Underwater repairs to Lock 9 should be done in early March
Divers at Lock and Dam 9 prepare to spend the day in frigid water while concrete will be pumped through a tube under the guidewalls and into the cribbing. The divers wear “hot water” suits which have hot water pumped through continually to keep the divers warm. (Photos courtesy of the U.S. Army Corps of Engineers)
The Lock and Dam 9 guidewall is under repairs as concrete will fill in voided areas where rip rap rock once was. Work will continue until early March when the navigation season opens on the Mississippi River.
By Ted Pennekamp
Repairs to the lock extensions at Lock and Dam 9 near Lynxville has been underway since December and is part of a two-year maintenance project by the U.S. Army Corps of Engineers.
“The guidewall crib repairs project is a unique project that is focused on the voided areas under the guidewalls which are an extension of the lock both downstream and upstream,” said Project Manager Joe Schroetter of the Corps of Engineers.
Schroetter explained, the extensions are built on wood pilings and have wooden cribs filled with rock to keep them in place. Over the years, voids have occurred in these cribs, which need to be filled in. Guidewall crib repairs spanning last year and this year have occurred or are being done on locks 4, 5, 5a, 6, 8 and 9.
Schroetter said divers dive down to the base and help pump concrete grout into the voids. The concrete grout has several additives to keep it warm for pumping and also has a foam additive so the final result has a forgiving aspect.
Roughly 1,500 to 1,700 cubic yards of concrete are poured under the guidewalls and into the timber cribbing, said Schroetter.
“The plans and specifications were prepared last year with the intent to have funding to award a contract for the construction over this winter, when the Mississippi River is shut down to navigation. This period is referred to as non-navigation,” said Schroetter.
He noted, Newt Marine Services, of Dubuque, is the general contractor for Lock 9. There are 14 people on the crew, including four divers. He said the Corps of Engineers also has divers to inspect the work and do pre and post videos with underwater cameras.
The divers have special suits that circulate hot water throughout the suits. Schroetter added, the divers work in shifts, but they could stay down all day in the 32-degree water in those suits.
The concrete grout is pumped from a truck and through a tube, which can reach up to 700 feet. The project is done in several steps.
“They do a really good job in not the best of conditions; it’s an amazing thing,” said Schroetter. “No matter what, these guys are working. They have great dedication.”
Schroetter said the project for locks 8 and 9 cost $3.5 million, and it needs to be completed by the start of the navigation season, which is usually early March.
Sub-contractors for the project include concrete supplier Prairie Ready Mix, of Prairie du Chien; Global Infrastructures LLC, diving; Elastizell Corporation of Wisconsin, low density cellular lightweight concrete; Meyer Concrete Pumping & Conveyor Service, LLC, concrete pumping.
Schroetter said the locks have a huge economic impact. If just one lock was closed for a day, $40,000 would be lost. The figures go up exponentially, Schroetter said. For a week, it would be $1.75 million. For a month, $25 million, and for a year, more than $300 million. These costs would be borne by industry, and in turn would trickle through the nation’s economy.
