"Filters in embankment dams are composed of specifically-designed entities (zones) of coarser-grained soils placed at specifically-targeted locations within or adjacent to the dam structure. Filters are designed and constructed to achieve specific goals such as preventing internal soil movement and controlling drainage, and are typically installed during new dam construction. Filters have also been added to existing dams to meet specific requirements. This document provides procedures and guidance for best practices concerning embankment dam filter design and construction, and represents an effort to collect and disseminate current information and experience having a technical consensus. Currently available information was reviewed, and when detailed documentation existed, it was cited to avoid duplicating available materials. The authors have strived not to reproduce information that was readily accessible in the public domain and attempted to condense and summarize the vast body of existing information, provide a clear and concise synopsis of this information, and present a recommended course of action."
United States. Federal Emergency Management Agency: http://www.fema.gov/