Trenching Safety Plan covers all the requirement needed to ensure the safety of the trench; this covers from point of excavation, to carrying out activity inside the trench, and maintaining the trench.
A trench is a narrow excavation below the surface of the ground, less than 15 feet wide, with a depth no greater than the width.
Hazards Associated With Trenches
Working in trenches and excavations is hazardous to both the workers who work inside them, and to workers on the surface. The hazards include:
- Cave-ins or collapses that can trap workers.
- Equipment or excavated soil falling on workers (e.g., equipment operated or soil/debris stored too close to the excavation).
- Falling into the trench or excavation.
- Flooding or water accumulation.
- Exposure to a hazardous atmosphere (e.g., gas, vapour, dust, or lack of oxygen).
- Contact with buried service lines such as electrical, natural gas, water, sewage, telecommunications, etc.
- Contact with overhead electrical lines.
- Slips, trips and falls as workers climb on and off equipment, or from inappropriate access and egress methods.
- Being struck by moving machinery, or by falling or flying objects.
- Hazards related to materials handling (e.g., lifting, struck by, crushed between, etc.).
Difference Between A Trench And An Excavation
A simple way to remember the difference is that all trenches are excavations, but not all excavations are trenches. Specifically, OSHA says an excavation is when soil is removed from the surface of the earth to create “any man-made cut, cavity, trench, or depression.”
A type of narrow excavation, a trench is below the surface of the ground, and its width—measured from the bottom—cannot be greater than 15 feet. Typically, a trench is deeper than it is wide.
OSHA’s requirements for trenches vary and depend on the depth of the trench as well as soil type. Find the excavation safety standards in 29 CFR 1926.650-652, Safety and Health Regulations for Construction.
Trenching Safety Plan Covers:
- Safeguarding procedures, including protection for employees, underground installations, hazardous atmospheres, confined spaces, water accumulation, adjacent structures, surface encumbrances, and walkways
- Qualifications for the competent person
- Protective systems, including sloping, benching, shielding, and shoring
- Accident investigations
- Emergency operations
- Employee training
Trenching Plan should Include The Following Elements:
- A hazard assessment: The hazard associated with the trench should be well assessed and controls put in place.
- Identification and credentials of competent person: A competent person should be on stand-by to monitor the process. The OSHA Standards require that the competent person must be capable of identifying existing and predictable hazards in the surroundings, or working conditions which are unsanitary, hazardous, or dangerous to employees, and have authorization to take prompt corrective measures to eliminate them and, if necessary, to stop the work.
A competent person is required to:
– Have a complete understanding of the applicable safety standards and any other data provided.
– Assure the proper locations of underground installations or utilities, and that the proper utility companies have been contacted.
– Conduct soil classification tests and reclassify soil after any condition changes.
– Determine adequate protective systems (sloping, shoring, or shielding systems) for employee protection.
– Conduct all air monitoring for potential hazardous atmospheres.
– Conduct daily and periodic inspections of excavations and trenches.
– Approve design of structural ramps, if use.
- Diagram or sketch of the area where the work is to be done, with adjacent and nearby structures shown: This plan is very important to help identify near-by facilities that could pose additional threat.
- Projected depth of the excavation: The depth of the trench is directly proportional the level of control needed; so it should be ascertained.
- Projected soil type and method of testing to determine soil type.
- Planned method of shoring, sloping, and/or benching.
- Planned method for confined space entry, trench access and egress, and atmospheric monitoring processes.
- Location of utility shutoffs (if required).
- Proposed methods for preventing damage to overhead utility lines, trees designated to remain, and other man-made facilities or natural features designated to remain within or adjacent to the construction rights-of-way.
- Plan for management of excavated soil/asphalt/concrete.
- Plan for traffic control.
- Excavation permits: All underground lines/utilities (communication lines, water, fuel, electric lines) will be located and protected from damage or displacement. Utility companies and other responsible authorities will be contacted to locate and mark the locations and, if they so desire, direct or assist with protecting the underground installations. The contractor will obtain an excavation permit from an authority having jurisdiction before the initiation of any excavation work.
- For cofferdams, a controlled flooding plan and fall protection.
- Access to and exit (egress) from the excavation.
- Evacuation procedures.
Trenching Safety Rules
- Collapsing should be avoided by supporting the sides by either battering them or supporting them with sheets.
- Materials from the excavation should be stored at a safe distance from the excavation, this will help reduce the risk of them falling onto people.
- Adding barriers to excavation is an essential precaution to avoid people falling into the excavation.
- It is safer if vehicles are kept completely out of the excavation area, but if required the use of barriers and stop-blocks should help mitigate that danger.
- Cable, pipe, and service plans should be used to ensure that underground services are known so they can be marked on the ground or, ideally, the area avoided entirely.
- Around the areas where there are underground services, mechanical equipment should be avoided and instead use spades and/or shovels.
- Picks and forks should be avoided as they are more likely to pierce cables and pipes.
- Flooding can be avoided by ensuring that there is appropriate pumping equipment so that any water that seeps into the excavation can be easily pumped out to a safe area.