The Project

The project consists of two tunnels of around 13.9 km long each, 72% of said length belongs to Argentina and the remaining 28% belongs to Chile. The road access is better appreciated by lowering its height from approximately 4,800 meters above sea level to 4,000 meters above sea level on the Argentinean side entrance and up to 3,600 meters above sea level on the Chilean side.

The form of the project has been made by professionals with a vast experience in studies and works on great length tunnels all over the world considering basic factors such as Geology, air circulation, position in the High Andes, financial evaluation and/or financing alternatives, among others.


Argentina and Chile share one of the largest binational borders in the world along with an amazing geographical obstacle as is the Cordillera de Los Andes. Not so long ago, there was only one adequate commercial route, which connected the macro area through over 4,000km long. It is unconceivable the growth of the regional development and a satisfactory physical integration of this area of the South American south cone considering such scarce good quality communication routes.

In comparison, from the time of the Colonization and maybe up to the arrival of the railroad, the communities from both countries, which were near the border held an intense economic and social interchange in some areas since the border was usually crossed on animal-powered vehicles, which were adequate for the magnitude of the transported loads. Simultaneously, with the increasing force of the railroad for the internal communication, both countries seemed to focus more on towards their economic connections overseas. Several decades ago, Argentina and Chile designed a system of border paths, granting priorities, making a paradigmatic effort of bilateral work in Latin America.

Nowadays, it is getting harder and harder to survive in a globalized world without a strong regional association, and not being part of a geopolitical block that empowers and complements us. There is a shared past, a mother tongue and economically speaking, comparative advantages that many other countries wish they had. It is imperative to accelerate the physical integration with works of different nature so as communication stops being the funnel that slows down a full integration. This way, the Túnel de Agua Negra is registered as a key works that will make The Bioceanic Corridor Porto Alegre- Coquimbo operative and transforms into a vital regional artery for the integration of this part of the South Continent.

Chile and Argentina have agreed on Paso de Agua Negra to receive preferential budgetary attention in order to improve. It is strategically located within a central stipe between both countries and was considered top priority regarding investment since it attracts traffic, which does not compete with the possible traffic adjacent paths. It is complemented with the Paso Sistema Cristo Redentor which connects Mendoza-Valparaìso. Once the Tunnel is built, it will help to ease the congestion at Paso Sistema Cristo Redentor during temporary closing due to winter storms. This can be explained as follows: even Agua Negra is higher than Cristo Redentor, snow precipitations is statistically three times inferior.

Developed countries such as Canada and The Unites States share large borders with many route paths suitable for commercial traffic. Said paths are note separated for more than 150 to 200 km in between which ensures a great flexibility of communication and competence in mutual interchange and with other countries as destination.

From the very beginning, Agua Negra has been a path used by the areas adjoining to both slopes of the Andes. In the 19thC, this was a route for cattle roundup to Chile and the entrance to many items to the Port of Coquimbo. The current route was opened to the public in the 1960’s and today, Argentina and Chile are transforming this route in a modern road surface suitable for transportation. This way, in Chile the route 41 CH goes down through the heart of Valle del Elqui and runs into La Serena and Coquimbo, crucial point of the Area of Coquimbo which holds an increasing touristic, mining, commercial, port and services activity. In San Juan, National Route 150 strategically crosses nearby rich metal deposits, lime production centers, privileged paleontological tourist centers. Through the East, it connects the roads that go through Córdoba and the Mesopotamia littoral, Argentinean industrial and agricultural exporting activity nodes. The Paraná-Paraguay-Porto Alegre waterway in the South littoral of Brazil are also and at the same time beneficiaries/taxpayers of this long bioceanic corridor which holds Paso de Agua Negra as a key link.

The idea of a tunnel in the Paso de Agua Negra was formally suggested in 1998 within the project of improving and paving the National Route 150 up to the international limit. The counselor in charge of the project pointed that a tunnel of 4.5km at the end of Quebrada de Agua Negra might prevent the ascent to the binational pass and obtain important benefits for the users and the administration. When this idea was shaped, in 2003 it was decided to hire a technical prefeasibility study to make clear which should be the most convenient works in order to cross the border. Over ten alternative possibilities which held different lengths tunnels from 4.5 to 24 km, were evaluated in a wide geographical area that covered most of the Quebrada de Agua Negra and Quebrada de San Lorenzo in Argentina and Valle del Río Colorado in Chile. In that occasion, the current alternative was selected, it included a tunnel of 14km approximately with entry ports in the Quebrada de San Lorenzo in Argentina and in Llano de las Liebres in Chile. The selected tunnel consisted of a main tunnel for bidirectional traffic circulation and a parallel tunnel with a smaller section for ventilation and emergency traffic circulation.

In order to gain more precision over some approaches taken in the studies of prefeasibility, a latter “Concept Study” in 2008 to deepen the topic of energy consumption regarding the artificial ventilation, the safety related to the traffic circulation in both ways of the same tunnel and the methodological constructive options. With this study it was decided that it was better to adopt two main tunnels, one for each way since it is more convenient, safer for the circulation as well as with better projection to the future. Specific ventilation channels were also foreseen, one in vertical position (chimney) in the Argentinean side and a horizontal one (gallery) in the first 4.5 km in the Chilean section. Both channels assisted by their respective ventilation stations. Later in time, basing on a conceptual study, a basic engineering development was hired. Said engineering should provide the potential interested parties in the building of the works with the basic elements to quote the work and develop a detailed engineering. By then, geological and hydrogeological evaluations, deep drillings with witnesses and geotechnical and lab tests, among other studies; had been performed in order to meet the conditions of the massifs along the trace.

The results of the basic engineering as well as the economic evaluation of the works were duly subjected to Chilean and Argentinean supervision, under current regulations of each country.

  • Two parallel tunnels, one for each way: descending from Argentina to Chile and ascending from Chile to Argentina. 13.9 km long. The Argentinean entrance is 4,085 meters above sea level and the Chilean entrance is 3,620 meters above sea level, which gives the tunnel a slope of 3,620 meters above sea level, which gives the tunnel a slope of 3.37%.
  • Separation between tunnels: vary between 40 and 50 mt.
  • Road internal sketch with curves of very high radius.
  • Roads of 7.50 mt wide, with both side spaces for pedestrian circulation and services. Height free of vehicle circulation of 4.80 mt. Transverse section typical of each tunnel: 70 m2.
  • Pedestrian galleries that connect both tunnel for emergency cases, are separated by 250 mt along the whole sketch. Vehicular interconnection galleries for emergencies every 1,550 mt.
  • Support/lining systems of the hollow spaces adapted to the geomecanical nature of the crossed massifs.
  • Sanitary ventilation for normal operation and and ventilation system for fire fumes extraction. Vertical ventilation dwell of 535 mt of excavation height and 4.5 mt diameter in the Argentine territory. Ventilation gallery of 4.75 km long and 36 m2 transversal section on the Chilean side.
  • Ventilation caverns in the ends of the previously mentioned dwell and ventilation gallery.
  • Hydrants for firefighting all along the tunnel.
  • Integrated Traffic Control Center to look after your safety and keep under control essential aspects for circulation such as sanitary ventilation, lightning and internal visibility.
  • Buildings with all necessary equipment for firefighters and rescue teams services next to the ports.
  • Road access separated in the influence areas of both ports.

For a much shorter tunnel, located at a lower altitude, probably just one tube would have been enough. Since the technical prefeasibility study from 2003 foresaw the need of an auxiliary tunnel due to safety reasons (for emergency escapes) and ventilation requirements. The 2008 conceptual study deepened the energy consumption analysis for the sanitary ventilation and recommended to transform the auxiliary tunnel of the prefeasibility report into a second main tunnel. This was made in order to have two equal tubes, one for each way of circulation. This way, more advantage is taken from the natural air circulation in the tubes, induced by height difference, barometric pressure and temperature between the ports – and the differentiated traffic circulation direction – in order to obtain significant savings from energy consumption. As important as the aforementioned is the safety provided to the users by saving 14 km of underground traffic circulation with vehicles coming in the opposite direction. In this case, drivers might be tempted to violate the prohibition of overtaking when driving behind loaded trucks that go slow. With two tunnels and one-way direction each, light vehicles might keep a good speed and are not delayed by heavy traffic taking the outer lane. This is the most important circumstance to prevent frontal crashes, an immense risk in two-way traffic tunnels.

As every significant engineering work, this tunnel shall be built with seism-resistant precautions in accordance with the regulation in force in both countries and with the international experience. It is worth noticing, however, that underground structures are less inclined to suffer damages due to seism than those on the surface of the Earth. The former move along with the rock massif they are joined to, the latter vibrate and get deformed depending on each particular inertia which may cause comparative bigger force. Not only the underground works such as Túnel de Agua Negra, but also the surface works – ports and services buildings – base their seism-resistant verification in regional and specific seismology studies of their place of implementation.

Regarding the minor vulnerability related to the tunnels towards seismic movements, it is worth to remember Japan, which is a remarkably seismic country with seism-resistant advanced engineering, has occasionally suffered damages in buildings and surface infrastructure works such as bridges and viaducts. Nevertheless, Japan has not suffered equal damages in tunnels, works that in that country are very well spread not only in mountain range but also under the sea.