MEMPHIS, Tenn. -- The Memphis District officially welcomed a new, $25.5 million Bank Grading Unit (BGU), April 11, 2023, when it docked at its new home port at Ensley Engineer Yard in Memphis, Tennessee
Constructed in three years, the new BGU is replacing the district’s legacy bank grader, and with nearly 75 years of operations in the books, it’s safe to say the 1949 barge-mounted Bucyrus-Erie dragline model is ready for retirement.
“The Bank Grading Unit is critical to the overall Regional Channel Improvement mission and is a vital piece of the entire revetment operations process,” Regional Channel Improvement Coordinator Jake Storz said.
Revetment operations are primarily the preparation for and placement of articulated concrete mattress (ACM) from the Mississippi River water's edge out to the toe of the riverbank slope. Revetment stabilizes the riverbank, supports proper navigation channel alignment, and provides a frontline of defense for the levees along the river.
The river industry depends on operations as important as revetment. With that said, the process is only as good as its weakest link, and that weak link was oftentimes the district’s aging bank grader.
“In past years, the legacy BGU has had major maintenance issues midseason, causing the Regional Channel Improvement Team to modify the season to allow for the continuation of sinking articulated concrete mattress on the Mississippi River,” Storz said.
"The condition of the existing plant equipment was undoubtably our greatest challenge throughout the 2022 revetment season," Channel Improvement Project Coordinator Andrew Smothers said. "For example, the (vintage) Bank Grader was down a total of 26 days due to catastrophic engine failure."
With the legacy bank grader at the end of its lifespan, the district is more than ready to start using the new grading unit.
Constructed to directly support the Mississippi River Regional Channel Improvement Revetment Program, the new BGU comes in at 1.1 million pounds and equipped with a 25-cubic-yard-capacity bucket – that’s ten more cubic yards than the legacy grader’s bucket.
“The new Bank Grading Unit will be much more reliable than the legacy grader, have a much smaller maintenance cost than the legacy grader, and will speed up the overall process of grading banks on the Mississippi River,” Storz said. “All of these reasons are directly supportive of a more efficient revetment process.”
The replacement BGU is also powered by a CAT Tier 4 diesel generator, making it much more ecofriendly than its predecessor. To meet Tier 4 standards, diesel exhaust fluid (DEF) is injected into the exhaust stream to convert pollutants into water, oxygen, and nitrogen and, at the same time, reduce two exhaust pollutants: particulate matter and of oxygen nitrates.
The district awarded two separate contracts for the new BGU totaling approximately $25.5 million using Mississippi River and Tributaries Channel Improvement Revetment Construction funding. This funding was re-allocated in 2019 when supplemental funds were made available to support replacement of the new Mat Sinking Unit, Armor 1. The Mat Sinking Unit is a Vicksburg District asset. Armor 1 is still being constructed but is expected to be complete and ready for use for the 2024 revetment season.
The first contract, for the unit’s dragline machine, was awarded to Seatrax, Inc., of Houston, Texas, in July 2019. A second contract for the unit’s barge was awarded to Conrad Shipyard of Morgan City, Louisiana, in September 2019. Both contractors worked together with technical support from the USACE Philadelphia District’s Marine Design Center and the Memphis District team to complete and deliver this key piece of plant to support the Lower Mississippi River Channel Improvement project.
The district is planning a dedication ceremony for the new BGU on May 2. Details to follow as May nears.
To learn more about revetment operations, including clearing and snagging, bank grading, and the Vicksburg District managed ACM Sinking Unit, visit the Memphis District Revetment Webpage.