Norwegian experts: Tallinn-Helsinki tunnel could be built in 5 years
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The structure would be made up of three bores: two bores for transit in either direction plus one service tunnel.
The base underneath the Gulf of Finland is rather similar along the whole distance of more than 80 kilometers between the two capitals, consisting mainly of granite and gneiss. Finns have experience working with a bedrock like this.
On the Estonian side the bedrock lies significantly deeper, at almost 120 meters, being covered by layers of soft sandstone and blue clay.
The metro of St. Petersburg has been built in a similar blue clay environment.
While digging the tunnel would be time-consuming, experts at a Norwegian boring company say that the structure could be ready in five years if in addition to digging simultaneously from Tallinn and Helsinki digging was started also in the middle.
Possible methods for tunnelling are drilling and blasting. Drilling would be the more expensive of the two, whereas blasting would be a cheaper but more time-consuming option.
The Tallinn-Helsinki tunnel is estimated to cost approximately 13 bln euros to build. ■