The studies conducted in the framework of Rail 2030 and the long-term development of the Geneva node (master plan Horizon 2050) have highlighted the need to build two further tracks at Geneva main station by 2025. Since 2011, several preliminary studies have been conducted to increase the service while respecting the established financial budget. The preliminary study called “EP 2015” is the basic scenario for the preliminary design studies to be undertaken. The framework agreement underlying the extension of the Geneva underground station was signed on December 7th, 2015. The Confederation, the Canton of Geneva and the Municipality of Geneva will invest over 1.6 billion Francs in the underground expansion of Cornavin station. The selected project involves the construction of two underground tracks and a platform. The trains will access the new tracks via a double-track tunnel on the Lausanne side and a single-track tunnel on the Airport side. Lombardi Engineering Ltd., leader of the JV G3, together with its partners, is responsible for the preliminary design (phase 31) of the double-track access on the Lausanne side for civil works (access ramp section: 246 m, section in cut & cover 184 m, tunnel 1’003 m, section in cut & cover in the connection area to the station 296 m, total 1’729 m) and optionally for all the subsequent phases (from 32 to 53, design, project management, commissioning). The coordination between civil engineering and railway technology is also included in the mandate. The execution of the works is planned under full train operation. The underground structures will be excavated in clay (alluvial materials) and in the moraine, partially in the Rhône aquifer, in difficult geotechnical and geomechanical conditions.