601
Kalil WeJtmirvter Dredging
Group
nY.
Jea ltland
Project·
A.10lution
forthe
·
1ea
l1land Project·
A,olution
forthe
wa,te di,pO/QI problem.
June 1972801 Kalil WeJtmirvter Dredging Group nY.
20 Rosmolenweg, Papendrecht, HollandComposed by:
Industrial Waste Disposal (1.W.D.) N.V. 20, Rosmolenweg, Papendrecht (Holland) Hydronamic N.V.
Port and Waterway Engineers Project Development
34, Merwestraat, Sliedrecht (Holland) in close consultation with
Dredging Investigations Ltd.
Port Causeway, Bromborough, Cheshire, (England) and other member companies
of the Bos Kalis Westminster Dredging Group N.V. Copyrights are reserved by
Preface.
The continuing economic growth, which is indisputably of essential importance to our prosperity,
causes an increasing number of problems with respect to our environment. Inasmuch as the various industries work with units which grow steadily in size and
complexity and because traffic streams are increasing enormously, the necessary margin between living and working space in the areas which are already densely populated is often reduced to an unacceptable
minimum. In addition thereto, there is the problem of an ever increasing stream of waste material.
The consequences of these developments force themselves upon us daily to an ever increasing extent. Air, water and soil becomes more and more polluted and noise caused by motorcars, industries and aircraft is being experienced as a steadily growing nuisance.
Due to these rapid developments, the authorities, industry and the private individual become more and more convinced of the necessity of solving this very
complex problem with the greatest possible energy. As an international dredging and civil engineering contracting company, and in particular because of its
activities in the field of transportation of waste material, the Bos Kalis Westminster Dredging Group is frequently directly or indirectly faced with these problems. In our opinion, the solution is not be sought or found in curtailing industrial development, but rather in a direction, where in the first instance residentiaJ and working areas must be clearly separated from one another. Moreover, uniform standards must be
determined regarding the influence exerted on
the environment; and if such plants, by which pollution is caused, are situated in a somewhat isolated location such as an island, it would be possible to carry out regulations more efficiently.
In densely populated industrial areas, which often border shallow seas, the building of artificial islands
may, against the background of this philosophy, provide a solution for many of these problems.
Within this framework we wish to introduce the prospects of building such islands and, by means of this Report, combine information and ideas - a
substantial part of which is already known - in order to activate discussions.
The publication consists of two Reports. One deals
with the possibilities of a relatively small island, specifically designed and equipped for centralised
waste processing. The second part deals in a wider sense with the building of both small and large sea-islands. In preparing this publication we were greatly assisted by a large number of authorities and industrial organisations.
Parallel to our activities regarding the
study of the building of islands in the open sea, the Association Europeenne Oceanique - called Eurocean
for short- at the end of 1971 submitted to its members, including Bos Kalis Westminster Di-edging Group NV., for further development, a number of
projects connected with the utilization of the sea. One of these projects is the development of a large multi-purpose island in the North Sea.
As we are convinced that such large, often international projects can only be realized by joint effort, it is our view that the project presented will
initiate closer inter-Eurocean co-operation. In conclusion, we express the wish that this publication may activate the discussion on this subject and that it will result in the realization of such a project.
J. Kraaijeveld van Hemert Chairman of the Board of Directors
BOS KALIS WESTMINSTER DREDGING GROUP N.V.
List of Contents.
Page
Preface
.
1.
Introductory considerations.
91.1. The problem of waste processing 9
1.2. The advantages of centralised processing of waste
on a reclaimed island in the North Sea. 10
2. Types and quantities of
waste
in the
Netherlands.
122.1. Categories of waste and the present-day manner
of processing 12
2.2. Estimate of the quantities considered for
centralised processing on an island 16
3.
Possible lay-out of a plant for
centralised
waste
processing.
173.1. The technique of waste processing 17 3.2. Supporting and other activities 18 3.3. Facilities for the transportation of products 19 3.4. Staffing, housing and central facilities 20 3.5. Estimate of the site area required 20
4.
A design for a
waste
processing
island
.
21 4.1. Considerations concerning the location of a wasteprocessing island 21
4.2. Physical conditions in the area considered 21 4.3. General lay-out of a waste processing
island 23
4.4. The sea defence-constructions 25
4.5. Quays and harbour installations 26
4.6. Possible building method for the island 26
5.
Financial
and
economical aspects.
275.1. General 27
5.2. Building costs of the waste processing island 28
5.3. Summary of the exploitation 28
6.
Review.
301.
Introductory
considerations.
1.1. The problem of waste processing
A direct consequence of growth in prosperity is the ever increasing quantity of produced waste matter, for two reasons: The world increase in population causes an increase in the quantity of domestic waste matter, in addition to which the quantity per capita is also increasing.
Moreover, the enormous industrial expansion during the last decade involves a stream of waste matter which is growing in volume and is steadily changing as regards composition.
The disposal or processing of these waste matters in a manner justifiable from an environmental and technical point of view involves problems of a varied nature. Those in the Netherlands for instance, who intensively occupy themselves with pollution problems, will no doubt have come to the conclusion that no integral approach to this waste disposal problem has been arrived at, mainly, as a result of the following:
1. No adequate legal regulation governing waste processing is as yet in force and no standard require-ments have as yet been set.
2. The responsibility regarding the environment is spread over too many levels of governmental depart-ments and government-agencies.
3. The costs per production unit for the processing of waste matter is higher in the case of small industries than in the case of the larger industries which produce a more or less continuous stream of waste of a fairly constant composition.
4. Data regarding the quantity and the composition of waste which is produced in or transported through the Netherlands are not available.
5. Technical developments in the field of
bulk-processing of continuous streams of waste is noticable. Such a remunerable approach is not possible for residues or the more complex and varied small quantities of waste matter.
6. In many cases there is a preference towards a de-centralised processing because of opinions that the transportation of waste matter by road should be kept t'.) a minimum.
In view of this increase in the stream of waste matter - the destruction of which, already creates enormous problems because present methods are unable to fully absorb such increases - the establish-ment of new processing plants suitable for all types of waste matter is essential.
Such plants will have to satisfy stringent require-ments, both in regard to the environment and proces-sing and this can only be undertaken by a centralised approach, in which processing methods conform to principles as suggested by the .,Dutch Institute for the Removal of Waste Matter" (Stichting Verwijdering Afvalstoffen) and by authorities after inter-departmen-tal discussions.
This means a centrally directed, centrally inspected and, as a result an optimal processing treatment.
CATA DATA
REPORTS SUPPLIED
ANALYSIS AND RESEARCH DEPARTMENTS
rno1,1- STICHT,IIU \l[O\WIJD[RING ~FV~tSTOFFEll-llET><[Rl•rlDS ..
Fig. 1. Plan for the removal of chemical waste in the Netherlands.
These facts induced the authors of this Report to try to find a solution to the problem which would satisfy the following requirements:
1. The solution has to be as universal as possible and it must provide the possibility of processing all and
any type of waste produced and in unlimited quantities. 2. The solution should include centralisation in order to enable smaller industrial plants to share in the benefits provided by the enlarged scale of activities. The argument that road-transport of waste would be as dangerous as road transport of chemical
substances is not, in the authors opinion, justified.
If Regulations c.oncerning the Transport of Dangerous Substances are obeyed, waste matter can be
transported without difficulties or problems.
3. This study is strictly for waste processing as such but the solution must also include an economic method of application for the energy released in the waste processing to keep down the overall costs of waste-treatment.
4. The solution should technologically be the most advanced in its field and it should satisfy requirements regarding environment and optimal control.
5. The solution should be under the direct jurisdiction of Governments.
The disposal problems of local authorities and large industrial organisations can be, by such a solution, dealt with. In addition, such will also
encourage the establishment of new industrial projects. The solution advocated and presented in detail in this Report which is open for further discussion, is the installation of a central waste processing plant on a reclaimed island in the southern part of the North Sea.
The positive responses and support received from central Government, as well as from trade and industry during the period preceding the publication of this Report has been so encouraging that the realisation of such a project within a period of the next 4 to 5 years would seem possible.
1.2. The advantages of centralised processing of waste on a reclaimed island in the North Sea.
As appears from paragraph 1 .1. of this Report a large-scale universal and centralised waste .processing plant is a good solution for overcoming the present waste problems.
The advantage of such centralised processing is that in the case of large plants it would be possible to convert the produced heat into electrical energy; whereas in small de-centralised plants such heat can only be regarded as thermal pollution.
Such a plant will naturally have to be located so that it can easily be reached from waste producing areas. In the Netherlands and Belgium for instance, the bulk of waste is produced in the urban districts of Antwerp, Rotterdam and Amsterdam with its densely populated areas and industrial centres. The
establishment of such a plant could be located in the region between Antwerp and Amsterdam. Here various restrictions would obviously be imposed by municipal and provincial Authorities, for no Municipality would willingly accept such a large scale waste-processing plant within its boundaries, necessitating storage facilities and the intensive transportation of frequently dangerous substances.
Some people see an increase of risks by centralising the waste processing. The authors of this
Report are, however, of the opinion that such a concentration will assure the highest possible guarantees of safety, with the use of optimal equipment and the use of trained and experienced personnel. Such safety guarantees cannot obviously be from a de-centralised organisationpartly expected because of the costs involved.
If such a centralised installation is set up well away from residential areas, such risks would then be reduced to an acceptable minimum.
The installation of a waste processing plant on a reclaimed island in the North Sea provides these guarantees and, moreover, by-passes administrative difficulties, because the sea comes under the direct jurisdiction of a Central Government within the framework of International rules. Provincial and Municipal Authorities have then only the task of issuing regulations prohibiting the dumping of waste and the control of its delivery to the collecting sites.
Studies into the possibilities of using the energy released during waste-processing on an island located in the North Sea, revealed interesting factors. There would be, at such a location, the possibility of linking up with one or more of the natural gas belts, which are at present uneconomical' in production, to further exploit such supplies. Such a centralised process can
reach an optimum and be supplemented by other allied
activities that come within the bounds of possibility. The transportation to the island of waste matter suitable for centralised processing will create no problems for harbour facilities along the North Sea coasts could be used (fig. 2).
Such ports are adjacent to the principle waste producing areas and they maintain excellent road, rail and inland waterway links with the hinterland.
Looked at from an environmental and hygienic point of view such a centralised waste processing installation on an island in the North Sea, which obviously must satisfy requirements regarding air and water pollution, could offer many advantages over a similar plant set up on the mainland. The most important of these aspects are:
1. The clean air above the island does not present a danger arising from a combination with waste-gases of other origin - such as exhaust gases from motor cars - which may be far more detrimental than the original component or the reaction products thereof, (formation of smog).
2. A controlled storage of frequently dangerous waste substances outside residential areas due to the natural safety girdle around the island.
3. The nuisance caused by flue-gases containing acids and sulphuric dioxide which are always released upon certain waste substances being incinerated. In the case of incineration at sea this will be substantially less than on the mainland, inasmuch a these gases are discharged close to the surface of the sea, and they are neutralized by the slightly basic sea-water and thereby rendered innocuous.
58°00' 00"N 56°00' 00'N 8 g 0
+
+
0
,
,E/
~ ' ' , ' ' N , , 0 ( 10Drn ... , I I ' ''
I,
' I0
DOGGER ,..som, ' '0
' ' BANK1-
-- -:~
:.
I
~
-\
I ' , +++• INTERNATIONAL DIVISION CONTINENTAL SHELFQ
GAS FINDFig. 2. Central location of the area under consideration in relation to the large domestic and industrial areas around
the southern part of the North
Sea.
will only cause inconvenience on the island and not in the residential areas on the mainland.
5. The possibility of an optimal check on the process because of the isolated location of the island.
The advantages of chosing the southern part of the Continental Shelf as the site for the building of the
island are as follows:
1. The location is near to Western Europe where the
problems of removing and processing waste are most difficult in the Netherlands and in Germany.
2. The location will avoid long distance transportation
to the island as it is situated as favourably as possible to the ports of Antwerp, Rotterdam and Amsterdam, all of which are adequately linked with the hinterland by rail, road and water.
3. The location on the southern part of the
Continental Shelf where the sea is relatively shallow is from a civil-engineering point of view, more
attractive than the northern part of the Shelf, whereas
in view of the location of gasfields a not to southerly
location is preferable.
4. Building material, such as sand and gravel, needed in vast quantities for the building of the island, are
available on location.
5. Dutch civil engineers, amongst whom are civil engineers of the ,,Rijkswaterstaat", (Board of Roads and Waterways), already possess the experience and knowledge to accomplish such gigantic projects. 6. The southern part of the Continental Shelf offers favourable possibilities for activities allied to waste processing on such a reclaimed island, and, at a later
stage of island expansion, the setting up of independent
industries.
2. Types and quantities of waste
in the Netherlands
2.1. Categories of waste and the present-day manner of processing.
In this Report data about the waste production
in the Netherlands have been taken into consideration,
since in this phase of the study, only these data could
be made available.
The total amount of waste produced in the Netherlands was - especially where chemical waste
was concerned - greatly under-estimated until about
two years ago, when the Dutch Government and Dutch
Industry began making a joint effort to look for a
solution to the waste disposal problem.
The Report of the official inquiry instituted by the Dutch Government and Dutch Industry for the purpose of gaining an insight into the quality and quantity of industrial waste produced in the Netherlands provides data and figures necessary for dealing with this problem.
Upon the basis of publications and upon the basis of the information made available to them by a large number of industrial firms, the authors of this Report have prepared a rough analysis of the waste market which can be divided, in broad outline, into the following five categories: Domestic waste, industrial waste, (coarse waste capable of being disposed of by normal processes), chemical waste, scrap-metal (motorcar bodies etc.) and other waste matter. Domestic waste.
The total quantity in this category - consisting of
household refuse, some coarse waste, garden refuse,
sweepings and market waste and the like - normally
gathered weekly by the municipal refuse collectors,
at present aggregates approximately 4 million tons per
year.
This quantity is rapidly increasing and it is
estimated that its production will be 5 million tons
by 1980.
Three methods are at present being adopted for the disposal of this waste, namely:
1. Dumping-grounds. This method is to an increasing extent being objected to on aesthetic and hygienic grounds. Since there is no possibility of keeping a proper check on these dumping grounds, they are dangerous to the environment, especially as it is possible for all impurities and polluting substances to penetrate into surface and ground water. Further-more they produce a nasty smell. The total quantity disposed of in Holland in this way is estimated at
about 2 to 3 million tons per year, spread over about
one thousand dumping grounds.
2. Composting plants. The composting of household
waste is in fact a cheap and useful method of
treat-ment of this waste, and the capacity for such plants
to take an additional amount of this type of waste
exists, but the compost market may become saturated.
Moreover, the composition of household waste is
subject to changes and this creates serious problems,
--Here again this method causes a nasty smell. It is estimated that about¾ million tons of waste is annually processed in this way.
3. Incinerating plants. An increasing number of
Municipalities are now operating their own inciner-ating plants. These installations being generally small and not fully utilizing the heat generated, have the disadvantage of relatively high operating costs. There-fore, only the larger incinerating plants which can be combined with the generation of energy and the distil-lation of water can operate favourably. Roughly about ¾ million tons of waste are annually disposed of in this manner.
The following table presents a summary of the present costs in the Netherlands incidental to these methods,
including the costs of transportation.
dumping £1.25 - £1.50 composting £3.50 - £4.25 incineration £4.25 - £4.75
Coarse industrial waste.
The quantity of coarse, flammable industrial waste,
emanating from the larger factories and industries amounts to about 1 million tons per annum and it is to be expected that by the year 1980 these quantities will have increased to about 1.75 million tons per
annum.
Only the incinerating plant is in fact appropriate and suitable for processing of this type of waste, and the total costs incidental to this manner of disposal will be on the same level as the costs incidental to the burning of household waste, depending of course, on the state in which such waste is delivered.
Chemical waste.
Waste emanating from the chemical and petro-chemical industries, laboratories and industries using chemicals, oil products and the like in their manufac-turing process includes inter alia, volatile, explosive,
poisonous and aggresive waste substances, which are difficult for processing.
A determined part of the liquid chemical waste can be classified as the so-termed 'grey products', a group comprising of substances, (inorganic acids,
basics and salts), which can now be dumped at sea following agreement at the inter-governmental con-sultations in Oslo (November 1971), such permission being subject to conditions as determined by the Governments concerned. Although little is known about the present annual quantities, it is assumed that in the year 1980 the quantity of waste emanating from Dutch sources and to be disposed of in this manner will average 1 to 2 million tons per annum.
The costs incidental to the dumping of these so-termed 'grey products' at sea with specially designed craft is likely to vary between £2 and £6 per ton, including the costs of transportation to the port of loading. This costs can obviously vary by the nature and origin of the waste on the one hand and the dumping area on the other.
To the other category belongs that chemical 14
waste, both liquid and solid, which positively may not be dumped at sea. Here a distinction can be made between:
1. organic compounds, to be sub-divided into;
- solid substances, such as pharmaceutical products, and tar-products, etc., (about 1,000 tons per anam), - liquid products, such as effluent oils etc. (about 80,000 tons per annum) emulsion and so called slops,
(about 100,000 tons per annum) solvents, (about 10,000 tons per annum) flavourings residues
emanating from the paint industry, (about 1.000 tons); and waste emanating from the food-stuff industry, etc.
2. inorganic compounds, to be sub-divided into;
- solid substances, such as gypsum and other waste
-salts,
- liquids, such as acids, alkalis, salts and watery solutions with poisonous anions or with cations (about 100,000 tons per annum), or chemical slops
(about 80,000 tons per annum), etc.
3. special organic-inorganic compounds, to be s ub-divided into;
- chlorine-hydrocarbons (about 25,000 tons per
annum),
- sulphuric substances containing 80% sulphuric acid
and 20% impurities (about 40.000 tons per annum).
Universal methods for processing of these chemical waste products are as yet unknown. In the
past, incineration in the open air has taken place, such as near Amsterdam. The cessation of this processing method created tremendous problems for many industries, and as no new authorised disposal procedure has been introduced, it is assumed that these waste substances will be treated by the individual industries themselves, or that incinerating plants will be installed for the destruction thereof. To date a general and determined insight into this problem is completely lacking.
An exhaustive analysis of this category of chemical waste brought together at a central point will no doubt show that there are many technical,
financially attractive and hygienically justified possibilities in the processing of such waste.
These possibilities will, for the greater part, cease to exist in the event of waste being disposed of at many different individual locations.
Scrap, metals, (car-bodies and such like). In the Netherlands alone, over 150,000 scrap car bodies have to be disposed of annually and it is estimated that by 1980 this figure will increase to about 200,000. There are also vast quantities of old
appliances suitable for turning into scrap, such as refrigerators, washing machines and agricultural machinery, etc. Measures currently being taken for such disposal on both a local and regional basis have often little effect.
Other waste substances.
There are many other types of waste, such as: a) sewer sludge, emanating from domestic and indus
-trial waste puryfying plants.
c) waste substances emanating from breedings and slaughterhouses.
d) waste from hospitals.
e) debris and such like.
f) waste from the cleaning of ships not including the
slops mentioned before.
Apart from sewer sludge and waste originating from the agricultural industries, which totals about 0.75 million tons per annum and which will have increased
to over 1.0 million tons by 1980, these substances are
less suitable for a centralised processing and acceptable solutions will obviously have to be found for such disposal.
2.2. Estimate of the quantities considered for centralised processing on an island.
As outlined in Chapter 1, a centralised approach
WASTE CATEGORIES
MILLION
HOUSEHOLD WASTE TONS
ANNUALLY
COARSE INDUSTRIAL WASTE
"
CHEMICAL WASTE _ "GREY PRODUCTS" • "
-
ORGANIC COMPOUNDS " - INORGANIC COMPOUNDS " - CHLORINATED HYDROCARBONS"
AND OTHER SUBSTANCES D D
SCRAP METAL
- MOTORCAR BODIES, ETC EACH
OTHER WASTE MATTER MILLION
- SEWER SLUDGE AND WASTE TONS FROM THE AGRICULTURAL ANNUALLY
INDUSTRIES
to the waste processing problem is proposed and this
in turn implies a centrally situated and universal waste processing plant.
The quantities shown in Table 1, are the
result of an analysis of the waste situation in the
Netherlands of categories suitable for centralised
processing.
Household waste. In view of the anticipated heavy
increase in the volume of this category of waste and having regard to the fact that many dry dumping-grounds may be eliminated, it is estimated that by the time an island is available over 1 million tons per annum will qualify for centralised processing.
Cosrse industrial waste. The increase in the
produc-tion of this type of waste justifies, in the opinion of the
authors, the prediction that an initial capacity of
0.2 - 0.4 million tons per year for centralised pro
-cessing has to be reckoned with.
WASTE MATTER ESTIMATED
QUANTITY
PRODUCED IN HOLLAND FOR
1970 1980 PROCESSING ON ISLAND 4.0 5.0 1.0 1.0 1.75 0.2- 0.4 0.5-1.0 1,0 - 2.0 -> 0.25 0.1 - 0. 25 > 0.25 0.1 - 0.25 > 0.05 0.05 - 0.1
150.000 200.000 25 TONS PER HOUR
0 ,75 1.0
-D
SUBSTANCES MENTIONED IN "GREY LIST'; ANNEX II TO CONVENTION OF OSLO, NOVEMBER 1971
oo SUBSTANCES CONTAINING 80% SULPHURIC ACID AND 20% OTHER IMPURITIES
Table 1. Known quantities of waste produced in the Netherlands and an estimate of the quantities which may be
processed on the island. 16
Chemical waste. Upon the basis of the quantities mentioned in the preceding paragraph, the following
estimate has - with reserve - been made:
- organic compounds approximately 100,000 to 250,000
tons per annum.
- inorganic compounds, (exclusive of waste matters
of the 'grey' products), approx. 100,000 to 250,000 tons
per annum.
- chlorinated hydrocarbons and sulpheric acids,
approx. 50,000 to 100,000 tons per annum.
The total is therefore estimated at approx. 500,000 tons
per annum.
Scrap metals. The quantity of scrap metals, such as car
bodies, obsolete machinery etc., to be turned into
usable material will depend mainly on the final
con-ception of the waste processing plant.
It may be assumed that such a processing plant
could handle an initial capacity of 25 tons per hour.
Other waste substances. In the analysis of the
proposed solution and the relation to this category
of waste, only the possibility of centralised processing
of sewer sludge and waste emanating from the
agri-cultural industry, has been directly investigated in this
Report.
3. Possible lay
-
out of a plant
for centralised waste processing.
As stated in chapter 1 of this Report, the proposed
installation must work and be controlled to the
prin-ciples laid down by the Authorities. In accordance
with these principles, the waste-stream will pass
through a centralised reporting and information centre,
working in close co-operation with an analytical
research and process development laboratory (fig. 1,
page 9).
In this manner it will be possible to designate
optimal processing methods for the destruction by
incineration, the removal of poisons, the rendering of
waste into harmless compounds, and its recovery.
Such a large scale installation offers, moreover, the
possibility of turning the heat released by the inciner-ation process to good account. This heat can, for
instance, be converted into electrical energy or for
use for the distillation of sea water.
Furthermore, the energy released can also be
combined with various activities incidental to waste
processing, including air separation.
3.1. The technique of waste processing.
The Report being of a general informative nature, sets
forth no detailed plan for a waste processing plant
on a reclaimed island. The technique is therefore only
explained in broad outline.
The waste processing plant will consist, inter alia,
of the following units:
a. An incinerating plant, in which household waste
and coarse industrial waste will be processed. Here,
current types of incinerating installations are
envis-aged such as installations with rotating furnaces.
For gaseous liquids and powdered waste another
type of incinerator will be required and for chemical
waste releasing aggressive gas flues, the fluid-bed
incinerating technique is suggested.
The principle underlying this incinerating
tech-nique is that grains, (so termed 'carrier grains'), are
pressed upwards by a flow of gas, causing them to
whirl with speed to form a liquid like medium. The
material to be burned is then fed into the incinerator.
As previously mentioned in this Report, the
nuisance caused by flue gases containing acids and
sulphuric dioxide gases - which always occur when
determinate waste substances are incinerated - will,
in the case of incineration at sea be substantially less
than on the mainland.
As these gases are discharged close to the
surface of the sea, they will be rapidly neutralised
by the sea water. By this method chemical compounds
will be formed which, by nature, are already present in
sea water in great concentrations and which are,
therefore, to be regarded as harmless.
b. a power station, attached to the incinerating plant
will, in the case of the quantities of waste assessed in
paragraph 2.2, already have a theoretical capacity
of about 100 megawatts.
c. a department for chemical waste processing will
have special advanced and modern techniques that
will be applied for the processing of the various
types of chemical waste which is not capable of being
incinerated.
Here too, the fluid bed technique plays an
impor-tant task, inasmuch as it renders it possible to
thicken concentrates of heavy metals by evaporation
and to release them from the organic contaminations
interferring with the process of recovery.
The temperature in such a plant, can, within a wide range of possibilities be accurately maintained for the further application of this technique by selecting a
particular carrier grain and the combination of the
waste streams.
Furthermore, standard processes are envisaged,
such as distillation of oil solvents and some so-called
slops formed when barrels and tankers are cleaned; extraction (of 'slops' for heavy metals recovered from
metal concentrates) over-crystallisation, exchange
of ions, electrochemical processes and other methods.
In the case of these techniques the recovery of
products is given priority.
d. a scrap processing plant. In the processing of scrap and especially in the field of processing motor car
bodies, new techniques have been developed. Up to
now car bodies have been pressed to form blocks of
scrap metal, after being stripped of usable and
non-metal parts.
Such impure scrap is hardly of any use to the steel
industry, but, by making use of new techniques, ferro
-metals, non-ferro-metals and also organic material can now be separated. In this way scrap metal is obtained, which is far more attractive to the steel industry. The different separating techniques are:
- installations, in which car bodies and such like are
cut into pieces by a swing-hammer pulverizer and
subsequently separated by means of magnets and blowing devices, (so called shredders).
- The 'cold'-technique. In this process pressed and crumpled car bodies and such like are coolled down in
a tunnel and finally sprinkled with liquid nitrogen to
make them brittle for smashing up by a swing-hammer pulverizer, a method for which only a minimum of energy is required. Here the separation of ferro-metals,
non-ferro-metals and organic material forms part of
the processing technique.
The advantage of this technique is that the scrap
metal can be pressed together before transportation,
thereby cutting down transportation costs. The
required nitrogen could be obtained from an
air-separating plant to be built on the island and the
required power - about 10 megawatts for a processing
capacity of 25-tons of scrap per hour - could be supplied by the power station attached to the inciner-ating plant.
The organic material, inclusive of the organic material
of motor car tyres, could be processed in the
inciner-ating plant.
The efficiency of such a central waste processing
plant will mainly be determined by the scale of its
activities and it must obviously be possible optimally
to handle waste material of various types.
In this connection a constant production of energy
will be of primary importance and the fact that it is
cheap energy, means that it could be applied to many other activities related more or less to waste
processing.
Further to this, the possibilities of connecting the
island to the currently unremunerative natural gas
fields, located in the area under consideration is of
great importance. The exploitation of these, often
relatively small, natural gas fields is now regarded as less attractive than similar fields on the mainland. The connection of such a natural gas field to an island
located nearby ensures a constant supply of energy
on the island with the gas being of benefit to the
process of incinerating various types of waste.
3.2. Supporting and other activities.
As previously stated, the integral approach to the
problem of waste processing by means of the mentioned industrial plants will make possible and
motivate other activities, such as:
a. An air separating plant. The proposed scrap metal processing plant requires liquid nitrogen and the necessary quantities can be supplied by an air separating plant installed on the island, which could also produce oxygen.
If, in the processing of domestic waste, the newly developed technique of gasification with the aid of oxygen instead of the incinerating process is applied,
the island will provide a proper basis for erecting an air separating plant with a daily output capacity of about 1,000 tons of oxygen.
The electric power required for operating such a plant would be approximately 20 megawatts, the energy of
which could be supplied relatively cheaply by the power
station adjacent to the waste incineration plants. Such an air separation plant would require a site of at least
2 hectares. The quantity of gas released in the
gasification of waste process - roughly 50 m3 of dry
domestic waste with a caloric value of about 6,000 K.cal. - could on the one hand be used again for generating energy and could, on the other hand, offer an attractive starting point for the production of hydrogen, which in turn provides the possibility of
introducing other chemical processes (i.e. the
manufacture of ammonia). This gasification technique
makes it also possible for the process of the
trans-formation of natural gas and other hydrocarbons. The air separation technique is also suitable for use in the
liquifying of natural gas.
b. Fresh Water Plant. The energy and heat produced on the island could also be used for the manufacture
of high-quality industrial process-water.
Compared with river water, sea water is highly
suitable for this process because it is of a constant composition and contains practically no volatile and colloidal organic substances. Taking as a basis, the energy which can be generated during the waste
incineration process, (set out in paragraph 3.1 of this
Report), it would be possible to produce about
20-million cubic metres of distilled water per annum.
c. Tankcleaning, storage of oils and chemicals.
There is a definite requirement for a fully equipped
harbour adjacent to the Dutch/Belgian coast, where it
is possible for large oil tankers to take shelter when
in distress, (a so-called damage repair harbour). In
such a harbour tankers carrying oil or chemicals could
---undergo provisional repairs, after which they could proceed to their destination without any danger to the environment.
The temporary storage of oil and chemicals would
require the building of a tankfarm.
Moreover, before carrying out small repairs the
tanks from which the cargo had been discharged could be cleaned. The steam required for this tank-cleaning
could be in ample quantity available at the waste processing plant.
The processing of the 'slops' would be no problem,
in contrast to the situation at the existing tankcleaning
plants at, for instance Amsterdam and Rotterdam,
where the 'slops' give rise to big problems.
If there was such a tank-cleaning plant installed on
the island, ships that require cleaning would be
encouraged to come to the plant for this special purpose, specifically because de-gassing at this
off-shore location does not present so many difficulties as
on the mainland. With a location close to the main shipping routes tankcleaning on the island will be stimulated and will diminish cleaning on the North Sea by the ships themselves.
d. Gas liquification. In addition to the use of natural
gas as a basic fuel for a power-station, the construction of a gas-liquifying plant may open up further favourable
perspectives.
The construction of long and, by consequence, very costly pipelines to the mainland could then be
avoided in as much as the liquid gas could, in that event, be carried by a special tanker, (a so termed
'LNG-tanker'), direct from the island to, for instance, the rapidly growing North-American market.
Moreover, it is from a safety point of view, essential
to keep these tankers away from the busy shipping
routes and harbours.
e. Other activities. An island in the North Sea, with several basic facilities, such as energy in the form of
electricity or gas, the industrial process water and oxygen, in addition to deep navigating channels may
attract industrial activities, other than those mentioned
above. The fact that waste produced on the island would be processed could be a main factor for the
introduction of other industrial activities.
In addition, the possible construction of a drinking water transhipment station is possible. High quality drinking water, imported from other countries in large
floating containers, could then be pumped from the
island to the mainland. A Norwegian plan provides for
an average daily supply to the Netherlands of about
1 million m3 of drinking water in one large flexible
container.
These containers, having a draught of at least
20 m, will by means of a pumping station and a sub-marine pipeline, have to be emptied into water reser-voirs on the mainland.
There is on the island adequate space for such a
pumping station, while, moreover, the energy required for the pumping of this water could be supplied at
relatively low cost.
Centralised processing of sewer-sludge into a
hygienically reliable organic fertiliser is also possible.
The energy in the form of electrical power and heat
needed for this process can be supplied by the incinerating plant.
Finally the island could be used to advantage in
several other ways such as the stationing of
sea-going tugboats; the installation of aids to navigation; the establishment of a meteorological station; and a beam-transmitter for international communication uses.
3.3. Facilities for the transportation of products.
As already stated, waste products suitable for processing will have to be conveyed to the island from
ports along the North Sea coast, the idea being to
transport the waste by water, rail, road or even by
pipeline to a number of these ports.
Necessary storage capacity should be available
at these ports for the building up of larger quantities
of waste to ensure economical transportation and for
facilities during possible delays in sea transportation.
Regarding household waste, coarse industrial waste and car bodies, etc., it is essential that these
categories of waste should be, as far as possible,
delivered at these points in a continuous stream, as is
currently operated by composting plants receiving waste from all parts of the Netherlands by rail. Owing to the often voluminous character of this
waste it requires to be ascertained as to what extent
volume-reducing processes can be applied.
During the convenance to, and the storage at these sites, very rigid regulations concerning safety,
supervision and the influence on the environment have
to be complied with.
For the subsequent transportation of waste products to the island, sea-going means of transport will have to be used, suitable for many types of waste such as, for instance, gases, liquids, household waste,
car bodies and the like.
This will undoubtedly mean that a number of ships
will have to be built, specially designed for this
purpose.
In this connection a recently developed system
of sea-going push-barge-units is envisaged, it being, of course, also possible to use conventional types of vessels.
The conveyance of dangerous chemical waste substances must, of course, be made subject to
stringent safety regulations. It might, for instance, be considered to transport these substances by means of specially constructed containers whereby the risks -which are particularly great in the case of loading and
unloading - are reduced to a minimum. This method
not only provides a better guarantee during transit,
but these containers can also serve as a conveyance
from the place where the waste is produced.
It is essential for this island to have good harbour
facilities with sufficient safe quays for unloading ships
and furthermore necessary that it satisfies adequate
nautical requirements.
For transhipment of dangerous chemical waste
substances a dock is necessary which can be closed
off from the rest of the harbour, to ensure no pollution
of the surrounding sea-water during any emergency or calamity.
Suitable unloading facilities will have to be available on the quays and the harbour should also
have safe berthing facilities for ships that are awaiting for unloading.
Tugs will continuously have to be stationed on the island to assist the ships that are being loaded or
discharged.
For some products, such as scrap metal, the same
transport can be used for transport both to and from the island, whilst for other products, such as distilled water and oxygen, the construction of pipelines may be considered.
This, however, will depend largely on the scale of the
enterprise and the location of the island.
3.4. Staffing, housing and central facilities.
The proposed waste processing plant will require
continuous attendance and supervision.
For this purpose a specialised, highly qualified staff
will have to be engaged, working for the major part in
shifts.
Analytical chemists, physicians, analysts, mechanical
engineers, trained operators, firemen, maintenance
teams, dockworkers etc. will be required.
For this staff and possibly for their families,
suitable housing accommodation and central facilities
pertaining to a small community, will have to be
provided.
The transportation to and from the island will take
place by ship and partly by helicopter, which
necessitates the construction of a small heliport.
3.5. Estimate of the site area required.
A rough estimate is given of the size of the site
areas required for several waste producing plants and
other activities.
These estimates are stated in table 2.
The plant for incinerating household and industrial waste:
Taking into consideration possible future expansion
and certain storage facilities, the site area required
for the waste incinerating plant is estimated at about
5 hectares.
Plant for processing chemical waste:
A like estimate shows that this plant will also require
a site area of about 5 hectares.
Storage spaces.
Certain waste substances - transported to the island
or emanating from the processing plant on the island
-will not immediately require further treatment.
The site area needed for temporary storage of these
materials is estimated at 1 hectare.
The scrap-metal processing plant.
Inclusive of storage facilities and taking into account
possible future expansion, this plant will need a site
area of approx. 2 hectares.
20
1. INCINERATING PLANT 5 HECTARES
2. CHEMICAL WASTE 5 " PROCESSING PLANT 3. SCRAP METALS 2 " PROCESSING PLANT <{ 4. DUMPING SITE 1 "
w
er:
5. ADDITIONAL PLANTS 10-15" <{ • PLANT FOR THE SEPARATION OF AIR • FRESH WATER PLANT
w
• GAS LIQUIFICATION I- PLANT -(J) 6. CENTRAL FACILITIES 3- 6 " AND RESIDENTIAL AREA 7. INFRASTRUCTURE 4-6 "AND QUAY SITES
TOTAL 30-40
"
HARBOUR
10-15"
TOTAL AREA
OF
APPROX. 50"
THE
ISLAND
Table 2. Estimate of the area required for an island
with waste processing plants.
Allied industries.
For the activities mentioned in paragraph 3.2, which
are more or less tied to the waste processing plant,
an effective site area of 10 to 15 hectare_s has been
reserved.
Central facilities and housing.
The site area required for central facilities - including
housing for the staff, storage areas for the
mainten-ance of the island, heliport, etc. - will be approx. 3 to 6 hectares.
The total effective site area will be between 26 and 34 hectares. It is estimated that quays, roads,
pipelines and cables will require an additional 15%
to 20% of the effective site area, making an aggregate
gross site-area of 30 to 40 hectares.
-4. A design for a waste processing island.
4.1. Considerations concerning the location of a waste
processing island.
The choice of the location of a waste processing
island in the North Sea is determined by many factoi-s,
including economic, civil engineering, legal and other .aspects.
From the economic point of view it will on account of the costs of transportation, be essential to take into
consideration, in addition to the cost determining
factors relating to the building of the island, the
distance between the island and the principal
popul-ation and industrial areas.
The location in relation to natural gas sources in the North Sea may also be of importance.
On the Dutch part of the continental shelf some gas
-finds have been made, the majority being situated north of latitude 53°. If exploitation of these sources
is considered for energy supply on the island, this island should be situated as closely as possible to these sources, so as to avoid the necessity of long
pipelines.
Viewed from the environmental angle it would
seem desirable to situate the island at an adequate
distance from the coast, so that the population areas will experience no nuisance whatsoever from the
island. In this connection distances of at least 25 to 50
kilometres are envisaged.
From the civil engineering point of view the
location of the island is determined to a considerable extent by the construction-depth, which substantially affects the building costs. In the event of the island being built in open sea, currents and wave-heights will, in view also of the conditions prevailing in the North Sea, have less influence on the selection of the location.
In addition to the above described factors, brief reference is made here to the location of the island
in relation to important shipping-routes, with a view
to the stationing of sea-tugs for the purpose of rendering aid or assistance to ships and the like. Moreover, the location in the vicinity of the shipping-routes will, if an enlargement of the island is contem-plated at a later stage, be of paramount importance. Also, in the event of drinking-water being brought to
the island in large plastic containers with a draught
of approximately 20 metres, it will be necessary to have deep navigating channels.
Various other factors could be listed, such as, the establishment of beam-transmitters on the island and
the installation of nautical position determining
systems which will also influence the definite
selection of the island's location.
Finally, mention must be made of the legal aspects
involved in the location of the island.
At this stage it is not therefore possible to accurately determine the location of the island.
However, in order to be able to determine to some
extent the basic conditions underlying the design of
this island, a fairly large area - shown in fig. 2,
(page 11) and fig. 3 (page 22), in the southern part
of the North Sea - has been considered.
4.2. Physical conditions in the area considered.
The conditions relating to the design will not be
the same for every part of the area considered
be-cause of the area being fairly large. For the purpose of
this preliminary study, the most important conditions for the entire area have been taken as a constant
basis. To confirm these basic conditions the results
of further investigations, as described in detail in the
other part of this publication have been applied.
Depth: A study has revealed that the depth varies
from 20 - 25 metres below Mean Sea Level (MSL), and in the vicinity of the Brown Ridge limited areas occur where the depth is less.
For the island under consideration a depth of 20 m
has been assumed.
Soil Conditions: The bottom of the entire area consists of an upper layer of young sea-sand, the thickness of this layer averaging two metres or more. Only in the vicinity of the Brown Ridge and on the so-called Brown Ridge-bed does this upper layer
show any loss of thickness. This Brown Ridge area consists of a fresh water deposit of very resistant clay-layers. At all other places in the area considered
the layers under the young sea-sand consists of
pleistocene sand, alternating with thin silt and clay
layers. In respect of the possible settling of the island,
the study has not revealed the presence of compres-sible layers in the area concerned.
rr
- '-, -... .;,G,,.~ \'
'-0
'
~c,, \ \. __, / 1-:,,-,, / N 00
5 J' 00 ----,--N \ \ \ \ (\
\
l
I /I
I I / / \ -SIZE OF ISLAND OF 1000\ HECTARES BASED ON SGf LE OF DRAWING\
g T ) /0
0 0L
Fig. 3. The area considered for the building of a waste processing island.
22
s
E A ,:_ _, / ( / ~ ✓ / / '!/
'
/
_l
L.S. TEXEL / ~ I 3°00 Nv'
OEN HELCER \...· i +++•+•
•
0
DEPTH CONTOURS IN METRES RELATING TO L.L.W.S. LIMITS OF DUTCH CONTINENTAL SHELF POINT OF MEASUREMENT OF TIDAL CURRENT LIGHT SHIP GAS FINDWater-levels. In the area considered the
water-level is determined by the movement of the tide on
the one hand and by the wind effects on the
water-level on the other. Because of the special ground
plan of the North sea, a basin enclosed on three
sides, tidal motion arises which propagates anti
-clockwise along the coasts of the southern part of
the North-Sea. In the middle of the North-Sea, on
about the same latitude as IJmuiden, there is a
so-termed amphidromic point, which is an area where
the tidal amplitude is almost nil. In the area considered
for the construction of the island, situated between
this amphidromic point and the coast, the tidal
amplitude will, therefore, be less than the tidal
amplitude along the Dutch coast. This amplitude may
be assumed to be 1 to 1.25 metres.
The effect of the wind on the water-level is
determined to a considerable degree by the depth of
the water and, of course, by factors, such as the
duration of the wind, the wind force, the direction of
the wind and the fetch. In this connection the
effects of the wind will at places where the sea is
deeper be less than the wind effects in the vicinity
of the shallow coastal areas.
With regard to the case under consideration it
has been assumed that water-levels of rare
occur-rence will be approximately one metre lower than the
water-levels at Hook of Holland. For the purposes of
the design of the island a water-level has been
assumed which occurs 10-4times a year, namely
M.S.L.
+
4.00 m.Currents. The current-picture in tne area under
consideration is determined by the tidal movement in
the southern part of the North-Sea. As a result
elongated stream roses arise in the area concerned,
these stream roses having been given in the other
report for four locations near the area considered.
These data show that the main direction of the tidal
current runs parallel to the Dutch coast. In the area
considered the maximum ebb and flood velocities
during spring tide will be between 0.75 and 1 m/sec.
and at neap tide approximately 0.50 m/sec. The vel
o-cities in a north to north-east flowing tide are
some-what greater than in a south to south-west flowing·
tide. The course of the tide is approximately sinuous.
Waves. Wave-heights have besn determined with
the aid of observations on board the I ightships
'Goeree' and 'Texel' and upon the basis of known
relations between observed and significant
wave-heights. The area considered lies west of both
lightships and the waves coming from an easterly
direction will, therefore, be larger than those observed
on board the lightships, this being due to the larger
fetch from that direction.
In the case of a water-depth of about 20 metres a
wave of 8 to 10 metres in height from a westerly to
northerly direction has been assumed for the
pur-poses of the design at a water level of M.S.L.
+
4.00metres.
For the east-side of the island a significant
wave-height of approx. 5 metres has been set, in
combina-tion with a waterlevel of M.S.L.
+
2.00 metres.4.3. General lay-out of a waste processing island.
For the various activities described that are to be
carried out on the waste processing island, a gross
surface of about 30 to 40 hectares will be required
(table 2), exclusive of the area required for the harbour
basin.
The shape and the arrangement of the island are
determined by various factors, these factors being,
inter alia, the requirements which the harbour must
satisfy and the hydraulic conditions.
The harbour. The number and the size of the
vessels which will put in are determined by the
nature and the volume of the products which are to be
brought to the island or - as the case may be
-carried to the mainland from the island.
Upon the basis of the quantities of the various
types of waste mentioned in table 1 that annually
require to be processed, it has been established that
the harbour must have mooring and berthing
facilities for 4 to 5 ships. Moreover, a determinate
quantity of dangerous waste will be brought to the
island for processing at the chemical waste
proces-sing plant, and for that purpose it must be possible
to separate - in the case of calamities - a part of
the harbour at the place where the chemical waste
processing plant is situated from the rest. In this
connection the use of a dock might be envisaged.
Regarding the size of the vessels, ships of up
to 5,000 tons and approximately 100 metres in length
are envisaged.
As for the type of vessels which will call at the
island nothing definite can be defined at this stage
of the investigation. Such could include existing
ships and also push-units, such as so called.
Artibar units, having a capacity of about 3,000 cubic
metres per unit. In connection with the currents and
the waves around the island the vessels will have
to enter the harbour at a certain speed, which will
require the possibility of a determinate stopping
dis-tance. A harbour length of 500 metres wil I be sufficient
for this purpose. At the rear, the harbour will have
to be approximately 200 metres in width, so as to
enable the ships to swing round, and, furthermore,
the depth of the harbour must be at least 8 m.
The harbour-entrance must be situated so that the
currents and the waves around the island cause the
least possible inconvenience to the vessels berthed in
the harbour. For that purpose the south-easterly side
of the island would be preferable.
The shape of the island is - in addition to the
requirements respecting the arrangement and lay-out
of the waste processing plant - to a very substantial
degree determined by the local physical conditions,
and that in particular, by the currents and the waves.
An elliptical shape with a longitudinal axis in the
direction of the main current, being more or less
SW-NE, would, examined from a hydraulic point of
view, appear to be the most suitable. Deflection of
the courses of the current will in that event be
limited to the least possible extent, as a result
where-of erosion where-of unprotected parts where-of the immersed talus
and of the sea bottom in the immediate vicinity of the
,---
.
I I I I 1 -1 ' I I - - -- -i--- -1 I I I I i . _ ____,.,.. A / ' -1 ~ -/ ---(--
... ~u
f, I 'r-... I I ... r I ' -/ '--1 ''
I ' I " I I I I ' I / / 0 o ' -- - -- -- -MS. L. -8/-10 m_
,
· -- - - I ,I-
... -....__I f--
,
I ~ - - - - _/ I INCINERATION I - - -- --·1 I / WASTE S~REAT:L~1 ' • @@PROCESSING®®
Pl.A~T
J ALLIEO INOUSTRIES MS.L.+5m.0000
0
FACILITIES RESIOENTIAL ANO/ ~
~
/ ''
/
/
/
/
/
rr
~
~\ \
I I I _f_I
I
\
\
\
\
:.- ✓ / / / 1 / / - - - - I \ \ \ \/ / ~' I I I I I I ' I I I I \ \ \ _,,.,. J I I I I 1 1 I \ , . / -.... I I I I I I \ , - .,.. --. ___ , I I \ \ 1.---.!.. __ / L-_L-- 100 I - - - ---7 I - - -- - - - 1 I I -- ---
,
- - -,
I-...
/
- ... 1 I I I 200m.Fig. 4. Lay-out of the proposed island for centralised waste processing.
island will be limited to a minimum. Figure 4 shows a possible shape and lay-out of the waste processing island, in the case of which, the aforementioned requirements are satisfied to the greatest possible degree.
Giving regard to the dominating wind forces, the chemical waste processing plant has been situated on the north-eastern part of the island.
The plant for the processing of the household and coarse industrial waste which is supplied in rela-tively large quantities, can best be erected along the side of the harbour. On this same area will be built the
power station attached to the waste incinerating plant.
Because the water-distillation and the scrap processing plant will to a substantial degree, make a direct use of the energy liberated from the incineration of waste, these two plants have been situated beside
the above mentioned processing plant.
The central facilities and the housing accommo-dation are, with a view to the dominating wind
directions, planned on the south-westerly part of the
island. As has already previously been stated, the harbour entrance is planned on the south-easterly part. In the vicinity of the harbour-entrance admini s-trative buildings and a beam-transmitter could be erected and tugs, life-boats and the like, stationed.
Finally, south-west of the scrap processing plant some space has been reserved for other industrial activities not as yet specified.
4.4. The sea defence-constructions.
The main constituent substance of the island will be sand, a material which in the part of the North Sea considered is available in large quantities. It has been assumed that the island will be elevated with this material to a height of M.S.L.
+
5.00 metres. This height has been fixed upon the basis of the frequencies of high-water levels on the one hand and of the criteria which, on the other hand are adopted, recently, in respect of reclaimed industrial sites.DOUBLE LAYER
I
I
~
-
LAYERS OFI
I
I
GRAVEL AND QUARRY STONE< 11~~~~
I
I •The defence of such a sand-island against current
and attacks by waves has been widely reviewed in
the other report, because the costs incidental to the defence construction, will in the case of relatively
small islands positively constitute the major part of
the total building costs.
In this connection four possibilities have been examined, namely, the unprotected beach profile, the partly defended beach profile by means of groynes, a sea-defence consisting of concrete blocks, quarry stone and gravel and a sea-defence construction with the aid of caissons.
In respect of the unprotected beach profile it has, upon the basis of the known relation between the slope of the beach profile and the average grain dia-meter of the sand, and upon the basis of the
investi-gation made of the beach profiles along the Dutch
coast where the average diameter of the sand is in
excess of 0,2 mm, been found and establishe:l that for the island under consideration slopes of 1 : 50 or less are required.
In the case of such a faintly sloping talus and in
the case of an island having an area of no more than some tens of hectares the quantities of sand-required for the immersed talus per running metre shore-line is
so large that the costs incidental to the construction
of a beach will be of the same order of magnitude
as the costs incidental to the construction of sea-defences with concrete blocks or caissons. In addition, an unprotected beach profile will require regular main-tenance in connection with erosion caused by current and waves.
Calculations have shown that on the western side
the average annual loss of sand per running metre
of shore-line may be in the order of 103 m3 .
-Capitalization of these maintenance costs shows
that a defence consisting, inter alia, of quarry stone and concrete blocks is a better solution for the waste processing island, also in relation to the beach profile partly defended by means of groynes.
From provisional calculations it appears that in
the case of a construction depth of 20 - 25 metres
a sea-defence with the aid of caissons would be a more expensive solution.
The principle of the defence construction selected for the westerly and northerly sides of this island is
bs¾
x\"'
":
··
·.
·
.
. ·
.
···•··
··•···
·
·
·
··
··
..
.
.
... ·
.••·•••·<;.\
·xt<;;
~E.ABE.9.
)J.-::;;;;
Fig. 5. Sea defence-wall for the proposed island for centralised waste processing.
