Crews Repair Lock 25 Four Days After Anchorage Bar Fails
Upper Mississippi Lock 25 reopened December 18, four days after an unscheduled closure, thanks in part to fortuitously placed repair crews and forethought in retaining a previously replaced component.
An anchor bar—consisting of threaded rods with eyelets on each end, used to connect the concrete-embedded anchorage to a miter gate—failed on the downstream land wall gate about 4 a.m. December 14, forcing the closure at the lock, located at Upper Mississippi Mile 241.4 near Winfield, Mo.
Andy Schimpf, operations manager-Mississippi River Project for the St. Louis Engineer District, said the failed anchor bar was part of a contract to replace the entire gate anchorage systems at locks 24 and 25 in 2020.
The district retained the original anchor bars, and engineers quickly determined that they could be used to replace those installed in 2020.
He stressed that the concrete part of the anchorage and metal plating that protrudes from the concrete and out through the recess remained in good shape from their 2020 replacement. Only the anchor bar had failed.
Repair crews happened to be close at hand. The Rock Island District’s medium lift crew was at Lock 25 to prepare for a scheduled dewatering in January. The Rock Island District’s heavy lift crew and crane were at Mel Price Lock and Dam, where scheduled repairs, including installation of a new 540,000-pound liftgate, were also due to begin next month. These two teams joined forces with the St. Louis District crew to quickly put a repair plan into place.
The crane and crews arrived on December 15 and rigged the Quad Cities II crane to prepare to lift the gate. That took weight off the anchors, which allowed the damaged bar to be removed. The work was not without some difficulty as crews initially had issues removing secondary anchor pins. As a result, the gate was pulled December 16 and set on the barge, and a 150-ton jack was used to remove the pins throughout the day.
Engineers then inspected the gate, finding no major issues, although they had spare anchor bars and pins on site in case they were needed, Schimpf said. Some damaged, embedded metals were repaired.
Crews installed the new anchor bar, and divers inspected the pintle and checked the recess for debris before setting the gate back in place the afternoon of December 17. However, they found that they had some difficulties adjusting the alignment with the new anchor bar. Since the crane was available on site, the gate was pulled to make adjustments.
The gate was reset for a final time the morning of December 18.
“Final adjustments and alignments have been made,” Schimpf said that afternoon. “Right now we’ve got divers in the water checking the sill and the quoin area.”
At the time, he said, seven northbound and seven southbound tows were waiting to lock through the chamber.
Following final testing, the lock reopened to navigation the evening of December 18.
Schimpf said the district was investigating the cause of the component failure. Engineers are using strain gauges to measure the loading on the anchor bars, he said.
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Featured Photo Caption: Heavy lift crane Quad Cities II, from the Rock Island Engineer District, lifts one of the miter gates at Lock and Dam 25. The lock experienced an equipment failure December 14, resulting in a temporary emergency closure to all navigation. (Photo by Aaron Berogan/St. Louis Engineer District)
