Posted on August 12, 2024
MOBILE, Ala. — To maintain certain depths in the shipping channel, the U.S. Army Corps of Engineers dredges approximately 4.1 million cubic yards of sediment from the stretch of the channel in Mobile Bay annually. Since 2014, the majority of that material has been put back in the bay using a method called thin layer placement, where no more than 12″ of sediment is spread out at least 2,500 feet away from the channel.
“A 2014 environmental assessment that ultimately approved the Corps to place material back in Mobile Bay as part of their routine maintenance practices using thin layer placement. There was a lot of science, data collection and studies that went into that. It’s all available online. And so that is our practice today. We place material in the bay. We rotate where we place it off the channel as we move down the system,” said Justin McDonald, Chief of Civil Works Programs and Project management Branch.
McDonald says the Corps will continue with that plan for future maintenance dredging after it finishes deepening and widening the channel next March. McDonald says they expect the quantity of sediment to increase by approximately 15%. Mobile Baykeeper has recently called that disposal method into question and threatened legal action.
“For the next 20 years that maintenance dredging would end up disposing 90 million cubic yards of mud into the bay wreaking environmental havoc on the oyster reefs, the fishery, crab and shrimp populations. We think it’s going to be absolutely detrimental to the health of the bay,” said Cain O’Rear, Mobile Baykeeper Communications Director.
McDonald disagrees with that prediction. He says the Corps knows where sea grass beds are in the bay and does not place dredge material on top of them. McDonald also pointed out that approximately 2.6 million cubic yards of sediment naturally enters Mobile Bay from the rivers every year.
“So, if you took more sediment out of the system that came into the system every year, ultimately the bay would get deeper, right? You would have degraded habitat in the bay. You would have degraded submerged aquatic vegetation habitat. You would have less ability for shorelines to repair themselves because the sediment that they need, that the shoreline needs is no longer there,” said McDonald.
Baykeeper says putting dredged sediment back in the bay threatens Gulf Sturgeon and pointed to 2023 research showing hundreds spend their winters in the bay. McDonald says Mobile Bay is not considered a critical habitat for Gulf Sturgeon.
“We absolutely included that in our consultation for ESA (Endangered Species Act), we acknowledged their presence there. We knew they were there, and we did include it in the analysis we did and that is well documented in all of our documents,” said McDonald.
