The department's Pipeline and Hazardous Materials Safety Administration announced it started an enforcement action against Exxon Mobil Pipeline Co. The PHMSA said it was proposing a $1.7 million fine in response to allegations the company didn't address the risks of river flooding, scour and erosion to its Silvertip pipeline system.
Exxon in October said it expected to pay more than $100 million in cleanup operations for the July 2011 rupture near Billings, Mont. An estimated 1,500 barrels of oil spilled from the Silvertip pipeline into the Yellowstone River in the incident.
Scouring of the pipeline, which was about 4 feet below the river bottom, is suspected of contributing to the rupture of Silvertip. The PHMSA also alleged that Exxon failed to establish written emergency response plans for its staff in the event of a spill.
Exxon has since bored holes under the river to bury the pipeline deeper beneath the surface. The company had no public comment on the PHMSA decision.