Saint-Anthony-Fälle

One of the dams making up St. Anthony Falls, photographed from downstream in October, 2005. One of the locks can be seen on the left.

Saint Anthony Falls, or the Falls of Saint Anthony, located near downtown Minneapolis, Minnesota, was the only waterfall on the Upper Mississippi River until it was replaced by a concrete apron after they partially collapsed in 1869 and, later, a series of dams in the 1950s and 1960s. The indigenous people who lived in their vicinity called the falls by various names. The Ojibwe term was Kakabikah (Gakaabikaa, "waterfall over a cliff") and the Dakota used Minirara (curling water) and Owahmenah (falling water).[1] In 1680, the falls became known to the rest of the world when they were observed by Father Louis Hennepin, a Catholic friar of Belgian birth,[2] who also brought the existence of Niagara Falls to the world's attention. Hennepin named Saint Anthony Falls after his patron saint, Anthony of Padua.[3] Later explorers include Jonathan Carver and Zebulon Montgomery Pike. The region around the falls was added to the National Register of Historic Places as the Saint Anthony Falls Historic District in 1971.

Geology

Plaque describing portaging

Geologists say that the falls first appeared roughly 10,000 years ago several miles downstream near the confluence of the Minnesota River, around modern-day Saint Paul.[4] Estimates are that the falls were about 180 feet high at that time. The massive River Warren, a precursor of today's Minnesota River, had a waterfall that is said to have been twice as wide as Niagara Falls. Over the millennia, the falls moved upstream, breaking off into several smaller waterfalls as tributaries were reached. Minnehaha Falls in south Minneapolis is one of several such examples.

From its origins near Fort Snelling, St. Anthony Falls relocated upstream at a rate of about 4 feet per year until it reached its present location in the early 1800s. When Father Louis Hennepin documented the falls he estimated the falls' height to be 50 or 60 feet. Later explorers described it as being in the range of 16 to 20 feet high.[5]

A diagram showing the recession of the falls between 1680 and 1887.

As Minneapolis (and its former neighbor across the river, St. Anthony) developed, the water power at the falls became a source of power for several industries. Water power was used by sawmills, textile mills, and flour mills (for instance, the Pillsbury "A" Mill). Millers on the Minneapolis side extracted power by diverting upper-level water into waterwheel-equipped vertical shafts (driven through the limestone bedrock into the soft, underlying sandstone) and then through horizontal tunnels to the falls' lower level. These shafts and tunnels weakened the limestone and its sandstone foundation, accelerating the falls' upriver erosion to 26 feet per year between 1857 and 1868. The falls quickly approached the edge of their limestone cap; once the limestone had completely eroded away, the falls would degenerate into sandstone rapids unsuitable for waterpower.

The falls in the early 1900s

The geological formation of the area consisted of a hard, thin layer of limestone overlaying a soft sandstone formation. The water churning at the bottom of the falls ate away at the sandstone, and after enough support had been removed, large blocks of the limestone would fall off. This process had been happening naturally over the past eight thousand years, with the falls having receded up from the Fort Snelling area to their location in the 1850s. The early dams built to harness the waterpower exposed the limestone to freezing and thawing forces, narrowed the channel, and increased the damage from floods. A report in 1868 found that only eleven hundred feet of the limestone remained upstream, and if it was eroded away, the falls would turn into a rapids that would no longer be useful for waterpower. Meanwhile, the St. Anthony Falls Water Power Company approved a plan for the firm of William W. Eastman and John L. Merriam to build a tunnel under Hennepin and Nicollet Islands that would share the waterpower. This plan was met with disaster on October 4, 1869, when the limestone cap was breached. The leak turned into a torrent of water coming out the tunnel. The water blasted Hennepin Island, causing a 150-foot chunk to fall off into the river. Believing that the mills and all the other industries around the falls would be ruined, hundreds of people rushed to view the impending disaster. Groups of volunteers started shoring up the gap by throwing trees and timber into the river, but that was ineffective. They then built a huge raft of timbers from the milling operations on Nicollet Island. This worked briefly, but also proved ineffective. A number of workers worked for months to build a dam that would funnel water away from the tunnel. The next year, an engineer from Lowell, Massachusetts recommended completing a wooden apron, sealing the tunnel, and building low dams above the falls to avoid exposing the limestone to the weather. This work was assisted by the federal government, and was eventually completed in 1884. The federal government spent $615,000 on this effort, while the two cities spent $334,500.

Sandstone layered under limestone

St. Anthony Falls was the upper limit of commercial navigation on the Mississippi until two dams and a series of locks were built between 1948 and 1963 by the United States Army Corps of Engineers. The locks make commercial navigation possible above Minneapolis but, since the locks in Minneapolis are smaller than most of the locks on the river, the practical limit for many commercial tows is farther downriver. Few barges go past St. Paul.

Locks and dams

The concrete apron over St. Anthony Falls

Completed in 1963, the upper St. Anthony Falls dam is a horseshoe-shaped hydro-electric dam 93 feet (28 m) in height. The upper pool has a normal capacity of 3,150 acre feet (3,885,000 m³) and a normal level of 799 feet (244 m) above sea level. The navigation channel required alteration of the historic Stone Arch Bridge, which now has a metal truss section to allow ships to pass below.

Completed in 1956, the lower St. Anthony Falls dam is a gravity-type hydro-electric dam 60 feet (18 m) in height, consisting of a 275 foot (84 m) long concrete spillway with 4 tainter gates. The lower pool (sometimes called the intermediate pool) has a normal capacity of 375 acre-feet (463,000 m³) and a normal level of 750 feet (229 m) above sea level.

The concrete apron over St. Anthony Falls

The pool below the lower dam has a normal level of 725 feet (221 m) above sea level.

The upper and lower locks are each 56 feet (17 m) wide by 400 feet (122 m) long.

Even though the falls often don't look very dangerous, the current is swift and people sometimes find themselves very bad situations in the area. In 1991, a small boat drifted too close and fell over one part of the dam. Two people onboard were killed, and two others had to be rescued by helicopter. Rescues at the site are usually much less dramatic, but continue to happen occasionally.

Jesse Ventura's brother Jan Janos has been a dam operator at the site for many years.

See also

• Hennepin Island Hydroelectric Plant
• Northwestern Consolidated Milling Company Elevator A
• Saint Anthony Main - adjacent shopping area.

External links

• U.S. Army Corps of Engineers St. Paul District: Upper St. Anthony Falls
• U.S. Army Corps of Engineers St. Paul District: Lower St. Anthony Falls
• Engineering the Falls: The Corps Role at St. Anthony Falls - an article on the U.S. Army Corps of Engineers website covering the history and geology of St. Anthony Falls.
• [6] The city's official promotional site for the riverfront district.