring became wrapped around shaft services, winder head ropes and balance ropes, pulling them out of alignment and tripping the winder protection circuit,” he said.
“A contributing causal factor was found to be uneven tension on the ropes holding the counterweight which caused it to rotate and come into contact with the shaft wall while it was moving.”
Mr Keon said the report also found monitoring of the rope tensions “wasn’t fully covered by maintenance and inspections”.
“Some of the early indicators of the problem that caused the incident were not communicated to senior management to action,” he said.
The Tahmoor Coking Mine was closed for five weeks following the incident.
Colliery staff were redeployed into assisting with community projects around Wollondilly while the mine was temporarily suspended.
Community projects to benefit included the painting posts and rail fencing at Bargo sports fields, repairing potholes on the road to Thirlmere Lakes National Park and a general clean-up of the Thirlmere Rail Museum.
Mr Reed said SIMEC’s performance had been “outstanding” since the colliery re-opened in mid-October.
“I’d like to thank our workforce for their commitment and hard work throughout this entire period,” he said.