Cable Avoidance Training: CAT & Genny Guide to Safe Excavation

Before an excavator bucket, breaker, fence post or hand tool enters the ground, there is one question that needs answering:

What is underneath it?

Construction sites, roads, industrial premises and even apparently open ground can contain electricity cables, gas pipes, water mains, telecommunications cables and other buried services. Their exact position or depth should never simply be assumed.

That is why cable avoidance training is about much more than learning how to switch on a CAT scanner.

A competent operator needs to understand service plans, the different locating modes available, how a CAT and Genny work together, the limitations of locating equipment and how the information gathered fits into a safe system of excavation.

HSE’s HSG47 guidance identifies three basic elements of a safe system of work around underground services: planning the work, locating and identifying buried services, and safe excavation.

This guide explains those principles, how Cable Avoidance Tools work and what you should expect from professional CAT & Genny training.

If you already need training for yourself or your workforce, view our CAT & Genny Training Course for current course information, prices and Novice or Refresher training options.

What Is Cable Avoidance Training?

Cable avoidance training teaches people how to use underground-service locating equipment correctly and, just as importantly, understand its limitations.

It is relevant to far more people than excavator operators.

Groundworkers, plant operators, utilities workers, fencing contractors, landscapers, highways teams, supervisors and others involved with breaking ground can all encounter underground services.

Training should develop an understanding of:

• Underground-service hazards
• HSG47 guidance
• Service plans and their limitations
• Cable Avoidance Tools
• CAT scanner operating modes
• Signal generators or Gennys
• Systematic search techniques
• Identifying and tracing services
• Equipment limitations
• Marking located services
• Safe excavation principles
• Emergency procedures

The objective isn’t simply to obtain a certificate. It is to give candidates practical knowledge they can apply before excavation starts.

Why Is Cable Avoidance Training Important?

The consequences of damaging an underground service can be severe.

Electricity cables can cause electric shock, serious burns, arcing and potentially fatal injuries. Damage to gas services can create fire or explosion hazards, while water services can cause flooding and undermine excavations. Telecommunications strikes can disrupt important infrastructure.

The risks are very real.

In May 2026, a fencing contractor was fined after an employee suffered an electric shock and multiple burns when a breaker struck a live underground cable. HSE found that suitable and sufficient controls had not been implemented to prevent the risk from underground services.

HSE highlighted three basic elements of the safe system of work: planning, detecting and identifying underground services, and safe excavation.

For a more detailed look at what can happen when things go wrong, read our guide to the consequences of hitting buried cables.

What Is HSG47?

HSG47 – Avoiding Danger from Underground Services is Health and Safety Executive guidance for people involved in commissioning, planning, managing and carrying out work on or near underground services.

It explains three fundamental parts of safe excavation:

1. Planning the Work

Relevant information about underground services should be obtained and considered before excavation begins.

The work itself also needs to be planned around the nature of the job, services present, ground conditions and site constraints.

2. Locating and Identifying Buried Services

Plans provide useful information, but they do not remove the need to locate services on the ground.

Suitable locating equipment should be used by somebody competent to use it and understand its limitations.

3. Safe Excavation

Once services have been located, the excavation method needs to reflect the remaining risks.

HSG47 covers careful excavation, trial holes, use of hand tools, mechanical excavators and power tools, as well as what should happen if a service is damaged.

This is an important distinction:

CAT & Genny equipment is part of the safe system of work. It is not the entire safe system of work.

How Do CAT & Genny Cable Locators Work?

To use cable avoidance equipment effectively, you first need to understand what it is actually detecting.

A common misconception is that a Cable Avoidance Tool can somehow “see” every pipe or cable beneath the ground.

It can’t.

A CAT is designed to detect appropriate signals associated with underground services. Whether a particular service can be located depends on factors including the service itself, the signal available, the equipment, the locating method and site conditions.

This is why competent use involves more than walking across the work area holding a locator.

A typical cable avoidance system consists of two important components:

CAT – Cable Avoidance Tool / locator

Genny – Signal Generator

Understanding how they work individually and together is a central part of professional CAT & Genny training.

What Is a CAT Scanner?

The Cable Avoidance Tool, usually shortened to CAT, is the receiving or locating device.

Depending on the model, different operating modes allow the user to search for different types of signal.

Two of the commonly encountered passive locating modes are:

Power Mode

Power mode searches for signals associated with suitably loaded electricity cables.

However, the absence of a Power-mode response must never automatically be interpreted as proof that no electricity cable is present.

Radio Mode

Radio mode searches for radio-frequency signals that may be present on buried conductive services.

This can help identify services that are carrying a suitable signal even though they are not electricity cables.

Why Passive Modes Alone Aren’t Enough

The key word is passive.

The locator is searching for signals already present.

Not every underground service will produce a signal that can be detected in these modes. That is one reason why a systematic cable-avoidance survey can involve more than simply scanning in Power and Radio modes.

This is where the Genny becomes particularly important.

What Is a Genny or Signal Generator?

A Genny, or signal generator, is used to apply a detectable signal to a suitable underground service so its route can be traced with a compatible locator.

There are different ways of applying the signal depending on the service, equipment and circumstances.

Direct Connection

Where it is safe and appropriate, a transmitter can be connected to a suitable conductive service or accessible connection point.

This can provide a useful signal that allows the service to be traced.

Operators need to understand the correct equipment, connection method and safety precautions rather than simply attaching leads to whatever is accessible.

Induction

A signal can also be induced onto suitable services without making a direct electrical connection.

This can be useful where direct connection isn’t available, but induction also has limitations. Signals may couple onto other nearby conductive services, so results still need to be interpreted correctly.

Other Locating Methods and Accessories

Depending on the equipment and application, other accessories or techniques may be used to help locate particular services.

The important point is that no single CAT or Genny method should be treated as infallible.

Training needs to teach the operator what the equipment is telling them — and what it isn’t.

Can a CAT & Genny Find Every Underground Service?

No.

This is one of the most important things anybody using cable avoidance equipment needs to understand.

A locator doesn’t automatically identify every pipe, cable or duct buried beneath the work area.

For example, a non-conductive plastic pipe cannot normally be detected simply because the plastic pipe itself is present. Locating may instead depend on a suitable tracer wire, sonde or another method appropriate to the service.

Likewise, an electricity cable should not automatically be considered absent because it hasn’t produced the expected response in one particular locating mode.

Cable avoidance therefore requires a combination of information and techniques rather than dependence on one scan.

That includes:

Plans → Site Survey → Locating Equipment → Marking → Safe Excavation

What a Professional CAT & Genny Training Course Covers

A good cable avoidance course should be considerably more than a quick demonstration of the controls.

Candidates need to understand both the theory behind underground-service avoidance and how to apply that knowledge practically.

Vally Plant Training’s CAT & Genny Training Course covers the principles needed to use cable avoidance equipment safely and effectively.

Understanding Underground-Service Risks

Candidates need to recognise the hazards created by different underground services and why locating them before excavation is so important.

This includes electricity, gas, water and telecommunications infrastructure.

Understanding HSG47

Candidates should understand the relationship between cable locating and the wider safe system of work described by HSG47.

A CAT scanner doesn’t replace planning or safe digging.

Reading and Using Service Plans

Service plans can provide essential information about what may be beneath the work area.

But plans have limitations.

HSE’s guidance makes clear that plans should not be relied upon to establish exact positions or depths. Ground levels, reference points and service routes can change, which is why plans need to be considered alongside site investigation and locating.

Equipment Checks

Before use, operators should understand the appropriate checks for the equipment they have been provided.

Equipment condition, batteries, accessories and any applicable calibration or service requirements need to be considered in accordance with the manufacturer’s instructions and site procedures.

Search Techniques

Cable locating should be systematic rather than random.

Candidates learn how to survey an area using the appropriate equipment modes and techniques rather than simply walking directly along the route where they expect a service to be.

Using the Signal Generator

Training should cover the purpose of the Genny and appropriate methods of applying a signal.

Candidates also need to understand the limitations of each technique and how signals can affect interpretation of the survey.

Interpreting and Marking Results

Detecting a signal is only part of the process.

The operator needs to establish the indicated route as accurately as the equipment and conditions allow and ensure the information is clearly communicated to the people carrying out the excavation.

Equipment Limitations

This is one of the most important parts of CAT & Genny training.

Operators need to know circumstances in which equipment may fail to locate a service or produce a misleading indication.

In 2025, HSE served improvement notices following an 11kV underground power-cable strike. One of the identified failings was inadequate training in the use of Cable Avoidance Tools, including their methods of use, limitations and calibration. HSE also identified shortcomings in safe-digging training and obtaining underground cable information.

That provides a very practical reason why handing somebody a locator isn’t the same thing as ensuring they are competent to use it.

Cable Avoidance Training: Novice or Refresher?

At Vally Plant Training, CAT & Genny training is available through two routes: Novice and Refresher.

There is no Experienced Worker Test route for CAT & Genny.

Novice CAT & Genny Training

The Novice course is intended for candidates who require full training in the use of cable avoidance equipment and the principles of locating underground services.

It is suitable for people who are new to CAT & Genny equipment or who have been using it without sufficient formal training.

CAT & Genny Refresher Training

Refresher training is intended for previously trained candidates who need to update their knowledge and practical skills.

This can be particularly useful where equipment, site procedures or the candidate’s understanding needs refreshing.

Both Vally Plant Training routes are one day, with a maximum of six candidates.

For current prices and availability, see our CAT & Genny Training Course.

The Safe Digging Process: Following HSG47

Knowing how to use a CAT & Genny is important, but competent excavation requires those skills to sit within the wider safe system of work.

Stage 1: Plan the Work

Before excavation begins, obtain relevant information about underground services in the area.

The work should be assessed and planned, taking account of the excavation method, services likely to be present, ground conditions and site constraints.

The people carrying out the work need appropriate information and instructions.

Stage 2: Inspect the Work Area

Walk the area before scanning.

Look for indications of underground services such as covers, cabinets, marker posts, meter boxes, street lighting, previous excavation and service entries into buildings.

Compare what can be seen on the ground with the information provided on service plans.

If something doesn’t make sense, don’t simply assume the plan is correct.

Stage 3: Locate and Mark Services

Use suitable locating equipment systematically across the work area.

Where appropriate, use the Genny or other compatible locating methods rather than relying exclusively on passive modes.

Indicated service routes should be clearly marked and communicated to the excavation team.

Stage 4: Positively Locate Services Where Necessary

A mark on the ground still doesn’t mean the exact position and depth of a service have been physically confirmed.

HSG47 advises that trial holes using suitable hand tools or vacuum excavation may be needed to confirm the position of detected services.

This is an important stage before mechanical excavation takes place close to a service.

Stage 5: Excavate Safely

Mechanical excavation needs to be carefully planned and managed.

HSG47 says another person should assist an excavator driver from a safe position where they can see into the excavation and warn the driver about services or other obstacles.

Hand tools aren’t automatically safe either. HSE specifically notes that hand tools are a common source of accidents when used incorrectly.

The excavation technique should therefore reflect the actual service, site conditions and safe system of work.

Stage 6: Protect Exposed Services

Once a service has been exposed, it needs to be protected from damage while work continues.

The excavation should also be backfilled appropriately so that underground services remain supported and protected.

How Close Can You Dig to an Underground Cable?

There isn’t one universal distance that can safely be applied to every underground service and every excavation.

The safe method depends on factors including:

• Type of service
• Indicated and confirmed position
• Excavation method
• Ground conditions
• Surface construction
• Available working space
• Equipment being used
• Site-specific risk assessment and method

HSG47 does give specific advice for particular circumstances.

For example, where practicable, hand-held power tools used to break hard surfaces should normally be kept 500 mm or more away from the indicated line of a buried service, followed by careful excavation to positively locate the service. HSG47 also explains circumstances where this margin may be reduced with additional controls.

That is very different from saying there is a universal “500 mm rule” for every type of excavation.

Competent operators need to understand the distinction.

What Should You Do If an Excavator Hits an Underground Cable?

This is something every excavator operator working around underground services should understand before excavation begins.

If an excavator strikes an electricity cable, HSG47 instructs the driver to stay in the cab.

Climbing down could expose the operator to electrocution.

The affected area should be isolated and secured, and nobody should approach the excavator or cable until the cable owner has made the damaged cable safe.

The appropriate site emergency procedure should then be followed.

Different types of service strikes can require different responses, which is another reason why emergency arrangements should form part of the planning process rather than being improvised after an incident.

Who Should Take CAT & Genny Training?

Cable avoidance training is relevant to anybody who may be responsible for locating underground services or whose work involves disturbing the ground.

That can include:

• Groundworkers
• 360 excavator operators
• Utilities workers
• Fencing contractors
• Landscapers
• Drainage teams
• Highway workers
• Site engineers
• Supervisors
• Site managers
• Construction workers involved in excavation

Employers should consider the person’s actual responsibilities rather than simply their job title.

Someone doesn’t need to operate an excavator to be exposed to underground-service risk.

Is Cable Avoidance Training a Legal Requirement?

There isn’t a piece of legislation simply stating that every worker must hold a particular “CAT & Genny certificate”.

The legal position is broader.

Employers have duties to protect workers and others from risks created by work activities, while the Construction (Design and Management) Regulations 2015 contain requirements relevant to construction work involving underground services.

HSG47 provides practical guidance on controlling those risks.

Importantly, HSE says people exposing underground services and those supervising them should be competent and have sufficient information, instruction and training to understand the risks, use detection tools and practise safe excavation techniques.

The focus therefore needs to be on competence, rather than assuming possession of a certificate alone makes excavation safe.

NPORS CAT & Genny Training

For employers and operators wanting recognised training, Vally Plant Training provides NPORS CAT & Genny / Cable Avoidance Training.

Training with an NPORS Accredited Training Provider provides a structured route for candidates who require recognised training and assessment.

Depending on the certification route selected, successful candidates can receive the appropriate NPORS certification/card.

It is important, however, not to confuse certification with permanent competence.

Operators still need to use the equipment correctly, follow site procedures, understand the limitations of their locator and maintain their knowledge over time.

In-House CAT & Genny Training

For some employers, in-house CAT & Genny training and certification may also be appropriate.

This can provide evidence that employees have received training and assessment for the equipment and work they undertake within the organisation.

However, an in-house certificate is not equivalent to an NPORS operator card.

Acceptance depends on the employer, client, site, principal contractor or insurer. Where workers need independently recognised certification for different sites or employers, the NPORS route may be more appropriate.

If you’re unsure which certification route your workforce requires, speak to Vally Plant Training before booking.

CAT & Genny Training at Your Site or in Tewkesbury

Vally Plant Training provides CAT & Genny training for individuals and businesses.

For employers, training can be delivered on-site nationwide, subject to suitable facilities, equipment and a safe area for the practical elements.

This is particularly useful for businesses wanting several employees trained together using equipment relevant to their normal work.

Individuals and businesses can also attend training at our centre at Newton Farm, Ashchurch, Tewkesbury, Gloucestershire, GL20 7BE.

Our centre is approximately five minutes from M5 Junction 9 and around a five-minute walk from Ashchurch for Tewkesbury railway station.

To discuss availability, call 01684 297167 or view our CAT & Genny Training Course.

Why Choose Vally Plant Training?

Vally Plant Training is a family-run NPORS Accredited Training Provider, established in 2014.

We provide plant operator, lifting and safety training directly to individuals and businesses rather than operating as a training broker.

Our CAT & Genny courses focus on practical understanding — not simply passing an assessment.

Candidates need to understand why different locating methods are used, what their equipment can detect, what it may miss, and how the results fit into the wider excavation process.

For employers, we can also deliver training at suitable customer sites nationwide, helping reduce workforce downtime where several candidates require training.

Cable Avoidance Training: The Most Important Lesson

A CAT scanner should never be treated as a magic device that proves an excavation is safe.

Likewise, a utility plan isn’t an exact underground map, and hand digging isn’t automatically risk-free.

Safe excavation comes from combining the right information, competent people and suitable working methods:

Plan the work.

Locate and identify the services.

Excavate safely.

Those are the principles at the heart of HSG47, and they are the principles that should sit behind professional CAT & Genny training.

If you or your workforce need practical training, view our CAT & Genny Training Course for current prices, course dates and Novice or Refresher options.