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Progress for the Andes Agua Negra road tunnel 02 Mar 2017

Patrick Reynolds for TunnelTalk

After being long on the drawing board, the proposed 13.9km Agua Negra road tunnel project in South America has enjoyed a succession of steps forward over recent months, helping to push ahead plans and construction procurement of the strategic transport link through the Andes mountains between Argentina and Chile.

Current mountain pass and Cristo Redentor tunnel is often closed in winter
Current mountain pass and Cristo Redentor tunnel is often closed in winter

The Inter-American Development Bank (IADB) recently agreed to a US$40 million loan package to support start of the procurement progress for the almost US$1.6 billion bi-national project, which will create an all-year, all-weather and quicker route through the mountains in twin highway tubes. At present, the existing mountain road over the Agua Negra Pass is closed for several months during each winter.

The development bank has agreed to back the full cost of the Agua Negra Tunnel through a series of loans. Following agreements reached in early 2016 between IADB and both Argentina and Chile to fund the major transport project, at the end of the year the bank approved initial loans to help finalise upfront planning and get procurement underway. The first debt package is structured as a pair of loans, each US$20 million, issued to the two countries.

Following recent launch of procurement phase, the deadline to submit applications to prequalify for the design and construction works was pushed back from the set date of 8 February 2017. A new date for submissions has yet to be decided according to the latest update from the project’s development agency, EBITAN. The Governments of Argentina and Chile had been hoping to get construction of the tunnel underway before the end of 2017.

Paving the way

The 13.9km Agua Negra road tunnel is a strategic transport project for Argentina and Chile, and also offers benefit to the wider Mercosur trading block in the continent. It is a key link in the developing transport corridor between the Pacific coast, at Coquimbo in Chile, and the Atlantic, via Porto Alegre in Brazil.

Fig 1. The 13.9km option was selected as the preferred tunnel alignment
Fig 1. The 13.9km option was selected as the preferred tunnel alignment

Presently, the transport corridor is served by the existing main road that winds up the mountains to an elevation of more than 4,700m. The heavily trucked highway over the Agua Negra mountain pass is one of the highest border crossings in the world but offers limited capacity and is open for little more than half of each year.

The Agua Negra Tunnel calls for a 13.9km long twin tunnel system linked by cross passages every 250m, and emergency inter-connections for vehicles every 1,550m (Fig 1).

The tunnel portals are at 3,620m and 4,085m above sea level and the twin tubes rise at a 3.37% grade from the Chilean portal and having the majority of its length (72%) in Argentinian territory, explains EBITAN in its prequalification document. The project also includes two major ventilation structures, a 500m deep shaft and a 4.5km long tunnel. Expected drill+blast excavation of the estimated 2.1 million m3 of material, and construction of the 13.9km long parallel highway tunnels, is anticipated to take up to nine years.

Swiss engineering consultant Lombardi has been working on the initial planning for the project since late 2012. It has been providing engineering services to cover preliminary studies, initial civil engineering and M&E designs.

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