Dyke Marsh, a freshwater wetland in northern Virginia and a migratory resource along the Atlantic Flyway, which is used by approximately 250 species of migratory birds, is eroding rapidly. The marsh was acquired in a congressional land trade agreement in 1959 and ceded to the National Park Service (NPS). At the time the NPS acquired it, dredge mining already had begun on its surface, and a preconditional 30-year mining agreement for direct dredging of the marsh had been stipulated. When mining ended in 1972 or 1973, the marsh had been transformed from an approximately 184-acre stable tidal wetland into a geologically unstable 83-acre remnant. Congress mandated its restoration in 1974. Unabated marsh loss has continued at this site since mining ceased, because the NPS was deeded a landform that inadvertently already had been destabilized geologically. When restoration was first mandated, the NPS had little knowledge of what the nature or scope of this problem was or how to fix it.