Syncrude Tailings Dam, Industrial dam at Mildred Lake, Alberta, Canada.

Syncrude Tailings Dam is a large engineering structure built next to Mildred Lake in Alberta, serving as a containment basin for byproducts of oil sands extraction. The facility spans 18 kilometers in circumference with sections reaching 88 meters high and handles substantial volumes of mining residue daily.

Two starter dams were built between 1976 and 1978 to hold sand until enough material was available for the main embankment. The Mildred Lake Settling Basin was officially inaugurated on 15 September 1978. The main embankment reached its final elevation of 352 m over more than half its length by 1994 and was completed in 1995.

The basin's water is recycled process water, and the fines that settle there are later pumped out for long-term storage. Since 2012 the Oil Sands Innovation Alliance has pooled industry research on tailings pond water and greenhouse gases. The pond holds naphthenic acids and process chemicals such as alkyl sulphates and alkylphenol ethoxylates.

The site is reachable from nearby Fort McMurray and sits in an industrial zone not typically open to public access. Be aware this is an active industrial facility with safety restrictions and limited entry policies.

In the early 2000s this engineering project was the world's largest earth-fill dam by volume of material used. This record status reflects the enormous scale of infrastructure required for modern oil sands operations.