On 24 March 1999, at around 11 a.m., a refrigerated lorry carrying 9 tonnes of margarine and 12 tonnes of flour began to burn inside the Montblanc tunnel. About 2 kilometres from the Italian entrance, when the smoke was already thick, the driver stops the lorry in the central area of the tunnel, approximately 6 kilometres from the Italian entrance and 6 kilometres from the French entrance. Within seconds, the lorry explodes. Because it’s a bi-directional tunnel, a queue of vehicles forms on both sides of the burning vehicle. Alarms are activated and the tunnel is closed to traffic in both directions, but 25 vehicles with 39 people inside are already stopped or driving towards the burning lorry from the French side. The smoke is heading towards the French entrance. In barely half an hour, the smoke travelled the 6 km distance and exited through the French entrance, partly aided by the mechanical ventilation that was activated by workers on the Italian side.

Several rescue attempts are made, but all are unsuccessful. The fire lasts for 53 hours. Once the blaze had been put out, firefighters entered the tunnel and, sadly, found 39 victims. All had died in the first stages of the fire due to smoke inhalation.

Two years later, on 24 October 2001, there was a collision between two lorries inside the Gotthard Tunnel, which links Italy and Switzerland beneath the Alps. A few minutes after the collision, a large fire breaks out and temperatures inside the tunnel exceed 1,000°C. The fire burns for 20 hours and causes part of the tunnel to collapse. When rescue services enter, they find 11 victims.

The company has also carried out other work such as risk assessments for 42 tunnels located on the Trans-European Network

Safety requirements in Spain

Following these accidents, the European Commission decided to draft legislation on safety measures in road tunnels for all its Member States. Therefore, on 29 April 2004, the European Parliament and the Council adopted Directive 2004/54/EC on minimum safety requirements for tunnels in the Trans-European Road Network.

Although this directive applies only to tunnels located on the Trans-European road network, when transposed into Spanish law by Royal Decree 635/2006, of 26 May, on minimum safety requirements in State road tunnels, no distinction was made between tunnels located on the Trans-European Network and other tunnels, in the belief that they should all have a similar level of safety. The royal decree also increases European safety requirements, so that all tunnels currently operating on Spanish roads are affected by the regulation in one way or another.

In 2016, the Directorate-General for Roads entrusted Ineco with the drafting of the first projects, which included the development of the Tunnel Adaptation Plan as the first assignment. There are a total of 354 tunnels on Spanish roads, of which 41 are on the toll road network and another three belong to the first-generation highways, all of which are managed under concession contracts. The remaining 310 belong to the network managed directly by the Directorate-General for Roads.

Following an analysis of the equipment of these 310 underground tunnels, it was concluded that 118 already meet the minimum safety requirements set out in the Royal Decree, and therefore the remaining 192 tunnels require attention. Of these, 90 are located on the Trans-European Network and 102 on other state roads.

Work on the 192 tunnels, which are being brought into line with European regulations, is expected to be completed in 2026. / PHOTO_INECO

Among other works, Ineco has drafted 22 adaptation projects, which include a wide variety of actions: road signalling, the installation of traffic lights, variable messaging panels, road surface improvement treatment, ventilation, upgrading of SCADA, CCTV and DAI, environmental control systems, fire protection systems, radio communications, public address systems, electrical installation, toxic liquid drainage, new emergency galleries, waterproofing and soundproofing improvements.

A further 21 projects were awarded in three lots to different consultancy firms. Ineco also provides support to the MITMA (Ministry of Transport, Mobility and Urban Agenda) in the drafting of tender specifications, bid evaluation and the preparation and review of study orders and subsequent modifications. As the Adaptation Plan progresses, some projects are being sub-divided in order to accelerate the tendering of tunnels falling within the scope of European Directive 2004/54/EC (tunnels longer than 500 metres located in the Trans-European Network).

In April 2021, Ineco began a new project to bring the Xeresa and Mascarat tunnels into line with the royal decree. Of the 53 tunnel projects on the road network managed directly by the State, Ineco is in charge of 32, involving a total of 104 tunnels.

The company has also carried out other work over the years, such as risk assessments for 42 of these Trans-European Network infrastructures. The objective was to assess, in accordance with the Ministry’s Risk Analysis Methodology, whether these tunnels could be classified as safe, or whether any additional measures were required. Once the improvements have been implemented, all of these can now be considered safe, on the basis of this methodology.

Two new tasks have been added to Ineco’s activities in the Tunnel Plan, which is scheduled to last until November 2022. Firstly, the control and monitoring of some of the works and secondly, the drafting of a plan to improve energy efficiency in the lighting of tunnels on the state network.

The work to upgrade the 192 tunnels is expected to be completed in 2026, after a major investment of more than 500 million euros. Once completed, the time may be right for a new plan, with the aim of converting the tunnels into smart infrastructures, thanks to new technologies and materials, connecting them to future autonomous vehicles, which, together with 5G, will become a reality in the next few years.

When the new commuter rail access is completed and operational, it is estimated that between 8 and 9 million passengers will be able to use it to travel from Sants station to Barcelona-El Prat Airport’s terminal T1 in just 19 minutes. Until now, the commuter rail line (known locally as Rodalies) only reached the old terminal, T2, where a new underground intermodal station is currently being built.

With the excavation of the final metres of the 3,400-metre tunnel –3,048 metres of which were excavated using a TBM– in December 2018, one of the major milestones of the works, which began in 2015, was achieved. This first phase, for which Ineco was commissioned by Adif to carry out site and environmental management, will conclude when the works on the new intermodal station and shafts are completed. The next step will be to install and equip the tracks, power supply and railway facilities and commission the two new stations, projects on which Ineco is also working.

The new double-track stretch starts on the Barcelona-Tarragona conventional line, and runs to terminal T1, with an intermediate stop at terminal T2, where it will connect to Metro Line 9. The access includes a new station at terminal T1, not included in this project (the civil works were executed during the construction of the terminal itself). According to Adif, it is the largest project of its kind in terms of scope and budget currently being carried out on Spain’s conventional and commuter rail network.

Underground challenge

Excavating a tunnel with an enormous tunnel boring machine through ground with low bearing capacity –Barcelona Airport is located on the delta of the Llobregat River, meaning that terminal T1 had to be built on a gigantic concrete caisson– and under a large building (terminal T2) and runway that operates 24 hours a day, was no easy task.

Ineco drafted the construction project in 2009 taking all of these factors into account. To resolve the issues of soil quality and presence of a shallow water table (just over 2 metres), ground improvement treatment was carried out: a total of 126,802 m³ of ground was jet grouted (soil improvement using high-pressure reinforcement material) and 4,410 metres of micropiles were installed.

For the excavation, an earth pressure balance tunnel boring machine (EPBTBM), with earth pressure balance shield and 10.60-metre excavation diameter and 9.60-metre internal diameter, was chosen. The tunnel, which is lined with 32-cm thick concrete segments, has a maximum depth of approximately 28 metres and was executed between 56,700 m² of screen walls.

In the end, the excavation was completed with no significant subsidence on the surface. Special care had to be taken under the T2 building, where the TBM had to manoeuvre between foundation piles with a margin of just over one metre, and, under the runway, which Aena decided to close for 20 days in order to excavate a 300-metre section below it. In addition to hydrogeological and geotechnical studies prior to the beginning of the works, during excavation, a sounding system, consisting of more than 3,000 devices, was installed, including automated systems to monitor the stability of the ground and construction at all times.

The new stretch starts on the Barcelona-Tarragona conventional line, and runs to terminal T1, with an intermediate stop at terminal T2, where it will connect to Metro Line 9

Environmental works management

Ineco was also in charge of environmental works management to ensure compliance with the project’s environmental impact study (EIS) during the different phases of the work and after acceptance.

From the environmental point of view, the most notable aspects were monitoring impact on the hydrogeological system of the area, consisting of two aquifers, one deep and the other on the surface, management of anthropic landfills (soil containing waste) found in some areas and corrective measures to avoid noise disturbances.

To supervise the hydrological system, in 2012, before the start of the works, a network of 14 piezometers was installed (nine in the surface aquifer and five in the deep one, which supplies part of the city of Barcelona) to learn about the aquifers’ charging and recharging processes. Monitoring of the piezometric levels and water quality carried out previously and during the execution of the works will continue for two more years, once the civil works have been completed, in accordance with the requirements of the Catalonian Water Board (ACA). The application of preventative and corrective measures, together with the above monitoring, has minimised the potential impact of the works and reduced the risk of the tunnel affecting communication between the aquifers, causing contamination and creating a drainage barrier effect.

The anthropic landfills found in the area of emergency exit No. 3 (Vidaleta shaft) were examined, sorted and transferred to the appropriate waste management centres. To address noise issues, temporary acoustic screens were installed near a hotel and tennis academy located next to the construction site.

Tunnel boring, the construction of access ramps and the building of the multimodal station generated large volumes of excavated earth, which, in accordance with the EIS, was collected and removed and will be reused on other projects such as works on the port of Barcelona and the regeneration of two nearby quarries located in the municipality of Gavá. All removed soil containing vegetation was also reused later to restore any affected areas to their former state.

Excavating below the water table also required the drainage and collection of excess water (effluents), which were then treated and purified before being discharged into either the public water system through the airport’s drainage network or storm drains or reused on construction site roadways to reduce dust. To ensure the quality of the air, filters were also fitted to lime, bentonite and cement silos, and sprinkler systems were installed in the concrete plant to clean machinery before leaving the site. All works waste was collected, sorted and disposed of appropriately.

Regarding the protection of cultural and natural heritage during the works, no archaeological remains of interest were found and none of the local animal life was affected.

The works continue

Ineco is also participating in the second phase of the works, for which it is drafting the project of necessary actions for the operational readiness of the new commuter rail access. These works include connection to the main line, track superstructure, electrification, telecommunications, facilities inside the tunnel and design of the stations at terminals T1 and T2.

The drafting of the project needs to consider certain specific conditions that affect both the design and the execution of the works, such as ensuring that connection to the existing line does not affect its operation. The tunnel evacuation plan will need to take into account that the T1 and T2 stations are separated by more than one kilometre, but an evacuation exit cannot be built because that section of the tunnel runs under the airfield. The T2 station will have to be compatible for use by passengers from both the Metro and the commuter rail, and in the T1 station, the design of the emergency exits and fume extraction system will be subject to the conditions imposed by its location in the air zone.

Lastly, the security facilities will be considered by Adif.