Why do people keep entering Excavations?

Inspiration (and some content) for this article came from Joseph Hovanjec’s article below:

Introduction

Construction typically involves excavation into the ground. In a lot of cases, these excavations are deep, unstable and have significant risks associated with them. These can include:

• Collapse
• Falls from height
• Unknown/non-identified services
• Groundwater ingress
• Hazardous atmospheres

So, why do I keep seeing people entering excavations? And reading reports about trench collapse incidents? Because they do things like this:

Unacceptable Practice- Working in a deep, completely unsupported excavation the operative is highly vulnerable to any sudden ground collapse or materials/equipment falling into excavation. (courtesy - Joseph Hovanjec)

Incidents

There were two separate incidents in July 2021 in South Australia:

“On 6 July 2021, a worker was injured after a trench collapsed while removing earth around and under existing services to allow the installation of an electrical conduit.

The worker was engulfed up to waist high by the earth for approximately 30 minutes requiring emergency services to respond. The worker received serious injuries to his spine and internal organs.

A second incident occurred on 12 July 2021 when a worker was injured after a trench collapsed while using a jack hammer.

The worker was engulfed up to shoulder height by earth for approximately 30 minutes. The worker received injuries resulting in bruising and muscle strains.

According to SafeWork SA data, 40 files have been opened since 1 July 2021 associated with incidents involving excavation work.

Of the 40 files:

• 13 relate to exposure to open trenches
• 4 relate to inadequate shoring of trenches
• 3 relate to the collapse of trenches.

This is quite staggering. That data was collected over a period of only 26 days.

The other state regulators have similar stories.

I have a personal connection to someone who's friend died back in 2008 in a test pit collapse. He was a graduate geotechnical engineer. This was 13 years ago. I think that we are generally becoming safer at work in the construction industry, so it surprises me that trench collapse incidents are still occurring so frequently.

The Law

The Code of Practice for managing health and safety risks associated with excavation work is an approved code of practice under the Work Health and Safety Act. It requires an employer to carry out a risk assessment, identifying all significant hazards and setting out the control measures that will be in place before work begins.

What about the 1.5m rule?

If you can drown in 50mm of water, you can certainly die in a trench less than 1.5m deep. If you are bent down with your head near the floor, it only needs to be just above your head to cause significant injury. The below incident was borrowed from Joseph's article:

“A ground worker was working within a 1.0m trench only 0.6m wide and installing a drain at the bottom of this trench. To install the pipe he had to crouch down and physically prepare, inspect and connect a joint. At this point the trench collapsed and the worker was trapped. He was killed by just one cubic metre of displaced soil which weighed approximately 1500kg. The collapse was caused in part by heavy plant moving about 1m from the edge of the excavation and surcharging the soil that formed the face of the excavation.”

For these reasons it is not an acceptable practice to rely on the traditional 1.5m rule of thumb – the risks at each site must be assessed to ensure that appropriate control measures have been implemented.

So what should be done?

A brief summary of the steps that should be taken is detailed below:

• Do NOT enter any excavation without appropriate risk assessment and consideration of all the aspects below.
• Good geotechnical data. Soil types and strengths effect how stable excavations are
• Good groundwater data – groundwater ingress into an excavation is not your friend. It will increase instability.
• Use a shoring system
• Batter back the side slopes
• Bench the excavation
• Keep surcharges (stockpiles, vehicles etc.) away from excavation edges
• Obtain advice from a Geotechnical Professional.

Taken from the Code of Practice that shows some of the items detailed above.

Please, if it seems even a little 'off' - DO NOT ENTER.

So why do people still enter excavations?

Good question. I am not entirely sure. But I imagine its for one of the following reasons:

• The classic 'she'll be right mate' attitude. They have entered excavations like this one for the last 20 years and never had an incident.... Well. It only takes 1 incident to take your life...
• They are worried that they will get in trouble if they 'don't get the job done'. Or that it will take too long/cost too much money/delay the job etc. etc. NEVER feel like you have to do something that you think is unsafe. Its not worth it. Safety should be the number 1 priority.
• They are new and have never been in this situation and don't know any better. They need guidance, mentoring, training to do the right thing and work safely.
• They genuinely feel like it is safe. This might be true if it has been assessed, checked and approved by qualified people.

I am sure there are many more. I hope that I will start reading less and less reports of trench collapse incidents though.

My closing remark is just to think about your and other's safety and don't enter an excavation without first thinking about whether it could be unsafe. It doesn't matter how deep it is, how long you are going to be in there for, or anything else. What matters is whether it can collapse and kill you. That's it.

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