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Working in Excavations-Frequently Asked Questions

What precautions must be taken to protect employees during excavation work?

According to the Construction Regulations, precautions must be taken that are adequate to:

  • Guard against danger to persons at work from a fall or dislodgement of earth, rock or other material by suitable shoring or otherwise
  • Guard against dangers arising from the fall of materials or objects or the inrush of water into the excavation, shaft, earthworks, underground works or tunnel
  • Secure adequate ventilation at all workplaces so as to maintain an atmosphere fit for respiration and to limit any fumes, gases, vapours, dust or other impurities to levels which are not dangerous or injurious to health
  • Enable persons at work to reach safety in the event of fire or an inrush of water or materials
  • Avoid risk to persons at work arising from possible underground dangers such as underground cables or other distribution systems, the circulation of fluids or the presence of pockets of gas, by undertaking appropriate investigations to locate them before excavation begins
  • Ensure that a safe means of access to and egress from each excavation

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How deep must an excavation be before such precautions need to be taken?

The Construction Regulations require contractors to guard against the dangers from a fall or dislodgement of material in an excavation. The Safety, Health and Welfare at Work Act 2005 requires a risk assessment to be performed by contractors before undertaking excavation work. The risk assessment must:

• identify those hazards that are likely to be encountered;

• determine the control measures; and

• determine the safe system of work required to protect employees and persons affected by the activities taking place.

Control measures selected could be in the form of shoring (support for the excavation), battering (sloping the excavation) or other suitable means.

Note: The risk assessment may indicate the need to install trench supports (or other alternative protective measures) even in relatively shallow excavations less than 1.25 m deep, particularly if ground conditions are particularly poor or the nature of the work requires workers to lie or crouch in a trench.

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When does an excavation have to be inspected?

A competent person must inspect excavations:

  • At least once in every day during which persons are at work there
  • If more than 2 metres deep, at the start of each shift before work begins
  • After any event likely to have affected the strength or stability of the excavation or the shoring
  • After any accidental fall of rock, earth or other material
  • At least once every 7 days where persons are not at work there

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Do any inspection form(s) have to be filled in?

An AF3 form is filled out by the competent person who carries out the inspection.

What should be included in these inspections?
Aspects/parts of the excavation works that should be inspected, include, but are not limited to:

1. Surface Conditions

  • Cracks
  • Spoil heaps not set near or close to excavations
  • No equipment or materials stored near edge
  • No standing water in excavation

 

2. Banks and sides of slope/bench

  • Cracks
  • Change in soil type
  • Slope of side/bank

 

3. Access and egress 

  • Stairs, ladders, ramps as appropriate

 

4. Shoring and Shielding

  • In place properly, functioning correctly
  • Wedges tight

 

5. Existing utilities

  • Support adequate
  • Loose materials

 

6. PPE

  • Hi-visibility vests, hard hats, steel-toe shoes, etc. as specified

 

7. Weather

  • Rain
  • Overnight freezing

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What particulars should be inspected in relation to shoring?

A checklist of inspection items that should be considered when inspecting shoring.
 

  • Is the installation as per the design?
  • Is the soil and water as per design?
  • Is there ingress of water?
  • Are there proper sumps?
  • Is material being drawn from behind the sheets?
  • What are the deflections on frames and sheets?
  • What is soil composition, are there tension cracks?
  • Are the deflections excessive?
  • Is there damage to the system?
  • Is access to trench adequate?
  • Are there any surcharges?
  • Check for cracks in adjacent structures?
  • Is there surface clear of plant, spoil, etc?
  • Are spoil heaps properly controlled?
  • Is the area properly fenced?
  • Is the edge protection/handrail to the trench adequate?
  • Are there exhaust gases in the trench?
  • Are buried services marked?
  • Are wedges tight?
  • Are the struts horizontal?
  • Have struts hanging chains?
  • Are the personnel competent?
  • Is the work as per method statement?
  • Is the safe system of work working?

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I have heard the HSA have a publication that simplifies what has to be done when carrying out groundwork and excavation work. What is this?

The HSA, in consultation with the construction industry, have formulated a practical system to assist employers and employees comply with their statutory requirements regarding a number of construction and construction related activities.

This is called the Safe System of Work Plan (SSWP). The SSWP links the implementation of the safety statement directly to the work activity. One SSWP is completed at the start of each activity, and can be reviewed at any time during the work. It increases the users to consider a range of options to deal with the risks. The SSWP uses pictograms in large part which will be of assistance in overcoming language barriers as currently being experienced on Irish sites. It is also is user friendly requiring a tick rather than long written paragraphs.

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What hazards are associated with excavation work?

The main hazards associated with excavation work include:

  • Surface encumbrances
  • Excavation collapse
  • Loose rock or soil
  • Contact with underground services and/or overhead power lines
  • Falling loads - Materials falling onto people working in the excavation
  • Mobile equipment - People and vehicles falling into the excavation
  • Vehicular traffic - People being struck by plant
  • Undermining of nearby structures
  • Access/egress to/from excavation
  • Hazardous atmospheres
  • Ground water
  • Accidents to members of the public

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What precautions can be taken to avoid contact with underground services and/or overhead lines?

If underground cables or overhead lines cannot be diverted, then the following steps should be taken to avoid contact:

  • Contact the appropriate service providers (ESB, Bord Gáis, etc.) and ask their advice.
  • Look around for obvious signs of underground services, e.g. valve covers or patching of the road surface.
  • Use locator's to trace any services and mark the ground accordingly. Make sure persons using these scanners are trained and understand their use.
  • Make sure that the person supervising excavation work has service plans and knows how to use them.
  • Everyone carrying out the work should know about safe digging practices and emergency procedures.
  • Survey the area for overhead obstructions such as electricity lines.
  • Erect goal posts and bunting if/as required
  • Where work needs to be carried out in close proximity to overhead lines, contact the ESB for advice.
  • For further information on working near underground services, see the HSA Code of Practice 'Avoiding Danger from Underground Services', available from the HSA Publications section of this website or contact 1890 289 389.

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What measures should be taken to prevent excavation collapse?

Measures that should be taken to avoid excavation collapse include:

  • Batter the sides and the ends to a safe angle.
  • Where it is not possible to batter, support the walls with timber, sheeting or proprietary support systems.
  • Do not go into unsupported excavations that have not been battered to a suitable slope.
  • Do not allow any vehicle or item of plant near an edge of an excavation that may be likely to cause collapse.
  • Keep equipment and materials piled, grouped or stacked at a suitable safe distance from the edge of the excavations.
  • Never work ahead of the support.
  • Remember that even work in shallow trenches can be dangerous. You may need to provide support if the work involves bending or kneeling in the trench.
  • Ensure adequate protective measures are taken even in rock cut excavations.

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What measures should be taken to prevent materials falling onto workers in excavations?

  • Do not store spoil or other materials close to the sides of excavations. The spoil may fall into the excavation and the extra loading will make the sides more prone to collapse
  • Make sure the edges of the excavation are protected against falling materials. Provide toe boards where necessary
  • Always wear a hard hat when working in excavations
  • In rock cut excavations where the rock is friable, netting should be used

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What measures should be taken to prevent people and vehicles falling into the excavation?

  • Fence off all excavations in public places to prevent pedestrians and vehicles falling into them.
  • Where children might get onto a site out of hours precautions should be taken such as backfilling or securely covering excavations.
  • If possible excavations in public roads or streets should be backfilled or covered over at night to minimise the risk of accidents to the public.
  • Do not leave materials lying beside the area of work if not required for imminent use beside the excavation.

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What if an excavation is likely to reduce the stability of a nearby structure?

Control measures that should be taken include:

  • Ensure excavations do not affect the footings of scaffolds or the foundations of nearby structures. Walls may have very shallow foundations that can be undermined by even small trenches
  • Decide if it is necessary to remove a structure in close proximity to excavation.
  • Decide if the structure needs temporary support before digging starts. Surveys of the foundations and the advice of a structural engineer may be needed
  • If shoring support is required, it should be installed in such a way that the stability of the structure is not compromised at any stage of the installation/excavation process
  • The services of a registered professional engineer may be required to determine that excavation work will not pose a hazard to employees

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Do all excavations have to be fenced off?

Regulation 55 of the Construction Regulations requires every accessible part of an excavation near to which persons are working and where persons could fall are either fenced or securely covered unless fencing is not present to allow access of persons/equipment.

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How can I ensure there is safe access to and egress from an excavation?

  • Quick unobstructed and ready access and egress should be allowed in case of emergencies. The size of the openings should be adequate and free from obstruction to allow ready passage for persons wearing the necessary PPE and allow access to rescue personnel. An alternative opening should be used for insertion of hoses, ventilation ducts, power lines and other cables required for work.
  • An appropriate means such as a barrier or a safety warning sign should be used to prevent unauthorised entry into a confined space.
  • Structural modifications (temporary openings) are necessary in the case of a confined space with a design deficiency whose openings are too tight, of convoluted construction or have excessive distances to the point of escape.
  • Manufacturers and suppliers of equipment as well as designers engineers and architects should ensure that entry and exit can be achieved from this equipment easily. For example the provision of manholes close to the bottom of the tank/vessel and fixed ladders from top manholes should be provided to facilitate emergency egress where the need for persons to enter a confined space is unavoidable. Manufacturers and designers should also be aware of any standards relevant to what they are constructing as there may be minimum sizes set out for hatches or manholes.

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What measures should be in place to avoid exposure to hazardous atmospheres?

Excavations can have very poor natural ventilation so that the potential for a dangerous atmosphere can give rise to typical 'confined space' conditions of immediate danger to life and health. Dangerous atmospheres can occur in excavations due to lack of oxygen or the presence of toxic or flammable gases of simple asphyxiants.  The leakage or seepage of a toxic gas into an excavation must be avoided by ventilation. 

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Before beginning work in an excavation what should you do?

  • Investigate if a dangerous atmosphere is present or liable to be present?
  • See is the space adequately ventilated to maintain adequate oxygen content and prevent the accumulation of harmful substances?
  • Find out what the use and history of the location of work is when carrying out risk assessment. Buried underground pipe work or a leakage in sewage system may present a hidden hazard.
  • Investigate if a dangerous atmosphere is potentially present; the excavation must be treated as a confined space.
  • A safe system of work must be developed and put in place, including the making of appropriate emergency arrangements. The safe system of work may involve the provision of adequate ventilation, testing of atmosphere, or other precautions, as devised by a competent person.

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What measures should be in place to avoid accumulation of water in the excavation?

There should be a safe system of work in place to prevent this from happening.  Employers should have addressed this hazard in their risk assessment and adequate control measures should be in place.  A plan for evacuation of personnel and equipment in case of emergency and flooding shall be developed.

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What Publications are available?

The Following publications are available on our website;