In 1973 construction on a dam was begun by Syncrude Canada Ltd. to store talings left over from extracting oil from tar sands in Athabasca, Canada. Known as the Syncrude Tailings Dam, this dam may only be surpassed by the new Three Gorges dam in China in terms of capacity and according to one source is the largest in terms of construction material.
A new book describing this and simlar dams and the environmental risks that they pose is by Andrew Nikiforuk, and was available for free download (I could not get the link to work) at: Tar Sands: Dirty Oil and the Future of a Continent
Links: Syncrude’s Website
Iowa Environmental Compliance 