Working Near Underground Services

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Working Near Underground ServicesHealth and Safety Study Module

Module Ref: OPERC-SM-029

Working Near Underground Services OPERC-SM-029 (Version 2)

Working Near Underground Services Health and Safety Study Module (Ref: OPERC-SM-029)

© OPERC 2007

With the exception of research, private study or review, no part of this publication may be reproduced, stored or transmitted in any form, or by any means, without the prior written permission of the copyright owner. Applications for reproduction should be made to the publisher.

Version 1 July 2006 Version 2 August 2007

Published by: The Off-highway Plant and Equipment Research Centre (OPERC) PO Box 5039 Dudley West Midlands DY1 9FQ Email: [email protected] Tel: +44 (0) 1384 356202


Conditions of Use The material contained within this module represents general guidelines only and is not necessarily mandatory. The module does not replace any legal obligations upon employers (or employees) to provide (or undertake) basic health and safety training (or any other mandatory requirements, for example, under relevant health and safety legislation).

Every work setting provides a unique set of hazards and similarly, every person is unique in terms of cognitive ability, experiential knowledge and so on. For reasons such as these, this module must be accepted by the user solely as providing a basis for learning and nothing more. The module does not for example, expressly state (or imply) that any individual correctly answering the multiple choice self-test questions has achieved a particular level of health and safety knowledge or competence. Such must be appropriately measured via a formal mechanism; for example, by OPERC’s on-line ‘Safetynet’ health and safety test (http://www.operc.com/hstest/).

Every effort has been made to ensure that the contents of the module are correct, error free and representing best practice; but no guarantee is made express or implied that this is the case. It is also the user’s responsibility to ensure that this version of the module is current. Accordingly, the module is offered without legal liability or responsibility on the part of the authors, the publishers, the distributor or anyone else involved in its production.

Acknowledgements This lifelong learning resource was produced in close consultation with members of the Off-Highway Plant and Equipment Research Centre (OPERC). Special thanks are extended to A-Plant, Balfour Beatty Utilities, Cable Detection, Costain, Laing O’Rourke, Morgan Est, Shepherd, Skansa and Speedy Survey for providing invaluable support and/or technical guidance during the production phase.

Acknowledgement is also extended to Dr Gary D. Holt, Miss Philippa G. Spittle and Mr Geoff Tristram for their contribution to this document.

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Welcome to OPERC The Off-highway Plant and Equipment Research Centre (OPERC) is a non-political, non-profit making international centre of excellence for plant and equipment professionals. Its main objective is to advance off-highway plant and equipment knowledge and share this knowledge among all interested parties. Funds generated by the association are used to produce, publish and make available information (such as this training resource) that would otherwise be too time consuming and / or expensive for a single member to produce in isolation.

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The Lifelong Learning Zone OPERC’s lifelong learning resources provide an effective means with which to train employees, at all levels, on a wide range of basic health and safety subjects. This may be in the form of refresher training or as part of Continual Professional Development.

All resources are produced in modular format, with each one based upon a particular health and safety subject. They can be managed easily within a worker’s own workplace or used remotely (such as at home or elsewhere), thereby facilitating convenient access.

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Telephone: +44(0) 1384 356 202 Email: [email protected] URL: www.operc.com

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Contents

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Introduction

What are Underground Services?

How to Identify Underground Services

The Risks Presented by Underground Services

Health and Safety Legislation for Underground Services

Working Safely Near Underground Services

Answers to Multiple Choice Self-test Questions

Multiple Choice Self-test Questions

Summary

References

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Further Information



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This self-study health and safety module will introduce you to the subject of working near underground services. The term underground services describes the underground pipes, cables and other equipment used by industries which supply services such as water, gas, electricity and telecommunications.

Working near underground services can be very dangerous if correct precautions are not taken. Damage to the services, particularly in the case of electricity or gas, may result in fires or explosions which can lead to severe injury, or even fatality, to the worker(s) nearby. It can also lead to the loss of vital services, for example to hospitals or emergency services.

The subjects covered in this module will include:

q a definition of underground services and how to identify the various types that may be encountered;

q identification of the risks that underground services can present and how you may be affected by them;

q a brief discussion of some health and safety legislation that applies to working near underground services; and

q a description of some safe ways of working near to underground services that will help to minimise or remove the risks.

This means that upon completion of the module, you should:

q know how to look out for and identify the different types of service that may be hidden within the ground;

q recognise the risks of excavating, or otherwise working, near to underground services;

q have a basic appreciation of relevant health and safety law; and

q know how to work more safely near underground services (and therefore, know how to minimise your chance of being harmed by them).

If, having completed this module, you have any queries or concerns regarding underground services, or any other aspect of workplace safety, then you should raise these concerns with your supervisor, company safety officer or employer as soon as possible.

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Introduction


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Utility services, such as water, gas, electricity and telecommunications, are commonly installed and transported below ground level (underground services) and there are many advantages to be gained by doing this, which include:

q for reasons of safety – for example, to isolate the services from the general public;

q for visual reasons – for example, to place unsightly pipes, cables and associated equipment out of view; and

q to protect the services – such as from vandalism or from freezing conditions in the case of water services.

The description ‘underground service’ includes both:

q the mechanism by which the service is carried (such as the cable, pipe, conduit or duct); and

q any of its associated equipment (such as a junction box, branch, or siphon valve).

Table 1 provides a summary of the different underground services, with their usual carrying mechanisms and associated equipment.

Although such underground services are most likely to be found under roads and footpaths, they may potentially be present anywhere, so when excavating at, or below, ground level, it is always safest to assume that they are there. It has been stated that there are over 4 million km of pipes and cables buried underground within the UK, including:

q gas mains - 275,000 km;

q sewers - 353,000 km;

q water mains - 396,000 km;

q electrical cables - 482,000 km; and

q BT and telecommunications - 2,000,000 km [ref 1].

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Table 1. Typical underground services and their associated equipment

Service or ProviderTypical Service

MechanismTypical Associated Equipment

Gas Pipes

Valves, branches, service connections, telemetry cables, telecom masts, cathodic protection systems, pressure reduction equipment.

Electricity Cables

Ducts, joints, link disconnecting boxes, protective coverings, control cabinets, buried substation equipment, transformers, telemetry cables.

Water (supply) PipesDucts, valves, hydrants, vents, meter chambers, service connections and valves, telemetry cables and masts.

Water (collection) Pipes Pipes, drains, collection chambers, inspection chambers, rodding chambers.

Telecommunications CablesCable ducts, jointing chambers, control cabinets, telecom masts, access chambers.

Communications Cables (can be optical)

Ducts, chambers, amplification points, control cabinets, jointing and branch chambers.

Local Authority Various

Cables (e.g. street lighting, illuminated signage, traffic control equipment), pipes, chambers (e.g. highway drainage).

Fuel (e.g. oil) Pipelines Valves, junctions, cathodic protection systems that include cables.

Other Various

Multi-service or shared ducts, tunnels, traffic (e.g. sensing) equipment, information (e.g. highway) cables and equipment.

Source: Based on National Joint Utilities Group Guidance [ref 2]

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To work safely by underground services, you must be able to recognise or identify one kind of service from another once it has been uncovered.

To help with identification, ‘modern’ underground service installations should be in accordance with the colour coding system that was agreed between utility supply companies - see table 2. These service equipment colours may be of the pipe (for example, a yellow pipe for gas, a blue pipe for water) or of the ductwork that carries the service (for example, black ductwork for an electric cable). However, as we will see in the next section you should not automatically assume that all apparatus found follows these colour guidelines, particularly in the case of ‘older’ equipment.

Table 2. Colour coding system for underground services


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In some instances, a service pipe, duct or cable may be laid with an additional coloured polythene marker tape installed in the ground about 300 mm above it. The tape is placed in this way so that it will be uncovered in the event of future excavation and serve as a warning that a service is located beneath it. Most warning tape is yellow with a black legend; two exceptions are that for water services which is blue or blue/black and that for telecommunications services which may be of various colours.

Some warning tapes also contain a metallic tracer strip along their length, so that when laid above plastic pipes for example, their position can be identified by electronic (metal detecting) equipment. Example polythene marker tapes, for water and electric services respectively, are shown in Figure 1.

Service Description Colour

Gas Yellow ducts or pipes

Electricity Black or red ducts and cables

Water Blue or grey ducts; blue pipes

Sewer pipes Black ducts; various colour pipes

Telecommunications Grey, white, green, black or purple ducts; light grey or black cable

Street Lighting

England and Wales Black or orange ducts; black cables

Scotland Purple ducts and cables

Northern Ireland Orange ducts; black or orange cables


Figure 1. Examples of polythene marker tapes

Figure 2. Concrete marker tiles located above an electric cable

Similar to the use of marker tapes, electric cables in particular might also be covered with marker tiles or capping, which may be clay (older method) or concrete (more modern method)– see Figure 2. These give notice that a service is buried underneath them, but in the case of the concrete capping in particular, also offer some degree of physical protection from damage to the cable by excavating equipment.

(a) For a water service Because water mains are typically plastic, notice the metallic tracer wire enclosed along the middle of the tape.

(b) For an electricity service

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The Extent of the Risk

It has been suggested that each year in the UK more than four million holes are excavated in roads and footpaths to repair leaks in services, provide services to new properties and lay new cables and pipes [ref 3]. Excavating and working near underground services is therefore an extensive activity, so the health and safety risks are ever present and must be controlled.

Workers who have to carry out excavation work can potentially come across any, or all, of the various kinds of buried services and equipment and because they are usually laid within footpaths and roads, then workers who excavate on or near the highway are arguably at greatest risk from them. Note however, that this does not mean that other land, for example open land, will not have services buried within it. See Figure 3.

Always expect that services will be present, regardless of where you are excavating.

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Figure 3. Underground services are often found below open land!


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The Types of Risk

The different types of underground service can present very different types of risk to the workers excavating near to them. Table 3 lists the main types of service that are found buried in the ground, along with some of the most likely ways that they may become damaged and the most significant risks that might result from that damage.

Table 3. Types of service, potential for damage and main risks

Service Type Potential for Damage Main Risks

Electricity cables and associated equipment

q Penetration of the cable by a sharp object q Exposure of cable conductors resulting from abrasion q Crushing damage

q Electric shock q Explosion from arcing current q Fire as a result of explosion q Risk of secondary damage and / or additional risk (e.g. secondary explosion from simultaneous damage to gas service)

Gas supply pipes and associated equipment

q Penetration, abrasion or crushing etc., that allows gas to escape q Immediate gas leak, or damage that causes a leak at a later time

q Asphyxiation q Fire q Explosion q Travel of gas into a duct, chamber or other property (unseen explosive risk)

Water pipes and associated equipment

q Penetration, abrasion or crushing etc., that allows water to escape

q Injury from being struck by a high pressure water jet and / or physical objects such as stones or soil being carried within the water q Flooding and filling of excavations or confined spaces, drowning q Secondary risks from contact with other services e.g. electricity or contaminated substances

Drainage and sewerage systems

q Penetration, abrasion or crushing etc., that allows contents to escape

q Similar risks as for high pressure water, in pumped or pressurised sewerage systems q Contamination

Telecomms cables and associated equipment

q Damage to cables as for electricity q Damage to ducts carrying cables

q Direct personal risk normally low q Secondary risk of flammable or toxic gas entering damaged duct and travelling or accumulating elsewhere

Pipelines q Physical damage that allows contents to spill

q Risk dependent upon contents q Being struck (as for water) in the case of high pressure systems q Fire or explosion for flammable contents q Asphyxiation for gases q Poisoning for toxic contents

Source: Produced from HSE Guidance [ref 4]


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How Accidents Happen

Accidental Damage The risks listed in table 3 normally occur after physical contact has been made with a service, such as might result if an electric cable were struck by the bucket of a mechanical excavator or a water pipe were punctured with a pickaxe. Other kinds of damage to buried services may occur without excavation having to take place, for example, as a result of penetrating the ground with a gas sniffing bar or a road pin [ref 5].

A service might also become damaged if it moves under its own weight, such as could happen if soil is removed from beneath a steel pipe. Services that are buried in concrete carry similar risks because if the ground supporting the heavy concrete is removed or disturbed, then the concrete may move under its own weight and fracture the service within it, resulting in significant risks – especially if the service is an electric cable or a gas pipe of any kind.

Incorrect Identification Many accidents occur during excavation work as a result of a discovered service being wrongly identified and therefore, its real risks not being taken account of. For example, consider what the consequences might be if you assumed an exposed service was a ‘dead’ water supply pipe, and while trying to saw through it to remove it, found out it was a ‘live’ high-voltage supply cable.

Where there is any doubt about an exposed service, always consider it to be live.

Despite the usefulness of the colour coding system for identification of underground services, it should be remembered that:

q older services may not be colour coded in accordance with this ‘modern’ system;

q services may be wrongly housed in a duct or other covering that is incorrectly coloured for that particular service (e.g. consider an electric cable that is wrongly sheathed within a white telecommunications duct); and

q dirty service equipment and / or poor light conditions (e.g. during emergency work at night) may make services appear a different colour to what they actually are.

With regards to warning tape, tile or capping methods, remember that:

q these might have become disturbed within the ground over time and therefore not accurately indicate the presence of a service below them; and

q the absence of a warning tape or capping does not automatically mean that there is no service in the vicinity.

Never ‘assume’ anything about an underground service.


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There are several items of UK legislation which make provisions for protecting your health and safety at work with respect to working near underground services. Although you do not need to be concerned with all the detail of these, we will look briefly at some of the main laws and regulations as they place legal responsibilities on your employer, on you (as an operative working near underground services) and on the owners, or operators, of the underground services.

The Health and Safety at Work etc. Act 1974 (HASWA) sets out general health and safety responsibilities for all work activities, which will include work that is near to, and/or will expose, underground services. Your employer has a duty under HASWA to ensure, so far as is reasonably practicable, the health and safety of all employees and also anyone else who may be affected by the work activities (such as members of the public). This duty includes to:

q provide and maintain safe equipment and systems of work; and

q provide adequate information and training (e.g. on the risks of working near underground services and safe working practices).

As an employee, you also have legal duties under HASWA which include:

q to take reasonable care of your own health and safety and that of others who may be affected by your work;

q to co-operate with your employer on all health and safety matters; and

q to not interfere with, or misuse, anything provided for your health, safety and welfare.

The Management of Health and Safety at Work Regulations 1999 require your employer to carry out an adequate risk assessment for any proposed work activity. This is so that any hazards can be identified and appropriate controls put in place to remove or minimise the risks to people once the work is started. This is especially important when working near underground services, because this kind of work must be fully planned in advance due to the significant risks associated with it. Your employer has a duty to inform you of any significant risks associated with a work activity (identified for example, from the risk assessment) and to ensure that you are instructed on the principles of accident prevention.

5 Health & Safety Legislation for Underground Services

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The Provision and Use of Work Equipment Regulations 1998, as amended 2002, require your employer to prevent or control the risks to your health and safety from using equipment at work. The equipment should be (and in the context of underground services):

q suitable for the work task you have to do (e.g. for the proposed excavation work);

q safe to use and maintained adequately (e.g. well maintained and calibrated in the case of service detection equipment);

q used by you only if you have received adequate information and training; and

q accompanied by appropriate safety controls (such as safety guarding).

The Electricity at Work Regulations 1989 aim to control the risks arising from the use of electricity at work and place duties on both your employer and you to comply with them where it is under your control to do so. The regulations require that any work undertaken on, or near to, an electrical system, is carried out in such a way as to prevent risk of injury. This will therefore be applicable to work involving underground cables. They also require that work with or near live conductors should only take place when it is reasonable under the circumstances and if all suitable precautions are put in place to prevent injury.


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The Gas Safety (Management) Regulations 1996 aim to ensure that the distribution network for natural gas is safely managed at all times. They require a national telephone reporting system to be available 24 hours a day for the reporting of leaks. Reported gas escapes must be acted upon (e.g. inspected) by the conveyor as soon as reasonably practicable and stopped within 12 hours of their being reported. The Pipelines Safety Regulations 1996 are concerned with the safe design, construction, operation and maintenance of pipelines. They place general duties on the operators of pipelines with respect to this and also require that adequate arrangements are in place in the event of an incident or emergency relating to the pipeline. Additional duties are put on operators of those pipelines which are identified as being the most hazardous (Major Accident Hazard Pipelines [ref 6]), such as those carrying gas at a high pressure or containing certain dangerous fluids.

The regulations state that pipelines must not be damaged such that danger to persons may result, which includes to those having to excavate near this kind of underground service. To help prevent this, the operators of pipelines must make available information relating to the existence and position of their equipment, including therefore to anyone who has to carry out excavation work near it.

The New Roads and Street Works Act 1991 imposes duties on those who will have to undertake work in a road or a footpath. For example, such works must be carried out to certain standards of safety (e.g. with respect to lighting and signage) and quality (e.g. regarding reinstatement of excavations). The act applies to those who install, inspect or maintain services in the highway, but do not apply to road construction itself.

Undertakers of such work should give notice of the proposed work (there are some exceptions, such as emergency situations) and ensure that it is adequately planned, appropriately supervised and carried out by competent persons. For the purposes of the act, ‘competent’ is defined as workers being qualified according to the Street Works (Qualifications of Supervisors and Operatives) Regulations 1992.

The Traffic Management Act 2004, combined with its modification of the New Roads and Street Works Act, place a responsibility on utility companies to locate and record the position of all underground services in the UK by 2008. These location records will have to be available for inspection to all relevant parties if required (such as to anyone with authority to carry out street works).

(NB: Full bibliographic listings of the above legislation are given under Further Information at the end of the module).


qRisk assessment qSite preparation qWork procedures qPermit-to-work scheme

Plan the work before starting

qService location equipment qCable Avoidance Tool (CAT)qTrial holes

Confirm the exact location of underground services

qLocation plans qSite visit scheme qLocal knowledgeq Workplace features

Ask for information on underground services

qSafe working practices qTools and equipment qPersonal protective equipment qReinstatement and backfilling

Excavate using safe digging practices

Guidance for Safe Working: How to ‘PACE’ the Work

OPERC’s general advice for achieving safe working near to underground services is to always ‘PACE’ the work. That is:

P - Plan the work before starting;

A - Ask for information on buried service locations;

C - Confirm the exact location of buried services; and

E - Excavate using safe digging practices.

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Figure 4. PACE the work for safe working


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Plan The Work Before Starting

The best way to avoid or minimise risks in any work activity is to plan carefully before starting. Of utmost importance in planning for work near underground services is the accurate identification of the location of all underground service equipment, in order to avoid both damage to the equipment and injury to people. There will of course be some situations where time for planning will be limited, for example, when excavating to make an emergency repair on a service. However, even in such cases some form of planning must take place.

Your employer should carry out a suitable and sufficient risk assessment1 of the proposed work and based on the findings of that, design a plan of work that will remove or minimise any hazards identified. This might include doing things like:

q designing formal evacuation or emergency procedures;

q installing traffic management systems;

q ensuring protection of the public from the work; and

q placing earthwork support to excavations.

This is especially important in areas where mobile plant is to be operated. Any underground service, cavity or chamber could be damaged and/or cause a vehicle to overturn due to the loads imposed by mobile plant. It is good practice to visibly highlight the service at ground level but additional barriers/protection may also be needed to prevent damage to services, or vehicles from overturning.

The work can be further controlled by operating a ‘permit-to-work’ system2

procedure in any area where underground services are present. This is a system whereby the way that the work is to be carried out (the method), in what order it is to be done (the sequence) and who shall do it, is designed and formally recorded in advance of the work starting. The work must then be completed strictly in accordance with the conditions of the permit as a means of closely controlling it (particularly in terms of health and safety).

Ask for Information on Underground Service Locations

As far as possible, all the relevant owners and / or operators of services should be contacted to obtain reliable service location information, which is normally in the form of location plans. These plans should be clear to read and up-to-date and ideally show both the position and depth of the services and their associated equipment. However, plans should only be used as an indication of where the services may be found as they are not always accurate. This may be due to various reasons, such as

1For more detailed guidance on carrying out risk assessments and using their findings to design risk controls, see

OPERC self-study module SM-002 An Introduction to Health and Safety Risk Assessments. 2For more detailed guidance on permit-to-work systems, see OPERC self-study module SM-022

Safe Systems of Work.

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Personal or local knowledge of a particular site or area of land (for example, from the landowner), can help to establish the existence of any underground service equipment that might not otherwise be documented. Certain features of the workplace can also give indication as to where services might be located. Things to look out for include:

q street lighting (electric cables);

q highway lighting, illuminated signs and traffic control systems;

q inspection chamber covers;

q drainage access points and rodding eyes;

q roadside cabinets (as used by BT and other telecommunications providers); and

q roadside (verge) marker posts (these usually indicate the approximate distance from the post to a service – see Figure 5).

You should not assume, however, that services do not exist in an area, simply because features such as those listed above cannot be seen. Remember: always expect that services will be present, regardless of where you are excavating.

Figure 5. Marker posts to indicate location of underground services

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not having been drawn precisely to scale or the services having been marked on them in convenient straight lines (when in reality they will not follow such perfect straight lines in the ground!).

Most utility companies will also provide a site visit service to locate and mark the position of their equipment, such as is provided by the British Telecom in their ‘Dial Before You Dig’ scheme [ref 7]. This is especially useful where a service proves hard to detect, where it would be very difficult or expensive to repair if it was damaged (such as fibre-optic cables) or where it poses an extreme hazard (such as a high pressure gas or petroleum pipeline). The owner or operator of that service can help to confirm its exact location and may even remain on site (and monitor all excavations) throughout the duration of the work.


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Confirm the Exact Location of Underground Services

When it is not known whether services exist within the ground (for example, where accurate records do not exist or in the case of emergency excavation work) or when the exact locations of known services are being confirmed on site, then specialist service location equipment is used. Note that this equipment must only be operated by someone who is fully trained and competent in its use.

Some types of locating equipment that might be used include:

q hum detectors – to detect the magnetic field radiated from a live electricity cable;

q radio frequency detectors – for identifying metallic pipes and electricity cables;

q transmitter-receivers – where a generator induces a signal into a cable or pipe and a receiver detects it;

q metal detectors – which can identify most metallic objects hidden underground (not suitable therefore for detecting plastic services); and

q specialist ground penetrating radar systems – which build up a ‘picture’ of the substrate to help identify services or other objects such as buried tramlines etc.

One particular service locating device that combines many of the above features is a Cable Avoidance Tool (CAT); often used in conjunction with a signal generator. Together, these are often conveniently referred to on site as ‘Cat and Genny’.

The CAT can be used in one of two ways: passive mode or active mode. In passive mode, the CAT can either be used in a ‘power’ option, whereby it detects the electromagnetic signals automatically generated by those services that carry power, such as live electricity cables; or in ‘radio’ option, where it is set to detect metallic services that do not carry power (such as metal gas pipes).

In active mode, the CAT is used in conjunction with a separate generator, which can convey a signal into a service or a duct so that the CAT can detect it. Figure 6 shows a CAT being used in such a way, with the generator in the background of the picture sending a signal into the underground earth cable directly via a connecting lead. Figure 7 shows a generator sending a signal into a copper cored tracer rod that has been inserted down a hollow telecommunications duct, in order that the route of this plastic duct can be followed and marked on the surface of the ground.

Once the service locations have been identified by the equipment, they may be marked-up on the ground either by using (biodegradable) paint or other waterproof markings on the highway, or by using marker pegs and lines on softer or open ground. However, trial holes should still be dug, using hand tools only, to confirm the exact position of the services. This is particularly important for locating plastic pipes which may not have been found by the type of location device used.


Excavate Using Safe Digging Practices

Safe working practices should always be strictly followed when undertaking excavation work. These will include:

q excavating under permit control;

q taking extra care when it is known that digging is taking place near to a service;

q not using mechanical excavators or hand-held power tools near to underground services and following the appropriate advised specific guidelines on the safety margins from each type of service;

q hand-digging alongside a service and then exposing it from the side, rather than exposing it from above (mainly because greater control over hand tools can be made by working from the side in this way and the service is therefore less likely to be damaged);

q always assuming an exposed service is live until it is confirmed that it has been disconnected and it has been proven to be safe at the point of work; and

q never using exposed services as hand-holds, foot supports or for any other kind of physical support, such as to prop-up tools or equipment or as ‘steps’ for helping to climb out of an open excavation.

If a service is found encased in concrete then an alternative excavation route should be found or the service provider contacted to confirm that the service within the concrete is dead or has been isolated.

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Figure 6. CAT in use with generator directly connected to a service

Figure 7. Generator in use with tracer rod inserted Into a duct


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Special care should also be taken with the tools and equipment you use when hand-digging, including:

q using insulated tools, such as shovels with non-metallic shafts, to stop electricity travelling up them in the event of striking an electrical service (ask your supervisor about these kind of tools if in doubt);

q using flat-edged tools (such as spades or shovels) in preference to pointed tools (such as bars, picks and forks);

q not throwing or spiking any tool into the ground; and

q applying only gentle hand or foot pressure to a hand tool, when encouraging it to penetrate the soil that is being dug.

Specialist digging equipment is available that uses water or air pressure jet systems to loosen and dig into soil. Vacuum tools are also available for removal of excavated soil. However, the use of this type of equipment is somewhat limited, for example, its effectiveness is reduced in the case of very hard ground or in soil that contains a lot of stones and boulders. Nonetheless, it is a safer way of working in particularly hazardous excavations.

Appropriate personal protective clothing should be used at all times and your employer may, depending on your work, require that their work clothing be made only from certain (e.g. fireproof) materials. You should never work bare-chested as this will provide no protection in the case of an explosion or fire.

Once excavation work has been completed, then reinstatement and backfilling near to any service should also be done carefully, to maintain safe practices. This includes:

q working in accordance with any specific requirements of the service owner or operator (such as covering the service with a layer of sand before backfilling with soil – specific utilities will advise of any such requirements);

q backfilling carefully, for example, by not allowing large boulders to roll into the excavation or to fall against services; and

q by carefully reinstalling marker systems such as warning tape or tiles.

Guidance for Safe Working: Damage to a Service If a service does become damaged:

q stop work instantly;

q report the damage to a supervisor (who must then contact the appropriate authority straight away); and

q do not continue work until a person in authority deems the area safe and/or confirms that the service has been isolated or repaired.


3First aid is beyond the scope of this module, but general advice on the subject is given in OPERC module SM-030

First-aid at Work.

Guidance for Safe Working: Service-Specific

The following text provides some additional ‘service-specific’ safety advice for working near electricity cables, gas pipes and water pipes respectively, based on HSE Guidance [ref 4].

For Electrical Services and Associated Equipment

q Contact the service owner to enquire whether the service can be isolated. More so than other service types there is often a need to disconnect the supply and ‘make dead’ any service before work begins.

q Do not rely on marker or warning systems (tape, tiles, mesh) to confirm existence. No warning system does not automatically mean no service.

q Beware of coming across cables laid at shallow depths.

q Beware of cables hidden in ducts, pipes or concrete. Excavation next to cables in concrete should not be carried out without advice from the service owner and re- routing or making dead as appropriate.

q Some service equipment, such as cable joints, may need temporary support during excavation to avoid them becoming damaged.

For Gas Services and Associated Equipment

q Beware of shallow pipes and problems of plant running over them.

q Redundant iron gas services may have live modern plastic services inserted into them.

q The location of plastic gas pipes should always be confirmed by hand-dug trial holes before any mechanical excavation is carried out.

q Beware of ancillary equipment that may be attached to (and project from) pipes such as valve housings and siphons.

q Damage to an exposed pipe could also create unseen damage elsewhere, such as further up the (unexposed) pipe at a connection or junction.

q Pipe restraints or thrust blocks (etc.) should never be disturbed without advice from the service owner.

q Particular care is necessary if hot work (like welding) is to be carried out.

q In the case of a suspected leak, evacuate the area and report the leak on the National Gas emergency number: 0800 111 999.

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In the case of damage to gas pipes then this should be reported on the emergency telephone number dedicated to this purpose which is 0800 111 999.

In the case of a worker being injured it is helpful if colleagues have a basic understanding of first aid techniques3.


For Water Services and Associated Equipment

q Beware of shallow pipes and problems of plant running over them.

q Some service equipment may need temporary support during excavation to avoid them becoming damaged (larger diameter pipes full of water will be heavy and could fail under their own weight if ground support is removed).

q Pipe restraints or thrust blocks (etc.) should never be disturbed without advice from the service owner.

q Risk of exposed services freezing and rupturing in sub-zero weather conditions.

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7

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Summary


q The term underground services describes the pipes, cables and other associated equipment which carry utility services below ground level.

q The main underground services are electricity cables, gas supply pipes, water distribution pipes, sewer and drainage systems and telecommunications cables.

q Services are installed underground to protect them, keep them out of sight and most importantly to maintain safety, both of the services and the general public.

q Workers who have to carry out excavation work in the ground may come across many of these types of underground service.

q Underground services are frequently laid within the highway, but open land may also have services buried beneath it.


q To work safely by underground services, you must be able to recognise or identify the different types.

q A colour coding system is used on ‘modern’ services to help identify them. The main service colours are:

n electricity – black or red; n gas – yellow; n water – blue or grey; n telecommunications – grey, white, green, black or purple; and n street lighting – black, orange or purple.

q Coloured warning tape is sometimes laid in the ground about 300mm above the service to provide a warning for anyone excavating that the service is beneath it. Some tapes contain a metallic strip so that they can be identified by electronic equipment.

q Electric cables may be covered with a concrete (or clay) marker tile (or capping) to both warn of their presence and also provide some protection.


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q Working near underground services is widespread, as are the accompanying risks to health and safety, with many millions of holes being excavated every year.

q If you carry out excavation work in the ground you may come across any type of underground service. Most are laid within footpaths and roads, but they can be found anywhere, including open land.

q Always assume that underground services will be present, regardless of where you are excavating.

q Different types of service can present very different types of risk. The main ones are:

n electricity – electrocution, explosion, fire; n gas – explosion and fire; n water – being struck by high pressure jet, flooding and drowning; n sewerage systems – contamination; n telecommunications – gases in ductwork; and n pipelines – (depends on what is being carried in the pipe and its pressure).

q Accidents resulting in damage to a service normally happen through:

n physical contact when excavating, e.g. being struck by an excavator bucket or punctured by a pick-axe; n physical contact by other means than excavating, e.g. penetration by a gas sniffing bar or road pin’; and n the service moving under its own weight (e.g. if soil has been removed from under it).

q Many accidents occur as a result of a service being wrongly identified.

q Where there is any doubt about an exposed service, always assume that it is live - stop work immediately and seek guidance from a supervisor.

q Remember that older services may not be colour coded in accordance with the ‘modern’ system and some services may be wrongly housed in a duct or other covering that is incorrectly coloured.

q Warning tape, tile or capping may become disturbed over time and not accurately show where the service is to be found.

q Never assume anything about an underground service.


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Health and Safety Legislation for Underground Services

q The Health and Safety at Work etc. Act 1974 (HASWA) requires your employer to ensure, as far as is reasonably practicable, your health and safety and that of anyone else affected by the work activities. This includes providing and maintaining safe systems of work and providing adequate information and training.

q Under HASWA you also have legal duties to take reasonable care of your health and safety, cooperate with your employer on all health and safety issues and not interfere with, or misuse, anything provided for your health and safety.

q The Management of Health and Safety at Work Regulations 1999 requires your employer to undertake a risk assessment for each work activity to identify any hazards, take action to minimise the risks from the work and tell you about any significant risks found.

q The Provision and Use of Work Equipment Regulations 1998 require your employer to prevent or control the risks to your health and safety from using equipment at work. The equipment must be safe for use, suitable for the work you are doing and only used if you have had adequate training.

q The Electricity at Work Regulations 1989 require that any work undertaken on, or near to, an electrical system is carried out so that risk of injury is prevented.

q The Gas Safety (Management) Regulations 1996 require that the natural gas distribution network is managed safely and that there is a 24 hour telephone number available for reporting gas leaks.

q The Pipelines Safety Regulations 1996 require the operators of pipelines to ensure their safe design, construction, operation and maintenance.

q The New Roads and Street Works Act 1991 requires utility companies to give notice of planned work to a service on a road or footpath and ensure that it is carried out to the correct level of safety and quality.

q The Traffic Management Act 2004 requires utility companies to locate and record the position of all underground services in the UK by 2008 and to make these available, if required, to anyone with the authority to undertake street works.


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q OPERC’s general advice for achieving safe working near to underground services is to always ‘PACE’ the work. That is:

P - Plan the work before starting; A - Ask for information on buried service locations; C - Confirm the exact location of buried services; and E - Excavate using safe digging practices.

q Plan for work near underground services by identifying the location of all the service equipment located below ground level so that excavation work can avoid it.

q Good planning will include a risk assessment of the proposed work and control measures to remove, or minimise, any hazards found, such as creating emergency procedures or protecting the public from the work.

q A ‘Permit-to-work’ system involves the design and recording of how the work will be carried out and who will do it. The work must then be done strictly according to the permit conditions to ensure health and safety.

q Ask all relevant owners and / or operators of services, in advance of work starting, for service location information and plans, but remember that they may not show service connection cables and pipes from the main to a building.

q Looking around the workplace can help identify signs of where services are, such as drainage access points, street lighting or roadside marker points.

q Confirm the location of underground services, particularly when in doubt, by the use of specialist location equipment (which must only be operated by competent persons). Types of equipment include:

n hum detectors; n radio frequency detectors; n transmitter-receivers; n metal detectors; and n ground penetrating radar.

q The ‘Cable Avoidance Tool’ combines many features of the other location equipment and is often used with a signal generator (Cat and Genny).


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q Once identified, the location of the services should be marked-up on the ground by using either waterproof marking, such as paint, or by marker pegs and lines, where the ground is softer.

q The exact location of services should be confirmed by hand-digging trial holes.

q Excavate and dig using safe working practices such as:

n taking extra care when digging near to a service; n exposing a service by hand-digging alongside it rather than from above it; n assuming an exposed service is live until confirmed otherwise; and n never using exposed services as hand or foot supports, or as an aid to helping climb out of an excavation.

q Due to the increased risk, if services are found buried in concrete, then a different excavation route should be found or advice sought from the services provider to confirm that the service is dead or isolated.

q Take special care with tools and equipment; e.g., use insulated tools and flat- edged, rather than pointed, tools. Avoid throwing or spiking tools into the ground.

q Appropriate personal protective equipment (PPE) should always be used; this may sometimes include fireproof clothing.

q Backfilling should be done carefully to avoid damage to services and marker systems should be reinstated.

q For electrical services and associated equipment consider things such as:

n the need to disconnect the supply and ‘make dead’ before work begins; n cables laid at shallow depths or hidden in ducts, pipe or concrete; and n that there may be no marker or warning system.

q For gas services and associated equipment consider things such as:

n damage to shallow pipes, by plant running over them; n the importance of locating plastic pipes by hand-dug trial holes before using mechanical excavation; n damage to an exposed pipe causing unseen damage elsewhere; and n the dangers of hot work.

q For water services and associated equipment consider things such as:

n damage to shallow pipes, by plant running over them; n temporary support for heavy live water pipes, particularly larger diameter ones, so that they do not fail under their own weight; and n the risk of freezing and rupturing to exposed pipes in sub-zero weather.


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8 Multiple Choice Self-test Questions

Having completed this module, you might now wish to test what you have learned by answering these questions. Simply choose which answer you think is correct for each question below. The answers are given at the end of the module, but try the questions for yourself before looking!

When excavating in the ground, it is safest to:

A. Always assume that no services will be present.

B. Always assume that services will be present.

C. Ignore the risk of services in the ground, unless someone has told you they are there.

D. Never use a mechanical excavator.

Which of the following IS a direct risk, from penetrating an underground electric service cable, during excavation work?

A. Explosion.

B. Contamination.

C. Asphyxiation.

D. Drowning.

Which of the following IS a direct risk, from rupturing a high pressure water main, during excavation work?

A. Fire due to the main exploding.

B. Explosion due to the main catching fire.

C. Being hit by a high pressure jet of water.

D. Being hit by a bolt of arcing electricity, due to conductors touching each other within a cable.

Q3

Q2

Q1


If you came across a yellow service pipe in the ground, what would you expect it to be carrying?

A. Medium pressure water.

B. Electric cable.

C. High pressure oil or diesel.

D. Gas.

If you came across a blue service pipe in the ground, what would you expect it to be carrying?

A. Street lighting supply cable.

B. Electricity.

C. Water.

D. Medium pressure gas.

What colour are below-ground street lighting ducts in England or Wales?

A. Orange or Black.

B. Blue.

C. Yellow.

D. Purple.

Which of the following statements, regarding service location information, is correct?

A. Full use of reliable and sufficient service location information should be made at all times.

B. Service location information should only be used when service location equipment is unavailable.

C. Service location equipment need only be used for larger jobs.

D. Service location information is only used when the risk assessment has identified existence of electricity cables or gas pipes.

Q4

Q5

Q6

Q7

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Which of the following is NOT safe digging practice?

A. Exposing a service by digging alongside it, rather than exposing it by digging from above it.

B. Using tools with insulated shafts.

C. Always throwing or spiking tools into the ground after you have finished using them.

D. Using flat-edged tools in preference to pointed tools.

Why should a larger diameter water carrying service be supported if an excavation exposes it?

A. Because it might contain an electricity cable.

B. Because it might be damaged by plant running over it.

C. Because it will be heavy and may collapse and fail under its own weight.

D. Because the service owner or operator may make a surprise visit to site.

Q8

Q9


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9

Q1

Q2

Q3

Q4

Q5

Q6

Q7

Q8

Q9

B

A

C

D

C

A

A

C

C

Answers to Multiple Choice Self-test Questions


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References10

1 The Geospatial Location of Buried Services. A presentation given by James Brayshaw – Director Ordnance Survey. Available via the Institution of Civil Engineers website at: http://www.icenet.org.uk/knowledge/document_details.asp?Docu_id=1389&intPage=1&faculty=4 (viewed September 2007).

2 Guidelines on the Positioning and Colour Coding of Utilities’ Apparatus. National Joint Utilities Group. April 2003. ISBN: 0-9543641-1-2.

3 Mapping the Underworld: MTU and VISTA. ‘Mapping the Underworld’ and ‘ Visualising Integrated Information on Buried Assets to Reduce Streetworks’ research projects, accessible on Leeds University website at: http://www.comp.leeds.ac.uk/mtu/ (viewed September 2007).

4 Avoiding Danger from Underground Services. The Health and Safety Executive, document ref, HSG47. ISBN: 0-7176-1744-0.

5 Underground Cables. Working Near to Underground Services. Guidance provided by Central Networks. Accessed on Central Networks website at: http://www. eon-uk.com/distribution/607.aspx (viewed September 2007).

6 Third Party Damage to Major Accident Hazard Pipelines. Accessible on the Health and Safety Executive website at: http://www.hse.gov.uk/pipelines/ukopa.htm (viewed September 2007).

7 Network Protection. Dial Before You Dig. British Telecom service information, location and marking scheme. Accessible at: http://www.dialbeforeyoudig.com/ (viewed September 2007).


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Further Information

The Electricity at Work Regulations (1989). Statutory Instrument 1989 No. 635. ISBN: 0-11-096635-X. Accessible via the web at: http://www.opsi.gov.uk.

The Gas Safety (Management) Regulations (1996). Statutory Instrument 1996 No. 551. ISBN: 0-11-054184-7. Accessible via the web at: http://www.opsi.gov.uk.

The Health and Safety at Work etc. Act 1974. London: HMSO. ISBN: 0-1054-3774-3.

The Management of Health and Safety at Work Regulations (1999) as amended. Statutory Instrument 1999 No. 3242. ISBN: 0-11-085625-2. Accessible via the web at: http://www.opsi.gov.uk.

The New Roads and Street Works Act (1991). Accessible via the web at: http://www.opsi.gov.uk.

The Pipelines Safety Regulations (1996). Statutory Instrument 1996 No. 825. ISBN: 0-11-054373-4. Accessible via the web at: http://www.opsi.gov.uk.

The Provision and Use of Work Equipment Regulations (1998) as amended. Statutory instrument 1998 No. 2306. ISBN: 0-11-079599-7. Accessible via the web at: http://www.opsi.gov.uk.

The Street Works (Qualifications of Supervisors and Operatives) Regulations (1992). Statutory Instrument 1992 No. 1687. ISBN: 0-11-024687-X. Accessible via the web at: http://www.opsi.gov.uk.

The Traffic Management Act (2004). 2004 Chapter 18. ISBN: 0-10-541804-8. Accessible via the web at: http://www.opsi.gov.uk/acts/acts2004/20040018.htm (viewed April 2007).


Hand-arm Vibration OPERC-SM-009 (Version 3)

OPERC Off-highway Plant and Equipment Research Centre PO Box 5039 Dudley DY1 9FQ

Contact OPERC Tel: +44 (0)1384 356202 Fax: +44 (0)1384 356202 E-mail: [email protected] Web: www.operc.com

(OPERC) HEALTH AND SAFETY STUDY MODULE Module Ref: OPERC-SM-029

Documents

Working Near Underground Services