STRUCTURAL RESTORATION OF CORAL REEFS DAMAGED BY VESSEL GROUNDINGS

Kevin R. Bodge

Abstract


In 1995, a unique project was completed in which two coral reef sites in the Florida Keys were structurally restored after having sustained severe damage from the groundings of large vessels. The project, believed to be the world's first major structural restoration of a damaged reef (vs. in-kind mitigation using artificial reefs), demonstrated numerous innovative materials and marine construction techniques. Restoration focused upon the stabilization ofcoral rubble and large craters which resulted from the vessel groundings. The project's intent was to re-create a stable foundation which closely emulates the adjacent natural seabed and which would foster future recruitment of local biota. Work at one site included the mechanical transfer of coral rubble back into the craters, placement of limerock boulders atop the rubble, and back-filling the boulders' voids with carbonate sand. Work at the other site included excavation of coral rubble and the precision placement of 40 pre-cast reefreplicating armor units into the crater. The gaps between the units and along the crater's perimeter were filled with a specially-designed, non-separable underwater concrete - into which coral rubble and soft corals were impressed. Design was complicated by the sites' proximity to environmentally sensitive coral beds and shallow depths (2.5 to 11 m). During construction, semi- real-time video images of the underwater work were relayed to the Engineer's office via the Internet to augment construction review. Construction was successfully completed per the engineering plans with no consequent environmental damage amidst a very active tropical storm season.

Keywords


structure restoration; coral reef; reef; vessel grounding

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