Uncontrolled runs of materials continue to cause serious injuries and fatalities in Ontario mines
This hazard alert highlights where runs of materials occur, why they happen, notable fatal incidents, and the critical controls required to prevent worker exposure.
What is a run of materials?
A run of materials (also referred to as a run of muck) occurs when ore, waste rock, slimes, tailings, or other bulk material moves unexpectedly and uncontrollably due to gravity. These events are typically sudden, forceful, and often involve water, creating a high-risk situation for workers in the vicinity.
Runs of materials are generally low frequency but high consequence events — often resulting in crushing, burial, or pinning injuries.
Where it can happen
Runs of materials can occur in both underground and surface mining operations, including:
Surface and Processing Areas
- Truck dump chutes
- Conveyors
- Bins and hoppers
- Stockpiles
Underground Operations
- Loading pockets
- Crushing stations
- Ore and waste passes
- Draw points
- Conveyors
- Backfilling operations
- Stopes
- Mucking slimes or saturated material
- Chutes
Why it happens
The primary force behind material movement is gravity. The risk of failure can be influenced by:
- Material properties (size, shape, cohesion)
- Water content (wet or saturated material)
- Temporary or steep slopes
- Hung-up or bridged material
- Non-routine work activities
Water is a critical risk factor. While small amounts of moisture may help material bind, excessive water can turn fine material into a slurry that behaves like liquid. Incident investigations consistently show that wet or saturated material is present in most run-of-material events.
For more information on identifying and controlling risks from runs of materials, contact your local health and safety specialist.