Okaloosa County BOCC — June 2, 2015 — Okaloosa Co ABF Feasibility Study C2014-042 — reading text

an average of 43 months while windward buoys survive an average of 25 months — a 40% reduction in expected longevity. One would anticipate that the periodic storm exposure with winds exceeding 40 mph in the GOM would further reduce buoy longevity. As such, the proposed program should implement design changes to account for the rougher conditions. The Hawaii program found that the single spherical spar buoy design (Figure 5) provided the best performance while minimizing losses. Figure 5 shows a typical Hawaii FAD surface buoy system. The system consists of a 200-lb (400 kg) 4.8-ft diameter steel spherical spar buoy with 3,000 lbs (1,400 kg) of positive displacement. The 3.5-ft mast atop the float holds a light system and 7-ft pipe welded below the float provides a counterweight to maintain the buoy upright. About 100 ft of 13 mm chain attaches the buoy to the rope mooring system. Sections of negatively buoyant and positively buoyant nylon rope provide an inverse catenary or “slack” (“S” shape) mooring system. The nylon rope and mooring system provide the slack needed to absorb cyclic loading on the mooring as the surface buoy heaves in the waves and ensures that the lower part of the mooring will not drag on the ocean bottom as might happen with a conventional catenary system. Three 1,700-lb concrete block anchors attached to 80 ft of 13 mm chain deployed in a tripod configuration provides the anchor system for the buoy. 7 Figure 5. Single Spherical Spar Buoy Design (figure provided by HIMB, SOEST, University of Hawaii) This buoy and anchor system typically costs an average of $8,000 – $9,000 to build and install offshore Hawaii with the nylon rope being the highest single component cost at approximately $2 per foot ($2,000 – $20,000 for 700 – 10,000 ft). Ship time for installation ranges from $7,000 – $8,000 per day. Simultaneous installation of multiple buoys allows significant cost savings resulting in the average cost of $8,000 – $9,000 to build and install. Notably, Hawaii buoy installation sites generally lay 5 – 20 miles from land, which reduces ship travel time for the installation. In comparison, a relatively small (3m) discus buoy (similar to the discus buoys used by NOAA to mount oceanographic instrumentation in the area of interest) may cost approximately $20,000 for just the buoy. The mooring system may cost between $10,000 – $50,000 depending on the water depth (200m – 800m) and installation in the proposed project area may cost approximately $20,000 – $40,000 depending on the total number of buoys proposed and the distance offshore. The increased mooring and installation costs primarily result from the larger buoy(s) imparting increased forces on the mooring system and requiring larger or more specialized vessels for deployment. From the information above, the water depth appears to be the greatest controlling factor for both the discus and spar buoy structures. Based on the research cited, the typical failure mechanisms of the Hawaii buoy system result from near-surface shackle connections (i.e., failure due to the rapid movements and friction damage near the surface) or rope breakage. Rope breakage is believed to be caused by cyclical loading resulting from 8 increased wave and currents, barnacle growth, and/or shark or other sharp-tooth fish biting the ropes. From conversations with Hawaii researchers, vessels mooring to the buoy system also decrease the structure life by increasing the loading on the mooring line and connection hardware. Notably, a correlation between depth and longevity was not apparent from the Hawaii FAD system. Similarly, typical failure mechanisms of NOAA buoys in the GOM generally result from severing of the synthetic line either through deliberate or accidental vandalism. In fact, from discussions with the National Data Buoy Center (NDBC) staff, they have begun installing camera systems on the frequently damaged buoys to deter vessels from mooring to the buoy. Connection hardware failure is generally less of a concern because the buoys and/or mooring systems are typically replaced every 3 – 5 years. Equipping the surface buoy with a GPS tracking system will allow easy relocation of the equipment should the connection system fail. However, the anchoring system can only be reused if it is retrieved from the bottom using specialized surface vessels equipped with cranes and underwater autonomous vehicles. Given the proposed water depth of 1,000 ft or greater, the cost of retrieving the anchoring system will likely be cost prohibitive. A small-scale (1 – 3 buoys) installation in the GOM (~40 – 60 miles to the site) with a more robust buoy system designed to survive moderate GOM storms may cost $20,000 – $30,000 per buoy (to build and install). This estimate is primarily based on a preliminary scaled-up version of the Hawaii system (larger anchors, chain, and rope) with a large diameter, round (spar) buoy. The availability of large-scale commercial vessels (capable of performing multiple deployments in a single trip) may greatly affect the cost estimate. Designing the structure to provide a platform for scientific instrumentation or vessel mooring (larger discus buoy and mooring system) presents additional design challenges. Given the distance offshore, the vessels mooring to the structure will likely be 50+ ft in length and the County will have little to no control over the number or size of vessels mooring to the structure. Such vessels may also attempt to anchor to the structure during increased wave/current events exponentially increasing the loading on the structure and connection hardware. Vessels moored to the structure also pose increased damage potential to any equipment that may be mounted on the surface buoy (e.g., solar panels, navigation lights, scientific/environmental monitoring equipment, etc.). Designing the structure to withstand the potential loading cases associated with vessel mooring will greatly increase the structure cost and increase the potential for structure failure (reduced structure life). The increased damage potential with a mooring structure will also likely require additional monitoring and buoy inspections, increasing the maintenance costs of the structure(s). Comparing the relatively simplistic, low-cost Hawaii buoy system with typical (higher-cost) NOAA buoys, the County should first install a small-scale buoy network similar to the Hawaii system. The County can make design modifications to future deployments based on 1 – 2 years of monitoring data from the original system. Further, because deep-water buoy systems are prone to failure, the County should consider the purchase of a buoy system (buoy, mooring, and anchor) designed as a unit. This may provide the greatest amount of confidence in optimal buoy lifespan. 9 5.0 BUOY LOCATIONS Given the scope of this preliminary study, we do not propose specific locations for a proposed buoy system. However, we provide the following items for consideration when planning the proposed buoy network. • Target Fish Species — Figures 2 and 3 provide essential fish habitat maps for two primary target species (billfish and tuna). Additionally, available literature indicates these species prefer variations in water temperature and depth that typically occur along and within the De Soto Canyon. • Water Depth — based on information presented in the previous section, the depth of water will likely greatly affect the initial material costs. • Distance Offshore — the County should consider the distance offshore of the buoy system, specifically for proposed use (e.g., recreational fishing), installation and maintenance costs, local preference, etc. • Bureau of Ocean Energy Management (BOEM) lease areas — as discussed below, placing the buoys in offshore federal waters will likely require a permit and/or consent of use agreement from BOEM. If the proposed buoy area is already leased, obtaining additional use agreements from the BOEM leasee may present additional difficulties for installation and maintenance of the system. However, relatively few active leases exist in the area of interest for placing buoys. • Buoy spacing — technical literature suggests 4 – 8-mile spacing between buoys in the Hawaiian system has been successful for effective fish attraction. Some research (reported in Dempster and Kingsford, 2003) indicates that fish orient to FADs spaced up to 18 km (approx. 12 miles) apart. Tuna may orient to anchored buoys from a distance of 10 km (Leroy et al., 2013). • Additional uses — the County should also consider utilizing the buoys (or a single buoy) as a platform for oceanographic or ecological monitoring equipment. Utilizing the buoy(s) as a research platform may reduce the initial and maintenance costs through research partnerships; however, including this equipment may also increase the overall cost of the buoy and mooring structures (i.e., larger buoy and anchoring system). Much of the deeper GOM bottom has been leased to members of the energy industry for oil, gas, and other mineral exploration and extraction. BOEM manages these leases and regulates mineral resources in Federal waters. Many active leases exist in the northern Gulf of Mexico, but relatively few lie within the project area of interest and should be easily avoidable (Figure 6). Regardless, the County will still likely be required to coordinate with BOEM regarding the installation of the buoy system. Considering only the target fish species and water depth, the County should consider placing buoys near the northern tip of the De Soto Canyon and atop the West Florida Shelf along the eastern edge of the De Soto Canyon. 10  90°0'0"W 89°0'0"W 88°0'0"W 87°0'0"W 86°0'0"W 85°0'0"W 84°0'0"W 0 20 40 60 80 One Inch = 40 Nautical Miles ! EAST PASS 30°0'0"N 30°0'0"N OKALOOSA COUNTY, FLORIDA