Blair Crossing Bridge

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Coordinates: 41 ° 33 '5 "  N , 96 ° 5' 44"  W.

Blair Crossing Bridge
Blair Crossing Bridge
The Blair Crossing Bridge during the 2011 Missouri Flood
use Railway bridge
Crossing of Missouri River
place Blair , Nebraska and
Harrison Counties , Iowa
Entertained by Union Pacific Railroad
construction Truss bridge
overall length 468 m
Longest span 102 m
Clear height 15 m ( MHW )
building-costs US $ 1.13 million (1883)
opening 1883, 1924
planner George S. Morison (SC&P, 1883)
OF Dalstrorn (C&NW, 1924)
location
Blair Crossing Bridge (USA)
Blair Crossing Bridge

The Blair Crossing Bridge , also Blair Railroad Bridge , is a single-track railroad bridge over the Missouri between the city of Blair , Nebraska and Harrison County , Iowa . It runs parallel to the road bridge on US Highway 30 and is just a few kilometers upstream from the Fort Calhoun nuclear power plant, which was shut down in 2016 . The bridge goes back to one of the first railway bridges over the river from 1883, the location of which required extensive hydraulic engineering measures to regulate the river . The truss bridge was built by the Sioux City and Pacific Railroad (SC&P), which later became part of the Chicago and North Western Railway (C&NW) rail network . Due to the rapid development of locomotives and freight volumes at the beginning of the 20th century, C&NW had to replace the superstructure in 1924 . The C&NW was merged with the Union Pacific Railroad in 1995 , which today uses the bridge as part of the Blair Subdivision on its east-west corridor.

First bridge in 1883

The Sioux City and Pacific Railroad (SC&P) was founded in 1864 as a connection from Sioux City to Fremont , where it was to provide a connection to the first transcontinental railroad between Sacramento and Omaha . The Missouri was crossed in Blair from 1870 by the Missouri Valley and Blair Railway and Bridge Company - a subsidiary of SC&P - cumbersome and time-consuming by means of rail ferries or, in winter, through temporary railroad tracks across the frozen river. To build a permanent bridge, representatives of SC&P and the president of the railway transfer company Marvin Hughitt contacted the bridge engineer George S. Morison at the end of 1881 . It would be the eleventh railroad bridge over the Missouri, and Morison's third across the river after the Plattsmouth Railroad Bridge (1880) and the Bismarck Bridge (1882).

River course

Course of the Missouri above Blair from 1880 (top left) to 1885 (bottom center)

The course of the Missouris was a particular challenge. Several kilometers upstream and downstream from Blair it was not naturally bounded by a high bank and migrating sandbanks gave the river a constantly new course after the spring floods. In order to be able to keep the course of the river below a bridge of manageable length in the long term when the water level is low, complex hydraulic engineering measures were necessary to regulate the river . From the summer of 1882, Morison had a dike built on the east side of the river on the future bridge , which should limit the Missouri to a width of around 500 meters even during floods, prevent the formation of side arms and close existing ones. In addition, the east and west banks and the adjacent river bed had, including the areas around the bridge piers, against flow-induced scouring be protected. To do this, huge mats made of tree trunks and branches were laid, which were weighted down with several thousand tons of stones. Morison had a total of over 150,000 tons of stone built, which had to be procured mainly from the quarries in Le Grand , 300 kilometers away ; the cost of river engineering amounted to rise to more than 400,000 US dollars , accounting for nearly 40 percent of the total.

Building

The first railway bridge in Blair in 1886, built by George S. Morison until 1883

At that time, Morison began to standardize his bridge construction projects, which made him more efficient and precise, and designed a high truss bridge with no movable bridge part , like the bridges in Plattsmouth and Bismarck . He chose three of his preferred parallel- belted Whipple trusses with an underlying track as central elements (English whipple truss , after its inventor Squire Whipple , 1804–1888). The girders, a little over 100 meters long, rested on four stone pillars, which were built using caissons down to the depth of the bedrock. Shorter truss girders with an overhead track 36 meters long on the east side and 54 meters on the west side followed the respective abutment . Morison was increasingly replacing the usual cast and wrought iron with the new material steel and was already using 37 percent of the three central trusses of the Blair Crossing Bridge . For the ascending approaches to the bridge, Morison had wooden trestle bridges several hundred meters long erected, which were later largely replaced by piles of earth; On the west side, before the gates of Blair, the small Fish Creek had to be crossed, over which girder bridges lead today. Work on the bridge piers began in October 1882 and was completed in May 1883. The trusses were set up from June and the first test train was able to pass the bridge at the end of October 1883.

Second bridge in 1924

New superstructure

The second superstructure of the railway bridge from 1924 behind the former road bridge, 1929–1991 (photo from 1987)
Girder bridge with solid wall girders on the west side (photo from 1987)

With the development of ever more powerful locomotives at the beginning of the 20th century, the weights of the railcars and the loads carried increased. As a result, the bridge reached its load limit in the early 1920s and the Chicago and North Western Railway (C&NW), as the operator at the time, was forced to provide the bridge with a new superstructure with a higher load-bearing capacity; the bridge piers were still in excellent condition and could be reused. The engineers at C&NW designed three new lattice girders made of steel in the Parker construction (named after the bridge construction engineer Charles H. Parker, 1842–1897) with a curved top flange in the shape of a polygon . These were designed for an axle load of 27 tons, which, according to the specifications at the time, corresponded to about two 190-ton locomotives. The subsequent shorter lattice girders were replaced by girder bridges with solid wall girders . The total weight of the superstructure was 2,300 tons, which is roughly double the mass of the first superstructure of 1,140 tons.

The manufacture and erection of the girders was carried out by the American Bridge Company ; to maintain the operation of the bridge, the exchanges took place one after the other. The renovation lasted from mid-October 1923 to mid-January 1924, with train traffic only having to be interrupted for a total of 17 hours. The old Whipple central trusses were in such good condition after 40 years of operation that some of them were used on smaller Wyoming branch lines for several years .

Takeover by the Union Pacific

The Chicago and North Western Railway (since the mid-1970s Chicago and North Western Transportation ) was taken over by the Union Pacific Railroad (UP ) in 1995 , which now operates the bridge as part of its east-west corridor from Chicago to the west coast of the United States . The traffic on the border between Iowa and Nebraska is divided equally between the Omaha subdivision to the east and the Blair subdivision to the west. About 60 trains a day ran over the latter in 2001, which among other things supply the Cargill plant in Blair; the coal transportation from the Powder River Basin in Wyoming and Montana runs the Union Pacific Missouri River Bridge on the Omaha Subdivision .

As part of the Lincoln Highway , the Abraham Lincoln Memorial Bridge was built about 60 meters downstream in a similar construction in 1929 , which was replaced by a new building in 1991 and which now leads to US Highway 30 .

2011 Missouri Flood

Railway and road bridge in June 2011
(view to the south, Morison's dike can be recognized by
the row of trees parallel to the driveway on the east side)
Satellite image of the Missouri near Blair from June 30, 2011 ( 하네 236342634643643.pngriver, F1 yellow flag.svgbridge, Redbox1.pngtracks)

From the 1880s onwards, the United States Army Corps of Engineers began to reinforce banks in densely populated areas along the Missouri, and over the years - as above Blair - the river was partially straightened . On the upper reaches of the Missouri, the Black Eagle Dam (1890) in Montana was built as the first barrage and, from the 1940s onwards, the Pick-Sloan Missouri Basin Program intensified river regulation and energy generation activities, which led to the construction of a large number of other dams . However, in the case of exceptionally strong spring floods, these cannot completely control the water masses and so there are occasionally major floods on the lower reaches of the Missouri, as a result of which many old tributaries carry water again; Since the 1940s, particularly severe flood disasters occurred on the Missouri in 1943, 1952, 1967, 1978, 1993 and 2011.

During the Missouri flood of 2011 , a record 42 km³ of water had to be drained above Sioux City to relieve the retention basin between May and July, which was almost three times the normal flow rate of around 16 km³ in this period and also in the area around Blair the Missouri made far over its banks. The railroad bridge and the adjacent road bridge on US Highway 30 in Blair were some of the few passable bridges between Sioux City and Omaha at the time . In order to maintain the supply of the Cargill biorefinery in Blair (Cargill Corn Milling North America biorefinery) and the removal of the processed products, the UP had to increase the tracks of more than 15 kilometers of the Blair subdivision by a few centimeters and in places by more than a meter ; the access roads to the road bridge in Blair were protected with temporary flood barriers made from sandbags and big bags .

Web links

Commons : Blair Railroad Bridge  - collection of pictures, videos and audio files

literature

Individual evidence

  1. ^ A b Clayton B. Fraser: Nebraska City Bridge. Historic American Engineering Record, HAER No. NE-2, Denver, Colorado 1986, pp. 99-115.
  2. ^ George S. Morison: The Blair Crossing Bridge: A Report to Marvin Hughitt, President of the Missouri Valley and Blair Railway and Bridge Company. New York 1886, plate 1, p. 27.
  3. ^ George S. Morison: The Blair Crossing Bridge: A Report to Marvin Hughitt, President of the Missouri Valley and Blair Railway and Bridge Company. New York 1886, pp. 2-4 and 8th.
  4. ^ A b George S. Morison: The Blair Crossing Bridge: A Report to Marvin Hughitt, President of the Missouri Valley and Blair Railway and Bridge Company. New York 1886, p. 6 f.
  5. ^ Glenn A. Knoblock: Historic Iron and Steel Bridges in Maine, New Hampshire and Vermont. McFarland, Jefferson 2012, ISBN 978-0-7864-4843-2 , p. 37.
  6. ↑ Lola Bennett: FROG BAYOU BRIDGE (Clear Creek Bridge). Historic American Engineering Record, HAER No. AR-65, Washington, DC 2007, p. 5.
  7. ↑ a b O. F. Dalstrorn: Missouri River Bridge at Blair, Neb., Rebuilt. In: Railway Age. Vol. 77, No. 21, 1924, pp. 931-934.
  8. ^ Lou Schmitz: The Blair Crossing. In: Chicago & North Western Historical Society Magazine. Fall 1997, pp. 39-45.
  9. ^ Union Pacific Railroad Crossing Study. Iowa Department of Transportation, December 2002, pp. 9-14, and 46 f. Retrieved May 19, 2018.
  10. ^ Clayton B. Fraser: Abraham Lincoln Memorial Bridge. Historic American Engineering Record, HAER No. NE-1, Denver, Colorado 1987.
  11. ^ National Research Council: The Missouri River Ecosystem: Exploring the Prospects for Recovery. The National Academies Press, Washington, DC 2002, p. 26 f.
  12. ^ Historic Floods on the Missouri River. United States Environmental Protection Agency (EPA), 2008. Retrieved May 21, 2018.
  13. ↑ Missouri River Mainstem Reservoir System: 2011 Flood Regulation. US Army Corps of Engineers, August 1, 2011, p. 16 and 18. Retrieved May 17, 2018.
  14. ^ Jeff Stagl: At Union Pacific, the floods of 2011 proved to be a watershed event of sorts. Rail News, Progressive Railroading, October 2011. Retrieved May 22, 2018.
  15. ↑ Flood Barrier Saves Highway. FEMA, Department of Homeland Security. Retrieved May 22, 2018.
  16. ↑ Katie Rohman: Remembering the flood. Washington County, Pilot-Tribune & Enterprise. Retrieved May 22, 2018.
This version was added to the list of articles worth reading on June 20, 2018 .