Line 6B of the Lakehead oil pipeline system ruptured in late July near Marshall, Mich., dumping around 20,000 barrels of oil into the Talmadge Creek and Kalamazoo River.
Enbridge in its annual report said it spent $550 million on the July spill, excluding insurance costs, fines and penalties.
The company spent another $45 million related to a similar accident in September in Illinois. Line 6A of the Lakehead pipeline network near Romeoville, Ill., spilled oil onto a roadway and into a nearby retention pond Sept. 9.
Repairs and cleanup costs wound up contributing to the company's first operating loss in at least five years.
U.S. Transportation Department Secretary Ray LaHood said his agency adopted a plan to make sure operators know the age and condition of their pipelines. Additional regulations would strengthen inspection requirements and provide more public access to safety records.
Pipeline operators could face penalties of as much as $2.5 million for a string of violations.