Safe digging practices: how to avoid underground services and excavation collapses

What can go wrong

HSE lists the main hazards of excavation work as collapse of the sides, material falling in on people, people or plant falling in, undermining of nearby structures, damage to underground services such as electricity and gas, contact with overhead lines, and water getting in. Your RAMS should deal with each of those that applies to the job.

Plan, locate, dig

HSE’s guidance on avoiding danger from underground services (HSG47) breaks safe excavation into three elements: planning the work, locating and identifying buried services, and digging safely.

1. Plan before you dig

• Get the records. Request plans from the owners of utilities in the area, and check for private services, such as supplies to outbuildings and old abandoned pipes, that will not be on any utility drawing.
• Look at the site. Manhole covers, valve boxes, lamp columns, meter boxes and patched tarmac all hint at what lies below. Overhead lines tell you where underground supplies might connect.
• Consider a survey. If the ground is complicated or the risk is high, a utility or ground-penetrating radar survey can give a much clearer picture than records alone.
• Write it into the RAMS. Say how services will be located, who is trained to do it, where trial holes will go, and what happens if an unexpected service turns up.

2. Locate and mark

• Use a cable avoidance tool (CAT) and signal generator, used by a trained operator, to scan for services before digging, and scan again as work progresses. Scanning is not foolproof, so combine it with the records and a careful look at the site.
• Mark what you find clearly on the ground and make sure everyone knows what the marks mean.
• Confirm the position and depth of services by digging trial holes by hand, rather than assuming drawings are accurate.

3. Dig safely

• Treat every service as live until the owner confirms otherwise.
• Use hand tools in the area around located services, and avoid using tools in a way that could pierce or crush a cable or pipe.
• Do not use buried services as a handhold, a step or something to hang loads from, and keep them supported if exposed.
• Keep checking as you go. If something unexpected appears, stop and reassess.

Keeping the excavation itself safe

Services are one risk. The excavation is the other. HSE’s advice is to decide before work starts what temporary support will be needed and to have the equipment on site, or to slope the sides back to a safe angle for the ground. Other key points:

• Fit edge protection such as guard rails and toe boards, or use trench boxes that extend above ground, to stop people and materials falling in.
• Keep plant, spoil and materials away from the edge, since their weight can bring the sides down.
• Keep clear of overhead power lines.
• Have a competent person inspect the excavation at the start of every shift and after any incident that might have affected stability, and record the inspection in writing.
• Provide safe access in and out, such as a ladder, and consider water, fumes from engines and the effect on nearby buildings.

If you hit a service

1. Stop work and get everyone well away. Do not try to repair or move the damaged service.
2. If you suspect a gas leak, call the National Gas Emergency Number on 0800 111 999. If a cable has been damaged, stay well away and call 105 to reach your local electricity network operator. If anyone is hurt or in danger, call 999.
3. Keep people back, keep ignition sources away from any gas, and wait for the emergency services or the utility.
4. Report it, record what happened, and review the RAMS before work resumes.

Write these steps into the emergency section of your RAMS and make sure everyone on site knows them before the first spade goes in.

Need help knowing what is under the ground?

AutoRAMS is part of Ambler Group, which also runs Ambler Group Surveys. If you would like help finding out what is below the surface before you dig, visit Ambler Group Surveys to find out more.