With tales of water tables rising, and more and more reports of flooding around the world, the integrity and performance of preventive structures like the Thames Barrier are more important than ever. Melyvn French provides an overview of how safety – and particularly fire safety – is ensured at London’s flood defender.
The Thames Barrier is a unique installation across London’s river at Charlton, in the south east of the city. It has been operational for nearly 30 years and is there for one purpose and one purpose only: to keep the capital safe from flooding caused by surge tides.
If London did flood, 1.25 million people’s lives could be at risk, property valued at £200 billion could be lost, or severely damaged, and billions of pounds worth of trade, commerce and fiscal enterprise would be thrown into chaos. Infrastructure, utilities, transport (particularly the London Underground network) and tourism would all be totally disrupted.
So, the Barrier plays an absolutely vital part in the defence and safety of London; typically, it is used three to four times a year, when tides driven by other climatic forces threaten the life and work of all who live in the world’s 16th most populous city.1
The 520m-long Barrier is an exceptional feat of civil and mechanical engineering. Built in the late 1970s, it was the concept of an engineer called Charles Draper. In addition to the main structure (six steel gates and nine concrete piers), there are several other relatively smaller gates (known as associated gates) and some 195km of flood-defence banks. The whole system is currently operated by the Environment Agency.
When the Barrier is in defence mode the water it blocks has to go somewhere, so residents and life down river are protected by secure walls and embankments. These, too, have to be checked and, if necessary, enforcement staff will take action to ensure property owners maintain their frontage in a good state of repair and do not do anything to compromise the integrity of the flood defences.
For the Barrier to remain 100-per-cent operational 365 days year a very large plan of operational checking, servicing and maintenance is followed. The planned maintenance tasks are computer generated and controlled by a planning department, which constantly issues work instructions as to what has to be checked, and monitors the returned reports.
Around 100 people staff the Barrier, the majority carrying out engineering roles and tasks. Personnel are rotated on 24-hour standby to be ready to come in if the gates need to be closed. (Between 1982 and 2010, the gates were closed 114 times to prevent flooding.)
Smoke on the water
As a place of work the Barrier is fairly unique but it entails many of the health and safety issues that are common to most workplaces, such as slips and trips, manual handling, and use of chemicals. The more specific situations arise generally from access requirements, such as walking along tunnels under the river bed, getting to and from the various levels via stairs and lifts, and working in confined spaces.
One of the biggest risks in the Barrier environment, however, is fire, which can be caused by system faults, failures, or overheating of electrical systems and components. While the Barrier is essentially made of reinforced concrete, it houses miles of cabling, as well as myriad hydraulic systems and oil-storage tanks.
Prevention
With any tunnel system, fire is likely to spread along the length until it can find a way upwards – the chimney effect; at the Barrier, the piers essentially act as chimneys. Consequently, when a fire alarm is activated, the tunnels are automatically compartmentalised, via fire doors that close throughout the access tunnels. All other doors within the piers are either self-closing, or automatically closing. Extraction and ventilation systems are in place in the tunnels, while elsewhere on the Barrier site there are automatic/manual ventilation systems.
Various other systems work together to prevent fire occurring, including:
- regular maintenance and inspection of all doors associated with fire control;
- portable appliance testing;
- continuous inspection and maintenance of all fire engineered systems;
- regular testing of fire-alarm and detection systems;
- control of contractors – induction courses and permit-to-work systems;
- separate and purpose-built welding bay;
- locked and bunded storage of oils and chemical substances;
- high-security access and 24-hour security patrols;
- a very high standard of housekeeping;
- regular thermal imaging of large cables and equipment for hot spots; and
- regular visits by the local Fire and Rescue Service so they are familiar with the Barrier layout.
Detection
Smoke detectors are in place throughout the site, with heat detectors also, in one or two areas. There are also optical-beam detectors in the large workshop. Break-glass points around the site are all connected to monitors in the control room, which is manned 24/7. All cabling racks in the tunnels are fitted with a linear heat-detecting system.
Once a fire has been detected, the evacuation alarm is sounded immediately, along with a site-wide Tannoy instruction for all personnel to evacuate the site to the relevant assembly points (because of the size and location of the Barrier, these can be on either side of the river). The access security system provides an automatic roll-call print out.
Extinguishing
There are many miles of water piping installed throughout the land-based site and the Barrier itself to supply hydrants, sprinklers and deluge systems. Gas-flooding systems, originally using halon, were installed to protect all the transformers and switch rooms. These systems have now been updated, with an Inergen system replacing the halon.
On site, there are standby generators and these are enclosed so that a foam/carbon-dioxide system can be activated to deal with any fire in this area.
Emergency services
The local Fire and Rescue Service is only two to three minutes away; of course, there is a contingency plan as to the type and number of appliances required to attend (including the Fire Boat from the Albert Embankment, upriver). The Access Fire Plan is currently being upgraded to provide 2D and 3D drawings for use by fire officers.
Because the piers are relatively isolated in the middle of the river, reaching and evacuating any casualties can be difficult. Although both the Fire and Ambulance Services are located close to the Barrier it can take more than 15 minutes from arrival at the gate to actually being escorted to the point of the incident.
There is also the Barrier Emergency Rescue Team (BERT), which has been specially trained to work in the confined spaces of the barrier gates. This team is also trained to deal with other incidents, such as lift entrapment, spillage/leakage, suspension from a fall-arrest harness, as well as personal-injury accidents and stretcher transport. (Incidentally, the Fire and Rescue Service regularly uses the Barrier tunnels for training personnel in the use of long-duration breathing apparatus.)
Go with the flow
The Barrier operates a fairly flat management structure, consisting of the Barrier manager and team leaders. The team leaders meet monthly, and fire, health and safety are always on the agenda. Health and safety responsibilities are delegated to the relevant team leaders, and the site has a rolling health and safety action plan, to which all employees are invited to contribute. There is a formal health and safety action group meeting once a quarter, and monthly site inspections are carried out by safety reps.
Site rules, risk and COSHH assessments, and technical information sheets are reviewed on a regular basis. Strict permit systems – including those for access, isolation and confined-space work – are in place, with some permits only being able to be authorised by one or two people. There is a yearly audit of specific areas – the most recent, for example, focused on chainsaws, DSE and LOLER. All accidents and near misses are investigated thoroughly, and reported through a group system. All reports require a management action before they can be locked off and closed. These are reviewed on a monthly basis.
Training and refresher courses are very much encouraged and can cover COSHH, confined-space awareness, fork-truck driving, working at height, first aid, and dealing with conflict (that last one is particularly aimed at inspection staff, who can find themselves at odds with owners of embankments, who are often reluctant to maintain their waterfronts to the required standard!)
Conclusion
The Thames Barrier may be a London landmark and icon pointed out to many a tourist but, in reality, it is an absolutely vital national asset that will keep London and its inhabitants and workers safe from flood conditions. Should the day come when it is needed, it must be fully functional and operational; there is no room for error.
Achieving and maintaining this peak of operability requires a dedicated team of engineers and technicians, who must have safe conditions in which to work and use their skills. The Thames Barrier prides itself on continually assessing, reviewing and updating its fire, health, safety, and environmental management to meet these demanding standards.
Reference
1 www.nationsonline.org/oneworld/
bigcities.htm
Melvyn French recently retired as fire, health and safety manager at the Thames Barrier.
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