South Beach Dune Restoration Project Overview

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South Beach Dune Restoration Project Overview

Background:
St. Lucie County has completed a non-federal project to address the severely deteriorated conditions of the South County shoreline.  Currently the development of a federal shore protection project is underway to provide for future re-nourishment of the beaches in the project area.  Funding for this one-time non-federal local beach and dune project included three funding sources; State funding at 43%, Erosion District Zone E reserve funding at 23% and Special Assessment District (property owners) funding at 34%.  After numerous meetings, workshops and public hearings, the Board approved several actions on October 2, 2012, including the award of a construction contract for this project.

Project Area (Beach and Dune):
The project encompassed approximately 3.3 miles of Atlantic Ocean coastline, from Martin County north to Normandy Beach Park, including shoreline segments designated by the State of Florida as “critically eroded” where upland development is threatened by erosion and recession of the beach-dune system.  The beach fill entailed the placement of approximately 635,000 cubic yards of beach quality sand obtained from a sand source approximately 3 miles offshore of the project area.  Additionally, approximately 280,000 plants, including a mix of sea oats, panic grass, railroad vine, and dune sunflower, were planted on the restored dune. 

This project was competitively bid to allow for the potential use of both upland and offshore sand sources.  A contract in the amount of $6,857,100 was originally awarded to the low bidder, Great Lakes Dredge and Dock Company, LLC (GLDD - Oak Brook, Illinois), for use of the offshore sand source.  Due to ongoing erosion and a change in field conditions generated by Hurricane Sandy and subsequent nor’easters additional sand was needed to construct the project design template which resulted in an increase in the original contract amount.  Some of this additional cost was offset by a special state appropriations of $250,000 associated with Hurricane Sandy storm repair.  A slight cost savings was also realized in the mobilization costs due to the concurrent construction of the adjacent Martin County Shore Protection project.  The final paid project amount was approximately $7.5 million.

The project was constructed using three different hopper dredges, Padre Island, Dodge Island, and Liberty Island.  A hopper dredge vacuums sand from the sea floor at the offshore borrow site through drag arms into the holding area of the dredge.  After filling the hopper to capacity, typically between 4,000 and 6,000 cubic yards, the dredge vessel then moves to the nearshore area.  The sand is pumped ashore by the dredge through a pipeline that discharges a sand and water slurry onto the beach.  The slurry is contained by a sand berm parallel to the beach where the sand is deposited onto the beach.  Heavy equipment such as bull-dozers and front-end loaders are then used by the Contractor to spread and grade the sand fill to construct the “template” shown in the construction plans.  GLDD began to move equipment onto the site on March 11, 2013 and began dredging on March 30, 2013.  Fill placement proceeded for the next month and was completed on April 29, 2013.  Final dressing, tilling, and installation of dune