There are many dangers to be aware of on construction jobsites — that’s why we talk about safety issues so often. But some activities are more dangerous than others, and excavation is one of them. Trenches in particular pose a huge danger to workers, since they are deep and narrow, and inadequate safety measures can lead to injury and even death. And in recent years, trench deaths have increased — 2016 saw 23 fatalities from trench collapses, more than in 2014 and 2015 combined. That’s why the National Utility Contractors Association (NUCA) hosts the Trench Safety Stand Down, now in its third year.
The danger of unprotected trenches
Trenches are dug to lay pipes or install utility lines underground. Because they can be deep, and are pretty narrow (no wider than 15 feet at the base), trenches are susceptible to collapse. And if anyone is in a trench when it collapses, the weight of the dirt or sand — a cubic foot of soil can weigh up to 140 pounds — can suffocate the person. Rescuing buried workers is also risky and dangerous — people can’t be dug out with machinery, but they need to be recovered quickly to avoid suffocating. OSHA’s oft-repeated mantra when it comes to trenches is, “An unprotected trench is an early grave.”
The Trench Safety Stand Down brings attention to the danger of working in unprotected trenches by encouraging construction firms to conduct toolbox talks and revamp their trench safety efforts. Everyone on-site should be aware of how to stay safe in and around trenches, just like everyone should be trained on your lockout/tagout procedure even if it’s not part of their average day.
How to prevent trench collapses
According to OSHA, the depth of the trench doesn’t really matter when it comes to safety — fatal collapses have occurred in trenches as shallow as three or four feet deep. That’s why on every jobsite where trench work is being performed, a competent person must be designated. The competent person does some important tasks:
- Conducts daily trench inspections before work begins
- Classifies soil types
- Designs structural ramps
- Inspects protective equipment
- Recognizes potential hazards before they cause damage
Classifying the soil type is important to assess the chances of a collapse — trenches in rock or clay likely won’t need the same protective systems as trenches in soil or sand. Excavations five feet deep or more need a protective system (unless it’s in stable rock); in trenches twenty feet deep or more, the system must be designed by a registered professional engineer. The competent person determines if a protective system is needed for a shallower (<5 feet) trench. There are a few different ways to protect trenches from collapse:
- Sloping the sides of the trench at a ratio of 1½:1
- Benching (see Figure V:2-15)
- Trench boxes or shields
- Call 811 to get underground utility lines marked before excavation begins.
- Don’t park heavy equipment near the edge of a trench.
- Set up warnings (barricades, hand signals, etc.) when machinery is working near a trench.
- Keep materials, including excavated soil (spoils) at least two feet from the edge of the trench.
- Provide a safe means of egress for workers in the trench, like ladders, stairs or ramps. Workers should not be more than 25 feet from an exit, so it may be necessary to provide more than one.
- Scale the face of the excavation to remove loose rocks or soil that could fall and hit workers, or otherwise prevent soil from falling.
- Require employees to stay clear of machines at work or that are being loaded or unloaded.
What if a trench collapses?
If there is a trench collapse on one of your jobsites and a worker is trapped, DO NOT attempt to rescue them. Many trench fatalities have occurred when one person jumped in to save another — call 911 immediately and again, do not attempt to rescue the person unless you have been trained on how to do so. If you’re hosting a toolbox talk this week, this is an important point to address.
Arguably the most important component of a safe jobsite is making your employees understand that accidents can happen to them. Although it can be tempting to take the shortcut, it’s not worth it if you end up buried in a collapsed trench. No one is immune to getting hurt — the only thing preventing injury and death is following safety procedures to the letter.
If you’re interested in participating in the 2018 Trench Safety Stand Down and receiving a flyer with your logo, contact NUCA at email@example.com. Provide your company name, state, logo and email address and NUCA will send you a flyer with your logo to display. As with every safety week you participate in, don’t think about trench safety just once a year — keep putting safety first every day.