At Sygma Solutions we provide training that covers all types of underground services location tools, including the CAT and Genny and the Radiodetection RD8000 and RD8100, as well as the Mala HDR ground-penetrating radar tools.

Between them, these tools can locate and identify most underground services, but there are always certain limitations, and our courses teach how to recognise them.

The RD8000/8100 can be used in three modes – the passive mode, the induction mode, and direct connection mode, and our Radiodetection RD8100 training covers all three, as you might suppose.

In passive mode, the signal from a service that is picked up by the receiver at ground level is from the cable giving off its’ own background signal. An electric cable or a telecom cable emits its’ own power or radio signal provided it is strong enough, this can be detected at the surface. If the utility is dead or turned off it will not emit any signal and therefore it cannot be detected by the passive method. For example, if electricity is running through a cable to the street lights, the signal will be emitted, but during the day, when the street lights are off, there won’t be a signal. This is just one of the many things that are covered in our training courses at Sygma Solutions because a novice might believe that there is no utility there and as a result commence digging.

So if it is winter, say, and gets dark at 4.00 pm, it would be possible to strike a live cable that the survey undertaken at 10.00 am indicated was not there!

Another issue here is that some live cables cannot be detected this way anyway. Some high voltage cables are designed specifically so that they do not emit any signal. Some ductile iron pipes can also be difficult to trace. This is because some iron pipes have a rubber seal at the end of each section of pipe and this has the effect of breaking up the conductivity of the signal, so only small sections of the pipe may be able to be located.

When the site has been surveyed using the passive mode and no further signals can be found, it is then necessary to switch over to induction mode with the Genny. The Genny is usually placed on the ground and generates a signal into the ground with the object of it “attaching” itself to a buried service and then travelling along the length of that service so that the RD8100 can locate that signal with the receiver in the induction mode, and follow the route of the service and mark it accordingly.

In some instances, it is not possible to trace a signal in either induction or passive mode and in this case, it is necessary to attach the Genny to the service directly using a clamp or clip leads. Obviously, in order to do this, it is necessary to have access to the service and this will usually be via an inspection chamber, stop valve, cable riser, or a plant room.

Sometimes it may not be possible to find a place for a direct connection in the survey area and if this happens the surveyor will need to widen the search area, but there comes a point at which this has to cease because otherwise, the search area becomes too big. This is one reason why it is essential to obtain STATS wherever possible because they may give an idea of where it is possible to find an access point.

If none of these methods produces a result, then it is time to turn to GPR – Ground Penetrating Radar, using something such as the Mala HDR Pro. This doesn’t locate services directly but looks for differences in the ground density which can indicate where they may be. The GPR is mounted on a trolley and the actual radar unit needs to be close to the ground. This can prove difficult in bumpy terrain where it can be difficult to push the unit along the ground. There may also be problems if the services are buried in heavy clay soils which are wet or perhaps contain lots of rubble that has been backfilled.

All of these things are taught in our training classes at Sygma Solutions so that operatives fully understand how to use the tools and what limitations there may be.