At Sygma Solutions, our utility surveyor training covers absolutely everything that an operative needs to know in order to undertake an onsite survey for the location of underground services. While we have some very clever tools available to carry out such surveys, unfortunately nothing in this life is perfect and there are some circumstances where it may not be possible to obtain a reading indicating the presence of a service, so it is essential to take these into consideration.
Any such survey should begin with the use of the CAT – Cable Avoidance Tool – and Genny – Signal Generator. Something such as the RD8100 locator works on electromagnetic principles and can be used for tracing electricity cables and metallic pipes. It can be used in passive mode or induction mode or by direct connection. If there is a live cable or metallic pipe it will emit a power or radio signal which can be picked up by the RD8100 at the surface in passive mode.
If this doesn’t produce a signal, the equipment can be switched to induction. In this case the Genny is set on the ground, and it emits a signal into the ground which should “attach” itself to the service and travel down its’ length and this can be picked up by the RD8100 in induction mode.
Direct Attachment
If neither of these works, then the Genny can be attached to the utility at source with a clamp or clip leads to generate a signal. Obviously, this requires direct access to the utility which might be a cable riser, inspection chamber, stop valve, or plant room. This may be an issue if the utility connection point is behind locked doors or cannot be found. All of this is covered in our utility surveyor training.
Once one has exhausted all of these possibilities, it is then time to use GPR. We provide GPR training as well, of course, using the Mala HDR or HDR Pro. These are mounted on a trolley which is then pushed over the ground with the intention of looking for differences in the soil density which could indicate the presence of services.
Our GPR training also points out its limitations. The radar unit needs to be as close to the ground as possible because otherwise it will not operate, so it can be a problem over rough ground. There can also be issues with wet or clay soils or if there is a lot of rubble, because the signal may be too weak, or it may be jumbled with too many peaks and troughs where the ground is disturbed. It tends to work best on flat ground without too many bumps and dips in it.
