The provided services were finalized to the analysis and interpretation of results from geotechnical investigation conducted for the design of the North shaft. North shaft is divided into two sub-shafts, one for north bound and one for south bound TBM extraction. Retaining structures consist of secant pile walls, sustained by 3 strut levels. The maximum excavation depth is approximately 17.5m and the maximum width of the excavation is 11.7m for north bound and 13.6m for south bound. Struts levels are installed at depth of approximately 3.5m, 7.5m and 11.5m from ground level. Due to the importance of the excavation works and the context in which the structures are located (urban environment with retaining walls near to the existing buildings), a monitoring system has also been designed, in order to control the accordance between project assumptions and measured quantities.