Man's activities and natural disasters have led to a reductions in our natural reef systems. Recreationally, growth in sports fishing, scuba diving, and boating has increased the pressures on these systems. Commercially, our seafood industry is dependent on developing the ocean to enable ever larger, yet sustainable, harvests. The loss of our natural systems, coupled with increased use, COMPELS US TO DO EVERYTHING WE CAN TO SAVE NATURAL REEFS. Even so, the natural reefs cannot rebuild themselves fast enough to meet human demands. Long lasting artificial reefs are useful tools for restoring our reef systems to a natural and productive balance. The key to making the decision to build a reef is having a properly defined set of project goals. Once these goals are established, it is possible to design a specific artificial reef that will accomplish that particular set of goals. It's not a simple process but the Reef Ball Foundation has completed a "Step by Step Guide for Reef Rehabilitation for Grassroots Organization" that will help you decide if designed artificial reefs are right for your project.
What's Involved & How Are They Made?
Reef Ballsare made by pouring concrete into a fiberglass mold (shown) containing a central Polyform buoy surrounded by various sized inflatable balls to make holes. There are over a dozen different standard mold sizes and custom sizes are possible. Molds obtained from the Reef Ball Foundation are generally supplied with spare parts, tool kits, starting concrete additive supplies, and training. Sometimes, additional items such as coral propagation kits are added. Usually, clients only need to supply some plywood to build the base, a source of compressed air, and a fresh water supply. Any type of concrete can generally be used, including end-of-day waste, but additives such as microsilica and a high range water reducer are needed to give the Reef Ballshigh strength and to make the concrete suitable for marine life growth.
We provides clients with customer concrete specifications for their particular biological use and if admixtures are not available locally then we can supply the additives. Building an artificial reef usually requires artificial reef permits or access to use a permitted area. The Reef Ball Group can help clients get or secure permission to use a permit. A training manual on how to use the molds and how to deploy the modules is also included with the mold systems, but most clients host a couple of certified Reef Ball trainers for about a week to get set up and casting Reef Balls efficiently and safely. We can provide additional specific on-site training such as coral propagation, coral planting, anchoring, bottom surveying, site assessment, monitoring or any other aspect involving artificial reef projects to make sure your project goes smoothly. Special programs are available to subsidize university research projects and other worthy projects through the Reef Ball Foundation. Reef Ball Foundation also encourages participation in projects by private organizations as we match projects needing sponsorship with companies that want to help the environment while gaining excellent press exposure.
Reef Balls are cast around an extremely durable Polyform bladder which are supplied with molds. This bladder can be left in the unit to provide flotation so the Reef Ball can be towed behind any size boat. Once at the site, the bladder is deflated and removed. When divers are used, the unit can be placed precisely on the sea floor with a controlled descent, making repairs to damaged reefs possible without endangering natural reefs. Floating deployments are useful in small projects when towing distances are less than 5-10 miles. This is an especially important feature in developing countries were access to barges and lift equipment can be limited or expensive. Multiple units can be towed behind a single boat. Seas should be 3-4 feet or less. Recommended towing speed is 2-3 knots, but techniques are available to attain 4-5 knots for long hauls. For most larger projects, the units can be deployed by barge without divers and we have specialized tools available to make this easier such as a Wanger automatic release hook.. Divers are required when deploying on any site that contains live corals within 300 meters of the intended location.
Whirlpooling Shape of Side Holes
[Wind tunnel tests at FIT showing effect of holes on current flow]
Natural reefs are variable in size, shape and hole density. Artificial reefs function better when they mimic nature. The balls which create holes are inflated to different pressures to vary hole sizes. You can move the hole creating balls around in your mold to create holes exactly where you want them. Interconnected holes are possible by inflating the balls until they touch. Most holes are designed so they create whirlpools around the Reef Balls helping to nourish marine life that is attached to the reef. The way the balls are squeezed against the molds during casting makes the inside and outside of the holes smaller than the interior cavity created and that creates the whirlpool effect. Every Reef Ball molds comes with a set of attachment adapter plugs that fit the mold shells and create specific sized indentions onto the surfaces of the Reef Balls for purposes of attaching items once the Reef Ball has been deployed. The attached items can include standardized coral fragment disks fostering live coral growth, tags for the purposes of scientific research or plaques such as signage for underwater snorkeling trails. Since hole sizes and placement can be modified, every Reef Ball will have a unique look....creating the visual diversity commonly associated with reefs. Additional casting techniques are taught by our trainers so users can customize to fit any need such as specific hole shapes for octopus nesting, lobster shelter, blenny hideouts, or long spiny sea urchin day shelter. The void spaces in the interior of the Reef Balls can also be customized, such as filling partially with rocks or conch shells to modify fish populations such as shifting the habitat to favor juvenile fish or to increase biomass production.
[The Above Close Up Shows Aggregate Exposed By Using Sugar Water On Molds]
A variety of surface textures that enhance the settlement of marine life are available. A popular surface texture is made by spraying sugar water onto the surfaces of the mold before casting. After the cement mixture hardens, the mold panels are removed and the last 1/2 inch of concrete remains unhardened. A rough stony surface is exposed by rinsing the module with a garden hose. All surfaces are enhanced by the use of an air entrainment admixture. This non-toxic, soapy-like additive creates tiny pockets in the concrete which pits the surface of the Reef Balls. These pits offer tiny marine organisms (such as larval corals) a place to easily attach themselves.
[This is a Bay Ball(tm) which weighs 325 pounds and is 3 feet wide and 2 1/2 feet high. Three different surface textures were applied (rubber mat, surface retarder, and air entrainment).]
The concrete used to make Reef Balls features W.R. Grace's Force 10,000 micro silica to create a super high strength, abrasion resistant, concrete that has a pH similar to natural sea water. This is unlike regular concrete which has a surface pH as high as 12. This high pH (the sea has a natural pH of 8.3) can inhibit the settlement and growth of many species of marine life including some larval corals. Micro silica gives Reef Balls an expected life of 500 or more years.
Other admixrtures include a high range water reducer, and microfibers. Reef Balls are made without using any iron rebar that would cause cement to eventually degrade in sea water.
Stability & Longevity
Reef Balls are designed so that over half of the weight is in the bottom near the sea floor. All sizes of Reef Balls have withstood, without movement, heavy tropical storms in as little as 20 feet of water without anchors. Reef Balls are stable because the opening in the top of the unit breaks up the lifting force of the hydrofoil effect common to dome shapes. Side holes are wider near the center of the walls and narrow near the units surface. This feature creates miniature vortexes which further reduce lifting forces and bring rich nutrients to life on the reef. Reef Balls can be cast up to double the standard weight to accommodate high energy zones, or they can be cast at 75% of the standard weight to save concrete for bay, deep or protected water locations. Our staff will help you determine the best way to insure stability.
We provide mold systems that have been used in thousands of work sites and are simple, efficient and easy to use. Molds pack down for shipping on simple pallets and will fit easily into a pick-up truck. We've even carried many of the smaller sized molds as checked luggage on an airplane.
There are 9 different standard sizes ranging from as small as a basketball to as large as a car 8 feet high.
Left to Right: Oyster, Lo-Pro, Mini-Bay, Bay, Pallet, Ultra, Super, Goliath, Goliath w/Booster Ring.
Largest Size ==>
We also offer Model sized reef balls for displays and they come in Large (6 inch diameter), Medium (4 inch diameter) and Small (3 inch diameter)
We give different sized Reef Balls names in an effort to differentiate them. If you work with the molds on a project you will learn the names by heart, but don't fret if you just emails you want the 4 foot tall size we'll help you figure it out. For a quick primer, use this sizing chart..
Goliath Booster Ring
6 feet, 6 inches
4,000-6,000 lbs. (1,818-2,727 kg.)b
1.3 yard3 (1.19 m3)
6 feet (1.83 m)
5 feet (1.52 m)
4,000-6,000 lbs. (1,818-2,727 kg.)
1.3 yard3 (1.19 m3)
230 ft2 (21.4 m2)
6 feet (1.83 m)
4.5 feet (1.37 m)
4,000-6,000 lbs (1,818-2,727 kg.)
1.3 yard3 (1.19 m3)
190 ft2 (17.6 m2)
less than 4
50 lb. bags
less than 2
50 lb. bags
less than 1
50 lb. bag
Sizes in red are typically only used for submerged breakwater applications. Other sizes are more typical for standard artificial reef projects.
When Reef Balls are used on a sandy bottom in depths of 10 meters or more or in storm protected waters, anchors are typically not required. However, shallow water applications, areas of flat hard bottom, and high energy zones often need to consider anchoring options. There were a variety of anchoring methods used, and in many cases, combinations of the methods shown below were used. Each method has been tested in the field for anchoring ability and engineering calculations are needed to determine which anchoring combination would be required for stability. Dr. Lee Harris performs these calculations for many of our clients.
For 'Normal' bottom (rebar could be driven to two feet by a sledge hammer with normal effort and there was a healthy biological seagrass root system for resistance to settlement) Anchoring cones were used. The four anchoring cones on the above Goliath Sized Reef Ball were cast monolithically when the Reef Ball was made and are designed to slowly settle over a period of months into the sea grass bed root system. After settlement, the cones will prevent lateral movement of the Reef Ball during storms. Although somewhat difficult to see in this photo but clearly visible in the photo below, between each cone has a 1.5 inch pad that is designed to keep the module above the root systems to maintain the designed height since the roots are slightly below the seabed.
In areas where the bottom was 'hard packed' (so hard that it was difficult for rebar had to be driven in by a sledge hammer) pre-cast spikes with #5 fiberglass re-enforcement were cast into the Reef Ball bottoms. Engineering pressure tests indicated the size of the spikes needed to be self penetrating by the weight of the units when installed. These spikes provide resistance to lateral movement. The outside and inside rows of Reef Balls had solid bottoms (shown above) and were 25-50% heavier than the hollow bottom units in the center rows. This was done to maximize stability.
Above is a picture of the base Reef Balls are cast upon showing several of the adaptations made for the Maiden Island project.
Battered Anchoring Pilings
In areas where the sand was 'soft' (so soft that rebar could be put to a two foot depth using hand pressure only) battered pilings were used. Three piles in a 'tripod' pattern were jetted in until they reached the hard bottom below the soft sand. During installation, the crews first jet to the bottom with a 4 inch pipe to determine the exact depth. Next they would insert a pile of the appropriate length and use the smaller 1/2 inch PVC pipe precast into the pile to jet it to the bottom. Three pieces of #3 fiberglass rebar were added to each precast piling for strength. Pilings were made in ranging from 8 feet to 3 feet in one foot increments.
Anchoring With Battered Fiberglass Rebar
In areas where there was hard bottom, or for smaller sized Reef Balls located inside of the breakwater in the wave protected area, 3-4 pieces of battered #5 fiberglass rebar where drilled or driven into the seabed. Holes for both the fiberglass rebar and the piling anchoring system were cast into every Reef Ball made to provide multiple anchoring options.
Anchoring With Rock 'Cones'
'Layer Cake' Reef Balls were cast upside down, so instead of using anchoring cones, we selected natural rocks about the size and shape of the anchoring cones. The concept is similar, the units settle by themselves over time or they are assisted by jet pump which provides additional stability from lateral movement and overturning.
Anchoring With Articulating Concrete Slabs
The Miami reefball submerged breakwater project included articulating concrete slabs and below are links to the AutoCAD drawings of the design.