Syncrude Tailings Dam

Syncrude Tailings Dam
Syncrude Tailings Dam - Mildred Lake Settling Basin, enclosing tailings pond
Official name	Syncrude Tailings Dam
Location	Fort McMurray, Alberta, Canada
Coordinates	57°03′25″N 111°36′00″W / 57.057°N 111.600°W / 57.057; -111.600Coordinates: 57°03′25″N 111°36′00″W / 57.057°N 111.600°W / 57.057; -111.600
Construction began	1978
Operator(s)	Syncrude Canada Ltd.
Dam and spillways
Height	133 to 288 ft (41 to 88 m) (2001)
Length	11.3 miles (18.2 km) (2001)

The name Syncrude Tailings Dam often refers to the Mildred Lake Settling Basin (MLSB). This is an embankment dam that is, by volume of construction material, the largest earth structure in the world in 2001. It is located 40 km (25 mi) north of Fort McMurray, Alberta, Canada at the northern end of the Mildred Lake lease owned by Syncrude Canada Ltd.. The dam and the tailings artificial lake within it are constructed and maintained as part of ongoing operations by Syncrude in extracting oil from the Athabasca Oil Sands. Other tailings dams constructed and operated in the same area by Syncrude include the Southwest Sand Storage (SWSS), which is the third largest dam in the world by volume of construction material after the Tarbela Dam.

According to Canada’s Oil Sands Innovation Alliance (COSIA), an alliance of oil sands producers formed in 2012, who share research on Environmental Priority Areas (EPAs) such as tailing pond water and greenhouse gases, "Tailings are the sand, silt, clay and water found naturally in oil sands that remain following the mining and bitumen extraction process." The hot water process used by Suncor and Syncrude in their open-pit mining operations, to extract bitumen from the Athabasca Oil Sands (AOS) produces large quantities of tailings pond sludge which remains stable for decades. By 1990 it was considered to be the "imminent environmental constraint to future use of the hot water process." Oil sands tailings pond water contains toxic chemicals such as "naphthenic acids (NAs) and process chemicals (e.g., alkyl sulphates, quaternary ammonium compounds, and alkylphenol ethoxylates)."

By 2012 Syncrude Canada Ltd had oilsands mining operations on three lease areas (Mildred Lake, Aurora North and Aurora South), all about 40 km north of Fort McMurray. There are many tailings dams on those leases. The lease that has the greatest number of tailings dams, and the largest tailings dams, is the Mildred Lake lease. According to Syncrude's 2010 Baseline Report submitted to the Energy Resources Conservation Board (since replaced by the Alberta Energy Regulator (AER), the Mildred Lake and Aurora North leases together contain: the Mildred Lake Settling Basin (MLSB), Southwest Sand Storage (SWSS), West In-Pit (WIP), East In-Pit (EIP), Southwest In-Pit (SWIP), Aurora Settling Basin (ASB) and Aurora East Pit Northeast (AEPN-E). Those referred to as "in pit" have only small containing embankments. In Aurora South lease the main tailings dam will be the External Tailings Area (ETA). This doesn’t exist in 2010, construction will start before 2016.