Locks and Dams 3 through 10 have auxiliary chambers. Each auxiliary chamber has only a single set of miter gates that could pass shallow draft navigation traffic if the lock chamber was out of operation and the upstream and downstream pools were equalized. Thus, the auxiliary chamber’s miter gates are considered emergency gates.
At each site, the U.S. Army Corps of Engineers only installed one set of miter gates. An auxiliary lock chamber was never authorized by Congress, which would have included a second set of miter gates. Since installation, the auxiliary emergency gates have never been used, and the gate operating machinery was never installed.
The Corps performs periodic inspections of all of its sites. Recent periodic inspection reports for these sites have raised concerns about the condition of the auxiliary miter gates because they constitute a non-redundant portion of the damming surface that cannot be properly inspected and maintained. Deterioration and failure of the auxiliary miter gates could result in a loss of pool and disrupt navigation on the Upper Mississippi River.
At each site, the Corps plans to install a double-walled sheet pile structure upstream of the auxiliary gates. The auxiliary gates will remain in place. The sheet pile structure will act as a redundant damming service and a walkway. If removed, the structure would not interfere with the function of the auxiliary gates.
Construction contracts for the sheet pile for Locks and Dams 5 and 5A were awarded in 2018. The Corps completed the designs for Locks and Dams 3, 4, 6, 8, 9 and 10 in fiscal year 2019. Construction contracts will be awarded based on the availability of funding.
Congress authorized the Upper Mississippi River 9-Foot Channel Navigation Project as part of the Rivers and Harbors Act, approved July 3, 1930.
Design and construction of the sheet pile at the auxiliary locks are completed with 100 percent federal funds. In fiscal year 2018, construction contracts at Locks and Dams 5 and 5A were awarded for $2,272,000 and $2,950,000, respectively, and a design task order for Locks and Dams 3, 4, 6 and 8 was awarded for $432,000.