Line 6B of the Lakehead oil pipeline system ruptured in 2010, spilling about 20,000 barrels of so-called tar sands oil into the Kalamazoo River in Marshall, Mich.
Enbridge, the pipeline's operator, announced it received a notice of probable violation from the Pipeline and Hazardous Materials Safety Administration. The PHMSA, in its notice, said there were "multiple violations" during the incident and proposed a $37 million penalty, the largest ever for the agency.
Stephen Wuori, president of the pipeline division at Enbridge, said safety is a paramount concern for his company.
"Enbridge completed a detailed internal investigation of this incident in the fall of 2010 and has made numerous enhancements to the processes and procedures in our control center since the Line 6B accident, including the training provided to pipeline operators, and has made significant changes in this critical component of our operations," he said in a statement. "Incident prevention, detection and response have also been enhanced."
A preliminary investigation into the incident suggested Enbridge operators misinterpreted alarms that indicated a leak occurred in Marshall. Enbridge said it wouldn't comment on the PHMSA notice until it reviews the findings.