Dam is 365' long with 4 roller gates. More than 2,000 feet of earth embankment with a series of upstream spot dikes completes the structure to create Pool 3.
Constructed and placed in operation July 1938. Site underwent major rehabilitation from 1988 through 1991.
The structure is somewhat unique in that the dam itself is not very long, while the river itself is rather wide. The bulk of the structure consists of earth embankments and dikes. The main dam structure consists of 4 roller gates. The lock structure is the standard size for the upper Mississippi of 110 feet wide by 600 feet long. [JohnWeeks]
The lift is 8'.
The highlighted curve in the bank upstream of the lock created an outdraft current that shoved downbound tows away from the lock and towards the gated structure. This has caused many accidents, including 11 incidents since 1968 when tows collided with the gated part of the dam. "Navigation accidents can render the four roller gates inoperable, resulting in overtopping and erosion of the embakments. Failure of the embankment system could result in an accidental drawdown of Pool 3 with significant economic and environmental consequences. [USACE-history]
|Google Earth, Sep 2009|
Using 2009 Tiger funds, an 862' guide wall extension was completed in Apr 2011.
|Google Earth, Aug 2011|
And a closure dike was completed in Oct 2011. Other improvements such as dredging the channel, improving embankments with sheet pile and riprap, and restoring 313 acres of floodplain were also done.
|Google Earth, Sep 2012|
The estimate for this 21st Century work was $70m. Until this work was done, USACE rated this structure as the second most likely Corps structure to fail. If it did fail, navigation above Red Wing, MN, would not be possible and the Prairie Island Nuclear Generating Plant would have to be shut down because its water intakes would be above the water level of a drained pool #3. That plant supplies half of the electricity to the twin cities area. [JohnWeeks]
The post that motivated researching this dam.
|Brian Klawitter commented on a post|
L&D 3 in 1999....seems like they're thinning out a bit.
[Judging from the context, they are dealing with dead mayflies. This gives us a unique perspective of roller gates that are all the way up.]