The Saskatchewan government is suing Ottawa over costs associated with the cleanup of the Gunnar mine site, an abandoned uranium mine.

The lawsuit, filed on Tuesday, calls on the federal government to honour a 2006 memorandum of agreement (MOA) that saw both sides committing to sharing the cost of cleaning up the northern Saskatchewan site.

When the MOA was signed, the estimated cost was $24.6 million over 17 years. The two sides agreed to split the cost.

The cost has now ballooned to an estimated $280 million. To date, the province has paid $125 million cleaning up the mine and its associated satellite sites. The province said the federal government has contributed $1.13 million.

"The federal government agreed to cost-share this project equally, but has since refused to uphold its end of the agreement," said Minister of Energy and Resources Bronwyn Eyre.

She said after years of back and forth the province was left with "no choice" because it has an obligation to fully remediate the site.

In an emailed statement to CBC, a spokesperson from the Ministry of Natural Resources said, "as the owner of the site, the Government of Saskatchewan is responsible for the Gunnar Mine Remediation Project."

It goes on to say the federal government has provided funding for the first phase of the project and it will commit to funding the remaining two phases "after Saskatchewan obtains all the necessary approvals required to proceed with remediation."

Mine's history

The Gunnar mine site, located west of Fond du Lac near Lake Athabasca, began production in 1955 and was shut down in 1963.

The federal, Crown-operated Eldorado Mining and Refining Corp. supplied refined uranium yellowcake that was an essential ingredient for U.S. atomic weapons.

A view of the Gunnar mine clean up near Lake Athabasca. (Government of Saskatchewan)

The mine produced 4.4 million tonnes of tailings and 2.2 million tonnes of waste rock. It also left behind an open pit more than 100 metres deep.

Canada officially stopped exporting uranium for weapons production in 1965.