Dams must be designed and maintained to safely control seepage. Nevertheless, most dams experience at least some seepage and many suffer from excessive seepage. Excessive seepage may lead to a problem with the safety of a dam if not treated properly. The basic problem is trying to discern how seepage is affecting a particular dam and what measures, if any, must be taken to ensure that the seepage does not adversely affect the safety of the dam. You may be called upon to make a visual inspection of a dam and its appurtenant structures and inspect a project's document files for clues to the likelihood of failure due to seepage problems. You may need to review background information on geologic characteristics, construction specifications and records, and safety and inspection records to discern critical information pertaining to seepage. If a seepage problem has already been identified you may be asked to determine the probable cause of the seepage and the remedial action needed. If you are an owner or otherwise have responsibility for a dam you should understand seepage, and know whether your dam and its appurtenant structures are safe with regard to seepage. It is also important to monitor seepage and maintain seepage control measures that are already in place.
This module provides background information on the evaluation and monitoring of seepage, the evolution of seepage control measures, maintenance of seepage control measures, and the various modes of failure related to seepage. Unit I concerns the historical evolution of seepage control measures and causes of dam failure due to excessive seepage.