How to Write a RAMS for Excavation and Trenching: UK Guide

Why Excavation Work is High Risk

Excavation and trenching work is one of the most dangerous activities on any construction site. Trench collapse can happen without warning, and when it does, there is almost no time to react. A single cubic metre of soil weighs between 1.5 and 2 tonnes. Workers caught in a collapse face crush injuries, asphyxiation, or death within minutes.

Several factors increase the likelihood of collapse:

• Wet or waterlogged ground reduces soil cohesion

• Vibration from nearby plant, traffic, or piling work destabilises trench walls
• Surcharge loads (spoil heaps, materials, or vehicles stored too close to the edge)
• Previously disturbed or backfilled ground that has not consolidated
• Granular soils (sand, gravel) that have no natural cohesion

Even shallow trenches kill. The HSE has investigated fatal collapses in trenches less than 1.5m deep. Depth alone is not a reliable indicator of risk. Ground conditions, weather, and nearby activity all matter.

Legal Requirements

Excavation work on construction projects falls under the Construction (Design and Management) Regulations 2015 (CDM 2015). Schedule 3 of CDM specifically addresses excavations and requires that:

• Suitable and sufficient steps are taken to prevent danger from collapse, falling materials, or people falling into excavations
• Excavations are inspected by a competent person before any person carries out work at the start of every shift
• Inspections are also carried out after any event likely to have affected the strength or stability of the excavation (heavy rain, ground movement, accidental disturbance, nearby blasting)
• Results of inspections are recorded in writing and kept available on site

Beyond CDM, the Management of Health and Safety at Work Regulations 1999 require a suitable and sufficient risk assessment for all work activities. For excavation work, this means a RAMS that specifically addresses the ground conditions, support systems, access arrangements, and emergency procedures for that particular site and task.

Service Avoidance

Before any mechanical excavation begins, you must establish what is in the ground. Striking an underground service can cause explosions (gas), electrocution (power cables), flooding (water mains), or loss of critical infrastructure (fibre optic and telecoms).

Your RAMS must include a service avoidance procedure. The minimum standard is:

1. Obtain utility plans from all asset owners before work starts. Use a utility search provider to get up-to-date records for gas, electric, water, telecoms, and drainage.
2. Scan the ground with a CAT (Cable Avoidance Tool) and Genny (Signal Generator) across the full excavation area. The operator must be trained and competent in the use of the equipment. Scan in multiple directions.
3. Hand dig within 500mm of any known or suspected service. No mechanical excavation is permitted within this zone. Use insulated hand tools, not picks or forks.
4. Mark the location of identified services with paint or marker stakes before excavation begins.

HSE guidance document HSG47 (Avoiding danger from underground services) is the primary reference. Your RAMS should cite it and your operatives should be familiar with its requirements.

The golden rule: assume every trench has services until proven otherwise.

Key Hazards to Address in Your RAMS

Your excavation RAMS should address all of the following hazards as a minimum:

• Collapse and burial of trench walls onto workers in the excavation
• Striking underground services including gas mains, live electrical cables, water mains, and fibre optic lines
• Falls into the excavation by workers, members of the public, or vehicles
• Flooding and water ingress from groundwater, burst services, or surface water runoff
• Undermining adjacent structures including building foundations, retaining walls, boundary walls, and roads
• Plant operating near edges causing surcharge loading or vibration that destabilises the excavation
• Confined space conditions in deep excavations where gas accumulation or oxygen depletion is possible
• Manual handling of trench support equipment, shoring timbers, and heavy materials

Control Measures

Shoring and Support Systems

Any trench where there is a risk of collapse must be supported. The type of support depends on the depth, ground conditions, and duration of the work:

• Timber shoring uses walings, struts, and poling boards to hold back trench sides. Suitable for shorter duration works in reasonably stable ground.
• Hydraulic shoring (drag boxes or frames) can be installed from the surface without anyone entering the unsupported trench. This is the preferred method for most utility trenching.
• Trench boxes (shield systems) provide a protected working area within the trench. Workers remain inside the box at all times. Boxes are rated to specific depths and soil types.

Shoring must be installed progressively as the trench deepens and must not be removed until all work in that section is complete. The design of temporary support must be carried out or verified by a competent person.

Benching and Battering

Where space allows, trench sides can be cut back (battered) to a safe angle rather than using mechanical support. The safe angle depends on the soil type:

• Granular soil (sand, gravel): maximum 1:1 slope (45 degrees) as a general guide, though loose granular soils may require flatter angles
• Cohesive soil (clay): steeper angles may be possible in the short term, but clay dries and cracks, so monitor constantly
• Mixed or made ground: treat as the weakest soil type present

Benching (cutting steps into the trench side) is an alternative approach for wider excavations. Both methods require significantly more space than shoring and may not be practical in confined urban sites.

Edge Protection

Preventing people and vehicles from falling into the excavation is just as critical as preventing collapse:

• Install physical barriers (guardrails, fencing, or proprietary trench edge protection) set back at least 1m from the edge of the excavation
• Use stop blocks or bunds to prevent plant and vehicles from approaching the edge
• Provide adequate lighting for any excavation that remains open after dark
• Keep spoil heaps, materials, and equipment at least 1m from the trench edge to reduce surcharge loading

Access and Egress

Workers in trenches need a safe way in and out that does not require climbing the trench walls:

• Provide a ladder at intervals of no more than 15m along the trench length
• Ladders must extend at least 1m above the trench edge and be secured against displacement
• For wider excavations or longer duration works, consider ramped access or proprietary stairway systems

Inspections

CDM 2015 Schedule 3 requires inspections by a competent person:

• At the start of every shift before anyone enters the excavation
• After any event likely to have affected stability (heavy rain, frost, nearby vehicle movements, vibration from adjacent works)
• After any accidental fall of rock, earth, or material into the excavation

Inspection results must be recorded in writing. Include the condition of trench support, water levels, ground conditions, edge protection status, and any remedial actions required. Keep records on site and available for inspection by the HSE.

Dewatering

Water in excavations creates multiple problems. It reduces soil stability, makes surfaces slippery, and can hide trench features and services. Your RAMS should specify:

• Pumping arrangements (submersible pump with adequate capacity)
• Discharge location (not onto adjacent land or into watercourses without permission)
• Monitoring of water levels during the shift
• Procedure for stopping work if water ingress exceeds pumping capacity

When Does an Excavation Become a Confined Space?

Not every excavation is a confined space, but deep trenches and excavations can become one. The Confined Spaces Regulations 1997 apply when an enclosed or substantially enclosed space presents a reasonably foreseeable risk of serious injury from hazardous conditions.

In practice, an excavation is likely to be a confined space when:

• It is deeper than approximately 1.2m with restricted access and egress (narrow trench, limited ladder positions)
• There is a risk of gas accumulation, for example methane from contaminated or landfill ground, CO2 from decomposing organic material, or heavier-than-air gases settling at the bottom of the excavation
• There is a risk of oxygen depletion, for instance from displacement by other gases or from biological processes in waterlogged ground
• There is a risk of flooding that could trap workers

If the excavation meets confined space criteria, your RAMS must include continuous gas monitoring (4-gas detector as a minimum for O2, LEL, CO, H2S), a written rescue plan, trained rescue personnel on site, and appropriate rescue equipment. No one should enter until atmospheric testing confirms it is safe.

Generate Your Excavation RAMS

Writing a thorough excavation RAMS from scratch takes hours. SwiftRMS generates a comprehensive, regulation-compliant RAMS for excavation and trenching work in minutes. Describe the job, review the output, and have your team sign off digitally. Start your free trial and generate your first excavation RAMS today.

Related Guides

• Confined Space Risk Assessment: UK Guide
• Construction Phase Plan: Complete UK Guide
• CDM Regulations 2015: What You Need to Know
• What is a RAMS? Complete UK Guide