Businesses act in attempt to keep London dry
Groundwater levels in London vary from 10m to 40m below ground level reaching the highest point in the east in such areas as Woolwich and Barking. It is estimated that by 2010, if nothing is done, the water table will be between 20m and ground level in areas of Westminster and the City of London. Lis Stedman investigates what London businesses are doing to solve the problem.One thing few people appreciate when looking at the bustling metropolis of London is that back in the days when the city was little more than a gleam in the eye of the local peasants tending their turnip patches, a fair percentage of the land around the Thames was swamp.
All of this activity sufficed, until quite recently, to ensure that the water table beneath London remained at a respectable distance beneath the city. But since the 1960s there has been a marked change in the amount of abstraction, coinciding with the move away from the type of heavy industry such as cloth making and steel production which use vast quantities of water. And along with the reduction in abstractions has come a swift and seemingly inexorable rise in groundwater levels. In 1905, the water table was 100m below Trafalgar Square.
By the 1950s it stood 80m deep and today, it sits just 40m below Nelson's Column. In general, groundwater levels in the capital now vary from 10m to 40m below ground level, reaching their highest point towards the east in such areas as Woolwich and Barking. It is estimated that by 2010 if nothing is done the water table will return to its natural level of between 20m and ground level in areas of Westminster and the City of London. Water levels are currently rising by over 2m a year, and even now are posing a serious threat to the deep structures and foundations of tall buildings. The alarm was initially sounded by London Underground back in 1990, says a spokesman. "We carry out a continuous risk assessment, and in the early 1990s it became clear that rising groundwater was the single biggest risk to customers, through flooding or malformation of structures."
As a result of this London Transport undertook two major initiatives one being the inauguration of General Aquifer Research and Investigation Team (GARDIT) in 1992. GARDIT is an association of interested parties determined to find a solution to this increasingly pressing problem. Members include the Association of British Insurers, the British Property Federation, BT, the Corporation of London, the Environment Agency, the Government Office for London, London Underground, the Metropolitan Water Company and Thames Water. In those early days London Underground took the lead role, with one of its engineers, Mike Gellatley, chairing the group. "We took the lead when it was formed because we had the greater urgency, so we were the driving force," LUL said.
London Underground¹s other major action was Operation Hard Hat in the mid-1990s a vast £100 million programme of engineering works intended to provide a final solution to the problem of water ingress into the tunnel system. "There are no problems where the Underground runs through London Clay," explained the spokes-man. "But where the tunnels come out of the clay we had to make them waterproof."
Waterproofing was a mammoth undertaking one example was the eight-month closure of the Bakerloo line between Embankment and Westminster while a watertight concrete box was built around the tunnels under the Thames. This work was finished two years ago, and the last element in the scheme, to protect sections of the East London Line, ended a year ago when the line finally returned to normal operation.
London Underground is now also confident that it can ensure any new station built below the groundwater table is safe from problems the North Greenwich station on the new Jubilee Line Extension was built by excavating a huge hole in the ground, pumping it dry and building a massive watertight concrete box to contain three platforms and a station.
The ground was then packed back around the box and the groundwater level allowed to rise engineering calculations had predicted exactly the amount of pressure the groundwater would exert on the various parts of the box, allowing the contractors to work with the groundwater rather than against it. As expected, the corners on which the most pressure was applied rose, by the amount calculated into the exact final alignment which London Underground had planned.
With all its works finished, London Underground left Thames Water to take the lead role in GARDIT. The result of this is the new action plan announced last month (March) by Thames's chief executive, Bill Alexander, who is now the chairman of GARDIT's steering group.
Thames has pledged to create a network of 50 new boreholes to solve the problem, and has already invested £8 million opening four boreholes on the outskirts of the capital, including two at Streatham and Merton in the south west, with more under way at Battersea, Brixton and Islington. A borehole at the Millennium Dome will mix the groundwater with water from the Dome's roof to flush the toilets on the site, as part of a plan to make the Dome a showcase for water efficiency. Thames estimates that the finished scheme will be able to abstract up to 70 million litres of water a day from beneath the capital, with a third usable for drinking.
Potential uses for the non-potable water include ornamental ponds and fountains in parks. Thames has argued that other organisations and companies that will benefit from its abstraction programme should help with the funding - annual running costs alone are estimated at £2 million. Jeremy Bryan, managing director of water competitor Enviro-Logic - which has created the Metropolitan Water Company specifically to exploit the groundwater problem sees things a little differently.
Enviro-Logic has been involved in GARDIT for the last 18 months and feels the rising groundwater is something that can be actively exploited commercially. He attended a GARDIT meeting with Nick Raynsford, minister for London, 18 months ago, which was sparked by a letter from GARDIT warning of the consequences if the groundwater problem was not tackled as a matter of urgency.
Thames put forward its argument for others to help with the costs at that meeting, Mr Bryan recalls. "I upset the consensus - I said this is crazy, we can sell this commercially, we don't need someone to subsidise us. It is a pretty good commercial prospect." Mr Raynsford suggested that Enviro-Logic and Thames settle a solution, he relates, and the result is an agreement to undertake a two-pronged attack. Thames will develop its boreholes as far as it can to feed into the supply, and Enviro-Logic will seek opportunities for commercial exploitation.
"There is conceivably a third element if water is taken out where there is
no customer, when there may need to be financial intervention. But my
suspicion is that this won't be necessary." He feels that customers will be
attracted by the opportunity to make savings on their water bills and as a
bonus helping to save London from its rising groundwater. The market, if
fully exploited, could be worth £15 million a year, he estimated. "I'm not
for one second claiming we can get all of that but I would certainly like
to. I will get as much as I can," he promised. London may remain dry yet.