Safety Policies and Procedures Manual
Chapter 3: Shop and Agricultural Workplace Safety

Trench and Excavation Safety

SPPM 3.46

For more information contact:
   Environmental Health and Safety


University units engaged in trench and excavation projects done by University employees are to protect employees, students, and the public from cave-ins and falling into trenches and excavations.

Employees and students working in trenches and excavations four feet or greater in depth must be protected from cave-ins by a protective system. See the second bullet point under Responsibilities.

Note: Trenches and excavations that are less than four feet in depth do not require employee protective systems unless indications of possible cave-in are present.


Supervisors and faculty are to comply with this policy and protect employees and students from hazards associated with trenches.

Employees and students are to comply with this policy and trench and excavation safety training information provided by University officials.

General Requirements


All supervisors, employees, and students working in or around trenches and excavations done by University employees are to be trained in trench and excavation safety procedures.

Contact EH&S to schedule trench and excavation safety training sessions.

Competent Person

Each trench and excavation project done by University employees requires a “competent” person to evaluate the project site for potential hazards. A competent person is someone who:

  • Can identify existing and predictable hazards.
  • Has authority by nature of her or his position to stop a project and take prompt corrective action to eliminate hazards.
  • Is knowledgeable in the requirements specified in the trench and excavation Washington Administrative Code section (WAC 296-155 (Part N)).

Note: Contact EH&S for assistance in identifying a competent person or fulfilling the requirements to become a competent person.

The competent person is required to inspect trench and excavation project sites:

  • Before the project begins,
  • Each day before work begins,
  • As necessary throughout the shift, and
  • After each rainstorm.

The competent person supervises the following activities:

  • Locating and protecting underground utilities.
  • Selecting employee protective systems such as:
    • Sloping
    • Aluminum hydraulic shoring
    • Trench boxes
    • Registered engineered designed protective systems
  • Safely storing excavated materials.
  • Inspecting project sites for sufficient trench and/or excavation egress.
  • Inspecting the stability of adjacent structures.
  • Inspecting for water accumulation in the trench and/or excavation.
  • Inspecting for placement of adequate physical barriers before a trench and/or excavation is left unattended.

Revisions:  Reviewed June 2013; Mar. 2011 (Rev. 88); Oct. 1992 – new policy (Rev. 10).