HSG47 is a guide from the HSE about avoiding the dangers of striking underground services when undertaking any form of digging or excavation work. It could apply to anyone anywhere, including a private householder who decides to add an extension to his or her home which involves digging for foundations. This could be right over the spot where the home’s electricity supply cable runs!

By and large, HSG47 refers to contractors who undertake excavation on a regular basis. This can be with hand tools such as a spade and fork or with something much larger like a JCB. The fact is that if you hit an electricity cable, gas pipe, water pipe, sewer, or anything else, you can be in a lot of trouble.

Another fact is that underground services can be found anywhere, even in the most unlikely places. Certainly, you can and must check with the local utility suppliers who may be able to supply you with a plan. Then again, they may not. Then again, if they do, it may not be accurate!

There are other problems too. If a contractor is carrying out excavation work in a high street or private residential road, it is obvious that there will be underground services there. Electricity, water pipes, gas pipes, sewers, as a minimum, but there could also be fibreoptic cables, telecoms, and so on, and other pipes carrying inert gases such as nitrogen and argon, other fluids at high pressure, and more.

Then there is another big problem with underground services. You may have to dig down two metres, so you use the appropriate tools - chiefly the CAT and Genny – to establish whether there are any services there and you find nothing. So you dig away happily only to strike a service 1½ metres down! How did that happen? Some tools only read down to certain depths, so while at ground level your CAT, for instance, said there was nothing there, it was because it could only read down to 1 metre. The only way around this is to begin to dig cautiously, perhaps down a foot or so, and then take a further reading with your CAT and Genny. And so on. That way, you can locate services that could not be found from ground level.

There’s another problem, too. Suppose one service is running directly beneath another one?

This is why, despite all the tools we have today to locate services, there are still an average of 230 cable strikes across the whole of the UK every working day – about 60,000 a year!

Striking underground services when excavating can cause problems ranging from something of a nuisance to fatalities. Yes, there are around a dozen fatalities every year, and a considerable number of severe injuries – some of them life-changing.

Cable strikes can result in severe problems for a contractor, not the least of which are financial penalties. The utility concerned may claim for damages. The main contractor may exert financial penalties. At the very least you have men standing around idle while the utility is repaired. However, there are further issues such as damages claims by businesses who have been shut down because there is no electricity and no internet. Worse still, striking a gas pipe could cause an explosion and fire severe enough to demolish whole buildings.

There is also the damage to the reputation of the contractor involved which can result in the loss of future business.

The fact is that this does actually happen – daily – to a greater or lesser degree. This is why there are companies that provide HSG487 training in the use of the tools that surveyors need to use in order to locate underground services before even poking a fork into the ground.

A good HSG47 course will not only teach surveyors how to use the CAT and Genny, and also other locators such as the MALA Easy Locator which uses ground penetrating radar, but will also, critically, teach them the limitations of the equipment. And yes, they do have certain limitations. The tools have different modes in order to deal with different situations, and when a surveyor knows and understands how to use them correctly, together with their limitations, there is far less chance of damage and injury on site.