Coal Inspectorate | Bulletin | No.214 V 1 | 29 August 2023

Dozer falls into coal stockpile void

What happened?

On 4 November 2022, a bulldozer fell backwards into a coal valve void during train load-out operations. The investigation for this incident has now closed with a number of recommendations listed below, to avoid future dozer stockpile incidents. This particular incident was one of several involving dozers from 2022 and 2023.

How did it happen?

Preparation for train load out had been conducted on the previous shift by constructing a ramp onto the stockpile to the assumed position of the coal valve. At the time of preparing the stockpile, the coal valve was closed and it is probable that the valve became bridged partly due to pushing significantly beyond the valve position.

The site applied physical indicator poles outside of the stockpile footprint for dozer operators to use as a visual reference. This visual reference provided only one part of a grid reference required to identify the voids actual position. The indicator poles were not necessarily visible by dozer operators at all times because of the height and shape of the stockpile. There were no other indicator poles to provide a secondary (right angle) reference point for the void position, however, the reclaim conveyor is commonly used for this purpose.

During the shift when the incident occurred, there were two dozers assigned to stockpile push operations for train load out. Just prior to the incident, the operator of the dozer involved in the incident (dozer no.1) had line of sight for the second dozer. Dozer no.2 was on the southwest side of the stockpile. It was assumed by the operator of dozer no.1 that dozer no.2 was pushing into the coal valve position. An assumption was made by the operator of dozer no.1 that coal was flowing due to coal dropping off the blade of dozer no.2. There were no positive communications made between the two dozer operators at this point.

At the site where the incident occurred, it was a requirement of the site’s Standard Operating Procedure (SOP) to visually confirm the coal valve location when the coal valve turned live. On this occasion, the bulldozer push commenced before operators visually confirmed the coal valve location. Dozer no.1 pushed coal to the position where the coal valve was thought to be after observations of dozer no.2 previously mentioned. Dozer no.1 conducted a second push to the same position and while reversing, dozer no.1 slumped backwards into a void created by the coal valve which was behind them and the material thought to be bridging the valve letting go. The operator was recovered by the Emergency Response Team (ERT) without injury.

Key issues

The investigation identified that:

• GPS unit was not fitted in dozer no.1 at the time of the incident.
• GPS units are not programmed with feeder locations.
• geo fencing was not a control practiced at the site for tasks of this risk profile.
• operators did not conduct positive communications.
• operators did not confirm the coal valve location before pushing.
• coal bridging occurred when the coal valve opened, and coal feed commenced.

Recommendations

Site Senior Executives (SSEs) should:

• review effectiveness of site systems for coal stockpile management. This must include a review of the underpinning risk management for those systems.
• identify operational areas that are considered to be 'high risk tasks'. Some examples are, but not limited to, coal stockpiles, working near bodies of water, bund construction or bench preparation in areas identified by section 18 of the Coal Mining Safety and Health Regulation 2017.
• implement engineering systems that can assist in identifying coal valve positions (e.g. GPS-enabled mobile plant).
• implement geo fencing capability on the operational mobile plant.
• ensure operators are complying with Safety and Health Management System (SHMS) requirements.
• review both aided and self-escape strategies for the scenario of dozer engulfment on coal stockpiles.
• review current self-contained breathing apparatus capacity (fit for purpose) available in mobile plant working on stockpiles. The risk management system should consider the placement of this equipment if the cabin of the mobile plant is inverted or on its roof. Self-contained breathing apparatus must be restrained so it doesn't become a projectile in a rollover. The risk of heat damage from direct sunlight or excessive ambient temperature in the cabin of the mobile plant must also be considered.
• commence due diligence and risk management for implementing semi-autonomous or autonomous dozer operations in areas considered to be 'high risk' as previously mentioned.
• review their site's risk profile if coal valves are used as a preference to stacker reclaimers. SSEs should review the risk management underpinning the decision made for design, construction and operation of infrastructure for coal stockpile management.