First Concrete Pour Completed At Demopolis Lock
The concrete trucks began arriving at Demopolis Lock on the Tombigbee River in rural Alabama around 4 a.m. April 11 for the first of seven concrete pours to repair and modify the lock’s upper miter sill, following its January 16 failure.
“It poured well and leveled out well,” said Anthony Perkins, operations project manager for the Black Warrior-Tombigbee Waterway (BWT). “They poured all the way across the lock, a 5-foot lift.”
Because the repair work at Demopolis is taking place in the region’s traditional rainy and high-water season, Mobile Engineer District officials opted to pour concrete “in the wet.” Thus, even though the area was forecast to receive flooding rain just ahead of the scheduled April 11 pour, work would have moved forward regardless, without delay.
“It has come up some from yesterday, but it’s not going to get as high as originally forecast,” Perkins said. “It’ll be good that it’s lower, but we’re really prepared even if the water’s higher.”
Perkins said the concrete from nearby Ready Mix USA has been specially formulated for the water in the lock chamber, with an anti-washout agent added to allow it to set underwater. In all, about 30 truck loads carrying a total of 205 cubic yards of concrete convoyed from the batch plant to Demopolis Lock throughout the morning. The trucks fed their concrete into a pumper truck, which had a retractable arm attached to a pipe that extended into the water.
Contractors involved with the debris removal, site preparation and the concrete pour included Thompson Engineering, R&D Maintenance, Brennan, Ready Mix USA, Pyramid and Cemex.
“It was a big milestone to get this first pour in,” Perkins said. “This is one of the largest pours we’ve ever done, especially on our project.”
Because this was the first of seven pours, the newly laid concrete will need to cure about seven days. Perkins said the next pour is set for April 18. After that, subsequent pours will need about three days to cure. Temperature sensors throughout the concrete will monitor the curing process.
“The last two pours may take a little longer, just to make sure we get all the steel in place and the concrete filled in completely,” Perkins said.
While the first pour took place a few days ahead of schedule, the Corps is sticking to the May 30 target date for returning the lock to service. Perkins said, besides the last lift or two curing a little longer, contractors will also have to apply a small amount of grout and install rubber seals around the sill. Then, they will have to make adjustments to the upper miter gate.
According to Ryan Reich with the Mobile District, who spoke at the April 11 meeting of the Inland Waterways Users Board, the district has spent approximately $23 million thus far on the repair work at Demopolis. Given the location of Demopolis Lock, that’s money well spent, Reich said.
“It is a critical lock for our district,” he said.
Demopolis is the first lock below the confluence of the Black Warrior and Tombigbee rivers, which means commercial traffic on both the BWT and the Tennessee-Tombigbee waterways must transit Demopolis to get to and from the Port of Mobile.
At 70 years old, Demopolis is the oldest lock on the system, but due to its location, it’s also the busiest. On a three-year average, Demopolis Lock sees about 10.5 million tons of cargo pass through, by way of 1,855 commercial lockages. As part of the Great Loop, the lock also sees close to 450 recreational lockages per year.
Following Reich’s presentation, Canal Barge Company’s Spencer Murphy, chairman of the Users Board, asked what the Corps was doing to assess the risk of a similar failure at other locks. Reich said that Mobile District personnel are analyzing the other locks on the system to assess risk of failure and assessing potential contributing factors, like cold weather.
Caption for photo (click on image for full photo): The first concrete is poured for the Demopolis Lock repair project. (Photo courtesy of Anthony Perkins)
