Finished Kentucky Lock Enables Dry Dig Conditions Adapted from Information by the U.S. Army Corps of Engineers In Grand Rivers, Kentucky, the completed cofferdam at the Kentucky Lock Addition Project paved the way for downstream excavation work preparing the site for construction of the remaining portion of the new lock chamber. Jeremiah Manning, resident engineer with the U.S. Army Corps of Engineers Nashville District, said Johnson Brothers Constructions, the Corps’ partner on the $68 million downstream cofferdam contract, turned over the completed cofferdam. “We had a great big challenging project,” Manning said, referring to river conditions in 2018 and 2019, delaying construction progress. He added, “Hopefully, the tide is turning on this project, and we’re isolating ourselves from our biggest risk factor, which is the tailwater at Kentucky Dam.” Johnson Brothers Construction placed the first of ten concrete shells in 2018, using an innovative lift-in technique, which employed a specially designed floating gantry crane and four spuds to hold the shells in place on the prepared rock stream bed. The contractor placed the final concrete shell in early 2020, and altogether the ten shells form the permanent portion of the cofferdam and the downstream lock wall. In mid-2020, work progressed on the main construction of the temporary cellular structure of the downstream cofferdam. The contractor installed circular steel sheet-pile structures into the riverbed and put granular fill inside each one to collectively form a dike. Jody Robinson, contract administration team lead at Western Kentucky Area Office, said the cofferdam is the most important spot on the jobsite because its specific purpose is to hold back the tailwater from construction activities. Heeter Geotechnical Construction, contractor for the $58 million downstream excavation contract, is installing a grout curtain into the cofferdam. When grouting is completed, water behind the cofferdam can be pumped out, making it possible to excavate in dry conditions. Heeter had already been excavating in areas more upstream near the completed portion of the upstream lock chamber. Earlier this year, the Nashville District worked on design and acquisition for the next phase of the project and planned to bid the Downstream Lock Monoliths Contract this year. The new contract will structurally finish the new lock’s chamber and place all the remaining concrete for the 100-foot by 1200-foot navigation lock at the Tennessee Valley Authority project. The contract period will be roughly 60 months and include limited rock excavation, placement of about 400,000 cubic yards of concrete in the construction of 51 lock monoliths, fabrication and installation of downstream miter gates, grouting the lock wall foundation, backfill of one million cubic yards of soil, as well as fabrication and installation associated with mechanical features of the new lock. 61 DECEMBER 2021 WorldWide Drilling Resource® RENEW - SUBSCRIBE NOW! Completed cofferdam at the Kentucky Lock. Photo by Leon Roberts. C&G
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