Nashville District Divers and the Maintenance Support Team work together to replace 18-ton debris screens at Wilson Lock

FLORENCE, AL, UNITED STATES

08.12.2020

Story by Daniel Barrios 

U.S. Army Corps of Engineers, Nashville District

FLORENCE, Ala. (Aug 12, 2020) – A stoic, bearded man with tree trunk arms breathed steadily as he calmed his mind for the dangerous task to come. His eyes stared straight ahead with confidence as his diver helper strapped on the reserve SCUBA tank, then mounted a heavy metal dive helmet onto his water-tight neck collar. Like a knight being armored by a squire, Matt Chambers who is a lock and dam mechanic and diver was preparing for battle. Only this battle was going to be seventy feet underwater, and it was time to go to work.
In the blazing August heat, the U.S. Army Corps of Engineers Nashville District Dive Team and the Maintenance Support Team worked together to start the process of removal and replacement of multiple debris screens from Wilson Lock, one of the largest projects within the Nashville District’s area of responsibility.
The trash screens are an important component at the lock because they prevent trash, trees and debris from entering the culvert and damaging the valve components. These heavy duty screens are from the original construction of Wilson Lock and have been in the water for over five decades and are due for replacement. Each screen weighs 18,000 pounds and takes careful teamwork to remove.
Mason Carter, the Maintenance Service Team coordinator with the Operations Division, Nashville District said: “The goal of the MST is to support the 14 locks we have within the District. It requires an extreme amount of coordination with the lock staff, mechanics, dive team, as well as operations managers both on the Tennessee River and the Cumberland River.”
Carter explained how coordinating maintenance is ongoing and necessary for the locks to support the navigation industry. “It can be very challenging because the locks are old and we have to come up with creative engineering solutions to be able to continue to keep these locks open for the navigation industry,” Carter said.
According to Carter, the process to replace the screens is not easy and it takes careful communication between the Dive Team and the MST to make it happen.
The first step is for the divers to inspect the screens and remove debris to allow the screens to travel unimpeded up the guiderail. The second step is to get the component out of the water, using the heavy lift capability provided by the MST, who had a 100-ton crane above on a USACE barge.
At the beginning of the operations, the divers enter the water and assess the screen, rig shackles onto the lifting components, and then hook them to the block of the crane. They ensure debris is removed so the component rises cleanly out of its mounting position. Then with careful coordination with the crane, the crew raises it up slowly and safely.
The removal of the unit is dangerous work and must be done by professionals.
“USACE Diving is hazardous duty and the divers must go through extensive training and maintain their equipment with great care.” according to Kyle Tanner, the dive coordinator with the Maintenance Section of the Technical Support Branch, Nashville District. According to Tanner, they inspect their gear daily and before each dive. Safety comes first and the team takes every precaution and coordinates to ensure hazards are mitigated. “We mitigate risk by pre-dive planning, equipment maintenance, inspections, and everyone looking out for each other.” Tanner said.
Tanner explained that every member has a valuable role on the jobsite to ensure everyone goes home safely at the end of the day.
“The dive supervisor ensures proper communication between the crane operator and the diver,” said Tanner. “The tenders monitor the lifeline umbilical which provides emergency air and communications to the diver from topside” and they “provide pre-dive equipment checks, dress the diver, and provide support.”
Tanner pointed out that these screens where not designed to be repaired underwater. “When the components where emplaced, future maintenance was not factored into their design,” Tanner explained. “Not only is it a big job, but now they have to deal with very dangerous work conditions.”
Some of the hazards of the job include strong currents, deep depths, zero visibility, diving inside intakes, and decompression sickness. “Diving is one of the most dangerous jobs you can do at the Corps - everyone here is a volunteer, they take the job it seriously. They perform work others wouldn’t dream about doing, or would be too scared to do.” Tanner said.
There is no such thing as an expert diver according to Tanner.
“Accidents can happen to anyone out here, even the most experienced divers. It’s important we not get complacent when performing dive operations and control our emotions underwater,” said Tanner. “One small mess up can lead to a fatality, so we want to ensure diver safety completely every time we perform diver operations.”
Mason Carter said: “The replacement of all the screens will take weeks to accomplish, but there is nothing routine about what these guys are doing on a daily basis - its hard work, dangerous.”

• Date Taken: 08.12.2020
• Date Posted: 08.18.2020 18:51
• Story ID: 376275
• Location: FLORENCE, AL, US