Tunnelling in Crete - A challenging task from a variety of aspects

In 2012 the Greek State awarded Intrakat the Aposelemis Tunnel, an approx. 3.5 km long, tunnel inclined at 15% accommodating a 1.8 m diameter steel pipe to convey water from the Lassithi Plateau to the reservoir impounded by the Aposelemis dam about 600 m below for the drinking water supply of Heraklion and Agios Nikolaos in Crete. The project is regarded as an environmental project and as such is being financed from the Cohesion Fund of the European Commission. Unexpectedly, this relatively small tunnel project has offered a wide spectrum of tunnelling problems and turns out to be a challenging task from a variety of aspects: the tender and the contractual situation, technical and the meanwhile encountered geological challenges. On top of these, the economic crisis in Greece doesn't make such a project easy. Since October 2013, Jäger Bau GmbH has mastered these challenges together with Intrakat on the basis of a service contract. The TBM excavation works commenced in March 2015 and were expected to be completed within 11 months at the latest, but due to various unforeseen adverse geological occurrences, only two-thirds of the tunnel length had been excavated by August 2016.