Geotechnical hazards are caused by slope instability, collapse, subsidence or uplift of the site surface, solid liquefaction and anomalous behaviour of foundation materials. Slope instabilities can be produced by landslides or snow avalanches with the possibility of affecting the electrical grid and the water intakes; caves, karstic formations, underground rivers, mines and water, gas or oil wells may cause collapse, subsidence or even uplifts of the site surface, affecting building structures; solid liquefaction induced by earthquakes has the potential of causing differential movements among builds connected by pipes and cables; and foundation materials may also produce differential movements among buildings, requiring a good knowl­edge of the foundation materials and their properties under static and seismic loadings.

An IAEA safety guide addresses the geotechnical aspects to be consid­ered in site evaluation and foundations for NPPs (IAEA, 2005). The guide describes the many geological aspects that must be evaluated, the observa­tions to be conducted and the laboratory tests to be performed. Special attention is given to the stability of the site and the foundations, necessary for the design basis of the major buildings. Such parameters, mainly the stability of the foundations, need to be reassessed during site preconstruc­tion activities and monitored during the operational life of the plant.