A major rehabilitation of the 50 year-old lock and dam was completed in the spring of 1994. The work included construction of new central control station, installation of a new operating machinery, concrete repair, permanent wiring, new utilities, and lighting. A platform has been built overlooking the lock for better handicap access. This modernization is expected to greatly increase the reliability of this heavily used lock and add at least another 50 years to its serviceability. Rehabilitation project completed in 1994 Lock and Dam No. 4 is located in Alma, Wisconsin at the river mile 752.8.
Commodities carried by the barges include grain, coal, fertilizer, and petroleum products.
An average of 175 million tons of freight moves on the Upper Mississippi each year. One barge will hold an average of 1500 tons, which equals the tonnage of 15 railroad cars or 58 semi trucks. The lock is 600 feet long by 110 feet wide and raises and lowers traffic 7 feet. The dam is 6,867 feet long, including 1,367 feet of moveable gate sections and 5,500 feet of earth fill dike. The moveable gate section consists of six roller gates and 22 Tainted gates.