By Lee Roberts
CHATTANOOGA, Tenn. (July 20, 2016) – Chickamauga Lock is empty and closed to navigation while maintenance crews inspect and make repairs to the miter gates, valves, bushings and other components normally submerged under more than 11 million gallons of water.
The U.S. Army Corps of Engineers Nashville District operates and maintains the 60-foot by 360-foot lock at the Tennessee Valley Authority dam located at Tennessee River mile 471. The lock closed to commercial and recreational traffic July 11 for scheduled maintenance and is expected to reopen Aug. 11.
Greg Cox, chief of maintenance for the Corps of Engineers maintenance team at the lock, said crews are working around the clock to fix cracks in the gates, to repair the struts that open and close the valves, and inspect areas in the culverts where water enters and leaves the lock chamber. He said mechanics are combing over the entire lock while it is dewatered to pinpoint any components that are worn or in disrepair.
“My team is working very hard in extremely hot conditions,” Cox said. “The repairs are on schedule despite the sweltering heat. There isn’t much of a breeze down in the lock, so we’re paying close attention to job safety with the help of our safety officer Chris Clabough and keeping everyone hydrated.”
Inside the lock chamber, 41 employees are working two shifts making welding repairs on the gates, which are huge steel structures that deteriorate from constant exposure to water, making assessments and tedious repairs, ensuring the gates will operate properly for years to come.
Ty Melton, lock and dam equipment mechanic with the Tennessee River Operations Center in Florence, Ala., is spending hours at a time in the empty lock welding the gate fenders and other sections of the gigantic miter gates.
“We’re changing the anode blocks, the square blocks on the end of the gates. It’s basically to keep the gates from corroding fast,” Melton said. “We have to change them out every job because they are usually worn out by the time they are dewatered every five years.”
Melton added that he has been inspecting all the welds on the gates and basically everything that is normally under water. He said it’s been very hot, but he isn’t complaining because he loves working in the outdoors.
Chris Clabough, lock and dam equipment mechanic from Fort Loudoun Lock, is working as the safety officer during the Chickamauga Lock dewatering. He emphasized that all employees have to wear protective gear, keep safe when working around cranes and take precautions when working high up.
“Safety is first priority with the Army Corps of Engineers,” Clabough said. “We want everyone to be 100 percent safe.”
TVA completed construction of Chickamauga Lock and Dam in 1940. The lock has since experienced structural problems resulting from alkali aggregate reaction between the alkali in the cement and the rock aggregate, which results in a physical expansion of concrete structures. Concrete expansion threatens the structural integrity of the lock and limits its life span.
Cox said there are always unexpected challenges that appear once the water is removed. New cracks and excessively worn component connections appear between cycles of dewaterings due to movement caused by concrete growth, he said.
“At Chickamauga over the years we have all learned to expect unforeseen challenges,” Cox added.
The Nashville District is in the process of building a replacement lock. If the current lock were to close prior to its completion, the direct impact would be closure of 318 miles of river and associated movement of approximately one million tons of commodities a year upstream of Chattanooga.
Chickamauga Lock supports not only commercial traffic, but also the recreating public. The lock is the most active lock for recreational vessels on the Tennessee River. More than 3,300 recreational vessels locked through in 2015.
The Nashville District restarted the Chickamauga Lock Replacement Project in April 2016 with a $3.1 million cofferdam stabilization project, and expects to award a two-year-long contract in September 2016 to begin lock excavation, which will prepare the site for future lock construction.
When the new 110-by-600-foot lock is funded and completed, it is expected to speed up the process of locking through, and would process up to nine jumbo barges in one lockage as compared to the one barge per lockage at the existing lock. With efficient funding, the new lock could be completed and able to lock vessels as early as 2022. Final work on the project would extend into 2023.
