Health and Safety Precautions that should be taken when Breaking Ground
Before digging any trenches, pits, tunnels, or other excavations, decide what temporary support will be required and plan the precautions that are going to be taken against:
- Collapse of the sides
Prevent the sides from collapsing by supporting them with sheeting or adequate support systems and never work ahead of the support or remove it prematurely. Any excavation will be safe without additional support only if its sides are battered back sufficiently, or if the excavation is in sound rock.
- People and vehicles falling into the excavation
Edges of excavations should be protected with substantial barriers where people are liable to fall into them. All excavations in public places should be suitably fenced off to prevent members of the public approaching them.
Where necessary, use baulks or barriers to keep vehicles away from excavated edges. Where vehicles have to tip materials into excavations, prevent them from overturning into the excavation by using properly secured stop-blocks.
- Materials falling onto people working in the excavation
Do not park plant and vehicles or store excavated spoil and other materials close to the sides of excavations, this will make the sides more likely to collapse. Edge protection should include toeboards or other means and head protection should be worn.
- Undermining nearby structures
Make sure excavations do not undermine the scaffold footings, buried services or the foundations of nearby buildings or walls. Before digging starts, decide if extra support for the structure is needed. Surveys of the foundations and the advice of a structural engineer may be required.
- Underground and overhead services
Many serious accidents have occurred when buried services have been damaged during excavation work. Excavation work should not start until steps have been taken to identify and prevent any risk of injury arising from underground services.
Burns and electrocution can result if raised tipper truck bodies or excavators touch or come close enough to overhead power lines. The need to undertake excavation work close to or below such lines should be very carefully considered and avoided where possible.
- The inflow of ground and surface water
The supports to the side of the excavation should be designed to control the entry of groundwater and the design should take any additional water loading into account. Water entering the excavation needs to be channelled into sumps from where it can be pumped out. Alternative techniques for de-watering such as ground freezing and grout injection could also be used.