The performance of the Shikwamkwa Replacement Dam thirteen years post-construction

Throughout the life of a dam, issues such as changes in technology, standards, and the behaviour of the dam and its foundation need to be reviewed and reconsidered as part of the dam safety management program to ensure that maintenance practices, monitoring systems, and other safety practices remain appropriate. As dams age, the nature of the structure can vary considerably. For example, in the initial stages of a dam life-cycle, seepage is in a transient state which can result in very different conditions and loadings than those which arise after steady-state is achieved. During this stage, seepage flows “search” for defects and, if they exist, dam safety incidents can occur in the first few years following impoundment. When steady seepage is achieved, conditions can still change with time due to issues such as consolidation and pore pressure redistribution, movement of fine materials into and out of bedrock discontinuities, segregation at filter boundaries, areas of concentrated flow, and a variety of other factors. Unchecked, these factors can result in dam safety incidents after many years of seemingly trouble-free service.

This paper outlines the value of implementing a coupled standards-based/risk-informed approach that has been used as one of the tools for effective dam safety management for the Shikwamkwa Replacement Dam, near Wawa, Ontario, with a focus on the performance of the dam through construction to steady state 13 years after construction.