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Temporary and permanent services have always been hazardous areas for commencing works on site. Problems can be encountered from the site setup stage through to construction stage.
The project management team is responsible to ensure that the procedure is implemented; the electrical contractor’s method statement must be reviewed prior to work commencing to ensure that a safe system of work is in place. If in any doubts then contact the H&S Department for advice. All electrical equipment and installations should be maintained to prevent hazards occurring, regular inspections must take place on any electrical equipment and installations, periodic testing is required at specified intervals
Contact with underground high voltage cables causing electric shock, burns, fire or explosion are potentially fatal along with fire or explosion caused by contact with gas mains. Additionally, there are commercial considerations if electric, gas, or telecom supplies are interrupted during our works on site where the financial implications could be significant.
Examples of temporary or permanent services are:
Electricity supply cables both overhead and underground;
Gas mains of high and low pressure;
Water mains high and low pressure;
Fibre optic cables;
Telephone cables overhead and underground;
Electrical cables in houses for domestic supply;
The information provided in the Safety Information Pack must be checked at the site setup stage. Liaison with the respective utilities suppliers will be a pre-requisite and a requirement under the CDM regulations for utility companies to provide information and undertake reasonable enquiries to locate their equipment.
Although any services drawings provided can only be used as a guide, the information on most utilities drawings will not be accurate and should not be relied on. The only effective way is to get the relevant utilities providers trace and mark the route of their services on site. This work must only be carried out by trained and competent personnel.
Always assume services will be present when carrying out excavation work on site or in the streets pavement or near existing buildings. Use up to date service plans, use of CAT & Genny and safe digging practice to avoid danger. Service plans should be available from regional electricity and gas companies, local authority’s highway authorities and telecoms providers. Such plans cannot be guaranteed as being accurate but provide a good indication of the location of any known service. A permit to break ground HSF 401 is to be completed for all excavation works. When a Permit to break ground identified a buried service within 500mm and we have ‘as built’ records of the service laid, our engineer must use the ‘as built’ data plotting the exact location of the service and clearly spray marking the location.
Penetrating road pins must NOT be used for any setting out, erection of fencing or demarcation. These pose a high risk to striking and damaging underground services, placing the operative at risk of electrocution or burns from subsequent damage. Non-penetrating pins must be used in all circumstances. For sites where no services exist, such as green field sites, permission can be granted to use penetrating road pins from Operations Director and H&S Director.
If in any doubt stop work and consult the utilities company, damage to services can be very expensive and very hazardous. No work with mechanical plant or machinery should take place within 0.5m of any known underground service.
When backfilling mains services, sites are to use 1-Ton bags filled with sand or ballast. These can be placed onto the service mains before they are backfilled at the location where plot service connections will be made. At a later date when exposing the service mains for plot service connections, the 1 Ton sand bags can either be lifted out or the sand removed by hand digging, which will safely open an excavation to allow the service connections to be completed, without the need for any mechanical excavating.
Gas purge valves located at the end of each section of Gas main are placed to allow the air to be purged from the main to liven the Gas main. However, these valves are a vulnerable area and require additonal protection. When backfilling Gas main, any Gas purge valve must have a section of vertical gas duct placed over the valve, be sanded and taped. This will create a clear visual reminder of the location of the Gas purge valve.
When working near overhead power lines it may be possible to have the electricity current turned off if the owners are given enough notice. If this is not possible the owners must be contacted about the safe working distance from the cables (usually 6-7 metres). Electricity can flash over from overhead lines even though equipment does not touch live conductors. The clearances required will be given by the electricity company and the measurements given may have an effect on the type of plant which can be used, cranes, piling rigs, scaffolding etc. Guidance found in ‘Avoiding danger from overhead power line Guidance note GS6 (Forth edition) can be used to identify the safe distances to be set dependant on voltage.
When plant is required to travel underneath overhead powerlines goal posts must be erected to ensure safe distances can be maintained whilst travelling underneath. Again, these distances can be found in the GS6 document.
If work is required close to operational railways you must consult with the operating railway company. Electricity for railways can be via overhead lines at 25,000 Volts or via a 3rd rail at 750 volts safe clearances will be provided by the railway companies. In some cases work may only be carried out after the electricity supply has been isolated in a Railway Possession Period. Specific training in railway track safety will be required, i.e. PTS, COSS or PICOP. If power is interrupted to the rail network the costs can be hugely expensive.
All supplies to construction areas will be 110 volt (where possible), this includes temporary lighting and electrically operated power tools. The power supplied to the site electrics will come from centre tapped to earth transformers which will limit the supply to the lowest voltage needed to complete the task. All electrical systems must be installed to BS 7671 and be regularly maintained at specific intervals.
Before equipment is used on site the temporary electrical installation must be commissioned and tested, copies of the certification will be provided to the site manager. All electrical mains distribution panels must be secured and lockable to prevent unauthorised entry by untrained personnel. Only trained and qualified electrical contractors or engineers can work on electrical equipment.
All site electrical tools and equipment must be 110 volts regularly tested and be double insulated to offer maximum protection. Equipment and tools which have damaged insulation or leads which may have been taped together must not be permitted on site.
With temporary halogen lighting it is vital that the lamps are protected from contact with flammable materials with adequate covers. Trailing leads should also be avoided they pose a trip hazard and can also suffer impact damage, if practicable electricity supply leads can be fixed to corridors above head height.
If work is required to be carried out on live equipment during commissioning of the electrical installation, only trained and qualified electricians must carry out the work. Work must only be carried out on live systems if there is no reasonable practicable alternative. Any such work being carried out must only be done on the issue of an Electrical Permit to Work or local detailed procedures. (This can only be authorised by an Electrical Duty Holder in the electrical contractor)
A risk assessment and method statement must be produced prior to any work on or near to live electrical systems and this must be communicated to all personnel involved. When electrics are being commissioned safe means of isolating live supplies must be detailed in the electrical contractor’s method statement, live cables must be mechanically isolated in a terminal box or joint box. Warning signs must be clearly displayed if work on live electrics is in progress. Electrical supplies must be locked off to prevent unauthorised use.
The frequency of testing electrical equipment both permanent and temporary is as follows:
| Type of installation / equipment | Frequency |
| Permanent installation (e.g. office) | Every 5 Years |
| Temporary installation (e.g. project office) | When installed, then annually thereafter |
| Portable equipment - office environment | Before use and then Annually |
| Fixed equipment – Site environment | Before use and then Annually |
| Portable equipment – Site environment | 3 monthly |
All electricians must hold ECS cards to prove their competence.
