Fire and rescue crews from Two Harbors placed containment booms in Lake Superior's Agate Bay on Wednesday morning to rein in what was thought to be a fuel slick just west of the ore docks in Two Harbors.
But it turned out the reported slick was taconite -- probably dust particles -- sitting on the water, the Coast Guard reported.
Aaron Gross, the chief of response for the Marine Safety Unit of the Coast Guard in Duluth, said it was nearly impossible for response crews to discern the difference between oil and taconite dust until they got to where the dust sat on the water.
Gross said he has seen pollen or other organics create conditions that look like a fuel slick but rarely one formed by taconite.
"I'm surprised it didn't sink," Gross said. He had a vial of water from the site at his office. He said the taconite poses no threat to the environment and the booms were released as soon as the taconite determination was made.
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The response was a "nice test" for a real emergency, Gross said.
"We much prefer this to actual oil," he said.
The Coast Guard had been working with ore dock owners CN and Two Harbors fire and rescue teams for a required containment practice drill later this summer. Many Two Harbors crew members thought the call Wednesday morning could have been part of that testing.
Gross said the response was good. CN responders were there as well, and Wednesday's scramble might fulfill the federal mandate for a practice.
"I'll have to call and see if this would count," Gross said.
The purported spill was contained to the corners of a breakwall off what is called Pork City Hill, west of the ore docks. About 4,000 feet of boom was used and those in response boats near the affected area said it could be enough to contain it until Coast Guard crews from Duluth arrived at noon.
The alarm had been sounded about 9:30 a.m., when Greg Hanson of Two Harbors called in what he saw as a fuel spill after returning from fishing on the lake.
"It was red," he said. "It looks a lot like the stuff in the Gulf that you see in pictures on TV."
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Officers from the Lake County Sheriff's Office and the Minnesota Department of Natural Resources were also at the scene.
