The regulator soon concluded the water had come from tailings ponds where the company stored the toxic sludge-like byproducts of bitumen mining. Environmental samples showed high levels of several toxic contaminants, including arsenic, iron, sulphate and hydrocarbon – all of which exceeded provincial guidelines.
But the company failed to notify the federal government and nearby Indigenous communities. In February, there was another leak, in which 5.3m litres of tailings water escaped from an overflowing catchment pond. This time, the community was informed two days later.