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 are 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. However, 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.
Numerous precautions should be taken when excavating or working in trenches. If you work for
a utility that is covered by the Saskatchewan Occupational Health and Safety Regulations, there
are specific regulations (Table 17 Excavation and Trench Shoring Occupational Health and
Safety Division Supplemental Paper ‘Safety in Excavations and Trenches AND Part 17
Excavations, Trenches, Tunnels and Excavated Shafts) that govern most subsurface excavations.
Requirements for Trenches and Excavations
A complete and detailed rundown of all the rules and regulations for trench and excavation
safety would be far too lengthy to tackle in a tailgate safety meeting. But the following are a few
points to remember. (For specific regulations, refer to the OHS regulations referenced above.)
- Before beginning any subsurface work such as trenching, contact the local utility alert
service to establish the location of other underground services such as natural gas, sewer,
telephone, electric power, and cable television. - Every trench must have a safe and ready means of exit. If a trench is deeper than four
feet, a stairway, ramp, ladder, or other safe means of exit must be available within 25 feet
of a worker in the trench. - Don’t expose workers in trenches to overhead loads handled by lifting or digging
equipment. - If an oxygen deficiency (less than 19.5 percent) or hazardous atmosphere has the
possibility to 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 much be provided. - 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. - Unless the excavation is made in stable rock, any trench greater than five feet in depth
much be inspected by a qualified person and if conditions warrant, a protective system
(such as a shoring cage) must be installed. - Trenches and Excavations must be created dependent on the soil conditions, different soil conditions can lead to collapse without proper cutting of the bank or a shoring cage.