The design, construction, and performance of concrete cut-offs and grout curtains as dam seepage remediation methods in carbonate foundations are reviewed. Recent experiences gained when attempting to build concrete cut-offs through hard and highly permeable rock masses have led the authors to develop the concept of a “composite cut-off.” A campaign of high-quality drilling, permeability testing, and grouting is first conducted to pre-treat the very permeable and/or solutioned zones, to seal the clean fissures, and to provide an extremely detailed geological basis upon which to design the location and extent of the subsequent concrete wall (if in fact needed). Bearing in mind that the average cost of a concrete wall is many times that of a grouted cut-off, and that there is currently a shortfall in industry capacity to construct the former, the concept of a “composite wall” is logical, timely, and cost effective, as well as being sustainable.

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