WO2015009162A2

WO2015009162A2 - Process and structure for rehabilitation of sea floor

Info

Publication number: WO2015009162A2
Application number: PCT/NO2014/050130
Authority: WO
Inventors: Trygve Sverreson
Original assignee: Ecopros As
Priority date: 2013-07-17
Filing date: 2014-07-17
Publication date: 2015-01-22
Also published as: EP3021990A2; NO335653B1; NO20130997A1; WO2015009162A3

Abstract

For rehabilitating sea floor around and under a potentially environmentally hazardous area such as shipwrecks including hazardous cargo or deposits of environmentally hazardous material, it may be used a layered bottom structure that may be placed on top of such polluted sea floor in lakes and oceans at and about areas, pockets or stores (1) of environmentally hazardous material(s), wherein said environmentally hazardous material(s) is in danger of leaking out to the surroundings. The layered structure comprises at least one layer of a mass on top of said area of environmentally hazardous material(s) including a viscous material (3,9) comprising sludge/earth/clay and including fine-graded particles impregnated with reactants that are able to react with the relevant environmental hazardous material(s) and bind and/or render these harmless. It is also disclosed a process for distributing such a layered structure.

Description

PROCESS AND STRUCTURE FOR REHABI LI TATI ON OF SEA FLOOR

Ambit of the I nvention

The present invention concerns a process for rehabilitating sea-floor being polluted or having sub-sea deposits or stores of environmental poisons, said poisons being able to escape to the environment from pockets or deposits, said pockets or deposits being in danger of expelling their contents of environmental poisons to the surrounding masses of water. The process according to the invention comprises those features and steps that are defined in claim 1.

Background for the Invention

Through history there have been transported large amounts of environmentally hazardous materials on ships, both as bulk cargo and in different forms of packed goods, and dangerous and harmful deposits have been placed in stationary pockets on land or on the sea floor as well, e.g. in naturally occurring stone pockets such as craters or in artificially excavated pockets such as mines or other deposits. Typical materials with a more or less environmentally hazardous character are e.g. ores, raw materials and semi-fabricates as well as chemical products of different kinds. From the Second World War and in subsequent acts of war it is known that chemical products that have been used for objects of war, or as a basis for such products, have been transported by sea routes. In connection with sea transport it is sadly not possible to avoid that such ships become ship-wrecked and sink with their entire cargo. Since the tooth of time includes corrosion and deformation or shipwrecks, one is faced with a need for securing sunken cargo of an environmentally hazardous nature. Preferably dangerous cargo should be hoisted and brought out of the eco-system, subsidiary remaining cargo must be secured from becoming distributed and thereby avoiding partially long-term and substantial environmental effects in a large scale. The same goes for deposits of environmentally hazardous or harmful nature such as ores or expelled masses (e.g. ones that contain lead or mercury).

A relevant example in Norwegian shores is the German submarine U 864 from the Second World War that in 1945 was sunk at Fedje in Hordaland. The submarine carried a special cargo of 67 tons of mercury bound for Japan, and that is now attempted to bring into safety. Other examples are sunken ships in Danish and German straits and in the Baltic Sea, with different types of cargo of e.g. chemical war- fare substances. In the last days of the war it is known that several ships were sunk to accelerate the end of the war.

Concerning mercury this is a naturally occurring element and is a metal that has been used for thousands of years. Mercury occurs naturally in several forms, but not all of the forms are harmful to humans. It is particularly the organic forms of mercury that are poisonous for several organisms. For humans methyl mercury is assimilated in the gastro-intestinal tract, and may pass through the so-called blood- brain-barrier and thus exert damage on the central nervous system. Methyl mercury may also be assimilated by other organisms such as fish or crustaceans or by predators feeding on these. Similarly mercury may be accumulated through the food chain and give rise to assimilation of relatively large amounts of mercury in the organisms being on top of the food chain (whereof humans are one of the organisms that are high in the food chain and consequently have a possibility of assimilating large amounts of organic mercury through caught or harvested sea animals) .

Microorganisms (bacteria) in sediments are able to transform inorganic mercury into organic methyl mercury. The bacteria are predominantly active in nutrient-rich environments i.e. in locations where there is a high production of algae and plankton such as shallow fjords and river mouths. Conditions influencing the bacterial activity in an area is thus one of the factors that should be considered concerning how to activate measures for isolating or removing environmental toxins in general.

The need for securing the sea floor is also present in the vicinity of land-based chemical industry expelling to sea recipient or that have been located close to rivers where deposits from expelled material may be significant. Thus there exists a need for a process that may secure exposed locations in a robust, safe and sustainable manner with a minimum of expense. The solutions must be able to withstand the current conditions concerning weather, wind, waves and current in the relevant area. Even if the selected solution should include the hoisting of cargo and ship, the sea floor might already have become polluted. Dredging masses out from the location may in itself constitute a risk of spreading the settlements from the cargo. A practical method for safe covering may consequently be quite relevant in many cases. Prior Art

It is previously known from GB 200229907 to submerge a flexible covering material onto a sunken shipwreck. Such a covering material is still of a temporary character where the covering material has to be removed from the shipwreck when the cleaning has been performed.

From JP 2004195456 it is known a process being meant for preventing water to become polluted by dioxins, and wherein a dioxin-containing bottom sediment is covered with a layer of steel slag and sand.

From US patent 4266889 it is known a method for covering shipwrecks with concrete at great depths.

From WO 200760275 it is known a process wherein an enclosing material comprising sepolite clay is poured over the polluting material on the sea floor. This sepolite clay is specified to be an absorbing material for the relevant pollutants.

From JP 2007063923 and JP 2007061054 it is disclosed enveloping subsea wreckage in sand and furnace slag for covering the relevant subsea polluting structure.

A frequently used method for isolating and rehabilitating potentially harmful waste on land and that also is mentioned concerning isolating pollutants on the sea floor (see supra) has been to cast the waste in concrete for thus isolating it from the surroundings during a long time. The disadvantage of such a casting is that concrete is a rigid material that to a lesser extent is able to adjust to movements in the underlying material without cracking and it may also be subjected to external damage by being hit by heavy objects from above such as e.g. anchors or ships running aground or by fishing with heavier bottom tools. Unarmored heavier concrete constructions will also by themselves develop cracks on account of variations in its course of hardening. The development of cracks in the covering material will create a possibility for the environmentally hazardous material escaping to the surroundings through such cracks. It is consequently a significant advantage if the covering material is self-sealing thus avoiding the creation of cracks and thereby provide a safe and lasting barrier between the hazardous material and the surrounding. One of the goals of the present invention is thus to provide a layered isolating mass over possibly environmentally polluting areas and objects so that this mass is phys- ically stable and totally covering and wherein the mass is layered in such a way that is apparent from the subsequent claims.

Disclosure of the Invention

The present invention will be disclosed with reference to the appended figures showing embodiments of possible constructions of layered structures that may be placed upon and cover an object of sediment with a content of environmentally hazardous material.

Figure 1 displays a concrete example where the environmentally hazardous object is the German submarine U-864 from the Second World War that in 1945 was sunk off Fedje, Norway. This submarine carried large amounts of mercury in iron containers. These iron containers are now, more than 60 years later, about to corrode and release their mercury to their surroundings. The hull of U-864 is currently corroding as well in addition to those damages that the submarine acquired when it was sunk. U-864 was split in half when it was sunk and the middle section of the submarine was exploded into pieces. Several of the mercury-containing containers carried by the submarine were thus scattered across an area from which it is expensive and difficult to bring this to the surface. In this situation it is relevant to be able to use an isolation method for the hazardous material having as a consequence that the danger of mercury poisoning of the surrounding areas is eliminated.

Figure 2 displays an alternative layered structure for the inclusion or covering of polluted sea floor according to an embodiment of the process and layered structure according to the invention.

The process according to one embodiment of the present invention for rehabilitating a sea floor comprises the steps of, after having localized the relevant location of the environmental hazards as well as having determined the type of the one or more of the relevant environmental hazards, initially placing onto the relevant area a layer 2 of stone masses comprising/consisting of stone within the size interval of about 100-200 mm in diameter and with a thickness within the size interval of about 0.5- 1.5 m based on the amount of absorbing material/mass that is needed in each instance. This stone fraction is named crude crushed stone and is to be free of fines. After placing this initial stone layer there is on top of this added a new layer of viscous material 3 comprising sludge/earth/mud comprising fine-graded particles impregnated with reactants or adsorbents that may react with the relevant environmental poison(s) and bind and/or inactivate these. The viscous material 3 sinks down into the spaces between the rocks in the initial layer 2 and furthermore to the bottom of this initial stone layer 2. This sinking of the viscous material 3 bring the reactants or adsorbents in the viscous material 3 into contact with the relevant environmental hazardous materials for, when these environmental hazards escape or leach out of their locations, reacting with or adsorbing and thus rendering these environmental hazards inactive. The fine-graded particles in the viscous material 3 have the effect that the relevant environmental hazardous materials diffuse into or are adsorbed by this material for forming a large reaction zone where the environmentally hazardous substances may be rendered inactive. Since the viscous material 3 is located between the rocks in the initial stone layer 2 the stones in the initial stone layer 2 will constitute a barrier against sea currents, tidal movements or other effects such as waves or propeller currents which otherwise might disturb the stability of the viscous material 3.

In an alternative embodiment it may be possible to apply the viscous material 3 with the reactive particles directly onto the polluted sea floor and also without a covering layer on top until the area becomes sealed and finalized. This may be an option in such locations where there are no currents and where the water is undisturbed such as in deposits lying in craters or dents in the sea floor or in mines.

With reference to the embodiment shown in Fig. 1 the applied layer 2 (crude crushed stone) will serve as mechanically stable substratum for new covering masses, said covering masses having as a purpose to create a new sea floor.

The viscous material 3 will also form a partial barrier against the external environment in relation to the environmentally hazardous material. The layer comprising stone 2 and viscous material 3 is not completely impermeable, but will after consolidation of the viscous material 3 only include standing water like in consolidated bottom clay and other bottom material. On account of this relationship there will no longer be any active transport of water through the viscous material 3. A possible out-transport of water-soluble molecules through this layer 3 will consequently predominantly happen through diffusion. The time it takes for water-soluble molecules to pass the initial layer will consequently be relatively long (in the range of weeks to months) and give ample time for any relevant reaction to happen between the environmentally hazardous materials and the reactant/adsorbent.

During consolidation of viscous material 3 (settling of the material through the crude crushed stones 2) there will arise a transport of fluids (water from washed reactants and adsorbents) in a vertical direction up through the viscous material 3. The volume of water from such a consolidation is limited in relation to the fluid volume being supplied by the viscous material 3. When selecting the composition of the viscous material 3 it must be taken into account that surplus water from the consolidation will have to be transferred to the local area above the stone layers with a decreasing volume stream up to the end of the consolidation. In practice it will here be a matter of weeks.

The purpose of the structure of the viscous material is that it is to create an intimate mechanical mixture of a carrier material surrounding porous and fine-graded particles, said particles being made of or surrounding chemical reactants, adsorbents or biologically active materials (e.g. in the form of bacteria or algae) that may react with, transform, adsorb or break down the relevant environmental poisons.

Examples of reactants that may be relevant to include inside the viscous material may be two- or three-valid iron oxides, ground olivine, oil-degrading bacteria, combat-gas-degrading or inactivating reactants, adsorbents or microorganisms, etc. The selection of reactants or microorganisms will have to be based on knowledge of the environmental hazards that are to be disabled. Information concerning the relevant environmental hazards may e.g. be found in public or private archives, logbooks containing information about the cargo carried by the shipwreck, or may be determined through analysis or investigations on site, e.g. through the use of probes, robot-operated vehicles (ROV, Remote Operated Vehicles) and/or scuba- divers.

In an alternative embodiment the viscous material 3, having been presented supra as pumpable sludge, may optionally also be presented in the form of a pellet. The size of such pellets should lie within a range so that they may penetrate into the distance between the crushed rocks in layer 2. The size of such a distance may be regarded as the remaining volume between at least four adjacent rocks in the layer 2 formed by drawing a line between the mass center in each rock for creating a theoretical polygon, determine the volume of the rocks within this theoretical poly- gon, determine the difference between the volume of the theoretical polygon and the volume of the rocks, this volume being called the available rest-volume, and determine the maximal size of the relevant pellets as particles that may pass through this available rest-volume being formed between the rocks.

Such an available rest volume may also be determined empirically by using a defined test volume being filled with the relevant rocks in layer 2. The test volume may be a cube or a cylinder or any other hollow space with a known internal volume. After the test volume has been filled with the relevant rocks, there may be performed a weighing followed by a filling with water. A new weighting may then be performed. As an alternative to weighting, the supplied water volume may be drawn off and be measured with respect to volume. This water volume provides a basis for estimating the available rest volume in the test volume. This volume may furthermore provide a basis for determining the largest diameter for the pellets or the reactive particles that may be included in the viscous material 3.

As an example of determining free volumes in crude crushed stone it will be explained that prior to crushing the stone the volume weight is about 2.7 depending on the type of rock. The mineral olivine has e.g. a volume weight of 3.3 and is considered to be a heavy type of rock. When stone is crushed a "dilution" with air arises so that the volume weight is reduced with about 1.7-1.8. The weight loss in volume weight in crushing represents the empty space being formed between the particles during the crushing. The difference in volume weight before and after the crushing/sorting is an alternative way of calculating the volume of the free space between the stone particles in the relevant stone layer 2.

If there is performed a sorting of crushed rock into small segments, the ratio of air will increase. It may e.g. be mentioned that it is estimated that a free volume in sorted crude crushed rock in the size interval 150-200 mm in diameter will lie at about 40% of the total volume occupied by the stone mass. This will have as a consequence that 30,000 m² area covered with such crushed crude rock at a height of 1 m will include a free volume of about 12,000 m³.

The larger the test volume the better the result will approach the real volume in a large scale. It is otherwise possible to adjust the container test by making a subtraction for reducing the volume error connected to the deviation of the border surface as a consequence of the stone abutting against a plane surface and not against a neighboring rock. By adjusting this border volume by 1/3 of the size of the rock multiplied with the total internal surface adjacent water (including the top surface provided the water covers the stone masses), it is obtained an adjusted value for the available volume being very close to the actual volume in a large scale.

To calculate a required volume in the layer of crude crushed rock 2 in each concrete case of coverage will depend on a pre-calculation of the amounts of reactant/ab- sorbent. A number for this volume is possible to determine in either case of sludge or pellets. The material is to be placed out physically in a free volume that is able to include this amount with a good margin. The relevant masses in the layer 3 may with a good precision be registered in connection with its placement, e.g. as kg/m² covered sea floor. The amounts may also be varied if there should exist areas with an extra need for covering masses.

The structure of the relevant pellets may be produced in different embodiments. In one embodiment a pellet may be provided with a water-soluble outer layer in the form of a coating encapsulating the relevant reactants in the pellet. The reactants may in such an embodiment be present in a pure form included in the coating or may alternatively be present contained in a carrier material wherein the reactants and the carrier are enclosed by the coating. In a different embodiment the reactants in such a pellet may be distributed inside a water-soluble carrier material wherein the water-soluble carrier material dissolves slowly in the water masses when the pellets are placed in the relevant location that is to be rehabilitated to liberate the reactants as the carrier material disappears. Examples of coatings may be cellulose, carboxymethyl cellulose, carbomers, other water-soluble polymers of synthetic or natural origin. Examples of the carrier material may by chalk, gelatin, water-soluble polymeric materials, etc. The liberation rate of the reactive material from the enclosing material and/or carrier material will lie within an interval of from 12 hours to 5 years depending on the properties of the location that is to be rehabilitated, the type of environmental poison that is to be rendered harmless, the rate of leakage of the relevant environmental poison, the water solubility of the relevant environmental poison and other factors that may be considered by the person skilled in the art.

When producing pellets there are in particular three items that need to be taken into account:

The granulating material must not contribute negatively to the chemical environment that the pellets are to function in. It may e.g. be men- tioned that in the covering of mercury deposits organic substances should be avoided so that there is not produced organic Hg compounds. The time before the effect commences, i.e. when the contents of the pellets becomes available. This time is normally not critical, but should be able to be defined and also verified so that a possible effect on the environment may be taken into consideration.

The size and quality of the pellets. This is hardly critical for the movement of the reactive material down into the layer of coarse crushed rock provided the opening between the rocks is larger than 5 x the pellet diameter. In this consideration it is a prerequisite that the material density is larger than 1.5 in relation to sea water (practical and empirical tests may contribute to the understanding of the relationship between pellet diameter, specific weight and mobility). It should also be taken into account whether or not the external material of a pellet does not adhere or stick in an aqueous environment so that the distribution of pellets/viscous mass may proceed unhindered without any establishment of bridges in the bottom layer/layer of crude crushed rocks 2.

In an embodiment based on the notion that unreacted material/viscous mass is distributed without the use of crude crushed rocks, pellets may provide an advantageous use followed by e.g. a simplified distribution of following covering masses, e.g. with sand followed by plastering masses.

In an alternative embodiment it is also possible to mix the viscous material/pellets/rocks prior to this mixture being placed onto the sea floor. In such an embodiment the distribution of crude crushed rock may be simplified by it not being necessary to add the viscous material onto the top of the crude crushed rock since it may then be distributed together with the crude crushed rock. The crude crushed rock may in that case be dimensioned to a smaller size which will still function as a physical carrier of the new covering layers 4 and 5. The function of the mixed material (crude crushed rock and pellets) will have a corresponding effect on the polluting material in relation to if the crude crushed rocks were placed first end the viscous material was placed on top of it.

The present invention may in one embodiment be extended to after the layers of viscous mass and crude crushed rocks have been allowed to function over some time (normally within a time interval of one week to five years, even if longer time intervals also are possible). After such a time period to originally environmentally harmful/dangerous compounds may be bound or have reacted with the reactants in the viscous mass 3. Depending on the situation at each localization it may after this time be advisable either to remove the reacted material (to the extent that this might also constitute a lesser environmental threat) or it may be relevant to remove the viscous mass 3 to remove unreacted reagents that may be present in the particles of the viscous material or be present as unreacted pellets. In one embodiment it may consequently be relevant to perform the process according to the invention anew or optionally to remove the entire viscous material or the pellets for safe deposit elsewhere.

As an example of a relevant compound that may be advantageous to render harmless, it can be mentioned mustard gas. Mustard gas was produced inter alia by the Germans in the first and second world wars and wrecks of German war vessels are still supposed to contain canisters of mustard gas.

Mustard gas dissolves easily in mist organic solvents, but has a poor solubility in water. In aqueous solutions mustard gas decomposes into non-toxic products through hydrolysis. This reaction is catalyzed by alkali. However, only dissolved mustard gas reacts which means that the decomposition proceeds very slowly. Baking soda, calcium hypochlorite, and chloric amines react, however, quite powerfully with mustard gas, whereupon non-toxic oxidation products are formed.

In addition to containers with combat gases and other environmental hazards (e.g. mercury, organic mercury compounds or lead or organic lead compounds) sunken ships may contain heavy oil which should not be spread into nature. The composition of the reactants in the viscous material 3 is selected based on relevant knowledge about what kind of substance or substances that is/are to be rendered harmless.

On top of the layer 2 of rocks and viscous material 3 there is placed at least one further layer 4 comprising rocks of a diametric size within the interval up to 50 mm, e.g.5-20 mm. This second layer of stone has as a task to consolidate and secure the first layer 2 and particularly to protect the viscous material 3 so that this is not transported away with the current or is whirled up through the influence of waves. The thickness of this further layer 4 is not decisive for the function of the layered construction according to the invention, but normally its thickness may be 0.2-0.5 m , e.g. 0.3 or 0.4 m . Preferred and optionally there is placed on top of this layer 4 of rocks a third layer 5 of plastering mass such as sand covering the other layers. This layer 5 of plastering mass may form a foundation for sea growths to establish a normal bottom environment in the relevant area. In locations with strong currents and/or significant wave activity, the plastering mass may possess a large quantity of crude rock (up to 50% of the plastering mass based on volume, such as 5%, 10%, 15%, 20% or 25% based on volume). With "crude rock" it is in this connection meant rocks that have a diameter extending from grains of sand (0.5 mm - 5 mm) up to the size of crude crushed rock. The application of plastering mass 5 is not necessary but may have relevance in areas being exposed to currents and weather and in leads where it is a danger for larger ships of running aground. The thickness of the layer of plastering mass will normally lie within the interval of up to one half meter.

One possible embodiment of the invention will be more closely disclosed infra with reference to the enclosed figure 1 showing one example of isolation and rehabilitation of the area around the wreck of the submarine U-864 sunk at Fedje in Norway during the Second World War. This submarine transported a cargo of containers with mercury, and these containers now leak mercury 60 years after the submarine was sunk. This leak represents an environmental hazard.

Reactive mercury consists mainly of ionic mercury, whereas metallic mercury is more inert. It is consequently, for in a feasible way to inactivate the mercury chemically, advantageous to transfer possible mercury ions to a metallic, non- charged form, denoted Hg(0). Among other reduction substances 2-valid iron possesses the property of reducing mercury ions to metallic mercury, Hg(0). Furthermore, metallic mercury is very poorly soluble in water and may consequently be isolated and adsorbed after Hg(0) has been formed. The absorption of mercury may be accomplished by the fine-graded, amorphous iron hydroxide particles existing in the viscous mass 3. The viscous mass 3 may include hydroxides of iron, finely distributed olivine (magnesium silicate including two-valid iron), chalk, diatoma- ceous earth, etc.

When distributing the initial layer 2 of rocks over the wreck of U-864 the stone particles will cover the wreck per se and the adjoining sea floor, and will also penetrate into openings or create openings into the wreck where the hull has become weakened by damages and/or degradation. It may be considered if the hull of the submarine should be filled with crude crushed rock (mass 2) for preventing breakdown of the hull structure in connection with a further covering. Such a filling is terminated with the introduction of the viscous mass 3 as a precautionary measure against mercury leaking out from the inner sections of the submarine. Alternatively, viscous mass 3 may be introduced first followed by crude crushed rock or stone masses with a reduced particle size, depending on the operational conditions when filling. It may also be possible to introduce viscous mass 3 initially for subsequent filing with crud crushed rock and new viscous mass, as explained in connection with the embodiment supra. This to achieve both an initial binding/deactivation of the environmentally hazardous waste/ compounds and additionally obtain a further binding/reaction of such compounds/waste that has not been bound initially, but that will become bound and rendered harmless through diffusion through the layer of viscous material 3 including binding/reacting/absorbing substances.

The total amount rock in the initial layer 2 will depend on the thickness and spread of the layer. With a thickness of 1 m and a spread in a diameter of 200 m in a circle around the wreck, the amount will be about 31 ,400 m³. It may be considered that the room between the rocks in layer 2, crude crushed rock, represents about 30% of the total volume. The amount of viscous mass 3 will then represent about 10,000 m³. On top of these layers 2 and 3 it is distributed a layer of finer masses 4 of smaller rocks, e.g. at a thickness of 0.5m, and the volume of this layer will then be 15,700 m³. On top of these two layers there may be placed an additional layer 5 of a plastering mass to a height of e.g. 0.5 m, representing a volume of an additional 15,700 m³.

A second alternative layered structure for the covering masses according to the invention is shown in Fig.2. Fig.2 displays a layered structure of a cover over a polluted sea floor wherein the covering has been conducted based on each layer's intended function. In the figure it is also shown zones that each of the layers refers to. By starting at the base of the figure, zone I refers to a zone including the layers 6, 7 and 8, wherein each layer 6 represents polluted sea floor, layer 7 represents in-mixing into sediments of the sea floor and layer 8 represent necessary adaption to the terrain. Zone I represents that part of the covering that takes into account variation in thickness of the construction. In Fig.2 zone II comprises the layers 9, 10 and 11 wherein layer 9 indicates a chemical isolation layer, i.e. the layer comprising the viscous material mixed with the reactive particles (corresponding to layer 3 in Fig. 1), layer 12 indicates advection deep where each material or substance is to bind via advection. Layer 11 indicates a layer that may be regarded as a part of a new sea floor established below zone III. In this layer 11 there may occur some mixture of the water masses together with elements that are dissolved or are transported through the layer by diffusion. This is indicated through the aid of arrows showing a passive transport both to and from and being internal inside layer 11. Layer 11 may be indicated as a "bioturbation layer", in one embodiment as a bioavailable section of a newly established sea floor. On top of layer 11 , being the topmost layer in zone II, there is present zone III, where the function thereof is disclosed infra.

Zone II in Fig.2 represents that part of the covering structure that is to prevent transport (e.g. via diffusion and/or convection) of the polluting material (e.g. mercury). Furthermore zone III in Fig.2 includes the layers 12 and 13 wherein layer 12 represents a layer with erosion protection (e.g. rocks, corresponding to the layers 4 and 5 in Fig. 1) and reference number 13 represents the water masses above the layered structure. Zone III is to make up that part of the covering that protects against erosion. The layers in Fig.2 may have the same thickness as the corresponding layers in Fig. 1.

In fig 2 arrows represent an indication of the direction that the pollutants from the sea floor 6,7 may be transported through ach of the layers.

Fig.2 may be considered as an illustration of the conditions existing when covering sea floor that per se is not present as a deposit, but may also be regarded as an illustration of the conditions existing in pockets of stagnant water masses in bottom layers that may exist as a deposit. In this connection Fig.2 may in one embodiment be regarded as a particular case of the conditions existing after the placing of the layered bottom structure according to the invention. In one such example the area may be considered to be an example where there is little current or turbulence in the water masses, i.e. a stagnant location. In one such example an advection occurs in the surrounding water/water masses until the area has been closed and sealed. In this connection it will be explained that in the embodiment where it is relevant to talk about a stagnant deposit, the pre-working of the bottom becomes relatively unimportant since the addition of viscous mass 3 on top of the pollutants will represent the bottom layers, whereas the sides of the pool/excavation wherein the deposit is present are initially in place and in function.

In the disclosure supra there are used expressions such as "about" and other relative indications. To the extent that it is meaningful, these expressions are meant to indicate a deviation of +_ 10% of the indicated value. The indication of e.g. a thickness of "about" 5 m will give a thickness variation of +_ 0.5 m . The estimation of an area will also represent an element of uncertainty. The area that has to be covered is mainly determined through a field-determination of the extent of the pollution, and is a natural project establishment for the remedy.

The invention is disclosed supra in relation to a "sea floor". This indication refers to the bottom of salt-water-based as well as fresh-water-based areas since the invention is not limited to its use in salt water, even if it is probable that it is in salt water areas it is most probable that ship-wrecks exist that have carried environmentally hazardous cargos. At generally industrial activities including mining and rescue activities, there may have occurred deposits of environmentally hazardous materials in water masses downstream from the expelling locations for the relevant industry including onto river floors, at a river mouth and in lakes and inland seas. The type of water around the relevant deposits is not of significance for the use of the invention.

In the disclosure supra there is also referred to the "size" of stone goods particles. Such an indication refers to the diameter of the particles and will be considered to represent the largest dimension of the particles. Where it is also of significance to indicate the lower size of the particles, this is given in the disclosure, in addition to the limits for the larger particle size, by indicating the smallest acceptable dimension of the relevant particles as well. The size of e.g. the particles of the stone layer 2 is defined to be 100-200 mm to indicate the absence of particles in the layer below 100 mm. These could otherwise reduce the intended function of the layer.

To the extent that the relevant particles are not spherical, the indication of "diameter" refers to the largest diameter of a sphere included inside the relevant particle. It is considered to be a sufficient accuracy for the indication of stone goods size to use sorting criteria used in connection with the sales specification for crushed and sorted stone products. Deviations from cubical/spherical form are most critical in layer 2 since it here must be secured a free distribution of the subsequent viscous mass 3. In stone products with a large inclusion of flat stones, e.g. with a large inclusion of slate-like goods, the stone products become oblong and flat instead of the preferred cubical/spherical shape.

Addition of viscous mass, layers 3 or 9, is possible through pumping a pre-made sludge-like material in the specified consistency and composition from land locations or from surface vessels. The viscous mass 3 is put on top of layer 2, crude crushed rock, with the aid of a screened conduit that at its bottom towards layer 2 has adjacent flexible rubber flaps. The device is passed over a substantially plan surface of crud crushed rock, layer 2. The operation may possibly be repeated after some time to ensure that a sufficient amount of the viscous mass has been adequately placed inside of layer 2.

Loss of viscous mass 3 or 9 to the surroundings when distributing said mass must be considered with respect to environmental effect. Further actions may be considered if there must be used environmentally suspicious substances or reactants. Particularly for the case of the submarine at Fedje, where the suggestion includes the use of iron salts or hydroxides, this represents a very low environmental hazard, but represents still a local deviation from a natural aqueous establishment at the time of the distribution. The distribution of stone per se and also other covering steps, represents in principle deviations where a permit for the distribution must be obtained from the Department of Environmental Protection. This must also be included into the environmental considerations that must precede the practical solution that is to be conducted at Fedje.

When distributing a layer of crude crushed stone and other stone masses, it is also an advantage that such a mass is distributed with care so that no larger stone masses are dropped down uncontrolled to whirl up bottom sediments in the relevant area that is to be covered. Such bottom sediments may include the relevant environmentally polluting substances that are to be covered, so as little disturbance and movement of the original bottom material is preferred. The distribution of crude crushed rock, stone masses and viscous material and plastering mass as well is preferably conducted at as small a distance above the bottom as possible. Devices and methods for such distribution are known. There may e.g. be used corresponding methods as when casting concrete in sub-sea areas. One relevant method is to use a hose with a flap or skirt at its expelling end to avoid viscous mass to be whirled up when it is distributed.

Claims

Cl a i m s

1. Layered structure for the rehabilitation of sea floor in lakes or oceans in or about areas, pockets or stores (1) of environmental pollutants, said environmental pollutants being on the verge of leaking out to their surroundings,

c h a r a ct e r i z e d i n that the layered structure comprises at least one layer of mass on the top of said area with environmental hazardous material and including one layer of a viscous material (3,9) comprising sludge/earth/clay and including fine-graded particles impregnated with reactants that are able to react with the relevant environmental hazardous material(s) and bind and/or make these harmless.

2. Layered structure according to claim 1,

c h a r a ct e r i z e d i n that the viscous mass (3,9) including the fine-graded particles is present in the at least one layer as a filling material between rocks in a second layer (2) of rocks on top of the bottom with the relevant environmental hazardous material(s), said bottom layer (2) having a thickness of about 0.5 to 1.5 m and comprising rocks within the size interval 100-200 mm in diameter.

3. Layered structure according to claim 2,

c h a r a ct e r i z e d i n that the stones of the bottom layer (2) comprise stones being round or cubical of shape (crude crushed rock).

4. Layered structure according to claim 2 or 3,

c h a r a ct e r i z e d i n that the second layer (2) comprises rocks being a mixture of round, oval and edged rocks.

5. Layered structure according to claims 1 - 4,

c h a r a ct e r i z e d i n that the layer of viscous mass (3,9) including fine- graded particles impregnated with reactants, optionally as a filling material between the rocks of the bottom layer, is covered with at least one further layer (4,10) of a mass including rocks of a diametric size in the interval up to 50 mm.

6. Layered structure according to any of the preceding claims,

c h a r a ct e r i z e d i n that the structure comprises at least one further top layer (5,10-12) of plastering mass covering the other layers.

7. Layered structure according to claim 6,

c h a r a ct e r i z e d i n that the top layer (5,10-12) of plastering mass comprises sand and rock masses.

8. Process for rehabilitating the bottom in lakes and oceans at and about areas, pockets or stores (1) of environmentally hazardous materials, said environmentally hazardous materials being in danger of leaking out to their surroundings, c h a r a ct e r i z e d i n that it on top of the area comprising the relevant environmental hazardous material(s) is placed a layered structure comprising at least one layer of a mass being comprised of a viscous material (3,9) comprising sludge/earth/clay and including fine-graded particles impregnated with reactants that are able to react with the relevant environmental hazardous material(s) and bind and/or render these harmless.

9. Process according to claim 8,

c h a r a ct e r i z e d i n that the relevant area including environmentally hazardous materials, prior to the addition of the viscous material (3,9), is added an initial layer of viscous material comprising sludge/earth/clay and including fine- graded particles impregnated with reactants that may react with the relevant environmentally hazardous materials and bind and/or render these harmless, whereupon there on top of this material is added a layer of rocks, said layer of rocks having a thickness of between about 0.5 to 1.5 m and comprising rocks of a size of about 100-200 mm in diameter, and where it on top of this layer of rocks optionally is added further mass of viscous material comprising sludge/earth/clay and including fine-graded particles impregnated with reactants that are able to react with the relevant environmental hazardous material(s) and bind and/or render these harmless.

10. Process according to claim 8,

c h a r a ct e r i z e d i n that the relevant area including the environmentally hazardous material(s), prior to the addition of the viscous material (3,9), is covered with a bottom layer (2) of rocks being added on top of the bottom with the relevant environmentally hazardous material(s), said bottom layer (2) having a thickness of between about 0.5 to 1.5 m and comprising rocks of a size of about 100-200 mm in diameter.

11. Process according to claim 9 or 10,

c h a r a ct e r i z e d i n that it in the bottom layer (2) is included rocks being round to cubical of shape (crude crushed rock).

12. Process according to claims 9, 10 or 11 ,

c h a r a ct e r i z e d i n that the bottom layer (2) includes rocks being a mixture of round, oval and edged rocks.

13. Process according to claims 8 - 12,

c h a r a ct e r i z e d i n that the layer of viscous mass (3,9) including fine- graded particles impregnated with reactants, optionally added as a filling material between the rocks in the bottom layer (2), is covered with at least one further layer (4,10) of a mass comprising rocks with a diametric size within the interval up to 50 mm .

14. Process according to any of the claims 8 - 13,

c h a r a ct e r i z e d i n that it on top of the layered structure is/are added at least one further top layer (5,10-12) of a plastering mass covering the other layers.

15. Process according to claim 14,

c h a r a ct e r i z e d i n that the top layer (5,10-12) of plastering mass comprises sand and stone masses.

16. Process according to any of the claims 8 - 15 for rehabilitating sea floor including wrecks containing mercury,

c h a r a ct e r i z e d i n that it is added a viscous mass (3,9) including amorphous iron oxides/hydroxides, ground olivine (magnesium silicate with two- valent iron), chalk and/or diatomaceous earth.

17. Process according to any of the claims 8 - 15 for rehabilitating sea floor including wrecks containing mercury,

c h a r a ct e r i z e d i n that the viscous mass (3) comprises alkaline oxidative reactants such as bleach, calcium hypochlorite and/or chlorine amines.