Trench Box Requirements Every NJ Utility Contractor Needs to Know
A trench box protects workers inside the shield. It does not remove the need to plan the excavation, check the surrounding conditions and use the box according to its design.
When a protective system is required
Under OSHA’s construction excavation standard, an excavation five feet deep or more needs a protective system unless it is made entirely in stable rock. For an excavation under five feet, a competent person may determine that no protective system is needed if there is no indication of a potential cave-in. The decision depends on the actual conditions, not the name of the job or the equipment being used.
Sloping, benching, support systems and shield systems are among the options described in Subpart P. If a trench box is selected, check its capacity and use it within the manufacturer’s tabulated data or the applicable design. The standard allows excavation up to two feet below the bottom of a support or shield only when the system is designed for the full depth and there is no sign of soil loss behind or below it.
Set and use the shield as designed
OSHA requires shield systems to stay within their design loads and to be installed so they resist hazardous movement if a sudden lateral load occurs. Workers must be protected from cave-ins while entering or leaving a shield, and must not be inside it while it is being installed, removed or moved vertically.
For excavations 20 feet deep or greater, the protective system must be designed by a registered professional engineer or based on tabulated data prepared or approved by one. Do not choose a system for a deep trench by comparing its dimensions alone; use the design information that applies to that system and excavation.
Check the excavation and access
A competent person must inspect the excavation, adjacent areas and protective systems before work begins and as needed throughout the shift. The standard also calls for another inspection after rain or another hazard-increasing occurrence. If the inspection identifies a possible cave-in, protective-system failure, hazardous atmosphere or another danger, employees must be removed from the hazardous area until precautions are taken.
In a trench four feet deep or more, provide a ladder, stairway, ramp or other safe egress so workers do not have to travel more than 25 feet laterally to reach it. Before digging, estimate the location of utility installations and contact the utility companies as required by the standard and applicable state procedures. If a hazardous atmosphere may reasonably be expected in an excavation deeper than four feet, test before employees enter.
Before the crew enters
- Confirm the depth, soil conditions and protective-system selection.
- Have the applicable design or manufacturer’s tabulated data available and follow it.
- Inspect the excavation, nearby areas and protective system; correct hazards before entry.
- Check the location of underground utilities before excavation reaches them.
- Provide egress within the OSHA travel-distance limit for trenches four feet deep or more.
- Test for hazardous atmospheres when conditions make one reasonably likely.
If you need a written excavation procedure or a JHA for a defined task, I can help prepare one from the project information you provide. Blueprint Safety works remotely; I do not design protective systems or visit jobsites.
For the details that apply to a specific excavation, use OSHA’s excavation standards and the system manufacturer’s instructions. This article is a general overview, not a substitute for the design or site-specific requirements.