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15th October, 2019

Finding Underground Services (Colours And Identification)

We all use services, gas, electricity, water, communications. Across the UK, we are connected. Services power our homes and businesses and take our waste away. And many of these services are laid underground. Out of sight, out of mind. Until you need to dig. If you ever need to dig up the ground, or excavate land, assume that services could be present. But what services, and where? Before you dig yourself a hole (literally!), you need to know.

In an ideal world, finding underground services would never come as a shock. You would have a survey and a map of the exact location of all the underground services pinpointed to the exact location and depth. And once exposed, services would be easily identified by the national colour coding system.

But this isn't an ideal world, and working underground is often more difficult than planned. Service maps are often not to scale and just a rough guide as to where services are hidden. A wide variety of materials and colours have been used for services over the years, making identification difficult. If underground services have been uncovered on your site, it is important to correctly identify the type of service so you can deal with it safely. Failing to work safely around underground services can be deadly.

A construction company paid £210 000 in fines and costs after an employee died in an explosion following damage to an 11 000-volt live cable within an excavation. The worker suffered burns over 60% of his body while he and other workers were using breakers and a shovel within the excavation. He died of his injuries 13 days later. The company had not informed workers that there were live cables in the excavation and failed to put adequate measures in place to prevent them being damaged.

Locating services isn't just important to avoid damaging the service. But to avoid damaging, or killing, yourself. You need to know what services are where. And, if they are dead or live.

Locating underground services is usually a three-step process.

  1. Desktop study Requestion information from the client and service drawings from utility providers, to give you an idea of the type and location of services located on the site.
  2. Site Investigation Which would usually involve a physical site inspection, looking for signs of services (e.g. manhole covers, telecoms boxes etc). The survey would use detection tools to get a more accurate idea of service locations.
  3. Physical Identification Using trial holes and tracing devices to get an exact location, depth and identity of services.

You should have a good idea from utility services searches and non-intrusive site surveys as to the location and type of services you are likely to come across on your site. However, not all records are up to date and it can be difficult to determine the exact type of service from non-intrusive surveys. Sometimes, it is not until the services are exposed on site after an intrusive site investigation, with trial holes and careful excavation work, that they can be identified.

electrical danger
Contact with underground services can be fatal

Surely, once the services have been exposed during the physical identification they can easily be identified? Not always. Even at this stage, it can be difficult to determine the exact type and status of service. Modern services tend to follow a national colour coding system:

  • Black – Electricity
  • Red – Electricity (Some High Voltage)
  • Orange – Street Lighting (England and Wales) and Traffic Control
  • Purple – Street Lighting (Scotland) or Communications
  • Blue – Water
  • Yellow – Gas
  • Grey – Telecommunications or Water
  • White – Telecommunications
  • Green – Cable TV and some Telecommunications

High pressure or hazardous fluids will usually be carried in welded steel pipes.

These guidelines describe utility industry practice. However, it should not be assumed that all apparatus will conform to the recommendations for positioning and colour coding contained in this publication.

While modern services should conform to this system, older services can be more difficult to identify as a wide variety of colours and materials have been used in the past that didn't always to conform to any particular system.

  • Some colours may not be clear under poor lighting or artificial lighting.
  • Underground services may also be hidden in protective ducts, and ducts could include any service types, making it difficult to identify the services.
  • Some services could be covered in black plastic. These services can include water pipes, fuel, electricity cables and telecommunication cables. If black plastic is found always assume the service is a live electricity cable.
  • Water pipes can be made of iron or steel and can appear very similar to gas pipes. In the interest of safety, and such pipes should be assumed to be gas.

The identification of services should usually follow a system. Firstly, service records are gathered. A site survey scan should then confirm the location of the services identified within the plans. Trial holes are then dug to confirm locations and further safe digging used to expose services as required.

digger
Check for services before you dig

However, work underground is rarely straightforward and at any stage in the above process, additional unknown services (live or dead) may appear on the radar as you scan the site.

If you are unsure about any services on your site, always assume the service is live electricity cable or gas pipe until otherwise confirmed. After all, it’s better to be safe than sorry.

Once you have identified services, they should be carefully exposed, supported and marked. Marking should be carried out on-site, and on plans. Always assume services are live, unless you know otherwise. And be aware the status of services can change. Isolated services may become live again during a project, so always check and get confirmation from the service provider.


Any work that involves digging or disturbing the ground should consider the risk of underground services. Never go into ground unprepared. Before work starts on your site, service records should be checked and an initial assessment of the likelihood and location of services carried out.

Raise awareness of the risks with the underground services toolbox talk, and make sure your team know how to dig safely.

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This article was written by Emma at HASpod. Emma has over 10 years experience in health and safety and BSc (Hons) Construction Management. She is NEBOSH qualified and Tech IOSH.

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