2.1 Principles of Risk Assessment & Five Steps to Risk Assessment

Principles of Risk Assessment & Five Steps to Risk Assessment

Risk assessment is the cornerstone of health and safety management on any construction site. In the UK, it is not merely good practice; it is a strict statutory requirement. Under Regulation 3 of the Management of Health and Safety at Work Regulations 1999 (MHSWR), every employer and self-employed person must make a "suitable and sufficient" assessment of the risks to the health and safety of their employees and any others who may be affected by their undertaking.

For site managers, understanding the core principles of risk assessment—and being able to implement them effectively at the workface—is critical to preventing accidents, ensuring legal compliance, and protecting workers under the Construction (Design and Management) Regulations 2015 (CDM 2015).

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Statutory Framework and Legal Duties

The statutory requirement to assess risk stems from the Health and Safety at Work etc. Act 1974 (HASAWA) and is codified in detail by MHSWR 1999:

• Employer Duty (MHSWR Reg 3): Employers must assess risks to employees and non-employees (such as subcontractors, site visitors, and the public) affected by construction activities.
• The 5-Employee Writing Threshold: Under MHSWR Regulation 3(6), if an employer employs 5 or more employees, they are legally mandated to record the significant findings of the risk assessment in writing, as well as any group of employees identified as being especially at risk.
• Construction Best Practice: On UK construction sites, best practice dictates that all risk assessments must be recorded in writing regardless of employee count, as Principal Contractors require documented evidence within the project's Construction Phase Plan (CPP).
• Self-Employed Duty: Self-employed contractors have a parallel duty to assess risks arising out of or in connection with their work.

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Hazard vs. Risk: Defining the Core Concepts

A fundamental requirement for SMSTS candidates is maintaining a clear distinction between a hazard and a risk.

The Principle of ALARP (As Low As Reasonably Practicable)

UK law does not expect employers to eliminate all site risks entirely if doing so is physically impossible or grossly disproportionate. However, employers must reduce risks to As Low As Reasonably Practicable (ALARP).

• The Legal Test: Established in the landmark case Edwards v. National Coal Board (1949), ALARP requires a quantitative or qualitative comparison between the degree of risk and the sacrifice (in time, money, and effort) required to reduce or eliminate that risk.
• Gross Disproportion: A risk control measure is legally required unless the defendant can prove that the sacrifice involved in implementing the measure is grossly disproportionate to the safety benefit gained.
• Standard Controls First: Standard industry guidance (such as HSE Approved Codes of Practice) sets the baseline for what is reasonably practicable. Claiming a measure is too costly when it is standard industry practice will fail in court.

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The HSE Five-Step Risk Assessment Process

The Health and Safety Executive (HSE) establishes a structured five-step methodology for executing risk assessments (INDG163):

Step 1: Identify Hazards
  └── Step 2: Decide Who Might Be Harmed & How
        └── Step 3: Evaluate Risks & Decide on Precautions
              └── Step 4: Record Findings & Implement Them
                    └── Step 5: Review Assessment & Update

Step 1: Identify the Hazards

Site managers must systematically identify hazards across all planned construction operations. Methods include:

• Site Walkthrough Inspections: Physically observing work areas, access routes, and storage zones.
• Reviewing Pre-Construction Information (PCI): Examining client PCI for hidden hazards like buried utilities, asbestos, or contaminated ground.
• Analyzing Trade Processes: Inspecting equipment, plant operations, hazardous substances (COSHH), and structural stability.
• Examining Historical Data: Reviewing accident books, RIDDOR reports, near-miss logs, and manufacturer Safety Data Sheets (SDS).

Step 2: Decide Who Might Be Harmed and How

Identify specific groups of people and how they might be exposed to harm:

• Direct Site Workforce: General operatives, machine operators, tradespeople.
• Specialist Subcontractors & Trade Interfaces: Electricians working adjacent to bricklayers.
• Vulnerable Groups: Young workers/apprentices (lack of experience), expectant mothers, trainees, or workers with language/literacy barriers.
• Transient Persons: Site visitors, delivery drivers, client representatives, and local statutory inspectors.
• Members of the Public: Nearby residents, pedestrians, school children walking past site boundaries.

Step 3: Evaluate the Risks and Decide on Precautions

Evaluate residual risk after considering existing controls, then apply the General Principles of Prevention (MHSWR Schedule 1). Site managers must ask:

1. Can I eliminate the hazard altogether?
2. If not, how can I control the risks so that harm is unlikely?

Step 4: Record Your Findings and Implement Them

Document the significant findings in a clear, accessible format. A suitable and sufficient risk assessment record must show that:

• A proper site check was conducted.
• You asked who might be harmed.
• You dealt with all the obvious significant hazards.
• The precautions implemented are reasonable and residual risk is ALARP.
• The workforce was involved and informed of the findings.

Step 5: Review Your Assessment and Update If Necessary

Risk assessments are living documents. They must be formally reviewed immediately when:

• There are significant changes to site conditions, scope of works, or construction methods.
• New plant, machinery, or hazardous substances are introduced.
• An accident, near-miss, or dangerous occurrence indicates that existing controls are inadequate.
• Statutory periodic review intervals elapse (typically annually or at major project phases).

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Dynamic Risk Assessment (DRA) on Live Sites

While written risk assessments plan for predictable operations, construction environments change rapidly. Dynamic Risk Assessment (DRA) is the continuous assessment of risk in a live, real-time environment.

• When Applied: Unforeseen weather shifts (e.g., high winds stopping crane lifts), unexpected ground conditions during excavation, or sudden structural instability.
• Operational Role: Site supervisors must observe the changing situation, evaluate the immediate hazard, determine if existing written RAMS cover the change, and pause work immediately if controls are inadequate until safe modifications are implemented.

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Specific Statutory Risk Assessment Requirements

In addition to general MHSWR assessments, UK legislation mandates specific statutory risk assessments for specialized hazards:

• COSHH Regulations 2002 (Reg 6): Assessment of hazardous chemical, biological, and dust exposures.
• Work at Height Regulations 2005 (Reg 3): Assessment of fall risks, fragile surfaces, and falling objects.
• Control of Noise at Work Regulations 2005 (Reg 6): Assessment of daily personal noise exposure levels.
• Control of Vibration at Work Regulations 2005 (Reg 5): Assessment of Hand-Arm Vibration (HAVS) and Whole-Body Vibration (WBV).
• Manual Handling Operations Regulations 1992 (Reg 4): Ergonomic assessment of lifting, lowering, pushing, and pulling tasks.