Construction Methodology for Underground Services Protection

Purpose of below safety method statement is to provide instructions for ensuring the safe operations involved with ground penetrations so that underground services are not damaged and also to ensure the safety of workers.

Overall the project manager is having responsibilities for the implementation of this standard safety procedure.

Hazard Identification and Risk Assessment

a) The main dangers which may arise from work near underground services are summarized below.

The term “service(s)” means all underground electricity, gas, water, piped sewage and telecommunications.

b) Buried services are widespread and it should be assumed that they are present until it is proved otherwise.

The standards contained within this Instruction should be considered, and adopted as appropriate to the work in order to ensure that the risks are controlled and thereby a safe system of work exists.

c) Typical hazards could include:

i. Severe and potentially fatal burns.

ii. Direct electric shock.

iii. Injuries resulting from gas explosion and/or fire.

iv. Injury from a high pressure water jet.

Risk Checklist

The main risks which may arise from work near underground services, and could give rise to an injury are summarized below:

a) Electricity Cables

i. Penetration by a sharp object

ii. Severe crushing

b) Gas Pipes

i. Damage causing an immediate leak

ii. Damage causing a leak some time later

c) Water Pipes

i. Damage to a high pressure pipe

ii. A leak which washes away subsoil etc.

iii. Damage causing flooding

Control Measures for Underground Services Protection

Following control measures should be considered as appropriate in order to establish a safe system of work.

Before work begins obtain as much information as possible about buried services in the area and then use that information to ensure safe digging.

Utility Plans

Wherever possible obtain plans or other suitable information which show the line and depth of services.

When this is not possible, for example emergency work the excavation should be carried out as though there are buried services in the vicinity.

Be aware that plans may not be drawn to scale and should not be relied upon to obtain distances etc. due to:

• Reference points (e.g. the kerb line) may have changed
• Recording of surfaces and depths are incorrect
• The services being moved without the authority of the owners
• Services marked as straight lines may in practice “snake”

Take account of any indication that buried services exist i.e. presence of lamp posts, illuminated traffic signs, valve pit covers etc.

However the absence of such indicators does not necessarily mean that there are no buried services.

Responsibility remains with all responsible Managers/Areas to identify services.

Using Cable and Pipe Locating Devices

a) The position of any service in or near the proposed work area should be pinpointed as accurately as possible by means of a locating device.

This should be carried out in conjunction with the plan and/or other information.

b) Users of locating devices should receive sufficient and suitable training in its use and interpretation of results.

c) A locator may not be able to distinguish between cables or pipes running close together and may represent them as a single signal.

Having dug and found one cable or pipe care should be taken in case a further one exists in close proximity.

Frequent and repeated use should be made of locators during the course of the work.

d) Ensure the use of a locator which will respond to all the possible types of service including voltage levels.

e) Be aware that an increasing number of gas pipes are made of plastic and therefore it is especially important to use plans and safe digging practices.

f) Locating devices should be regularly checked (calibration) and maintained in good working order in accordance with the manufacturer’s instructions.

g) The position of the buried service should be indicated with fluorescent paint aerosols on paving or wooden pegs on grass or unsurfaced areas.

Safe Digging Practices

Before any excavation is done, an excavation permit is required from HSE department.

When services have been located excavation may proceed with trial holes dug using only hand tools to confirm the exact position of the buried service.

Special care should be taken when digging above or close to the assumed line of such a service.

Mechanical excavators or power tools (other than for breaking hard surfaces) where practicable should not be used within 0.5m of the indicated line of the service.

Every effort should be made to excavate alongside the service rather than directly above it.

Final exposure of the service should be by horizontal digging.

Spades and shovels should be used rather than other types of tools. They should not be thrown or spiked into the ground but eased in with gentle foot pressure.

When power tools have been used to break the surface away the service should then be positively located by careful hand digging.

If the service is not exposed then it should be assumed to be embedded within the paved surface.

The 0.5m safety margin may be reduced:

• Where congestion of buried cables renders it impracticable or;
• Surface obstructions limit the space available but only if the line of the service has been positively identified.

Power tools should never be used over the service unless:

• The service has already been exposed by digging under the surface to be broken out and it is a safe depth or;
• Physical precautions have been taken to prevent possible damage.

Services should not be used as a hand or foot hold.

Should an electrical cable be struck by a mechanical excavator, the driver should stay in the cab.

If the driver has to leave the cab he should jump clear and not climb down.

Identifying the Underground Services

Water pipes, electricity cables and telecommunications cables may be of black plastic.

If any black plastic is found it should be assumed to be a live electricity cable unless proved otherwise.

Similarly, cast iron and steel water pipes may look very much like gas pipes. If any such pipe is uncovered, it should be treated as a gas pipe.

Where there is any doubt about the identity of an exposed service it should treated as an electricity cable or gas pipe until proved otherwise.

Any wires not capped off must be accepted as Live Wires.

Permit to Excavate

A permit to excavate should be initiated by the health and safety department and issued to the persons or contractor company carrying out digging work requiring an excavation.

Random sampling will be carried out to monitor compliance.

Validity of Permit maximum one week cognizance is to be taking of daily inspections and sign offs in accordance with Permit to Work system.

Underground Service Safety Checklist

General

i. Has the HSE / Logistics departments been notified of the intended work?

ii. Have all requirements of the Excavation Permit been fulfilled?

iii. Is the work supervised by an appropriate qualified supervisor?

Plans

i. Are suitable and sufficient plans to hand from the authority, Electricity Company, Gas Company, Water Company as appropriate?

ii. Are employees able to read and interpret the plans and information? (Manager’s Responsibility)

iii. Has sufficient notice been taken of any other indications i.e. lamp standards, illuminated signs etc?

Location of Services

i. Is suitable equipment available?

ii. Has the locating device been adequately maintained?

iii. Have persons been trained in its use?

iv. Has the position of any service been adequately marked?

Safe Digging Checklist

i. Are trial holes being dug with hand tools?

ii. Are mechanical excavators being used at safe distances?

iii. Have any services been exposed firstly by hand digging?

iv. If appropriate, are services protected?

Relevant Records

Excavation Permits