Figure - Lock & Dam 25

Lock & Dam 25

Operational on May 18, 1939 and located in Winfield Missouri, Lock and Dam 25 is the third southern-most dam in the system on the Upper Mississippi River.

The dam, which is 1,296 feet long, consists of 14 tainter gates and 3 roller gates. The tainter gates pivot vertically and are raised or lowered to control the depth of the water in the pool upstream of the dam. In times of high water, these gates are raised completely and the river flows almost unimpeded, allowing a more natural flow of the river. The roller gates, located near the center of the dam, also restrict the water flow, but in a manner meant to reduce erosion.

Vital Statistics

Location: Winfield, Mo.
Mississippi River Mile: 241.4
1st Day of Operation: May 18, 1939
Average lift: 15 feet
Pool size: 49,674 Acre Feet
Pool length: 27.8 miles
Lock characteristics:
Single Lock, 600 feet long, 110 feet wide
Dam Characteristics:
1,296 feet long, 14 Tainter Gates, 3 Roller Gates
Phone number: (636) 566-8120
Marine Radio: 12

Nine-Foot Navigation Channel

Located in Winfield, Missouri, Lock and Dam 25 is part of the Upper Mississippi River Nine Foot Navigation Project. The Project, authorized by the Rivers and Harbors Act of 1930, created and ensured a nine-foot deep navigation river channel.

On the Upper Mississippi, a total of 29 lock and dam systems were constructed, forming a stairway of water from Minnesota to Illinois. From the first lock and dam at Minneapolis-St. Paul, Minnesota to the last one at Granite City, Illinois, there is a drop in elevation of 420 feet. The locks are necessary at each of the dams to allow boats to navigate from one pool (the water backed up behind each dam) to the next. These dams were constructed to aid only navigation; they were not designed for flood control.

On the Lower Mississippi, the river does not need locks and dams because, with the addition of the Missouri, Illinois, Arkansas, Ohio, and other rivers, it is naturally wide enough and deep enough for navigation.

Figure - Nine-Foot Navigation Channel

Locking Process

The lock chamber consists of four miter gates (two at each end of the chamber), and four valves (two at each end). All boats wishing to pass through a dam must lock through the lock chamber, even during open river conditions.

Lockage is completed by using a system of valves to raise and lower the water level in the lock chamber. This is an elevator system for boats; raising or lowering the water adjusts the boats to the necessary pool level.

There are two sets of valves on the lock. The filling valves, located near the upper gate, are opened to allow water to enter the chamber, making it the same height as the upper pool. The emptying valves, located near the lower gate, are opened to allow water to drain out, making the chamber the same height as the lower pool. During the process, no pumps are used; the water is moved solely by gravity.

On the Upper Mississippi River, a full tow consists of a towboat and 15 barges, arranged 3 wide by 5 long. A full tow is around 1200 feet long, so at Lock 25 a double lockage must be performed. The first three rows of the tow’s barges would be untied and locked through separately, using a tow haulage (cable and hoist system). Then, the remaining barges and the towboat would lock through and afterwards the barges would all be ratcheted back together. This process typically occupies up to two hours, which is why the U.S. Army Corps of Engineers is considering the addition of a 1200 foot lock chamber that would eliminate the need for a double lockage.

Figure - Annual Tonnage

Annual Tonnage

Year Tonnage Lockages
2009
26,926,504
4,545
2008
23,244,934
3,929
2007
30,204,744
5,314
2006
31,026,288
4,971
2005
29,043,655
4,886
2004
27,894,562
4,795
2003
33,749,527
5,614
2002
38,916,145
6,601
2001
34,858,294
6,008
2000
39,177,450
6,623
1999
39,536,830
6,777
1998
34,819,845
6,110
1997
33,638,634
6,132
1996
36,088,709
6,652
1995
37,432,909
6,654
1994
30,758,651
5,658
1993
26,560,658
4,687
1992
39,378,151
7,282
1991
37,758,657
7,394
1990
42,339,143
7,923
1989
36,218,686
7,118
1988
37,875,033
7,326
1987
35,319,224
6,720
1986
28,159,960
5,681
1985
26,109,104
5,389
1984
36,167,255
7,027
1983
37,439,016
7,319
1982
32,767,055
6,586
1981 34,309,187 7,067
1980 32,519,470 6,770
1979 28,638,386 Na
1978 29,041,957 6,100
1977 25,093,200 5,671
1976 24,781,578 5,708
1975 23,712,446 5,336
1974 24,292,547 5,374
1973 22,706,350 5,085
1972 24,611,927 5,785
1971 21,430,888 5,580
1970 22,175,609 5,327
1969 18,622,522 4,715
1968 16,547,642 5,146
1967 16,355,932 4,906
1966 15,857,490 4,803
1965 13,425,723 4,287
1964 13,408,798 4,664
1963 12,599,623 4,345
1962 10,814,046 4,023
1961 9,762,001 3,866
1960 9,686,116 3,737
1959 9,154,872 3,834
1958 8,464,618 3,646
1957 7,460,929 3,383
1956 6,792,648 2,884
1955 6,530,038 2,974
1954 5,675,246 2,914
1953 5,072,640 2,870
1952 4,044,774 2,276
1951 4,225,148 2,187
1950 4,323,837 2,571
1949 3,654,954 2,634
1948 3,252,308 2,341
1947 3,120,342 2,068
1946 2,989,198 2,570
1945 2,033,557 1,695
1944 1,875,881 1,624
1943 1,608,788 1,687
1942 1,987,289 2,447
1941 1,974,121 2,189
1940 1,570,167 2,188
1939 1,122,824 1,645