TRAVERSE CITY (AP) - Three U.S. senators asked a federal agency Wednesday for evidence that a pipeline crossing a section of the Great Lakes is safe, following a roughly 10 percent increase in its capacity to carry oil.
Enbridge Energy Partners LP boosted the capacity of its Line 5 pipe earlier this year by 2.1 million gallons from 20.6 million. The line runs from Superior, Wis., to Sarnia, Ontario, passing through the Upper Peninsula and crossing the Straits of Mackinac, a five-mile-wide area where Lakes Huron and Michigan meet.
In a letter to the Pipeline and Hazardous Materials Safety Administration, Sens. Carl Levin and Debbie Stabenow of Michigan and Richard Durbin of Illinois noted the line is 60 years old and questioned its durability in the straits, where currents are strong and water temperatures variable.
"If the pipeline running beneath the Straits of Mackinac were to leak or burst, it could have devastating effects on the Great Lakes and the entire region's economy," they said.
Another Enbridge pipeline ruptured in southwestern Michigan in 2010, spilling about 843,000 gallons of crude into the Kalamazoo River and a tributary creek. It was the largest inland oil spill in the nation's history.
Enbridge spokesman Larry Springer said the company performed tests that verified the higher volume of oil running through Line 5, part of the company's Lakehead network, would meet pressure and capacity guidelines. PHMSA reviewed the results, he said.
"This line is very well inspected," Springer said. "We have very good confidence that this pipeline is fit for service in that environment."
Line 5 is 30 inches in diameter except when crossing the straits, when it divides into two 20-inch pipes. Springer said that section is about 1 inch thick and seamless, the better to prevent leaks. The exterior is inspected regularly with remote underwater vehicles, while the interior is checked with tools that look for corrosion, dents and cracks, he said.
The line carries light oil and liquefied natural gas, in contrast to the line that ruptured, which carried heavy crude.
The three Democratic senators asked PHMSA for information about tests performed on Line 5.