In the region of Asturias in the north of Spain the last stretch of the Cantabrico Motorway has recently been opened. As part of the tunnel excavation for this motorway, a vertical excavation has been carried out in a natural hill. A pile wall—with several anchorage lines—was initially designed to contain the terrain but the ground conditions that were initially expected turned out to be different in the field. The position of the rock level is lower than what was thought and important horizontal movements of the pile wall have been recorded, with signs of instability. It is necessary to reconsider the initial design with an increase in the number of anchorages designed and to monitor the movements of the pile wall. Finally, with the development of proper numerical analysis, a reinforcement of the ground in the extrados of the pile wall is carried out, with the objective of obtaining an “equivalent cohesion” in the ground, and also to reduce the lateral pressure on the pile wall. This paper describes the process for obtaining a final stable situation of the natural hill and the pile wall, the ground characterization and monitoring of the movements that took place.