Excavation and Trench Safety Toolbox Talk
A trench can collapse with no warning, and a cubic metre of soil weighs as much as a small car. People caught in a collapse are often crushed or suffocated before anyone can dig them out. Never get into a trench that is not properly supported.
Takes about 7 minutes, plus a 5-question quiz.
Key points to read out
- Trenches 1.5 m deep or more must be shored, benched or battered unless a geotechnical engineer advises in writing that the sides are safe. Trenches deeper than 1.5 m are high risk construction work and need a SWMS.
- Shallow trenches kill too. A worker kneeling or bent over in a waist deep trench can be buried by one slab of the wall.
- A competent person inspects the excavation before each shift and after rain or any change.
- Shoring and trench boxes only work if they are installed the way they were designed. No missing struts, no gaps, and no digging below the bottom of the box beyond its rating.
- Keep spoil, materials and plant back from the edge, at least 1 m, more in loose ground.
- Check for underground services before digging. Never assume the plans are exact.
- Provide a safe way in and out, such as a ladder secured at the top, close to where people work.
- Never ride the bucket or climb the shoring to get in or out.
- Put barriers around the excavation so people and vehicles cannot fall in.
- Rain, water, vibration and nearby traffic weaken the walls. Watch for cracks, bulging and falling soil.
- Keep water out of the trench. Pump it out and do not work in a trench with water building up unless it has extra protection.
- Deep trenches can collect dangerous gases. Test the air if there is any doubt.
- If the trench starts to collapse, get out and stay out. Rescue only with proper support in place.
Questions to ask the crew
- How deep is our excavation today, and what support is in place?
- Who inspected it this morning?
- Where is the ladder or way out?
- What signs would tell you the walls are moving?
- What would we do if someone was buried, and who would we call?
Reference: WHS Regulations, Part 6.3 Division 3 (Excavation work, r.304 to 306)
How to run this talk
- Run the talk at the edge of the actual excavation, standing well back from the lip.
- Measure the depth together and agree what protection that depth needs.
- Point out the spoil pile, the ladder or ramp, and any cracks, water or vibration sources.
- Show the competent person's inspection record for today.
- Agree the emergency plan for a collapse and who calls for help.
- Record attendance, depth and protection on the sign-in sheet.
Excavation and Trench Safety quiz
Ask these after the talk. Answers are underneath each question.
At what depth does a trench need shoring, sloping or a trench box?
- Only when it is deeper than 3 m
- At 1.5 m or more, unless a geotechnical engineer advises in writing the sides are safe
- Only if it has rained
Answer: B. The WHS Regulations treat trenches over 1.5 m as high risk construction work that needs protection and a SWMS.
Where should you put the spoil from the trench?
- Right at the edge so it is easy to backfill
- Back from the edge, at least 1 m and more in loose ground
- In the trench itself
Answer: B. Spoil at the edge adds weight to the wall and can roll back in on workers.
It rained heavily overnight. What has to happen before anyone goes back in the trench?
- Nothing, it was inspected yesterday
- A competent person inspects it again
- Pump the water out and get in
Answer: B. Rain weakens trench walls, so a competent person must inspect after any event that could affect stability.
How should you get in and out of a trench?
- By a secured ladder or ramp close to where you work
- By riding the excavator bucket
- By climbing the shoring
Answer: A. You need to be able to get out fast if the walls start to move.
You see cracks forming along the top of the trench wall. What do you do?
- Keep working but faster
- Get everyone out, stay out and tell the competent person
- Put a plank against the wall
Answer: B. Cracks and bulging are warning signs of collapse, and a cubic metre of soil can weigh as much as a small car.
Questions about excavation and trench safety
How deep can a trench be before it needs shoring?
Under the WHS Regulations, trenches 1.5 m deep or more must be shored, benched or battered unless a geotechnical engineer advises in writing that the sides are safe, and a trench deeper than 1.5 m is high risk construction work that needs a SWMS. Shallower trenches still need the collapse risk managed.
How far back from a trench should spoil be kept?
Keep spoil, materials and plant far enough back that their weight does not load the trench wall, at least 1 m as a rule of thumb and more in loose ground. Check your site's excavation plan for the exact distance.
Who needs to inspect a trench and how often?
A competent person must inspect the excavation before each shift and after rain, vibration or anything else that could affect its stability. If they find a problem, nobody goes in until it is fixed.
What should you do if a trench collapses on someone?
Call 000 straight away and do not jump into an unprotected trench, because a second collapse often follows the first. Rescue only with proper support in place, and keep machines and people back from the edge.
Sign-in sheet
Print this page or download the sign-in sheet. Or run it in the app and the crew signs on the phone.
| Name | Company | Signature |
|---|---|---|
Get it signed
Run this talk in the app. The crew signs on your phone and you get a dated attendance record as a PDF.