Michael Nordskog [2]When Father Louis Hennepin first saw the great falls of the Mississippi in 1680, he was on furlough from a prolonged captivity at Mille Lacs Lake. The Flemish cleric and his Dakota escorts portaged downstream along the east bank on what is now Main Street in Minneapolis, then beheld the cataract he would later document to be forty or fifty feet high. This figure was exaggerated (though somewhat prescient), but empirical accuracy was never a missionary priority, and Hennepin ventured only to tally souls. The cataract was called Minirara by his guides in honor of the water’s playful descent, close phonetic kin to the nearby “laughing waters” memorialized by Longfellow. But unlike the classic bridal veil at Minnehaha Creek, here a great flood spilled over ledges across a half-mile of river, spouting and tumbling through fields of broken limestone, producing a thunder that drew the ear from miles away. The dutiful Hennepin divested the site of its evocative animism, and christened the falls for Anthony of Padua, the patron saint of lost things.

Not until Zebulon Pike’s 1805 expedition was the only waterfall on the Mississippi technically surveyed at just over sixteen feet, about as high as an upended canoe. This natural wonder quickly became a scenic refuge for southern tourists escaping the summer heat. But money men were also scheming along the riverbanks, seeing only industrial power uncapitalized, and by 1870 the falls had been completely harnessed by the young city’s industrial pioneers. They had no notion that their seizure of the river’s power also halted a geologic process in its final moments.

The St. Anthony Falls of the seventeenth century—splendid, romantic, and terrible as they were to Dakota and Franciscan alike—were the faint echo of their cataclysmic origins just downstream from St. Paul. A dozen millennia ago, a surge of ice-age runoff first flooded over and eroded the stubborn Platteville limestone to create a cataract just as impressive as today’s Niagara Falls (another natural wonder first documented by Father Hennepin). Absent the ambitions and interventions of Minneapolis millers, the river would by now have eroded to the last reach of the Platteville limestone twelve miles from its start, and our legendary falls would have dissolved into a series of rapids through the underlying sandstone.

Even the newest residents of condominia overlooking this site should recognize St. Anthony Falls’ major components: the central spillway, or apron; the millpond fronting St. Anthony Main, which once powered a large share of the city’s industry but now generates a thread of the electricity we consume; and the boondoggle Upper St. Anthony Falls lock on the downtown side.

There’s a fourth component, however, that has for decades gone virtually unnoticed: The St. Anthony Falls Laboratory, a bastion of water-power research embedded in the middle of the river on Hennepin Island. Rampant nature created these falls, but engineers have preserved them, and so it is most fitting that the last significant use of the Falls of St. Anthony is a playground for engineers.

 

By the time Lorenz Straub, a native of Kansas City, came to the University of Minnesota in 1930, the university had been pondering for decades a laboratory that would use the power of the falls to model natural processes. Civil engineering had begun to come into its own in America, and Straub was among the last generation who would need to travel to Europe to best learn the bedrock principles of this science. He returned from his studies in Germany excited to create engineering solutions to such tragedies as the Mississippi flood of 1927, which displaced 700,000 people in southern states, a disaster comparable in scope and impact to the aftermath of Hurricane Katrina.

Despite the Great Depression, Straub took on a host of bureaucracies and got the lab built, aided by two considerable benefactors. The city of Minneapolis contributed a riverfront site along with the rights to five mill powers of energy, or roughly one percent of the Mississippi’s average flow. (One mill power is the equivalent of 375 horsepower, or the energy generated by a flow of sixty-five cubic feet of water per second.) And the ditch-diggers’ brigade of the New Deal, the Works Progress Administration, provided the labor to excavate such a site; blasting was impossible, because the bedrock also held in place a nearby sensitive hydroelectric plant. The thirty thousand cubic yards of stone that occupied a future spacious laboratory had to be removed manually, a project that would have taken a single laborer 250 years. (University engineers seem to have a preference for difficult burrows: the Civil Engineering building on the Minneapolis campus extends nine stories beneath Pillsbury Drive.)

Straub himself designed the facility, boring and probing the limestone just ahead of the workers, and several essential design changes resulted in hefty cost increases. But his patient and detailed assessment stood in stark contrast to the cowboy engineering of the previous century, a spirit that nearly destroyed the falls.

During the 1860s, a prosperous Yankee named William Eastman acquired the southern end of Nicollet Island, several hundred yards upstream from the falls, and the real estate came with a share in the water power on the St. Anthony bank. In 1868, when the existing mills rebuffed his demand for direct access to the falls, he proposed a tunnel beneath the river that would run from the base of the falls and bore several blocks upstream to his Nicollet Island site.

But Eastman’s engineers had not assessed the bedrock beneath Nicollet Island; had they done so, they would have learned that the stout ledge of Platteville limestone on which the mills downstream sat quickly tapered to a brittle wafer above a porous sandstone substrate. That’s why the Falls of St. Anthony—absent the dams, millponds, headraces, tunnels, aprons and tailraces of nineteenth-century industry—were destined to disappear. And that is why, a year after the project started and the ambitious six-by-six-foot tunnel was nearly complete, the river suddenly plunged through the roof of the tunnel, spouted out of the downstream end of Hennepin Island, and sluiced away the foundations of several buildings. By nightfall the city was in full fret that the falls were doomed, and for months ad hoc gangs threw everything they could find into the whirlpool, including massive cribs of Rum River pine sunk with rock, which the river swallowed like so many birds’ nests. The temporary solution was to build coffer dams around the gape and divert the river from Eastman’s irresistible shortcut. A few days after the breach, the Minneapolis Tribune understated that Eastman was “dispraised if not denounced” by his fellow citizens.

It took almost a decade to secure the falls with the expertise of the Army Corps of Engineers, led by Civil War hero General G. Kemble Warren. The corps’ solution was a subterranean concrete dike moored forty feet deep into the sandstone and spanning 1,850 feet from bank to bank. This time the requisite boring did not bring catastrophe, and the sturdy dike can still be inspected via a four-foot underground tunnel. The Army Corps’ participation in the debacle was justified with a far-flung premise: that the Mississippi above St. Paul, a toothy and perilous course attempted only by the most desperate riverboat pilots, would one day be tamed by engineers and become part of the nation’s legally designated navigable waterways.

The early mission of the St. Anthony Falls Laboratory served that goal—to master rivers through impedance and control—and one of the first projects for which Straub secured funding was a scale model of a system of locks that would allow barges to travel above the falls that ran through his lab’s basement. Completed in 1963, the Upper St. Anthony Falls lock was the final link in that project, the highest of the thirty-two locks on the river, opening onto a nine-foot navigable channel that extends upstream just beyond the Lowry Avenue Bridge.

Overcoming the falls for navigation allowed for importation of many barrels of Washington, D.C. pork, but that was the end of meaningful commerce associated with the lock: One is most likely to see this magnificent device operate for passage of tour boats or various personal expressions of gas-burning masculinity. In a perfect inversion of the original justification for its construction—to foster commerce—the Corps now defends the lock’s existence based on its relief of congestion on local highways, because gravel transported by barge would otherwise be carried on trucks. Long after the downtown mills have disappeared, the St. Anthony Falls Laboratory remains a thriving concern, a solid, homely building recently adorned with bright banners to announce its presence to the public. The new director, in a reversal of Straub’s expatriate thirst for knowledge of fluid mechanics, arrived from Greece via the University of Iowa and Georgia Tech. “I received congratulatory emails from colleagues all over the world—New Zealand, Australia, Japan, Europe—when I announced that I would take the job here,” said Fotis Sotiropoulos, who accepted the directorship last year. He likes to point out that the lab’s reputation in the international scientific community stands in stark contrast to its anonymity here in the Twin Cities.

Besides building grand models exploring how rivers could be mastered and contained with locks and dams, the lab has been long involved in such pedestrian pursuits as standardization; staff measure, for instance, the rate of flow through a specific culvert design—not exactly the sort of work that seizes the imagination. But recently the lab’s scope has broadened to consider questions of sustainability. One of Sotiropoulos’ interests—exploring new ways to create electricity from tidal power—is an example. He envisions “windmills under water” moored at the bottom of New York’s East River, which could help make the city the world’s first green-powered metropolis. It’s a long hope, to energize this most profligate country’s largest city with the power of nature, but the thought of exporting engineering expertise generated by the Falls of St. Anthony—a brilliant post-industrial use of flow—would have greatly pleased the man who was the first and longest custodian of that power source.

 

Hydroelectricity was not on the mind of William De La Barre when he arrived in Minneapolis in the late 1870s, though the first hydroelectric plant in the country opened here a few years later. De La Barre was dispatched to the Mill City as an air-filtration salesman after the massive explosion of a flour mill owned by Cadwallader Washburn triggered a chain reaction that leveled most of the city’s milling capacity. Impressed by the enterprising young Austrian immigrant, Washburn engaged him to help rebuild and improve his enterprise. De La Barre could not have lucked into a better patron than Washburn, who would eventually control the rights to nearly every ounce of flow that passed over the falls.

Water power has two components: flow and head. The Mississippi’s flow is high when spring snowmelt swells the river, and generally dwindles toward an annual nadir in the early months of winter; production of flour and lumber in Minneapolis, fueled by flow, would slow correspondingly. But De La Barre spotted an obvious means of improvement: The mills were underutilizing head, the distance that the water falls before moving turbines. If Father Hennepin, first beholding the falls, was contemplating the vertical distance from the point where water first spilled over the limestone ledge to the relative calm after the river resolved its way through the field of boulders below, his seemingly exaggerated fifty-foot estimate was spot-on. De La Barre persuaded Washburn to redesign the canal that brought the river to his mills, and each turbine was set deeper into the underlying sandstone; new tailraces (the channels that bring diverted water back to the river) also relocated the outflow farther downstream. The result: The power supply to the Minneapolis mills was ingeniously doubled, and the milling season was extended.

De La Barre worked vigorously well into his eighties, and his tenure as the city’s water czar lasted until the 1930s. Convinced that “only eternal vigilance would keep the falls in existence,” he countered the competition from coal-generated steam power, which had begun to satisfy a growing municipal demand for electricity and allowed the mills to wean themselves from the mechanical power of the river. De La Barre successfully advocated for a series of headwaters reservoirs—Leech, Winnebigoshish, and Pokegama—that would store water to mitigate the river’s seasonal impotence, and this adaptation converted the falls into a steady source of hydroelectric power. The turbines of St. Anthony Falls, once used to pulverize wheat and saw logs into lumber, now spawned electricity giant Northern States Power, today’s Xcel Energy.

 

Next door to the steady thrum of hydroelectric generators, Lorenz Straub’s lab served grand engineering and hydraulics experiments around the world, making possible the mastery of its great river systems. Now that the huge ecological and social costs of such projects have become clear, the wisdom of such mastery is no longer presumed, and the lab has adapted and grown. “The lab is a unique institution because of its interdisciplinary flexibility, bringing together engineers, geoscientists, and biologists,” said Sotiropoulos, explaining how the rigors and narrow focus of hydraulic science have given way to the complexities of earth science. Recently, the lab was chosen by the National Science Foundation to host the National Center for Earth-surface Dynamics, a clearinghouse for data relevant to tectonicians, volcanists, and riparian wits worldwide. NCED was created to provide a better understanding of the many processes shaping the surface of the Earth, and in contrast to the long line of civil engineers who have run the lab, the head of NCED is a geologist, Chris Paola.

Paola is not the sort of geologist who, hammer in hand, scrutinizes ancient ledges of bedrock like the limestone slabs that jut into the basement of the lab. Most often using computer models, he seeks to understand the ancient legacies of sedimentary processes. But computer modeling has its limitations, and Paola and his former colleague Gary Parker, a civil engineer, envisioned a contraption that would reproduce, in scale, the infinitesimally slow processes of geomorphology.

No one had ever built such a device before. To carry out their scheme, Paola and Parker asked an engineer at the lab, Chris Ellis, to build a basin in the laboratory that could replicate an undulating bedrock layer; on its surface, eons’ worth of stream sediment would deposit a facsimile of the layer cake that is our ancient Earth. Ellis, smart enough to see the steepness of the trail ahead, ran the concept by a longtime friend, Jim Mullin, a man with mechanical experience but no formal training. The lab, an egalitarian outpost of the University, has the institutional smarts to recognize that such puzzles are sometimes best resolved by chemistry and collaboration, and Mullin, a pure mechanical mind without a degree, was given a salary. “His involvement made the experiment work,” says Paola. “He’s the best designer I’ve ever met.” Ellis and Mullin schemed, pondered, failed, stepped back; finally, from all their bolting and welding a functioning model came into existence.

The product is a large dynamic sandbox that the lab has playfully dubbed Jurassic Tank, and its first results drew the attention of Scientific American. The name is appropriate insofar as that geological period, along with the Cretaceous, sowed the seeds of most of the earth’s petroleum reserves, and subsurface geologists like Paola have often found willing patrons in the boardrooms of oil companies. (The Platteville limestone that outcrops into the basement of the lab, Ordovician in origin, predates the Jurassic by over two hundred million years.) While it resembles any industrial bulwark ever built in the vicinity of St. Anthony Falls, the Jurassic Tank turns the Mississippi’s flow into an agent of information—and in so doing once again forestalls the falls’ decay.

As suggested by the geologic history of St. Anthony Falls, some of the earth’s most dynamic surfaces lie along and beneath rivers, and part of NCED’s mission is river restoration; one example is the removal of dams in the American West, such as the Glen Canyon Dam on the Colorado River, silted to the chin and soon to be obsolete. Other river restoration projects will soon help create a much more visible presence for the lab: outdoor experiments will be installed on the dry spillways next to the lab and meander in plain sight of joggers and tourists on the Stone Arch Bridge. (The spillways were designed to relieve flow at flood stage but have never proved necessary.) “People in the city are unaware that there is an institution with a tremendous international reputation right in their midst,” says Sotiropoulos. “This is an opportunity for us to expand our laboratory and reveal it to the community.”

Entering its seventieth year, the St. Anthony Falls Laboratory seems fit to endure, but the ground beneath it is only as good as its latest fix. Apparently, the Army Corps never completed its repair of the falls in the 1870s after the collapse of the Eastman tunnel. According to David Wiggins, who runs the National Park Service’s Mississippi River Visitor Center in St. Paul, Corps engineers suggested a second subterranean dike upstream where the limestone ends, but the work was never funded. So it is not inconceivable that parts of the falls will someday succumb to the river. In fact, this happened as recently as 1987, when the river rushed into the sandstone beneath the hydroelectric plant at the lower dam, just downstream from the Stone Arch Bridge, and collapsed parts of its floor and roof. This time, engineers commanding a fleet of trucks plugged the forty-by-six-foot gap within a day. But heroes wearing pocket protectors notwithstanding, the river just keeps rolling along.