Beneficial Use of Dredged Material in the Gulf
Historic Egmont Key will soon receive critical sand thanks to maintenance on the Tampa Harbor channel. The small island has experienced large-scale erosion and structural damage on its western shoreline.
The U.S. Army Corps of Engineers, Jacksonville District awarded a $13.4 million contract to Great Lakes Dredge & Dock Company of Oak Brook, Ill., to perform maintenance dredging of the Tampa Harbor Egmont and Mullet Key channel cuts. The project plans to beneficially place dredged sand and to install geotextile tubes on Egmont Key to help stabilize the beach and protect historic structures.
The maintenance will remove up to 875,000 cubic yards of shoaled sand along 17 miles of channel to improve navigation safety. The Corps anticipates operations will start in late October or early November and continue for approximately four months.
“Sand placement will start at the north end of Egmont Key which is currently the most severely eroded portion of the island,” said Andy Cummings, project engineer. “From there sand placement and tilling will progress southward along the western shoreline of the island.”
Throughout operations, channel maintenance work will include turbidity monitoring to help ensure water quality standards are met and endangered species observers to help protect marine wildlife. If sea turtles are numerous in the navigation channel, they may be relocated through the use of open-net trawling. The island is home to gopher tortoises, nesting sea turtles, nesting shorebirds and wintering migratory birds.
Erosion on the western shoreline has created a two- to three-foot escarpment to form and caused numerous palm trees to fall into the Gulf of Mexico. As a result of the erosion, currently there’s almost no beach on the west side of the island for sea turtles to nest.
“Placing sand there in the early part of the winter season provides time for wave action on the beach to naturally sort the sand and silt,” said Aubree Hershorin, Ph.D., project biologist. “This is important, because it ensures the beach is as suitable as possible for nesting sea turtles that will begin using the area in April.”
Historic structures that are in peril include portions of Fort Dade, an 1899 coastal defense system that was completed in 1906. The island is also home to a lighthouse built in 1858 and still in use today. A number of state, federal and private entities actually own and manage Egmont Key, including the U.S. Fish and Wildlife Service, the Florida Park Service, the U.S. Coast Guard, and the Tampa Bay Pilots.
Although the dredged sand is not an exact match to that found on Egmont Key, the beneficial placement is supported by the Corps, NOAA Fisheries, Florida Department of Environmental Protection and local agencies.
“Reusing dredge sand from the local area will benefit the ecosystem surrounding Egmont Key in many ways,” said Mark Sramek, habitat conservation biologist for NOAA Fisheries. “It will protect some of Tampa Bay’s most important living marine resources, as well as provide shoreline stabilization to protect the island’s historic and cultural resources.”
“We all recognized that if nothing is done, storms and wave action will continue eroding the shoreline and eventually destroy the historic structures,” said project manager Milan Mora. “It’s only a band aid, but we’d like to continue to beneficially use the dredged sand to help preserve Egmont’s cultural and natural environment as long as possible for future generations.”
Press Release, September 15, 2014