In our industry, trench safety is something often discussed but just as often ignored. It's actually both the most dangerous part of our job and the most often cited OSHA violation. In the interest of moving the project ahead, precautions may not be taken that should be, and that can cause injury or death. At Team EJP, we take excavation safety very seriously. Though the OSHA standard can be a bit weighty to dig through, we've taken the time to draw up some basics that will help you through most excavations.
The OSHA standard pertaining to excavated trench safety is in 1926 sub part P. It includes soil classifications, where to place shoring members, using non-structural sheathing and the bending strength of plywood. But for the most part, what you need to know falls within some fairly straightforward parts of the standard. You should always have a competent person on site, and make sure you test the trench with a gas detector if there is a possibility of atmospheric hazards. Here are a few more to keep in mind on the work site:
- If the trench you're working in is 4' or more in depth, you need to have stairs, ramps or a ladder. If you do use a ladder, you need to have it located within 25' of travel and it should extend at least 3' above the grade to allow for handholds while climbing out.
- When you're working in a trench that is 5' or more in depth, you'll need to use a protective system that keep the sides of the excavation from collapsing. Typically, in waterworks, this is accomplished by using trench box. The box top will need to be above normal grade. Other options include sloping the sides sufficiently, benching the grade or using planking or hydraulic jacks to shore the trench. If you slope your trench, the trench box needs to be 18” above bottom of trench slope.
- If you do decide to use a trench box, keep in mind that the box can be blocked 2’ from the bottom of the trench. All 4 sides of trench box need to be closed in. The trench should be just big enough to allow for the trench box to fit. There shouldn’t be enough room between the trench box and trench wall for a person to fall and get trapped in between.
- If you decide to use a slope to prevent the ground from going into a distress form where it can collapse, you'll need to slope the ground anywhere from 90° for solid rock through the different grades of soil classifications to 34º for type C soils, 1-1/2’ to 1’ as a guide for type C only. When sloping with type C soils the top width should be 3x the depth plus the width of the bottom. Ex. If the depth is 5’ and the bottom width is 4’, top width should be 19’
- Keep it dry. Inside the trench, you can't allow any water to accumulate. Why? Wet soil is less resistant to distressing, creating a potentially dangerous collapse situation.
- Does your work site have any surface encumbrances? If there are any that could create a hazard must be supported or removed to prevent accidents.
- Going deep? For trenches at or over 20' in depth, a registered professional engineer must be employed to design the protective systems.
- Don't dump that dirt just anywhere! We've all seen poor job sites where the dirt that was dug out is back in the trench following a rain storm. OSHA regulations specify that the spoil pile needs to be a minimum of 2’ away from the edge of the trench.
By keeping these specific issues in mind, your work site should be in great shape. Whether it's avoiding a violation or ensuring worker safety, following OSHA's standard helps keep your work site running smoothly and efficiently while preventing serious accidents. At Team EJP, we're all about getting the job done quickly, efficiently and safely. Please feel free to contact us today for more details on how we can help make your work site safer and more efficient.