Excavation work generally means work involving the removal of soil or rock from a workplace using tools, machinery or explosives to form a tunnel, an open face, hole, trench or cavity. The person conducting the business or undertaking (PCBU) is responsible for the overall management of excavation work (no matter how deep) they undertake.
PCBUs, employers and workers are to refer to the Excavation work - Code of Practice.
Risk management
You must manage risks to health and safety associated with a person including a member of the public.
Specific excavation hazards may include:
- falling into an excavation
- being struck by a falling object while working in an excavation
- ground collapse involving the fall or dislodgement of earth or rock
- instability of adjoining structures caused by the excavation
- underground essential services - including gas, water, sewerage, telecommunications, electricity, chemicals or refrigerant in pipes or lines.
- exposure to an airborne contaminant or a gas while working in an excavation.
Assessing hazards and risks
When assessing the risks associated with excavation work, consider:
- the nature of the excavation
- the nature of the excavation work, including the range of possible methods, tools and plant for carrying out the work
- the means of entry into and exit from the excavation
- previously disturbed or weakened ground
- previous backfill
- ground slope
- adjacent buildings and structures
- water courses (including underground) and trees
- the depth of the excavation
- the geotechnical engineer's report, including any information on:
- stability and safety of the trench excavation
- any shoring or trench support requirements
- the soil properties and ground conditions
- presence of ground water
- effect of exposure to the elements
- unauthorised access.
You must also have regard to all relevant matters, including the following:
- the nature of the excavation
- the nature of the excavation work, including the range of possible methods, tools and plant for carrying out the work
- the means of entry into and exit from the excavation.
High risk construction work
When undertaking excavation work, there are a number of high risk construction work activities that may be encountered, for example work that is carried out:
- in or near a shaft or trench with an excavated depth of greater than 1.5 metres or a tunnel
- on or near pressurised gas distribution mains or piping
- on or near energised electrical installations or services
- on, in or adjacent to a road, railway, shipping lane or other traffic corridor that is in use by traffic other than pedestrians
- in an area at a workplace in which there is any movement of powered mobile plant
A Safe Work Method Statement (SWMS) must be authorised before carrying out high risk construction work.
On a construction project, the principal contractor must have arrangements in place for the collection and any assessment, monitoring and review of the SWMS.
Hierarchy of control
Health and safety risks must be managed to eliminate the hazard. If this is not reasonably practicable, you must minimise the risk by one or a combination of the following in this order:
Engineering controls – examples of engineering control measures that minimise the risk of ground collapse include:
- Benching – this is a method of preventing collapse by excavating the sides of an excavation to create a series of steps to reduce the wall height of the excavation
- Battering – this is where the excavated face is cut back to a safe predetermined slope to ensure stability.
- Shoring – temporary support for trenches to prevent the movement of soil and therefore ground collapse. Shoring boxes and other trench support systems will protect workers who are between the shields of the shoring box from trench collapse. Shoring is a common method of ground support in trench excavation where unstable ground conditions, such as soft or wet ground including sand, silt or soft moist clay are often encountered. Types of shoring include hydraulic systems, steel sheet piling and steel trench sheeting.
Administrative controls – other risks must be minimised by implementing administrative controls. For example;
- implement and maintain a safe system of work for installing footings in a trench
- installing warning signs near the excavation
- establishing exclusion zones
Personal protective equipment (PPE) - any remaining risk must be minimised with suitable personal protective equipment. For example provision of:
- hard hats
- steel cap boots
- high visibility vests
Administrative control measures and PPE rely on human behaviour and supervision and used on their own are the least effective in minimising risks.
Trenches
Any trench of at least 1.5 metres deep must be, so far as is reasonably practicable, secured from unauthorised access, including inadvertent entry by members of the public. This is to minimise the risks to health and safety arising from unauthorised access, and the likelihood of unauthorised access, occurring to the work area.
The PCBU must also minimise the risk to any person arising from the collapse of the trench by ensuring that all sides of the trench are adequately supported at all times by doing one or more of the following:
- shoring by shielding or other comparable means
- benching
- battering
- where shoring, benching or battering of the trench is not carried out, a Geotechnical engineer must be engaged to assess the safety of the trench where persons are required to enter the trench. Any written advice should state the period of time to which it applies and may be subject to a condition that specified natural occurrences may create a risk of collapse.
Underground essential services
A PCBU must take all reasonable steps to obtain current underground essential services information relating to the part of the workplace where the excavation work is being carried out, and areas adjacent to it before directing or allowing the excavation to commence. This information must be provided to any person engaged to carry out excavation work.
'Underground essential services information' means:
- the essential services that may be affected
- the location, including the depth, of any pipes, cables or other plant associated with the affected essential services
- any conditions on the proposed excavation work.
Before You Dig
Before you Dig is the national referral service for information on underground infrastructure. It puts those who intend to excavate in touch with underground asset owners who are members of the Before You Dig service.
The asset owners respond by providing information (generally plans) on the location of any underground pipes and cables along with information on how to work safely and carefully while excavating in the vicinity of underground plant.
Underground essential services information - Transcript
NOTE: Before you Dig enquiries must be lodged online. If you need assistance with any Before You Dig service including lodging your enquiry online or establishing or accessing your online account, please call the National Help Desk on 1100 during business hours.
Locating underground utilities
Locating underground utilities is a vital process in avoiding a utility strike. This video explains how to look for visual clues, using cable locators and why potholing is a critical process.
Locating underground utilities - Transcript
*This animation is an outcome of an EU mandatory term