This study was conducted to identify methods that have been used in the repair and rehabilitation of concrete dams. Information was obtained through literary searches, discussions with project personnel, and visits to project sites. Each case history includes a background of the project, the deficiency that necessitated repair or rehabilitation, and descriptions of materials and methods used in the repair or rehabilitation. When available, the cost of the repair project and the performance of the repair to date have been included. Case histories included in this report cover a range of deficiencies in concrete structures, including cracking, spalling, erosion, leakage, inadequate PMF capacity, expansion resulting from alkali-aggregate reaction, instability, and insufficient storage capacity.

As dams age, they are subject to a series of external agents and processes which tend to deteriorate the qualities with which they were originally conceived to stand against these actions. At the same time, it is often necessary to respond to increased safety standards, either in the structural or hydrological fields. Reservoir sedimentation or wat

The present state of the art of dam engineering has been ronmental, and political factors, which, though important, attained by a continuous search for new ideas and methods are covered in other publications. while incorporating the lessons of the past. In the last 20 The rapid progress in recent times has resulted from the years particularly there have been major innovations, due combined efforts of engineers and associated scientists, as largely to a concerted effort to blend the best of theory and exemplified by the authorities who have contributed to this practice. Accompanying these achievements, there has been book. These individuals have brought extensive knowledge a significant trend toward free interchange among the pro to the task, drawn from experience throughout the world. fessional disciplines, including open discussion of prob With the convergence of such distinguished talent, the op lems and their solutions. The inseparable relationships of portunity for accomplishment was substantial. I gratefully hydrology, geology, and seismology to engineering have acknowledge the generous cooperation of these writers, and been increasingly recognized in this field, where progress am indebted also to other persons and organizations that is founded on interdisciplinary cooperation. have allowed reference to their publications; and I have This book presents advances in dam engineering that attempted to acknowledge this obligation in the sections have been achieved in recent years or are under way. At where the material is used. These courtesies are deeply ap tention is given to practical aspects of design, construction, preciated.