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Floating Breakwater feasibility

Home Forums Archive Structure Designs Floating Breakwater feasibility

This topic contains 39 replies, has 11 voices, and was last updated by Profile photo of wohl1917 wohl1917 3 years, 11 months ago.

Viewing 15 posts - 16 through 30 (of 40 total)
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  • #12131
    Profile photo of Altaica
    Altaica
    Participant

    i_is_j_smith wrote:

    Totally incorrect. Even the image you supplied shows “International Waters” starting outside the 200nm EEZ.

    Notice that arrow right next to “International waters”? It the caption that says “outside territorial waters”?

    Convention on the High Seas
    Done at Geneva on 29 April 1958. Entered into force on 30 September 1962

    Article 1
    The term “high seas” means all parts of the sea that are not included in the territorial sea or in the internal
    waters of a State.
    Article 2
    The high seas being open to all nations, no State may validly purport to subject any part of them to its
    sovereignty. Freedom of the high seas is exercised under the conditions laid down by these articles and by the
    other rules of international law. It comprises, inter alia, both for coastal and non-coastal States:
    (1) Freedom of navigation;
    (2) Freedom of fishing;
    (3) Freedom to lay submarine cables and pipelines;
    (4) Freedom to fly over the high seas.
    These freedoms, and others which are recognized by the general principles of international law, shall be
    exercised by all States with reasonable regard to the interests of other States in their exercise of the freedom of
    the high seas

    ouk emou alla tou logou akousantas homologein sophon estin hen

    #12133

    i_is_j_smith wrote:

    My experiences with anchoring large 90% submerged structures (as my prototype) in real world conditions point in exactly the oposite direction.

    The forces on the anchor rig are SURPRISINGLY low – much lower than they are for a structure of similar size that is floating high in the water like a ship or a boat.

    Of course the forces are low! The forces acting on the mooring system are due to wave drift forces. Since 90% of your structure is submerged it isn’t reflecting any wave energy thus the drift forces are minimized. Something floating high in the water, like a ship or TLP, reflects or absorbs a lot more wave energy thus is affected more by wave drift forces. TLPs try to minimize their exposure to the wave energy by presenting a minimum surface area to the waves, thus mooring them in depths of 1k to 2k is possible.

    A breakwater is the exact opposite of your submerged structure example. A breakwater not only sits high in the water, it maximizes the surface area exposed to the waves. Its entire purpose is to absorb or reflect a maximum amount of wave energy. Thus the forces acting on the mooring system will be many times greater than those of a TLP, and many many times greater than those of a submerged structure.

    ——————

    If submerged structures have a tremendously priviledged situation what concerns the needed strenght of the anchor rig, i would suggest to simply go to a submerged breakwater design. Submerged structures are very efficient breakwaters as we can see on natural reefs, – they also do not obstacle the view of the seastead residents which was a important breakwater design point in dubai.

    The idea that anchoring a breakwater is a more severe load case than a oil rig does not look very acertive to me and i can not confirm it in scaled down real world experiments.

    It’s all about wave drift forces. There is no doubt what-so-ever that the wave drift forces acting on a structure that has a large waterplane area will be much larger than those acting on a structure with a small waterplane area. That is just physics, not opinion. Thus the larger the wave drift forces acting on the structure, the stronger the mooring system needs to be. The stronger the mooring system needs to be, the more expensive it will be.

    ————

    Whatever the physics says – seamenship says that anchors in practice are not designed to hold anything near a magnitude of the ship weight – so my favorite theroy is that the physics that predict such forces does not happen very freqently in practice.

    In my practice i could not measure more than 1kp force on the anchor rig of a 20 ton hull – so i share your argument that the structure design influences in the needed anchor rig strength – but i doubth that anchoring a breakwater is a extreme special case – a breakwater is just another structure, any structure is a breakwater.

    Oil rigs have narrow tolerances for movements in all directions. On the other hand breakwaters can be anchored with wide tolerances and flexible anchor rigs.

    It has nothing to do with the positional tolerances…it has to do with strength. Once the wave forces push the breakwater to the extent that its flexible anchor rig will allow it will continue to strain the lines. The anchoring system needs to be strong enough to handle the predicted maximum forces, and that is where the expense comes in.

    ———————-

    It is practice to give a long anchor chain to make the anchor hold better the chain weight adds flexibility to the rig and reduces the transfer of waves movements to the anchor – in a oil rig this can be done only limited due to the needed narrow position tolerances – a breakwater is free of those narrow station keeping needs.

    A breakwater should interact with waves to convert their engegy into something that cancels out mutally not into forces on the anchor rig.

    ANY interaction with waves is going to cause forces acting on the anchor rig. As soon as the wave hits the breakwater it imparts its energy to the structure. You can’t cancel out anything. You can only minimize the forces by minimizing the interaction with the waves, and a breakwater isn’t designed to do that.

    Read Eelco’s great blog entry on wave drift forces. He makes the point very well.

    —————–

    I agree on the basic physics (force creates contrary force) – doubth that this applies on breakwaters in a strikt way – i would suggest to look at how mangrove roots dampen waves – they convert the energy not into a unidirectional force but into small turbulent currents that cancel out mutually.

    Looking for seamounts limits seasteading to places where no business is happening – it is economic suizide.

    Sorry, but just like the first civilizations and cities formed around rivers and fertile areas…areas where it was easy to settle…the first seasteads will need to choose areas that are easy to build in. This means either an EEZ or a seamount.

    Now if your idea of a seastead is a cluster of smaller, mostly-or-fully-submerged single family structures then you have more flexibility. You might be able to anchor in extreme depths with a manageable cost.

    ———–

    Yes that is true. Yust a first step out of EEZ is so hard to perform and so expensive to finance that i would tend to envision the first seasteads more like Dangerous Don´s bait barge – or the model of the sea gypsies…

    ————–

    I can imagine a outer ring consisting of breakwaters (deeploaded) that get wave washed every now and then and where the living spaces are attached like barnacles to stand the sea.

    Then a inner ring with medium strength floating islands…

    finally – a general marina as inner core with yachts, houseboats, and other “soft solutions”

    [/quote]

    #12135
    Profile photo of i_is_j_smith
    i_is_j_smith
    Participant

    Altaica wrote:
    Convention on the High Seas
    Done at Geneva on 29 April 1958. Entered into force on 30 September 1962

    You are right, that image does show “international waters” up to the 12nm limit. While that might be technically correct, it doesn’t change anything. You cannot setup a seastead in the EEZ. As long as we are quoting UNCLOS:

    PART V: EXCLUSIVE ECONOMIC ZONE

    Article56: Rights, jurisdiction and duties of the coastal State in the exclusive economic zone

    1. In the exclusive economic zone, the coastal State has:

    (a) sovereign rights for the purpose of exploring and exploiting, conserving and managing the natural resources, whether living or non-living, of the waters superjacent to the seabed and of the seabed and its subsoil, and with regard to other activities for the economic exploitation and exploration of the zone, such as the production of energy from the water, currents and winds;

    (b) jurisdiction as provided for in the relevant provisions of this Convention with regard to:

    (i) the establishment and use of artificial islands, installations and structures;

    (ii) marine scientific research;

    (iii) the protection and preservation of the marine environment;

    (c) other rights and duties provided for in this Convention.

    So if you are going to just float around in the EEZ without fishing, doing any form of mariculture, using wind turbines, dumping waste overboard, or anything else that could impact the marine environment then you are fine.

    For the record, whenever I say “international waters” I am talking about waters outside the jurisdiction of any existing nation. This means 200nm from shore or even further if the nation claims continental shelf areas.

    #12136
    Profile photo of i_is_j_smith
    i_is_j_smith
    Participant

    ellmer - http://yook3.com wrote:
    i would suggest to simply go to a submerged breakwater design. Submerged structures are very efficient breakwaters as we can see on natural reefs,

    Submerged structures work by decreasing the water depth, which increases the wave height. The goal is to increase the wave height until it reaches a point where the structure is no longer stable and it collapses or “breaks”. As I said in my other post I think this is probably a much better system than the standard “big flat wall” style breakwater. It seems logical that a submerged breakwater of this type would experience smaller wave drift forces than the big flat wall style, and thus require simpler mooring systems. This would have to be tested, of course.

    ellmer - http://yook3.com wrote:
    Whatever the physics says – seamenship says that anchors in practice are not designed to hold anything near a magnitude of the ship weight

    That’s because the wave drift force is based on the surface area exposed to the waves, and the angle at which the waves impact the surface. A ship at anchor is not kept parallel to the waves…it turns its bow into the waves so the wave drift force is minimized. A “big flat wall” breakwater doesn’t have this option, and thus needs to handle wave drift forces many times greater than a ship would experience.

    ellmer - http://yook3.com wrote:
    a breakwater is just another structure, any structure is a breakwater.

    True, but the forces acting on different structures depend on the situation. For instance take two duplicate caisson-style breakwaters. One is moored parallel to the wave direction, so the waves are impacting directly on the surface. The other is moored at an angle to the wave direction. The second one will experience lesser wave drift forces and thus doesn’t need as strong a mooring system.

    This is great if you are in an area where you can predict the direction of the waves, such as near the coast, or if your structure can rotate to always present the best angle to the waves. But out in the open ocean, in a large moored structure, the waves will be coming from all directions. The wave drift force will be maximized.

    ellmer - http://yook3.com wrote:
    a breakwater is free of those narrow station keeping needs.

    Unless, of course, there are other seasteads with their own breakwaters nearby. That needs to be considered.

    ellmer - http://yook3.com wrote:
    I agree on the basic physics (force creates contrary force) – doubth that this applies on breakwaters in a strikt way

    Physics is physics…it applies to everything equally. But you can design something that works best in a given situation. I doubt very much that large, moored, caisson-style breakwaters will be viable in water depths exceeding several hundred meters. The cost for mooring these structures will be enormous and will very quickly become prohibitive. But we need breakwaters. So we need to design a structure that:

    1. Decreases substantially or completely eliminates wave forces acting on structures inside its protective area.
    2. Minimizes wave drift forces acting on its own structure and mooring system.
    3. Is strong enough to require minimal repairs and maintenance over the lifetime of the ENTIRE structure (breakwater AND the seastead inside).

    So lets get designing, and lets have TSI start engaging engineering firms to give us cost estimates on mooring systems and concrete structure construction as well as metocean analysis at several prime seasteading locations.

    #12137
    Profile photo of i_is_j_smith
    i_is_j_smith
    Participant

    Another option to discuss is using fixed or compliant towers for the breakwater. Fixed platforms have been used in water depths from 70m to 500m so would work just fine on a seamount. The question is how the costs would compare, given a certain wave drift force that the system would have to support.

    With a mooring system it just has to counteract the wave forces, while a fixed tower needs to counteract the wave force in addition to supporting the entire weight of the breakwater structure. But fabrication, installation, and maintenance of a gravity base structure such as the Condeep systems is much simpler than a mooring system.

    Using a compliant tower might be even better, since the flexibility of the structure might make the breakwater even more effective. These can go even deeper than fixed platforms and might even be cheaper to construct.

    I’m thinking of a large, circular breakwater supported by fixed platforms or compliant towers, with the central seastead structure supported by it’s own buoyancy but kept in place by rigid attachments/walkways to the breakwater. This would eliminate the need for mooring/anchoring completely and results in a very simple and practically maintenance-free system. I have no idea about cost, though. I haven’t been able to find any information on the cost of fixed platforms or compliant towers for given depths….

    #12138
    Profile photo of Matt
    Matt
    Participant

    Why does the breakwater need to be anchored to the seabed?

    With a breakwater design there would be one big (probably segmented) fixed structure around a lot of lagoon real estate.

    Instead of positioninig the seastead relative to the submerged landmass, the internal RE units would be positioned relative to the breakwater, maybe with a network of tension/compression links. If this looks too much of a net, I remind you it could be only partially that way, symbolizing the more “seadentary” units, while houseboats, etc could remain off the grid but within the lagoon. Whe the entire lagoon becomes links it means it has saturated and it’s time to build more, and evaluate the experience. It could define a cycle.

    The whole seastead would minimize interaction with waves by being a massive concrete ring moving gently. Taking advantage of currents (throug switchable keels), winds (sails), and harnessed energy too costy to store (?), could a system of propulsion be developed to mantain a breakwater seastead stationary?

    Why does it have to be stationary anyway? I’m not advocating the use of the oceanic gyres, but maybe a combination in which the seasted moves just enough to avoid bad conditions, select climate and get closer or farther from different countries.

    #12139

    i_is_j_smith wrote:
    It seems logical that a submerged breakwater of this type would experience smaller wave drift forces than the big flat wall style, and thus require simpler mooring systems. This would have to be tested, of course.

    We tested that. What you see on the picture is the same 20 ton displacement structure floating on middle line (without ballast) and floating 90% submerged (with a tower sticking out) – i can confirm that the tension on the anchor is bigger when the structure floats high in the water. It is extremly low (1kp) when it floats deeploaded. I can not confirm a monumental difference in tension in the anchor rig depending if waves come from the front or from the side (maybe some). I would spot the wind profile as the dominating factor for forces on the anchor rig. This leads my thoughts to submerged tunnel breakwater solutions…or at least deeploaded breakwater solultions…

    i_is_j_smith wrote:
    True, but the forces acting on different structures depend on the situation. For instance take two duplicate caisson-style breakwaters. One is moored parallel to the wave direction, so the waves are impacting directly on the surface. The other is moored at an angle to the wave direction. The second one will experience lesser wave drift forces and thus doesn’t need as strong a mooring system.

    I see Nkossa and Adriatic LNG anchored miles offshore with cero adaptability to wave direction and quite small mooring sistems – seems to work…

    ellmer - http://yook3.com wrote:
    a breakwater is free of those narrow station keeping needs.

    i_is_j_smith wrote:
    Unless, of course, there are other seasteads with their own breakwaters nearby. That needs to be considered.

    I would suggest anchoring the seastead elements in package – with a shared tendon ancor…

    You can leave the blue buoy some 20m below surface – it will always stay straight above the anchor block – then you anchor the structure to the buoy with a short chain.

    The blue buoy works like a “artificial seamount” bringing your anchor point to shallow depth. When using neutral buoyant polypropylen line (or extrusion) you can use that rig in ANY depth. No high cost anchor handling required. It is quite flexible (this is why oil industry uses a more direct sistem to take flexibility out.)

    In a oil rig tendon anchor the blue buoy IS the platform. The tendons can be steel pipes instead of cables or chains.

    At seasteading the additional flexibility will not hurt – no oil well to drill…

    All this works on industrial scale for 2000m and deeper as we speak – so testing is done.

    Wil

    concretesubmarine.com

    European Submarine Structures AB

    #12141
    Profile photo of i_is_j_smith
    i_is_j_smith
    Participant

    Matt wrote:
    Why does the breakwater need to be anchored to the seabed?

    So it won’t move (see below)

    Matt wrote:
    Why does it have to be stationary anyway? I’m not advocating the use of the oceanic gyres, but maybe a combination in which the seasted moves just enough to avoid bad conditions, select climate and get closer or farther from different countries.

    There are many who advocate mobile seasteads. I don’t agree with that approach, for several reasons:

    1) To be taken seriously as a new nation you need to have territory. It is doubtful that any existing nations would accept an artificial platform in the ocean as territory, but it at least has a small chance compared to a seastead that wanders the oceans.

    2) It helps for people to know where you are, for shipping and business purposes. Also telecommunications systems are nearly impossible to implement if your seastead will be mobile.

    3) The cost of implementing reliable propulsion systems is enormous for installation, fuel needs, maintenance and repair, backups, etc.

    4) Mobility adds an entire limiting factor on the possible structure of the seastead. A mobile structure will have many more forces acting on it than a fixed one.

    There are many other reasons, but you get my “drift”. This is just my opinion, of course. I don’t believe that the benefits of mobility outweigh the costs and limitations.

    #12142
    Profile photo of tusavision
    tusavision
    Participant

    There’s no need to choose. Have you guys seen how wave power works? It’s giant concrete pontoons connected by universal joints with hydraulic cylinders pumping hydraulic oil in to pressure accumulators.

    Make the breakwaters out of those in a snoke flake with various lengths to take advantage of the different wave harmonics. Use concrete sewer pipes/propane tanks as your legos with concrete as your mortar. Hydraulic motors are cheap from china, and propane tanks are pressure accumulators. When the propane tanks are at max pressure, divert the flow to the hydraulic motors/car alternator generators and battery banks. When the batterys are fully charged: use electrolysis/desalinator of water to generate hydrogen gas.

    When you have enough hydrogen gas, use molten salt thermal energy storage.

    It’s all in “The Millenial Project” from there.

    Our problem isn’t waves. Our problem is a good supply of pressure vessles, and a stable market price which we can model business plans around.

    Find a liquid supply of available/cheap pressure vessles and the problem solves itself.

    Edit: it’s trivial to protect the hydraulic cylinders from corrosion with a boot seal.

    #12143
    Profile photo of Matt
    Matt
    Participant

    No I’m just asking only a technical question. Do these structures need to be tethered or fixed to the seabead, or could they “simply” be geopositioned with propulsion?

    Or another way to put it: Does a breakwater have to endure a lot less resistance if it’s set (semi) adrift? Enough for propulsion to be able to compensate?

    #12144
    Profile photo of i_is_j_smith
    i_is_j_smith
    Participant

    ellmer - http://yook3.com wrote:
    It is extremly low (1kp) when it floats deeploaded.

    What was the sea state during that experiment? In both those pictures it is very calm, and if I remember correctly the one time you experienced storm conditions you were completely submerged.

    My guess is that if your 20-ton submarine were in 2-3m waves, floating high enough so that there was no overwash, you would see significant increases in the force on the anchor rig.

    Same goes for both Nkossa and Adriatic LNG. I don’t have enough information on their mooring systems to comment, or on the highest seastate either has had to endure.

    Now if we can find a seamount sitting in international waters that has the same metocean profile as 60km off the Congan coast then we are in business. This is why I also advocate finding the calmest, easiest place to setup shop that we can.

    But your information further solidifies my belief that a caisson-style floating breakwater is a no-go, and we’ll have to rely on something else. I’d love to see if there was more recent research on the bubble breakwaters…

    #12145
    Profile photo of i_is_j_smith
    i_is_j_smith
    Participant

    Matt wrote:
    No I’m just asking only a technical question. Do these structures need to be tethered or fixed to the seabead, or could they “simply” be geopositioned with propulsion?

    Or another way to put it: Does a breakwater have to endure a lot less resistance if it’s set (semi) adrift? Enough for propulsion to be able to compensate?

    It doesn’t matter if you are held in position by a physical connection to the ocean floor or thrusters controlled by a central computer. The result is the same, the only difference is the short and long-term costs.

    We are not discussing the effect of wave forces on the breakwater structure itself, but on the system keeping it in place. If the breakwater were adrift then all you need to do is design a structure strong enough and high enough to stop the wave impact forces. What I am concerned about are the drift, wind, and current forces that would act on any positioning system.

    If there is a certain force pushing the seastead/breakwater in one direction you need to apply the same force in the opposite direction to keep the same position. In a mooring/anchoring system that force is supplied by the anchor and the lines. In a propulsion system that force is supplied by the thrusters/kite/sail/whatever. Since all large floating stationary structures that exist right now use mooring my assumption is that mooring is the cheaper and better option.

    #12146
    Profile photo of i_is_j_smith
    i_is_j_smith
    Participant

    tusavision wrote:
    Have you guys seen how wave power works? It’s giant concrete pontoons connected by universal joints with hydraulic cylinders pumping hydraulic oil in to pressure accumulators.

    There are many different methods for harnessing wave energy (not POWER). The Pelamis system is just one of them. There is no evidence that these systems act as a breakwater. In fact, because they are so thin, they would be terrible breakwaters…even stacked side by side. They haven’t shown any wave attenuation or dispersal evidence at all.

    tusavision wrote:
    Our problem isn’t waves.

    Our problem most definately IS waves. Because with lots of waves you will not get a seastead. The production of pressure vessels is simple and not even worth noting. It’s just a matter of cost. You can build all the pressure vessels you want, come up with the greatest business plan in the metaverse, but if nobody wants to live there or invest in your business because the structure heaves all over the place and keeps tearing itself apart in a storm then it’s a failure.

    #12148
    Profile photo of Altaica
    Altaica
    Participant

    i_is_j_smith wrote:

    Altaica wrote:

    Convention on the High Seas
    Done at Geneva on 29 April 1958. Entered into force on 30 September 1962

    You are right, that image does show “international waters” up to the 12nm limit. While that might be technically correct, it doesn’t change anything. You cannot setup a seastead in the EEZ. As long as we are quoting UNCLOS:

    [/quote]

    Any State’s purported sovereignty to any part of International waters is noy valid according to Customary international law.

    Not only is it a against Customary international law. it’s against treaty law.

    The United Nations Convention on the Law of the Sea (UNCLOS) is the international agreement that resulted from the third United Nations Conference on the Law of the Sea (UNCLOS III), which took place from 1973 through 1982.

    Convention on the High Seas entered into force on 30 September 1962. That’s over 10 years befor the UNCLOS was even concived of.

    UNCLOS;s limits on activities outside the teritorial waters is clear only aplicitable against members of the International Seabed Authority .

    UNCLOS wrote:
    Affirming that matters not regulated by this Convention continue to be governed by the rules and principles of general international law,

    2. (1) “States Parties” means States which have consented to be bound by this Convention and for which this Convention is in force.

    UNCLOS wrote:
    Desiring by this Convention to develop the principles embodied in resolution 2749 (XXV) of 17 December 1970 in which the General Assembly of the United Nations solemnly declared inter alia that the area of the seabed and ocean floor and the subsoil thereof, beyond the limits of national jurisdiction, as well as its resources, are the common heritage of mankind, the exploration and exploitation of which shall be carried out for the benefit of mankind as a whole, irrespective of the geographical location of States,

    clearly

    resolution wrote:
    1.The sea-bed and ocean floor, and the subsoil thereof, beyond the limits of national jurisdiction (hereinafter referred to as the area), as well as the resources of the area, are the common heritage of mankind.

    2.The area shall not be subject to appropriation by any means by States or persons, natural or juridical, and no State shall claim or exercise sovereignty or sovereign rights over any part thereof.

    13.Nothing herein shall affect:
    (a). The legal status of the waters superjacent to the area or that of the air space above those waters;
    (b). The rights of coastal States with respect to measures to prevent, mitigate or eliminate grave and imminent danger to their coastline or related interests from pollution or threat thereof or from other hazardous occurrences resulting from or caused by any activities in the area. subject to the international régime to be established.

    ouk emou alla tou logou akousantas homologein sophon estin hen

    #12153

    ellmer - http://yook3.com wrote:
    anchor force is extremly low (1kp) when it floats deeploaded.

    i_is_j_smith wrote:
    What was the sea state during that experiment?

    It was not a single experiment – the hull stayed there anchored for years during the nightiees – i had a mooring rig that indicated the forces on the rig with a buoy that would go under as soon as forces overpass 5 kp – a status that i never happened nor was any close to happen – what surprised me.

    The storms that i experienced during those years where sufficiently severe to break trees and the waves sufficiently hazardous to make 30 foot sailing yachts (of the open ocean capeable type) call SOS while i had my coffee cup still standing on the table. This was the case in both states submerged and surfaced on the anchor place.

    i_is_j_smith wrote:
    My guess is that if your 20-ton submarine were in 2-3m waves, floating high enough so that there was no overwash, you would see significant increases in the force on the anchor rig.

    I will not dismiss the “significant increase” as the buoy was designed to go under at 5kp it is possible that the force difference is 0.5 kp 90% deeploaded and close to 3kp floating only 50% deeploaded – this would still be a “signifficant increase”. On the other hand we are still quite far away from theocal possible 20.0000 kp force which is anchor rig forces in the “order of structure weight”.

    i_is_j_smith wrote:
    Same goes for both Nkossa and Adriatic LNG. I don’t have enough information on their mooring systems to comment, or on the highest seastate either has had to endure.

    You are right we don’t have the details – what we have is fotos of their mooring sistem – and those fotos tell me two things – those structures are anchored with no bow pointing against the waves, and their anchor sistem is not designed to hold anything near structure weight… we need to investigate.

    i_is_j_smith wrote:
    your information further solidifies my belief that a caisson-style floating breakwater is a no-go, and we’ll have to rely on something else.

    Dismiss caisson-style seasteads and breakwaters is possibly premature – especially as oil/gas industry is moving EXACTLY in that direction (probably for good reasons – cost efficiency most bang for the bug)

    i_is_j_smith wrote:
    Now if we can find a seamount sitting in international waters that has the same metocean profile as 60km off the Congan coast then we are in business.

    I suggest to create a “artificial seamount” that provides the equivalent of “shallow anchorpoint” for our structures with a tendon anchor buoy – as described – in the seaarea that is convenient for business reasons.

    Wil

    concretesubmarine.com

    European Submarine Structures AB

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