What Is Buried, and What It Does to You

This booklet outlines potential dangers of working near underground services, utilising equipment (Genny and CAT) and gives advice on how to reduce the risks. It deals principally with risks to health and safety rather than damage to services. However, precautions taken which reduce risk to people's health and safety will generally also reduce the risk of damage to services, which can directly or indirectly pose a risk to people's health and safety.

Damage to underground services can be fatal or cause severe injuries as well as significant disruption and environmental damage; it can also delay the project and incur considerable costs.

Injuries are usually caused by the explosive effect of arcing current, and by any associated fire or flames that may result when a live cable is penetrated by a sharp object such as the point of a tool. Such effects can also occur when a cable is crushed severely enough to cause internal contact between the conductors, or between metallic sheathing and one or more conductors. Typically, injuries are severe and potentially fatal burns to the hands, face and body; electric shock is possible but less likely.

Incidents may also arise from cables, connections and terminations which have been damaged but left unreported and unrepaired, or which have deteriorated with age.

Damage to gas pipes and connections can cause leaks that may lead to fire or explosion. There are two types of damage: damage that causes an immediate leak, and damage that causes a leak sometime later.

The damage may occur when the work is carried out, or subsequently; for example, poor reinstatement may leave a pipe inadequately supported or subject to unequal forces.

Although damage to water pipes is less likely to result in injury, the following may occur:

• 01A jet of water from a main can be of sufficient pressure and intensity to injure a person. It may also contain stones or other hard objects ejected from the ground around the pipe.
• 02Leaks of water from underground pipes can affect adjacent services and reduce support for other structures.
• 03Damage to mains pipes can result in flooding, leading to subsequent risks from drowning or the rapid collapse of support to the sides of an excavation; water can enter gas pipes if they are also damaged.

While some sewage is pumped at pressure, sewers are generally gravity-fed and the main risks from damage to a sewer are to the health of workers from exposure to raw sewage, the chance of ground collapse and possibly of environmental contamination and pollution.

The danger arising from damage to other pipelines depends on the nature of the conveyed fluid. Fluids and their associated risks include:

• 01Flammable liquids and gases: risk of fire and explosion.
• 02Fluids at elevated pressure: risk of injury from sudden release of contents.
• 03Toxic liquids and gases: risk of poisoning.
• 04Inert gases such as nitrogen and argon: risk of asphyxiation.

Very often a fluid will present a combination of risks; for example, a liquid may be both toxic and flammable.

Damage to telecommunication and cable TV cables may require expensive repairs and can cause considerable disruption to those relying on the system. However, the risk of personal injury is normally very low.