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October 16, 2013
Cal/OSHA issues citations after trench collapse: What the employer should have done differently

Cal/OSHA cited a Southern California contractor in a deadly trench accident that killed one employee and severely injured another. The two pipe layers were checking the depth of a trench when an unshored wall caved in on them.

Cal/OSHA issued four citations, including one willful violation, totaling more than $100,000. The willful violation was cited for the employer’s failure to install required shoring in the trench, even after a cave-in earlier in the day, and continuing to send workers into the unprotected trench.

Acting Cal/OSHA Chief Juliann Sum noted, “Incidents like this are heartbreaking because they are so unnecessary. Employers must be more vigilant in protecting worker safety.”

Other violations included failing to properly protect the trench from caving in, not inspecting the trench after the earlier cave-in, lack of training on heat illness prevention, and lack of an effective injury and illness prevention plan.

Review these trenching requirements to avoid citations

Like federal OSHA, Cal/OSHA requires a daily inspection of trenches and associated protective systems by a competent person before work begins and throughout the day as conditions change. A competent person is defined as someone who can demonstrate:

  • Knowledge of the provisions pertaining to excavations, trenches, and earthwork;
  • Knowledge of soil analysis;
  • Knowledge of the use of protective systems;
  • Authority to take prompt corrective action on the job as conditions warrant; and
  • Ability to recognize and test for hazardous atmospheres.

Several factors affect the kind and amount of shoring needed. These include:

  • Depth of the trench. A trench must be shored or sloped if it is 5 feet deep or more. Shallower trenches must be shored if there is a possibility of soil movement.
  • Soil classification. More protection is needed for less stable soil and for soil with a higher liquid content.
  • Changing weather conditions. Hard-packed soil can become unstable after a rain. 
  • Heavy loads in the area. Nearby structures like buildings and curbs exert stress on trench shoring.
  • Vibration.  If you are digging a trench near a roadway or location where other operations cause vibration, make sure the shoring/sloping design reflects the conditions.
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