Oil sands tailings ponds (Canada)
Oil sands tailings ponds are engineered dam and dyke systems used to capture oil sand tailings. Oil sand tailings contain a mixture of salts, suspended solids and other dissolvable chemical compounds such as acids, benzene, hydrocarbons residual bitumen, fine silts and water.
Source: Wikipedia — Oil sands tailings ponds (Canada) (CC BY-SA 4.0)