Wilson Lock Repairs Could Stretch Into April
The Corps of Engineers hopes to know by December 1 whether repair efforts at Wilson Lock, located at Tennessee River Mile 259.4 in Florence, Ala., will permit limited operation of the main chamber between two anticipated dewaterings.
During an October 29 call with industry representatives, Brian Mangrum, chief of the Nashville Engineer District’s technical support branch, went over details of a plan that includes temporary weld repairs by December 20 and replacing gate components to effect permanent repairs between January 20 and April 20, 2025.
More funding will be needed to complete the permanent repairs, Mangrum said, adding that he hoped to know how much within about a week. The Nashville District has been in contact with regional headquarters in Cincinnati about the need.
“They do recognize that it’s the highest priority in the region right now and are tracking the need,” Mangrum said.
It is possible that traffic will be able to transit the main chamber between the two dewaterings, Mangrum said, adding that it is not clear whether more typical tows will be moved or whether it might be limited to those too large to traverse the auxiliary chamber. Mangrum said he has been in talks with United Launch Alliance, which needs to move rocket stages through the lock in mid-December from the manufacturer in Alabama to the launch site in Cape Canaveral, Fla.
The main lock chamber has been closed since September 25, after operators reported hearing popping and cracking noises. Divers and remotely operated vehicles (ROVs) later discovered cracks in the lower steel girders and pintle castings of both lower gates. The auxiliary lock remains operational, with only one or two barges able to transit at a time, depending on size. Mangrum said that, as of the morning of October 29, there were 252 cuts in the queue, meaning a delay of close to 11 days for tows waiting to transit the lock.
“That’s a big impact,” he told those on the call. “It’s slow and cumbersome, and you all are really getting beat up by this closure of the main chamber. I understand all that. I understand that frustration is growing on knowing the exact timeline for these repairs so that we can assist you in planning out what the movement of your goods needs to look like in the coming weeks and months.”
The lock chamber cannot be dewatered until its lower caisson slot is repaired and the concrete allowed to cure. Mangrum said that work is expected to be completed by November 8. On November 1, the Tennessee Valley Authority is scheduled to assist with removal of excessive sedimentation on the closure structure seal to prepare for the dewatering inspection and repairs.
Temporary Repairs
During that first dewatering, which will be supported by the Great Lakes and Ohio River Division’s Heavy Capacity Fleet, crews will set the caisson on the lower end to dewater the chamber.
“Once the chamber is dewatered, we’ll clean and inspect the gates and pintles to verify the repair plan and perform nondestructive testing on those components,” Mangrum said. “At this point we have gathered as much information as possible using our divers and ROVs, but there will be some level of discovery and adjustment to our plans once we’re able to inspect those components in the dry.”
The work will include qualifying the gate steel, he said.
Weld repairs are expected to be performed on or about November 23, he said. Crews will also measure and perform a full inspection of the chamber’s quoin gaps, looking for any areas of concern. Mangrum said that inspection will be an important step in a root analysis of why the pintle castings and gate girders cracked.
Permanent Repairs
During the second dewatering, also supported by the Heavy Capacity Fleet, each gate leaf must be jacked up to access pintle components and bushings.
The gate-lifting plan is due no later than November 18, Mangrum said. He added that the Corps has identified two sets of three hydraulic jacks, which are at a vendor for recertification. Delivery of the jacks is expected by early December. An additional five hydraulic jacks are on hand with the Heavy Capacity Fleet, he said.
Mangrum said a key development over the past week involved the Corps and TVA determining how to replace the pintle components.
“Originally the lead time for traditional casting of replacement in kind was approximately a year, so we’ve been exploring other avenues, to include additive manufacturing or forged components, trying to find the best solution, from a time and quality standpoint, as possible,” he said.
Both additive manufacturing and forging replacements were expected to take about 12 to 16 weeks. Ultimately, the Corps and TVA determined that TVA’s Power Services shop will order and fabricate the needed components using a forging method, Mangrum said. He added that the Corps of Engineers and TVA metallurgists are working to determine the final material specifications.“We are very close to making that determination,” he said. “We do know the material specifications for that traditional casting and really are just in the final stages of confirming what that equivalency is with the class of materials that we need to forge that component rather than cast it.”
During the second dewatering, Mangrum said crews will also complete any additional repairs needed on the gates, to include additional stabilization, make contact block adjustments as needed and perform operational testing prior to returning the lock chamber to service.
Answering Questions
During the call, Harley Hall of Tennessee Valley Towing asked if it was possible that the main chamber could be used between dewaterings even if only one gate was operable. That could potentially allow for a helper boat and a string of three barges at a time to transit the lock.
“Three at a time is better than one at a time,” he said.
Mangrum said it was something the Corps could consider, but that the primary concern seemed to be the stress on the gates from filling and emptying the chamber, rather than swinging the gates.
Marty Hettel of American Commercial Barge Line asked Hall if having a TVA assist boat would help improve locking times in the auxiliary chamber rather than the current self-help method. Hall said that was doubtful because there are plenty of boats on hand in the queue to help out.
Hettel also asked if the main and auxiliary chambers could be operated at the same time if both chambers were operable. Brian Brewer with the Corps answered that it would depend logistically on where boats are stationed. Brewer said at times it might be necessary to shut down the auxiliary chamber to make room in the canal to use the main chamber.
The Corps plans to continue the weekly industry calls as necessary to continue providing updates on the repairs.
