Photo By Charles Walker | A dredge performs maintenance work in the Mobile Harbor, Mobile, Alabama, June 3,...... read more read more
**MOBILE, Ala. —**The U.S. Army Corps of Engineers (USACE), Mobile District, has fundamentally shifted its dredging operations. By moving away from ocean disposal and embracing "Beneficial Use" (BU) and Thin-Layer Placement (TLP), the Corps is keeping vital sediment within the bay system, restoring sediment-starved marshes, and optimizing maintenance costs.
Valerie Morrow, USACE Mobile District Dredge Material Program Manager, said that is exactly what the Mobile District is doing in Mobile Bay, restoring sediment to sediment-starved marshes.
"The material dredged from the federal navigation channel is natural sediment," Morrow said. "Sediment is a resource that should be managed intentionally. Thin-layer placement is an intentional placement practice that is a beneficial use of dredged material and is in alignment with the 'Expanding Beneficial Use of Dredged Material in USACE' memo dated August 28, 2023."
The Historical Challenge: Losing Ground
For years, maintaining the Mobile Harbor Navigation Project meant removing over four million cubic yards (MCY) of maintenance material from the system annually. Historically, hopper dredges hauled this sediment out to the Ocean Dredged Material Disposal Site (ODMDS) in the Gulf of Mexico.
This practice permanently removed critical sediment from the natural Mobile Bay ecosystem. Removing this much material from the natural system proved not to be the most environmentally sound method of disposal, contributing to sediment-starved coastal marshes and potentially causing long-term negative effects on the local ecology.
Forging a New Template: The Interagency Working Group
Fast forward to 2010, when Regional Sediment Management (RSM) initiatives began showing success along coastal inlets, helping the Corps and its project sponsors make more informed placement decisions. A new collaborative template was forged: bringing all stakeholders together, discussing operational needs, and using technology to think outside the box.
In 2011, this concept led to the launch of the Mobile Harbor Interagency Working Group (IWG). Meeting initially at a neutral site, the IWG brought together all parties with a valid interest in the health of Mobile Bay. Once presented with the project's history and challenges, it became obvious that no one agreed with continuing to dump over 4 MCY of material into the ocean every year.
The team actively pursued several Beneficial Use (BU) ideas authorized under WRDA 96, including:
“Beneficial use is about more than finding a place to put dredged material,” said Jason Kudulis, Director of the Mobile Bay National Estuary Program. “Through the Beneficial Use Interagency Working Group, agencies are working together to develop long-term, regional strategies that restore habitat, improve coastal resilience, and make the best possible use of this valuable resource.”
Innovative Solutions: The Thin-Layer Placement Demo The most critical breakthrough came when the team pursued a one-time demonstration ofThin-Layer Placement (TLP)using a hydraulic cutterhead dredge. The demo involved pumping 9 MCY of bay material in a thin lift—just 6 inches, not exceeding 12 inches—over the adjacent bay flats.
To answer the critical question,*"Where did the material go after placement?"*the Engineer Research and Development Center (ERDC) deployed 3D modeling, SEDFLUME, and other advanced tools. The results were highly encouraging:
A Win for Ecology and Operations
The modeling and monitoring results led to a unanimous IWG decision to support in-bay placement as an environmentally acceptable alternative to ocean disposal. OnJune 30, 2014, a permit was officially issued allowing the in-bay placement of operations and maintenance (O&M) material from the Mobile Ship Channel.
This shift represents a massive operational advantage. Utilizing TLP allows the Corps to employ cutterhead dredges rather than relying solely on a limited fleet of hopper dredges, making disposal practices more cost-effective. Placing material farther from the channel margins not only prevents sediment from washing back into the dredged areas but also promotes a much faster recovery of benthic communities.
Kudulis said MBNEP works with the USACE Mobile District to find solutions for the use of dredged material.
"The Mobile Bay National Estuary Program works closely with the U.S. Army Corps of Engineers, Mobile District, and our partners through the Beneficial Use Interagency Working Group to identify long-term opportunities for dredged material," Kudulis said. "Together, we're identifying opportunities to restore marshes and other habitats by returning valuable sediment to places where it can provide the greatest benefits."
Strategy Comparison: Old vs. New Management
In the old or historical method was ocean disposal vs. the modern method which is Beneficial Use and TLP. For the old, historical method the equipment used is Hopper Dredges, whereas the new method uses Hydraulic Cutterhead Dredges. The destination for the sediment using the old or historical method is Ocean Disposal (ODMDS in the Gulf), whereas in the new it is In-Bay Placement in (Bay Flats and Marshes). The old or historical method removes the sediment completely and starves the system of the sediment, whereas the new method mimics natural deposition, faster benthic recovery. The old system is limited to the Hopper Dredge Fleet and the new allows broader access to the cost-effective cutterhead fleet.
Ultimately, the intent of modifying these sediment management practices is to develop a placement strategy within Mobile Bay that meets the O&M needs for Mobile Harbor while firmly adhering to environmental standards. Through collaboration and innovative engineering, the USACE Mobile District is ensuring the long-term conservation of Mobile Bay's ecological resources.
“USACE Mobile District has been partnering and supporting Beneficial Use projects for decades,” Morrow said. “USACE Mobile District is actively engaged with practitioners looking for opportunities to provide sediment for beneficial use projects. USACE Mobile District is also actively involved in the Beneficial Use Interagency Working Group to support identification of future beneficial use sites within Mobile Bay.”
| Date Taken: | 07.08.2026 |
| Date Posted: | 07.08.2026 13:33 |
| Story ID: | 569557 |
| Location: | MOBILE, ALABAMA, US |
| Web Views: | 20 |
| Downloads: | 0 |
This work, Turning the Tide in Mobile Bay: USACE Restores Sediment-Starved Marshes, by Charles Walker, identified by DVIDS, must comply with the restrictions shown on https://www.dvidshub.net/about/copyright.
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