Freezing weather cracked an overflow pipe on a tank holding oil production water on the Blackfeet Reservation, causing about 12,600 gallons to spill.
The Bureau of Land Management says the spill discovered Tuesday about 10 miles southwest of Cut Bank didn't involve oil, but wastewater that is the byproduct of oil and gas production.
Grinnell Day Chief is director of the Oil, Gas and Minerals Department for the Blackfeet Tribe. He says there was "very little, if any" crude oil in the water, but it did have salt in it. He says the surface soil will have to be scraped away and disposed of, with the area re-seeded in the spring.
An Environmental Protection Agency spokeswoman said FX Drilling Co. had already begun cleaning up the spill.