6.2 Risk Matrices and ALARP

6.2 Risk Matrices and ALARP

Quick Answer: A risk matrix multiplies or combines likelihood and severity to rank risk. ALARP (As Low As Reasonably Practicable) means you reduce risk until further reduction would cost grossly more than the safety benefit gained—and you must document that decision.

After HEMP Identify, supervisors Assess risk so resources go to the biggest threats. Most Nigerian industrial employers use a risk matrix (often 5×5) defined in the HSE-MS. Level 3 candidates must read a matrix, apply it consistently, and explain ALARP without treating it as a slogan that excuses weak controls.

What “Risk” Means in Assessment

In workplace HSE:

• Hazard = potential source of harm
• Risk = combination of the likelihood of a hazardous event and the severity of its consequences

You assess risk with existing controls (current risk) and again with proposed additional controls (residual risk). Examiners care whether you claim “low risk” while critical barriers are missing.

Anatomy of a Risk Matrix

A typical matrix has:

Severity may consider people, environment, asset, and reputation (PEAR). A small spill might be Medium for environment but Low for people; an H₂S release might be Extreme for people even if asset damage is limited. Use the worst credible consequence the company matrix requires—not the best-case fantasy.

Qualitative vs Semi-Quantitative

Level 3 focuses on qualitative and semi-quantitative practice. Semi-quantitative scoring helps compare tasks (“12 vs 6”) but false precision is a trap: a score of 12 is only as good as the judgment behind the 3 and the 4.

Scoring Likelihood Honestly

Likelihood rises when:

• Exposure is frequent (daily task vs once a year)
• Many people are exposed
• Controls are weak, bypassed, or untested
• Conditions are degrading (rainy season, night, SIMOPS, new contractors)
• History shows near misses

Likelihood falls when robust engineering and proven procedures are in place and verified. Do not lower likelihood simply because “nobody has been hurt yet.”

Scoring Severity Honestly

Severity reflects credible harm:

• First aid vs lost-time injury vs fatality / multiple fatalities
• Localised spill vs creek/river contamination affecting communities
• Minor equipment damage vs major fire/explosion

For work at height without fall prevention, severity of a fall from significant height is typically High/Extreme even if the worker is experienced. Experience reduces some error likelihood; it does not make gravity optional.

Using the Matrix in Supervisory Workflow

1. List significant hazards from Identify.
2. For each, judge likelihood and severity with current controls.
3. Read the matrix colour/score and action rule (e.g., red = stop / escalate).
4. Add controls using the hierarchy.
5. Re-score residual risk.
6. Decide if residual risk is tolerable / ALARP; if not, do not proceed.

Nigerian examples:

• Scaffold erection beside live plant: likelihood Medium if competent scaffolders and exclusion zones exist; severity High for falls and dropped objects → amber/red until additional controls.
• Manual excavator work near buried cables without locates: likelihood may be Medium-High; severity Extreme for electrocution/explosion → do not start until cable detection and permits confirm safe dig.
• Routine office ergonomics complaint: often lower matrix priority than process safety threats, but still manage via OH pathways—matrix priority is relative, not a reason to ignore health.

ALARP — Meaning for Supervisors

ALARP means risk is reduced As Low As Reasonably Practicable. The idea (rooted in UK common-law/regulatory thinking and widely used in oil & gas and major hazard industries globally, including Nigerian IOCs and many contractors) is:

• You must implement risk reduction that is reasonably practicable.
• You may stop adding measures when the sacrifice (cost, time, effort, operational difficulty) is grossly disproportionate to the safety benefit.
• You cannot declare ALARP while obvious, cheap, effective controls remain unused.

ALARP is not:

• “Zero risk” (almost never achievable)
• “As Low As Easily Convenient”
• A rubber stamp for continuing a high-risk practice because production pressure is high
• Proven merely by issuing PPE

Good vs Weak ALARP Arguments

Documenting ALARP and Residual Risk

Documentation turns judgment into a defensible record. A Level 3 supervisor should ensure records show:

• Task description and location
• Hazards assessed and matrix scores (inherent/current and residual)
• Controls selected and who verifies them
• Why residual risk is considered tolerable / ALARP
• Escalation path if residual risk remains high
• Names, dates, and toolbox talk acknowledgment

If an inspector, auditor, or incident investigation asks “why was this allowed?”, your form should answer without relying on memory.

Escalation Rules

Company matrices usually define mandatory actions:

• Low: proceed with standard controls; monitor
• Medium: additional controls / supervisor approval
• High/Extreme: stop work, escalate to area authority / HSE, redesign task

Never “average away” an Extreme severity scenario by inventing an unrealistically low likelihood. If severity is Extreme and barriers are uncertain, treat it as escalate.

Linking Matrices Back to HEMP

• Assess uses the matrix.
• Control and Recover change the score.
• Reassessment after change of conditions (weather, SIMOPS, night shift) is part of dynamic risk assessment.

Exam Focus Points

Expect questions that mix numbers and judgment: given likelihood 4 and severity 5, what priority? Or: which statement correctly describes ALARP? Correct answers emphasize proportionate reduction, documentation, and not accepting high residual risk without escalation. Incorrect options often confuse ALARP with zero risk or with PPE-only solutions.

Practice translating live Nigerian jobs into matrix language: state likelihood, severity, colour, extra controls, residual risk, and whether you would allow the job to start. That fluency is what Level 3 supervision looks like under audit.