Imperial Oil is facing nine charges for allowing millions of litres of contaminated wastewater to leak from its Kearl oilsands mine in northern Alberta, and for failing to mitigate the environmental damage.

The Alberta Energy Regulator announced the charges Friday in connection with a berm overflow of industrial wastewater at the company's Kearl mine, about 70 kilometres north of Fort McMurray.

The berm overflow was the second of two significant leaks at the Kearl mine, which put Alberta's regulatory practices in the spotlight and raised questions about transparency in the oilsands. The first of the two incidents went unreported to the public for nine months.