The biggest problem facing any contractor who has to undertake any sort of excavation work – digging a hole, however big or small – is the fact that there are all sorts of services running under the ground. Obviously, these include electricity, water, telecoms, gas, and sewage, but there can be other things as well such as fibre optics.

Probably the main problem before starting any excavation is the fact that, although utilities have STATS – plans – that you can obtain, they are by no means always accurate and in many instances non-existent. Then, even when they do exist and may be accurate, they can be in different formats, such as vector-based, microfiche, paper drawings, and so on, which makes co-ordinating all the information not only time-consuming but costly as well. However, it should be noted that STATS should only ever be used as a guide and not assumed to be accurate.

To add to the problem, wherever you need to excavate, there are estimated to be anywhere between 1.5 million and 2 million kilometres of underground services in the UK, depending on whom you believe, which is, to say the least, quite a lot. Nobody knows for sure. It also means that those services can be virtually anywhere, even in places you would least expect to find them. In order to repair, maintain, and upgrade all this, the Local Highways Authorities and the utilities between them carry out around 3.5 million street works every year.

Up until now there has been no central source of information and data for underground services and utilities, and neither has there been any simple means of sharing the necessary data. Meanwhile there has been growing traffic congestion as a result of street works, which benefits no-one.

All of which begins to explain why in April 2017 the Institute of Civil Engineers, in collaboration with Infrastructure UK in HM Treasury and the British Standards Institute, published PA256 which is a common code of practice regarding underground services which can be implemented across the UK.

Improving the ready availability and exchange of asset data, together with more effective and collaborative planning and coordination, will lead to better planned road works resulting in significant cost savings; more effective reinstatement practices; longer pavement life; and improved quality of advance information, readily available for any contractor who needs to know it.

However, there is a long way to go before we get there yet. Meanwhile those undertaking any form of underground excavation need to carry out a survey of the area in and around the point of excavation using the tools that are available today which are the CAT and Genny. The CAT on its’ own can only locate metal cables and pipes, but used in conjunction with the Genny, or signal generator, can locate and identify many other underground services.

Any surveyors, or potential surveyors, who need to be able to locate underground services need to attend a PAS256 course which will enable them to understand the latest methods of working and taking into account PA256 itself.

Courses such as this are available, both using the classroom and practical on site PAS256 training. Anybody who undertakes, or is proposing to undertake, the location of and identification of underground services needs to understand not only how to use the CAT and Genny, but also their limitations. And they do have limitations.

For instance, you may be able to detect where a particular underground service is so that you can avoid it. So you decide to excavate four or five feet away from the service so that you do not damage it and cause possible injury to workers or passers-by. The CAT and Genny tell you that there is nothing there, but there still could be. It could be the case that these tools can only read to a certain depth, and that gives the impression that there is nothing there, even though there might be. And those services might be above the level to which you need to dig.

This is why training is so important because it can teach you the limitations of the equipment and also how to deal with it. In this case, you begin to excavate, carefully, and then take a further reading when you have dug down a foot or so, when the CAT and Genny may now locate a service that you didn’t know was there.