The reconstruction

In order to allow the Mont Blanc Tunnel operation to start up again, the concessionary companies (the Italian SITMB and the French ATMB) put forward a “General programme of repair and updating”, in collaboration with the Public Services, so as to guarantee the highest levels of safety to users of the Tunnel. This programme, approved by the Intergovernmental Commission 1 (CIG) on 14 December 1999 after obtaining the view of the Safety Committee, 2 incorporates the 41 recommendations formulated in the Marec-Cialdini report and in fact corresponds to the new requirements concerning tunnel safety (European Directive 2004/54/CE). The programme is divided into four essential points:

  • reconstruction of the safety systems;
  • reinforcement of the emergency services;
  • creation of a single operating structure;
  • the writing of new traffic regulations.

Preliminary action

A preliminary assessment of the state of the Tunnel structure after the incident was carried out by means of investigation and surveys entrusted to specialized companies.

This activity (which was necessary and preparatory to tunnel planning and modernization work) took the form of measurements, geometrical surveys, ground-penetrating radar tests, core boring of the concrete lining of the roof, laboratory analysis of the core samples, chemical and biological analysis and flat jack point load tests.

To be able to get the above activities started it was essential first of all to proceed with making safe the roof, the side walls and the ventilation channels, as well as the slab covering these channels and bearing the road surface, in the stretch of tunnel directly damaged by the fire. Since these structures were in part found to be seriously damaged by the fire, it was necessary to set about making the worst affected parts safe, mainly by detachment of part of the roof concrete, stabilization of part of it by applying a metal mesh and shotcrete, shoring up the fresh air channels and the stale air channels, in order to allow transit, and the carrying out of all those remediation activities, and all the investigation and surveying activities, that had to be carried out on the structure in conditions of absolute safety.

Work was also carried out to dismantle pre-existing structures that the effects of the fire had totally or partly jeopardized, with a view to their replacement with more modern and suitable installations. This particularly concerned the existing side wall linings and the dismantling of the walls of the old shelters and the sign system.

It must be borne in mind that the Tunnel was substantially “stripped”, i.e. gradually emptied of the previously existing systems and fittings and reduced to the simple structures lining the tunnel and comprising the channels beneath the road surface together with the slab lying above them.

This was in view of the fact that the gradual definition of design indications for the different sectors, and the gradual start-up of the works relating to them, highlighted the opportunity and the need to modernize most of the structures and installations in the tunnel either because they were damaged or because they needed to be reviewed.

1 The Mont Blanc Tunnel is a cross-border structure and, as such, is placed under the trusteeship of an Intergovernmental Commission (CIG) formed in this specific case by Italy and France. Made up of representatives of the French and Italian governments, it is presided over by a diplomat. This body establishes the regulations for safety and traffic in the Tunnel and approves the tariffs. It also controls the execution of works needed to improve the operation and safety of the Tunnel.

2 This body was instituted in application of a decision of the CIG of 23/07/99 as a result of the fire of 24 March 1999. It consists equally of 5 French members and 5 Italian members, who are specialists in matters concerning protection, fire fighting and traffic movement in tunnels. The Safety Committee has the task of providing the CIG with a technical opinion relating to the above matters.

Furthermore, as a preliminary to the main works two operations were carried out:

  • the first (functional cleaning and decontamination) concerned treatment of the roof, side walls and flooring of the tunnel and the whole of the stale air channel with jets of water at high pressure and temperature and using special solvents, in order to clean and decontaminate the structures of corrosive agents; also, dry cleaning of the fresh air channels and the ventilation plant, as well as decontamination of the networks and fixed installations that were to be used for the work, and ordinary cleaning of those which were to be removed and taken to the waste disposal site;
  • the second (the so-called batch 0) consisted of the construction on Italian territory, near the tunnel entrance, of 3 garages, as well as lay-bys of 30 by 3 m positioned at intervals of 300 m alternately on both sides of the tunnel, with the consequent widening of this, in order to eliminate possible interference of these excavation works (which affected the whole section of the tunnel) with the works that were to follow. There must be added to this the partial construction of six new safe places, started in advance for the same reason.

The new safety features: technical measures

The primary safety objective was pursued by means of a series of technical measures, i.e. work carried out on the structures and installations, supplemented by organizational measures, i.e. action taken in the area of management.

Among the technical measures we must include the following :

  • Prevention systems
    • the installation of thermo-graphic portals for identifying and stopping vehicles that display abnormal temperatures, before they enter the tunnel;
    • the detection of risk situations inside the tunnel through video surveillance systems (consisting of 120 fixed television cameras, mounted on fixed supports in the roof of the tunnel in two rows, that watch the two traffic lanes, 36 fixed cameras, mounted in the lay-bys, together with the 37 cameras positioned in the safe places), systems for the automatic detection of accidents and traffic jams, failure to keep to the speed limit and minimum distance between vehicles, and systems for detecting temperatures, fires and smoke.
  • Ventilation, extraction and evacuation of smoke in case of fire, with a flow rate of 156 m³/s over a 600 m area
    • the positioning of remote-controlled shutters on the aspiration outlets (carneaux) every 100 m on the side next to the France-Italy lane;
    • the installation of 76 longitudinal ventilators placed in pairs in the roof for controlling the longitudinal flow of air;
    • the creation of a continuous system of ventilation and stale air conduits between Italy and France;
    • the possibility of activating simultaneously and promptly the two ventilation plants positioned at the tunnel entrances;
    • the installation of 4 supplementary ventilators along the aspiration channels to give better extraction of stale air.
  • Instruments and structures for getting people to safety and evacuating them, among which there are :
    • 37 safe places, one every 300 m, on the side next to the Italy-France lane, having a surface area of 37,5 m², preceded by a SAS of 5 m², overpressure ventilated and connected to pure air passages, that are used as an escape route, with access appropriately highlighted by specific signs and fittings ;
    • provision of an electric vehicle, both on the Italian and the French side, capable of moving along the ventilation channels used as an escape route, in order to be of help in the evacuation of any injured people or people with disabilities;
    • illuminated and tactile signs guiding people to the access point of the safe places (Arianne’s thread) positioned all along the side wall where the safe places are located;
    • 3 new garages (specially equipped lay-bys) near the Italian entrance, to ensure that these are present every 600 m throughout the tunnel, bringing the overall number to 36, positioned alternately on both sides of the tunnel;
    • safety booths every 100 m (116 in total), alternately on both sides of the tunnel, each containing: 1 interphone connected to the Control and Command Stations (PCC), 2 extinguishers with a use detector, electric points (220/380 V), a glass door with a door-open detector, and specific signs;
    • fire fighting booths every 150 m (80 in total), on the side next to the France-Italy lane, fitted with a double fire hydrant according to the standard for both Countries, with similar installations in the SAS of the safe places, and reconstruction of the fire fighting network fed by 4 tanks of 120 m³ each (fed by water coming from the capture of sources inside the tunnel) two of which are situated at the tunnel entrance aprons and two in the tunnel (at lay-bys 25 and 29).
  • Equipment for the technical and functional fittings, such as :
    • new road signs consisting of illuminated signs for better visibility;
    • new highly reflective road markings and acoustic road surface roughening;
    • variable message panels positioned every 600 m alongside the garages, with the possibility of showing pictograms and alphanumeric messages, using the most advanced technologies;
    • half-barriers for stopping vehicles in emergency situations every 600 m positioned alongside the garages and incorporating red stop traffic lights and alphanumeric variable message panels; these half-barriers are a very effective risk-reduction device that allows the traffic flow in the tunnel to be stopped by, every 600 m, keeping back vehicles which are heading towards the place of an incident;
    • reconstruction of the lighting system;
    • reconstruction of the communication and radio broadcasting system; the Mont Blanc Tunnel is equipped with two radiating cables, one in the roof, and the other protected in channel 4 under the road structure, which allow retransmission of operational communications from the tunnel management and of the Public Services radio frequencies. These radiating cables also allow 12 FM radio frequencies (6 French and 6 Italian) to be rebroadcast for the attention of tunnel users. In case of need, the operator in the command room can send out pre-recorded or live messages, to provide users with information about the nature of an incident, and instructions concerning how to behave;
    • replacement of the tunnel wall cladding with light-coloured panels;
    • rebuilding the electrical supply system with 9 substations for providing low voltage supply to installations, and two power plants (EDF on the French side and ENEL on the Italian side) that are capable of supplying the whole tunnel;
    • installation at the tunnel entrance apron on the Italian side of auxiliary generating units.

The new safety features: organizational measures and intervention tools

Among the organizational measures must be listed :

  • preventive actions to inform users and heighten their awareness about using the infrastructure, keeping to the limits set, and how to behave in case of emergency, that are carried out using the most up to date communication instruments, including radio broadcasting over dedicated channels;
  • one main command room for the whole tunnel (PCC 1, referred to as “active”, which is used for the unitary management of systems and the intervention teams in accordance with predefined procedures), and a secondary command room identical to the first (PCC 2, referred to as “traffic”, which is used for the unitary regulation of heavy vehicle traffic through the two regulation areas of Aosta and Passy-Le Fayet, and for communicating information to their partners and to the tunnel users), with the possibility of switching over from one to the other in case of emergency;
  • the traffic regulations, developed by a working party set up at the Franco-Italian conference of 29 January 2001, and approved by the Intergovernmental Commission, that defines the traffic standards;
  • the first aid plan (Internal Intervention and Safety Plan - PIIS) and the instruments for dealing with emergencies, put together on the basis of specific risk analysis; among these, the provision of three immediate intervention teams (one for each of the tunnel access aprons, and the third in a special newly created structure at the centre of the tunnel) specifically trained for intervention in confined spaces, and equipped with fire fighting vehicles specially designed and built for the Mont Blanc Tunnel;
  • The bi-national Rescue Plan (PSB), which is the fruit of collaboration between the Prefecture of Haute-Savoy and the Civil Protection of the Valle d’Aosta, if it should be necessary to have recourse to additional and more specialist intervention, beyond that provided by the resources present at the site;
  • Two areas for the regulation of heavy vehicle traffic heading for the Tunnel, in accordance with what has been established by the Intergovernmental Commission (CIG); heavy vehicles, before entering the Tunnel, must get clearance at the regulation and control areas of Passy-Le Fayet (France) and Aosta (Italy). Their conformity to the tunnel transit conditions is certified by a pass, issued after checks on the dimensions of the vehicle and the European pollution category (transit being prohibited for Euro 0 and Euro 1 vehicles, i.e. vehicles registered before 1st October 1996).