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AUS-6 Lift pit excavation hazards

Report ID: 821

Published: CROSS-AUS Newsletter 2 - July 2019

Report Overview

A reporter came across an unsafe deep excavation and asks how a geotechnical engineer views the risk of excavation collapse.

Report Content

The reporter took the attached photo of a worker standing close to the edge of a deep excavation.

The reporter notes that there are several issues/risks here:

  1. Worker safety from falling into the pit which may have had water and slurry in it.
  2. There was no immediate escape method visible (except perhaps via the excavator bucket?).
  3. Excavation side wall collapse.
  4. The stockpiles to the side are a potential risk although they were being moved at the time.

The controls for all of the above are or should be well known by builders. For example:

  1. Worker fall restraint could be achieved by harness systems or a walkway with handrails etc.
  2. An access ladder should be available.
  3. In NSW, the excavation code of practice requires that "Shoring, benching and/or battering may not be required if written advice is received from a geotechnical engineer that all sides of the trench are safe from collapse. Any 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."

The reporter would be interested to hear more from a geotechnical engineer on how they look at the risk of excavation collapse.

Comments

Despite much publicity about this issue, deaths from excavation collapses are all too common and may now lead to corporate manslaughter charges as has happened in the UK. In Australia, industrial manslaughter offences now exist in Queensland and the ACT.

The reporter draws attention to the NSW Excavation work code of practice - and other states and territories have similar codes that are based on the Safe Work Australia Code of Practice for Excavation Work.

All parties involved in construction work, including structural engineers, must address workplace health and safety issues and while any excavation is a hazard, the above codes of practice consider any excavation over 1.5m deep to be high risk and requiring control measures to prevent collapse unless a geotechnical engineer has advised otherwise.

This is also a design matter and clause 3.2 in the above code of practice sets out the responsibilities of designers, including “Designers of structures should consider possible excavation work methods and health and safety control measures when producing any final design documents and the safety report for the structure.”

As the reporter notes, it would be good to get feedback on how a geotechnical engineer would address the question of when control measures are not required. If you can provide feedback on this, or any other report, please submit feedback on the CROSS-AUS website.

 

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View other CROSS-AUS reports published in CROSS-AUS Newsletter 2

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Excavation hazards



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