Aug 3, 2016

From The Waterways Journal Weekly

By Frank McCormack

The Armistead I. Selden Lock near Sawyerville, Ala.--located at a cutoff in the Black Warrior River just over 40 miles from where it feeds into the Tombigbee River at Demopolis--is nearing the end of a 30-day closure that has seen a new lower miter gate installed, along with some other minor maintenance and repair at the lock.

The lock was last dewatered in 2009, at which time officials with the U.S. Army Corps of Engineers' team that oversees the Warrior-Tombigbee Waterway and lock maintenance contractor R&D Maintenance in Tuscaloosa, Ala., discovered some extensive corrosion and cracking on the lower gate.

"It had corroded and degraded to the point we had to cut out and replace some metal girder flanges," said Danny Hensley, operations project manager for the Corps' Warrior-Tombigbee and Alabama waterways. "We had to replace metal components of the gate just to get by."

Anthony Perkins, navigation manager for the waterway, said the old gate, which was some 60 years old, had close to 200 cracks back in 2009 that had to be repaired.

"When you have that kind of metal loss and section loss in your members, and with the stresses it goes through during lockages, it's more susceptible to cracks," Perkins said. "We did those repairs knowing we needed a new gate."

G&G Steel Inc. fabricated the new miter gate in part at its Russellville, Ala., facility, then finished them at its Iuka, Miss., facility, from which they were delivered by barge to Selden Lock. Each leaf measures close to 50 by 60 feet and weighs about 410,000 pounds. G&G delivered the new gates the first week of July, with the closure commencing July 6.

To move the old gate out and the new gate in, the Corps opted to use a gantry crane spanning the 110-foot-wide lock. The old gate leafs were lifted off the pintle ball, loaded onto a barge and floated out. Then the new leafs were floated into the chamber, lifted vertically and set into the recessed position in the lock wall on temporary stands.

"[The new leafs], which have temporary stands attached to the bottom, have to be picked up and set down in the gate recess," Hensley said. "They're in position, but they're not installed. Putting them in the gate recess allowed us to dewater the chamber in preparation for installation and to make other repairs."

Under the terms of the construction contract, G&G took ownership of the old gate.

With the lock dewatered and the new gate set temporarily in the gate recess, officials from the Corps and R&D Maintenance quickly got to work clearing the lock of silt and inspecting the chamber.

"It's always a matter of inspection and repair," Hensley said. "It's been under water for seven years. We knew the old gates were in really bad shape with a lot of corrosion. The old gates were 60 years old, so they didn't corrode overnight."

All involved said the new gate is a big improvement over the original miter gate.

"Certainly the structure itself is a lot heavier-built than those in the past," R&D's Brooks Ferguson said.

At the new gate, instead of wood timbers comprising the bumper system on the gate, the new leafs feature recycled plastic with a rubber backing. During the current dewatering, crews are installing the same synthetic timbers on the upper gate, along with cleaning and repainting it.

The new gate also has an arched girder assembly rather than sharp angles, which should reduce stress points and lower the likelihood of stress fractures in the future. The new gate also has an improved cathodic protection system, which applies a low voltage current to the gate to help prevent corrosion.

"They're really nice," Hensley said of the two leafs. "We're proud of them and hate to see them go under water and get dirty."

Besides work to get the new miter gate into place, crews have had to replace some sections of the steel where the gate meets the bottom of the chamber when in the closed position. They are also having to fine-tune the anchorage assemblies on the top of the gate.

"We're making adjustments to the gates to get a good fit," Hensley said.

Hensley said, with the leafs in position, anchorage attached to the lock wall, and sitting on the pintle ball, crews are ready to stress the gate and make any needed adjustments. R&D has two crews of 15 working around the clock in order to meet the August 5 goal of completing the project. Hensley said all involved are keenly aware that the closure means the Black Warrior above Selden is totally cut off from the rest of the waterway.

"When we're closed, there's no way around since we don't have auxiliary lock chambers on the waterway," Hensley said. "That makes our closure time critical because, for industry, there is no other way around."

Hensley said, while finishing ahead of schedule doesn't look likely, finishing the project on time is within reach.

Upcoming Work

Hensley said he hopes to begin work on installing rock jetties at Mile 90 on the Tombigbee River near Jackson, Ala., just above the railroad bridge there.

"The river in that location has moved to the west 300 feet since 1979," Hensley said.

Because of the angle at which the railroad bridge crosses the river and the alignment of the channel, making that turn in Jackson is treacherous.

"Traffic can't make that kind of turn," he said.

Dredging is also required each year to provide flanking room for traffic to pass under the bridge.

The jetties are designed to divert the flow eastward and keep the channel more in line with the bridge. Plus, if the channel stays toward the east bank, the Corps won't have to dredge year after year.

"It'll take some time to build them and will take a lot of rock, but traffic will remain open," Hensley said. "We hope to award a contract this fiscal year."

In about two years, the Warrior-Tombigbee Waterway will receive another new miter gate from G&G, this one bound for Holt Lock and Dam on the Black Warrior River near Tuscaloosa in the summer of 2018.

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