Mississippi River: Lock and Dam 6 Winter Maintenance; Alma, Wisconsin

U.S. Corps of Engineers, St. Paul District
Published Sept. 27, 2021
Updated: March 29, 2022

Purpose of this project is to assure proper periodic maintenance and subsequent operation of the Lock and Dam systems.


Lock and Dam 6 is located near the community of Trempealeau, Wisconsin. The Corps of Engineers completed the facility in 1936 as part of the overall 9-foot channel project.


Lock and Dam 6 was originally dewatered in 1977, 17 years later in 1994, and subsequently in fiscal year 2013. The St. Paul District locks are now dewatered on an approximate 20-year cycle. 

On average, more than 10 million tons of cargo and 4,300 recreational craft pass through the lock annually. The difference between upper and lower pools during normal conditions is 6 feet.

The lock consists of the upper miter gates, which are 23 feet high, and the lower miter gates, which are 25 feet high.

Other districts have had issues with greaseless pintels and bushings. The main focus is to replace them with greades pintels and bushings while checking for degradation in the spring. The other focus is on repairs from tow damage on the upper miter gates.

All construction is completed by the Corps’ maintenance and repair crew. First they place bulkheads upstream and downstream of the chamber temporarily dam the water. Once the water is pumped from the chamber, the miter gates and parts are inspected.

The work is performed during the winter traffic closure period to avoid impacts to users of the navigation system. The project has a very tight schedule as the work has to be completed by the opening of navigation season.


Maintenance started in early December 2022 when the lock closes navigation for the winter. The project will be completed by March 2023 when the lock is open to navigation.


The project was authorized as part of the Rivers and Harbors Act approved July 3, 1930.


Project design and construction costs are 100% federal.

Estimated Total Cost                                   $3,000,000