Dams generally fall into five categories (Concrete arch, labyrinth, buttress, gravity and earth-fill). Each type has characteristics that are complex, but which generate information about the ongoing health of the dam. The use of the dynamic response of a dam to assess performance can give information about the change to the risk status and the effects of any changes to the dam. SG has experience of working on all types of dam including some of the largest in the world. In the case of assessing leakage or the onset of instabilities SG offers a comprehensive service that aids the choice of startegies for the safe continuing operation of such a facility.