Article Safety

Underground Services and Utility Plans

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Figures provided by the Health and Safety Executive (HSE) record around 30 fatalities a year through contact with electricity. Most of these fatalities arise from contact with overhead or underground power cables and even when non-fatal, they can cause severe and permanent injury. Within the ground investigation industry, the potential for striking underground services is far greater than from coming into contact with overhead services and it is possibly the greatest risk we face.

The ability to react quickly to the requests of clients is seen by many companies as their competitive advantage, but this has to be balanced against the legal requirement to reduce risk. Any measures taken should be in accordance with the general principles of the Management of Health and Safety at Work Regulations 1999 further clarified in the Construction (Design and Management) Regulations (CDM) 2007 :

  • clients shall ‘provide appropriate pre-construction information to designers and contractors’
  • all parties shall allow sufficient time to obtain vital pre-construction safety information

To help companies discharge these duties the HSE provides clear guidance on how to reduce the level of risk from underground services in their publication ‘HSG47 – Avoiding Danger from Underground Services’ . Within HSG47 the HSE outlines the requirement for any company involved with work where there is a risk of contacting underground services, to have in place and use a safe system of work consisting of four elements:

  • Planning the work and risk assessment
  • Maps and plans to identify the presence and location of underground services
  • Cable and pipe locating devices
  • Safe digging practices

Planning the work, assessing risk, using cable avoidance tools and safe digging are in every safe system of work but the use of utility plans is often absent. So why do many people take a short cut that could result in injury or fatality?

Initially it is the inability to obtain utility plans within the timescales demanded by clients and the commercial pressure to deliver reports and studies on time. Although utility plans are generally available within five working days they can take longer and this may not fit the expectations of the client, particularly where the decision to purchase land depends on the outcome of a report by a fixed deadline. But in the context of CDM2007, the provision of utility plans and any resulting delay in mobilisation is seen as strong evidence that all reasonable care has been taken to protect staff and members of the public.

CDM has always defined construction as:

‘Any civil engineering ….the preparation for an intended structure, including site clearance, exploration, investigation (but not site survey).’

Historically, the geotechnical and environmental sector has often viewed its work as exempt from the requirements of CDM as work only fell within the scope of the regulations when the work was ‘in preparation for a structure’. With the revision in April 2007 this requirement has been clarified and it is now clear CDM applies to work undertaken in ‘preparation of sites for use’, whether notifiable or not. It should be noted that irrespective of CDM there is an existing duty of care and HSG47 still applies.

The intention of a safe system of work is not necessarily to eliminate risk entirely but to reduce it to a level “as low as is reasonably practicable”. This is recognised by the HSE. However, for a safe system of work to be effective it must incorporate all four of the elements outlined in HSG47 and referred to earlier. The role of utility plans should be viewed in this context. Each element in the safe system of work has limitations, but they complement each other and when used together address the fundamental weaknesses of each.

The planning of the work and the development of risk assessments is the initial stage of the safe system of work. Understanding the site, its history and the nature and location of any likely services, will initially determine costs of works and the cable detection technology required. This can only be done with reference to utility plans.

Utility plans have limitations and this is often used as a justification for not including them in safe systems of work. Utility providers acknowledge their services rarely run in straight lines, surface depths may have changed, datums such as kerblines may have been moved and plans may only run to site boundaries. They all carry disclaimers to this extent.

Clients and contractors alike do not routinely expect utility plans to show the path of services on domestic, industrial or derelict sites and rarely request them as a result. This is particularly common for areas under development despite the fact that live services may still be present and utility plans may show where they cross sites or mysteriously terminate at the boundary. Without attempting to obtain utility plans in these cases the contractor or client will not be discharging their duty of care in possibly the highest risk environment of all.

Maps and plans are supplemental to the use of appropriate cable and pipe locating technologies which all come with inherent weaknesses. In most instances the appropriate cable locating technology will be a basic Cable Avoidance Tool (CAT) to verify the accuracy of utility plans or detect the presence of services not indicated. However CATs will not detect plastic or earthenware pipes, cables with no load and in some cases three phase cables where the load is well balanced. At the other end of the scale there is Ground Probing Radar which is expensive and may not detect all ground anomalies such as small diameter low voltage supply cables. To determine the suitable technology, reference must be made to utility plans and the site engineer must have an understanding of the applicable equipment.

Safe digging can only take place if you know what to expect. As examples, the use of mechanical equipment is prohibited within certain distances of gas mains with the distance depending on the mains pressure. Additionally safe digging traditionally relied on noticing a change in geology to indicate utility presence but this may no longer be applicable with the increasing use of directional drilling for service installation. In both of these examples the risk can only be truly managed with reference to utility plans.

As a final point of note, it must be understood that the safe system of work will only be effective if staff on site are trained in all 4 aspects and supported in the decisions they make. The safe system of work should carry the sponsorship of a senior figure, as a clear demonstration of commitment to staff safety, and be accompanied by a documented procedure that can be followed and used as reference.

Management of Health and Safety at Work Regulations 1999 – Approved Code of Practice and guidance – L21 is available from HSE books priced £8.00

CDM2007 Approved Code of Practice known commonly as L144 is available from HSE books priced £15.00

HSG(47) ‘Avoiding Danger from Underground Services’ is available from HSE books ( priced £7.50

Tom Phillips
Applied Geology