Excavation Safety and the Role of the Competent Person
The Problem
Excavation work is essential in construction, but it comes with serious risks. Ground collapses, hazardous atmospheres, and utility strikes can lead to severe injury or death. Statistics show that trench collapses are among the most life-threatening hazards on a construction site. This is where the role of the Competent Person is critical—assessing site conditions, ensuring protective systems are in place, and helping keep everyone safe. Today, we’ll talk about common excavation hazards, the responsibilities of the Competent Person, and how everyone on-site plays a part in excavation safety.
Identify the Hazards
- Ground Collapse: The most dangerous excavation risk—often fatal if support systems are missing or fail.
- Hazardous Atmospheres: Excavations can contain toxic gases, fumes, or low oxygen levels, particularly in confined spaces.
- Underground Services: Striking electrical cables, gas pipes, or water mains can cause electrocution, gas leaks, or flooding.
- Unexpected Events: Rain, broken water lines, or nearby equipment movement can destabilise the ground, increasing risks.
Safety Practices and Preventative Measures
Soil and Site Assessment
- Carry out daily inspections of soil conditions and nearby risks to determine the appropriate protective measures—such as benching, sloping (battering), or shoring.
Protective Systems
- Ensure protective systems are installed correctly and are strong enough to prevent ground collapse.
- These systems must be maintained throughout the excavation process.
Inspections and Hazard Control
- Inspect the excavation daily, and after any event that could affect its stability (e.g., heavy rain or water leaks).
- Test for hazardous atmospheres and use ventilation where necessary to ensure a safe environment.
Authority to Stop Work
- The Competent Person has the authority to stop work and remove workers from the excavation if unsafe conditions are identified.
Responsibilities for All Workers
- Report Hazards: Immediately report loose shoring, water buildup, or any damage to support systems.
- Follow Safety Procedures: Always wear the correct PPE, stay out of restricted areas, and remain alert to changes in the work area.
Real-Life Case or Scenario
Incident Summary: Trench Collapse Fatality A construction crew began excavation work without installing proper trench protection. During the task, the ground gave way unexpectedly, causing a partial trench collapse. Tragically, one worker was fatally injured in the incident. It was later determined that the Competent Person responsible for excavation oversight was not actively monitoring the site that day. No daily inspection had been documented, and no protective systems (such as shoring, benching, or sloping) had been installed. Key Learnings: All excavations over 1.5 metres deep—or where collapse risk is present—must have adequate ground support in place before work begins. A Competent Person must inspect the trench daily and be present to monitor site safety. This fatality could have been prevented with proper trench protection and active oversight. Reminder: Trench safety is not optional. Always follow WorkSafe NZ guidelines and ensure a Competent Person is engaged before and during excavation.
Employee Responsibilities
- Carry out pre-start checks and follow all trench protection procedures.
- Report unsafe conditions to the Competent Person immediately.
- Stay out of unsupported trenches and obey all access restrictions.
Employer Responsibilities
- Appoint a trained Competent Person for all excavation work.
- Provide trench protection systems, gas detectors (where required), and suitable PPE.
- Deliver excavation safety training to ensure workers can identify and respond to site hazards effectively.
Discussion & Questions
- “What are some warning signs of an unsafe trench or excavation?”
- “Have you experienced an excavation hazard on-site? What happened, and how was it resolved?”
- “What can you do to support the Competent Person’s role in excavation safety?”
Encourage workers to share their experiences, raise questions, and offer suggestions. Peer learning and open dialogue help reinforce safe practices.
Commitment/Action Plan
Let’s commit to supporting our Competent Person and staying vigilant during all excavation work. Before we start today, we’ll review our trenches and trench protection systems. If anything looks unsafe — speak up. Your safety depends on it.
Wrap-Up
Excavation work is high-risk, but with strong planning, regular checks, and teamwork, we can avoid serious incidents.
Thanks for your time today—let’s prioritise safety and look out for one another.
Standards Overview
Under Canadian workplace health and safety legislation and CCOHS guidelines:
- A Competent Person must oversee excavation safety, including site assessments, hazard identification, and the implementation of control measures.
- Trench protection systems (benching, sloping, shoring, or trench boxes) are required for excavations deeper than 1.2 metres (4 feet) or where there is a risk of collapse, depending on provincial regulations.
- All workers must be trained to recognise excavation hazards and know how to respond appropriately.
Disclaimer
“The information provided in this toolbox talk is intended for informational and educational purposes only. It is not a substitute for professional legal, safety, or regulatory advice. The content reflects general best practices and industry standards but may not be applicable to all workplace environments or jurisdictions.
It is the responsibility of employers, supervisors, and workers to ensure compliance with applicable federal, provincial, and territorial laws, regulations, and standards, including but not limited to those set by the Canadian Centre for Occupational Health and Safety (CCOHS) and relevant provincial occupational health and safety authorities. Site App Pro, its affiliates, agents, or representatives—as well as the authors, presenters, and distributors of this toolbox talk—assume no liability for the use or application of the information provided.
Participants are strongly encouraged to consult appropriate legal, safety, or regulatory professionals regarding specific workplace concerns or questions. Always adhere to your organisation’s policies and procedures for health and safety and hazard management.
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