Saint Anthony Falls
The Saint Anthony Falls ( Falls of Saint Anthony in English ) are located near the center of Minneapolis in the U.S. state of Minnesota. They were to the construction of a weir made of concrete, which had been built after the partial collapse of the cases in 1869, in addition to the smaller waterfalls in Little Falls / Minnesota, the only waterfalls on the upper reaches of the Mississippi River. Later, during the 1950s and 1960s a series of dams was built to allow navigation in the section above the falls. The people living in the neighborhood of the cases indigenous peoples knew various names. The Anishinabe called Kakabikah ( Gakaabikaa, " waterfall over a cliff ")., The Dakota used the terms Minirara ( " to curling water") and Owahmenah ( " falling water "). The cases were the rest of the world first came to prominence in 1680, when the Belgian missionary Louis Hennepin Catholic reported it. This had brought the news of the existence of Niagara Falls to the world. Hennepin named the falls after Saint Anthony of Padua. Later researchers who visited and described the falls, for example, were Zebulon Montgomery Pike and Jonathan Carver. The waterfalls and its surroundings were added to the National Register of Historic Places in 1971 as the Saint Anthony Falls Historic District.
Geology
According to geologists the waterfalls a few miles Snelling emerged around 10,000 years ago downriver at the confluence of the glacial River Warren at today's Fort. According to estimates, the cases were about 60 feet high, as the former falls back wandered over the confluence of the Mississippi River with the River Warren. During the subsequent 10,000 years, the waterfalls moved by headward erosion of the limestone layer upstream until that arrived at the point where they are today. Tributaries such as the Minnehaha Creek formed their own waterfalls, as to nick the valley of the Mississippi River in the surrounding countryside.
From its original location at Fort Snelling, the Saint Anthony Falls migrated with a velocity of about 120 cm annually upriver and reached its present position at the beginning of the 19th century. By Louis Hennepin, the height of the falls was estimated at 15 to 18 meters; subsequent explorers described their height in a range of five to seven meters high. However, the difference may originate from different view points. The slope in the range is about the series of various dams across 23 meters in total.
The geological formation of the area consists of a hard, thin layer of limestone overlying a soft layer of sandstone. This layering is the result of Ordovician lake, which had covered the Middle East Minnesota million about 500 years ago. The bubbling water at the foot of the waterfall has gnawed the sandstone and after sufficient ground had disappeared in this way, fell off large fragments of the outer layer. This process takes place in a natural way since about 9800 years.
Industry
The first private land claims in the cases were found in 1838 by Franklin Steele, although this only in 1847 put forward the necessary funds of $ 12,000 for a 90 - percent stake in the ground. On May 18, 1848, U.S. President James Polk approved the statements made to Saint Anthony claims. Steele was now able to build his dam on the east side of the river above the falls by cordoned off the eastern arm. The dam stood out with a length of about 230 meters diagonally into the river and was just under five feet tall and firmly attached to the river bed. However, the thickness reached at the base of about 12 feet, at the crown only about three and a half meters. Steele sent in December 1847 Lumberjack teams at the Crow Wing River to supply its sawmill with pine wood. On September 1, 1848 his sawmill began at two vertical saws to work. He could be ready to sell wood cut and supplied construction projects in the emerging city with wood. The new settlement at the falls attracted entrepreneurs from New England, one of which brought many experiences with the timber industry and the mill being. Steele committed Ard Godfrey to build the first saw mill at the waterfalls and to lead. Godfrey knew how to most effectively exploited the natural resources, especially the waterfalls and the vast pine forests to produce wood products. Godfrey built the first house in St. Anthony. Steele had done land registration for the city in 1849, the city's founding itself was carried out in 1855.
Until 1854 300 squatters had the west bank of the river occupied and 1855 saw the Congress the right to purchase the land to which they had claimed. The western shore quickly developed into a center of new mills and consortia. This built a running diagonally to the north embankment into the river, created together with the dam Steeles the inverted V - pattern that can still be seen today. Steele founded in 1856, the St. Anthony Falls Water Power Company, along with three partners from New York City. The company struggled for several years to survive, partly because of poor relations between the financiers, partly because of an economic crisis and because of the American Civil War. In 1868 the company was restructured, now. Involving John Pillsbury, Richard and Samuel Chute, Sumner Farnham and Frederick Butterfield
As Minneapolis and his former neighbor, St. Anthony, developed the water power of the Falls was a source of energy for various industries. Water power was used by lumber mills, spinning mills and flour mills. The mill operator on the shore side of Minneapolis formed a consortium to win hydropower by discharge of river water in equipped with water wheels vertical shafts. These were driven by the hard limestone in the soft underlying sandstone and led the water through a horizontal tunnel to the river below the falls again. Through these shafts and tunnels the limestone ceiling and sandstone subsoil were weakened, thus accelerating the headward erosion 1857-1868 annually to eight meters. It threatened so that the falls quickly reached the edge of the limestone ceiling; once the limestone would have been completely eroded away once, the cases would turn into rapids that were unsuitable for the use of water power. The mills on the side of St. Anthony were less well organized and that is why the industry developed on the eastern side of the river at a slower pace.
Collapse of the Hennepin Iceland tunnel of 1869
The first dams were built to tame the water power, put the limestone the forces of nature by freezing and thawing out, narrowed the river and thus increased the damage caused by floods. A report in 1868 showed that a distance of only about 3350 meters remained before the limestone would be completely eroded away. Then the cases would turn into rapids. Meanwhile, the St. Anthony Falls Water Power Company had approved a plan of the company by William W. Eastman and John L. Merriam to build a tunnel under the Hennepin and Nicolletinseln, which allowed the sharing of water. The realization of this plan led on 5 October 1869 an accident, as the limestone ceiling collapsed. The leak turns into a raging stream of water came out of the tunnel and directly met Hennepin Iceland, where by an approximately 50 -meter length of the island has been broken. In the belief that the mills and the other companies would be ruined by the cases around, hundreds of people flocked to witness the accident. Groups of volunteers began to build the hole a weir by threw them in trees and wood, but these attempts were ineffective. Then they built a large raft out of the woods, which were stored at sawmill on Nicollet Iceland. This worked for a short time, but ultimately missed its purpose well. Numerous workers built over months a dam should drain the water from the hole. The following year, recommended an engineer from Lowell, Massachusetts to build a wooden weir, would fill the tunnel and low dams to build the waterfalls around, so that the limestone would not be further exposed to the weather. This work was supported by the Federal Government, and finally completed in 1884. $ 615,000 from federal funds were spent for this purpose, the two cities gave $ 334,500.
Locks and Dams
The St. Anthony Falls formed the upper end of the farmed navigation on the Mississippi River until 1948-1963 by the United States Army Corps of Engineers two dams and a series of locks were built. The locks made the navigation above Minneapolis possible, but due to the smaller size of these locks in comparison to other Mississippi locks, the practical Schiffbarkeitsgrenze downstream. Few ships ply St. Paul out to the north.
In 1963, the upper dam was completed. There is a horseshoe-shaped dam that serves the hydropower plant and is 28 m high. The upper pool has a normal capacity of 3.885 million cubic meters and a normal level of 244 m above sea level. The ship channel required a change in the historic Stone Arch Bridge, which now has a metal support section that allows the ships to pass underneath.
In 1956, the lower dam had been completed, which is 18 m high and consists of a 84 m long concrete spillway with four flood gates. The lower tank, sometimes referred to as an intermediate tank, has a capacity of 463,000 m³, and is located 229 m above the sea level.
The basin below the lower dam is located in a normal height of 221 m above sea level. The upper and lower lock chambers are each 17 m wide and 122 m long.
Although the cases usually do not look very dangerous, the current is strong. Again and again people in threatening situations. In 1991, about a small boat was herangedriftet too close and slipped over a portion of the dam. Two passengers were killed and two others had to be rescued by a helicopter. Most rescues on the site are less dramatic, but for this to happen fairly regularly.