Page - 1553 - in Book of Full Papers - Symposium Hydro Engineering

modus operandi, involved in achieving the overall operational functions. Some form of monitoring and surveillance of the operational modes of the dam and its sub-systems, components and parts provide the starting point for a dam safety analysis, regardless of its form or the level of detail [2], [3] According to the US Bureau of Reclamation (p.17): “Many times, weaknesses or deficiencies can be identified from changes in the behavior of the structure, foundation, abutments, or seepage.”, …, “Any unusual behavior, regardless of how seemingly insignificant, should be identified and recorded because any unusual condition may be the forewarning of a newly developing unsafe condition.” Monitoring of structural and functional behaviour under normal operating conditions covers the spectrum from visual identification of structural or functional distress (visually observable deformation, overtopping), through visual identification of precursors of physical distress (increased seepage), to detection of actual distress or its precursors via instruments and other technologies. Typically, the monitoring activity is embodied in the broader surveillance process that involves assessing the integrity of the recorded data, interpreting this data and transforming it into meaningful information that then informs safety management actions. Surveillance, which transforms monitoring data into engineering information provides essential analytical and interpretative elements of real-time dam safety assessment. The notion of basing a surveillance program on monitoring the operational modes of a dam system and its components is not obviously aligned with the notion of focusing the surveillance process on detection of early development of significant failure modes as set out in ICOLD Bulletins 138 and 158 [4], [5]. This is because the latter implies that the effort should be directed at “significant” failure modes that can be identified prior to the establishment of a surveillance program (or prior to re-configuration of an existing program), whereas the former operational modes monitoring approach which is deterministic, does not impose any restrictions or make assumptions about how failures or incidents might develop either physically or temporally. This paper is underpinned by an unparalleled 25 years of pioneering experience as a dam owner in developing and advancing capability in risk- informed dam safety management while simultaneously maintaining and improving a robust surveillance program as part of a comprehensive dam safety management system. Periodic critical re-assessment of our performance in both of these areas of the dam safety program, which includes independent external audits of the program every 5 years, leads to the question as to whether the dam safety program should revolve around the results of analysis of failure modes in a portfolio risk management process as suggested by some, or maintain and advance the current approach of focusing first on monitoring and surveillance of the operational performance of the dams on an individual basis. 1553