Risk Assessments · Mandatory · Pre-Construction
RAMS — Groundworks and Excavation
This RAMS covers excavation works including trenching, piling, and foundation preparation, addressing collapse risk, underground services, water ingress, and access/egress. It requires utility surveys (CAT and Genny scans), shoring or battering arrangements, and edge protection. All excavations must be inspected before each shift.
Last reviewed: 29 March 2026 — This guide reflects UK law as of this date. MHSWR 1999 remains current with no amendments enacted as of 29 March 2026. Next scheduled review: 29 March 2027.
| Legal basis | MHSWR 1999 Regulation 3 + CDM 2015 Regulation 22 (excavations) + HSG47 (Avoiding danger from underground services) |
| CDM 2015 Reg 22 | Prevent collapse, competent person inspection at the start of each shift, records required |
| Who | Groundworks contractor |
| Permit to dig | Separate permit required before any excavation work begins |
| Underground services | HSG47 protocol — CAT/Genny survey, service drawings, trial holes |
| Enforcing authority | Health and Safety Executive (HSE) |
1. What It Covers
Groundworks and excavation is the highest-risk category of construction activity. A RAMS for this work scope must address every phase of ground disturbance — from initial topsoil strip through to final reinstatement. The hazards are severe, the margin for error is narrow, and the legal requirements are specific.
The RAMS should cover the full range of excavation activities likely to be encountered on a typical groundworks package: topsoil strip, bulk excavation, trench excavation, foundation excavation, and reinstatement. Each of these activities presents distinct hazards and requires specific control measures. A single generic statement is not sufficient — the RAMS must address each activity individually and set out the sequence, plant, support methods, and inspection regime that will be used.
Trench collapse: a cubic metre of soil weighs over 1.5 tonnes
No ground can be assumed to be stable without a proper assessment. There is no depth threshold below which excavation is considered safe — collapses have occurred in trenches less than one metre deep. Every excavation, regardless of depth, must be assessed for the risk of collapse and appropriate support or battering provided.
2. Legal Framework
Groundworks and excavation RAMS sit within two overlapping legal frameworks. The first is the general duty under the Management of Health and Safety at Work Regulations 1999, Regulation 3, which requires a suitable and sufficient risk assessment for all work activities. The second is the specific duty under CDM 2015, Regulation 22, which imposes detailed requirements on excavation work that go well beyond a standard risk assessment.
“All practicable steps must be taken, where necessary to prevent danger to any person, including, where necessary, the provision of supports or battering, to ensure that — (a) no excavation or part of an excavation collapses; (b) no material forming the walls or roof of, or adjacent to, an excavation is dislodged or falls; and (c) no person is buried or trapped in an excavation by material which is dislodged or falls.”— CDM 2015 Regulation 22
What CDM 2015 Reg 22 specifically requires
- • Prevent collapse of excavation walls, roofs, and adjacent ground
- • Prevent falls into excavations
- • Prevent overloading of excavation edges by plant, materials, or spoil
- • Competent person inspection at the start of each shift before work begins
- • Records of inspections kept and available for review
3. Key Hazards
The following table sets out the principal hazards associated with groundworks and excavation, who is at risk, the key risk factors, and the control measures that should be addressed in the RAMS.
| Hazard | Who at risk | Risk factors | Control measures |
|---|---|---|---|
| Trench collapse | Operatives in or adjacent to trench | Soil type, water table, depth, surcharge loading, vibration from plant | Trench support (box, sheet piling, props) or battering to safe angle; competent person inspection each shift; exclusion zones |
| Striking underground services | Excavator operator, banksman, nearby operatives | Presence of gas, electric, water, telecoms; accuracy of service records; depth of cover | HSG47 protocol: service drawings, CAT/Genny survey, trial holes by hand, permit to dig, safe digging practice |
| Falls into excavation | All site operatives, visitors, members of the public | Open excavations, inadequate barriers, poor lighting, proximity of pedestrian routes | Edge protection (guard rails, barriers); signage; lighting for night works; covering openings; segregation of pedestrian routes |
| Plant and vehicle movements | Banksmen, operatives on foot, adjacent trades | Blind spots on 360 excavators, reversing dumpers, congested site, unmarked routes | Traffic management plan; banksman; reversing aids; segregation of pedestrian and vehicle routes; speed limits; designated turning areas |
| Flooding / water ingress | Operatives in excavation | High water table, rainfall, burst services, tidal influence | Dewatering (pumps); monitoring water levels; rescue plan; prohibition of entry during flooding; competent person assessment |
| Manual handling | All operatives | Trench props, formwork, kerbs, pipes, heavy materials in confined trench | Mechanical handling where practicable; manual handling assessment; two-person lifts; task rotation; training |
| Silica dust / contaminated ground | Excavator operator, operatives in excavation | Cutting concrete, sandstone, or brick; brownfield sites with contamination history | Dust suppression (water); RPE where required; ground contamination survey; COSHH assessment; health surveillance where indicated |
| Overhead lines | Excavator operator, dumper operator, crane operator | Proximity to overhead power lines; boom reach of plant | Goal posts / height restrictors; safe clearance distances (GS6); plant selection to avoid working within exclusion zone; DNO consultation |
4. Underground Services — HSG47 Protocol
Striking an underground service — particularly gas or electricity — can cause fatal injuries, explosions, and fires. HSG47 (Avoiding danger from underground services) sets out the protocol that must be followed before any excavation begins. The RAMS must reference this protocol and confirm that each step will be completed in sequence.
| Step | Action | When |
|---|---|---|
| 1 | Obtain service drawings from all utility providers (gas, electric, water, telecoms, drainage) | Before any excavation is planned — at the earliest stage of the project |
| 2 | CAT and Genny survey of the excavation area to locate live services | On site, before excavation begins — by a trained operative (CSES certified) |
| 3 | Trial holes by hand to confirm the position and depth of services identified by the survey | After CAT/Genny survey, before machine excavation in the vicinity of identified services |
| 4 | Mark out services on the ground surface using paint, pegs, or markers | After trial holes confirm service positions — markings maintained throughout the works |
| 5 | Maintain safe distances — minimum 500mm hand-dig zone either side of any identified service | During all excavation work in the vicinity of services |
| 6 | Emergency procedure if a service is struck — including isolation, evacuation, and notification of the utility provider | Documented in the RAMS and briefed to all operatives before work begins |
CAT surveys locate live services only — not dead or isolated cables
A CAT (Cable Avoidance Tool) detects electromagnetic signals from live cables and metallic pipes. It will not detect services that are de-energised, isolated, or non-metallic (such as plastic water or gas pipes without a tracer wire). Service drawings must always be consulted alongside the CAT survey, and trial holes used to confirm the position of any service that may not be detectable by the instrument alone.
5. Trench Support Methods
The method of trench support must be selected based on ground conditions, trench depth, available space, and the duration of the excavation. The RAMS must specify which method will be used and confirm that it has been selected by a competent person with knowledge of the ground conditions on site.
| Method | Description | Typical use | Key requirements |
|---|---|---|---|
| Battering / sloping | Excavation sides cut back to a safe angle to prevent collapse | Bulk excavation, shallow trenches, open sites with space for battered slopes | Angle determined by competent person based on soil type; typically 45 degrees or flatter in granular soils; steeper angles may be acceptable in stiff clay but must be assessed |
| Trench box / shield | Pre-fabricated steel or aluminium box placed in the trench to protect operatives | Pipe-laying trenches, service trenches, repetitive linear excavations | Box must be rated for the trench depth; installed before operatives enter; must extend above ground level; operatives must not work outside the box |
| Sheet piling | Interlocking steel sheets driven into the ground to retain the trench walls | Deep excavations, high water table, adjacent to structures or highways, long-duration excavations | Design by a competent engineer; installation by specialist piling contractor; monitoring for movement during the works |
| Hydraulic / screw props | Adjustable struts placed between trench walls to prevent inward movement | Short-duration trench work, inspection chambers, localised excavations | Props must be correctly sized for trench width and depth; installed from the top down before operatives enter; removed from the bottom up during backfill |
The 1.2m rule is an urban myth — it does not exist in current legislation
There is a widespread belief in the industry that excavations under 1.2 metres deep do not require support. This is incorrect. There is no depth threshold in CDM 2015, the Workplace (Health, Safety and Welfare) Regulations, or any other current legislation below which trench support is not required. The duty under Regulation 22 is to prevent collapse — regardless of depth. Collapses in trenches less than one metre deep have resulted in fatalities. Every excavation must be assessed on its own merits by a competent person.
6. Competence Requirements
Groundworks and excavation requires specific plant and task competence for every role on the team. The RAMS must confirm that all operatives hold the required qualifications and that evidence has been verified before work begins.
| Role | Required competence |
|---|---|
| 360-degree excavator operator | CPCS (Construction Plant Competence Scheme) trained operator card or competent operator card for the relevant category (A59 or equivalent) |
| Dumper operator | CPCS trained or competent operator card for forward tipping dumper (A09) or articulated dump truck (A56) as applicable |
| Telehandler operator | CPCS trained or competent operator card for telescopic handler (A17) |
| Roller operator | CPCS or NPORS (National Plant Operators Registration Scheme) card for the relevant roller category |
| Competent person (excavation inspection) | Sufficient training, experience, and knowledge of ground conditions to carry out inspections under CDM 2015 Regulation 22; typically a site manager or engineer with specific excavation experience |
| CAT/Genny operative | CSES (Cable and Service Enquiry System) certified; trained in the use of CAT and Genny equipment and interpretation of service drawings |
| All operatives | CSCS (Construction Skills Certification Scheme) card valid for their occupation; site-specific induction completed; toolbox talk on excavation hazards |
7. Common Mistakes
No CAT survey before excavation
Excavation must not begin until a CAT/Genny survey has been completed by a trained operative and the results reviewed against service drawings. Relying on drawings alone is not sufficient — drawings may be inaccurate or incomplete. Equally, relying on CAT alone is not sufficient because it only detects live services. Both must be used together as part of the HSG47 protocol.
Treating ground as stable without assessment
No ground should be assumed to be stable. Ground conditions can change within metres due to variations in soil type, water content, and previous disturbance. A competent person must assess the ground before excavation begins and determine the appropriate support method. Visual inspection alone is not an adequate assessment.
No permit to dig in place
A permit to dig is a separate document to the RAMS. It confirms that the HSG47 protocol has been followed, that services have been identified and marked, and that the excavation has been authorised. Excavation without a permit to dig is a significant compliance failure and a common enforcement target for the HSE.
Spoil heap too close to the excavation edge
Spoil must be stored a minimum of 600mm from the edge of any excavation. Spoil placed closer than this surcharges the ground and significantly increases the risk of collapse. In practice, a greater distance is often required depending on the depth of the excavation and the type of ground. The RAMS must specify the minimum distance and the competent person must verify compliance during inspections.
Competent person inspection not recorded
CDM 2015 Regulation 22 requires that excavations are inspected by a competent person at the start of each shift before work begins. The inspection must be recorded. An unrecorded inspection provides no evidence of compliance. Inspection records should note the date, time, excavation reference, findings, and any actions required — and be signed by the competent person.
8. Frequently Asked Questions
Does CDM 2015 Regulation 22 apply to shallow excavations?▾
Yes. Regulation 22 applies to all excavations regardless of depth. There is no minimum depth threshold in the legislation. A trench 600mm deep in unstable ground can collapse and bury an operative just as effectively as a deeper excavation. The competent person must assess every excavation and determine the appropriate control measures based on the actual ground conditions, not on an arbitrary depth figure.
What records are required for competent person inspections?▾
The inspection record should include the date and time of the inspection, the identity of the excavation inspected, the name and signature of the competent person, the findings of the inspection (including the condition of any support systems), and any actions required before work can proceed. Records must be kept on site and available for review by the HSE or the principal contractor.
Can one RAMS cover the whole groundworks package for an entire project?▾
In principle, yes — provided the RAMS is sufficiently detailed to address every activity, hazard, and control measure for the full scope of groundworks. In practice, a single RAMS that tries to cover topsoil strip, bulk excavation, trench work, foundation excavation, and reinstatement across multiple phases often becomes too generic to be useful. It is usually more effective to produce separate RAMS for each distinct activity or phase, cross-referenced to the overarching construction phase plan.
Who is the competent person for excavation inspections?▾
CDM 2015 does not prescribe a specific qualification for the competent person. The requirement is that they have sufficient training, experience, and knowledge to identify the hazards associated with the excavation and to determine whether the control measures in place are adequate. In practice, this is typically a site manager, site engineer, or groundworks supervisor with specific experience of excavation work and ground conditions. The competent person must be named in the RAMS and their competence documented.
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