Icy work underway to repair lock
The U.S. Army Corps of Engineers (USACE) is doing some important maintenance at Lock and Dam 7 outside of La Crescent in preparation for new gates to be installed next summer. Project Manager Jim Cook said the maintenance project is important to keep the lock operating efficiently for commercial and recreational traffic on the Mississippi River.
USACE’s St. Paul District operates and maintains 13 locks and dams on the Upper Mississippi from Upper St. Anthony Falls in downtown Minneapolis to Guttenberg, Iowa. The construction of the locks and dams was authorized in 1930 with the goal of splitting the river into a series of navigation pools deep enough to support barges. The USACE ensures the pools are a minimum depth of nine feet through its locks and dams and river dredging efforts during the summer. The lock chambers allow everything from large river craft like barges to small fishing boats to move between pools with differing elevations. This winter, USACE worked on maintenance projects at locks and dams 7 and 9 to replace lock gate anchorages, as well as guidewall repairs at Lock and Dam 2, and gate maintenance at lock and dams 5 and 5A near Winona.
The U.S. Army Corps of Engineers work to install new anchorages in preparation for new lock gates to be installed next summer at Lock at Dam 7.
At Lock and Dam 7, USACE began a $1.5 million maintenance project to make concrete repairs and install new anchorages in December and expects to complete the project by the end of February. The anchorages are essentially the hinges on which the lock gates, or miter gates, rest, Cook said. The gates allow vessels to enter and leave the lock chamber, where the water level is adjusted to match the neighboring pool. Cook said the USACE won’t replace the entirety of the anchorages, which are huge steel structures that extend tens of feet into the ground and wall, but instead the components that connect the deeply anchored part to the gate. “You can think of it as the door hinge panel piece, but not the wall which actually carries the weight,” Cook said.
“We do this work during the winter because it takes the lock out of service, because you can't use the gates while you're upgrading the hinges, essentially,” Cook said. “So we have to do it during the winter so as not to disrupt all the commerce and all the recreation traffic on the river. But of course, that puts the guys doing the work in less favorable conditions.” He added, “It's difficult, dangerous work, so these guys are professionals. We're lucky to have them. There's an instance when we put divers in the water in the middle of winter to get this work done.”
This maintenance work to replace the anchorages is in preparation for installing new miter gates at Lock and Dam 7 next summer, according to Cook. “The existing miter gates have been in position since 1937, and so the structures are nearing the end of their design life,” Cook said. While the new gates will be roughly the same size, they will be thicker and weigh roughly 50% more.
Operations Safety Manager Aaron Pieplow said replacing the miter gates will disrupt river traffic for four 12-hour periods, and that they will focus the work on Tuesdays and Thursdays when river traffic is lower. “So on Tuesday morning at 6, we're shutting down the lock, then by like 6 at night, it’s usually back and operational,” Pieplow said.
Last year, 4,360 barges carrying around 8.7 million tons of commodities passed through Lock and Dam 7. In that same year, 2,462 recreation vessels also passed through the lock.
