Lisbon Metro - Extension I Plan (PER I) Extension 1 Plan of the Lisbon underground network, including the following actions: Disconnection of the Y (in Rotunda) and Rotunda-Rato extension; Disconnection of the Rossio-Restauradores section and Rossio - Baixa/Chiado – Cais D Sodré and – Baixa/Chiado- Restauradores extensions; Colégio Militar – Pontinha extension; new Garages and Workshops in Pontinha (PMO III). With this Extension Plan, the Lisbon Underground network goes from being a single “Y” line, 19 km long and 25 with stations, to a system comprised of 3 functionally independent lines with a total length of 23 km and 30 stations, which establishes the essential connections with the railway network (local and intercity lines) and with the river connections with the south bank of the River Tajo. Main technical characteristics: Building of 4 km of tunnels (of which 1.8 km are excavated with a 9.4 m diameter tunnel boring machine) and 6 stations with a length of 96 m. An important part of the extension work was conducted in the underground of the old district, in very difficult geological conditions, which rendered it necessary to mobilise high-tech equipment for the building of the tunnels and underground work and very experienced engineering professionals to develop highly demanding technical solutions, such as the building of the cavern of the Baixa/Chiado station with a diameter of more than 17 m and the digging of tunnels of 9.4 m diameter in areas closer to the river Tajo which, while performed with a tunnel boring machine, called for major soil treatment.p> SENER developed a wide range of services that included the study of layout alternatives and the location of stations and new workshop, the drafting of the Preliminary Design, drafting of the sheets of specifications, assessment of bids, monitoring and revision of Client: METROPOLITANO DE detailed design, construction management and commissioning. LISBOA, S.A. Location: Lisboa Country: Portugal Start date: 1991 End date: 1999 © SENER Ingeniería y Sistemas, S.A 1991 http://www.sener-civil-architecture.com/CIVIL/ - [email protected].