Another battle is brewing over piping heavy Canadian crude oil across Minnesota.

Anti-pipeline activists who in July disrupted the Minnesota Public Utilities Commission as it approved a cross-state pipeline expansion say they'll be back this week, demanding to be heard on another upgrade.

Enbridge, the Calgary-based operator of the 1,000-mile "Alberta Clipper" pipeline, plans to boost its capacity another 40 percent to 800,000 barrels per day.

In July, it won PUC approval for a smaller capacity increase.

The expanded line from Hardisty, Alberta, to Superior, Wis., would import more oil from Canada's tar sands region. Environmental activists who oppose the expansion cite Enbridge's safety record and concerns about increasing greenhouse gas linked to climate change.

"Enbridge is responsible for the largest on-land spill," said Tom McSteen, lead convener for the anti-tar sands group MN350. He's referring to the July 2010 rupture of an Enbridge pipeline in Michigan that released 20,000 barrels of crude oil, much of it into the Kalamazoo River, triggering a record fine and a $1 billion cleanup. "We don't want a Kalamazoo in Minnesota," he added.

When activists showed up in July at the PUC in St. Paul, they interrupted the meeting, shouting their opposition to Enbridge's first expansion. It was approved anyway, with virtually no discussion by commissioners.

Next steps

Regulators on Wednesday will probably decide whether more debate is warranted on the second expansion. Pipeline opponents including MN350 and the Sierra Club want the commission to subject the project to a triallike process that could take months. Enbridge would be forced to prove to an administrative law judge that the expansion is needed and would be safe.

The state Commerce Department and the PUC staff have endorsed a "contested case hearing" involving lawyers, fact-finding, an evidentiary hearing and legal arguments.

In the end, a judge would issue a recommendation on the expansion, with the final decision left to the PUC.

The $159 million upgrade would add pumping stations to increase the pressure and carrying capacity of the 36-inch line. It went into service in 2010, and was designed so its capacity could be expanded by increasing the pressure, Enbridge says.

The company wants a streamlined regulatory review. That process allows anyone to comment at public meetings and in writing. The PUC used that process to approve the first-stage, $40 million pump-station upgrade, which still awaits a federal permit.

Enbridge says the second expansion is needed because oil shippers and their customers, including Twin Cities refineries, could be slapped with quotas as Canadian oil output ramps up and pipelines become oversubscribed. That has happened in North Dakota, where 68 percent of that state's oil bounty is shipped to market in railroad tank cars. Enbridge plans to build another pipeline from the Bakken oil region to deliver that oil.

In a state regulatory filing, Enbridge defended the safety record of the Alberta Clipper line, saying the pipe's outer, anti-corrosion coating is better than that used on the 1960s-era line that failed and leaked undetected for hours into the Kalamazoo River near Marshall, Mich. The company said it dismissed some employees, changed operators' response procedures since the 2010 accident, and is looking at adding more remote-operated valves.

"Clearly, the Marshall incident was one of the worst in Enbridge's history, and it is one we don't want to repeat," said Lorraine Little , an Enbridge spokeswoman based in Duluth.

At the state's request, Enbridge submitted data on all 56 reported crude oil spills in the past five years on its Midwest pipeline system. Minnesota had the most accidents but the least amount spilled among the six states, the data show. Most releases were small, and occurred at terminal and pumping facilities, not on the line. Enbridge's worst Minnesota accident happened in 2007 (before the five-year period), when two company maintenance workers died in an explosion and fire on a pipeline near Clearbrook, Minn.

'Substantial disagreement'

The oil industry has pushed back against tar sands pipeline criticism, citing a National Research Council study that found that the Canadian heavy oil known as diluted bitumen is no more corrosive than other crude. The industry also rejects the comparison that greenhouse gas emissions from tar sands oil far exceed those from other heavy oil extraction.

"You have to evaluate the carbon emissions of any crude oil measured from the time it is removed from the ground until it goes into your gas tank, and when you measure it on that basis … the oil sands crude is comparable to any heavy crude we have imported from other countries like Venezuela and Nigeria," said Dan Gunderson, a spokesman for the American Petroleum Institute, the industry's trade group.

The issue facing Minnesota regulators is not whether to approve the second expansion — that's to be decided later — but whether to authorize an extensive review of it.

The state Commerce Department, which advises the PUC on utility issues, supports a contested hearing. In a recent filing, the agency said "many members of the public raised various concerns," and assessing the need of this expansion "may be more complex" than the first one. The PUC staff cited "robust concerns with the environmental effects of the use of petroleum products such as heavy crude oil" and "substantial disagreement" among parties over interpreting laws and rules.

MN350, which says it's loosely affiliated with the climate change group founded by environmentalist Bill McKibben, has questioned the need for the expansion project, saying that too much of the oil would be shipped out of state. McKibben and his group 350.org have organized against TransCanada's proposed Keystone XL pipeline, which would import the same type of oil through western states.

"If Keystone XL gets built, I think there is a great risk that the two companies could easily bring on their capacity to ship from Canada at about the same time and you could see lot of excess pipeline capacity for a number of years," said Paul Blackburn, an attorney for MN350.

Enbridge says it doesn't invest in pipelines unless the demand exists. It also doesn't deny that Canadian oil is headed to many U.S. refineries, but says refiners in Rosemount and St. Paul Park stand to directly benefit — or lose if the expansion isn't approved.

David Shaffer • 612-673-7090 @ShafferStrib