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Excavation Safety: What You Should Know

 

Reading time: 7 minutes

 

What are the rules for excavation in the UK?

In the UK, the law states that workers must be protected from hazards when working in or near trenches, and no worker is allowed to work in an unsupported trench deeper than 1.2m. There are also other safety considerations to consider, such as avoiding underground services, not undermining existing structures, providing daily inspections of the trench by a competent person and providing safe routes in and out. 

 

There are other trench safety rules to consider, including:

 

  • Planning and preparation should be done by a competent person

  • If possible, trenchless techniques should be considered in the design phase 

  • Safe digging practice must be used to avoid electricity cables, trees and other infrastructures (the OSHA safety standards offer useful advice on the correct safety procedure in excavation work)

  • Temporary support may be required to prevent collapse

  • Fall prevention must be used

  • The soil type should be inspected to consider drainage and slope

  • Ground conditions, underground structures and existing services must be provided by commercial clients to contractors

 

What are the safety measures for excavation?

Trench collapse and falls pose a serious safety risk to construction workers, and safety measures have to be put in place, by law, to prevent accidents. A competent person must inspect the trench plus excavation safety supports and battering before each shift, and no work should start before the excavation is safe. Heavy equipment must be kept away from the edges, and all workers must wear the correct PPE.

 

Other safety measures include:

 

  • A survey of the soil type should be done in the planning and preparation stage - this will determine the slope angle of the trench

  • Trenches must be supported if they are 1.2 m or deeper

  • Inspections must take place by a competent person at the start of each shift, after storms, flooding, or other changes which could affect stability

  • Battering of the sides should be used to create a safe angle

  • Tools, plant and equipment must be moved away from the trench edge

  • Excavated soil and stone must be moved at least 2 feet away from the edge

  • Underground utility locations should be mapped out before trenching starts

  • If a trench is 4 feet or deeper, tests should be carried out for atmospheric hazards (including toxic gas)

  • Work mustn’t take place under suspended or raised loads

  • Safe access in and out must be provided

  • Additional safety measures, such as benching, sloping, shoring and shielding should be planned in advance

  • Trench safety barriers must be installed to prevent people or materials falling in

  • As well as the site-required PPE, workers should also wear hi vis clothing

 

What are the hazards in excavation?

The main risks posed by construction digging work are excavation and trench safety hazards to workers, through trench collapse or falls. Just one cubic metre of soil can weigh over 1.5 tonnes, and collapse can happen quickly and without warning. Workers are also at risk of falling materials, flooding or groundwater causing instability, and the risk of accidental damage to nearby structures, pipes or cables.

 

Avoiding the risk of collapse

By removing excess soil, equipment and shoring or battering walls you can help to prevent collapse. Using trench sheets, props, baulks and other equipment can significantly improve the structure’s safety. Inspection by a competent person will also help to reduce the risk by identifying problems before they happen.

 

Preventing falls

Falling into the trench is a risk for both construction workers and the general public. Cordoning off the trench and using the correct safety signage and barriers is vital. Guardrails and toe boards should be used, as well as safe and secure access in and out. Ladders should be the appropriate length and placed on a firm base.

 

The risk from existing infrastructure

There is a risk of existing structures falling or being undermined. Extra support for the structure may be needed, and a foundation survey and/or advice from a structural engineer is recommended. Ideally, all existing cables and pipes should be mapped out, to avoid damage, with planning and safety measures in place to prevent accidents.

 

Other environmental risks

The watercourse level, soil type and weather can all affect trench stability. Water needs to be channelled and pumped out, or an alternative method used, especially when excavation takes place near to lakes or water sources. Tree roots can provide potential problems, and care must be taken not to damage nearby trees. Remember that inspection must take place after bouts of rain or other significant weather conditions.

 

How deep can excavation be without shoring?

The Construction (Working Places) Regulations of 1966 states that any trench of 1.2 metres in depth, or more, must be protected by a shoring system - such as shores or props - used for bracing the trench walls whilst excavation takes place. Trench shoring is sometimes called trench bracing or lining.

 

Do you need a licence or special training?

To follow the correct safety procedure in excavation work, all trenches must be supervised and inspected by a fully-trained competent person, and all staff should receive safety training. Trenches deeper than 20 feet need a protective safety system designed by a professional engineer. 

 

If you’re digging to a depth of 100mm or more, or on a public footpath or highway, you should have a Permit To Dig from your local authority. You’ll also usually need planning permission and building control sign off when digging foundations. For works involving excavation of the highway all contractors must be Street Works Accredited.

 

Excavation safety checklist

An in-depth excavation safety checklist must be carried out by a specialist competent person daily, before any work starts, and after any possible change to the trench conditions, as previously mentioned. An inspection record must be kept and signed, with any possible risks addressed immediately. The written report must contain crucial information, such as the person inspecting, any health and safety risks found, what action was taken and plans to prevent future problems.

 

Initial assessment

The excavation safety checklist will include the competent person’s details, the time and date of inspection, and an assessment of the soil and particulates plus any ground water present and planned drainage of the trench. The types of protective systems will be noted. Utilities and overhead lines and pipes are noted, with the relevant authorities contacted.

 

General assessment

The job site will be assessed for nearby structures, as well as whether employees are wearing PPE, warning systems in place and whether all employees have been briefed on safety procedures - such as standing away from loading/unloading vehicles, or not working on sloped areas above other employees. Required safety equipment, such as handrails, will be noted alongside the safe means of access.

 

Protective equipment you will need

An excavation safety checklist includes checking that workers are all wearing hard hats, class II high visibility reflective vests, protective boots, eye protection, work gloves, and other site-required PPE. Ear protection is often required, as well as respirators for certain site conditions. A full body harness is needed for bell bottom trenches or deep excavations. A protective system such as sloping, benching, trench shield or box, or shoring, will be required and must be noted. 

 

Hazardous atmosphere

If atmospheric testing is needed, this must be noted. Protection from exposures to atmospheres containing less than 19.5% oxygen must be logged and actioned. Ventilation will be checked, and testing will be performed regularly to ensure compliance. The assessor may require a penetrometer to assess the soil, as well as the means of testing vibrations on site. 

 

Safety measures and support systems

All materials must be inspected for possible defects, as well as the stability of nearby structures. Any materials, equipment and support systems being used will be noted and updated daily, or throughout the shift if any changes occur. Any repaired damaged materials must be inspected by a registered engineer before re-use.
 

For more information, inspiration and handy construction tips, visit the Travis Perkins Trade News and Advice hub

 

Excavation Safety: FAQs

What is the 5 4 3 2 1 rule excavation?

The 5 4 3 2 1 excavation rule states that for every 5m depth, the trench walls should slope 4m back. For every 4m depth, it should slope 3m back, and for a 3m depth it should slope 2m. For 2m deep, the trench should slope 1.5m to help protect the structure and reduce the risk of collapse. 

 

What is the 6 foot rule for excavation?

The 6 foot rule in trenching is that any excavation measuring 6 foot (or more) in depth must offer fall protection, to prevent workers or the public from falling in. It must be protected from cave-in, and offer guard rails, fences, barricades and other safety systems to help prevent serious accidents.

 

What are the 5 P's of safe excavation?

The five ps of safe excavation are: Plan, Prepare, Pothole, Protect and Proceed. Safety is paramount, and workers have the legal right to health and safety protection on site.

 

What is the maximum trench depth before shoring in the UK?

The Construction (Working Places) Regulations of 1966 states that any trench of 1.2 metres in depth, or more, must be protected by a shoring system - such as shores or props - used for bracing the trench walls whilst excavation takes place. Trench shoring is sometimes called trench bracing or lining.

 

What PPE is required for excavation?

Excavation workers must wear hard hats, class II high visibility reflective vests, protective boots, gloves, eye protection and other site-required PPE. Ear protection is often required, as well as respirators for certain site conditions. A full body harness is needed for bell bottom trenches or deep excavations.

 

Disclaimer: The information contained on this page is intended as an overall introduction and is not intended as project-specific advice from a qualified professional.