An experienced person should manage and monitor the excavation work, including the quality of the soil, and make decisions on slopes and the use of reinforcement materials.
Before you start excavating, it may be necessary to investigate the following with local authorities or utility companies:
- Contamination of the soil from earlier production or landfill sites.
- Any earlier excavations in connection with supply pipes or other facilities.
- You must pay particular attention to whether there are any installations in the ground. There may be gas pipes, electricity cables or communication cables.
- Permission to excavate from the municipal authorities.
It may be necessary to undertake surveys of the soil before starting excavation work, e.g. if there is contamination of the soil, and if so to what extent.
Written assessment – work plan
In the case of excavation work at depths in excess of 5 m (particularly hazardous work), the employer must create a written assessment for execution of the work. If necessary, this assessment must include specific arrangements so as to avoid any hazards.
If there is more than one employer, the developer in such instances must also create a Health and Safety Plan. It must be possible for all work processes to take place properly, including with regard to ergonomics and good working positions.
When planning excavation work, specific conditions may require preparation of an emergency contingency plan. Here, the necessary equipment must be available. This may include pumps, ladders, additional reinforcement materials, respiratory protection and special workwear if there is any risk of encountering contamination.
Safety during excavation work
Make sure that the soil is exposed, and use lights at dark times of year. Rain, snow, frost, thaw and darkness may be of great importance with regard to safety during excavation work.
There may be sand veins, water-bearing strata (flow) and previous excavations with loose backfill. There is also a risk of collapse with all faces. Pay particular attention to e.g. sand, flow, marsh, water veins or a high water table.
Also, pay attention to buildings, structures, pipes or trees near to where you will be excavating.
You must also pay attention to factors such as heavy traffic which includes buses and trucks, or piledriving and blasting which may affect the stability of the soil.
Excavation work near roadworks
You must compile a delineation plan if excavation work is to take place near to or on roads carrying traffic. The local road authorities have to approve the plan, which must be compliant with the rules for delineation.
The distance between work site and road is important as vibration from the passing traffic may cause the excavation to collapse.
Excavation without reinforcement
It is important to ensure that the sides will not slip in the case of excavation without reinforcement. You can ensure this by means of the following:
- by establishing facilities,
- by keeping the sides even and free of large rocks, and
- by removing excavated soil so that it does not place stress on the edges and allow the excavated soil to slip down.
To safeguard against a hazardous collapse, you can create what is known as a slope, in which the sides take the shape of steps with an incline of 1:2 (1 across and 2 up). In the case of excavation depths in excess of 5 m, the facility must have an incline of 1:1.
In exceptional circumstances, it may be justifiable to work in excavations without facilities at a depth of 1.7 m, if the earth has been deemed to be stable. However, it is normally necessary to safeguard against collapse when working on small excavations where staff are to work in a kneeling position, for example.
In the case of excavation work in connection with roadworks, the distance from the edge of the excavation to the carriageway must be at least the depth of the excavation.
Excavation with reinforcement
You must reinforce the excavation when it is not possible to create a slope. There are several ways in which this can be done:
Use extensible planks if you are to excavate to depths greater than 2.25 m.
Use an excavation box. This must protrude at least 0.15 m up over the edge when it stands at the bottom of the excavation. The excavation box must reach all the way down to the bottom of the excavated trough.
When using an excavation box, you have to remain only in the area safeguarded by the excavation box. It must also be possible to get out of the excavation box using a ladder.
The same is applicable to implementation of reinforcements using clamps or extensible planks. Here, as much is prepared as possible on the ground when reinforcement work begins. After this, the reinforcement is established continuously from the ground and from the reinforced part of the excavation.
If there are to be railings along the edges of the excavation at ground level, these can be established as part of the reinforcement.
In the case of large excavation depths, it may be necessary to establish sheeting.
Excavation work close to existing pipework or cabling
If there are pipes or cables in the ground or overhead in the locations where you are to excavate, these must be taken into account in your planning of excavation work.
Make sure that:
- You have information on all pipes and cables within 10 m of the excavation sites.
- Installations in the ground are clearly marked.
- Overhead cables, roads and cycle paths are clearly marked on drawings and similar.
Applicable safe distances when working close to overhead cables. The minimum distances shown must be respected.
The safe distance in the case of low voltage overhead cables is 1.5 m at a radius from the cable suspension point plus 3 m from ground level and up to this point.
Breaking overhead cables or ground cables
If an excavator strikes an overhead cable or ground cable, the driver must proceed as follows:
- Stay in the machine until the power has been switched off.
- Keep everyone away from the machine – see safe distance.
- Notify the local power supply company, and call the emergency services (112) if necessary.
Access and escape routes
All excavations must have proper access and escape routes.
The risk of landslide is particularly great when work is taking place in a construction pit as the side often have to remain where they are for a length of time and are so affected by the wind and weather.
Therefore, the faces must either be reinforced or have a slope when work is in progress between a foundation and a face.
The work area must be at least 1 metre wide (measured at knee height). The bottom of the construction pit must be flat and even so that people can work properly there. If necessary, put down a layer of road construction gravel.
Steps must ensure access to and from the construction pit. These must have handrails on both sides, with both hand and knee rails. If tools are to be transported using the steps, they must be at least 0.8 m wide.
In construction pits which are plugged, a stair turret will be installed as an access route, or possibly an elevator.
There must always be a ladder close to work areas which can be used as an escape route between the foundation and the face.
It must not be possible for people to fall into the construction pit. Set up markers 2 m from the edge, or set up railings. The railings must only be open by the steps.