Poorly Reinforced Walls Aren’t the Only Deadly Hazards in Trenches and Excavations

Posted on May 15, 2019

Trenching and excavation projects are among the most hazardous types of construction jobs due to collapses, flooding, toxic fumes, and oxygen deprivation.

Confined Work Spaces Pose Deadly Hazards

Working underground in trenches, tunnels, sewers, manholes, and underground utility vaults puts workers at high risk of death. Dangers include cave-ins and collapsed walls, flooding from damaged water pipes, toxic fumes, and oxygen deprivation from working below ground. Workers employed in construction, mining, drilling, and utility operations are commonly exposed to the dangers of confined workspaces.

According to the U.S. Occupational Safety and Health Administration (OSHA), 22 construction workers died in trench collapses and cave-ins in 2017 and 2018. Additional deaths also occurred. One worker was crushed by a storm pipe as it was lowered into a trench. One worker drowned from a burst water pipe. Another worker was killed when a trench box was disassembled. In British Columbia, five construction workers exposed to nitrogen dioxide (NO2) poisoning had to be rescued while digging trenches in the basement of a large building. NO2 creates toxic fumes when fossil fuels like oil and coal are burned at high temperatures.

Although OSHA sets strict safety standards for working in confined spaces, many yearly accidents result in severe injury and death. Workers face dangers from falling overhead equipment and materials; contact with overhead electrical lines; falls into open pit areas; contact with dangerous machinery; combustible materials; heat exhaustion; dehydration; and lack of oxygen. OSHA classifies confined spaces as permit-required work environments that require safety testing prior to entry and continual monitoring for dangers. Permit-required confined spaces include spaces are enclosed or partially enclosed, not designed for continuous human occupancy, and have limited entry or exit access. They are spaces:

  • that contain a hazardous atmosphere
  • with limited airflow or oxygen
  • that contain toxic or combustible materials
  • with exposed live wires
  • with unguarded equipment or machinery
  • with downward sloping floors and/or inward sloping walls that connect to smaller spaces

For maximum workplace safety, OSHA requires all employers to identify permit-required confined spaces, properly train workers, and inform workers of hazards. Since confined spaces have small work areas and limited entry and exit openings, workers’ daily hours are limited. Workers are required to maintain contact with a trained supervisor outside of the space either by sight, phone, or two-way radio, which allows for evacuation alerts if necessary.