Lock and Dam 17, in New Boston, Illinois, closed this winter to undergo a dewatering as part of several maintenance projects performed at District locks from December to March.
Brad Heuzenga, maintenance section project engineer, said, "We only get to do a dewatering maybe every 40 years or so, and it exposes a lot of the problems that we don’t ordinarily get to look at when there is water in the chamber."
The dewatering project allowed District engineers to inspect and repair portions of the lock that otherwise couldn’t be done with water in the chamber, explained Aaron Dunlop, Mississippi River operations manager. The project also tested the ability of the lock to be dewatered quickly and reliably in the future.
All of the projects slated for the lock were purposely scheduled during the winter months, so as not to disrupt the heavy flow of summer river traffic.
In addition to regular maintenance of the lock chamber, crews also completed the installation of the lower bulkhead slots, which included the placement of a sill beam.
"There is also work going on at the lower end, installing sill beams, which you wouldn’t be able to do if the water was in the chamber," Heuzenga said in February.
The sill beam provides a base against which the chamber bulkheads will sit on and seal against. This beam is lowered into the water prior to the dewatering and secured by divers. Once the lock chamber is dewatered, the beam is
tied to the chamber floor with reinforced concrete.
The bubbler system, which prevents ice formation in and around the miter gates, was also repaired as part of the maintenance project.
Structures Maintenance Supervisor, Justin Carter, said, "The old concrete is just bad and really deteriorating, so we had to come in and pour new concrete and hopefully that will ensure a longer life out of the lock."
Old, degraded concrete was removed from the lock using the hydro-demolition machine, which uses high-pressure water to blast away at the concrete, and new concrete was poured in its place.
Also new to this dewatering was the replacement of the upper embedded miter gate anchorages. The recently replaced miter gates now hang from heavy-duty anchorages.
"It’s important to dewater them [the lock chambers]. It gives us the chance to do a lot of the work and it gives our engineers the opportunity to come in and see some of the possible problems so we can schedule more maintenance in the future," Heuzenga said.