We have stackable trench boxes rated for 25 feet total. Do I need to use a Registered Professional Engineer (RPE) to design our protective system for our 22-foot deep trench? Could you also give me a brief overview of trenching and excavation safety facts?

Even with fatalities from trenching and excavation work at a staggering 112 percent higher than the rest of the construction industry, injuries and fatalities continue to plague this type of work despite well-known control methods.  In a study of 542 trenching and excavation related deaths from 1992-2001, most deaths (76 percent) were caused by cave-ins, most involved excavation contractors (141, 26 percent) or water/sewer/pipeline construction (131, 32 percent) and most deaths occurred in small businesses (48 percent in companies with ten or fewer employees, 70 percent with fifty or fewer employees).

These deaths can be greatly attributed to lack of or improper use of protective systems. This is a direct result of inadequate training. In a 2002 survey of contractor members of the National Utility Contractors Association on the use of trench boxes and safety practices, they identified not using trench boxes when they are onsite and taking other shortcuts that violate OSHA standards and put workers at risk as the greatest safety problems.  The survey also identified that, as seen across the board in all areas of construction, increased worker training sessions per year was directly tied to lower reported injury rates.

The 29 CFR 1926 contains the OSHA standards for construction.  It details all requirements for various trades including trenching and excavation. To prevent these types of injuries and deaths, OSHA standards require that protective systems for trenches over 20 feet deep must be designed by a RPE.  Depending on the soil type and design of the trench box however, you may not need a Registered Professional Engineer for your situation.  The reason why? Because you already are using a one. Let me explain.

OSHA requires that trench boxes be designed by a RPE, therefore when he/she rated your stackable trench boxes for 25 feet, it fulfilled the requirements of the standard for trenches over 20 feet as long as it is used in accordance with the manufacturers recommendations. In addition, OSHA issued a letter of interpretation clarifying this is in fact the case:

March 1992, response from Directorate of Compliance Programs, Patricia Clark:

"...In regard to whether manufacturer's tabulated data can be used to design protective systems for trenches more than 20 feet in depth, please be advised as follows: Protective systems that are designed using manufacturer's tabulated data can be used in trenches deeper than 20 feet provided the use is within the limits of the data, including depth limitations and soil type. It should be noted that all tabulated data, by definition (1926.650), must be approved by an RPE."

Trenching and excavation is dangerous business.  Ensure that your employees are protected at all times, and you will be protecting not just them, but your business as well. Always consult with the manufacturer, OSHA or a Certified Safety Professional if you have any doubt because when a trench starts to collapse, it is too late to start playing it safe.

Construction Business Owner, February 2008