Heathrow Tunnel (Hansard, 27 October 1994)

§ Mr. Dover
To ask the Secretary of State for Employment (1) what steps he has taken to satisfy himself about the health and safety aspects of the tunnelling techniques being used for the Jubilee line extension near Heathrow airport; if these have previously been used in clay substrata; and if he will make a statement on these matters in relation to risk to lives and adjacent buildings;
(2) if he will make a statement on the collapse of the Heathrow express tunnels adjacent to Heathrow airport.

§ Mr. Raynsford
To ask the Secretary of State for Employment (1) what tests were carried out on the suitability of the new Austrian tunnelling method for London ground conditions before approval was given to use this technique on both the Heathrow express and Jubilee line extension projects;
(2) what steps are being taken to reinforce those sections of the Jubilee line extension and the Heathrow express projects being built using the new Austrian tunnelling method;
(3) if he will list the transport projects in which the new Austrian tunnelling method is being used in the United Kingdom, identifying the specific areas affected;
(4) what steps are being taken to prevent the risk of further subsidence at Heathrow central terminal area;
(5) What evidence he has of ground movement at any of the other sites on Heathrow express and Jubilee line extension projects being built using the new Austrian tunnelling method;
(6) what checks have been carried out on the Jubilee line extension tunnels being constructed using the new Austrian tunnelling method following the collapse of the Heathrow express tunnel;
(7) what trial bores using the new Austrian tunnelling method in London clay were undertaken before its adoption for sections of the Heathrow express and Jubilee line extension projects;
(8) what has been the effect on the Piccadilly line of the collapse of the Heathrow express tunnel;
(9) what evidence his Department has received on the cause of the collapse in September 1994 of the tunnel in Munich being constructed with the new Austrian tunnelling method;
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(10) when he expects to receive a report on the causes of the tunnel collapse at Heathrow on 21 October; and if he intends to make this report available to the public;
(11) when he expects the Piccadilly line between Heathrow terminal 1, 2 and 3 and Heathrow terminal 4 to resume normal service;
(12) what evidence he has on (a) the use of the new Austrian tunnelling method in ground conditions similar to those which exist in London and (b) the number of failures which have occurred;
(13) if tunnelling work involving the new Austrian tunnelling method has been halted on the sites in the United Kingdom where this method is being employed; and what conditions have been set with regard to the resumption of such tunnelling work.
(14) what investigations and checks were made by his Department into the safety of the new Austrian tunnelling method following the collapse of the Munich tunnel in September 1994 and prior to the collapse of the central terminal area tunnel at Heathrow.

§ Mr. Tony Banks
To ask the Secretary of State for Employment what will be the impact on the construction times and costs to the Heathrow express link and the Jubilee line extension arising from the Heathrow tunnel collapse.

§ Mr. Oppenheim
I have consulted my right hon. Friend the Secretary of State for Transport following the partial collapse of tunnels under construction at Heathrow airport.
In the early hours of Friday 21 October a ground slip led to a partial collapse into tunnels under construction on a section of the Heathrow express rail link at the central area of Heathrow airport. This section of the work involved the use of the new Austrian tunnelling method—NATM—in a complex of tunnels for a new station.
There were no injuries as a result of the collapse. Site safety procedures included sensors to detect ground movement. These gave early warning of abnormal movement. Emergency procedures were put into effect and workers were safely evacuated. There were two further ground slips over the weekend. They were almost certainly as a consequence of the initial event.
The contractors and their specialist advisers have set up an engineering task force to deal with the situation. Tunnelling has of course been stopped. The key task now is to stabilise the ground to prevent further subsidence and secure the safety of the remaining tunnels. The British Airports Authority and the contractors are working together to secure the continued safe operation of the airport and minimise inconvenience.
At the place where the Piccadilly line crosses the Heathrow express rail link tunnels, there has been no ground movement outside of the tolerances predicted before tunnelling began. The monitoring continues. London Underground has, however, suspended the use of the terminal 4 loop as a precaution. The central station serving terminals 1, 2 and 3 continues in service. A temporary bus link is connecting Hatton Cross station and terminal 4.
NATM has also been adopted for use on the Jubilee line extension project. Contractors on the project suspended the use of the NATM technique as a precautionary measure on the day of the collapse at Heathrow.
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The Health and Safety Executive has asked for tunnelling not to restart at Heathrow, nor on the Jubilee line extension project, until it is clear that this can be done safely. The Health and Safety Executive has also asked London Underground to maintain its voluntary suspension of the railway loop until sufficient information is available to justify its safe restoration. The decision will be made in conjunction with HSE's railway inspectorate. HSE's inspectors are on site and keeping in touch with developments in the major remedial works undertaken by the contractors. The HSE is initiating checks of other significant construction projects currently using NATM.
NATM is a tunnelling method that has been used worldwide for over 40 years. The two largest projects under construction in the United Kingdom using NATM are Heathrow and the Jubilee line extension. A trial tunnel was driven at Heathrow in 1992 and the information and experience gained was used in developing the project. Further trials were carried out at London Bridge and Jubilee Gardens at the start of the Jubilee line extension project.
NATM is normally the first stage of a two-stage process involving the construction of a initial lining to provide short-term support followed by the construction of a further lining. There is no evidence that, once the work is finished, there is any significant difference between the safety and integrity of tunnels constructed in this way and those using more conventional techniques.
There was a failure, also during the construction phase, in Munich earlier this year. However, because the ground conditions were considered sufficiently dissimilar, there were no reasons to justify halting work in London. There have been no recorded instances of ground collapse once the construction phase of the tunnelling using NATM is complete.
The Health and Safety Commission has asked the Health and Safety Executive to undertake an investigation. The HSE has asked Mr. Stuart Nattrass, HM chief inspector of construction, to lead it. He will be seeking support from independent consultants of international standing. The investigation will initially concentrate on whether the failure at Heathrow is site specific. Once the initial findings are known, the investigation will go on to consider whether there are broader implications for the use of NATM as a construction technique. The evidence will be reviewed with a view to confirming that the safety of tunnels constructed in this way matches the safety of tunnels constructed using more conventional techniques and will take into account any lessons to be learned from the Munich incident.
Initial lines of inquiry will include whether:

(a) the design was defective;

(b) the execution of any construction work was defective;

(c) adverse ground conditions contributed to the failure.

The investigation has begun. Its findings will be made public. The HSE will consider whether there may have been breaches of health and safety legislation and, if so, what action to take.
It is too early to predict time and cost penalties which may result for the Heathrow express and Jubilee line extension as a result of the collapse on the Heathrow project.