Safe roads, reliable journeys, informed travellers
The Delivery Hub health, safety and environment
Raising the bar 9
Underground service avoidance
Issued July 2013 Revised January 2015
An executive agency for the Department for Transport
The delivery hub Health, safety and environment - raising the bar 9
Underground service avoidance - Issued July 2013 Revised January 2015
2
Contents
Objective
Page 3
Background
Page 3
Minimum requirement
Page 3
Risk assessment and planning
Page 3
Mark services
Page 5
Permits
Page 5
Cable avoidance tools
Page 6
Emergency arrangements
Page 7
Risks/controls
Page 7
Appendix 1 - CAT Calibration certificate
Page88
Page
Appendix 2 - Case study A46 tollbar critical stats protection
Page 9
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Underground service avoidance - Issued July 2013 Revised January 2015
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Objective
This raising the bar guidance aims to provide best practice for excavating in order
to prevent service strikes and the associated risk of harm.
This raising the bar guidance aims to provide best practice for locating, identification and working in the vicinity of underground services in order to prevent service
strikes and the associated risk of harm.
Background
Ensure that the risk assessment for the activity starts with considering if the hazards
associated with excavation and future maintenance can be eliminated. An example
of eliminating excavation at the design stage is locating longitudinal communications ducts in footpaths (Fig 1). The original design was to have separate longitudinal ducts and footpaths. The opportunity was identified to combine the two items to
bring efficiencies and cost savings. One managed motorway scheme was able to
apply this approach to 67 percent of their maintenance footpaths avoiding trenching
in rock, clashes with existing drainage or other services and providing footpaths for
future maintenance.
This area was chosen as a raising the bar topic as there have been repeated service strikes on project sites.
Minimum requirements
The expectation is that all the guidance contained within should be considered
minimum requirements.
Risk
assessment
and planning
Physically
mark
services
Permits
and cable
avoidance
Emergency
arrangements
Check and
review
Risk assessment and planning
Fig 1.
Prestart meetings with the statutory undertaker and supply chain should be held
prior to start on site to set expectations with regards to competency and working
standards. Agreement must also be reached with the utility owner what methods
and techniques can be utilised within the proximity of their asset.
Planning
The responsibility for works (who is principal contractor under construction, design
and management) should be clearly recorded for each element of the works as this
may change depending on the location of the works.
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When excavation is required, in the planning of a task, ensure that service drawings
are obtained and reviewed. It is essential that current drawings are used as new
services may have been laid as part of a project that would not be on plans issued
at the start of the contract. Method statements should include a hold point to
ensure that current updated drawings and a permit are in place prior to the ground
being broken.
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Underground service avoidance - Issued July 2013 Revised January 2015
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Under CDM REGS Clients responsibility is to ensure information is passed to the PC
so he may adequately plan his activities. Information on existing services can be
gained from statutory undertakers and
Highways Agency communications and national roads telecommunication
services (NRTS) drawings. Records from cable networks no longer in service such
as National Motorway communication system 1 (NMCS1) or old street lighting
should also be obtained. The Highways Agency use NRTS web site as a repository
for communication records drawings, however, users should be aware that there is
no guarantee that this web site includes all the old drawings. Statutory undertakers
offer services, such as dial before you dig, which should be used where available to
gain as much information as possible.
Service drawings may give an indication to the location of a service, however, the
accuracy can vary so if a service is shown, its location should be confirmed with a
hand dug trial hole. Once the service is located, in one trial hole the depth / offset
can vary significantly a very short distance away eg to avoid physical constraints so
multiple trial holes should be made on each service.
Be aware that when working in close proximity to services it is possible that they
may run through material that is to be removed, eg ducting that has been overlaid
with concrete. If not appropriately managed this can lead to services being
unintentionally removed with other items e.g. kerbs. Where possible services should
be isolated or items removed in small controlled quantities.
Before any works start, a site walkthrough must be undertaken by all persons who
will be involved in the operation.
Where no services are shown, conduct an onsite survey looking for:
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• Items that may have a power supply eg street lamps or gantries.
• Scarring or depressions in the road where there may have been a repair or new service laid.
• Manhole covers and frames, including hydrants and valves.
When hand digging, insulated tools must be used to protect the user from current
leakage or service strikes. Before starting any excavation ensure that edge
protection is available to immediate protect operatives and/or the public from falls
into the excavation. Where trial holes are undertaken and backfilled, take a photo
prior to backfilling and reference this in the method statement for the future works.
Individuals who work with services must be made aware of the types and coloured
ducting used for each service. This may be in induction or through service related
training. Personnel should also be aware of the dangers of poorly maintained
services that could conduct in water or leak hazardous substances.
Be aware that whilst the above should be followed, any type of service can be any
colour. Black and clay ducts, for example, are frequently found.
Utility
Colour
Utility
Colour
Electricity
Red
BT
Grey
Gas
Yellow
Data cables
Purple
Water main
Blue
Cable TV
Green
Sewer/drainage
Brown
Road lighting
Orange
Table A - service colours.
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Underground service avoidance - Issued July 2013 Revised January 2015
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Mark services
Where services are known, mark them on the ground, to make them clear to
anyone working in the vicinity, noting the need for better marking arrangements for
soft verges etc. They should be marked in the colour that relates to the service
(Table A). Do not mark services solely on the basis of the location shown on a
drawing as if the drawing is inaccurate, or reference points (eg kerb lines) may have
moved, this can lead to a false sense of security to the team excavating.
Mark liberally on as clean a ground as possible to minimise risk of erasure.
The location of services must be surveyed accurately (eg GPS line and level) to
avoid confusion if landmarks move. Information must then be transferred directly to
update the master stats drawings. Fig 3 shows a low pressure gas service marked
up in the road as shown on the utility drawings, however, the service was struck in
the footpath.
Permits
Before any activity is undertaken that breaks the surface of the ground a permit to
break ground / dig must be issued. The permit will ensure that competent and
authorised people conduct the task and that adequate consideration of the tasks
has been taken. The issue of the permit cannot by itself make the task safe.
Do not work beyond the scope of the permit, if anything changes you should stop,
re-issue and re-authorise for any additional scope of works.
In the raising of a permit the ground a trained cable avoidance tool operator must
scan the ground using a cable avoidance tool.
Personnel
p
Fig 2.
o
Fig 3.
Lifesaver
CONDUCTIVE METAL SETTING OUT PINS ARE BANNED ON
ALL HIGHWAYS AGENCY SITES
Conductive metal setting out pins are banned on Highways Agency sites.
Alternative means of marking could be non conductive pins, free standing
pins of carbon fibre, paint or marker flags. There are many products within
the industry and these alternatives should be used.
There are several people involved in creating a permit, the permit raiser will
gather information and write the permit. The authorised person shall check the
information is correct and the responsible person shall supervise the works at all
times and ensure the permit is closed once works are completed. Responsibilities
are detailed on following page.
Permit raisers:
• Review the service drawings
• Check the location
• Cat scan and mark the services on the ground
• Raise the permit and get it authorised
• Communicate the permit, make sure the responsible person understands it
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• Close out the permit on completion
Cable avoidance tools
• Look for evidence of services
There are a variety of cable avoidance tools on the market.
These can assist in the location of services.
• Open chambers and manhole covers to verify service routes
• Look for things that will need services - lighting columns, telecom boxes etc.
Permit authorisers:
• Check the services are clearly identified.
• Check the control measures can be fully implemented.
• Check the drawing clear and concise.
• Check the permit raiser had adequate time to raise the permit.
The cable avoidance tool can be used in a grid pattern
(Figure 4) in order to look for services or the Genny (Figure 5)
can be used to trace a service. Be aware cable avoidance tools
are not foolproof and are less likely to detect pot ends, services
without a live current (eg street lighting that is off) and when
there a multiple services one can mask another. Safety
fencing and cables that are no longer live further confuse
the situation. This is a support tool, and in no way a
definitive tool.
• Check the responsible person is clearly identified.
• Ensure that the permit is returned to the Permit raiser when the work is
completed or the Permit expires.
Permit responsible person:
• Talk with other responsible persons to ensure and share good practice.
• Ensure that all of the details, control measures or restrictions contained in the permit are strictly met.
• Supervise the operation throughout. If you have reason to leave the operation (even for a short duration) work must stop. Inform the authorised person, who will approve a suitable replacement.
• Stop if you encounter anything not indicated on the permit and inform the
authorised person.
• Check where hand digging is a requirement, that all engaged in the task have received formal instructions on safe hand digging techniques.
• Ensure that all necessary personnel are totally familiar with the contents, hazards and restrictions of the permit.
Figure 4: Typical CAT scan sweep.
• Ensure that any necessary instruction and supervision is provided.
Note: This can vary with the different manufacturer’s instructions.
• Ensure adequate inspections of any existing excavations affected by the work are in effect before work starts.
Genny’s should be used where possible to increase the likelihood of identifying the
service. Personnel should also be aware that services often weave and it is common
poor practice for loops of cable to be left in the ground, therefore identify the service
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Figure 5: Genny in use.
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Underground service avoidance - Issued July 2013 Revised January 2015
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in two locations may not mean that the service runs directly between the two points.
Colour coded permits
Cable avoidance tools must be calibrated by an authorised dealer. Personnel
should be aware that this service is unlikely to be offered by tool hire companies.
Consider use of colour coded permits to make it immediately clear if a permit is for
hand dig only or if they allow mechanical dig.
Any personnel using a CAT and Genny must have training on the specific model
that they are using.
Quick response codes can also prove useful in linking to the latest drawings and
contact details for service providers.
Emergency arrangements
Site emergency arrangements should detail contacts for service providers in the
event of a service strike and the action that site personnel are expected to take.
Personnel should be made aware that in the event of an injury, not to place themselves in danger when assisting others.
Risks/controls
Significant risks / controls (risks verses controls) items to be considered when
writing risk assessment / method statement.
Follow extraction and permit system.
Isolation of electrical equipment.
Striking buried services
Cable removal / spiking and cutting of any redundant
cables.
Consider avoiding digging
It is a minimum requirement to follow the hierarchy of control and eliminate
excavation where possible. There are many options for doing this which can be
found by typing ‘Underground Surveys’ into a popular internet search engine.
Vacuum extraction can be a useful method of extracting material without damaging
services. Suppliers of vacuum extraction equipment can be found by typing
‘vacuum extraction’ into a popular internet search engine. Please see Highways
Agency health and safety toolkit 346 air excavation.
The air pick (soil pick or air spade) is used when compacted ground conditions are
encountered. It is connected to a mobile compressor via an air hose. High speed air
is used to fracture and displace the hard material. Loose material is removed from
the trial hole with an insulated hand shovel. Manufacturer’s instructions should be
followed as methods of use can vary with model. When using the air pick full PPE
and impact resistant goggles must be worn at all times by all personnel within the
vicinity of the operation.
Falls into excavations
Before starting an excavation, ensure that there is
edge protection available for protecting the work area.
Vehicle movements
Ensure stop blocks are adequate to prevent vehicles
entering excavations.
Contaminated land
Soil testing to assess risk.
HAVS / noise from tools
Assessments to be in place including health
surveillance where necessary.
Consideration should be made to any additional risks introduced with use of this
equipment, for example, noise, vibration or scattering of material.
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Underground service avoidance - Issued July 2013 Revised January 2015
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Legislation
HSG47 Avoiding danger from underground services.
Health and Safety Executive case studies
http://www.hse.gov.uk/electricity/excavations/index.htm
Appendix 1 CAT Calibration certificate
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Underground service avoidance - Issued July 2013 Revised January 2015
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Appendix 2 - case study A46 tollbar critical stats protection
After a risk assessment exercise covering all aspects of the A45/A46 Tollbar
End project, it was acknowledged by the site team that the greatest risk to the
workforce on the project was the existence of underground services. While it was
acknowledged that all services posed a potential hazard, there were a number of
significant services including high voltage electricity, high pressure gas and water
mains, and multi way BT ducts that presented potentially fatal consequences. These
services were termed “Critical Stats”.
A policy and series of control measures were therefore developed to control work in
the vicinity of these services.
The aim of this approach was to raise awareness of the presence and location
of these STATs and work in a manner appropriate to the nature of these Critical
services, with all the necessary control measures in place.
This is carried out as follows
• Create Controlled zones around position of these services by use of cones and yellow rope clearly signed with the nature of the Critical STAT(s) in the
controlled zone
• Create clearly defined crossing points over these STATs to ensure that
protection from plant loading is controlled.
• Identify road crossing locations by use of ‘PK’ nails and discs at channel
lines on the existing roads.
Once the Critical STATs Zones were created, access into these areas to carry
out works is controlled by use of a ‘Critical STATs Zone’ permit issued by senior
members of the site team. These permits are only issued once it has been
demonstrated that the works will be carried out recognising the presence of the
critical service and all necessary control measures are in place.
This system has been very effective with no incidents recorded to date.
suppliers are available.
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The delivery hub Health, safety and environment - raising the bar 9
Underground service avoidance - Issued July 2013 Revised January 2015