The Service's field investigations and recommendations addressed potential upstream impacts of saltwater intrusion to fish and wildlife resources if the existing structure fails.  An analysis using GIS supplemented with ground-truthing suggests habitat potentially affected by saltwater intrusion within the project area includes approximately 32,655 acres of predominately fresh to intermediate marsh, and 3,530 acres of forested wetlands.  The marshes and forests are variously dominated by Taxodium distichum (bald cypress), Acer rubrum var.drummondii (Drummond's red-maple), Salix nigra (black willow), Quercus phellos (willow oak), Q. lyrata (overcup oak), Fraxinus caroliniana (water ash), and Pelltandra virginica (virginia arrowarum), Scirpus californicus (California bulrush), S. americanus (Olney bulrush), Spartina patens (marsh-hay cord-grass), Phragmites autralis (southern reed), Sagittaria lancifolia (lance-leaf arrowhead, Zizaniopsis miliacea (southern wildrice), Typha latifolia (cattail), and Sesbania spp. (rattlebush).

Stands of submerged aquatic macrophytes are frequent in the study area, and can include Cabomba caroliniana (carolina fanwort), Ceratophyllum demersum (coon's-tail hornwort), Potamogeton nodosus (long-leaf pondweed), and Utricularia spp. (bladderworts). These habitats provide critical resources for fish and wildlife, such as migratory songbirds, wintering and migrating waterfowl and other water birds, amphibians, reptiles, and commercially important aquatic species including blue crab (Callinectus sapidus) and white shrimp.