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Frozen river: How clean energy is ending winter boating on the urban Mississippi

As the winter chill barreled into Minnesota this winter, a curious transformation took hold on a big stretch of the Mississippi River that lies above St.

The Riverside power plant
MinnPost photo by Mike Mosedale
The Riverside power plant: Did the plant’s Bubbler keep the river from freezing over?

As the winter chill barreled into Minnesota in early December, a curious transformation took hold on a big stretch of the Mississippi River that lies above St. Anthony Falls. At first, the change was hardly perceptible. The river ice, which usually builds slowly along this industrial section of Minneapolis waterfront, simply seemed to be forming at a faster clip.

Frigid weather was the most obvious explanation. But as the month wore on and the Mississippi froze bank to bank, more in the manner of a lake than a flowing river, that answer was no longer entirely satisfying. In the recent past, on all but January’s coldest days, there was always a ribbon of open water running through the main channel.

This band of water appeared as a dark blue streak, gloriously conspicuous against the winter white backdrop of snow and ice. In mid-winter, it typically stretched from Xcel Energy’s Riverside power plant, past the Lowry Avenue Bridge and south to the Broadway Bridge.

On milder days, while the city lakes remained stubbornly frozen, winter surrendered quickly on the river. The receding ice would leave a skinny shelf along the shoreline and a fat slice of open water that snaked down to the Plymouth Avenue Bridge, sometimes all the way to St. Anthony Falls.

Because there is so little ice-free water in Minneapolis during winter, this most unnatural-looking stretch of river — with its barge docks, sprawling scrap and gravel yards, and other vestigial remnants of the city’s industrial past — attracted an enormous amounts of wildlife. The winter-time congregation included Canada geese by the hundreds, mallards, golden eyes, bald eagles, even the occasional trumpeter swan.

Like Bogart in Casablanca, they all came for the waters. But this year, the few birds loitering in the old neighborhood might want to echo Bogart’s famous retort to Claude Rains’ observation about the lack of waters in Casablanca: “I was misinformed.”

By mid-December, only a single pool of water remained in the traditional wintering spot below the Lowry Avenue Bridge. A big flock of geese, assisted by a smaller number of mallards, kept it ice-free for a few weeks. Then that, too, finally froze over and the birds moved along in search of open water.

Strange pleasure: winter boating
I suspect the geese and ducks are perturbed by this winter’s ice-locked river. I certainly am. Having lived in northeast Minneapolis for most of the decade, I have spent countless hours exploring the local waters in a 16-foot aluminum fishing boat, much of the time in  the winter months. On the nicer days, I would shove the boat prow-first across the ice shelf and clamor into the stern once it started to break into open water.

Over the years, boat rides on the winter river became a favorite pastime. I took my wife on such an excursion on our first date. The sharing of that weird experience — the shoehorning of a summer activity into the middle of winter, the comic incongruity of bouncing over waves while simultaneously being pelted in the face with snow, the near solitude in the midst of the state’s biggest city — kicked off the courtship in style.

As we trolled through ice flows in the night, the loose ice pinged off the side of the boat, making a lovely clinking sound, like toasted Champagne flutes. Occasionally, we passed through giant flocks of Canada geese. Sometimes, the birds would quack at our approach, bobbing up and down in the current with a faint, murmuring concern. Other times, they would flee en masse, shattering the winter’s hush with the drumbeat of wings and a chorus of angry honks.

Lacking much in the way of spiritual impulses, I am embarrassed to admit that I found these experiences utterly transcendent. This stretch of the Mississippi lacks the grandeur of the section of river that lies below St. Anthony Falls, which is the only true gorge between the headwaters and New Orleans and boasts steep forested banks and lovely vistas. But in winter especially, I found the river above the falls an exhilarating place to explore, full of rich contrasts between heavy industry and the natural world, full of life.

When people told me I was likely to drown if I kept taking the boat out in snowstorms, I shrugged. From an actuarial point of view, they were right. The river’s wintertime majesties — and the spell they cast on a vulnerable sucker like me — are hard to explain.

With the Mississippi now locked up solid with ice, this winter has denied me that old, odd pleasure. And it left me wondering: What changed? 

The Bubbler hypothesis
In casual conversations with my fellow river rats, the subject of the unusual ice conditions has come up often lately. One neighbor — a houseboat dweller with a long history on the water and a lot of strongly held opinions — at first insisted there was no hidden explanation for the ice accumulation. It was just the damn cold. But over time, he too was swayed by the persistent absence of any open water on our little stretch of the river.

In late December, I started venturing out on the river ice on foot, mainly in the vicinity of Gluek Riverside Park, where I drilled a bunch of holes with an auger. To my surprise, I consistently found 8 to 12 inches of solid ice. In previous years, I would have been very reluctant to walk in those same spots.

The view of the frozen river from the Lowry Avenue Bridge
MinnPost photo by Mike Mosedale
A view of the frozen river from the Lowry Avenue Bridge.

Walking on river ice can be hazardous, especially if you don’t have a solid understanding of local conditions. On Dec. 9, a 39-year-old south Minneapolis woman out exercising a friend’s dog fell into the river near the Camden Bridge. Her gloves and cell phone were found near a hole in the ice.

But my confidence in the particular ice I was exploring — located not far downriver from the scene of that poor woman’s death — was bolstered by a theory I developed: It was the Riverside power plant Bubbler that had kept the river open and now it was locked solid. Therefore, something must be amiss with the Bubbler.

The Bubbler is not an official term; it’s just how my fishing buddies and I refer to a particular spot in the main channel where warm water is discharged from the power plant. The discharge bubbles up from the depths, creating a visible roil, or bubble, on the surface.

I was intrigued by the Bubbler for years. When I first came across it, I liked to joke that the bubbles came from the river’s version of the Loch Ness monster. Later, I developed a more practical-minded interest in the Bubbler, a fisherman’s interest.

As most anglers know, the majority of Minnesota fish — and virtually all fish found in the Mississippi — prefer water temperatures above 50 degrees. So when water temperatures in the river fell below 50 degrees during the winter, spring and fall, I often anchored by the Bubbler, where the water was often five or six degrees warmer, and tried my luck with a night-crawler or fathead minnow.

While I never limited out at the Bubbler, I graphed plenty of fish on my depth finder. On a few occasions, I boated a walleye or a channel catfish there when I couldn’t raise a fish anywhere else.

Then, last month, as I was shooting photographs of a flock of geese struggling to maintain their open water hole below the Lowry Avenue Bridge, I looked upriver towards the Bubbler. I saw nothing but ice where the Bubbler should have been. The Bubbler wasn’t bubbling.

A culprit identified: clean energy
For the past several years, the Riverside power plant has been the site of a massive, $250 million reconstruction effort, part of Xcel’s so-called MERP (Metro Emissions Reduction Project). Under the MERP, the utility is shifting its fuel source at Riverside from coal to natural gas.

As an environmental proposition, this is an obvious improvement. The oldest coal burning plant in the state, Riverside had also long been one of its dirtiest. The conversion will lead to 100 percent reduction in the emission of such harmful pollutants as mercury, sulfur dioxide, and particulates (along with a 99 percent reduction in nitrogen oxides, which create ground level smog). It will also add 80 megawatts to the plant’s generating capacity.

And it will change the nature of the river.

Jeff Ricker, a manager at Riverside plant, said Xcel has nearly burned through the last of its coal reserves in preparation for the switchover to gas in May. As a consequence, he explained, the warm water discharge into the river has been minimal this winter.

While the refurbished, gas-powered plant will also discharge warm water once it is fully functional, Ricker expects the quantities to be greatly reduced. One reason: unlike a coal-fired plant, generators that run on natural gas can be turned on and off with relative ease. That will lead to savings during periods of lower demand, or when other energy sources — such as wind — are pumping more power into the grid.

“We used to run all the time. With the new plant we’ll probably run 30 percent of the time,” added Ricker.  “So in the future, there will be a lot less heat released to the river.”

That will probably be a good thing for the local fish populations which can be harmed when water temperatures exceed 90 degrees. As a condition of its operating permit, Xcel is required to monitor the water temperature down river from the plant. On several occasions, when the river temperatures at the Lowry Bridge exceeded 86 degrees, the utility was required to shut down. 

Only constant on the river: change
Up and down the Mississippi, power plants — and their attendant warm water discharges —  have imposed some dramatic changes on the river. Before the Prairie Island nuclear plant opened in 1973, Lake Pepin usually froze hard enough to accommodate vehicle traffic. Many winters, a road was plowed between Lake City and Stockholm, Wis., so that motorists didn’t have to drive around Lake Pepin to cross state lines.

The warm water discharge from Prairie Island radically altered the ice dynamics, according to Mike Davis, a river ecologist with the Minnesota Department of Natural Resources who grew up in the area. “When I was a kid there were fish house villages all around Lake Pepin. Today there are very few out there,” he recalled. 

In part, that’s due to safety concerns about driving on suspect ice. But it is also because the warm water from the nuclear plant “completely changed” the wintering behavior of the fish. Ice fishing on Pepin has never been the same because the fish that used to over-winter there have been lured upstream by the warmer temperatures from the nuclear plant.

A cross-country skier’s perspective
While I’ve missed the proximity to open water this winter, Cory Parkos, a former neighbor who now lives in Columbia Heights, has reveled in it. Despite the loss of a leg in a motorcycle accident, Parkos is an enthusiastic cross country skier. He enjoys skiing on smooth, flat surfaces, so he often skied along the river’s edge.

Wary of open water and thin ice, Parkos typically hugged the shorelines. This year, he ranged out over deeper water. “We were skiing 10, 15, 20 feet from shore. There was a beautiful layer of ice, with a good amount of snow. Perfect bed for skiing,” Parkos said.

A few weeks ago, Parkos skied from Gluek Riverside Park to Boom Island — a trip he’d never before completed owing to concerns about ice thickness. “There were a lot more people down on the ice than I’ve ever seen before,” he said. “People were just out venturing and exploring. I never used to see that.”

While Parkos said he likes the better quality of the ice, he couldn’t help but infer a larger significance to the unfamiliar aspects of the winter river. “It just seems congruent with the economy and the times,” he said, a little ruefully. “Everything is kind of shut down and frozen.”

Mike Mosedale reports on the environment, Indian affairs and other topics.