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Mining and Mineral Processing Engineering Risk Assessment: Ground, Equipment and Process Control Hazards

A worked example of how a mine and concentrator team identifies, scores and controls the risks from ground failure, equipment defects, electrical work, reagents, tailings and supplier gaps.

Updated November 2026 8 hazards assessed Review every 6 months Highest risk: Critical to Medium
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Executive summary

This assessment shows how a mine and mineral processing team can find, rate and control the engineering and operational risks that threaten people, equipment, process performance and the environment. Eight risks were chosen because they are plausible on a hard rock site with an open pit, a concentrator and a tailings facility. Ground instability and tailings failure carry the greatest potential harm, while equipment failure, electrical isolation and maintenance backlog are more likely day to day. Each risk is scored before controls and again after existing and additional controls. Most residual scores fall to Medium or Low, but ground control and tailings stay at Medium because the consequences remain severe. The first actions are exclusion zones and alarm levels for slopes, personal locks for every electrical isolation, tailings alarm checks, and management of change for plant modifications. Every score is a teaching example and must be replaced by a formal site-specific assessment led by qualified engineers.

Focus area
Mining and mineral processing engineering
Setting
Surface and underground hard rock mine with an on-site ore concentrator
Method
Five by five likelihood and impact risk register

Scope

This assessment covers a hard rock mine and its on-site mineral processing plant, from ground support and haulage through crushing, grinding, flotation, tailings and maintenance. It looks at risks to people, equipment, process performance, the environment and the business. Jurisdiction, mine depth, ore type and the specific plant layout are not specified, so they are treated as assumptions made for teaching. The assessment is an educational example and does not replace a formal site-specific assessment.

Context

The example site runs an open pit feeding a primary crusher, a grinding circuit and a flotation plant that produces a concentrate for sale. Mobile equipment hauls ore and waste, and fixed plant includes conveyors, pumps, thickeners and a tailings storage facility. A maintenance team works in shifts, a supply chain brings in spares and reagents from outside suppliers, and an engineering group manages design changes. Each risk is scored before controls to show its natural level, then again after existing controls and the additional controls that are proposed.

Objectives, assets and stakeholders

The objective is to mine and process ore safely and reliably, meet the commitments made to the regulator and the community, protect people from ground, electrical and chemical harm, and keep the tailings contained. The assets in scope are the pit and underground workings, crushers, conveyors, grinding mills, flotation cells, pumps, the tailings storage facility, reagent stores and the maintenance workshop. Stakeholders include mine workers and contractors, the site leadership team, the geotechnical and process engineers, suppliers, neighbouring communities, the environment regulator and the owners. Every risk has one owner role, and the site general manager reviews the register with each department each quarter.

Risk matrix: before and after controls

Each cell shows hazard numbers placed by likelihood and impact. Compare the two grids to see how controls move each hazard.

Before controls

Inherent risk

Risk before controls: rows are likelihood from almost certain to rare, columns are impact from insignificant to catastrophic. Cells list hazard numbers.
1
Insignificant		 2
Minor		 3
Moderate		 4
Major		 5
Catastrophic
5 Almost certain
4 Likely Likelihood 4, impact 2, score 8, medium: H08 Likelihood 4, impact 3, score 12, high: H03 Likelihood 4, impact 4, score 16, high: H02 Likelihood 4, impact 5, score 20, critical: H01
3 Possible Likelihood 3, impact 3, score 9, medium: H07 Likelihood 3, impact 4, score 12, high: H05 Likelihood 3, impact 5, score 15, high: H04
2 Unlikely Likelihood 2, impact 5, score 10, high: H06
1 Rare

After controls

Residual risk

Risk after controls: rows are likelihood from almost certain to rare, columns are impact from insignificant to catastrophic. Cells list hazard numbers.
1
Insignificant		 2
Minor		 3
Moderate		 4
Major		 5
Catastrophic
5 Almost certain
4 Likely
3 Possible Likelihood 3, impact 2, score 6, medium: H03
2 Unlikely Likelihood 2, impact 2, score 4, low: H07 H08 Likelihood 2, impact 3, score 6, medium: H02 H05 Likelihood 2, impact 4, score 8, medium: H01 H06
1 Rare Likelihood 1, impact 5, score 5, medium: H04
  • Low 1 to 4
  • Medium 5 to 9
  • High 10 to 16
  • Critical 17 to 25

Hazard register

A summary first, then the detail for each hazard.

Summary of hazards with scores before and after controls
No.HazardBeforeAfterOwner
H01 Ground instability in pit walls and underground excavations 20 Critical 8 Medium Geotechnical engineer
H02 Crusher and conveyor failure from specification mismatch 16 High 6 Medium Process engineering manager
H03 Maintenance backlog and declining fleet reliability 12 High 6 Medium Maintenance superintendent
H04 Electrical isolation failure during maintenance 15 High 5 Medium Electrical engineering supervisor
H05 Reagent and chemical exposure in the flotation circuit 12 High 6 Medium Metallurgical process supervisor
H06 Tailings storage facility and water containment failure 10 High 8 Medium Tailings storage facility manager
H07 Spare parts and supplier dependency 9 Medium 4 Low Procurement manager
H08 Procedural deviation and human error in process control 8 Medium 4 Low Operations superintendent
H01

Ground instability in pit walls and underground excavations

Safety Before 20 After 8

Pit walls, benches, stopes or drives fail because of water pressure, weak rock, blasting damage or changes in excavation shape, causing falls of ground onto people and equipment.

Who or what is affected: Mine crews, geotechnical staff and haulage drivers

Causes

Weak or water bearing rock, poorly timed blasting and mining steeper than the design allows.

Consequences

Fatal or serious injury, equipment loss, production stoppage and a regulator investigation.

Existing controls

  • Geotechnical mapping is completed before each new bench or drive is opened.
  • Slope monitoring prisms and extensometers are read on a set routine.

Control gaps

Monitoring data is reviewed weekly, so a fast movement can develop between reviews.

Additional controls

  • Prevent: Set exclusion zones below highwalls and require a ground control review before any change in blast design.
  • Detect: Install radar slope monitoring with alarm levels agreed by the geotechnical engineer.
Likelihood 4 x impact 5 before; 2 x 4 after Owner: Geotechnical engineer Target: Within 30 days Early warning: Slope movement rate above the agreed alarm level on any monitored bench.
H02

Crusher and conveyor failure from specification mismatch

Operational Before 16 After 6

Equipment bought or modified without a full check against ore hardness, throughput and feed size fails early, forcing unplanned stops and surges that upset the grinding and flotation circuit.

Who or what is affected: Plant operators, maintenance crews and production planners

Causes

Ore properties that differ from the test samples and modifications made without a full design review.

Consequences

Repeated breakdowns, lost throughput, damage to downstream equipment and higher costs.

Existing controls

  • Equipment purchases follow a written specification signed by the process engineer.
  • Major changes are reviewed in a design meeting before installation.

Control gaps

Specifications are not updated after the ore grade or hardness changes over the mine life.

Additional controls

  • Prevent: Apply management of change to every modification and check the design basis against measured ore data.
  • Detect: Record vibration, temperature and throughput trends and compare them against the original design envelope.
Likelihood 4 x impact 4 before; 2 x 3 after Owner: Process engineering manager Target: Within 60 days Early warning: Crusher power draw or bearing temperature trending above the design envelope for two shifts.
H03

Maintenance backlog and declining fleet reliability

Operational Before 12 After 6

Planned servicing is deferred because of production pressure, so haul trucks, loaders, pumps and screens run beyond their intervals and fail in service.

Who or what is affected: Maintenance technicians, equipment operators and fleet planners

Causes

Production targets set above available maintenance capacity and parts that arrive late.

Consequences

Breakdowns, unsafe equipment in service, higher repair costs and missed production.

Existing controls

  • Preventive maintenance schedules are held in the maintenance system.
  • Operators complete a pre start inspection before each shift.

Control gaps

Backlog is measured by count, not by safety criticality, so critical items wait with routine ones.

Additional controls

  • Prevent: Protect a fixed weekly maintenance window and link production targets to planned equipment availability.
  • Detect: Review backlog size and mean time between failures each week and publish the trend.
Likelihood 4 x impact 3 before; 3 x 2 after Owner: Maintenance superintendent Target: Within 45 days Early warning: Overdue critical maintenance tasks above an agreed number for any fleet type.
H04

Electrical isolation failure during maintenance

Safety Before 15 After 5

Equipment is restarted or energized while a technician is working on it because isolation, locking and testing steps are skipped, wrong or not checked, exposing staff to electric shock, arc flash and stored energy.

Who or what is affected: Electricians, mechanics and contractors working on fixed plant

Causes

Pressure to restart quickly, unclear drawings and contractors who do not know site rules.

Consequences

Electrocution, burns, arc flash injury, uncontrolled release of stored energy and loss of life.

Existing controls

  • Isolation points are labelled on single line diagrams held at the switchroom.
  • Work permits require a named isolation point before work starts.

Control gaps

Permits are checked on paper and are not confirmed at the point of isolation.

Additional controls

  • Prevent: Use personal locks and a proven dead test for every isolation, and forbid shared keys.
  • Detect: Audit a sample of permits each month against the physical isolation found in the field.
Likelihood 3 x impact 5 before; 1 x 5 after Owner: Electrical engineering supervisor Target: Within 30 days Early warning: Any work permit found without a matching physical lock or proven dead test.
H05

Reagent and chemical exposure in the flotation circuit

Safety Before 12 After 6

Process reagents such as collectors, frothers, acids and alkalis are mixed, dosed or stored incorrectly, releasing corrosive or toxic substances, mist and fumes into work areas and drains.

Who or what is affected: Reagent handlers, plant operators and laboratory staff

Causes

Manual mixing, mislabelled drums and dosing pumps that run without checks.

Consequences

Chemical burns, respiratory harm, contamination of water and fines or plant closure.

Existing controls

  • Safety data sheets are kept at each reagent store and reviewed each year.
  • Reagents are stored in bunded areas with labelled containers.

Control gaps

Dosing rates are set by feel in some areas and are not checked against the recipe.

Additional controls

  • Prevent: Use closed dosing systems and substitute the most hazardous reagent where the process allows.
  • Respond: Practise spill response with bunding, neutralising material and an emergency shower check each quarter.
Likelihood 3 x impact 4 before; 2 x 3 after Owner: Metallurgical process supervisor Target: Within 45 days Early warning: Reagent level or dosing rate outside the recipe range for more than one hour.
H06

Tailings storage facility and water containment failure

Environmental Before 10 After 8

Tailings dam walls, decant structures or pipelines leak, overtop or fail after heavy rain, seepage or poor beach deposition, releasing slurry and contaminated water into the environment.

Who or what is affected: Downstream communities, environmental staff and site workers

Causes

Extreme rainfall, rising water levels, poor drainage or weak foundations.

Consequences

Environmental damage, regulatory action, harm downstream and loss of the licence to operate.

Existing controls

  • The tailings dam is inspected by a competent person each shift.
  • Water balance and freeboard levels are recorded daily.

Control gaps

Seepage readings are reviewed after the shift, so early seepage can grow unseen.

Additional controls

  • Prevent: Keep freeboard above the design minimum and manage beach deposition through a written plan.
  • Detect: Fit piezometers and seepage monitoring with alarms set by the tailings engineer.
Likelihood 2 x impact 5 before; 2 x 4 after Owner: Tailings storage facility manager Target: Within 30 days Early warning: Piezometer reading or seepage flow above the alarm level set by the tailings engineer.
H07

Spare parts and supplier dependency

Supplier Before 9 After 4

A single supplier or long lead item for critical spares, reagents or specialist services fails to deliver on time, or delivers parts that do not meet the specification, leaving key plant stopped.

Who or what is affected: Maintenance crews, procurement staff and production planners

Causes

Single source suppliers, long lead times and remote site logistics.

Consequences

Extended outages, unsafe repairs with non-approved parts and cost overruns.

Existing controls

  • Critical spares are listed and stocked to a minimum level.
  • The approved supplier list is reviewed each year by procurement.

Control gaps

Stock levels are set by cost, not by criticality, and second sources are not tested.

Additional controls

  • Prevent: Qualify a second supplier for the top critical spares and check incoming parts against drawings.
  • Recover: Agree emergency delivery terms and a loan arrangement for critical equipment.
Likelihood 3 x impact 3 before; 2 x 2 after Owner: Procurement manager Target: Within 60 days Early warning: Critical spare stock below minimum, or a supplier delivery more than two weeks late.
H08

Procedural deviation and human error in process control

People Before 8 After 4

Operators bypass alarms, skip steps in start up or shutdown, or make manual setpoint changes without authority, so the plant drifts outside safe or efficient operating limits.

Who or what is affected: Plant operators, shift supervisors and contractors

Causes

Alarm overload, fatigue on long shifts and unclear rules on changing setpoints.

Consequences

Plant upset, equipment damage, product off specification and injury during restart.

Existing controls

  • Standard operating procedures are displayed at each control station.
  • Operators complete a shift handover log for every shift.

Control gaps

Alarm floods are not reviewed, and bypasses are not logged consistently.

Additional controls

  • Prevent: Limit manual overrides to a named supervisor with a written reason and a time limit.
  • Detect: Review alarm logs and bypass records each week and feed findings into training.
Likelihood 4 x impact 2 before; 2 x 2 after Owner: Operations superintendent Target: Within 60 days Early warning: An alarm bypass active for longer than one shift or more than a set number of overrides in a day.

Rating method and evaluation

Each risk is rated on two five-point scales. Likelihood runs from 1, rare, to 5, almost certain, and impact runs from 1, minor, to 5, severe, covering injury, environmental harm, production loss and cost. Multiplying the two gives a score from 1 to 25 in one of four bands: Low from 1 to 4, Medium from 5 to 9, High from 10 to 16 and Critical from 17 to 25. Inherent risk is the score before any controls, and residual risk is the score after existing and additional controls are in place. A residual score can never be higher than the inherent score, and where the inherent score is 10 or more the residual must be lower. Any Critical or High residual needs senior attention and a dated plan, Medium needs routine control with a named owner, and Low is accepted and monitored. Safety and environmental impacts are never rated down only because they are unlikely to happen, and specialist engineers should check every score. Ratings are challenged by the people who do the work at toolbox talks and review meetings, and a rating is reopened whenever a warning indicator reaches its threshold or a change of plant, ore or supplier occurs.

Likelihood, impact and rating bands

Likelihood

  • 5 Almost certain: Expected to happen in most circumstances.
  • 4 Likely: Will probably happen in many circumstances.
  • 3 Possible: Could happen at some time.
  • 2 Unlikely: Not expected, but it could happen.
  • 1 Rare: Only in exceptional circumstances.

Impact

  • 1 Insignificant: No lasting effect. Handled within routine work.
  • 2 Minor: Small effect that is quickly corrected.
  • 3 Moderate: Noticeable effect that needs managed effort to correct.
  • 4 Major: Serious effect on people, delivery or reputation.
  • 5 Catastrophic: Severe or lasting effect that threatens the whole activity.

Bands (likelihood x impact)

  • Low (1 to 4): Accept and monitor.
  • Medium (5 to 9): Manage with routine controls.
  • High (10 to 16): Senior attention and a treatment plan.
  • Critical (17 to 25): Act first. Do not proceed until reduced.

Monitoring, escalation and review

Review this assessment every 6 months, and sooner when an indicator below reaches its threshold.

Early-warning indicators and escalation thresholds
Indicator to watchEscalate when
Slope movement or piezometer readings above alarm levels.Escalate to the geotechnical engineer at once and to the mine manager if movement continues for two readings.
Overdue critical maintenance tasks on the fleet and fixed plant.Escalate to the maintenance superintendent when overdue critical tasks exceed the agreed count, and to the site general manager if still open after one week.
Work permits without a matching physical isolation check.Stop the work and escalate to the electrical engineering supervisor the same shift.
Reagent dosing outside recipe range or spill events.Escalate to the metallurgical process supervisor the same shift, and to the environment lead for any release to drains.
Critical spare stock below minimum or supplier delivery overdue.Escalate to the procurement manager when stock falls below minimum, and to the operations director if an outage is expected.

Contingency arrangements

If a ground fall, tailings alarm or major electrical incident occurs, the shift supervisor stops work in the affected area and sounds the emergency alarm. Emergency response teams are called and the site general manager is informed at once. The geotechnical engineer or tailings engineer assesses the hazard before any entry, and plant isolation is confirmed with the electrical supervisor. Injured people receive first aid and medical help, and relevant regulators are notified as required in the jurisdiction. Production restarts only after the affected equipment or structure is cleared by a competent engineer, and staff receive a plain briefing on what happened.

Prioritized action plan

  1. Confirm the highwall exclusion zones and radar alarm levels, owner geotechnical engineer, within 30 days.
  2. Enforce personal locks and proven dead tests for all electrical isolations, owner electrical engineering supervisor, within 30 days.
  3. Review tailings freeboard and seepage alarm levels, owner tailings storage facility manager, within 14 days.
  4. Apply management of change to every plant modification and refresh the design basis, owner process engineering manager, within 60 days.
  5. Qualify second suppliers for critical spares and protect a weekly maintenance window, owner procurement manager, within 60 days.

Conclusion

Safe and reliable mining and mineral processing depend on a few steady habits: respecting ground limits, proving every isolation, keeping maintenance ahead of production, checking every change against the design basis, and watching tailings and water levels closely. The highest scores sit with ground instability and tailings containment, and each has actions that bring the residual risk down. Treat the register as a living record, review it on the stated cycle, and seek qualified engineering, safety and environmental advice for any real site decision.

Assumptions and limitations

Assumptions

  • Jurisdiction is not specified, so legal duties are described in general terms and must be confirmed locally.
  • The site uses a diesel mobile fleet, electric motors on fixed plant and a single tailings storage facility.
  • Staff are trained operators, technicians and engineers, with contractors working under a site permit system.

Limitations

  • The scores are examples for learning and do not describe any real mine or plant.
  • Ground, electrical, chemical and tailings engineering require specialist review by qualified professionals before any decision.
  • This is educational content and is not engineering, safety, legal or environmental advice.

Related frameworks to study

  • Hierarchy of controls
  • Bow tie analysis
  • Failure mode and effects analysis
  • Management of change process
  • Layers of protection analysis

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For Learning Reference Only: This assessment demonstrates how risk assessment principles are applied in a practical setting, providing a useful reference for learning and understanding. Actual assessments may be adapted to suit specific site conditions and circumstances.

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