HSG47 was produced by the HSE in 2014 and is the latest information on how to avoid danger from underground services. There are at least 1.5 million km of underground services in the UK, and may be a lot more, because nobody knows for sure. Some 4 million roadwork contracts are carried out every year, and they result in about 60,000 strikes of cables and other underground utilities, many of which cause severe injury and are responsible for around a dozen fatalities each year.

Digging in the street can be an extremely dangerous task because underground services can be anywhere. They are also found in some of the most unlikely places as well, so undertaking a thorough survey before commencing any work is critical. We all have electricity, water, sewage and telecoms services, and many people also have a gas connection. Striking any of these when digging will cause a delay on the contract as an absolute minimum.

There can also be severe financial implications for the contractor because he may be sued for damages and may also be subject to financial penalties from the main contractor. Striking and cutting off telecoms is not all that likely to cause injury, but it can put companies out of business for the rest of the day, or even longer, while the utility concerned carries out repairs. Those companies may very well make a claim for compensation.

However, striking other services can not only cause all of the foregoing problems but can also result in serious injury or death. Striking an electricity cable can cause injuries from the explosive effects of arcing current, together with any accompanying fire or flames when a live cable is penetrated by a sharp tool. The same thing can occur if a cable is crushed and causes the internal conductors to connect. Typical injuries are severe burns to the hands, face, and body, and there is also the possibility of electric shock. Furthermore, other services nearby may also be affected by damaged electricity cables, such as plastic gas pipes.

Damage directly to gas pipes can cause leaks that can lead to fire and explosion. There are two possible types of damage, one which causes an immediate leak and one which may cause a leak later on. The damage can be caused as the work is being undertaken, or it can be caused by something else such as poor reinstatement. For example, a gas pipe may not be properly supported, or it may suffer from unequal forces on it.

Leaking petroleum gas can cause greater problems than natural gas because it is heavier than air, so it doesn’t disperse as easily. It can also travel underground and gather in places such as basements or cellars.

Damage to water pipes is less likely to cause injury, although if water is of sufficient pressure it can cause injury. It may also hurl stones and other debris out of the ground. Damage to mains pipes can result in flooding and could cause the risk of fast collapse of the sides of an excavation, which in turn could lead to drowning if a worker was working in the excavation. There is also the possibility that a leaking water pipe could eat away at the earth supporting other utilities.

Sewer pipes are not generally under pressure, but nonetheless damage to them could affect the health of workers if exposed to raw sewage, and again there is the possibility of soil collapsing and, of course, environmental pollution.

There are also other pipelines which carry fluids and gases which can be flammable causing risk of fire and explosion. They may be toxic, causing the risk of poisoning, or inert, such as nitrogen and argon which carry a risk of asphyxiation.

All of this is why it is essential for operatives to have proper training in the location and identification of underground services. Training courses available include EUSR HSG47 training, PAS 128 Utility Surveyor Training, a QCF Level Three Utility Surveyor Qualification, a QCF Level 5 Diploma Senior Utilities Mapping Surveyor Qualification, and also training in the various tools that are available such as the RD8100, Mala GPR Easy Locator HDR, and Vivax and VScan training.