Is a trench a permit-required confined space?

A question sometimes comes up as to whether a trench or other excavation is a permit-required confined space under OSHA standards.

The answer in broad terms is no, even though conditions in a trench can sometimes resemble those in a permit-required confined space, as Curtis Chambers points out in an excellent article. However, there are still similar precautions that must be followed under OSHA’s excavation standard, even if no permit is required.

Examples of situations that could resemble those in a permit-required confined space are:

• When trenches are cut near landfills, creating the possibility that methane gas would seep into the space.

• Digging near leaky underground tanks or pipelines.

• Tapping/tying into an existing sewer line inside of a trench to make a connection.

• Using combustion engine-powered tools and equipment inside of a trench.

In those cases, where the trench is more than four feet deep, the excavation standard requires testing the atmosphere and taking precautions to protect workers.

Employers should also be aware that it is also possible to have a permit-required confined space in a trench where work does not otherwise require a permit. An example might be a 30-inch pipeline laid inside the trench that ties into a sewer line.