Trenching: Don’t Dig Into Trouble!

If you’re involved with water utility maintenance or construction, sooner or later you’re going to be involved in trenching operations. And, despite all the classic slapstick movie routines you may have seen through the years, safely excavating and working in an open trench is serious business.

Not all holes in the ground are trenches. A trench is defined as a narrow excavation made below the surface of the ground. In general, the depth is greater than the width, but the width of a trench (measured at the bottom) does not exceed 15 feet. A wider excavation can be considered a trench if forms or other structures are installed such that the distance from the edge of the form or structure to the side of the excavation is less than 15 feet.

Working in an unprotected trench is dangerous. The walls can collapse suddenly and without warning. When this happens, workers do not have time to move out of the way. A small amount of dirt may not seem dangerous, but one square yard can weigh more than 3,000 pounds—the weight of a compact car. This small amount of dirt is enough to fatally crush and suffocate workers.

Numerous precautions should be taken when excavating or working in trenches. If you work for a utility that is covered by the Occupational Safety and Health Administration (OSHA), specific regulations (29 Code of Federal Regulations 1926, Subpart P) govern most subsurface excavations.

A complete and detailed rundown of all the rules and regulations for trench and excavation safety would be far too lengthy to tackle here or in a tailgate safety meeting, but the following are a few points to remember:

S Before beginning any subsurface work such as trenching, contact 811 or One Call Center for the local utility alert service to establish the location of other underground service lines, such as natural gas, sewer, telephone, electric power, and cable.

S Every trench must have a safe and ready means of exit. If a trench is deeper than 4 feet, a stairway, ramp, ladder, or other means of exit must be available within 25 feet of a worker in the trench.

S Don’t expose workers in trenches to overhead loads handled by lifting or digging equipment.

S If it’s possible that an oxygen deficiency or hazardous atmosphere may exist in a trench or excavation, the air in the excavation must be tested before employees enter and while work is being conducted. If necessary, adequate ventilation must be provided.

S If hazardous conditions exist (or may exist), emergency rescue equipment, including a breathing apparatus, safety harness and line, and basket stretcher must be readily available near the trench.

S Unless the excavation is made in stable rock, any trench greater than 5 feet in depth must be inspected by a qualified person, and if conditions warrant, a protective system (such as shoring) must be installed.

For more information go to the OSHA website at www.osha.gov/publications/ trench/trench_safety_tips_card.pdf. S