Tony Abbott of ECA member company Modus Utilities explains why contractors need to plan ahead when digging in our bustling cities.
Walk down any main street in one of our cities and you will soon come across the barriers that mark out a hole or trench where cables or pipes are laid. As businesses and homes need more power connections or internet connectivity, the number of entrepreneurs innovating on our streets is growing.
Digging on city streets is hard and potentially dangerous work. And it looks like it’s getting riskier. The Energy Networks Association reports that power cable strikes have increased by 46% since the end of the lockout. On average, 70 people each year are seriously injured as a result of contact with underground power cables.
These are not the only potential dangers under our streets. There are gas and water lines as well as telecommunications cables to consider when carrying out these projects. The problems are exacerbated when working in a place like the City of London where there are narrow streets and heavy traffic.
There are tips on how to approach these projects safely. HSG47 Avoid the danger of underground services from the Health and Safety Executive (HSE) outlines three important steps to safe work during excavation:
* Work planning
* Location and identification of buried services
* Safe excavation
But not everyone follows the advice. Figures show that around a third of construction workers do not check underground power cables when digging on site.
Below are five tips to give you a head start when digging in built-up areas.
- A project that involves digging through city streets should begin with meticulous research. Preferred route design includes requesting utility drawings. It is also crucial to take the time to walk the route, as this will provide a clear view of any potential physical challenges in the area. A site visit can help identify workplace hazards that may not be shown on the drawings. This is much more common than many people realize, as the designs rarely keep pace with the addition of the road alignment, new street furniture, pipes and cables. More worryingly, there are rogue contractors who lay cables and services with no regard for the safety of others who may have to work in the next area.
- Planning and control: Although we can use a CAT 4 Plus scanner to track electrical cables, it does not provide accurate depths. If the cables have been laid incorrectly, it can be very dangerous for anyone working on the project. We have seen high voltage cables laid at 180mm when the depth should be 750mm. Planning and checking literally saves lives. In theory, it might be possible to use modern technology such as ground-penetrating radar to map cables and pipes under the streets of London. But, aside from the cost of this project, the map would also soon be obsolete as things change almost every week. So we rely on everyone in our industry to work safely and keep good records, which isn’t always the case.
- Give it enough time. We are all aware that our projects are more and more rushed. Working anywhere in London is a challenge as road access permissions may come from more than one local authority and involve Transport for London (TfL). None of these agencies want to close the city’s roads for very long. As a result, the excavation contractor is likely to have limited time and space to complete the work, and this is often when safety takes a back seat.
For example, the area allowed for digging may be very restricted on a busy road. Ideally the contractor should work 500mm on either side of a cable to avoid contact. But if a cable is very close to the edge of the allocated work area, it might be tempting to lift the tarmac, “just to see what’s there”.
This is when accidents can happen. It is essential to take the time to stop the work and assess how to proceed to undertake the work safely (extension of the work area, or extension of the permit even if this seems counter-intuitive). Planning ahead means decisions aren’t left to a time-pressed site manager who might make the wrong decision with the best of intentions.
- Advance planning and evaluation of proposed routes can highlight danger zones and these potential problems can be controlled by instructing excavation crews on how to investigate (no-dig zones). These clear instructions reduce the risk of the wrong decision being made for the best of intentions due to perceived pressure from excavation crews.
The need to search the streets of our cities is growing. As new buildings are constructed, they require the utilities that are essential to modern life. In addition, the government is encouraging the development of low-carbon district heating systems in urban areas, which will add to the challenge as new pipes are laid.
- As electrical contractors, we know the importance of prioritize safety for us and our customers. With the increase in accidents in excavation projects, it is time to focus on ensuring that contractors adopt strict safety standards on city streets.
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* Link to HSE’s HSG46: https://www.hse.gov.uk/pubns/books/hsg47.htm