The commercial shipping industry moves approximately 11 million tons of cargo annually on the McClellan-Kerr Arkansas River Navigation System. That cargo generates an estimated 4.5 billion dollars in sales for the nation.Brig. Gen. Christopher Beck, Commander of the U.S. Army Corps of Engineers Southwester Division and Col. Eric Noe, Commander of the USACE Little Rock District discuss recent critical maintenance on the MKARNS as well as why its imperative crews keep the 50-year-old navigation lanes up and running.Crews from the U.S. Army Corps of Engineers Little Rock District set two cofferboxes around the center-post receivers in the David D. Terry Lock Chamber near Scott Arkansas on Aug. 19. David D. Terry Lock and Dam is one of 13 structures on the McClellan-Kerr Arkansas River Arkansas River Navigation System in Arkansas that allows the shipping industry to move commerce up and down the system.Ensuring center-post receivers can be set and secured is a critical part of a lock dewatering. The lock chamber is 110 feet wide. The center-post allows 50-foot stop-logs to be placed on both sides.The cofferboxes allow maintenance crews to pump out the water, inspect the receivers and perform a pull test to ensure they still function as intended. The boxes were designed after crews found other center-post receivers along the system to be inoperable. Depending on the configuration, the locks with inoperable center-post receivers must be retrofitted to use costly 110-foot stop-logs or have the center-post anchor bolts replaced.If the existing center-post receivers pass the pull test they won’t require costly modifications.