Water Hazards in Excavations: Prevention and Protection
The Problem
Water in excavations can quickly turn a routine job into a high-risk situation. Whether it’s causing soil saturation and collapse, eroding trench walls, or creating drowning hazards, water poses serious threats. Ignoring these hazards can lead to injuries or fatalities. Today, we’ll look at how water affects excavations, what WorkSafe NZ requires, and how we can manage these risks effectively.
Identify the Hazards
- Soil Saturation: Water fills soil voids, making the soil heavier and more slippery, which increases the risk of rench wall failure.
- Erosion: Running or pooling water can undermine the excavation base, weakening structural stability.
- Softened Soil: Extended exposure to water softens soil, making it more likely to collapse under pressure.
- Drowning Hazard: Sudden accumulation (e.g., from a broken main or heavy rain) can lead to deep water in the excavation, posing a drowning risk.
Safety Practices and Preventative Measures
Avoid Entry
- Never enter an excavation with standing or incoming water until it has been inspected and cleared by the Competent Person.
Role of the Competent Person
- A Competent Person must assess water-related hazards and determine what controls are needed before entry is permitted.
Water Removal
- Use pumps or similar equipment to remove standing water.
- No work should proceed until the excavation is drained and deemed safe.
Shoring and Trench Shields
- Use shoring or trench shields to stabilise walls, especially when the ground is saturated with water.
Personal Flotation Devices (PFDs)
- If drowning is a possibility, workers may be required to wear PFDs and lifelines, as determined by the Competent Person.
Actions to Take
- Alert the Competent Person: Immediately report any signs of water ingress or accumulation.
- Stay out: Do not enter an excavation with water until it has been inspected and cleared.
Real-Life Case or Scenario
A crew noticed water pooling in an excavation but continued working without notifying the Competent Person. Hours later, the trench walls collapsed due to saturation, trapping a worker and prompting a full-scale rescue. This could have been avoided with proper water removal and evaluation beforehand.
Employee Responsibilities
- Watch for signs of water in or near excavations.
- Immediately report water accumulation to the Competent Person.
- Follow all instructions—never enter without clearance.
- Wear PPE such as PFDs if instructed to do so.
Employer Responsibilities
- Ensure a Competent Person evaluates any excavation with water present.
- Provide pumping equipment and trench protection systems (e.g., shields or shoring).
- Train workers on recognising water hazards and their role in reporting them.
Discussion & Questions
- “Has anyone experienced water-related hazards in or around excavations? What was the outcome?”
- “What more can we do on this site to prevent or control water hazards effectively?”
Encourage workers to share experiences and ask questions.
Commitment/Action Plan
Let’s commit to staying alert for water hazards and always notifying the Competent Person. Starting today, if you see any sign of water, don’t ignore it—report it. We will not enter water-filled excavations without clearance. Safety comes first.
Wrap-Up
Water may look harmless, but in an excavation, it becomes a serious risk. By recognising the signs, following the right procedures, and deferring to the Competent Person’s judgement, we can prevent incidents and keep the job on track. Thanks for prioritising safety on site.
Standards Overview
Under the Health and Safety at Work Act 2015 (HSWA), PCBUs must ensure:
- Excavation work is risk assessed and monitored by a Competent Person.
- Water hazards such as pooling, erosion, or saturation are identified and controlled.
- Workers are trained to understand the risks and respond appropriately.
Refer to WorkSafe NZ’s guidance on Excavation Safety, Managing Risks, and Working Around Water Hazards for more information.
Disclaimer
These toolbox talks are provided for informational and educational purposes only and are not a substitute for professional legal, health and safety, or regulatory advice.
The content reflects recognised best practices and general industry standards as at the date of publication. However, it may not be applicable to all workplace environments or specific operational contexts.
It is the responsibility of the Person Conducting a Business or Undertaking (PCBU), as well as officers, workers, and other duty holders under the Health and Safety at Work Act 2015 (HSWA), to ensure compliance with all relevant laws, regulations, and WorkSafe New Zealand guidance.
The authors, presenters, and distributors of this toolbox talk disclaim all liability for any loss, damage, or injury arising from the use or reliance on the information provided. Users should seek advice from a suitably qualified health and safety professional or legal advisor for guidance tailored to their specific circumstances.
Always follow your organisation’s policies, procedures, and safe work practices to manage risks and maintain a safe and healthy workplace.
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