Hennepin Island Tunnel

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Collapse of the Hennepin Island Tunnel at the Saint Anthony Falls in 1869 .

The Hennepin Island Tunnel was a 2,500-foot (approximately 760 m) long tunnel in Saint Anthony (now part of Minneapolis ) that was dug under the Mississippi River between 1868 and 1869 to create a hydropower drainage channel for sawing and cutting To create flour mills that were located above the Saint Anthony Falls . The tunnel ran from Nicollet Island downstream under Hennepin Island and had its exit below the falls.

While the tunnel was being built, on October 5, 1869, the river broke through the thin limestone blanket that separated the river bed from the tunnel. The river washed through the tunnel, eroding parts of Hennepin Island and causing the collapse of the supporting soil on the upstream side of the falls. There were serious fears that the river bed would crumble and turn the Saint Anthony Falls into a long series of rapids . Within a few weeks, dams were built to hold back the flow and stop the falls from washing away. The measure was only temporary, however, because the spring floods of 1870 damaged some of the new dams and washed away even larger parts of Hennepin Island. By autumn 1870, the river bed and banks were further stabilized and a wooden weir was built above the falls. As a direct result of the collapse, the Saint Anthony Falls eventually received the concrete weir that created an artificial waterfall, the only larger waterfall on the Mississippi River.

The former tunnel is located approximately 1,650 meters upstream of the Interstate 35W Mississippi River Bridge, which collapsed in 2007 .

history

Hennepin Island was named after the discoverer , Catholic priest and Franciscan Louis Hennepin (* May 12, 1626 ; † around 1705 ). The entrepreneurs William W. Eastman and John L. Merriam bought the neighboring island, Nicollet Island, in 1865 because they had the idea of ​​digging a tunnel from Nicollet Island under the Saint Anthony Falls to make a profit To provide a mill canal to flour mills and sawmills that were located above the waterfalls. The tunnel was to become part of a system of hydraulic engineering for the benefit of the industries on which Minneapolis's growth depended. The project was intended to enable further industrial companies to settle on Nicollet Island through hydropower.

The Saint Anthony Falls are made up of a hard limestone cap that sits on top of soft sandstone . 10,000 years ago the falls were where Fort Snelling is today, at the confluence with the glacial River Warren . During the following millennia, the river eroded the sandstone , undermining the limestone on it, causing the falls to slowly migrate upstream until they reached their current location.

Workers began in 1868 to dig a 2,500-foot tunnel under the river bed that ran from Nicollet Island downriver under Hennepin Island and would reappear beneath the falls. For a year the workers dug their way through the soft sandstone that lies beneath the thin limestone layer that forms the river bed. Then, in October 1869, water began to seep into the tunnel from above.

Photo taken shortly after the tunnel collapsed. A group of men sort logs on Nicollet Island . A barge can be seen in the foreground and the houses of Saint Anthony in the background.

On October 5, 1869, the river broke through the thin limestone layer. The rushing current washed through the tunnel, causing parts of Hennepin Island to give way and causing the earth that bedded the Saint Anthony Falls to collapse. There were immediate fears that the river bed would crumble, turning the falls into a long series of rapids. A contemporary witness remembers

“Shop owners rushed to the falls, taking their vendors with them; the bakers left their ovens, the woodworkers were sent from the mills, the hairdressers left their customers unshaven; Craftsmen dropped their tools; the lawyers closed their books and stopped submitting petitions to the court; the doctors left their offices. Hundreds of people could be seen hurrying on their way to the falls in the streets. "

Immediately, work began to plug the tunnel and hundreds of volunteers used wood and stones. The river washed them away without any problems. After a few weeks the situation improved and dams were built to divert the river and prevent the waterfalls from washing away. The repair was temporary as the spring floods of 1870 tore open some of the new dams and washed more soil away from Hennepin Island. The soil also collapsed beneath the Summit flour mill, Moulton's mechanical planer, and a grain house, and those buildings fell into the river.

By the autumn of 1870, however, the river bed and the banks were stabilized and a wooden weir protected the battered Saint Anthony Falls from further receding erosion . The weir covered the rugged rocks of the falls and tamed the prancing water.

consequences

The widespread damage caused by the break-in of the Hennepin Island Tunnel resulted in litigation and calls for political change. A key question at the time was whether the local taxpayer had to pay for repairs that only benefited the entrepreneurs on the riverbank. The collapse of the tunnel was ultimately one of the factors that led to the merger of St. Anthony and Minneapolis in 1872. To make it easier for the local population, the United States Army Corps of Engineers carried out the repair work on the assumption that this would ensure navigability on the river and used federal funds to do so. Seven years after the tunnel collapse, in 1876, the falls were secured with an underground dam and other low dams that still exist today above the Stone Arch Bridge . Until 1880, the Army Corps of Engineers had built in a concrete weir and thus created today's artificial waterfalls. The federal government spent $ 615,000 on the effort, with the cities of St. Anthony and Minneapolis paying $ 334,500 of the cost.

See also

Individual evidence

  1. ↑ a b c d Parker, Dick. (October 30, 2006) Star Tribune Retro: Saving St. Anthony Falls in 1869. Mississippi gorge almost eats Minneapolis' heart. Section news; page 3B.
  2. ↑ Falls of St. Anthony . In: A History of Minneapolis . Minnesota Public Library. Archived from the original on August 15, 2007. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved August 2, 2007. @1@ 2Template: Webachiv / IABot / www.mpls.lib.mn.us
  3. ↑ Engineering the Falls: The Corps Role at St. Anthony Falls ( Memento of the original from May 3, 2007 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. - an article on the US Army Corps of Engineers website covering the history and geology of St. Anthony Falls. @1@ 2Template: Webachiv / IABot / www.mvp.usace.army.mil
  4. ^ Minneapolis' official promotional site for the riverfront district
  5. ↑ a b c d e f g McAuliffe, Bill. (September 29, 1997) Star Tribune Time capsule: "The falls are going out!" Section news; page 1B.
  6. ↑ a b c d e f g h i Benidt, Bruce. (November 15, 1987) Star Tribune River has powerful history of damage at falls. Section: news; Page 7B.
  7. ↑ Shannon M. Pennefeather (Ed.): Mill City. A Visual History of the Minneapolis Mill District. Minnesota Historical Society Press, St. Paul MN 2003, ISBN 0-87351-446-7 .

literature

  • Lucile M. Kane: The waterfall that built a city. The Falls of St. Anthony in Minneapolis. Minnesota Historical Society, St. Paul MN 1966.

Coordinates: 44 ° 58 ′ 57 ″  N , 93 ° 15 ′ 22 ″  W.