The geology and the geotechnical conditions along the 18Km alignment of the Athens Metro have been extensively investigated, analyzed and evaluated. The results of this investigation have been used to develop the geotechnical parameters required for the safe design of the tunnels, stations and other underground works. The predominant geological formation is heterogeneous, fractured schist. There are also lesser, but significant, occurrences of karstic limestone and a low rate from schist. The Metro is designed to absorb the worst earthquake conditions recorded to date, consistent with Greek standards. A geotechnical investigation program was conducted to provide the information required to engineer the project. The program includes more than 300 boreholes to complement the 200 boreholes drilled along the Metro alignments in earlier investigations, on average, penetrate 20 to 30 meters below the surface. Some geotechnical investigation activities will be continuing during construction.

The most significant geotechnical activities undertaken by Attiko Metro are

• Geophysical surveys, using such techniques as ground penetrating radar, detected buried features including underground stream channels, utilities and potentially larger archaeological features.
• Measurement of ground water elevation along the tunnel alignment to determine the general direction of ground water flow and annual fluctuations in water levels.
• Development of basic soil and rock strength parameters to be used for design of project structures. The parameters are based on tests of soil and rock core samples and other data gathered during field tests.