Resilient marina renovations lead to coral relocation

by Marie Guyer and Anne Shoffner
Fisher Island, a private barrier island community south of Miami Beach, Florida, is renovating its 1980s resident marina with sea level rise resilience and the modern boater in mind. Remarkably, the artificial and highly active marina basin supported a thriving stony coral community, creating an environmental obstacle when upgrading from a fixed to floating dock system.

Outgrowing the existing 86-slip marina and approaching the end of the useful life of the timber fixed docks, an overhaul was due at Fisher Island Club’s resident marina. With this renovation, Fisher Island Club seized the opportunity to safeguard its marina investment by incorporating resilient docking features.
In South Florida, the estimated service life for a marina is 30 to 40 years, during which time water levels are projected to change significantly due to sea level rise. For fixed dock configurations, water level increases trigger premature replacement or repairs, creating an additional expense and an unwelcome interruption in marina operations. To circumvent these future water level challenges, Fisher Island Club chose a floating dock system. Floating docks inherently adapt to changes in water levels, as well as storm surge, offering a level of resilience to the projected sea level rise. Bellingham Marine was selected as the general contractor and floating dock manufacturer for the project.
Optimising berth configuration
The original marina satisfied the market when built in the 1980s, with most slips under 60ft (18m) in length, but the new configuration has been designed for the modern boater, with 80% of slips in the 60 to 70ft (18 to 21m) range and 20% in the 90 to 120ft (27 to 37m) range. Efficient use of the existing basin also allowed for 13 new slips, for a total of 99-slips.
Basin modifications
The change from fixed docks to floating docks, the increase in vessel draft, and the creation of new slips necessitated dredging and removal of previously placed rock riprap. The existing rock riprap, approximately 1 cubic yard per linear foot of seawall, was directly in the proposed footprint of the 8ft (2.4m) wide marginal floating dock and lined the 2,200ft (671m) perimeter of the basin seawall. The riprap consisted of rock boulders approximately 2 to 6ft (0.6 to 1.8m) in diameter and was installed with the original marina.
Through discussions with environmental agencies and review of historical information, it was determined the rock riprap was originally required by the County as a means of creating nearshore habitat as well as providing toe scour protection for the seawall. Fortunately, the State and Federal government allowed for its replacement under a permit exemption without mitigation requirements. The replacement toe scour protection measures have a lower profile to accommodate the rise and fall of the floating docks with the tide. The engineering design and permitting for the marina basin renovations was provided by Cummins Cederberg.
Thriving coral colonies
As part of applying for environmental permits for marina construction in Florida, in-water surveys were performed by the Cummins Cederberg marine science team to document any protected marine organisms, such as stony coral colonies or seagrass in the construction area. Within the Fisher Island Club marina, marine scientists identified several hundred healthy ‘urban’ stony coral colonies, ranging from 6in to 3ft (15cm to 1m), growing on the rock riprap below the fixed docks.
These ‘urban’ corals are the focus of many researchers, who are trying to determine how and why the corals, growing in marina basins, large ports and industrial areas, are doing so well. The stony corals found in the resident marina were particularly hardy and well-adapted to their environment, which was remarkable considering the existing fixed docks decrease light penetration and the vessel activity increases water turbidity, both of which can be harmful to coral colonies.
Coral relocation
To allow for rock riprap removal, the local permits required all stony corals greater than 6in (15cm) be detached from the rock riprap and transplanted to a suitable off-site location. To relocate the corals, it was first necessary to find a nearby recipient site with appropriate water depth, clarity and substrate with enough available open space to reattach the stony corals from the marina basin. A site with relatively shallow water, located east of the island and immediately south of the entrance to Port of Miami, was selected as the most suitable location to transplant the colonies.
Following acquisition of the appropriate authorisations and permits, stony corals were harvested from the riprap substrate and relocated to the preferred coral recipient site. Coral colonies were assessed for size, overall health and growth form. Stony corals presenting signs of disease, overgrowth by an invasive boring sponge species or heavy algae, or with low potential for survival (e.g. breaking apart into very small fragments) were not removed.
Boulder relocation obstacles
Several large colonies of stony corals ranging from 2 to 3ft (0.6 to 1m) in width were unable to be successfully removed from the rock riprap due to their growth form (vertically on the riprap) and fragility. For those specimens, it was determined the entire “coral boulder” would need to be moved. This unexpected setback was overcome through coordination between the Cummins Cederberg environmental science team and the marine contractor selected for the dredging and riprap, Kearn’s Construction Company, who faced the challenge of carefully relocating massively sized boulders using heavy equipment and support divers without damaging the coral.
With each coral boulder tagged and identified by marine scientists, the Kearns Construction team carefully lifted the entire coral boulder out of the marina basin with heavy duty slings secured by commercial divers and a long-arm excavator.
“Working hand in hand to coordinate the coral boulder relocation was crucial for the success of the corals,” says Kearns Construction operations director, Brock Sullivan. “The engineer, environmental science team, and us (the contractor) had to be in sync to make sure there was no delay to the marina renovation schedule, and more importantly no harm to the coral colonies.”
The coral boulders were placed on a construction barge and transported within a short period of time to a designated area on a breakwater outside the marina basin containing existing riprap and naturally occurring corals. The time on barge for these coral boulders was minimised to reduce long-term exposure to ambient air and the potential for the living coral colonies to dessicate or be exposed to harmful direct UV radiation.
Final marina construction
Over 450 coral colonies were relocated from boulders below the fixed docks in the marina basin. Results from a six-month coral monitoring programme required by the County permit documented a success rate of over 95%, meaning almost all the relocated stony corals remained firmly attached to the seabed, were free from coral disease and were doing well in their new environment.
Notably, record high water temperatures during summer 2023 led to coral bleaching events throughout South Florida, and the relocated ‘urban’ corals appeared to fare better than neighbouring natural corals, as they were likely conditioned to unfavourable environments from living in an active marina basin.
When moving from a fixed to a floating dock system, challenges are to be expected. Through coordinated efforts with the environmental, regulatory, engineer and contractor team, we were able to resolve the basin renovations including coral relocation and permitting tasks related to the rock removal and dredging. To complement the engineering team and contractor, having an experienced team of environmental scientists and regulatory experts played a crucial role in providing Fisher Island Club with its resilient marina updates.
Vessels have started to move back into the completed sections of the new marina, offering partial marina access to residents. Construction is expected to conclude in early 2024.