Federal regulators ruled on Jan. 23 that Exxon Mobil Corp. must pay a $1.05 million penalty for safety violations related to a 2011 pipeline break under Montana’s Yellowstone River.

The Wall Street Journal (WJS) reported on Jan. 24 that in the 2011 incident the pipeline was buried beneath the riverbed, but flooding amid a summer snow melt exposed it and stressed it to the breaking point. An estimated 1,500 barrels of oil spilled into the river and were carried miles downstream.

Exxon spokesman Christian Flathman said in a statement Jan. 24 that Exxon is reviewing the agency’s final order. The company has 20 days to ask the agency to reconsider the ruling.

The WJS reported that the Yellowstone River is the site of another major cleanup effort, following another pipeline break last week about 230 miles east of Exxon’s 2011 spill. It isn’t yet clear what caused Bridger Pipeline LLC’s Poplar pipe to fail under the river. The company now estimates that about 960 barrels—more than 40,000 gallons—spilled into the partially iced-over river. That incident fouled drinking water for residents of the city of Glendive, Mont., but state officials said Jan. 23 that the water is once again safe to drink.

In the case of the 2011 spill, Jeffrey Wiese, associate administrator of the Pipeline and Hazardous Materials Safety Administration, upheld a finding that Exxon hadn’t adequately prepared for the possibility that flooding could cause the pipeline to fail—something that had happened to pipelines in the area in the past.

Also on Jan. 23, Exxon agreed to a $2 million settlement of claims relating to seven private properties impacted by the oil spill.