The Montana Department of Environmental Quality is asking a bankruptcy court to set aside $6 million from the owner of a Fergus County gold mine to ensure treatment of polluted water.

According to the Great Falls Tribune , Colorado-based Atna Resources Inc. and six affiliates — Atna Resources Ltd., Canyon Resources Corp., CR Briggs Corp., CR Kendall Corp., CR Montana Corp. and Horizon Wyoming Uranium Inc. — filed for bankruptcy protection in Colorado in 2015.

The CR Kendall Mine is an open pit gold mine that operated until 1997, when it closed.

Mines are required to provide a bond for cleanup, but Montana officials say they need more money from the bankruptcy court to cover cleanup costs.