(Adds lawyer's comment)
By Nia Williams
July 24 (Reuters) - A Native American tribe in Wisconsin is suing Enbridge Inc in a bid to shut down an aging oil pipeline that runs across its tribal land, the latest in a string of challenges against the Canadian company's pipelines in the U.S. Midwest.
The Bad River Band filed a federal lawsuit against Enbridge on Tuesday in the Western District of Wisconsin, asking for the section of Line 5 that runs across its reservation to be decommissioned and removed because of the risk of a leak.
The 66-year-old pipeline carries 540,000 barrels per day of light crude and propane from Alberta to refineries in the Midwest and Ontario and is a critical part of Enbridge's Mainline network, which delivers the bulk of Canadian oil exports to the United States.
The band is most concerned about a section of Line 5 near the Bad River, where bank erosion could soon leave the pipeline exposed to the full force of the river, the lawsuit says, describing the situation as a "looming disaster."
"We want the constant threat of that pipe eliminated. We want it out of our aquifer and the greater Bad River watershed," Mike Wiggins Jr., acting tribal chairman of the Bad River Band, told Reuters on Wednesday.
Pipeline easements, which are agreements allowing Enbridge to use Bad River land, expired in 2013. The lawsuit argues the continued use of Line 5 constitutes trespassing and seeks an injunction that would force Enbridge to cease operations and remove the pipeline.
The Bad River Band and Enbridge have been in negotiations regarding the easements since 2013 but Wiggins Jr. said there were "irreconcilable differences" between the two parties.
Enbridge spokesman Michael Barnes said the company needed time to review the contents of the legal filing. Most of Line 5's right of way through the Bad River reservation is not affected by the dispute, he added, because it is covered by different easements.
Enbridge faces a difficult situation because tribes have authority over their own lands and cannot be forced to allow pipelines to operate, said James Freeman, a partner with law firm Zabel Freeman in Houston.
"It's not a good thing one way or another if Enbridge cannot work out an agreement with this tribe," Freeman said.
Line 5 is also facing a court battle in Michigan, where the state filed a lawsuit last month asking for an underwater section of the pipeline that runs beneath the Straits of Mackinac in the Great Lakes to be decommissioned.
In addition, Enbridge faces delays on its Line 3 replacement project, which would double capacity on a different pipeline carrying oil from Alberta to the Midwest, after a Minnesota court ruled that Enbridge's final environmental impact statement was inadequate. (Reporting by Nia Williams Editing by Chris Reese and Tom Brown)