It's the cost to actually clean it up. If it's a multi-year project that goes 20 years into the future.... To clean up AECL is a long-term game, as is Giant Mine. You would take the long-term expenses and actually discount them back to present value. There are discount rates involved, there are interest rates involved, but it is the present value estimate of the cost to clean up that site to meet current environmental standards.
On May 19th, 2016. See this statement in context.