Floating Breakwater : Cost?

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This topic contains 11 replies, has 9 voices, and was last updated by  clarkd 4 years, 2 months ago.

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• #1012

Anonymous

Hey all, does anyone have some idea of the cost structure behind floating breakwaters? I was looking around but couldn’t seem to find any decent estimates… Ideally some sort of formula that tells you the cost per meter of a breakwater with an effectiveness of [x] would be great!

The only examples of floating breakwaters I found with a quick google search were http://www.whisprwave.com/floating.htm and http://www.wavebraakker.com/floating-breakwater.htm but I didn’t see any easy price estimates on either site. I also these examples would work in a large-scale implementation in the open ocean =

So yeah, just seeing if anyone else has come across the info before I delve any further

#7102

vincecate
Participant

If you are interested in wavebreaks here is some stuff I have:

http://www.floatingislands.com (go down to wavebreak section)

The “Defender” wavebreak at the bottom of this page seems very interesting too:

“For comparison, a simple caisson would require a mass of 50 Tons per meter for a 5-second wave; our design would require 15 Tons per meter for .3 transmission co-efficiency. We believe the costs for the IMF “DEFENDER” concept would be as low as 50% of the simple caisson model.”

I think some google searching could give you an estimate of the cost of concrete structures including steel, forming, and concrete. So maybe total cost is \$400/ton (just guess) then with 15 tons per meter you can estimate a cost.

I think if you mostly stopped 5 second waves and had the floating harbor rising and falling with longer period waves that boats inside could be fine.

– Vince

#7103

DM8954
Participant

After looking around the rest of their site, I’m surprised by the versatility of IMF’s designs. Many of them are designed for somewhat sheltered waters and even the wave breaks don’t seem to be meant specifically for the open ocean but I imagine that with a little beefing up, they might work as a seasteading concept.

I bet that they might even be willing to partner up with us under the right conditions. For instance, we come up with a few design concepts (including lots of pretty pictures), which they could add to their Floating Concepts page and, in return, they give us a quick run-down for the potential costs involved. We might still find that it’s not quite cost effective enough in the short term but at least we’d have some much better information on the subject.

I imagine that it might be beneficial to employ multiple wave-breaks to help with the various wave types and sizes on the open ocean. I’d also expect to require structures that are twice as deep (perhaps, even, as a minimum) for open ocean applications. Finding the right combination or configuration likely wouldn’t be within the scope of such a partnership, initially. However, knowing the price points for multiple shapes and sizes of wavebreaks, docks/foundations, and connections/joints between units would go a long way in enabling us to further experiment with new designs with greater confidence and understanding of the materials and processes involved.

#7104

OCEANOPOLIS
Participant
#8579

billswift
Participant

One idea I had for a floating breakwater is to suspend netting supported by occasional floats horizontally around a seastead as a substrate for mangorves to grow on. Their roots could grow throught the netting to hold them in position as they normally grow on sand or mudflats. There would need to be something of a breakwater further out since mangroves can’t handle a lot of wave action, but they could dampen broken waves even more to make an anchorage more comfortable. Also, mangroves could be coppiced maybe for some wood.

#8712

thebastidge
Participant

I like your mangrove concept. It’s good thinking- it also increases biodiversity around your structure much more than the intentional species. A lot of biology depends on surface area, and mangroves greatly increases that. I posted some links on mangroves here:

#12070

delachea
Participant

max wrote:

Hey all, does anyone have some idea of the cost structure behind floating breakwaters? I was looking around but couldn’t seem to find any decent estimates… Ideally some sort of formula that tells you the cost per meter of a breakwater with an effectiveness of [x] would be great!

The only examples of floating breakwaters I found with a quick google search were http://www.whisprwave.com/floating.htm and http://www.wavebraakker.com/floating-breakwater.htm but I didn’t see any easy price estimates on either site. I also these examples would work in a large-scale implementation in the open ocean =

So yeah, just seeing if anyone else has come across the info before I delve any further

Max,

The action of a floating breakwater is not dissimilar to a rigid thin barrier penetrating the water surface to some depth customized to the site. Some company like the MAADI Group (http://www.maadigroup.com) have derived theoretical relationships of Kt for deep-water and transitional depths respectively which agree reasonably well with experiment. I know their floating wave attenuators are made of two (2) thin ductile corrugated barriers with high Yield strength and low modulus of elasticity acting as a damper and they are separated by a distance specific to the site data for best efficiency (as they mention). I keep in mind that a floating wave attenuator shall always be customized for its operating site since wave length & height, wind direction, fetch, water depth and wave periods vary from site to site around the world. When the wave train strikes the seawall at some oblique angle, then the wave front will be reflected at approximately the same angle (i.e. the angle of incidence equals the angle of reflection) helping to increase efficiency. It is always desirable to destroy the wave energy by avoiding a steep vertical wall (like some concrete FBs technologies) with high reflectivity. A corrugated seawall is always preferable. To anwser your question all depends of the width, draft, water depth, anchoring type (chain or piles). A ballpark figure for a floating wave attenuator with a 12 ft width anchored with piles in a 20-ft water depth may worth anywhere from 1000 to 3500 USD per linear foot. I think these links should be helpfull to you:

http://www.chesapeakebaystone.com/

http://www.tpub.com/content/coastalhydraulicslaboratoryfact/sect54eng_sm/sect54eng_sm0096.htm

Hope this help!

delachea

#12075

max wrote:

Hey all, does anyone have some idea of the cost structure behind floating breakwaters?…

We are building floating and submersible concrete structures for quite a time now and our global estimate is 331 Euro/ton . This includes forming, material, labor cost, general project cost.

A ton of structural concrete gives you (at least) a squaremeter of living space at sea. So in general i would say structure building at sea (as soon as it is well established and adapted to the different environment) is not necessarily more expensive than building housing structures on land.

331 Euro per squaremeter of living space is a quite normal building cost for apartments in many places.

A floating concrete breakwater in a size that allows a save harbor for 4 cruiseships is in use as we speak in the monaco harbor (163.000 tons of concrete structure) – this structure is not only a breakwater it also contains a park house, and a shopping mall, inside the hollow structure and several buildings on top of it.

It was built in spain and towed to monaco – so the structure is obviously capeable to stand the conditions of the open sea. (Read more here)

Wil

concretesubmarine.com

European Submarine Structures AB

#12198

max wrote:

… does anyone have some idea of the cost structure behind floating breakwaters?…

Wil

concretesubmarine.com

European Submarine Structures AB

#12306

clarkd
Participant

I have done a “Reverse Cost Analysis” on the cost effectiveness of a breakwater structure by lineal ft. The breakwater structure I had in mind was a pneumatic concrete structure that is 30’x15’x18′ for each unit. It should handle most waves and it would be 30 lineal ft on sea side with a minimum of 40 units making a small breakwater square.

I made a number of assumptions including how much space each seastead should take inside the breakwater and the arbitrary number of \$100,000 per seascape in capital costs.

When talking cost per seastead, I am only refering to the breakwater cost, not the seastead cost itself.

PDF Analysis

Here are some of my conclusions:

• If cost is \$100,000 per stead then cost per lineal ft of breakwater with 15 steads would be ~\$1,000 per lineal ft
• if cost is \$1,500 per lineal ft then 32 steads would have to participate at \$100,000 each
• If cost is \$2,000 per lineal ft then 50 steads would have to participate at \$100,000 each
• At \$3,000 per lineal ft 50 steads would have to participate at \$150,000 each instead of \$100,000 (not shown)
 # Steads Investment Cost/Ft 12 150,000 2,000 20 115,000 2,000 25 100,000 2,000
• The cost per lineal ft of breakwater is critical to the feasibility of building it
• The number of people who have to participate and the likelyhood of it being feasible are inversely proportional
• This is a backward cost analysis. I don’t know if an adequate breakwater can be made for \$1,000 or even \$3,000 per lineal ft

David Clark dfc@rccconsulting.com

#12309

The general idea of cost figures is to make things compareable.

A lineal ft cost figure is not compareable to anything else and therefore not particular useful. In civil engineering and real estate cost figures break down in squarefoot floorspace, cubic meter building volume , cubic meter concrete used, or something like that.

In naval engineering you have normally a “cost per displacement figure” for a vessel.

My general experience in project management is that whenever somebody avoids such “easy compareable” cost figures and comes up with some exotic cost tables it is for a reason. Among the most frequent reasons is the intention to hide the fact that the cost figure per cubic meter/ton fails to meet the average usual in the industry ….

One of the basic dilemmas of seasteading is that it will not happen on large scale until real estate costs (squarefoot floorspace, cubic meter building volume) do not match the land based housing markets.

Whenever a “great new idea” comes up we should break it down to the “basic cost figure” to check its feasibility in matching existing and competing markets. Baseline is if you can not compete with the mainstream you can not exist in the mainstream – seasteading in special niches where cost is not an issue is already happening (oil/gas/yacht).

Wil

#12330

clarkd
Participant

I would agree with Wil if we are talking about the cost of the seastead but it is the cost of the breakwater we are trying to determine. The problem is that as the number of seasteads that can be accommodated by the breakwater goes up, the cost of distance around doesn’t go up by as much. In my analysis, I worked backward from the amount of space each seastead would probably want and then asked, with a reasonable investment of \$100,000 each, how many seasteads would it take to build the breakwater at what cost per ft of breakwater.

I think this was a useful exercise because it sets a budget for costing a piece of the breakwater ie say 30 ft long at a desirable amount of investment and a doable numb of seasteads. If you don’t like in ft then let’s say 10 meters instead of 30 ft.

Unless the breakwater is the seastead, then how can you know if the structure is cost reasonable without the kind of analysis I did?

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