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The undersea road passes through the Aktio - Preveza tunnel providing the quickest connection between Aitoloakarnania and South Greece with the road along the seaside of Preveza - Thesprotia Prefectures and Igoumenitsas Port.

The Preveza - Aktio Crossing has a total length of 1982m. and is made up of

Akteo P1010583

The undersea section is constructed of 8 prefabricated elements; the biggest element has length 134.50m., thickness of walls 1m and weight almost 15.000 tons. The elements are manufactured in a casting basin in Aktio with total area, 67.500m2 The seabed is 11m under the surface of the sea. To keep the casting basin dry a network of perimetric drillings was used so as to lower the water level. The casting basin communicates with the sea through a channel that is manufactured by diaphragm walls. The communication is succeeded by the removal of the channels barriers. 
In the next stage the elements were sealed with the use of barriers and the flood of the casting basin. The floating elements because of the buoyancy were towed into their final position. In the end the elements were immersed with the use of pumps and by increasing and reducing the water level thorough a temporary network of pipes, which was located in the internal area of the elements. The bottom of the sea trench is improved with the construction of 8.482 stone columns (diameter about 60cm and 12m length) in segments of 1,80m X 1,80m in a total length of 125 km.


THERMAIKOS TUNNEL in the northern Greek Metropol and Capitol of Makedonia: Thessaloniki
under design


The project, was tendered as a builtfinance-operate-transfer project, and will result in a 6-lane bypassing road toll-tunnel with entrances and exits on both sides of Thessaloniki City Centre. The project consists of approximately 4km alignment, including 1,5km immersed tunnel under the Thessaloniki harbour basin and approximately 2,5km cut & cover tunnels and ramps at either end of the immersed tunnel. The most challenging technical aspects of the project were seismic design of the immersed tunnel and the extension of the immersed tunnel to below existing quays on either side of the harbour basin. The extension of the immersed tunnel required temporary retaining structures for providing a channel for immersion of elements and different foundation and load cases for the completed tunnel. COWI carried out Design Management, Specialist Services and Tender Design of immersed tunnel and mechanical installations in tunnels for THESCROS Consortium. Local consultants carried out Tender Design for other parts. COWI coordinated the Tender Design and reviewed design by local consultants.

Project Period: 2003 - 2004

Client: THESCROS Consortium

- FCC, Spain
- Pantechniki, Greece
- Attikat, Greece
- Pihl & Søn, Denmark

Construction Costs: EUR 400 mio.

COWI fee: EUR 335.000

Thessaloniki UST