Chapter 2.4.7 – Excavations

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Purpose

The purpose of this procedure is to provide guidelines and information to effectively control risks associated with excavation and trenching.

Scope

This procedure applies to all workers of our company and visitors including contractors, volunteers, work experience students, trainees, apprentices and clients.

Policy Statement

Any excavation work should be considered as high-risk work. Our company conducts excavation work under the scope of it’s normal operations and requires the regular use of:

  • Risk Assessment
  • Hazard / Risks Factors Questionnaires
  • to mitigate any and all associated risks with excavation operations.

Risk Assessment

A risk assessment must be conducted prior to excavation or trenching work and suggested corrective actions Implemented through a Rectification Action Plan (RAP).

Always conduct a risk assessment before any controls are implemented and a risk assessment after the controls are implemented to ensure the risk has been reduced.

Underground Services

Before excavation work is carried out:

  • Excavations where there is a principal contractor (PC), the principal contractor for the construction work must:
  • find out what underground services exist (Ring 1100 – Dial Before You Dig is a useful service);
  • obtain relevant prescribed information about the service (location, type, depth and restrictions to be followed);
  • give the information to the relevant person to do excavation; and
  • record the information in writing.

The relevant person must:

  • consider the information supplied;
  • follow any reasonable restrictions; and
  • implement necessary control measures (permits, signage, traffic management).

Excavation, where there is no principle contractor, the relevant person for the company, must:

  • find out what underground services exist (Ring 1100 – Dial Before You Dig is a useful service);
  • obtain relevant information about the service (location, type, depth and restrictions to be followed);
  • ensure the information is considered in planning the work; and
  • record the information in writing.
  • give the information to relevant workers; and

The relevant person must:

  • consider the information supplied;
  • follow any reasonable instructions;
  • implement necessary control measures: and
  • any notifiable incidents relating to confined space activities must be reported to WHSQ as per legislative requirements.

Excavation and Trenches

If a person intends to do excavation work that could reduce the stability of a building, driveway, footpath, road or other routes, necessary controls measures are to be implemented to prevent collapse.

Trenches 1m Deep

Our company is responsible for managing the risks associated with:

  • an excavation collapsing;
  • a person being struck by an object falling into an excavation;
  • a person falling into an excavation; and
  • a person inhaling or being exposed to carbon monoxide from the plant.
  • Following a risk assessment, any control measures necessary to prevent risk from the collapse of another structure such as an adjoining building or road must be implemented.
  • To ensure public safety a barricade of at least 900 mm high must be erected around a trench that is 1 metre or deeper unless it is not practicable

Trenches 1.5m Deep

  • Our company must ensure that if a person is entering a trench more than 1.5 metres deep it: (one must apply)
  • has shoring or shielding; or
  • is benched – not higher than it is wide and no vertical face exceeding 1.5 metres; or
  • is battered – angle not exceeding 45° and bottom vertical face not exceeding 1.5 metres; or
  • is approved in writing by a geotechnical engineer as safe to work in.
  • Written approval to vary the benching and battering requirements may be obtained from a geotechnical engineer. The approval must be kept on site at all times;
  • Sheeting or timber may only be used if a competent person has inspected the trench, assessed and approved the shoring;
  • The excavation and trench has been checked to ascertain of it is a confined space;
  • Ladders used for access must be no more than 9m apart in the area of the trench where work will be carried out; and
  • No petrol-driven machinery in or near the trench.

Safe Work Method Statement

Safe Work Method Statements must be compiled when conducting construction work for high-risk activities such as a person entering trench more than 1.5m deep.

The safe work method statement must take into account the Principal Contractor’s WHS Management Plan and also state:

  • the high-risk construction activity;
  • the person’s ABN;
  • the control measures to be used;
  • the way the activity will be performed;
  • how the control measures will be monitored and reviewed; and
  • any relevant prescribed occupations.
  • Safe Work Method Statements must be easy to understand, and be signed and dated;
  • Safe Work Method Statements must be amended if there is a change in the activity and a copy must be given to the principal contractor. All persons affected by changes must be advised of amendments to the work method statement; and
  • Safe Work Method Statements must be readily available for inspection. It must also be reviewed and amended as required.

In the event of a collapse

  • Immediately contact Queensland Ambulance Service by mobile telephone (000) or via the depot by 2-way radio (or nearest Office if the Depot does not respond);
  • Try and locate the victim looking for signs such as tools or a shovel;
  • Clear all unwanted workers away from the area;
  • If possible, batter the sides of the trench in the collapsed area or insert shoring where possible to protect the victim 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 the victim;
  • Do not allow anyone on top of the collapsed soil as this will increase pressure on the victim;
  • If the trench is over 1.5m deep, rescuers are to wear safety harnesses and lifelines which extend to the surface;
  • When rescuers are near the victim, hands should be used to remove the soil if possible. If shovels have to be used, these are to be used with caution;
  • When the victim is located, clear soil from head and chest, and check for breathing and a pulse;
  • If breathing has stopped, start Expired Air Resuscitation (EAR). Where breathing has stopped and pulse is absent, start Cardio-Pulmonary Resuscitation (CPR);
  • Check for injuries and apply first aid where necessary;
  • Do not remove the victim unless there is a danger from flooding or dangerous gases are present or there is an imminent danger of further collapse;
  • Do not remove the victim by tying a rope around him/her and pulling on the rope; and
  • Where possible, leave the victim in the trench until the ambulance or a qualified medical person arrives.

Training

  • Specific job training should be completed for staff conducting trenching work and this may include confined space work;
  • Ongoing training or refresher training should be provided periodically to ensure that relevant staff are competent;
  • Staff are to be advised of the requirements of trenching including the safe work method statements through conducting a toolbox talk

Definitions 

Battering is where the wall of an excavation is sloped back to a predetermined angle.

Benching is the creation of stepped sides to an excavation, by forming a series of vertical and horizontal planes on either side of the excavation site.

Caisson means a structure that provides an underground passageway or passageway through the water.

Cofferdam means a temporary wall erected to exclude water from an area normally under water.

Competent person – A person is a competent person for section 210(5) for work in relation to a trench if the person and who has at least 3 years experience in stabilising excavations that are trenches and is either a geotechnical engineer or holds a qualification, or statement of attainment, from a registered training .

  • knowledge of relevant Australian Standards, relevant codes of practice and other relevant legislation;
  • knowledge of, and competence in, the following
  • hazard identification and risk assessment for trench stability;
  • measures to control exposure to risks from trench collapse;
  • safe work practices and procedures for installing control measures;
  • how to plan and prepare for working in a trench;
  • how to identify the location of underground services;
  • how to identify soil types and other factors that affect the stability of a trench.

Confined Space means an enclosed or partially enclosed space that:

  • is not designed or intended primarily to be occupied by a person; and
  • is, or is designed or intended to be, at normal atmospheric pressure while any person is in the space; and
  • is or is likely to be a risk to health and safety from
  • an atmosphere that does not have a safe oxygen level; or
  • contaminants, including airborne gases, vapours and dust, that may cause injury from fire or explosion; or
  • harmful concentrations of any airborne contaminants; or
  • engulfment, but does not include a mine shaft or the workings of a mine.

Excavation means a trench, tunnel or shaft, but does not include:

  • a mine; or
  • a water bore to which the Water Act 2000 applies; or
  • a trench for use as a place of interment.

Excavation work means work to make an excavation or fill or partly fill an excavation.

Geotechnical engineer means an engineer who holds an engineering qualification relevant to geo-technology.

Prescribed information about an underground service, means the information about the service necessary to safely do excavation work at or near the service including:

  • the location of the service;
  • the type of service;
  • the depth of the service;
  • for an electrical service – whether the service is or is not live; and
  • the restrictions to be followed in doing the work.

Shoring is a system of temporary supports and sheeting material used to maintain the stability of the sides of an excavation. Shoring may also be known as shielding.

Trench means a horizontal or inclined way or opening:

  • the length of which is greater than its width and greater than or equal to its depth; or
  • that commences at and extends below the surface of the ground; and
  • That is open to the surface along its length.

Underground service means a cable, pipe or other thing laid or installed underground for the transmission, transportation or storage of electricity or a substance.

Supervisor – a person involved in the management or control of a workplace (eg. supervisor, the person in charge or leading hand).