The Hazards Faced By Contractors Undertaking Any Type Of Excavation

By Author: Peter Ashcroft
Total Articles: 17
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There are many hazards associated with carrying out any sort of excavation work. The simple fact is that wherever you are there are very likely to be underground services nearby carrying electricity, gas, water, sewage, telecoms, fibreoptic cables, and more. Striking any of these, whether with a hand tool or a machine, can result in anything from a nuisance because work has to stop while repairs are carried out, to personal injury, and occasionally can lead to fatalities.

Certainly, if you are out in the countryside surrounded by fields there are less likely to be underground services there, but even so you cannot be certain. Even in your own front garden you could accidentally strike your telephone cable or drainage system if you don't know where they run.

The first step before undertaking any form of excavation is to contact the local utilities and ask them for plans. These should not be taken as gospel because they are not always accurate, but at least you can use them as a guide. This means that wherever you are planning to dig, you need to undertake a survey using the CAT and Genny in combination in order ...
... to determine as accurately as you can the layout of underground services in the spot that you intend to excavate and close to it.

Two of the most dangerous utilities to strike are electricity cables and gas pipes. Striking an electricity cable can result in arcing which can cause severe burns over the whole body which can be fatal. Electric shock is also possible, but less likely. However, if an electric cable is close to a gas pipe and that is also damaged it can obviously lead to an explosion which in some instances can be severe enough to bring down a building. The same thing can occur if a gas pipe is struck directly.

Damage to a gas pipe can result in an immediate leak, or it may lead to a leak later on. This can occur as work is being carried out, or it could be the result of bad reinstatement where a gas pipe was not properly supported. The risk of leakage from liquified petroleum gas pipes is actually greater than natural gas because it is heavier than air and doesn't disperse easily. It can also travel for long distances underground and accumulate at low level, such as in a basement car park for instance.

Damage can also occur to sewers. The danger here is from contamination and the health risks to workers in the immediate area from raw sewage. There is also a chance of ground collapsing and of environmental pollution.

Striking a water main can also result in injury, since a jet of water under pressure can be very strong and may also contain within it stones or other debris from the surrounding soil. Damage to mains pipes can lead to flooding and the risks of drowning if a burst is severe enough. Water could also enter damaged gas pipes and damaged electricity cables as well.

Apart from the obvious health risks, there will always be a delay on site since the utilities concerned will have to carry out repairs. This may lead to the main contractor placing penalties on the sub-contractor responsible and could also result in damages claims from local businesses who have been affected. If a worker has been injured, then there will certainly be damages claims for his injuries and these could run into hundreds of thousands if those injuries are severe enough that he may never be able to work again. In the event of a fatality, there will be damages claims from affected relatives.

All of these are very sound reasons for undertaking a thorough survey of the area in which an excavation is about to take place. Even so, the CAT and Genny have certain limitations, so there may be instances where nothing is shown even though there may be a utility in that particular spot. Excavation should always proceed cautiously, and a further survey with CAT and Genny should take place after about a foot of earth has been removed. This is because there may be a utility which the equipment was unable to detect from ground level because it was too deep, but which may be apparent with a further survey.
Sygma Solutions is the leading provider of CAT and Genny training in the UK and runs courses which are approved by the CSCS, EUSR, and The Survey Association.