More than 10 million gallons of water removed. More than two million pounds of construction materials placed. More than 20 thousand hours of manpower expended. And, all of it done in treacherous conditions due to record low temperatures. These statistics represent a small snapshot of the work recently completed at Lock and Dam 22 as the lock chamber was dewatered and maintenance to the infrastructure was performed.
Lock and Dam 22, located on the Mississippi River near Saverton, Mo., falls under the purview of the Rock Island District's Mississippi River Project. Crews from the Project's Maintenance Section maintain 12 lock sites on the river, working throughout the year to keep the critical vein of commerce open to navigation. According to Aaron Dunlop, Chief of the Maintenance Section, work at Lock and Dam 22 began in December and was completed in early March. Dunlop said the lock had not been dewatered in nearly two decades.
"Historically in the Rock Island District, locks are typically dewatered as part of a major rehabilitation which is performed by a contractor," Dunlop said. "That work was last done at Lock and Dam 22 more than 20 years ago so it was time to pursue some critical maintenance work that needed to be done."
Dunlop said the critical maintenance work included the installation of four new miter gates, bulkhead sill beams and struts, a new bubbler system, bulkhead stands, and valve cables; as well as an inspection of the chamber and the associated systems. All of this equipment, including the systems within the chamber, are typically under water thus the need to dewater the chamber.
The process of dewatering the lock chamber involved the use of four, 12-inch pumps, Dunlop said. Those pumps, working simultaneously, could remove more than 18,000 gallons per minute which equated to nearly 10 million gallons removed throughout the duration of the project. When the chamber was dewatered, navigation operations through the lock had to be stopped. The scheduling of the project was done to minimize impact to the river industry during the cold-weather season.
"In December there was a short closure to install the downstream bulkhead sill beam which included nearly two entire days of diving operations and heavy lift crane work," Dunlop said. "This work enabled the downstream bulkheads to be properly sealed at the bottom of the chamber once the dewatering closure began in January."
After the work on the downstream bulkhead was complete, Dunlop said the rest of the process worked from upstream to downstream.
"Once the chamber was dewatered, work on the bulkheads began," he said. "Tarps were placed on the bulkheads and heated to reduce the ice buildup. Then, concrete was poured to permanently affix and seal the bulkhead sill beam. Bubbler pipes were installed in the gate recesses, and a bubbler screen and crossover piping were installed and encased in concrete."
David Schipper, lockmaster at Lock and Dam 22, said the new bubbler system was a very important maintenance need for his operations. Schipper said the bubbler system helps remove ice from the recesses so the gates of the lock can open and close fully. The bubbler system also helps during the non-winter months by helping to remove objects like driftwood which can be a hindrance to the gate operation.
"The old bubbler system had become more or less useless," Schipper said. "Without a bubbler system, locking can become nearly impossible. It would be a very slow process. We were really happy to get the new system."
After the bubbler system and other repairs were in place, the crews made adjustments to anchor bars and seals to ensure the lock's gates were properly aligned and operational without interference. Dunlop said the project concluded with clean up and inspections.
"Debris was removed from the lock chamber, Tainter valve wires were replaced, and a full Operational Condition Assessment inspection was performed by a joint team of Operations and Engineering Staff," he said. "Finally, once all the necessary work was completed, the lock chamber and Tainter valve bulkheads were all removed from downstream to upstream and the lock was placed back into service. All of this was done in two short months."
The quick completion of the work meant the lock was back in service before the traditional navigation season began. But, more importantly, Dunlop said, all of the work was completed safely without a lost-time accident.
The timely, safe completion of the project was a success but Dunlop said there were plenty of challenges along the way. Most significant of those challenges came in the form of Mother Nature. The crews endured working in temperatures that dipped below zero for more than 12 days. For 47 days, the temperatures never climbed above freezing.
"Weather is always a part of our work environment," Dunlop said. "But these extremely low temperatures were hard on both our equipment and employees. I would estimate that at least two weeks of the project's schedule were dedicated to resolving cold weather issues like ice buildup and general site safety cold weather issues."
While endeavoring through the challenges of a frigid environment, the crews completed the $10 million project with a combination of contractual and maintenance efforts. Although it had been nearly 20 years since a project of this magnitude was taken on at Lock and Dam 22, modern technology was providing some assistance that was not available the last time this lock was dewatered.
Dunlop said the team implemented the use of aerial drones to provide photography which documented the work being done.
"This is a new capability that has already proven invaluable," Dunlop said. "The ability to document the work being completed showcases the capabilities of the Maintenance Section for purposes of regional coordination and information sharing. The small drone was much more cost effective than traditional aerial photography which would have required the rental of a commercial plane."
As unmanned aircraft snapped pictures and sub-zero temperatures challenged the crew, a critical piece of the District's infrastructure got the imperative maintenance it needed to ensure its reliability. It is a project Dunlop described as "teamwork at its finest."
"This was a unique opportunity for our maintenance crews to integrate with staff from the Lock and Dam Section, Engineering, Project Management, Safety, and the District's dive team who all worked together to ensure project success," he said. "We even enlisted support from the St. Paul District's lock dewatering experts to ensure that everything would run smoothly as they have been doing dewaterings each winter for many years."
Looking to the future for the rest of the District's infrastructure, Dunlop said there are plans to increase these kinds of regional work efforts with each successive project. The goal in doing this is to ensure the District's valuable resources are being used as effectively and efficiently as possible.
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