If you are digging or disturbing the earth in any way, it is essential to avoid damage to underground services, partly because the damage can have financial implications, but even more importantly because of the danger to life and limb. Underground electrical cables in particular can be extremely hazardous because they often look like pipes and it is not possible to tell if they are live simply by looking at them. The Electricity At Work Regulations 1989 state that you must take precautions to avoid danger.
Careful planning and risk assessment are essential before any work is carried out. In particular, if you are excavating near cables, they must be located by someone trained in the use of the CAT and Genny. Most service cables belong to a DNO (Distribution Network Operator) but some belong to the Ministry of Defence, Network Rail, or the highways authority. It is necessary to check nearby for equipment that may be owned by these organisations and if it is believed that there may be underground cables you should check with them and ask for plans. It may also be necessary for someone from the organisation to come and locate them accurately for you.
It may also be necessary for the cables to be made dead while you carry out the work, in which case it is necessary to know that the electricity supply authorities are required to give five days' notice to customers before cutting off their supply.
If work is being carried out as an emergency, and there are no plans or other information, the work should be carried out on the assumption that there are buried cables in situ.
Symbols on electric cable plans can vary from one utility to another, so it is necessary to get advice from the issuing authority. Furthermore, high-voltage and low-voltage cables may be shown on separate plans.
Whether plans are available or not, the area should be thoroughly searched by a surveyor using the CAT and Genny who has undertaken a CAT and Genny training course. CAT training is essential for all surveyors who need to locate underground utilities of all types. The locators should be used often during the course of the work for maximum safety. Before any work begins, cables that have been located should be clearly marked. Once cables and routes have been identified using locating equipment, trial holes should be dug by hand to confirm the accuracy of the position. Excavation must be carried out alongside the cable and can then finally be uncovered by hand digging horizontally. Hand tools used for digging near electricity cables should be suitably insulated.
It is not only electricity cables that need to be located. Gas pipes can also be extremely dangerous. Water pipes are less so but can still cause danger to life with severe flooding. There are also other things to consider. For instance, in February 2010 a young child was killed and a woman injured when a lamp post fell on them. It was just outside the edge of a site where street works were taking place. The lamp column had a non-standard root design where the root was off-set from the lamp column itself. These are not very common, and are usually used when there is a need to avoid existing underground services when the lamp column is installed. In this instance, the cause of the accident was that the offset root of the lamp was completely cut through.
All companies undertaking any sort of excavation work must ensure that their surveyors have undertaken a CAT course, and preferably one that is recognised. It is possible to find an EUSR CAT and Genny course where the training company is EUSR approved, and CITB approved. Nationally recognised qualifications in utility detection and mapping include the Level 2 Award in Utility Location & Avoidance, which is a requirement for undertaking work on HS2 and is now also requested by some utility companies and other sites.