Excavation & Trenching

Summary

Working in and around excavations and trenches can result in serious injury and death if hazards are not properly identified and controlled at all times.
 
This guideline highlights the main components and risks associate with excavations and trenches during construction and maintenance operations.  The Environmental Health & Safety Office is available for general consultation related to these activities.

Scope

When an employee is required to work in an excavation 5 feet in depth or more, protection from cave-ins shall be provided by an adequate protective system.  Employees may work in excavations less than 5 feet in depth without a protective system provided that the ground is evaluated by a competent person who determines that there is no indication of a potential cave-in.
 
Excavations and trenches 4 feet in depth or more must also be provided with a stairway, ladder ramp or other safe means and must be located so there is no more than 25 feet of lateral travel distance for the employee.
 
In excavations and trenches 4 feet in depth or more where hazardous atmospheres may occur, the space shall be evaluated, and controls in place, to prevent exposure to the employee.

Policy & Regulation

University of Iowa Operations Manual, Part III Human Resources, Division II Standards and Ethics, Chapter 16.4d Policy on Ethics and Responsibilities for University of Iowa Staff.

IOSH Construction Safety and Health Regulations, 29 CFR 1926.650, Subpart P – Excavations.

Glossary

Competent Person
An Individual who has knowledge, training, and experience in recognizing and controlling hazards associated with excavations and trenching operations, shall be involved in all stages of the work being done by employees.  A department shall have such an individual(s) assigned for this purpose.  
Benching (Benching System)
A method of protecting employees from cave-in by providing a series of steps with horizontal and vertical surfaces within the excavation or trench.
Cave-in
The sudden movement of soil or rock that that causes these materials to fall into the excavation or trench that causes the employee to become entrapped buried or immobilized.
Excavation
A man-made cut, cavity, trench, or depression in the surface of the earth.
Faces or Sides
The inclined earth surfaces formed as a result of excavation or trenching.
Hazardous Atmosphere
An atmosphere that contains an air contaminant or lack or oxygen that can result in injury, illness or death.
Examples of hazardous atmospheres include: explosive, flammable, poisonous, oxygen deficient, and toxic.
Protective Systems
A method used to protect an employee from cave-in of soil or rock material in an excavation or trench; 
or from the collapse of adjacent structures.  Such systems have the capacity to resist without failure all loads that are placed on it.  Protective systems include support systems, shoring systems, sloping and benching systems, and shield systems.
Sheeting
Members of a shoring system that provide support to the vertical sides of the excavation or trench.
Shield System
A method used to protect an employee form cave-in of the excavation or trench.  Shields are usually referred to as “trench boxes” or “trench shields.”
Shoring System
A structure used to prevent the cave-in of an excavation or trench.  The structure may be made of metal, hydraulic, mechanical, or timber shoring systems that support the sides of an excavation.
Sloping System
A method to protect employees from cave-in in an excavation or trench.  It is done by calculating the angle of incline to the soil type, environmental conditions and application of loads applied on the excavation.
Trench
A narrow excavation made in the surface of the earth.  It is generally deeper than wide with the width at the bottom not greater than 15 feet.

Responsibilities

Deans, Directors and Department Heads are responsible to:

  • Actively support these procedures within individual units.
  • Ensure an environment where employees are encouraged to follow these procedures.
  • Designate the Department’s Competent Person for excavation and trenching.

Supervisors are responsible to:

  • Implement these procedures
  • Assure that staff is aware of University and department procedures, instructed on the details of implementation, and provided with training, personal protective equipment, and methods of control.
  • Maintain documentation and records as required in these procedures.

Employees are responsible to:

  • Comply with these procedures and any further safety recommendations provided by supervisors.
  • Conduct assigned tasks in a safe manner, wear appropriate personal protective equipment, and obtain training and information prior to using tools.

EHS is responsible to:

  • Provide guidelines, administrative consultations and reviews, and select technical and field services.
  • Exercise surveillance over health and safety issues at the University.

Procedures

Protective System
The department’s Competent Person shall evaluate and select the type of employee protective system to use and shall inspect it prior to the start of the work and as needed during the shift.  At a minimum, daily inspections shall be done of excavations, the adjacent areas, and protective systems used. Whenever the competent person determines that a hazard to the excavation or trench exists, exposed employees shall be removed immediately from the area until the hazard(s) has been corrected. 

All employees using the excavation or trench shall use it as instructed by the Competent Person and report any problems immediately to the competent person.

Specific Requirements
At a minimum, the following items shall be reviewed and implemented as required to the specific excavation and trench operation:

  • Removal of all support encumbrances located near the surface of the excavation or trench.
  • Underground utility installations located.
  • Access and egress from the excavation or trench provided.
  • Any employee exposure to vehicular traffic and employees provided with visible warning vest or garments.
  • Employees protected from falling loads while in the excavation or trench.
  • A warning system provided when mobile equipment nears the edge of the excavation or trench.
  • Hazardous atmospheres evaluated prior to entry and during work based on containment(s) present.
  • Water hazards associated with excavation or trench are evaluated and controlled.
  • The stability of any adjacent structures is evaluated and controlled.
  • Loose rock or soil is kept back from excavation or trench by at least 2 feet.
  • Walkways are provided where employees or equipment are permitted to cross over excavation.
  • Daily inspections shall be done of excavations, adjacent areas, and protective systems by the Competent Person.

Related Programs or Procedures

Assistance and Resources

The Environmental Health & Safety is available for consultation and assistance in assessing excavation and trenching operations.  Special situations may require outside expert assistance also. Departments should also work with EHS in the administrative annual review to review protocols in excavations and trenching operations.

 

updated 04/2012