A mining company is accusing the Environmental Protection Agency of letting a huge volume of polluted water reach a southwestern Colorado river by operating a wastewater treatment plant below full capacity.

The allegation came Wednesday from Sunnyside Gold Corp., which is fighting the EPA over who should pay for a water study as part of a Superfund cleanup.

The cleanup includes the Gold King Mine, source of a 2015 spill that polluted rivers in Colorado, New Mexico and Utah.

Sunnyside owns a different mine there. The company says it isn't liable for the area's water pollution.

Sunnyside says the EPA is making things worse by not operating the treatment plant at full capacity. The plant treats wastewater from the Gold King.

The EPA didn't immediately respond to a request for comment.