Since 2002, regulations have been in place. The private sector posts bonds to manage the mitigation of sites. Prior to 2002, such requirements did not exist. Speaking for the north in particular, two of the major mining projects—the Faro and the Giant—were active when the government did not have requirements for the companies to mitigate all impacts as they closed down. When they closed these companies as active mines, they reverted to the control of the Government of Canada. The Government of Canada thereby became responsible for their mitigation.
On November 29th, 2011. See this statement in context.