Athens metro, Lines 2 and 3

New metro Lines 2 and 3 in Athens criss-cross the city from north to south and east to west. This turnkey design-build project included two tunnels, 9.2 and 8.4 kilometres long, respectively, and no fewer than 21 stations. This infrastructure, which is used by 600,000 passengers on a daily basis, has reduced car traffic in the city centre and cut the pollution that is harming the Greek capital’s historic centre by 8%. Today, the Athens metro is among the most modern in all of Europe.

BACKGROUND

Metro Line 1 in Athens dates from 1930. It was the only metro line in the city until 2000. In 1930, the capital of Greece had a population of about 450,000; today, that figure is nearly 3.5 million, including 900,000 in the municipality of Athens itself. Consequently, the city’s transport infrastructure was unable to meet increased demand. During this 70-year interval, car traffic also rose, leading to congestion in the city’s main thoroughfares.
In 1987, a call for tenders for the construction of Lines 2 and 3 was launched. In 1991, a contrat was signed by the Greek minister of public works and the European consortium, Olympic Metro (which brought together 22 Greek, German, and French companies).

TECHNICAL OVERVIEW

The project called for the development of two metro lines: a north-south line 9.2 kilometres long and an east-west line 8.4 kilometres long for a total of 21 stations.
To build this infrastructure, two tunnel-construction methods were employed: the use of TMBs for the most part and the use of the New Austrian Tunnelling Method (NATM). The project, however, faced geological challenges. On the one hand, the subsoil below Athens is complex due to the many tectonic shifts it has experienced; on the other hand, the soil itself consists of shale, which provides fairly good cohesion. However, other more heterogeneous areas (altered igneous rock and hard to very hard limestone) were less stable, which led to landslides during boring operations carried out with TBM number 1 and, therefore, delays in its progress.
Moreover, Athens has been continuously inhabited for the past 9,000 years, and its layers of subsoil reflect its various transformations over time. Since work was carried out below the city historic centre, numerous precautions had to be taken when the TBMs were operating under or near historic monuments. Archeological sites were discovered, including a Roman bath in perfect condition with its water basin and heating system in the ground.

This project has provided Athens with a safe, fast, reliable, and eco-friendly transport system. It also provides a touch of modernity and technology that blends in well in this millennial city. 

IMPACT

On these new metro lines, trains – travelling up to 80 kilometres an hour – arrive every three minutes. These new lines have reduced commuting time. Travel from Dafni (the southern terminal on Line 2) to the city centre has been cut by a half-hour on average: it went from 30 to 45 minutes by car to just nine minutes on the metro.
The project has helped to relieve traffic congestion in Athens by providing a fast transport option linking the old city, business district, and residential neighbourhoods.
In addition, extending the Athens metro significantly reduced pollution damaging to archeological sites.
The tunnel-boring operations included advanced archeological excavations, which led to the discovery of numerous sites of archeological interest, thereby adding to the city’s capital as a centre for archeological knowledge and artefacts. Interestingly, the artefacts found during the project did not disappear from view at the end of the project since three stations currently feature showcases for these pieces as well as modern art – making the Athens metro something of a museum and art gallery.

Project participants

Client
Attiko Metro

Project management
Bechtel International, Inc.

Key figures

Implementation dates
November 1991 to April 2003

Concrete
865,000 m3

Excavation
964,000 m3

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