How to Write a Risk Assessment for Excavation Work

Why excavation risk assessments catch people out

Excavation work sits near the top of the list for fatal accidents on construction sites. The hazards are well known — ground collapse, buried services, flooding, plant movements — yet risk assessments for excavation jobs are often rushed, vague, or copied from a previous project without being updated for the actual ground conditions, depth, or proximity to traffic.

If you're writing a risk assessment for excavation work from scratch, or trying to improve a template you've used before, this guide walks you through what needs to be in it, why each section matters, and how to make sure it holds up on site and in an inspection.

What the law requires

Under the Construction (Design and Management) Regulations 2015 (CDM 2015), all construction work must be planned and managed so that risks are identified and controlled. For excavation work specifically, Regulation 31 of the Construction (Health, Safety and Welfare) Regulations (now consolidated into CDM) requires that excavations are inspected by a competent person at the start of every shift, after any event likely to affect stability, and after accidental falls of material.

Your risk assessment doesn't need to be a 20-page document, but it does need to be specific to the job, signed off by someone competent, and available on site. A generic template with no site-specific detail will not satisfy an HSE inspector — or protect your workforce.

The key hazards to cover

Every excavation risk assessment should address the following hazard categories. Don't just list them — describe how they apply to your specific job and what controls you're putting in place.

1. Ground collapse and instability

This is the primary risk. Unsupported trench walls can collapse with no warning, and the weight of soil can be fatal within seconds. Your assessment needs to specify:

• The maximum depth at which work will be carried out
• Whether the sides will be battered (sloped back), shored (timber or hydraulic props), or supported with trench boxes or drag shields
• Ground type — made ground, clay, sandy soil, and gravel all behave very differently under load
• The procedure for inspecting the excavation before each shift and after rain or vibration

Any excavation deeper than 1.2 metres should be treated as requiring formal support unless a competent person has assessed the ground and confirmed it's safe to batter back. Even then, that decision should be documented.

2. Buried services and utilities

Striking a gas main, electrical cable, or water pipe is a consistent cause of serious injuries on site. Before any excavation begins, the assessment must confirm:

• Service drawings have been obtained and reviewed
• A CAT (cable avoidance tool) and Genny scan has been carried out
• All identified service routes are marked on the ground
• Hand digging only within 500 mm of any marked service
• Who to call if a service is struck or suspected — including the relevant utility emergency numbers

3. Flooding and water ingress

Excavations can flood quickly, especially in poor weather or near water tables, rivers, or drainage runs. Your risk assessment should address:

• Current water table depth (check with a ground investigation report if available)
• Whether a pump and standby pump are on site
• The procedure for evacuating an excavation if water rises unexpectedly
• Weather monitoring responsibilities — who checks forecasts and when

4. Plant and vehicle movements

Excavators, dumpers, and delivery lorries need to operate close to open excavations, which creates risks of edge collapse and workers being struck. Cover:

• Exclusion zones around the excavation edge (typically 2 metres minimum for vehicular traffic)
• Use of stop blocks or baulks of timber to prevent plant overrunning the edge
• Banksman requirements for reversing plant near excavations
• Segregation of pedestrian and vehicle routes

5. Falling into the excavation

Workers, members of the public, and plant operators can all fall into an open excavation. Controls should include:

• Physical barriers — Heras fencing, handrails, or trench covers — wherever the excavation is left unattended
• Safe means of access and egress (ladder, steps, or ramp) at regular intervals
• Clear signing at all access points

6. Hazardous atmospheres

In deep or confined excavations, especially near contaminated land, landfill, or sewers, there's a risk of oxygen depletion or build-up of toxic gases such as hydrogen sulphide or carbon monoxide. If this is a possibility on your site:

• Specify atmospheric testing before entry and during work
• Identify the equipment needed (multi-gas detector)
• Reference your confined space procedure if the excavation meets that definition

Structure your risk assessment clearly

A workable risk assessment for excavation work should follow a logical structure:

1. Task description — what's being excavated, where, how deep, what plant and how many workers
2. Hazard identification — the list above, described in terms of your actual site
3. People at risk — groundworkers, engineers, plant operators, members of the public
4. Initial risk rating — likelihood × severity before controls are applied
5. Control measures — the specific actions, equipment, and procedures that will be used
6. Residual risk rating — the risk level after controls are in place
7. Responsibilities — who is responsible for implementing each control
8. Review trigger — what would cause this risk assessment to be reviewed (change in depth, ground conditions, weather, unexpected finds)

Common mistakes that weaken excavation risk assessments

• Using a template from a different project without updating ground conditions, depth, or proximity to services
• Listing "trained operative" as a control without specifying what training is required
• No mention of inspection frequency or who carries out the inspection
• Ignoring the risk to the public where excavations are near footpaths or roads
• Failing to reference the method statement or permit to work that sits alongside the risk assessment

How to produce one faster without cutting corners

The problem most site supervisors and engineers face isn't knowing what should be in an excavation risk assessment — it's finding the time to write it properly in the middle of everything else going on.

One approach that's gaining traction is using AI tools to produce a first draft based on a description of the work or a few site photos. SiteSafePro lets you type a brief description of the excavation task — depth, location, plant involved, ground type — or upload photos of the area, and it generates a structured risk assessment in seconds. You still review it and add site-specific detail, but you're editing rather than writing from scratch, which saves significant time.

Whether you use a tool like that or a paper-based approach, the principle is the same: start with the actual hazards, work through the controls methodically, and make sure it's signed off before work begins.

Before work starts — a quick checklist

• Risk assessment written, reviewed, and signed
• CAT scan completed and services marked
• Shoring or battering plan agreed with a competent person
• Inspection regime confirmed and logged
• Access and egress in place
• Barriers and signage erected
• Emergency procedures briefed to all workers
• Atmospheric testing equipment on site if required

Excavation work is one of the highest-risk activities on any construction site. A risk assessment that's specific, practical, and actually read by the people doing the work is one of the best defences you have against serious injury — and against enforcement action if something does go wrong.