FILE - In this Aug. 14, 2015 file photo, water flows through a series of sediment retention ponds built to reduce heavy metal and chemical contaminants from the Gold King Mine wastewater accident, in the spillway about a quarter mile downstream from the mine outside Silverton, Colo. New Mexico officials said Thursday, Jan. 14, 2016 that they plan to sue the federal government and the owners of two Colorado mines that were the source of a massive spill last year that contaminated rivers in three Western states. An EPA cleanup crew accidentally triggered the spill in August at the inactive Gold King mine near Silverton, Colo.(AP Photo/Brennan Linsley, File)

DURANGO | The U.S. Environmental Protection agency wants a mining company to pay for a potentially costly investigation of underground water flows at a southwestern Colorado Superfund site to help the agency devise a cleanup plan.

The EPA on Thursday ordered Sunnyside Gold Corp. to study part of the Bonita Peak Mining District. The district includes the Gold King Mine, where agency workers inadvertently triggered a massive spill in 2015.

Sunnyside doesn’t own Gold King but has other mining property within the federal cleanup site.

The EPA has said previous work at one of Sunnyside’s mines may be contributing to wastewater flowing into the Animas River.

Sunnyside says it has already spent $30 million on reclamation work in the area and maintains it is not the cause of the water quality problems.