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Tuesday, August 25, 2020

Erjos to be the 'daddy' of all tunnels and a 'before' and 'after' in terms of island mobility

Position of the Teno Massif Florival fr / CC BY-SA

Works on the Anillo Insular de Tenerife (Tenerife Island Ring Road) have been news for years, but it finally feels more like the closing the ring is shortly to become a reality and this final stage something of a dramatic climax in terms of Civil Engineering.

The Teno Massif is one of the three volcanic formations that gave rise to the island, along with those of Anaga and Adeje. The Insular Ring Road, and, specifically, the El Tanque-Santiago del Teide section, which will link north and south of Tenerife and signify a 'before' and 'after' in terms of mobility around the island, requires drilling the oldest basalt in Tenerife in order to build the Erjos Tunnel, which will be the longest in the Canary Islands, and one of the largest in the country at 5.1 kilometers, through two parallel tubes.

The tunnel will be drilled with specific machines or 'robots' with two and three heads that allow several drills to be carried out simultaneously. There will be five, one for each tunnel mouth and another to have as a spare in case of breakdown. One of the first arrived on Friday at the works area in Santiago del Teide and it is forecast that it will start working at the end of next month on the south side. In the case of the north, the plans point to November-December and from that moment, all the machinery will be operational.

Although the drilling and subsequent explosions are certain to be noisy, it is said that it will hardly be perceived by the population as the work will be at a depth that ranges between 400 and 600 meters. The amount of kilos of explosives that will be needed cannot yet be specified, since this will be adapted to the terrain that is found. Depending on the type of rock, it is expected to extract an average of between 6 and 8 meters per day. 

It is anticipated that both entrances will meet in approximately two years and that the excavation will be carried out in two phases due to the dimensions of the cavity. 

The surplus material that is extracted from both will be used to rehabilitate the Bilma quarry, in the southern municipality, while another amount will be used to fill specific sites - an equalization of land in engineering terms - in the layout of the road, mostly in the north.

Once completed, at 5.1 kilometers long, Erjos will become the 'father' of all tunnels. Currently, the longest in Tenerife is El Bicho, in Santiago del Teide, at one kilometer long, followed by El Guincho, in Garachico, barely 725 meters.