Excavator Hazards and Control Measures

Construction By Matthew Coombes

An excavation of any depth can come with considerable hazards that will need to be controlled.
This article will discuss some of the most common hazards faced by those using excavators and provide suggestions on control measures to control these risks.

Buried services

Buried services such as gas pipes, electrical cables, water mains and more come with significant risks, read our article to find out more about avoiding danger when digging near underground services.

Overhead services

Overhead services such as electrical cables can carry varying currents of 11,000v, 33,000v, 132,000v all the way up to 400,000v. If an excavator, equipment or something in the environment (e.g. an excavator accidentally knocks down a tree) comes into contact with overhead cables, this will create a direct route for the electricity to take to earth. In addition, coming close (within 15m for overhead lines supported by steel towers, and within 9m of overhead lines supported by wooden poles) to overhead lines can even create a significant risk of flashover, whereby the electricity bridges the air gap between the cables and the excavator.

Controls
Working near overhead powerlines will require effective supervision through the use of a vehicle and plant marshaller. This individual will be able to guide the excavator driver and ensure that they do not come near the powerlines. In addition, the working area needs to be well thought out and planned to include markers that the excavator and its arm/bucket should not pass.

When working near an overhead service cannot be avoided or controlled effectively by any other means, it is necessary to contact the provider of that service in order to disconnect it.

Contaminated ground

Excavating ground can release or expose workers to contamination in the ground. Brownfield industrial sites such as old steelworks can have ground containing arsenic leftover from industrial processes, and greenfield sites such as farms may have buried animal carcasses, pesticides or other contaminates.

Controls
The actions and procedures required to control the risks of ground contamination will vary vastly based on the type of contaminant. The process will typically involve:

  1. Desk assessment – A desk assessment uses historical maps and other relevant information such as land use, prior land use, local contaminants and recorded contaminants can be used to identify the likelihood that an excavation will uncover contaminated land. However, a lack of information doesn’t guarantee a lack of contaminants.
  2. Site investigations – Visiting the site and taking samples to analyse either on-site or at a lab.
  3. Lab analysis – Some contaminants will only be properly identifiable with lab analysis.

Water ingress

Water can enter an excavation pit from rainfall, ground water sources, nearby water sources or water pipes. When water interacts with the soil it can change its consistency, eroding the soil away and leading the pit to collapse which can injure or drown any workers in the pit at the time.

Controls
The level of control required to keep water out of the pit will depend on the way that water is entering the pit. Sometimes sandbags to redirect rainwater away from the pit will be sufficient, however when working under the groundwater level, or close to waterways and bodies of water, additional controls such as dewatering and pumps may be required.

Falls into the excavation pit

Open excavation pits are an accident waiting to happen if they are not controlled properly. Workers, contractors and even members of the public may fall into the pit. In addition, any equipment can fall/be knocked into the pit which may damage the equipment itself, or injure workers below.

Controls
Signposting – One of the simplest forms of control is signposting the location of excavation pits so that people are made aware of their presence. This is typically done with safety signs and symbols and procedures and site inductions to ensure people know that excavation pits are on site.

In addition, where possible pits should be covered, have barriers to prevent materials from falling into the pit, and have guard rails to ensure that people do not fall into the pit. When the working area is not in use, it should be secured with appropriate barriers and fencing to prevent anyone from accidentally falling into the pit, especially if it is on a public walkway.

Pit collapse

Removing soil or ground materials will change the way in which forces (gravity, ground pressure, wind etc) interact with the ground. Enough ground pressure exerted by nearby plant, people, equipment or even buildings may cause the structural integrity of the pit to be compromised, and the pit to collapse.

If persons are working in the pit at the time, they can easily be crushed or asphyxiated if the pit collapses on top of them.

Controls
Appropriate reinforcement can prevent the excavation from collapse, and with the correct reinforcement nearly anything is possible. This video by the B1M highlights a huge excavation project happening in the middle of multiple skyscrapers in London.

The type and level of reinforcement required will depend on multiple factors including the depth of the pit, type of pit, soil type, weight of plant, pressures exerted by nearby buildings and more factors.

Mechanical hazards

An excavator, any attachments to it and any relevant equipment that the excavator might interact with (e.g. trench sheeting) pose a significant risk to nearby workers if they are struck. Risks are greatly increased the closer you are to the equipment, including anyone directing the excavator’s movement, or supervising the work.

In addition to the hazards arising from the movement of the arm, jib or anything the excavator is ‘holding’, there is a risk of the vehicle itself striking pedestrians.

This is made more significant by any blind spots that the driver may experience while in the cab.

Controls

  • Segregation – One of the most effective controls is to segregate vehicles from pedestrians. Well designed sites with laid out pedestrian areas and traffic light-controlled crossing points can reduce the likelihood of a vehicle-pedestrian collision.
  • Visibility – Both vehicles in operation and pedestrians need to be visible. This is often done through the use of high-visibility clothing, effective lighting for night working, and sounders and lights for vehicles.

In addition to this, many excavators will have live video feeds to cover any blind spots such as behind the excavator and if the arm obscures the view from the cab.

Vehicle topple

Excavators are heavy pieces of machinery. If they topple it can damage the equipment, surrounding equipment and structures, or even crush people and the weight of excavators often means that they can be very difficult to stand back upright.

The risk of the vehicle toppling depends quite considerably on the environment, condition of the equipment, and the actions of the operator. For example, if the tracks are worn down and unable to grip land, driving over debris and uneven road/land surfaces, if the operator is not driving at appropriate speeds, and if the load is not suitable secured.

Controls
A competent driver, effective training, and planning and maintenance of both the site and equipment are essential for reducing risk on site.

If the excavator does topple, the cab should be suitable to keep the driver safe in the event of most impacts. Wearing a seatbelt inside the cab is essential so that you are not thrown from the vehicle and crushed underneath it.


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