Cape Sable Dam Restoration
In collaboration with the National Park Service, HDR recently provided full-time onsite construction management/inspection services for the Cape Sable dam restoration project, which replaced dams on the East Cape and Homestead Canals in Everglades National Park.
The Cape Sable project was necessitated by two major issues: failed structures that created hazardous conditions for the boating public by allowing illegal entry of motor boats into the wilderness, and twice-daily intrusion of salt water into the interior marshes of Cape Sable, resulting in adverse impacts on the native habitat for the American Crocodile.
HDR oversaw the performance of the project general contractor throughout the project. The general contractor replaced two sheet-pile plugs with earth-filled sheet pile structures and constructed floating docks, ramps and concrete walkways to permit visitors to portage canoes across the dams to wilderness areas. The eroded condition of the existing plugs created a safety hazard for the public, allowing swift tidal currents to flow through the breeches. High tides flowed over the steel sheet piling, hiding it from boaters on the water. The new structures, easily visible to visitors, provide a place to dock boats, and portage canoes and kayaks.
The Cape Sable canals cut through a low ridge of marl soil along the edge of the cape, historically retaining freshwater, which enabled fresh water to drain from interior wetlands and salt water from the Gulf of Mexico to penetrate inland. The resulting salt water intrusion accelerated the change from freshwater wetlands to a more saltwater estuary ecosystem. Higher salinity in interior marshes reduced juvenile crocodile habitat suitability and lowered the productivity of forage fishes. This was affecting the ability for wading birds and other fauna to forage efficiently. Replacing plugs on the East Cape and Homestead canals has lowered salinity in these marshes and reduced the impacts of saltwater intrusion.