International Conference on Applications of Statistics and Probability in Civil Engineering (ICASP) (12th : 2015)

Economic optimization considerations in South African dam rehabilitations Viljoen, Celeste; Reynolds, Sonel


Economic optimization is applied to eleven case studies of actual dam rehabilitation projects in South Africa. The optimization includes the cost of rehabilitation and damage- and compensation costs for lives lost in case of dam failure. Economic motivation for the existence of the facility is excluded from the optimization. Five of the eleven cases would require rehabilitation based on economic optimization. The other cases either had a prohibitively high rehabilitation cost, an already low probability of failure prior to rehabilitation or low expected loss of lives in case of failure. Costs to improve safety for the different cases was typically between ZAR 0.5 and 5 million per percentage reduction in the probability of failure over a 50 year design life, but could be as high as R50m/%. A high cost per percentage reduction is typically associated with dams that already had a low probability of failure prior to rehabilitation. Interesting to note when the outcome is compared to other rehabilitation decision criteria is that ANCOLD’s ALARP criterion dictated that in all of the eleven cases the dams be rehabilitated, while only one of the eleven cases would require rehabilitation based on the Society’s Willingness to Pay utility function (Reynolds, 2013). Surprisingly, the cost of rehabilitation works is not considered as part of the South African Department of Water and Sanitation’s (DWS's) decision framework. Rational incorporation of this cost needs consideration.

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