The Army Corps of Engineers is considering an expansion of the area where “beach-quality” material is disposed from its dredging activities in Mobile Bay — potentially putting beneficial sand closer to Dauphin Island, where residents have faced eroding shorelines for years.
The Corps’ Mobile District is evaluating economically and environmentally feasible ways to expand the federally maintained Mobile shipping channel, which is used daily by large commercial and shipping vessels accessing the Port of Mobile.
It’s a “a huge piece of the economic engine” both locally and nationally, according to District Commander Col. James A. DeLapp. However, maintenance dredging of the channel is a sore subject for some Dauphin Island residents who blame it for the town’s disappearing beachfront.
The Corps annually digs up millions of cubic yards of sediment — mostly mud, sand and clay — to maintain the channel’s current depth and width, but it has also long held the activity has no “measurable impact” on Dauphin Island’s erosion problems. However, that’s a position many residents vehemently dispute and have previously litigated in federal court.
Since 1999, the Corps has placed dredged sand in the Sand Island Beneficial Use Area near the old Sand Island lighthouse, but property owners have argued for years it would be better for the island if those disposals were made closer to its shores.
For the first time last week, the Corps publicly discussed a proposal that would change its 20-year-old practices by expanding the Beneficial Use Area to the northwest toward Pelican Island.
“When you look at [sediment] transport rates from 1999 to current, it’s transported out of the site at about half the rate we’ve put it in,” Corps engineer Justin McDonald said. “So, it’s moving out at a lower rate than we’re putting it in, and it’s accumulating.”
Those comments came during a public input meeting last week about the Corps’ ongoing study of how expanding the shipping channel might impact Mobile Bay. Ultimately, Congress will use a report from the study to determine how, or if, the channel should expand.
Former Corps biologist Glen Coffee, who’s become an organizer for a group concerned with erosion at Dauphin Island, sees the proposed expansion as an acknowledgement of what he and others have been saying for years: The “beneficial” use area has not been very beneficial for Dauphin Island.
Coffee said if only 50 percent of the sand the Corps dumps there is making it to the island, the other half is being “effectively removed from the natural littoral drift system” as it accumulates.
“That means, since 1999, around 7 million cubic yards of naturally provided sands have been prevented from reaching and nourishing Dauphin Island,” Coffee wrote via email. “That represents a significant cumulative loss of beach-quality sands, which is contributing to the sand-starved nature of Dauphin Island and its observed erosion.”
While McDonald did say the sand was moving at only half the rate at which the Corps deposits it, he said it is indeed moving … just very slowly.
Asked if the proposed course change was a concession that maintenance dredging has had an adverse effect on the island, McDonald reasserted the Corps’ position that studies have shown there’s only been a “minimal effect” on the erosion of Dauphin Island from channel dredging.
He also said any change is simply the Corps “trying to do a better thing” within its required parameters of using “the least cost, most environmentally acceptable disposal method.”
“We can’t just go put [sand] on the beaches at Dauphin Island. We don’t have the authority to do that, and it exceeds the federal standard cost,” he said. “We feel like we’ve developed a revised dredge material disposal location that’s more beneficial for Dauphin Island than the current one.”
The expansion of Dauphin Island’s Beneficial Use Area is being considered apart from the environmental impact assessment, which McDonald said will ensure the Corps has adequate capacity to handle the increased volume of dredge material expanding the channel would generate.
The current model would deepen the channel five feet to a 50-foot depth throughout its 36-mile length. It would also widen a three-mile stretch by 100 feet to create a passing lane.
Congress has authorized depths of up to 55 feet, but DeLapp said that wouldn’t be “economically justifiable” in Mobile because “there’s not enough commerce to support it today.”
An expansion is projected to generate at least 7 million cubic yards of lower-quality material (predominantly clay and silt) to meet the new dimensions, and that all has to go somewhere.
McDonald said the majority would be deposited throughout the “Relic Shell Mined Area” east of Gailliard Island. The rest, he said, would be placed be offshore.
It would also mean more routine maintenance dredging — a projected increase of “5 to 15 percent” under the current proposal, per McDonald, and that’s been a concern not just for Dauphin Island property owners but also for local oystermen.
While state officials blame a number of factors for a decline in bottom-grown oysters in recent years, some in the industry itself believe routine maintenance dredging has contributed to the low yields because disturbances can suffocate oyster beds as sediment redistributes.
“There are no oysters in Alabama right now. None. All the dredging you’ve been doing and have done for at least three years has covered up everything in the bay,” Ralph Atkins, owner of Southern Fish and Oyster, said at Thursday’s meeting. “If you stopped today, it’d take 10 years to get the pH factor back in the bay to produce local oysters. This is a major problem.”
No one from the Corps responded to Atkins publicly, though representatives have previously told Lagniappe no “oyster reefs or sea grasses are being adversely affected by the dredged material disposal” in the more central parts of Mobile Bay.
However, at least two reefs in close proximity to dredging projects — one of which was conducted by the Corps — showed signs of an overburden of silt during reconnaissance dives conducted by the Alabama Department of Conservation and Natural Resources in 2016.
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