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

U.S. Army Corps of Engineers, Jacksonville District
Published Aug. 11, 2020
The Corps team arrives on site before sunrise to begin dewatering the Ortona Lock.

The Corps team arrives on site before sunrise to begin dewatering the Ortona Lock.

The first step in work phase is to get divers into the water to clear and clean the needle slots, which are under the water on the bottom of the lock chamber. Needles, which look like metal panels, will be installed into the needle slots. The needle system serves as a temporary “cofferdam” to isolate a part of the structure for dewatering.

The first step in work phase is to get divers into the water to clear and clean the needle slots, which are under the water on the bottom of the lock chamber. Needles, which look like metal panels, will be installed into the needle slots. The needle system serves as a temporary “cofferdam” to isolate a part of the structure for dewatering.

All components must be inspected months in advance, and are placed on the floating plant, which includes a barge-mounted crane and a tug to tow it to the work site. Panels for the needle system are stacked up on the deck so they are ready to be installed, and other equipment, such as large pumps are on board as well.

All components must be inspected months in advance, and are placed on the floating plant, which includes a barge-mounted crane and a tug to tow it to the work site. Panels for the needle system are stacked up on the deck so they are ready to be installed, and other equipment, such as large pumps are on board as well.

The crane operator begins the installation by setting a steel I-beam into the girder recess notch in the lock wall, starting with the upper or upstream end of the lock.

The crane operator begins the installation by setting a steel I-beam into the girder recess notch in the lock wall, starting with the upper or upstream end of the lock.

The crane operator lifts the needles that have been staged on the barge.

The crane operator lifts the needles that have been staged on the barge.

The crane operator picks up and rotates the needles toward the needle slots, where they are inserted close enough together that they will seal. Divers are again in the water to help to assure that the needles are placed properly.

The crane operator picks up and rotates the needles toward the needle slots, where they are inserted close enough together that they will seal. Divers are again in the water to help to assure that the needles are placed properly.

The team secures the needles to the girder. The natural hydraulic pressure of the river presses the needles toward the girder, and also holds a curtain that is installed on the upstream side of the needles to provide an additional seal.

The team secures the needles to the girder. The natural hydraulic pressure of the river presses the needles toward the girder, and also holds a curtain that is installed on the upstream side of the needles to provide an additional seal.

The needles have been set in place in the needle slot in the bottom of the lock chamber and secured to the I-beam girder across the end of the lock chamber, the first step in isolating the lock chamber so it can be dewatered.

The needles have been set in place in the needle slot in the bottom of the lock chamber and secured to the I-beam girder across the end of the lock chamber, the first step in isolating the lock chamber so it can be dewatered.

Seen from the upstream side, the needles have been placed in slots to form a temporary “cofferdam” adjacent to the yellow-and-black pie-shaped lock sector gates. The needle slots are located in the bottom of the lock chamber, about 30 feet on either side of the each set of gates. This makes it possible to dewater just one set of gates at a time, or to dewater the entire lock chamber at once.

Seen from the upstream side, the needles have been placed in slots to form a temporary “cofferdam” adjacent to the yellow-and-black pie-shaped lock sector gates. The needle slots are located in the bottom of the lock chamber, about 30 feet on either side of the each set of gates. This makes it possible to dewater just one set of gates at a time, or to dewater the entire lock chamber at once.

On the lower end of the lock, crews must work across the girder in wetter conditions, wearing life vests for safety. The rigger or signalman on the barge keeps a close eye on the installation. He uses both a headset and hand signals to indicate “stop” to the crane operator as the second needle is properly fitted in the slot. It takes a significant amount of experience and expertise for a crane operator to maneuver and place each needle down into the small slot, fitting them close enough together that the two pieces can be sealed together with a narrow black seal, visible on the left side of the second needle.
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On the lower end of the lock, crews must work across the girder in wetter conditions, wearing life vests for safety. The rigger or signalman on the barge keeps a close eye on the installation. He uses both a headset and hand signals to indicate “stop” to the crane operator as the second needle is properly fitted in the slot. It takes a significant amount of experience and expertise for a crane operator to maneuver and place each needle down into the small slot, fitting them close enough together that the two pieces can be sealed together with a narrow black seal, visible on the left side of the second needle.

The crew moves the second needle, still suspended from the crane, close to the girder. A diver also checks to be sure the needle has been properly placed.
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The crew moves the second needle, still suspended from the crane, close to the girder. A diver also checks to be sure the needle has been properly placed.

The tag line man helps to steady and control the load so it doesn’t twist as it is moved into position.
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The tag line man helps to steady and control the load so it doesn’t twist as it is moved into position.

As each needle is added, the crew secures it to the girder.
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As each needle is added, the crew secures it to the girder.

Needles have been placed almost completely across the lower end of the lock.
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Needles have been placed almost completely across the lower end of the lock.

The tag line man helps keep the final seal facing in the right direction is moved into place.
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The tag line man helps keep the final seal facing in the right direction is moved into place.

A pump is installed and secured, so water can be pumped out of the lock chamber, providing a relatively dry area for equipment, inspections and repairs.
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A pump is installed and secured, so water can be pumped out of the lock chamber, providing a relatively dry area for equipment, inspections and repairs.

Multiple pumps are used to pump water out of the lock chamber for several hours or even overnight.
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Multiple pumps are used to pump water out of the lock chamber for several hours or even overnight.

Once the water level has gone down, a 4 Man Basket is used to lower the crew into the chamber so they can remove vegetation and lift native fish up and out of the chamber.
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Once the water level has gone down, a 4 Man Basket is used to lower the crew into the chamber so they can remove vegetation and lift native fish up and out of the chamber.

Equipment lowered into the chamber for inspections and repairs. This is what the bottom of a lock looks like – it’s not flat!
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Equipment lowered into the chamber for inspections and repairs. This is what the bottom of a lock looks like – it’s not flat!

This JLG lift is used for inspections.
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This JLG lift is used for inspections.

Needed repairs can be made in the shade.
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Needed repairs can be made in the shade.

Corps team members wearing safety harnesses hook the crane assembly to the top of the narrow slide plate..
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Corps team members wearing safety harnesses hook the crane assembly to the top of the narrow slide plate..

Corps team members exit the lock chamber as everyone else watches eagerly in anticipation of the symbolic final moment of the dewatering process.
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Corps team members exit the lock chamber as everyone else watches eagerly in anticipation of the symbolic final moment of the dewatering process.

The crane operator starts to lift the slide plate, instantly relieving the hydraulic pressure and allowing water to start refilling the lock chamber.
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The crane operator starts to lift the slide plate, instantly relieving the hydraulic pressure and allowing water to start refilling the lock chamber.

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.
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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.

Keeping busy federal waterways like the Okeechobee Waterway open for navigation is challenging.

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 U.S. 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,” 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 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.

Scroll through the series of photos above to learn about the dewatering process.

Once the inspections and repairs have been completed, the team prepares to rewater the lock.

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.”

The U.S. Army Corps of Engineers Jacksonville District constructed, operates and maintains five locks along the 154-mile Okeechobee Waterway, which allows safe passage of vessels through the middle of the state, from the Atlantic Ocean near Stuart to the Gulf of Mexico near Fort Myers in south Florida. On the east coast, they include the St. Lucie Lock and Dam on the St. Lucie (C-44) Canal in Stuart, and the Port Mayaca Lock and Dam on the east side of Lake Okeechobee. The Moore Haven Lock and Dam is located on the west side of Lake Okeechobee, along with the Ortona Lock and Dam and the W.P. Franklin Lock and Dam on the Caloosahatchee River (C-43 Canal).