Risks inherent in excavation works - Yleistä


General information on topic

The costs of repairing damage caused by excavation works can be considerable, and it is the guilty party’s responsibility to pay them. In addition to financial losses, the contractors involved in the project can also be taken to court for causing an injury or serious danger.

Most of these kinds of incidents can be avoided with careful planning, by studying maps of cable routes, by using cable location services and by marking the terrain. Cable location services are usually free of charge during normal working hours.

Underground cables must be factored into excavation plans

It is the principal contractor’s responsibility to find out whether there are any underground cables in the project area before excavation works can begin. Underground cables can be property of electricity distribution or telecommunication network operators or private landowners.

The landowner must always be consulted before excavation works are carried out on private land in order to find out the locations of any private cables. Electricity distribution or telecommunication

network operators can also have underground cables on private land. Maps of network operators’ cables must be factored into excavation plans.

Cable location and terrain marking services

It is the responsibility of the principal contractor of a construction project (or, in the absence of a principal contractor, the developer) to get in contact with local network operators in order to determine the locations of any cables and pipelines in the project area. Electricity distribution network operators provide maps of their cables and instructions for interpreting the maps. Cable location services can only be provided once cable maps are available.

Electricity distribution network operators stipulate that the foreman of the site where cable location services are required, or someone appointed by them, is present when the location service provider performs their job. It is the contractor’s responsibility to keep the location information and the labels marking the locations of underground cables for as long as is necessary. If the markings can no longer be seen when excavation works are due to begin, the location service provider must be called back.

In the event of a cable strike

Electrical cables

If an electrical cable or copper grounding (copper conductors are usually used) breaks, the area around the break must be cleared immediately and the network operator contacted and their instructions followed.

It is important to remember that a cable strike can cause intermittent power cuts with the power coming back on automatically. This can happen several times in a row, which is why the damaged cable should not be approached until the network operator has given the all-clear.

Dangerously high voltages can occur between the torn ends of a broken copper conductor. Any damaged copper grounding must always be repaired. A broken copper grounding wire can only be spliced by a qualified electrician.

It is impossible to ensure that power is cut off in the event of a fault, which is why the location of the fault must be guarded until the network operator’s staff arrive at the scene.

Telecommunication cables

The light inside fibre optic cables is produced by a laser or similar. Under no circumstances must a laser beam be allowed to hit a person’s eye. Direct eye contact with the fibre ends should also be avoided.

It is important not to touch the broken fibres. The light may not be noticeable, and tiny fragments from the broken fibres can easily penetrate skin.

The network operator’s representatives provide more detailed safety instructions when the fault is reported.

Risks inherent in excavation works - Työntekijälle


Instructions for employee

Never break ground until you have checked whether there are any underground cables in the area. If there are cables in the project area, make sure that you know their locations well enough and that you have been given detailed instructions for your work.

Risks inherent in excavation works - Työnantajalle


Instructions for employer

Find out whether there are any potentially dangerous electrical cables in the project area before authorising any excavation works. If there is even the slightest chance that there are underground cables in the area,

  • get maps of their locations
  • contact a cable location service provider to locate the cables
  • ensure that the markings in the terrain remain visible for as long as they are needed, and
  • make sure that the digger operator is told about the locations of the cables and given detailed instructions for their work.

Proper handling of cables requires that

  • the recommended distances are observed when using excavation machinery
  • the trial holes are dug with particular care
  • any cables that are dug up are protected and provided with proper support
  • cables are not moved to new locations without good reason (if a cable must be moved, the network operator carries out the work)
  • live cables are never manoeuvred
  • the base of the cables is properly compacted, and
  • the cables and any conduits are checked before reburying.

The same also applies to any underground pipelines. Information on the depths at which cables must be reburied is provided by the network operator. Pipelines should be treated the same as electrical cables.

Risks inherent in excavation works - Lainsäädäntö



Occupational Safety and Health Act (738/2002)

  • Section 8 – Employer’s general duty to exercise care
  • Section 10 – Analysis and assessment of the risks at work
  • Section 14 – Instruction and guidance to be provided for employees
  • Section 39 – Physical agents and electrical safety
  • Section 52 – Obligations on a shared construction site
  • Section 53 – Obligations of self-employed workers at a shared workplace

Government Decree on the safety of construction work (205/2009)

  • Section 2 – Definitions
  • Section 3 – General obligations of the parties to a construction project
  • Section 10 – Safety planning of the construction work
  • Section 11 – Design of the use of the construction site area
  • Section 12 – Management of construction work
  • Section 13 – Execution of construction work

Electrical Safety Act (1135/2016)

  • Chapter 6 – Damage and inconvenience

Risks inherent in excavation works - Esimerkkitapaukset


Examples and good practices

Excavation and earthworks require special care. Cables may have moved closer to the surface or away from their original locations due to, for example, frost, groundworks, ditch cleaning or previous excavation works, and it may be impossible to determine their exact depths. The network operator must be consulted if necessary. Warning tapes may also have been removed due to the aforementioned reasons.

Any decommissioned cables should be treated the same as live cables.

Risks inherent in excavation works - Sanasto


Developer An individual or organisation engaged in a construction project or another person who directs or supervises a construction project. In the absence of a developer, the developer’s duties are assumed by the contractor.
Principal contractor The contractor whom the developer has appointed as the principal contractor or the employer who principally oversees the project. In the absence of a principal contractor, the principal contractor’s duties are assumed by the developer.
Network operator An entity or an organisation that operates, for example, an electricity distribution network subject to a licence.