ITASCA TOWNSHIP, Minn. -- The boggy ground jiggled underfoot as Paul Stolen walked along La Salle Creek, a tiny wetland stream whose banks are staked with orange plastic posts that say, "Warning, Petroleum Pipeline."

"There's water flowing beneath the ground," said the retired Minnesota Department of Natural Resources biologist.

And crude oil too.

This remote wetland near Itasca State Park, already undercut by three crude oil pipelines, is one of several fragile, isolated habitats along the proposed path of the 610-mile Sandpiper crude oil pipeline across northern Minnesota.

The $2.6 billion project would help fix a problem in North Dakota's booming oil fields. The bounty of almost a million barrels of crude per day far surpasses the capacity of pipelines to refineries in the Midwest and beyond.

The Sandpiper pipeline would be one of the largest across Minnesota, delivering an additional 375,000 barrels daily to Superior, Wis.

But the ecological risk of adding another major pipeline in places like La Salle Creek is raising alarm among state environmental officials. For the first time, the Minnesota Pollution Control Agency (MPCA) is questioning whether more pipelines should be built through the state's lakes region.

In a new analysis of the proposed Sandpiper route, the agency said the line would cross 28 rivers, lakes and wetlands that can't be reached from nearby roads. At La Salle Creek, for example, it would be "extremely difficult if not impossible" to bring in cleanup equipment if an oil spill occurs, the agency said.

"The environmental damage that would occur as a result of a leak in this location could be massive," agency officials said in a letter to state regulators reviewing the Sandpiper project.

Enbridge Energy, the Calgary-based company developing the pipeline, has tried to identify sensitive areas and pick the "least impactful" route, said Mark Curwin, senior director of strategic coordination for U.S. projects.

"In northern Minnesota, it is hard to avoid wetlands and water bodies when you traverse east to west," he said.

Nine pipelines already carry North Dakota and Canadian crude oil through northern Minnesota. The oldest lines were built in the 1950s and 1960s before many environmental regulations were in place.

As the pipeline network grew, pipeline builders added lines to some of the same rights of way.

When spills happen in roadless places, workers first must construct a temporary road, delaying the cleanup and restoration. The MPCA warned state regulators that "past routes have crossed too many water bodies in inaccessible areas." Even the section of the Sandpiper route that would follow a new right of way is causing concern.

At Twin Lakes near Menahga, Minn., the state analysis found, the pipeline would cross a wetland complex 1.3 miles from the nearest road. If the pipeline ruptured there, barges or boats might be needed to contain a spill, the MPCA said.

The agency urged the state Public Utilities Commission to consider pipeline routes outside of the lakes region.

Enbridge officials had hoped to start building the Sandpiper pipeline next winter.

The company also has announced plans to build another crude oil pipeline to carry Canadian oil across Minnesota, possibly adjacent to the Sandpiper line.

The Utilities Commission, which has the authority to approve or reject the Sandpiper project, is scheduled to vote Thursday on whether to review the route separately from its review of the project's need.

That decision could affect the timing of the project, but final action is months away regardless of the outcome.

Enbridge welcomes the comments from the agencies and intends to address their concerns, Curwin said. For example, he said, the company will consider adding shut-off valves at waterways as the DNR has urged.

Trip into La Salle Creek

At La Salle Creek, pipelines cross at a point where the water flows into a chain of pristine lakes. Just 3½ miles downstream, the state recently spent $8.7 million to acquire land and develop the La Salle Lake State Recreation Area.

As Stolen, the retired DNR biologist, walked along La Salle Creek, he worried about what might happen if an oil pipeline ruptured in the area.

"If it spilled here, you couldn't clean this up," said Stolen, who spent two decades reviewing the effects of projects like pipelines for the DNR. "Twenty-thousand barrels of oil could go right down to the lake."

La Salle Creek is one of more than a dozen sensitive areas that lie along the proposed Sandpiper route, according to the MPCA and the Minnesota DNR.

Others include the upper Mississippi River and the Straight River, a noted trout stream near Park Rapids, Minn.

Ten places potentially crossed by the pipeline, including the Nemadji River, Kettle River and Crow Wing River, are undergoing taxpayer-funded wetland restorations.

One area at risk is a walleye fishing spot and wild rice region in Aitkin County.

"If a spill were to occur in this stretch of pipeline, there is little to prevent it from quickly moving downstream to the walleye spawning area, wild rice beds and Big Sandy Lake," DNR principal planner Jamie Schrenzel said in a letter to state regulators.

Both agencies have suggested alternative routes, and the DNR is urging regulators to reconsider an existing right of way through Bemidji, Minn. But that route already holds six petroleum pipelines and crosses almost as many isolated water bodies, leaving regulators with tough choices.

Remote access

Although the proposed path of the Sandpiper crosses hundreds of wetlands, environmental officials are most concerned about the inaccessible ones.

At least four Minnesota crude oil pipeline accidents, including the state's biggest in 1991, required immediate construction of temporary roads, according to MPCA officials.

"Sometimes they have to build a road in a real wet area like a wetland and they do that with timber mats," said Steve Lee, head of the MPCA response unit. "They are giant timbers chained together that they lay in a wet area and basically float the road across."

Doug Bellefeuille, an MPCA official based in Detroit Lakes who has overseen spill cleanups for 17 years, says he keeps a pair of fishing waders in his trunk so he can slog through the muck as a first responder.

Enbridge is well aware of the challenges when trying to reach remote areas quickly, Curwin said. The company has emergency response plans, predefined access routes and equipment stored at five strategic locations along its Minnesota pipelines, he said.

"We know up and down the pipeline how we can get in," Curwin said.

Preparing for the worst

The company is still reeling from its worst crude oil spill.

In July 2010, a 30-inch crude oil pipeline ruptured from cracking and corrosion in Marshall, Mich., and leaked 17 hours before Enbridge detected it.

The spill sent 843,000 gallons of crude oil into wetlands, a creek and the Kalamazoo River, and triggered temporary evacuation of more than 50 houses because of high levels of benzene, a toxic component of oil.

Enbridge has spent more than $1 billion to clean up the area, roughly the price tag of the Minnesota portion of the new Sandpiper pipeline.

Federal investigators blamed the Marshall accident on "pervasive organizational failures" at Enbridge, and the company has said it expects to pay an estimated $29.6 million in federal penalties.

Curwin says the fallout from the spill has dramatically changed the company's culture ­— for the better.

He said the company has improved leak detection, upgraded pipelines and opened a new control center in Edmonton, Alberta.

It also has hired more control-room workers and given them a new rule about shutting down pipelines, he added.

"If there's some abnormal condition, whether they understand it or not," Curwin said, "the Golden Rule is to shut down the line."

As for the corrosion-protection coating that failed in the Michigan pipeline, Curwin said it "is long gone from the industry." Now, the coating is fusion-bonded "so the circumstances that contributed to the pipe failure in Marshall cannot occur on Sandpiper," he added.

One of Enbridge's worst spills in Minnesota was the 2002 rupture of a 34-inch pipeline near Cohasset, Minn. That spill dumped 252,000 gallons of crude oil into a bog. Much of the oil pooled on the ground, and officials decided to ignite it, causing a mile-high smoke plume.

Enbridge says replacing that 1960s-era line is its next big pipeline project in Minnesota. Environmental officials have generally applauded those plans because the old line has been prone to ruptures.

Yet if its replacement is built next to the Sandpiper pipeline, it could mean a fifth plastic pipeline marker on the bank of La Salle Creek.

Stolen, the retired DNR pipeline evaluator, said concentrating pipelines presents a cumulative risk that Minnesota now needs to consider.

"Why should these be sacrifice areas?" Stolen said. "At what point do you say, 'Enough is enough?' "

David Shaffer • 612-673-7090 • @ShafferStrib