Line 6B of the Lakehead oil pipeline ruptured in July 2010 near Marshall, Mich. The EPA estimated more than 23,000 barrels of heavy oil from Alberta tar sands spilled from the pipeline into the Kalamazoo River and nearby Talmadge Creek.
The energy company initially estimated the cost of the cleanup and potential claims at $430 million, then later to $585 million. In its latest filing with the Securities and Exchange Commission, the company said it expects the cost to be $700 million, WOOD TV 8 in Grand Rapids, Mich., reports.
The U.S. Environmental Protection Agency said it spent more than $29 million cleaning up the spill.
The EPA recovered about 18,000 barrels of oil from the surface. Officials said it was unclear how the remaining oil would affect the environment because there is no spill with which to compare the Enbridge leak.
The nature of oil from tar sand deposits causes some of it to sink to the river bottom where it soaked about 6 inches of sediment.
The EPA set an Aug. 31 deadline for Enbridge to remediate parts of southern Michigan affected by an oil spill in July 2010. Enbridge spokeswoman Lorraine Grymala said earlier this month the EPA set the deadline before the extent of the spill was reviewed this summer.