When are three collapses on the same tunnelling project not a sensation? When you are the mayor of Prague apparently.
Last month’s collapse during construction of the Blanka Tunnel Complex for the Prague ring road was the third reported since 2007, and yet the owner’s first real reaction, represented by Mayor Pavel Bem, was to blame journalists of ‘sensationalism’, whereas the more sobre assessment would be on their reflection of the legitimate concerns of citizens. As is usual when politicians are under pressure, especially in an election year and when intimately involved with a particular project, the media makes an easy target as a distraction from the real story. And Mayor Bem is certainly under pressure, for safety reasons now as well as for the cost of the longest city tunnel in Europe and the most expensive construction project ever undertaken in Prague.
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Before Tunnels & Tunnelling International attracts the likely accusations of some readers of not supporting the tunnelling industry by concentrating on bad news, or of the sin of speculation, let us say that, as a professional journal team, we are committed to finding the facts of what went wrong. In the absence of hard facts it is legitimate to assess likelihoods and to ask questions, as any investigation will do with, hopefully, greater resources than ours.
And there are plenty of questions to be asked, some of which the contractor Metrostav has already speculated upon in an official statement. These could include:
1) As the tunnel cover ranges 8-44m on this project, was the working depth too shallow, at least for the type of support and construction method chosen?
2) Since it has been said frequently that certain geological conditions were unexpected, should there have been more site investigation?
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By GlobalData3) Was the construction design faulty, and what was the real role of engineering designers and project managers to date, as Metrostav has to field most of the questions?
4) Should there have been additional ground stabilisation measures, especially near major structures?
5) Was there a human error in removing needed support, or on the part of supervisory management or advisors?
6) Were there any more than legitimate cost-saving measures in the tunnel support and safety inspections, as some leaked reports have indicated, and that a critical auditor no longer works for the city?
The official investigation seems unlikely to report for 2-3 months. The many investigations into collapses under NATM procedures, SEM or similar procedures have confirmed that close supervision of support, and support removal, procedures is essential. In the meantime, the fear of the unknown could well turn people against tunnelling, especially in urban situations.
What is needed is practical and rapid steps that may reassure the public, voters and guardians of city resources that tunnelling can and should be carried out safely under such circumstances. Rightfully the Czech mining authorities have stopped all but safety-essential work on the tunnel to carry out investigations, but more is needed to prevent a PR disaster, second only to BP’s, for Europe’s biggest urban tunnel project.
Ultimately, we may hope for some clear answers away from the fog of politics.
PS A joke doing the rounds is that the latest collapse is hole 3 on the mayor’s golf course. Nothing like humour to satirise a bad situation.
Maurice Jones
