Safe Work Method Statement & Risk Assessment for Excavation and Trenching

This safe work method statement SWMS details how specific risks associated with excavation, trenching and the location of underground services are to be managed and controlled.

It outlines the common risks and dangers associated with this work and how to best control them.

The control measures listed in this SWMS must be implemented on site.

The Key Safety messages provide a summary of the essential control measures.

If other hazards are identified that are not identified in this SWMS, a risk assessment for the new hazard must be completed.

Excavation Safety Method:

Do not assume you know where utility cables and pipes MIGHT be; you must contact underground service providers for prescribed information (DBYD – Dial Before You Dig).

Use all available methods to locate the services:

• Maps.
• Cable avoidance tool (CAT).
• Pot holing with hand tools, shovels and trowels. (Insulated if working near electrical services.)
• Use of Vac truck and/or locator by a location company.

Do not use the PLANT until you have the prescribed information from underground service providers (e.g. DBYD). Support and shield exposed services (seek advice from the service authority);

Mark all exposed / identified services with flags, devices or mark with paint that can be readily seen; ensure all marked services continue to be visible for the duration of the work.

When excavating, Employees (excepting the operator) MUST NOT be in physical contact with the excavating machine or equipment, in case it comes into contact with live electrical cables.

No one is to be in the excavation whilst any plant is in operation within the excavation.

Trenching Safe Method:

Assess the stability of the site, and document the findings.

Ensure that the trench sides aren’t loaded.

Keep spoil at least 1 m from the excavation.

Keep spoil piles to a minimum height.

Where trenches pose a risk to the public barricade the trench, only workers involved with the trench will be in the work area.

If there is an exposed gas main or fuel line, there must be continuous gas detection.

A Risk Assessment (Record of Excavation Inspection Form) must be completed whenever one of the following events occur:

– Before and during commencement of excavation.

– Excavation reaches a depth where there is a possibility of an injury

– Reaching a depth of 1 meter. – Reaching a depth of 1.5 meters.

– Change of expected excavation dimensions.

– Rain.

– Soil change.

– After every break.

At trench depths greater than 1.5 m, or where there is a risk of collapse, if a worker intends entering a trench, then at least one of the following measures MUST be implemented:

• Shoring or shielding (approved by competent person).
• Benching – not higher than it is wide and no vertical face exceeding 1.0 m.
• Battering – angle not exceeding 45° and bottom vertical face not exceeding 1 m.

Approval in writing by a geo-technical engineer must be obtained stating that the trench is safe to work in for trenches > 3 m deep. The approval must be kept on site at all times.

Use a ladder to enter and exit the trench. (Ladders must not be more than 9 m apart and at least 1 m of the ladder must extend out of the trench.)

No petrol or diesel driven machinery is to be used in or near the trench.

Ascertain if the excavation and trench is a confined space; if so refer to the Confined Space Entry method statement.

An emergency plan must be developed and rehearsed before work begins.

No one is to be in the excavation whilst any plant is in operation within the excavation.

Hazard Analysis & Control Measures

Activity: Planning of site, identification of underground services

Hazard: not identifying some underground services

Risk: Disconnecting a service, electrocution

Control Measures:

Prescribed information (DBYD) must be obtained prior to any excavation work commencing.

Don’t rely on DBYD! Always conduct a comprehensive site inspection to identify services that will be affected by proposed works and location of proposed works and any nearby services.

Consider all possible services such as phone and optical cables, water and sewerage, gas, electricity, storm water drainage, irrigation and indirect services, survey marks and street lighting electric cables.

Contact authorities for relevant information about the service (location, type, depth and restrictions to be followed) including maps etc.

Obtain all relevant prescribed information in writing and keep on site for the duration of the task.

The relevant person must consider the information supplied, follow any reasonable restrictions and implement the necessary control measures. The information shall be kept on site at all times.

Activity: Arrival at work site

Hazard: Vehicle Traffic, Manual handling, Obstructions
Risk: Struck by traffic, Slips, trips, falls, falling from heights

Control Measures: 

Assess site risks: The following activities must be completed before work starts each day and at other times as appropriate

• Pre-start Site Risk Assessment.
• ‘Record of Excavation Inspection’ form.
• Check the condition of any barricading.
• Ensure that all plant and equipment has been checked.

Determine the exclusion zones around plant and areas to be potholed.

Make sure workers on work sites are informed and acknowledge understanding of these exclusion zones.

Conduct a pre-start toolbox talk to ensure that all workers have been made fully aware of the scope of work to be performed.

Essential PPE for the task must be used:

• All authorised staff to wear safety helmets inside assessed machine exclusion zone at all times.
• Safety helmets must be worn in areas where there is a risk of a person suffering a head injury from falling, flying or moving objects.
• Steel cap safety boots.

Barricading the job site when a risk assessment identifies the need.

Activity: Locating the underground services / Excavating around the located services

Hazard: Gas lines, electricity

Risk: Contact with services, electrocution, explosion

Control Measures:

Carry out a detailed site inspection and review the site against prescribed information and plans.

Scan the site with a cable avoidance tool (CAT), if available.

Potholing, using hand tools must be conducted (insulated equipment must be used if working near electrical services).

Only use plant once you have identified where the relevant services are located (e.g. electricity, gas, telephone).

All onsite workers must be advised of the location of the services, in particular the operator(s) of any plant working on the work site.

Work parallel to any service(s) that is/are identified, use caution at all times.

A trained observer must be onsite at all times to assist the plant operator(s) to maintain sight of the service(s).

Support exposed services (seek advice from the service authority if required).

Mark all exposed services with flags or devices that can be readily seen.

Ensure all marked services continue to be visible for the duration of the work.

NO EMPLOYEES (apart from operator) are to be in physical contact with any excavating machine or plant at any time whilst it is operating. (Do not touch plant!)

Activity: Trenching

Hazard: loose soil, excavation, manual handling, solar radiation

Risk: Trench collapse, falling objects, Personal injury, Heat stress

Ensure trench sides aren’t loaded. Keep spoil at least 1 m from the excavation and keep spoil piles to a maximum of 600mm.

Continuous gas monitoring shall be required if working in the vicinity of known gas lines or near a high traffic flow area.

A Risk Assessment must be completed on the ‘Record of Excavation Inspection’ form, by a competent person when the trench or excavation reaches a depth of 1m and other occasions outlined on the form. Preventative actions must be taken if the risk assessment indicates there is a risk of collapse: eg.

a. Shoring or shielding (approved by competent person).

b. Benching – not higher than it is wide and no vertical face exceeding 1.0 metres.

c. Battering – angle not exceeding 45 and bottom vertical face not exceeding 1.0 metres.

Approval in writing by a geo-technical engineer must be obtained stating that the trench is safe to work in for trenches > 3 m deep. The approval must be kept on site at all times.

Use an industrial strength rated ladder to enter and exit the trench.

No petrol driven machinery is to be used in or near the trench.

All tools and equipment shall be placed so that they cannot fall into the trench or excavation.

Minimize the length of open trench by back-filling the trench or excavation as soon as possible.

Proximity of plant (including vehicles/trucks) to the top of the trench or excavation shall be determined through a risk assessment. The risk assessment should take into account the weight of the plant or vehicle involved as well as the type of soil and weather conditions.

Minimize plant and equipment movement near trench or excavations.

Ascertain if the excavation and/or trench is a confined space. If so, refer to the procedure for confined space entry.

Work only from inside shored areas or from on top of stable backfill.

All workers must constantly monitor the stability of the trench or excavation walls.

If a change of shift is required, the site supervisor will hold a handover meeting with incoming staff and supervisor to discuss the workplace and indicate any known hazards.

In the event of a collapse of a trench:

Immediately contact Emergency Services by telephone your supervisor and the H&S Team.

Try and locate the victim looking for signs such as tools or a shovel, but do not put yourself at risk.

Clear all unnecessary employees and others on work site away from the area.

If possible, batter the sides of the trench in the collapsed area or insert shoring where possible to protect victim(s) and rescuers.

Remove the collapsed soil with shovels, or if it is a very deep trench, with a machine.

If a machine is used, take extreme care to avoid further injury to a victim!

Do not allow anyone on top of the collapsed soil (this will increase the pressure on a victim).

If the excavation is over 1.5 m deep, rescuers must wear safety harnesses and life lines that extend to the surface.

When rescuers are near a victim, hands should be used to remove the soil if possible. If shovels have to be used, these must be used with extreme caution.

When a victim is located, clear soil from head and chest, and check for breathing and a pulse. If no signs of life are present, start Cardio-Pulmonary Resuscitation (CPR).

If a victim’s chin is pressed onto their chest, tilt the head back as soon as possible so as to open up the airway to the lungs. This can be done while other rescuers are freeing the soil from the upper part of their body and before starting CPR.

Check for injuries and apply first aid where necessary.

DO NOT attempt to remove a victim by tying a rope around him/her and pulling on the rope.

Where possible, once a victim has been freed from the soil, leave them in the trench until the ambulance or qualified medical person arrives. This minimizes unnecessary movement of the victim.