Safety in soil excavation and trenching
Workplace accidents involving soil excavation and trenching, along with working at heights and electrical shocks, are among the most frequent accidents in the construction industry. Besides being a common occurrence on construction sites, they are often highly serious, resulting in the death of workers involved in this type of work.
Below, we list the main occupational safety measures that must be observed before beginning work, as well as during its execution.
Preliminary site preparation and inspection:
The execution design for open-pit excavations must comply with the requirements. Click here for Excavation Safety Course
Perform a preliminary survey of the ground. If there are underground utilities, rocks, or materials of any nature, engineering must provide a solution to remove or preserve these obstacles so that the excavation can be carried out safely.
If there are underground power cables near the excavation site, work may only begin once the cables have been disconnected. If disconnecting the cables is not possible, special measures must be taken with the electricity company to request temporary disconnection.
All workers involved must wear Personal Protective Equipment (PPE) appropriate for the risks they will be exposed to. When digging trenches or excavating of any nature, a Work Permit (PT) must be issued in advance by the workers’ immediate supervisor. The supervisor of the area where the work will be performed will approve and/or recommend additional safety measures in the Work Permit if interference with underground water, sewage, electricity, telephone, or other networks that may increase the risk of accidents for the workers involved is detected. Before beginning excavation, clear the area to be worked, isolate, sign, and securely shore up any rocks, trees, walls of neighboring properties, and existing machinery and equipment that will not compromise stability.
Work Area Signage:
Excavations must have warning signs, including at night, and an isolation barrier around their entire perimeter. Signage may include sawhorses, traffic cones, zebra tape, or warning signs.
When excavation work interferes with traffic on roads, avenues, or streets, specific road signage guidelines must be followed, as required by local regulations. Access for workers, vehicles, and equipment to excavation areas must be permanently posted, including warning signs and a barrier prohibiting access by unauthorized persons.
Shoring installation in buildings, excavations, slopes, and trenches:
Among other preventive measures taken before beginning construction, the condition of neighboring buildings or structures that may be affected by the excavation should be assessed, and shoring should be implemented beforehand if necessary. Excavations deeper than 1.25 m should be analyzed by an engineer, who will determine whether shoring or wall lining is necessary. It is also necessary to locate ladders or ramps in strategic positions for the quick exit of workers from the excavated area in emergencies. Unstable slopes in excavations deeper than 1.25 m (one meter and twenty-five centimeters) must be ensured by structures specifically designed for this purpose.
The material removed during the excavation should be deposited at a distance greater than half the depth, measured from the edge of the open trench. Containment measures should be provided for the material removed from the trench to prevent it from being carried away by rain, and the same should be done to prevent the trench from flooding. The trench should be shoring up as it is dug. Metal profiles or wooden planks may be used for this purpose, following a prior shoring plan.
Excavation services must be performed by a legally qualified technician, and a specific soil movement and trench shoring plan must be prepared, previously discussed with designers and occupational safety professionals.
Manual Excavation:
When excavating manually, a cable system with a hook and safety lock should be provided for removing material from the trench using a bucket or other container. The cable, hook, and bucket must always be kept in good condition to ensure safe lowering and raising of material, protecting workers working inside the trench. Nighttime excavation work must have adequate lighting to ensure a minimum of 150 lux in the work area. Floodlights for nighttime illumination should be positioned so as not to blind equipment operators or drivers passing by. If there is a potential leak in an underground gas network, the excavation site must be continuously monitored so that, in the event of a leak, an alarm system, either audible or visual, can be activated, prompting workers to leave the work site.
Machine-Based Excavation:
Excavations using machinery should be planned taking into account the characteristics of the terrain where the operation will be carried out. Ground subsidence can cause the machine to tip over. All points where the machine’s footings will be supported must be assessed in advance. For excavations using machines with booms (e.g., excavators, backhoes), the possibility of interference from overhead lines such as telephone lines, power lines, walkways, conveyor belts, or other obstacles during the operation must be assessed before beginning operations. The machine operator should be informed of these risks and, if necessary, should have an assistant to guide the machine’s operation to ensure greater safety. Whenever possible, the site’s electrical network should be disconnected.
