Digging a hole or trench without the proper training can be troublesome and dangerous, especially when it’s a large project. That’s why construction crews use a tool called trench boxes to secure the surrounding soil.
You might think these cage-like structures are designed to support the walls of the trench, but that’s not actually the case. They are meant to help protect workers inside the trench in the event of a cave-in.
Using a trench box is just one example of proper trenching and excavation safety protocols. What else can be done to improve the safety of workers during these projects? What are some necessary trenching and excavation safety tips everyone should know?
1. Review the Manufacturer’s Tabulated Data
The tabulated data of a trench box provides the specifications for the system, including the limitations of the build. For example, it will tell you the maximum depth a shield or box is rated for. It might also explain unique considerations when installing the box that you or your workers should be mindful of.
Start by reading the instruction manual and manufacturer resources. Before using a trench box on an active site, make sure you know the manufacturer’s tabulated data.
Moreover, site engineers can help improve trenching and excavation safety by aiding during preplanning, quality control, and workflow assurance phases, so don’t forget to include them in the initial processes. They can also confirm tabulated data and ensure guidelines are being followed.
2. Proper Tool Training
Trench boxes are one of the most important tools when excavating a site or digging a trench, regardless of size. But implementing them during a project may not be as straightforward as it seems, which calls for additional training. Even a minor mistake in the way the pit is built or the walls are supported can have disastrous effects. Construction crews sometimes take shortcuts to speed up a process or two, which could put their colleagues’ lives at risk.
The proper dimensions should always be preserved when installing the panels of a shield or trench box. For example, excavating underneath the box is not recommended, and the soil should be solid and stable. Just a single cubic yard of dirt can weigh close to 3,000 pounds, which would put a lot of pressure on the box and panels, let alone the human body.
A trench box or shield needs to be able to withhold potential soil or rock collapse and lots of pressure, keeping the danger at bay long enough for workers to climb out of the trench. It means the people working with these tools must know the ins and outs, with proper field training and plenty of experience before they’re able to do big jobs.
3. Label the Panels
Trench panels are meant to be put in a particular order when installing the shield. If you’re not paying attention, or you don’t know how to properly build the box, you might end up using panels in the wrong place. This can weaken the structural integrity of the box.
Ensure the panels are labeled appropriately and that everyone constructing the box understands where they belong. Critical to trenching and excavation safety is the proper use of the tools and resources, including a correctly built trench shield.
Another point of action is that the panels should never be placed directly against the spreader pipes. In a collapse, they will push against the end posts, but if they’re against the spreader pipes, it can cause the entire system to deflect.
4. Always Inspect the Paneling
Most trench shields come as panels, which are meant to be secured in place on the project site. Storing and maintaining these panels when they’re not in use is crucial to worksite safety. They should also be inspected before every use. Any structural damage should be repaired or dealt with accordingly, which may mean replacing panels or entire segments. During a disaster, that structural damage could mean the difference between protecting someone’s life or ending it.
That includes replacing damaged spreader pipes, box panels, fasteners, and other components. The spreader pipe can be bent or damaged, and it’s common to see when excavators lift or move the box.
5. Always Backfill Gaps
A trench box is always going to be wider than the excavation or trench, but once it’s in place, the outside soil should be flush with the edges, which often means backfilling any gaps. You’d think this might put added pressure on the panels of the box, but that’s the idea. They’re designed to restrict lateral or hazardous soil movements, so the extra soil will help stabilize the entire system.
That’s precisely why you’re not supposed to excavate below the box more than 2 feet. By removing that pressure and compromising the floor’s stability, you’re opening up the potential for a cave-in from below. Moreover, the trench box or shield should be rated for the full depth of the excavation site. Never use a box with shallow dimensions in a deep trench.
6. Mind the Top
Soil, rock, and clay are all relatively loose materials, so when you’re digging, they tend to fall or fly all over the place. You don’t want the top of the trench flush with the top of the trench box. You want to leave enough room for slippage and loose materials to get trapped outside of the box, rather than falling into it and harming workers.
Standard practice is to use a sloping design for the trench edges, with at least 18 inches of the trench box and panels above the lip of the trench. That way, any slippage gets trapped on the outside where the soil intersects the shield wall.
7. Follow OSHA Guidelines
When digging trenches or excavating a site that’s deeper than 20 feet, you’ll need a certified professional engineer on-site. You should also have access to an extensive overview of the soil depth and pressure of that particular site, including the contents of the soil you’ll be working with. This allows your team to vet the weights, widths, and internal dimensions as it pertains to the surrounding soil walls and select the proper trench box for the project.
Additionally, underground components must be located and avoided when digging, such as pipes and electrical lines. Certified lift equipment is also necessary, with trained personnel operating the machinery, to move and secure the trench box and the surrounding soil.
Clearly, there are detailed logistics surrounding the project before work is even underway, and many of these elements are covered or required by OSHA, which has some rigid trenching and excavation safety guidelines.
8. Keep It Empty
When the trench box is being placed inside the excavation site, or when it’s being installed, when it’s being disassembled, or even outside of work hours, it’s up to you and your teams to secure the site and keep it empty. No one should be going into the trench area during these times, and no one should be standing around the edges or near machinery.
Anyone inside the trench or excavation area could be struck by falling soil, objects, tools, and even the box or panels. It is imperative to remove everyone and relocate them while these events are taking place. It highlights, once again, the importance of following trenching and excavation safety guidelines to protect life and limb.
Build a Safety-Focused Culture
As long as you and your teams adhere to proper trench and excavation safety guidelines and complete your due diligence, the site will be safe for everyone. When you build a safety culture that includes proper tool training, experienced installers, support from the appropriately certified professionals, and proper handling, safety incidents become far less likely and everyone on the site can focus on productivity.
Emily Newton is the Editor-in-Chief of Revolutionized, a magazine exploring how innovations change our world.