Just across the street from the Mall of America, down a hill and hidden by trees, a stream bubbles out of the limestone bluffs.

The clear water flows through a verdant ravine bordered by watercress and wildflowers to the Minnesota River. The creek is less than a mile long, but pure enough and cold enough to offer a rare opportunity: restoring native brook trout that flicked through the water decades ago.

"It's not a stream that's on any designated waters maps," said Vicki Sherry, wildlife biologist at the Minnesota Valley National Wildlife Refuge that owns the property. "It's kind of a little hidden treasure that nobody really knew about."

Sherry called the Minnesota Department of Natural Resources and the Twin Cities chapter of Trout Unlimited seven years ago and said the stream reminded her of Michigan trout streams she had studied early in her career.

After initial disbelief that a pristine stream might be so close to the sprawling shopping complex, DNR fisheries expert Mark Nemeth made a visit and was immediately hooked. He studied the stream closely for the next two years.

"It had the flow, it had the water temperatures, and it had the insect community capable of supporting trout," he said. "The only thing it didn't have was trout."

That changed in 2007, when DNR and Trout Unlimited stocked the stream with 1,450 brook trout.

About 150 have survived and reproduced, but no fishing is allowed -- even catch and release -- because the population is still too vulnerable.

Replicating nature

The stream has one big problem, as far as fish are concerned: a dam.

The former owners of the property, the Izaak Walton League, installed a small dam in 1926 to capture and pool its water. The conservation group then diverted the water to circulate the clean water through several fish rearing ponds used to stock area lakes until the 1950s.

To honor that work, Sherry and others have started calling the stream "Ike's Creek."

But the dam breaks the steam into two parts, and the trout need the full run of the stream to thrive.

"There's limited area to reproduce and they're losing their connectivity with the better spawning habitat and better nursery habitat upstream of the dam," said Nemeth.

So the dam had to go.

During the past two weeks, DNR crews removed it and temporarily diverted the upper stream while they reconstructed the creek the way it once flowed, with a natural gradient and a meandering route. As Nemeth watched recently, a huge excavator picked up large red pine logs and maneuvered them into position. Workers arranged them in pairs into a series of inverted V-shaped structures pointing upstream. The logs will create six-inch steps that trout can cross to move freely up and down the stream.

"The water will flow over the logs and scour out small pools, and fish can sit in there," said Tony Nelson, habitat chair of Twin Cities Trout Unlimited. "You're also putting oxygen in the water, and giving them a place to hide."

Partnerships in play

The $45,000 project includes contributions from the fishing group, the wildlife refuge, the DNR and a grant from the Outdoor Heritage Fund.

Nelson said Trout Unlimited is usually associated with rehabilitating and improving trout streams for anglers, but not in this case.

"Even if this never becomes a fishable stream, just to have these species in the city tells everyone that we're doing a better job," he said. "We're maintaining some level of wildness even in the heart of the city, and that's a great thing."

The creek is near wildlife refuge trails that lead to Bass Pond and other areas in the bottomlands near the Minnesota River.

That will make it a special place for school groups, hikers and others to see how a trout stream looks, and how cold it feels, and perhaps to catch a glimpse of the elusive "brookies," Nelson said.

Water began flowing into the reconstructed creek bed last Thursday, and two dozen volunteers began to stabilize its banks on Saturday with erosion fabric mats and tree plantings. That work and additional seeding with native plants will continue this week, said Sherry.

"It's a rare habitat for the Twin Cities metro area," she said. "With the flowing groundwater and the constant temperatures, this stream stays open all winter, and the trout are in here year round."

Tom Meersman • 612-673-7388