A branch of the Lakehead oil pipeline system ruptured July 26, spilling about 20,000 barrels of oil in the Talmadge Creek and Kalamazoo River in southern Michigan.
Enbridge Energy Partners, the Canadian pipeline operator, pulled about 50 feet of the broken line from the ground for federal investigators examining the leak. Federal regulators said it could take at least 12 months to carry out their investigations.
Meanwhile, the Pipeline and Hazardous Materials Safety Administration is reviewing revised plans submitted Friday by Enbridge to restart the pipeline.
Michigan's U.S. Sens. Carl Levin and Debbie Stabenow, both Democrats, in a letter to the PHMSA called for patience regarding the restart plan.
"How can PHMSA approve a restart plan for the ruptured line when the cause of the leak has not yet been determined and may not be found for another 12 to 18 months?" they asked in their letter.
Republican lawmakers last week said Enbridge failed to repair around 200 so-called anomalies on the Lakehead pipeline system last year, opting instead to lower the pressure on the pipeline.
"We ask that you continue to prioritize safety when reviewing any modified restart plan submissions by Enbridge," Levin and Stabenow wrote. "All precautions should be taken into account to ensure that any reopening of this pipeline begin only when the PHMSA is fully confident that the line restart can be done in a safe manner."