Hoping to relieve a shipping bottleneck for Canadian and North Dakota oil, Enbridge Energy on Monday filed plans with state regulators to boost capacity by 27 percent on its Alberta Clipper pipeline, which carries crude though northern Minnesota to Superior, Wis.

The project is part of $600 million in pipeline upgrades in the United States and Canada that Enbridge announced in May to carry more oil from Hardisty, Alberta, to terminals in Wisconsin and Illinois.

In a filing with the Minnesota Public Utilities Commission, Enbridge said it will spend $40 million to upgrade three Minnesota pumping stations, at Viking, Clearbrook and Deer River, allowing them to push more oil through the 36-inch Alberta Clipper pipeline.

"This project will increase the pipeline capacity ... in order to meet North America's growing need for reliable transportation of crude oil supplies from growing production regions in Western Canada and North Dakota and surrounding regions," Enbridge said in its filing.

When it constructed the 1,000-mile Alberta Clipper three years ago, Enbridge installed pipe with a larger diameter than it needed, anticipating a later upgrade. The capacity will go from 450,000 barrels per day to 570,000, the company said.

The upgrade won't require replacement of existing buried pipeline. Landowners are being notified about the project by mail. It is expected to create 38 permanent jobs after its completion in 2014, the company said.

Enbridge, based in Calgary, Alberta, said refineries in the Chicago, Detroit and Toledo, Ohio, areas could get more oil shipments though the higher-capacity pipeline. Other end users, from Minnesota to the Gulf Coast, also stand to benefit, the company said.

The pipeline through northern Minnesota has become such a bottleneck that a company proposing the High Prairie Pipeline across North Dakota has accused Enbridge of favoring Canadian crude over crude from the Bakken field in western North Dakota and eastern Montana. The discrimination allegation is pending before federal regulators.

David Shaffer • 612-673-7090