Safety Alert

What Happened

A section of pit wall measuring approximately 12 metres wide and 8 metres high collapsed in Pit 4, Zone B during a shift change period when no personnel or equipment were in the immediate area. The collapse occurred approximately 30 minutes after the area had been vacated for the shift change. Geotechnical prisms in the area had shown 4mm of movement in the preceding 48 hours.

Why It Matters

Pit wall failures can bury equipment and personnel with little or no warning. This collapse occurred in an area that was occupied just 30 minutes earlier. The geotechnical monitoring data showed signs of instability, but the rate of movement had not yet reached the evacuation trigger level, highlighting the need to review current thresholds.

Immediate Actions Required

1. 1Pit 4 Zone B to be barricaded and declared a no-go zone until geotechnical assessment is completed
2. 2Review all geotechnical monitoring trigger levels for Pit 4 — consider lowering evacuation thresholds
3. 3Install additional prisms and radar monitoring on adjacent wall sections
4. 4All crews working in Pit 4 to be briefed on the collapse and updated exclusion zone boundaries

Key Learning

Ground conditions can deteriorate rapidly. A wall that was stable one hour ago can fail without warning. Always respect exclusion zones, monitor geotechnical data, and if you see cracks, bulging, or unusual water flows on a pit wall — stop work and report immediately. Your observation could save lives.

Discussion Points for Toolbox Talk

• •Do you know how to identify visual signs of wall instability (cracks, tension rills, seepage, bulging)?
• •What would you do if you noticed movement or cracking on a pit wall during your shift?
• •Are you familiar with the geotechnical monitoring system and what the trigger levels mean for your work area?