Deaths in confined spaces occur because the atmosphere is oxygen-deficient, toxic, or combustible. To protect employees who work in such environments, says Jeff Bowman, Environmental Training Coordinator of Texas A&M Engineering Extension Services, Infrastructure & Safety Training, public works departments should perform three basic steps at each jobsite:

  • Identify all confined spaces. “Because public works projects are constantly changing, this evaluation must take place daily and any time the work being performed changes,” he says.
  • Determine if they contain or could develop hazards. Certain concentrations of flammable gas, vapor, or mist and airborne combustible dust, for example, can cause illness, incapacitation, inability to self-rescue, injury, and death. Another red flag is when the space contains material that could engulf a worker or is configured so that the worker could be trapped or asphyxiated.
  • Figure out which of the four classifications they are and, if necessary, obtain a permit.

Similar to an OSHA “non-permit space, an Isolated-Hazard Confined Space (IHCS) is the lowest hazard level. Hazards are eliminated or removed via blanking and blinding; misaligning or removing sections of lines, pipes, or ducts; a double-block-and-bleed system; locking out or tagging out energy sources; machine guarding; and blocking or disconnecting all mechanical linkages. Controlled-Atmosphere Confined Space (CACS) hazards are sufficiently controlled via ventilation.

Ventilation isn’t enough to lower hazard potential or maintain safety in a Permit-Required Confined Space (PRCS). Inwardly converging, sloping, or tapering surfaces could trap or asphyxiate a worker; or the space presents an engulfment hazard or other physical hazard. Workers may not enter the space until the employer has completed all items required by the permit, including testing. Sewers are a Continuous System PRCS (CSPRCS) because they’re part of or contiguous with a larger confined space, making it impossible for the employer to isolate them.

“A PRCS also is subject to a potential hazard release from the larger confined space that would overwhelm personal protective equipment and/or hazard controls, resulting in a hazard that is immediately dangerous to life and health,” says Bowman. “There are difficulties associated with isolating the hazards. Special precautions are necessary, in addition to the other PRCS requirements, to ensure adequate protection.”

Check out this 2-page “cheat sheet” for how the Confined Spaces in Construction standard applies to sewer systems.