Protection against buried cables

Accidents may occur, if care and attention are not used, when excavating to locate underground cables. Hand-held power tools and mechanical excavators are the main cause of accidents, so they must not be used close to underground cables. The risk of danger can be avoided by following a few basic rules.

Before starting work:

• complete a suitable risk assessment
• set up the appropriate road signs, barriers and cones
• wear high-visibility clothing and any other PPE needed to carry out the task safely
• check the area drawings to find the number of cables, their voltage ratings and their physical dimensions
• use a cable detector to trace the line of the cables and mark their route on the ground
• where no cable or other utility records exist, consult your supervisor

When work begins:

• avoid using a hand-held power tool or mechanical excavator close to a known cable or other utility
• use the competent safe-digging method selected for the services and ground conditions. Hand digging can still damage a cable; do not use a pick or other pointed tool close to a service merely because it is used carefully
• during excavation, repeat the checks with the cable detector to find the position of any cable more precisely
• treat all cables found as live until proved otherwise
• if there are any signs of distress in a cable or joint, such as smell, heat, noise or damage, stop work, withdraw and consult the supervisor
• backfill around cables with fine material and do not use hardcore, which is likely to cause damage
• replace any warning tiles or tape that has been disturbed
• treat other utilities such as gas, water and telecommunications with respect
• report any damage to the other services to your supervisor

Protection against overhead cables

Plan and manage work near overhead power lines so that the risks from accidental contact or close proximity are adequately controlled. The precautions depend on the nature of the work and are essential even when the work near the line is short. Safety can be achieved through a combination of measures.

• Planning. First find out whether there is any overhead power line within or immediately next to the work area, or across any access route. The local electricity supplier or distribution network operator can give this information. If overhead lines are found, assume they are live unless their owners prove otherwise. If there are lines over the work area, near the site boundaries or over access roads, consult the owners so that the proposed plan of work can be discussed. Allow enough time for lines to be diverted or made dead, or for other precautions to be taken.
• Avoidance. Find out whether the work really has to be done under or near overhead lines or could be done somewhere else. Make sure materials are not placed near overhead lines and temporary structures are put up outside safe clearance distances.
• Diversion or isolation. Arrange for overhead lines to be diverted away from the work area, or made dead while the work is carried out.
• Controlling access. Where there is no scheduled work or need for access under the lines, erect barriers at the correct clearance distance from the line to prevent close approach. The safe clearance distance should be obtained from the distribution network operator. Where people or plant must pass under the lines, make defined passageways. Keep the danger area as small as possible by limiting the width of the passageway to the minimum needed for plant to cross safely, and if possible cross the route of the overhead line at right angles.
• Clearance. The safe clearance needed beneath the overhead lines should be found by contacting the distribution network operator.
• Exclusion. Vehicles, plant, machinery, equipment or materials that could reach beyond the safe clearance distance should not be taken near the line.
• Modifications. Vehicles such as cranes, excavators and telehandlers should be modified with suitable physical restraints so they cannot reach beyond the safe clearance distances, with measures to make sure the restraints are effective and cannot be altered or tampered with.
• Maintenance. Operators of high machinery should be told not to carry out any work on top of the machinery near overhead power lines.
• Supervision. Access for plant and materials and the working of plant should be under the direct supervision of a suitable person appointed to make sure the safety precautions are observed.

Summary notes for Element 11 · Cheat sheet · Glossary. A study aid, not published or endorsed by NEBOSH.