Nobody knows exactly, but it is calculated that there are some 2.5 million miles of underground services in the UK. These include electricity cables water pipes, sewage pipes, telephone cables, fibre optics, gas pipes, and more.

Furthermore, these services can be found anywhere, even in some of the most unlikely places. Obviously, almost all of them will be found in any built-up area, but they can also be found out in the countryside, apparently miles from anywhere. We all need electricity, water, and telephone lines, along with sewage pipes. We may or may not have a supply of gas to our homes. Even if you live in a farm in the middle of a field, you still need these services, and apart from some telephone wires, they all run underground.

That means that they cannot be seen with the naked eye, and that presents a major problem for any contractor who needs to undertake any sort of excavation work, even if it is only digging a foot or two into the ground. Certainly, the first thing to do is to contact all the relevant utilities in the area and get copies of their plans. However, it is not safe to rely on them. Some are not complete, and others can be quite inaccurate: they should only ever be used as a guide, not taken as gospel.

In fact, the statistics are quite horrific. It is thought that there are some four million excavation works of all descriptions every year, and of those, around 60,000 result in a cable strike. At the very least, that means that a contractor has men standing idle while the utility concerned send men out to repair it. However, it is usually a lot worse than that. If a telephone cable is knocked out next to an industrial estate, those businesses suddenly have no internet. Strike an electricity cable and a factory has no power and cannot operate.

However, it gets worse because striking many of these can and often does result in severe injury, and on occasion is fatal. Striking an electricity cable can lead to severe and instant wounding, while a gas pipe can lead to fire and explosion. Even a water pipe can cause problems as water under pressure can hurl stones out of the ground. Striking a sewage pipe just really doesn’t bear thinking about, especially if you are a worker in a six feet deep trench at the time.

Not only is there the danger of injury, both to workers and passers-by, but businesses who have been put out of action may well claim for compensation. The main contractor may hold the sub-contractor responsible and raise financial penalties as well. If anyone is seriously injured – or even only slightly injured – there is a small army of ambulance chasing lawyers in every town who are only too happy to work on a "no win, no fee" basis because they know that in most cases they are going to win, and win big, and their usual fee under those circumstances is 25% of the compensation the court awards. Trebles all round, folks!

Furthermore, the amount of damages and compensation could easily put the contractor out of business, but even if it doesn’t that contractor’s reputation could be so badly affected that he goes out of business that way instead.

All of which is why it is absolutely essential to undertake a thorough survey of anywhere that a contractor proposes to dig before even inserting a spade into the ground.

The two main tools that are used for underground surveys are the CAT and Genny (Cable Avoidance Tool and Signal Generator). Now it is by no means safe to buy one of each, take them out of the box, and read the instructions. Anybody who is going to undertake an underground survey must first attend a recognised course on the use of the CAT and Genny because, apart from any other considerations, they do actually have some limitations and it is essential to understand what those limitations are and how to overcome them. The risks for anyone who has not been thoroughly trained in their use are far too great, and just not worth taking.