The purpose of the pilot tunnel project was to test the chosen method of NATM excavation in an area of rapidly changing ground conditions ranging from very hard rock to very soft in residual soil. Further the pilot project provided additional experience with local tunneling conditions as well as ground water and geotechnical data relevant to the main Project.

Owner during Construction Ministry of Environment, Town Planning and Public Works

Period of Construction November 1987 to October 1989
Type of Project Two track main line the Metro tunnel, concrete lined
Location Between Sepolia and Attiki Station, Line 2
Dimensions 902 meters long; oval section 8.54mx 630m
Depth to Top of Tunnel 13 to 7 meters
Financing 50% Program of Public Investment
50% Mediterranean Integrated Programs, EEC
Cost 2.02 billion drachmas, including VAT
Construction technique
New Austrian Technique Method (NATM) using a "Roadheader " and hydraulic excavator.17 m.of controlled blasting; reinforced concrete lining.
Geology
Athenian schist system and related ingenous rocks, specifically 15% limestones, 25% schists and 60% igneous.