The dozer was being towed by a second dozer down the mine ramp to an in-pit maintenance area with an excavator being used as a brake stop when a recovery sling failed and another disconnected.
This resulted in the unoccupied dozer rolling down the ramp.
According to an investigation by the NSW Resources Regulator, no workers were injured in the incident.
Workers from three different contracting companies undertook the recovery of an inoperable Caterpillar D10T2 dozer that required it to be conveyed to an in-pit maintenance area at the mine on January 15.
Initially, a float was arranged to relocate the dozer but it was later identified to be unsuitable for the task and was not used.
The workers completed a job hazard assessment that identified towing the dozer to the maintenance area using a Caterpillar 992-wheel loader, with a Caterpillar D11T dozer used as a brake stop.
The JHA also required the axles of the D10 dozer to be removed for free movement of the tracks.
When the task was ready to start, the wheel loader was not available and a decision was made to deviate from the JHA and use the D11 dozer as the tow machine with a 36-tonne excavator used as a brake stop.
"Preliminary inquiries indicate the JHA was not reconsidered and the risks arising from the work task were not reassessed once the wheel loader was no longer to be used as part of the recovery, and the function of the D11 dozer changed," the regulator said.
At about 3pm the workers started towing the D10 dozer down the ramp towards the in-pit maintenance area. No supervisor was present in the area at this time.
"Mine operators and contractors are reminded of their duty to identify hazards and manage risks to health and safety in accordance with the provisions of the Work Health and Safety Act 2011 and Work Health and Safety (Mines and Petroleum Sites) Act 2013 and Regulations," the regulator said.
"In particular, mine operators and contractors must ensure fit-for-purpose plant, towing equipment and tow and lifting points are used as designed and in accordance with towing procedures to ensure recovered plant remains suitably restrained to prevent uncontrolled movement."