By Nia Williams
CALGARY, Alberta (Reuters) - Canadian company Enbridge Inc <ENB.TO> said on Tuesday it had received a permit from the U.S. Army Corps of Engineers to install 54 steel supports along its underwater Line 5 pipeline in Michigan's Straits of Mackinac.
Line 5 ships 540,000 barrels per day of light crude oil and propane and is a critical part of Enbridge's Mainline network, which delivers the bulk of Canadian crude exports to the United States.
It has attracted fierce opposition from many environmental campaigners, who fear the underwater portion of the 66-year-old pipeline could leak oil into the Great Lakes.
The state of Michigan is suing Enbridge in a bid to have the underwater portion of Line 5 shut down and decommissioned and has rejected Enbridge's suggestion that it build a tunnel under the Straits to house the pipeline.
In August Enbridge identified a span, or gap between the pipe and the lakebed, exceeding 75 feet, which under easements granted by the state of Michigan is the limit for each span.
Company spokesman Ryan Duffy said Enbridge had been waiting 17 months for the permits and upon receiving them started work immediately to install a support at that span. Work on that section is expected to be completed later this week, weather permitting, and the other steel supports will be placed at different locations along the pipeline.
"Enbridge believes that the tunnel project is the best long-term solution for Line 5 moving forward. Placing the pipeline inside a tunnel, 100 feet below the lakebed, would eliminate any span issues, and the need for supports," Duffy said in an emailed statement.
The Michigan Attorney General's office did not immediately respond to a request for comment.
(Reporting by Nia Williams; Editing by Leslie Adler, Cynthia Osterman and Tom Brown)