The Department of National Defence says the largest environmental cleanup in Canada's history is now finished.

The DEW Line remediation project cost the government $575 million and saw the removal of toxic waste from 21 former radar stations across the Arctic.

The stations were built in the Cold War era to defend North America from enemy aircraft. Most were decommissioned decades ago.

Federal Treasury Board president Tony Clement announced Friday that the cleanup work was done.

“The remediation work of each site typically consisted of demolition of infrastructure, cleaning up or removing of contaminated soils, stabilizing of landfill sites and  the construction of new and innovatively engineered landfills designed to stand the test of time, “ said Clement.

Many Inuit and Inuvialuit helped with the cleanup. Of the 21 sites, there are four that still need minor cleanup of debris and tents.

The federal government says a monitoring program is in place to ensure the sites remain safe for at least the next 25 years.