Lock steps: Dewatering is the first step before lock repairs can begin

Ironically, to keep locks open, you’ve got to close them. To do work on a waterway structure, you’ve got to dry it out first, a process called dewatering.

“Last year, our lock operators locked through 25,486 vessels safely during 18,140 lockages along the Okeechobee Waterway,” said Bill Keeney, the U.S. Army Corps of Engineers Jacksonville District’s supervisory facility management specialist for the west region locks and dams. “We want to do everything possible to keep these locks open for our recreational and commercial users. To do that, we’ve got to close the locks periodically for maintenance and repairs.”

“It’s important for our users to learn about the dewatering process that we’ve got to go through before we can even begin our repairs,” said Keeney. “Otherwise it’s tough to understand why we’ve got to close down the waterway for a week or two at a time. Regular maintenance saves both time and money, since emergency repairs take longer and are usually very costly. Think of it as changing the oil and fluids in your car regularly, versus having to do major repairs.”

The Army Corps of Engineers South Florida Operations Office will be dewatering the Moore Haven Lock on the west side of Lake Okeechobee to do repairs on the upper lock gates only, in August 2020.

“We have been having some intermittent mechanical issues with the upper lock gates at the Moore Haven Lock and Dam,” said Keeney. “We tried to troubleshoot it several times with the remotely operated vehicle, or ROV, a kind of mobile underwater robot, but weren’t able to determine the cause of the problem.”

“That’s why it’s necessary to close the lock down temporarily in August,” said Keeney. “In order to do lock repairs, you’ve got to close down the lock to navigational traffic and dewater the upper lock gate area. It’s a lot more complex than just shutting the lock gates and pumping the water out.”

“There are three reasons for the Corps to dewater a lock,” said Paul Jacques, chief of maintenance and contract quality assurance in the Corps’ South Florida operations office. “One is periodic maintenance for things that we can predict. For example, we know that over time, seals will need to be replaced. We must also dewater structures for periodic inspections, where we are required to perform a full test on all structural elements, including the gates. In August, engineering is going to take advantage of the Moore Haven dewatering to do their periodic inspection as well, to save cost. If we perform the required periodic maintenance and inspections, we minimize the likelihood of needing to close down the lock for emergency repairs.”

The dewatering process requires months of advance planning and coordination, the mobilization of equipment on site, and a small army of close to 30 people with experience and specific skill sets working and solving problems together for a week or more during long hot days under the searing south Florida sun.

The Corps temporarily closed down and dewatered the full lock chamber of the Ortona Lock and Dam for two weeks in 2018. That event serves as a good example of how many steps are involved in the dewatering process.

The first step of the process onsite is a very early morning safety briefing for all team members. One of the things that the team must work around is lightning, especially since there are very tall cranes on site. If there is a lighting strike within 10 miles of the work area, operations are closed down until 30 minutes after the last lightning event.

Manatee observers are on site an hour before work begins, and during all work in or above the water. If a manatee or other threatened or endangered species is within 50 feet of the operation, work in or on the water must stop for at least 30 minutes from the time the last one was spotted.

During the first day or two, once manatee observers are on site, divers are suited up and begin their initial work. At this time, the lock may be closed only intermittently, and reopened to lock vessels through in between dives.

Within a fraction of a second, water rushes in to fill the lock chamber. Though it means that the necessary repairs and inspections have been completed and it’s the symbolic end of the dewatering process for the team, there’s still a huge amount of work to be done. The needle system still needs to be removed, and all of the equipment must be demobilized.

Still, it’s a victory, and it means that the lock will be reopened soon, and vessels will be locking through once more.

“When we do maintenance repairs on a lock, our goal is to get in, identify and fix the problem, and re-open the lock as quickly and safely as possible,” said Jeff Fallin, chief of the South Florida Operations office in Clewiston. “The dewatering process is a true example of teamwork at its best. Everyone is working together and pulling in the same direction to accomplish a goal.”

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