DELAYS IN closing massive underground steel flood barriers are thought to have led to August's catastrophic flooding in Prague's Metro system.
Two thirds of the system was paralysed following flooding of 18 or more stations, bringing the Czech capital to a near stand still.
The widespread inundation also led to mass evacuations, building collapses and widespread infrastructure damage of the city's historic centre.
The metro tunnels are fitted with massive steel barriers, designed by Soviet engineers to withstand nuclear bomb blasts.
These should have been able to hold back pressures many times greater than that exerted by the 30m head of flood water, said Petr Vozarik, technical director of specialist Metro contractor, Metrostav. It was initially thought that human error was to blame.
Lead-lined steel doors are fitted inside the tunnels at either end of each Metro station and in some, further blast protection barriers of lighter construction were installed between ticket hall and platforms.
These were designed to remain standing under a 10m head of water which would exert a force of 10kN/m 2. In the event support frames gave way when water reached 10m.
It is widely rumoured that metro staff did not close the barriers fully, to keep the city's population moving as long as possible.
But the scale of flooding took many officials by surprise. Initial modelling forecast the River Vltava would reach a one in 20 years return height. This was subsequently raised to one in 50 years and then one in 100 years.
The Vltava overtopped even this, submerging Prague's streets in more than 2m of mud-laden water.
Across all sectors, the government is having to spend large sums on stabilising or replacing low grade structures, said Mott MacDonald Praha managing director Jiri Petrak.
It is also feared maintenance has been neglected, possibly resulting in corrosion.
After fire crews and Metrostav workers pumped out the waterfilled Metro tunnels, it became clear that water had rushed in with devastating force, stripping away mechanical and electrical equipment in its path.
It is expected that cleaning and repairing damage will take months - few expect it to be operational before spring 2003.
Loss of the Metro, on which around 2M journeys are made every weekday, has forced people into their cars, grid-locking the already over-laden roads.