The federal minister of Aboriginal Affairs and Northern Development approved the plan to clean up Yellowknife's Giant Mine this week, after deliberating over the Mackenzie Valley Review Board's environmental assessment for more than a year.
The defunct gold mine is one of the most contaminated sites in the country.
The approval means the federal clean-up team can begin applying for the permits and licences required to start the massive remediation plan.
The plans include freezing 237,000 tonnes of arsenic trioxide, a byproduct of decades of mining gold. It also involves filling in underground tunnels and cleaning up tailings areas. There are about 95 hectares of waste on the surface of the site.
The minister's approval makes changes to eight of the 26 conditions the review board put on its approval of the project.
One involves wording changes to the board's recommendations for an independent oversight group for the project.
Another change allows for more options for how Baker Creek could be diverted.
The clean-up plan is estimated to cost about $1 billion.