Dock & Decks

Top 10 questions about

ConcreteFloatingDocksBY ROBERT WILKES

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' n recent years, many marinas across;J the country have been installingconcrete floating docks. The questionmost marinas want answered is: What'sbehind the choice ot concrete floatingdocks? Here are the Top 10 questionsasked about concrete floating docks:

IIMany people who'veexperienced standing on a

; .. concrete floating dock say,"It feels like solid ground." Why areconcrete floating docks so stable?

Craig Funston, a structural engineerwith the engineering and design firmRed Point Structures in Bellingham,Wash., explains the science behind thedesign.

He says the perception that a persongets of standing on solid ground is "acommon reaction when anyone stepson a concrete floating dock for the firsttime." Funston says, "the modules floathigh on the water, but they are massive,and they have a wide footprint."

'Think of a floating dock as a snow-shoe," he explains. "The footprint isvery broad compared to the weight itsupports, so the water easily resists the

load. Because each module is connect-

ed to the next, it multiplies the massand footprint by the number of mod-ules, making the entire system extreme-ly stable and solid."

The strength of the "snowshoe.effect"can be seen at Port Forum, a super yachtmarina in Europe that features a concretefloating dock. Here, the yacht ownerscarry their Mini Coopers (see photobelow), on the decks of their yachts.

At Port Forum, cranes lower theautomobiles on to the finger piers with-out jeopardizing the freeboard or stabil-ity of the docks.

II...', Will concrete floating docks

..'... help me comply with. . environmentalregulations?

Let's be clear: concrete floating docksand pilings may look void of life, butthey are home to an amazing biodiversi-ty. Concrete has a high carbonate con-tent, much like natural submerged rock.Large floats and tall pilings provide anattractive surface for colonization bymany types of marine organisms.

In an environmental study of a con-crete floating marina in Florida, biol-ogists found a "meadow" of mixedalgae, barnacles, feather duster

Floating concrete docks are home to anabundance of marine life.

worms, sponges, oysters, mussels,shrimp, and crabs living on the sidesof the floats.

. The algae and other sea life helped'filter and clean the water by absorbingdissolved nutrients. This was especiallyhelpful at the location studied becausethe marina basin received storm runofffrom the land above. In most situations,sites with runoff will experience murkyor clouded water. However, the pres-ence of bi-valves or other filter feederscan help minimize the effects of stormwater runoff.

II"'..' In case of a marina fire, is" there an advantage to havingconcrete. floating docks?

The simple answer is "Yes." Once aboat is fully involved in a fire, theintense heat of burning fiberglass makesit difficult to extinguish. As firefightersnote, it's hard to locate and attack thefire's core from the outside of a boat dueto the boat's many compartments. As aresult, once the fire department arrives,it's usually not a question of saving theburning boat, but rather how to save allthe other boats in the marina.

In February 2006, the San Diego FireDepartment spoke highly about concretefloatation after a nighttime marina fire atthe Marriott Hotel Marina. In interviews

with the firefighters at the scene, theymentioned several factors related to theconcrete-float design that helped themlimit the fire to a defined area.

Concrete will not bum like wood orsag or collapse like aluminum trussstructures that can anneal in the heat ofa fire. Less obvious is the real benefit of

continuous concrete floating docks-they are a fireproof barrier againstburning liquids spreading the fire.

Second, scrambling firefightersMini Cooper automobiles are hoisted on to the docks from the mega-yachts at Port Forum,Barcelona, Spain.

20 MARINA DOCKAGE,JANUARY/FEBRUARY2007

Firefighters in San Diego appreciated thestable, non-flammable platform from whichto fight the fire.

could work from the docks because

they provided a steady platform. With70 Ibs. of equipment on their bodies,firefighters fear falling in the water,which is a real and present danger.Having a stable platform from which tofight the rire and manage high-pressurehoses is critical to the success of the

fire-fighting efforts.

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11.\. It's been said that the water. '.. around these concrete

floating docks is calm. Isthis a myth?

Without getting too far into hydrody-namics, the inside of a floating concretemarina is virtually still-i.e. calm-because most of the time the approach-ing wave "sees" the float as a solid wall.

In a properly designed marina, mostof the waves that approach the marinawill be relatively small and of shortfrequency.I That is, the time betweenone wave and the next is brief, barelyone or two seconds. The float's designgeometry and inertia dissipate or ab-sorb virtually all of the wave energyleaving the waters inside the marinacalm. The float is not a solid wall, butthe effect is nearly the same.

II.. Judging from the exterior,..'. concrete floats look as if they

have a simplistic design.What's taking place on the inside?

Stan Reimer, manager of corporatemanufacturing for Bellingham Marineof Bellingham,Wash.,has manufactureda lot of concrete floats, and nothing

1Longerfrequencywavesmay occur in windy condi-tions over long fetches.In properly designedmari-nas,theseare rare. Forexposedmarinas,additionalprotection may be required by floating-concretewave attenuators,rubble moundsor seawalls.

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The inner structures are set with great precision before the concrete is poured.

makes him more upset than people whosay they are just blocks of concrete."There's a lot of skill and precision thatgoes into making a float," Reimer says.

Reimer, who is involved with plantsworldwide such as the one in Ferndale,Wash., that is currently turning out one-piece fingers up to 70 ft. long for theShilshole Bay Marina renewal inSeattle, says working with concrete isquite complex.

"I can't get into the design becauseit's proprietary," Reimer noted, "butconcrete is actually a delicate materialto work with. It takes a very experi-enced team of workers to construct theforms and internal workings of the floatand prepare it for the pour. The rein-forcing bar and mesh, utility runs, cus-tom features, and expanded polystyrenemust be installed to exacting tolerancesand standards." ,

"In the endit's worth it," Reimer says."When those modules come togetherand form a marina, the uniformity andsymmetry of the whole is beautiful."

IISo how can a concrete

/ .. floating dock marina beconsidered flexible?

Although the concept that concrete isflexible is counterintuitive, it's true.Concrete's flexibility derives from itscomponent design. Well-designed sys-tems use three basic components: thefloat, the structural waler, and thethrough rods.

Think of Lego blocks. Working with

these three components, one can recon-figure a marina and move finger piersaround relatively easily. In many cases,the pilings don't have to move at all, orvery few of them have to be reposi-tioned.

The aIde Naples Seaport, formerlyknown "Isthe Coconut Grove Marina inNaples, Fla., is a good example.Originally built with 40- and 60-footberths, the operators saw the longerberths sell out more quickly than short-er length ones. To capitalize on thesemarket changes, the owner remodeledthe marina to create 60- and 80-foot

berths. Few piling positions werechanged, and the cost of the remodelwas one-third of what it might other-wise have been, and most importantly,the marina now has large berths for itslarge boat customers.

A flexible concrete system will alsoallow for non-opposing fingers. From adesign standpoint, this is a great bene-fit. One may have a 30 ft. berth on oneside of the main walk, and a 40 ft. berthon the other. Flexibility in configuringslips allows owners to optimize thespace in the basin and the slip mix.

II Where do the utilityruns go?

Marinas with concrete floating dockswill find their buried utilities are safer

than other style docks, just as neighbor-hoods with buried utilities are moresafe and reliable to live in. Built-in util-

ities are resistant to damage and needlittle or no maintenance.

Placing the utilities on the inside offloats can help prevent fatigue failuresfrom constant bending motion, buthere is a case where not all floatingdocks are the same. When modules areconnected by hinges, constant flexingcan occur. When the modules areunitized, as they are in a structuralwaler system" the connecting pointsflex very little.

Internal utility runs may includeelectrical power in primary and second-ary voltages, potable water, wet and dryfire lines, CATV, CAT6, fiber optics,telephone, sewer systems, natural gaslines, and even a compressed air systemfor boatyards. Whatever the operatorwants can probably be run inside thefloats.

II', ""'"'"What is design-build,anyway?

There are a number of ways to sourcea marina. However,using a design-buildprocess can be an effective means tocreate addedvalue. EverettBabbitt,pres-ident of Bellingham Marine in Belling-ham, Wash., has been involved in manydesign-buildmarinaprojects."In the end,you'll have fewer headaches,more valuefor your dollar, and an optimum facilityfor the business," Babbitt says.

A design-build contractor who incor-porates site-specific engineering anddesign recognizes that each marina isdifferent, and that there are alwayscompromises with "off-the-shelf' solu-tions. Hiring a design-build contractorcan help ensure that the marina isdesigned with the geology, topography,environment, and market in mind.

An experienced design-builder canbring a wealth of talent and expertise tothe project and can help deliver a mari-na that is designed to last, but is stillcost effective. Design builders offermany services, including a thoroughexamination of how to optimize useof the available basin and how toensure a calm and safe harbor for

guests. A knowledgeable design buildercan also anticipate slip size, amenityrequirements, and help each ownerachieve a unique style and character forits projects.

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A main walk in Sun Harbor Marina, San

Diego, Calif.

II; Docks are docks. They alllook the same, right?

Wrong! The new trend in marina con-struction is customization and style. For

example, the owner of Sun HarborMarina in San Diego wanted a cus-tomized deck surface to go with the soft-er curves she had designed for buildingsand walkways. She got this and more.(See the cover story on Sun Harbor inMarina Dock Age, Sept/Oct. 2006).

The owners of Salpare Bay Marina inPortland, Ore. wanted to create a moretraditional look on the decks of their

floats, but still maintain the durabilityof concrete. The manufacturer was able

to stamp in "cobblestones" and create amarina like no other.

II/"""," You still have to maintain

", ' concrete floating docks,right?

Not really! They do require somemaintenance, but it is far less than othermaterials. Randy Short has been in thebusiness 30 years, and his company,Almar Management, owns or manages15 marinas. Short is convinced of thedurability of concrete flotation. He hastwo docks built near one another at oneof his marinas.One dockwasbuilt 20

A traditional decking style at the Salpare BayMarina in Portland, Ore.

The 12th Street Marina in Everett, Wash.,incorporates curved finger ends, as shown inthis dock prior to installation.

years ago, and the other is only twoyears old. "You can't tell the differ-ence," he says.

Short likens the change in dockmaintenance to that on automobiles."Back in the 1950s and 1960s, onecould almost see the paint oxidize infront of their eyes. Similarly, the dis-tributor, rotor, and points would go outof timing every few weeks, and theplugs would have to be cleaned andgapped. Today, one only needs tochange plugs every 100,000 miles.That's what these new dock systemsare like compared to the old wooddocks we used to have." -J;.

Robert Wilkes writes about the marina

industry from his home in Bellevue,Wash., and is a frequent contributorto Marina DockAge. He can bereached by phone: 425/451-8005 orvia e-mail: rcw@wilkescreative.com.

DID YOU KNOW?

A marina in China selectsPremier Floats for dock support

A new marina developmentin Dalian,China, features docks supported byPremier Materials. As part of a largecommercial development, the Star-bay Yacht Club opened in Fall 2006.Premier's floats not only support the

docks, they alsohelp the environment.While traditional,floats were made ofblocks of foam that flaked .into thewater as they aged. Premier's productsare fully encased in plastic. Thismeans that even as the years add up,the foam is never exposed to water, sothere's never any danger to the waterand its wildlife.