terra-et-aqua-78-complete.pdf - IADC Dredging

International Journal on Public Works, Ports & Waterways DevelopmentsNumber 78 • March 2000

International Association of Dredging Companies

Terra et Aqua – Number 78 – March 2000

Terra et Aqua is published quarterly by the IADC, The International Association of Dredging Companies.The journal is available on request to individuals or organisations with a professional interest in thedevelopment of ports and waterways, and in particular, the associated dredging work.The name Terra et Aqua is a registered trademark.

EditorMarsha R. Cohen

Editorial Advisory CommitteeH.A.J. Fiers, ChairmanH. van Diepen H. De Vlieger H.W.J. PoieszK. de Groot R. Vidal Martin P.G. RolandP.J.A. Hamburger F.A. Minderhoud H. Cami

IADC Board of DirectorsR. van Gelder, President O. Nakagome, Vice President C. van Meerbeeck, TreasurerP.G. Roland M. Montevecchi G. VandewalleD. Eicke J.J. Koeman

Please address inquiries to the editor.Articles in Terra et Aqua do not necessarily reflect the opinion of the IADC Board or of individual members.

© 2000 IADC, The NetherlandsAll rights reserved. Electronic storage, reprinting or abstracting of the contents is allowed for non-commercial purposes with permission of the publisher.

ISSN 0376-6411

Typesetting and printing by Opmeer Drukkerij bv, The Hague, The Netherlands.

Front cover:

Although much attention has been given to the new jumbo trailing suction hoppers, the development ofcutter heads that are able to withstand extreme wear and tear has also been essential for the excavation ofhard rock in places such as the fixed bridge-tunnel links in Scandanavia.

IADCP.J.A. Hamburger, Secretary GeneralDuinweg 212585 JV The Hague, The NetherlandsTel. 31 (70) 352 3334, Fax 31 (70) 351 2654E-mail: [email protected]://www.iadc-dredging.com


2 Editorial

3 Dredging: Opportunities and Challenges for 2000 and Beyond

John Riddell

Large investments in technology and equipment have transformed dredging into an innovative and dynamic industry.

11 The Use of Agitation Dredging, Water Injection Dredging and Sidecasting:Results of a Survey of Ports in England and Wales

Nicola Sullivan

This year’s IADC Award winner examined the hydrodyanamic dredging techniques used in ports and harbours in the United Kingdom.

21 Determining the Ages of Recent Sediments Using Measurements of Trace Radioactivity

Hewitt W. Jeter

Geochronology analyses are used to characterise sediments and sedimentationrates which can help in planning dredging operations.

29 Books/ Periodicals Reviewed

Proceedings of two important conferences — one held in The Netherlands and one inDenmark — are evaluated, and the second edition of Dredgers of the World is published.

33 Seminars/Conferences/Events

The new millennium starts with a water conference in The Hague, moves on to Singapore,Turkey, China and around the world, with a “Call for Papers” for WODCON XVI to beheld in Malaysia.


CO N T E N T S


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EDITORIAL

The old year has changed over into the new millennium, and activities in thedredging industry have not skipped a beat. Major works are being executed,important tenders for large projects are on offer, and state-of-the-art equipment is being built. The growth of the last decade is continuing.

The economies of scale persist, not only in the new equipment being commis-sioned, but in the enormous efforts being made in research and development ofplant, as well as environmentally safe methods of dredging. Joint ventures havebecome more and more necessary — both to execute major projects more effec-tively as well as to share the risks. The modern dredging industry seeks to find abalance between risk and reward.

Privatisation of dredging works has also increased, for it is too costly for nationsto build their own state-of-the-art fleets which they then only use intermittently. Inmany cases — for instance, New Zealand, Mexico and Argentina — ports are nowwilling to contract private dredgers like IADC companies to maintain and deepentheir waters. IADC companies are dedicated to providing the most cost-efficientmeans of dredging. They have also realised the necessity of informing their clients,and the populace at large, as to the economic advantages of dredging. As JohnRiddell points out in his article on page 3, “Contractors now appreciate that anunprepared client is not a blessing....”

To that end, the IADC sponsors training seminars such as the course held everyMarch at the Institute of Hydraulic Engineering (IHE) in Delft, in Singapore andin Buenos Aires. In addition, the IADC Award is granted annually to the bestpaper by a young author presented at a major conference (see page 11). Our hopeis to attract the best and brightest professionals to the dredging industry. To meetthe challenges before us, we can ask for no less.

Robert van GelderPresident, IADC Board of Directors

tion industry. Over the last two to three decades theindustry has faced huge challenges -- challenges bothto provide increased benefits and services to its cus-tomers and challenges to its perceived impact on anincreasingly fragile and sustainable-vulnerable environ-ment. The industry has risen to these challenges. Byvery substantial investment in plant and equipment, bythe development of new methods and techniques, byresearch and training, and through a growing realisationof the importance of communication, the world'sdredging industry is well placed to enter the new mil-lennium.

Like ports, dredging is a service industry. Its develop-ments and innovations are thus largely responses tothe needs of its customers and in turn the pressuresput on these customers by other external influences.The dredging industry of today is truly international. Itscustomers and their needs are constantly changing.The type, scale, location and purpose of dredgingprojects are far from uniform, and may not even bepredictable more than a few years ahead. What thenare the opportunities and challenges for the dredgingindustry beyond 2000?

Abstract

Dredging today is a service industry, yet it has oftenbeen underestimated or misunderstood. The mainconcerns have been environmental issues such as thedisturbance of contaminated sediments, turbidity whiledredging, and disposal of dredged materials. Today’s dredging industry has met the challenge andhas carefully addressed these issues with large invest-ments in technology and equipment. Consequently, atthe start of the new millennium, the opportunities forenvironmentally sound dredging are increasing steadily.This article is adapted from the Keynote Address pre-sented by the author at the Coasts & Ports ’99 Confer-ence, held in Perth, Western Australia, in April 1999.The Conference was organised by the Institution ofEngineers Australia and was followed by a dredgingshort course which attracted many participants fromthroughout Australia and New Zealand.

INTRODUCTION

There are many aspects to both coastal and port andharbour engineering. All are important. It has to berecognised, however, that few of today’s ports wouldhave been developed, or indeed would continue toexist, without the activity of the dredger. Whether it beinvolved in creating a new harbour, maintaining a chan-nel or creating new land for port development, thedredger plays a vital role (Figure 1). Yet the moderndredger and the dredging industry of which it is themost visible part is relatively rarely regarded as favoura-bly as might be expected from the benefits it brings.The public perception of dredging is low and whendredging does attract media attention it may well be inan adverse light. Even among port professionals --including civil engineers -- dredgers are little under-stood, their capabilities not fully recognised and theirpotential not always appreciated.

Yet the dredging industry of today is one of the mostdynamic and innovative areas of the modern construc-

Dredging: Opportunities and Challenges for 2000 and Beyond

John Riddell

Dredging: Opportunitiesand Challenges for 2000and Beyond

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Dr John F. Riddell is a Professor in the Department of Civil Engineering,University of Strathclyde, Glasgow,Scotland (UK), where he specialises inWater Engineering. He is a well-known lecturer on dredging.

John Riddell

THE ENVIRONMENT

It is difficult in any discussion of dredging today not tostart with the challenges presented by a world with anincreasing awareness of and concern about the envi-ronment. Our seas and waterways constitute a verylarge part of that environment. The potential of theoceans for all forms of future advances -- medicine,food, minerals -- is far from understood, while recre-

ational use of the sea continues to grow. Dredging bydefinition takes place in that water. Thus the opportuni-ties for dredging to disturb, interrupt and even destroythe water environment are high.

Concern about the environmental impact of dredgingcan be divided into three main areas. The first is thedisturbance of contaminated material, the secondturbidity and the third is material disposal.

Contaminated sedimentContamination of the sediments lying on the bottom ofa harbour or channel is not caused by the dredgingindustry, or even in most cases by the ports. It is caused by industry, by agriculture and by human beings.It is the result mainly of historic ignorance and some-times of greed and negligence.Yet these contaminatedsediments often require to be dredged. The resultingdisturbance may then produce the potential for thepollutants to re-enter the water column or otherwisespread.

The recognition of contaminated sediment and itsproblems is relatively recent. Whether it be tin fromantifouling paints in a marina or chromium from somelong-abandoned tannery, the impact of disturbance candamage both the marine environment and humanhealth.

The dredging industry has responded most effectively

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Figure 1. The premier project of the last decade of the last century was most likely the massive development of the container terminal and airport platform of Hong Kong.

Figure 2. Close up of a specially developed environmentalsweephead.

developed world can now afford. The care and concernof the dredging industry when operating in that worldmay be something of which all involved can be proud.But is it too much of a challenge for the industry toapply the same standards of care in those many coun-tries where the environment is still far down the list ofbasic concerns? If turbidity is controlled in Rotterdam,New York and Sydney, should it not also be controlledin all locations where the dredging industry now findsits work?

Material disposalThe disposal of dredged material has traditionally beenachieved by dumping in the sea. But the environmentalacceptability of ocean disposal of even clean sedimentis being increasingly questioned and opposed. There isalso a growing awareness that dredged material can beregarded as a resource rather than a waste, with possi-ble beneficial uses. With maintenance dredging, theremoval from the estuarine or coastal circulation zoneof large volumes of natural sediment inflow is also nowregarded as unsustainable.

to the challenge of removing and disposing of contami-nated sediments. It has funded research and developednew techniques and equipment (Figure 2). It can nowclear, relocate and, if required, treat most forms ofcontaminated sediment. It has developed expertise ofa high professional standard. In the process it has alsocreated a new and valuable business opportunities.

TurbidityAlthough most concern still relates to the quality ofdredged material, there is growing awareness of thepossible physical impacts of the dredging and disposaloperations. The sediment dredged may be quite pris-tine in terms of quality, but its loosening, lifting andtransporting can result in significant amounts of mate-rial entering the water column. Both through lightreduction and subsequent settling, this can have anadverse impact on marine life -- and on public percep-tions. The smothering effect of fine sediment on coralis perhaps the most obvious example, but there aremany short-, medium- and long-term changes -- somepossibly beneficial but all changes -- which may followthe disturbance caused by dredging activity.

The challenge of minimising the production of suspend-ed solids has been accepted by the dredging industry.There are now numerous examples of projects wheresensible and informed discussion between those withenvironmental concern and responsibility, those wishingto dredge, and the dredging industry has resulted inspillage being controlled to agreed parameters. Spillmanagement and monitoring formed a significant partof recent major dredging projects in Hong Kong, inVictoria, Australia, and on the new Øresund crossingbetween Denmark and Sweden (Figure 3).

Again, meeting the challenge has resulted in newknowledge, new techniques and new equipment.Enclosed, "no spillage" grabs are now commonplacewhile sophisticated turbidity measurement and monitor-ing equipment able to give real time data to the dredgeris in regular use. As with contamination, the dredgingindustry is not always unhappy with tight environmen-tal controls. So long as the rules of the game are clearlyestablished in the contract, the additional costs ofcontrol and monitoring can offer enhanced businessopportunities.

Such is the investment in environmental technology bythe dredging industry that some may say that theindustry now has a considerable interest in maintainingenvironmental awareness. This is coupled with anincreasing projection of a "green image" by many of thecompanies and organisations involved in dredging, asevidenced by their advertisements and other promo-tional material.

Environmental concern in relation to dredging, likemost environmental concerns, is a luxury which the


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Figure 3. Research vessel Maritina monitored the effect ofdredging on the ecological conditions in the Øresund.

Figure 4. The cutter suction dredger Castor, at work in theØresund, is equipped with innovative anchoring systems andprecision excavation control.

For all the foregoing reasons increasing attention isbeing given to the acceptable disposal or relocation ofdredged material. With granular material there aremany satisfactory alternatives to sea disposal. Benefi-cial uses include the obvious reclamation and beachnourishment. Less clear is what can be achieved withthe finer cohesive sediments which form a large pro-portion of many maintenance dredging projects. Whererapid drying can be achieved the possibility of use forreclamation may exist, but otherwise the options todate have generally been limited to some form ofenvironmental enhancement. The creation or rechar-ging of mangrove areas and saltmarshes using dredgedmuds is now well established, but there are obviouslimits to how much dredged material can be used insuch ways.

OPPORTUNITIES

The dredging industry is primarily reactive. The develop-ment of specialist equipment and techniques for tack-ling contaminated sediments was a response to therecognition of contamination in material which neededto be dredged. The construction of heavy-duty rockcutter dredgers for port projects in the Middle East andAustralia was a reaction to the physical and financialcharacteristics of these locations. The development ofhighly efficient maintenance dredgers was a responseto the need to contain port operating costs.

World trade continues to develop. No viable alternativeto the sea transport of thousands of containers and

tens of thousands of tonnes of bulk cargoes are yet inprospect. Ships may for the present have stoppedexpanding in terms of draft, but the need for newharbours and the expansion and maintenance of exis-ting ones does and will continue. Such development istotally dependent upon dredging. Thus what might betermed conventional harbour dredging -- whether of a marina, ferry terminal, fishing harbour or containerport – is likely to continue steadily if not dramatically.

Construction activitiesWhere the greatest opportunities now exist in dredgingis work to support construction activity. There arenumerous examples of such activity and each haspresented new challenges for the dredgers involved.Below-water tunnel construction, for example, is nowpredominately achieved by immersed tube techniques.These involve the accurate excavation of the containingtrench, often in hard material. The Øresund Tunneltrench required the use of a large cutter suction dredger with innovative anchoring systems and precision excavation control (Figures 4 and 5). The lessons learned in such projects will be applied byboth designers and contractors to future immersedtube tunnels.

Pipelines and cablesThe increasing number of pipelines and cables laid onthe sea bed also provides new dredging opportunities.These lines have to be placed in a trench, backfilled andprotected. Water depths are frequently far in excess ofany required for safe navigation. Routes are often in themost exposed and hostile seas. How do you dig a

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Figure 5. Cutting through hard rock demands specially developed cutter heads that can withstand incredible wear and tear.

these twin goals of increased production and reducedunit costs have resulted in major changes in both thepredominant types of dredger and within the typesthemselves.

Trailing suction hoppersThe most obvious change has been in the develop-ment of the trailer or hopper dredger. This type ofdredger is now used for all forms of capital and mainte-nance dredging, and particularly for land reclamation.The requirements of the latter for vast volumes ofsand, often mined from deep water far away from thefill site, have resulted in the rapid expansion in size ofthe hopper dredger. This growth has been most spec-tacular in recent years with the advent of a number ofso - called "jumbo" trailers with hopper capacities inexcess of 20,000 cubic metres. Developed to recovermaterial, haul it long distances and place it ashore atthe lowest possible cost, these large and sophisticatedvessels now dominate the international dredging scene. In just over a decade their maximum capacityhas more than doubled, and is set to treble in 2000with the introduction of a 33,000 cubic metre "mega"trailer (Figure 6).

The development of the large hopper dredger was aresponse to the increasing scarcity of easily-won fillmaterial. In meeting that challenge, however, thevessels have also presented opportunities. The dredgingindustry is now able to undertake reclamation projectsrequiring hundreds of millions of cubic metres of material, and to undertake such projects in realistictime scales and at affordable prices. This was simplynot possible twenty years ago. Thus developers, fromnational governments to financial institutions, can nowconceive of and realise reclamation projects which inthe past would have occupied every dredger in theworld for many years. In the large trailer hopper dredgerthe dredging industry has provided a powerful newconstruction tool for the world’s civil engineers to use.

Specialised equipmentOther developments in dredging equipment have beenat the opposite end of the scale. Here the need has

trench for a 1 m pipe in 80 m of water, bury the pipeand then cap the trench with stone? The dredgingindustry has provided the solution by the developmentof very deep dredging hopper dredgers and stoneplacement vessels.

Land reclamationThe greatest opportunities for the international dredgingindustry are in land reclamation. The creation of newland for industry, transport, housing and recreation are now priorities for many countries. Singapore, forexample, can only expand if its land area expands; theonly possibility is to create new land from the sea. Thereclamation projects currently under discussion aroundthe world are staggering in their magnitude. Theyinclude a new airport for Holland in the North Sea andmajor industrial sites off the coasts of most Far Easterncountries.

Reclamation is fine so long as a sufficient volume ofsuitable material can be found to create the platform. It is here that the problems start. Sand deposits con-veniently located to the reclamation areas are beingdredged out. Thus the need to go further afield, to go to deeper water, or to reach for sand lying belowmud or clay. These problems are tackled by new equip-ment. Deep suction dredgers able to recover sand from100 m water depths or from below overlying cohesivelayers are one solution. Where the material lies atsome distance from the fill area the design criteria notonly look at the recovery but also the transport andplacement.

DREDGERS

At the start of the twentieth century the bucket ladderdredger still ruled supreme. It could be found in virtuallyevery harbour in the world engaged in both capital andmaintenance dredging. Today the bucket ladder dredgeris a quite rare machine. It has been replaced by cuttersuction and trailer suction hopper dredgers able todredge greater volumes of material in shorter timesand at lower costs. In the development of the dredger


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Name of Dredger Company Year Built Hopper capacity (m3)

Lelystad Ballast Nedam 1988 10,000JFJ De Nul Jan De Nul 1992 12,000Pearl River Dredging International 1994 17,000Gerardus Mercator Jan De Nul 1997 18,000Amsterdam Ballast Nedam 1997 17,000WD Fairway Boskalis Westminster 1997 23,000Volvox Terranova Van Oord ACZ 1998 20,000Queen of the Netherlands Boskalis Westminster 1998 23,000Queen of Penta-Ocean Penta-Ocean Construction 1999 20,000Vasco Da Gama Jan De Nul 2000 33,000

been for specialist dredgers to handle relatively smallquantities of material. This may be contaminated sedi-ment from a canal or former dock which needs to beremoved without releasing sediment to the watercolumn. Thus the development of such machines asauger and scroll dredgers which can feed in-situ mate-rial into a suction mouth at high concentrations andwith minimum solids resuspension (Figure 7).

Advances in instrumentationFor any dredging to be efficient it is imperative that thedredger removes only that material which needs to beremoved, or which the contractor is being paid toremove. This has resulted in very great advances insurveying and positioning techniques.

Differential global positioning systems using satellitesand shore stations are now standard in dredging andsurveying for horizontal control, and increasingly forvertical control. Positional accuracies of better than 0.5 m for not only the dredger but more importantly thedredging equipment – grab, cutter head or draghead –ensure that unwanted and unpaid dredging is reducedto a minimum.

Advances in underwater surveying have also beendramatic. The conventional echosounder with its singletrace of at times smudgy black lines has given way tomulti-beam, movable beam sonars with full colourdisplays. These provide three-dimensional views of thesea bed and can guide the dredger in real time throughthe work area.


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Figure 6. Trailing suction hopper dredgers have doubled —and will soon treble — in capacity from those of some 10,000cubic metres capacity built only a decade ago, such as theLelystad (left under), to the jumbos of today (clockwise):Gerardus Mercator, Pearl River, Amsterdam, (opposite page)Queen of the Netherlands and WD Fairway. Right under, theVasco da Gama (33,000 cubic metres capacity) is scheduled tobe delivered this year.

Further advances in instrumentation mean that everyaspect of a dredger’s performance can be monitored.This allows production to be maximised, minimises thecauses of disputes and enables researchers anddesigners to optimise loosening, lifting and transportingtechniques. Today the performance of a dredger caneven be monitored in real time from within the dredgingoffice on shore.

PLAYERS AND PRIVATISATION

The very large capital investment required to constructand operate modern dredging equipment has resultedin a steady consolidation of the companies and organi-sations able to play the game. This has happened onthree levels, albeit for the same reasons.

The most obvious contraction has been in the directlabour dredging organisations. Fifty years ago it wascommon for most ports to own and operate their owndredger or dredgers. The numbers doing so in 1999have fallen substantially as the investment required fornew plant has been diverted to more revenue earningdevelopments such as quays, container cranes andbulk terminals. Thus contract dredging has become thenorm with the dredger only being hired in when deepen-ing or maintenance is required.

A second level of consolidation has been in the nationalfleets. This is most noticeable in the United Stateswhere much of the dredging formerly undertaken bydredgers owned by the US Army Corps of Engineers isnow carried out by private (but US only!) contractors.Other countries, most notably India and China, stillretain large national dredging fleets, but it would not beunreasonable to predict that beyond 2000 will see theprivatisation of even these extensive state organisa-tions.


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The third level of consolidation is within the large inter-national contractors. These companies are the trueprofessionals of dredging. They operate throughout theworld and will tackle all kinds of dredging projects. Todo so they must invest in new dredgers and newtechnology. The vast cost of such investment hasmeant that only the strongest, or those considered tobe the strongest, have survived. There has thus been aseries of amalgamations, takeovers and both agreedand forced mergers so that today only a few largecompanies dominate the international dredging market.How long these will continue to remain independentwill be interesting; already most have to go into jointventure to resource and fund the mega reclamationprojects on offer today.

LEARNING

For many years dredging was a somewhat secretiveindustry. The private sector contractors saw little togain by informing others of their projects, problems ornew techniques. The industry was also insular andinward looking. Those involved tended to stay withintheir companies and there was little interchangebetween contractors, clients and consultants.

Much of this has now changed. Contractors nowappreciate that an unprepared client is not a blessing,but a source of endless conflict. There is still commer-cial confidentiality, especially about production methodsand rates, but the availability of knowledge nowextends rapidly. The Western, Central and EasternDredging Associations, for example, have done much

to encourage conferences, workshops, publicationsand courses. The International Association of DredgingCompanies, while clearly promoting the interests of itscontractor members, supports educational and trainingcourses and funds a quarterly publication as well asbooks and pamphlets on dredging.

Conclusions: 2000 and Beyond . . .

The dredging industry at the start of the twenty firstcentury can be considered to be in excellent shape andin good heart. The recent investment in new equip-ment and technology has meant that dredging costs,adjusted for inflation, have held steady, bringing greatbenefits to world trade. The industry now has thecapability to undertake the full range of work whichmay be required in coastal engineering construction, inharbours and in inland waterways. These develop-ments have opened up new opportunities and enabledprojects to be tackled which a few decades ago werejust dreams.

The environment will continue to present challengesand opportunities for the dredging industry. Dredgersdo not make harbour muds contaminated, nor does thedemand for efficient and competitive international tradecome from the dredging industry. If sediments fromunderwater have to be removed and relocated, a bal-ance has to be struck between the potential benefitand the potential adverse impact. The dredging industryis happy to participate in that debate and continues todevelop its experience, knowledge and technology toprovide acceptable solutions.

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Figure 7. Specialist dredgers such as this auger dredger at work in the harbour of Delfzijl, The Netherlands handle smaller quantities of sediment but are equally important.

Nicola Sullivan

The Use of AgitationDredging, Water InjectionDredging and Sidecasting: Results of a Survey of Ports in England and Wales

The author wishes to thank Dr Lindsay Murray who hasbeen working in the field of the environmental impactsof human activities on the oceans for 25 years. DrMurray currently works for the CEFAS — an Agency ofthe Ministry of Agriculture Fisheries and Food (MAFF)— where she heads the Regulatory AssessmentsTeam, whose responsibilities include advising MAFF onthe issue of licences for the disposal of dredged mate-rial at sea for England and Wales, and development ofpolicy on dredged material disposal. In addition to theabove, the paper draws on CEFAS’s experience ofmarine construction operations and presents views onthe impacts of sidecasting.

This paper was originally presented at the CEDA Dredg-ing Days, Amsterdam, The Netherlands, in November1999 and was published in the conference proceed-ings. This revised version is reprinted with permission.

INTRODUCTION

At the present time, the disposal of dredged material atsea in the UK is regulated under the Food and Environ-ment Protection Act (FEPA) 1985. In England (and onbehalf of the National Assembly for Wales), FEPA isimplemented by the Ministry of Agriculture, Fisheriesand Food, who operate a licensing procedure. FEPAdoes not cover the dredging operation per se. There isno single act regulating dredging operations in the UK,although control of some (but not all) operations isexerted the Harbours Act 1964 or its local equivalentsand the Coast Protection Act 1949.

To require a FEPA disposal licence, sediment has to beremoved from the seabed and re-deposited from a

Abstract

The Centre for Environment, Fisheries and AquacultureScience (CEFAS) carries out a diverse range of scienti-fic research, advice and monitoring into aspects of themarine environment. The Regulatory AssessmentsTeam work within CEFAS to provide expert scientificadvice to the Ministry of Agriculture, Fisheries andFood on the impacts of the disposal of dredged mate-rial at sea. Disposal of material at sea in the UnitedKingdom, is regulated by the Food and EnvironmentProtection Act (FEPA) Part II 1985. The day-to-dayprovision of advice is informed by research and monitor-ing programmes. Presently, dredging methods thatinvolve relocation of sediment by means other thanphysical removal and deposition elsewhere are notregulated under FEPA. This paper presents the resultsof a recent review into the use of hydrodynamic dredging techniques in England and Wales.

A questionnaire was sent to 250 ports, harbours andmarinas in the study area. The response was encoura-ging, with 42% of consultees submitting completedquestionnaires. The responses were both geographical-ly widespread, and representative of the study area.

More than a quarter of respondents claimed to employhydrodynamic dredging techniques. However, only11% of respondents use these techniques as their solemethod of dredging. All but one of these ports aresituated on the south coast of England. The Reviewalso queried which conventional dredging methodswere employed, what consultations were undertaken,and the environmental impacts of these activities.Several site visits provided a practical aspect to thereview and allow the presentation of case studies.

The Use of Agitation Dredging, Water Injection Dredging and Sidecasting

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vessel, floating container or pump. There are a numberof dredging methods which result in the relocation ofsediment by physical pushing or agitating, but which donot involve deposit directly from a vessel. Dredging anddisposal of sediment using these methods is not cover-ed by the existing legislation.

The aim of this paper is to provide an indication of thecurrent practice regarding dredging in ports, harboursand marinas located on the coasts of England andWales. The extent of use of the different types ofconventional dredging methods will be discussed, butthe main focus of the discussion will be the extent ofthe use of dredging methods from which the disposalof material is not licensable under FEPA. The originalsurvey of ports referred to these techniques as "non-FEPA-licensable dredging techniques"; however,for the purpose of this paper, the term hydrodynamicdredging (CEDA, 1998) is appropriate.

A questionnaire "A Review of Dredging Techniques"was sent to 250 ports in England and Wales. Reci-pients were selected using existing records of past andpresent holders of licences to deposit dredged materialat sea, published lists of UK ports and other resourcessuch as Yellow Pages. To ensure that the results werean accurate representation of the use of hydrodynamicdredging techniques, it was important to include portsthat do not hold licences to deposit dredged material atsea.

The response to the questionnaire was positive with42% of ports submitting completed questionnaires.The data was compiled and analysed with the aid ofdatabases, spreadsheets and a geographic informationsystem.

PRESENTATION OF RESULTS

The questionnaire was divided into four sections. Theresults of each section are presented below.

Section 1: Background information about respondents

Section 1 aimed to establish the location of theresponding port and details of current licenseddredging quantities. Of the respondents, 55% claimed to hold a currentlicence to dispose of maintenance dredgings at sea.These licence holders were well distributed representingall sections of the coast. Disposal licences are for varyingquantities, from 1,000 wet tonnes (Minehead) to>19,000,000 wet tonnes (ABP Humber). Figure 1 showsthe quantities of material disposed of by respondingports. The major ports of the Tyne, Humber, Harwich,Cardiff, Bristol and Liverpool are immediately obviousfrom the map. The map also suggests that many portson the south coast require relatively little dredging.


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Nicola Sullivan (center) was presented the IADC Award by MrPeter Hamburger (right), Secretary General of the IADC, withW Dieter Rokosch of CEDA assisting.

IADC Award 1999

Presented during CEDA Dredging Days ’99,at the Europort ’99 ExhibitionAmsterdam, The NetherlandsNovember 18-19 1999

At the CEDA Dredging Days, from November 18-191999, Ms Nicola Sullivan was presented with theannual IADC Award for young authors. Ms Sullivangraduated from Imperial College, London in 1997with a first class honours degree in EnvironmentalGeology. She subsequently gained employmentwith CEFAS (Centre for Environment, Fisheries andAquaculture Science) where she works within ateam performing risk assessment on the deposit ofmaterials at sea and providing scientific advice to theMinistry of Agriculture, Fisheries and Food (MAFF).She is also studying part-time for a MSc in Coastaland Estuarine Management.

Each year at a selected conference, the InternationalAssociation of Dredging Companies grants an awardto a paper written by a young author. The PaperCommittee of the conference is asked to recom-mend an author who is younger than 35 years ofage and whose paper makes a significant contribu-tion to the literature on dredging and relatedfields.The purpose of the award is "to stimulate thepromotion of new ideas and encourage youngermen and women in the dredging industry".The IADCAward consists of US$1,000, a certificate of recogni-tion and publication in Terra et Aqua.

ted areas, backhoe and grab dredgers are mostsuitable.

– Availability of contractor/vessels: The dredging opera-tion needs to be timed to coincide with the availabili-ty of the contractor. Smaller ports tend to use localcontractors in order to minimise costs.

The majority of responding ports (55%) employed acontractor to carry out the dredging process, against20% of ports operating their own vessels (Figure 3).A small number of ports (9%) own a vessel for dailyupkeep, whilst employing a contractor for large-scalemaintenance campaigns.

At the time of the enquiry, few ports held currentlicences to dispose of material at sea from capitaldredging operations. The main respondent was CardiffBay Development Corporation with a quantity of>500,000 wet tonnes.

The survey of material types found that silt was themost common surface sediment in ports, although onthe south and west coasts, sediments also consistedof fine sands and shingle. The material found at depthwas variable according to location and included silt, stiffclay, gravel, boulder clay and rock.

Section 2: The use of conventional dredgingtechniques

The questions in Section 2 covered conventionaldredging methods employed by ports.The most popular conventional dredging methodemployed by ports is the trailer suction dredger; closelyfollowed by the backhoe and grab dredgers. None ofthe port operators replying to the Review employ adipper or bucket ladder dredger and only a small num-ber make use of a cutter suction dredger (Figure 2).

There were three main reasons cited for the choice ofdredging plant employed:– Water depth: Backhoe and grab dredgers are limited

to relatively shallow waters whilst trailer suctiondredgers can remove material from deeper water.

– Accessibility of area: Trailer dredgers are used todredge large areas as they require adequate workingspace to complete a turning circle. For use in restric-


13

Figure 1. The location of responding ports and quantities of material disposed of to sea.

Figure 2. Popularity of conventional dredging plant.

Nearly all of the responding port operators stated thatthere were no noticeable environmental effects asso-ciated with, or following, the dredging campaign. Only15 port operators (14%) stated that turbidity increasedduring the dredging campaign.

Section 3: The use of hydrodynamic dredgingtechniques

This section obtained information on the use ofhydrodynamic dredging techniques.Twenty-seven percent of respondents to the Reviewclaimed to use hydrodynamic dredging techniques,with the plough/bed leveller being the most popular(Figure 4). The ports employing these techniques arewidely distributed around the coast (Figure 5).

The main uses of the bed leveller are to move materialfrom inaccessible areas into the path of the main

dredging plant and to level the peaks and troughscaused by trailer suction dredgers. Most port operatorsfound it difficult to define the quantities of materialinvolved, but where estimates have been made, theseare shown in Figure 5. ABP Goole and Fleetwood bothredistribute significant quantities of material, >50,000wet tonnes pa, using bed levellers in addition to licensed(dredging and) disposal operations.

Hydraulic dredging methods, which include vesselpropeller agitation and water injection dredging (Figures7 and 8), were used by 10% of respondents.

Some port operators (10% of respondents) use hydro-dynamic techniques as their sole means of dredging.Most of these are located on the south coast of Eng-land and the quantities involved are small, <5000 wettonnes pa. The other area that employs only hydro-dynamic dredging techniques is the Burnham YachtHarbour on the River Crouch, Essex with redistributionof >30,000 wet tonnes pa.

Experience indicated that the major limitation of hydro-dynamic dredging techniques is a loss in effectivenesswith increasing quantities of material removed.

Encouragingly, 80% of respondents stated that theywould, in the future, perform some form of environ-mental impact study and consultation prior to commenc-ing dredging using hydrodynamic techniques. The scaleof the studies would depend upon the scale of theproposed dredging activity, as EIA is expensive and oneincentive for using hydrodynamic dredging methods istheir relatively low cost.

Section 4: Comments

Section 4 provided the opportunity for comparison ofconventional and hydrodynamic dredging techniquesand for any further comments.A third of respondents declined to comment, feelingthat they had no experience of one or other dredgingtypes. The majority of larger ports indicated that hydro-dynamic techniques are less successful as a lonemethod of dredging, but can be most useful whenused in conjunction with conventional methods.

For many small ports, it is claimed that hydrodynamicdredging is the only cost effective way of maintainingwater depths. Many small operators commented thatthey would be forced to close if any restrictions wereplaced on techniques such as ploughing.

A comment made by many ports was that hydrodynam-ic dredging techniques can be successful with the levelof success depending on the operation and the manyvariables associated with a port (area, geography,topography, material and so on).


14

Figure 3. The percentage of respondents using contractorsand/or port-owned vessels.

Figure 4. The types of hydrodynamic dredging techniquesused by respondents.

The use of hydrodynamic dredging techniques can beclassified into two groups: 1) sole use and 2) use in conjunction with conventional dredgers.

In general the smaller ports tended towards sole use,whilst larger ports used hydrodynamic techniques todredge areas inaccessible to their main dredging plant,or to level areas following a dredging campaign (Figure 7).

One further use of hydrodynamic dredging techniquesis by ports that have been refused a licence to disposeof dredged material at sea. There are a few ports thathave highly contaminated sediments, but neverthelesshave a requirement to dredge if the port is to continueto operate. If a sea disposal licence is refused, there are

Many ports recognised the financial savings associatedwith hydrodynamic dredging techniques and indicatedthat their use was being considered for the future.However, as for current users, the quantities involvedwill probably be small and the areas localised. Portsthat already use hydrodynamic dredging techniquesplan to continue using them in the future, with quanti-ties removed remaining similar to present.

DISCUSSION

The questionnaire "A Review of Dredging Techniques"received a good response with 42% of recipientsreturning completed questionnaires. In addition, theresponses were geographically widespread, whichenabled us to gain an understanding of dredging prac-tices throughout the study area (Figure 6).

Of the responses received to the questionnaire, 27%indicated the use of hydrodynamic dredging tech-niques. Whilst this implies that a large number of portsdo not employ these techniques, there are some portsusing hydrodynamic dredging methods that did notrespond to the survey. The ports that do use hydrody-namic dredging techniques are located all aroundEngland and Wales, suggesting that their use is notlimited to a particular sedimentary regime. The sedi-ments relocated by these techniques are mainly of siltgrade, but some port operators successfully relocatefine and medium sand. However, as the particle size ofthe sediment increases, the success of most hydrody-namic dredging techniques tends to decrease.

This is to be expected, as most of these techniquesrely, at least in part, on water flow to relocate thesediment.


15

Figure 5. The location of ports using hydrodynamic techniques(left) and estimated quantities moved (above).

Figure 6. Respondents to the questionnaire

a number of options open to a port (such as use ofsediments in land reclamation, transfer to a confinedmarine disposal facility, removal to landfill, application ofsediment remediation techniques) but the easiest andcheapest option is often the use of a plough, or vesselpropeller agitation. Such techniques in areas of conta-minated sediment will inevitably result in the spread ofthe contamination.

The use of hydrodynamic dredging techniques can bevery attractive in commercial terms for small ports,however the lack of legislative control could result inserious adverse impacts on areas of fisheries or con-servation importance if the techniques are used with-out a suitable assessment of the consequences. Themain issues of concern are the lack of knowledge ofthe destination of the sediment, and the possibility ofchemical contamination within the sediments beingredistributed. The sensitivity of the site is also of keyimportance. For example, the use of a plough dredgerwithin a port already using a trailer suction dredger willhave a minimum additional physical impact on theenvironment. In such situations, the sediments willhave been chemically and physically characterised priorto the issue of a disposal licence, and hence a predic-tion of impacts can be readily made.

In contrast, the use of a plough or hydrodynamic tech-niques in an area located close to shellfish beds or aconservation site has the potential to yield adverseenvironmental effects from physical smothering. If the

material is contaminated, then subsequent uptake ofcontaminants by filter feeders, or release of contami-nants into the water column, may give rise to toxicolo-gical impacts on marine organisms and potentially toimpacts on higher trophic levels through transfer up themarine food chain. Although many port operators didstate that they would consult with appropriate bodiesprior to commencing dredging using "non-FEPA-licensable" techniques, these statements were qualified by comments relating to the cost of suchconsultation.

This is particularly notable, as cost reduction is one ofthe prime reasons given for the use of hydrodynamicdredging techniques in small ports.

There are a number of other considerations associatedwith the use of these techniques: "hotspots" of conta-mination could be spread to give a higher backgroundlevel with consequences for conventional licenseddisposals. There is some difficulty in estimating thequantities of sediment relocated, and in identifying thesubsequent deposition sites of the sediments.

Any evaluation of the potential impact of the use ofsuch techniques should take account of the environ-mental sensitivity of the site, the nature of the sedi-ments and the hydrodynamic regime. In making suchan assessment, it is also appropriate to put it into thecontext of the impact of conventional dredging and ofnatural events including storms.

16

Figure 7. The water injection dredger Jetsed working close to the Thames Barrier Clearance.

(TBT) were present in the water column (Waite andWaldock). It is likely that TBT will also be present in thesediments. Since the ban on the use of TBT on boatsunder 25 m in 1987, water column sampling (the mostrecent in 1992) has shown a significant decrease inTBT levels (Waite and Waldock). However, the decom-position of TBT in sediments is a very slow process andthere may still be TBT present in concentrations thatwould harm marine life. Detailed research has shownTBT to have a wide range of harmful effects on marineorganisms both sub-lethal and lethal with the scale ofthe effect dependent upon the species and the TBTconcentration in the sediments (Alzieu). Hence TBTconcentrations in sediments are a critical factor indeciding the suitability of dredged material for seadisposal in FEPA licence assessments (Murray et al.).

No formal investigations have been carried out into thedestination of the disturbed sediment, but on the lowtide following a dredging operation it is possible to seethe newly deepened areas and a new layer of silt (1/4inch thick) upon the surrounding mudflats (Barren).

The Dart, like many estuaries in England and Wales, issubject to an environmental management project(DEEM) which encourages and facilitates consultationbetween all groups involved with the estuary. TheDEEM is supportive of the use of the Neptune andknows of no adverse effects of its use. The upperreaches of the River Dart contain a designated shellfishharvesting area. These shellfish would be sensitive toincreases in the suspended solid content of the riverwater and TBT contamination in the sediments. Itshould be noted that at present the dredging is notperformed in the immediate vicinity of this fishery.

CASE STUDIES

The following case studies present three differentsituations involving the use of dredging techniqueswith "non-FEPA-licensable" sediment disposal.

Dartmouth, Devon The Dart Harbour Navigation Authority (DHNA) areresponsible for maintaining navigable channels withinthe River Dart in Devon, England. Owing to relativelylow levels of siltation (compared with other areas inEngland) there has not been a requirement to dredgethe main channel and Dartmouth Harbour since 1955.However the River Dart is an important and populararea for sailing and the smaller channels, creeks andberths do require dredging to maintain access.

To meet this dredging requirement, DHNA commis-sioned the construction of an agitation dredger. Thetechnology is based on offshore (e.g. pipeline) dredgersbut DHNA developed the navigation dredging method(Barren). The agitation dredger, Neptune is flat bot-tomed and approximately 8 m in length with a width of<3 m. The propeller (diameter of ca. 1 m) can operatein water depths of up to 5.5 m but is most effective inshallower water. DHNA operate the vessel by swingingabout an anchor in an arc of about 2.5 m, or moving thevessel through the berths and channels. The quantitiesof sediment relocated are not precisely known butDHNA estimate a quantity of between 150 and 1000wet tonnes per annum (Figure 8).

DHNA do not carry out sampling or chemical analysisof the river sediments prior to dredging an area but it isknown that, in the late 1980s, high levels of tributyl tin


Figure 8. The agitation dredger Neptune alongside the quay, with its propeller down, agitating the sediments to allow silt to be dispersed by the tide.

Burnham Yacht Harbour, Burnham on Crouch, Essex The River Crouch in Essex, England is an importantcentre for sailing. During the summer months, themany river moorings in front of the town of Burnhamon Crouch and the Burnham Yacht Harbour are filledwith small yachts and sailing boats.

In addition, the relatively high siltation rates on the eastcoast of England produce a need for frequent mainte-nance dredging. Under the guidance of the CrouchHarbour Authority (CHA), the small marinas and har-bours on the River Crouch employ a plough dredger torelocate sediment from the channels and berths.Approximately 30,000 wet tonnes of sediment (mostlysilt) is relocated each year. During a visit to the YachtHarbour to see the plough in action, a large plume ofsilt was observed in the dredged areas. The CHAcontinuously monitors the environmental impacts ofploughing, and has not observed any adverse effects todate. In addition, the Burnham Yacht Harbour hascarried out its own investigation into the dispersal ofthe dredged material.

In early 1996, trials were carried into the use of waterinjection dredging in the yacht harbour. Presently, theuse of the plough is the preferred dredging method. Inrecent years, Essex Marina at Wallasea Island has helda licence to dispose of dredgings at sea. The disposalsite used was Bridgemarsh Island in the River Crouchwhere the material was deposited to help slow theerosion of saltmarsh from the island. Owing to a chan-ge of ownership of the marina, the licensed disposalhas now ceased with the new marina operators inten-ding to plough instead. This technique is said to havethe support of the harbour authority, English Natureand the Environment Agency.

As a result in part of the location of the CEFAS Labora-tory in Burnham, there have been a large number ofstudies and research projects carried out into variousaspects of the river. These include investigations intothe impacts of TBT from the yachts on the benthiccommunities in the river, and chemical analysis ofsediments for contaminant levels. Very high levels ofTBT in water and sediments were observed in the1980s and these have since reduced following the banon the use of TBT on small vessels in 1987 (Waite etal.). As a consequence, a marked biological recovery ofthe river is in progress (Waldock et al.). The sedimentsof the Burnham Yacht Harbour, analysed in support ofapplications for FEPA sea disposal licences, containconcentrations of contaminants similar to those insediments from the river. However, with the cessationof FEPA licensed disposals, the dredged sediments are no longer subject to routine analyses under thatprocedure.

An environmental management project is proposed forthe River Crouch that will encourage communication

between users of the river. It seems that continuedassessment of the impacts of dredging, and of thecontaminant content of the sediments, would be anappropriate component of that management pro-gramme.

Harwich, EssexIn contrast to the two small operations discussedpreviously, the Port of Harwich in Essex, England,holds a FEPA licence to deposit at sea approximately 3 million wet tonnes of maintenance dredged silt andsand. The dredged areas include the approach channelto the important Ports of Felixstowe and Harwich.

The sediment is removed using a trailer suction dredgerand is then transported out to the disposal site (Figure 9). In addition to the trailer suction dredger,Harwich also employ a plough dredger. The plough isused to relocate sediment from the berths and otherrestricted areas into the operating area of the trailersuction dredger. The plough may also be used to flat-ten out the peaks and troughs produced by the opera-tion of the trailer suction dredger. Approximately50,000 wet tonnes of sediment is moved from therestricted areas to be picked up by the trailer suctiondredger and removed to sea.

Harwich Haven Authority (HHA) use turbidity meters tomonitor the turbidity caused by both the plough andtrailer suction dredgers, in addition to surveying theimpacts on benthic organisms and fisheries. HHA arepresently deepening the approach channel, and areinvolved in projects to beneficially use the dredgedsediments in the local estuaries. One of these benefi-cial uses involves placing dredged silts into the watercolumn to provide a sediment source with the aim offacilitating deposition on the mudflats. The increases inthe suspended solid content of the water column in thedeposit areas will mask any effects of using a plough.

Since the survey was completed, licences have beenissued to Harwich Haven Authority for the disposal ofapproximately 27 million wet tonnes of material dredgedas part of the capital project to deepen the approachchannel. This disposal is in licensed dumping sitesoffshore, in additional to the near-shore and estuarialbeneficial deposits.

THE USE OF SIDECASTING IN THE UK

The following comments are not derived from thesurvey of dredging techniques, but are drawn fromCEFAS’s experience in relation to assessing applicationfor FEPA licences.

In addition to the disposal of dredged material at sea,the deposit of material below mean high water springsin relation to marine constructions is also regulated


18

should be removed from the seabed on completion ofthe project and disposed of either to land, or to licensedmarine disposal sites. The implications of not removingthe excess material depend upon the site and thenature of the sediment, but may include damage tofishing equipment, provide a long-term source of sus-pended sediment or interfere with natural sedimenttransport processes. In some cases, there may be apotential for more damage to result from the removalof the material than leaving it in situ, so this mustconsidered in the assessment

The physical impacts of sidecasting include:– Direct smothering of benthic habitats by deposition

onto the seabed.– Increase in suspended sediment loads during trench-

ing, deposition onto the seabed and the possibletransport of suspended material to other areas.

– Once sidecast, the deposit will provide a source ofsediment to be transported away from the construc-tion site and deposited in other (possibly more sensi-tive) areas.

– Further release of sediment during replacement inthe trench, or removal of excess material from thesite.

The importance of these impacts will depend upon thetype and quantity of material to be sidecast (recentapplications have ranged from <1000 wet tonnes to

under FEPA. The recent changes in European and UKlegislation relating to the quality of marine dischargeshas prompted an increase in the number of applicationsfor the construction of new outfalls. The followingparagraphs describe the approach CEFAS use whenadvising the Ministry of Agriculture, Fisheries and Foodof the impacts of outfall construction.

The most common method (currently) of outfall con-struction involves the dredging or excavation of atrench, and the placing of the excavated material on theseabed to one or both sides of the trench. This processis termed sidecasting. The dredging/excavating of thetrench is not regulated by FEPA, but a FEPA licence isrequired to deposit the material onto the seabed. Thereare a number of generic issues of concern related tothe environmental effects of sidecasting, however theimportance of each issue will depend upon the specificcharacteristics of the construction site. Each applicationfor sidecasting is assessed independently according tothe sensitivity of the site but using a common set ofguidelines.

Physical impactsThe main reason for sidecasting is to provide a tempor-ary deposit site for material that will be required to infilla trench after placement of the outfall pipe. In manycases only a proportion of the sidecast material will besuitable for trench infilling. The rest of the material

19

Figure 9. Trailing suction hopper dredger at work in the Harbour of Felixstowe, deepening the approach channel to make the harbour more accessible to the new generation of container ships.

>250,000 wet tonnes), and the sensitivity of the con-struction site and surrounding areas. All of these fac-tors must be considered during the assessment of anapplication.

Chemical impactsThe potential chemical impacts of sidecasting include:– Contaminated material, if present at depth, may be

brought to the surface and deposited on surroundingareas.

– Contaminants may be released into the water column.

– Disturbance of the sediments and the consequentchanges in physicochemical parameters may in-crease the bioavailability of contaminants.

Unlike dredged material that is to be disposed of at sea,sidecast material is not routinely sampled and analysedprior to a FEPA licence being issued. However, wherean area is likely to be contaminated or concerns areraised by consultees, samples are analysed. In manycases, chemical analysis is carried out during the pro-duction of an Environmental Assessment, and hencethe data are available to CEFAS to inform the licensingprocess.

Conclusions

Hydrodynamic dredging techniques are used bothalone and in conjunction with conventional dredgingtechniques at a number of ports and harbours through-out England and Wales

Most ports or harbours which use hydrodynamic tech-niques as their sole method of dredging move relativelysmall quantities of sediment, typically <5000 wettonnes per annum, but up to 30,000 wet tonnes perannum can be moved in some cases.

Chemical and physical impacts associated with the useof hydrodynamic dredging techniques are seldom fullyevaluated. There appears to be little if any requirementfor such assessments under existing legislative controls

Potentially adverse environmental impacts can occurfrom the use of hydrodynamic techniques. A site-specific assessment should be made to ensure thatmeasures are taken to minimise such impacts. Keyfactors are the environmental sensitivity of the site, thequantity and nature of the dredged sediment and thehydrodynamic regime.

When used in conjunction with conventional dredgingfrom which sea disposal of the material has beenlicensed, additional adverse impacts from hydro-dynamic dredging are likely to be minimal.

A few ports may take advantage of the lack of legisla-tive control of hydrodynamic dredging techniques andemploy them if refused a licence to dispose of dredgedmaterial at sea. If the licence has been refused becauseof high contamination of the sediment there is a stronglikelihood of adverse environmental consequencesresulting from the operation.

References

Alzieu, C. (1996). “Biological effects of tributyl tin on marine organisms”. In de

Mora, S. J., Tributyl tin: case study of an environmental

contaminant. Cambridge Environmental Chemistry Series, 8,

pp167-205.

Barren, Roger (1999).Dart Harbour Navigation Authority, personal communication.

CEDA, Environmental Steering Committee (1998). “Hydrodynamic dredging: Principles, effects and methods”.

Submitted to SEBA 99/12/Info.1-E.

Murray, L.A., Waldock R., Reed, J. and Jones, B. (1999). Sediment quality in dredged material disposed to sea from

England and Wales. In press.

Waite, M.E., Waldock, M.J., Thain, J.E., Smith, D.J. andMilton, S.M. (1991). “Reductions in TBT concentrations in UK estuaries following

legislation in 1986 and 1987”. Mar. Env. Res. 32, pp 89-111.

Waite, M.E. and Waldock, M.J. (1993). “The effect of the use of tributyltin (TBT) antifoulings on

aquatic ecosystems in the UK”. Section II. DoE report 7/8/74.

Waldock, R., Rees, H.L., Matthiessen, P. and Pendle, M.A.(1999).“Surveys of the benthic infauna of the Crouch Estuary (UK) in

relation to TBT contamination”. Journal of the Marine Biologi-

cal Association of the United Kingdom, 79, pp 225-232.


20

Hewitt W. Jeter

Determining the Ages of Recent SedimentsUsing Measurements of Trace Radioactivity

In recent years there has been a growing emphasis oncharacterisation and remediation of contaminatedwaterways. Often a long stretch of river and the asso-ciated terminal estuary has been contaminated by industries over a period of decades. The toxic substan-ces released by these industries become progressivelyburied in the sediments, such that profiles of thesesubstances in the sediment become a record of thecontamination process. These water systems mayhave only a fragmentary history of depth surveys, ornone at all. Such water systems require anothermethod to measure sedimentation rates and to deter-mine the calendar dates associated with buried toxicsubstances.

Chronology information of this kind is useful in deter-mining which industries caused the contamination, forindustrial production or release records can be compar-ed to the dates of buried materials. Chronology information is also useful for determining whetherburied substances are migrating or degenerating.

Abstract

Laboratory analyses of sediment cores can determinesedimentation rates and the calendar dates associatedwith various depths within sediments. These chronolo-gy results can be used for characterising the depositionenvironment of a water system, which is pertinent tothe planning of dredging operations. The methods areparticularly useful for water systems which containburied toxic substances. Measurements of differentradioactive species give chronology information fortime frames from a half year to 100 years before thepresent. Recent studies in the 1990s where thismethod has been applied include the Kalamazoo Riverin Michigan, the Housatonic River in Connecticut, thePassaic River in New Jersey, the Hudson River andGrasse River in New York. This paper presents thepractical application of three geochronology methodswhich have been used.

This subject was presented at a Workshop of theNuclear Regulatory Commission, Region 1, in June1999, in Baltimore, Maryland, USA.

INTRODUCTION

The accumulation of sediment in a water system is oneof the most common situations which requires dredging.Consequently, a knowledge of sedimentation rates isoften useful in planning dredging operations. The pat-tern of sedimentation rates can be used to calculatewhen various areas will require work. This informationcan also be used to plan the time intervals betweensuccessive operations. In shipping channels and otherlocations which are frequently dredged, sedimentationrates can be calculated from the history of periodicdepth surveys. There are instances, however, forwhich no history of depth surveys exist.

Determining the Ages of Recent Sediments Using Measurements of Trace Radioactivity

21

Hewitt W. Jeter

Hewitt Jeter received a PhD degree inoceanography at Oregon State Univer-sity in 1972. Since that time he hasbeen a research scientist and Managerof Radiochemistry at Teledyne, West-wood New Jersey. He has presentedpapers on oceanic measurements,mathematical simulation of rivers anduranium deposit, and radiochemicalmethods.

Trace quantities of radioactivity, primarily of naturalorigin, are found in most substances. The earth, theoceans, the atmosphere and living things have alwayscontained a number of radioactive species. Scientificmethods for measuring recent sedimentation rates byanalysing trace quantities of radioactivity were devel-oped by universities beginning more than thirty yearsago (Ref. 1). These methods were subsequently expan-ded and applied to lakes, ocean environments, andrivers (Ref. 2-5).

With increasing interest in the environment, the tech-niques were applied to contaminated river and estuarysystems (Ref. 6-8). The procedures involve takingsediment cores and analysing samples at variousdepths. The distribution of natural or artificial radioactivespecies in the cores can often be interpreted to pro-duce a chronological history of the sediments and theirassociated contaminants.

Present studies of contaminated river systems ofteninclude the taking of a pattern of sediment cores tocharacterise the site. The number of cores may befewer than 10 or greater than 100. Cores are often 4 to10 cm in diameter and 1 to 7 m in length. The cores aregenerally cut lengthwise to enable a sedimentarygeologist to make a visual study of the sediments,sometimes including grain size measurements. Trans-verse sections of the cores are then sampled and sentto a laboratory to measure the concentrations of con-taminants, resulting in profiles of the contaminants as afunction of depth. Other sections of the core, often 2cm in thickness, are sent to a radiochemistry laboratoryto measure trace radioactivity at various depths. Theradioactivity data are interpreted to determine sedimen-tation rates and the dates associated with different

Table I. Pb-210 concentrations plotted in Figure 1.

Depth cm Pb-210 pCi/g

6 – 8 2.5 + – 0.210 – 12 2.2 + – 0.220 – 22 1.2 + – 0.130 – 32 1.5 + – 0.140 – 42 1.2 + – 0.250 – 52 0.86 + – 0.1260 – 62 0.52 + – 0.0870 – 72 0.76 + – 0.1080 – 82 0.63 + – 0.13

100 – 102 0.51 + – 0.11138 – 140 0.55 + – 0.12

Tolerances of the measurements are based ondetection uncertainties at the 2 sigma (95% confidence) level.

depths in the sediment. The chronology data are thenlinked to the contaminant profiles in order to character-ise the site.

The Teledyne Environmental laboratory has supportedmany site characterisations since 1977 by performingradiochemical analyses of core samples and interpret-ing the sediment chronology. Work of this kind hasbeen performed for 23 engineering firms and for 15universities. Recent studies in the 1990s include theKalamazoo River in Michigan, the Housatonic River in


22

Figure 1. A profile of Pb-210 concentrations measured in asediment core. Results are expressed in picocuries per gram(pCi/g). The picocurie is a small unit of radioactivity equivalentto 2.22 nuclear transitions per minute.

being derived from direct deposition, from upstreamtransport, and from decay of Rn-222 in the water. Theresult is a relatively high concentration of Pb-210 in theshallow sediments.

Figure 1 and Table I show an example of Pb-210 con-centrations found at various depths in a sediment core.The measurements were made by cutting 2 cm thicksections from a core, drying the samples in a laboratoryoven, then performing chemical separations to isolatethe radioactive elements present (Figure 2). The puri-fied elements are placed in sensitive radioactivitydetectors to measure their radioactive concentrations

Connecticut, the Passaic River in New Jersey, theHudson River and Grasse River in New York. Thispaper presents the practical application of three geochronology methods which have been used.

CHRONOLOGY STUDIES ON THE 100 YEAR

TIME FRAME: THE PB-210 METHOD

The Pb-210 (lead-210) method performs best in rela-tively quiet deposition areas such as marsh lands (Ref.9), bays, lakes (Ref. 4) and the backwaters of riversystems. For example, in the Passaic River (NewJersey), more than 100 sediment cores were analysedfor Pb-210. Of those, the three cores taken from quies-cent tributaries exhibited more regular profiles.Fast flowing rivers may produce intermittent depositionwhich is better measured by the Cs-137 (cesium-137)method described in the next section. Nevertheless,the Pb-210 method is often used in conjunction withthe Cs-137 method in active rivers in order to obtainmaximum chronology information.

Lead-210 is a natural radioactive form of lead which isfound in small quantities in most soils as part of theuranium decay series. It is also produced as naturalfallout from the atmosphere by radioactive decay ofRn-222 (radon-222) gas. Minute quantities of Pb-210 fallconstantly onto the earth’s surface. This materialaccompanies and mixes with sediments which accu-mulate at the bottoms of water systems. For a givenlocality, the supply of Pb-210 is often at a steady rate,


23

Figure 3. Purified bismuth derived from a sediment sample isloaded into a low level beta-particle detector. The measuredradioactivity of Bi-210 is used to calculate the concentration ofPb-210.

Figure 2. Radiochemcial separations are performed to isolatebismuth or polonium from sediment samples. The purifiedelements are then analysed in radioactivity detectors.

(Figure 3). Lead-210 is often measured indirectly byanalysing its radioactive decay products Bi-210 (bis-muth-210) or Po-210 (polonium-210).

The Pb-210 profile in Figure 1 shows relatively highconcentrations in the surface sediment caused bynatural fallout. There is decreasing trend with depth,finally achieving a constant level which is inherent inthe sediment itself. The decreasing trend is caused byradioactive decay of fallout Pb-210 with time. Deeperlevels in a core correspond to earlier times, so thatradioactive decay is manifested as decreasing concen-tration with depth. This is the basis for determiningsedimentation rates by the Pb-210 method.

In Figure 4, the logarithm of the “excess Pb-210”derived from natural fallout (the measured

concentration minus the constant concentration atdeeper levels) is plotted against depth. The linear trendof this plot shows that excess Pb-210 concentrationvaries logarithmically with depth. This situation occursbecause radioactive decay is an exponential process:under simple decay conditions, the logarithm of aradioactive concentration decreases linearly with time.The decay of Pb-210 translates into a logarithmic de-crease in excess Pb-210 concentration with depth inthe simplest case where the sedimentation rate andthe rate of Pb-210 supply are steady, and the uppersediments are nearly uniform in physical properties and intrinsic uranium-series content. Although morecomplex cases have been studied, simple logarithmicprofiles (or segments of profiles) are often found insediments and can be interpreted usefully.

The equation of the fitted line is shown in Figure 4. Theslope of this line can be used to calculate the sedimen-tation rate, knowing the radioactive decay coefficient ofPb-210. When base 10 logarithms are used and thedepths are expressed in cm, the sedimentation rate in cm per year equals -0.01352 / slope. In the caseshown, the ratio -0.01352 / -0.0142 leads to a calcula-ted sedimentation rate of 0.95 cm/y.

Because of radioactive decay, excess Pb-210 (derivedfrom natural fallout) is generally detectable to 100 yearsbefore the present. At depths corresponding to 100years or older, the excess Pb-210 has decayed awayand the measured concentration represents the back-ground level which is characteristic of the sedimentitself. If a logarithmic curve is fitted to a completePb-210 profile from the surface to the 100 year level,therefore, the sedimentation rate derived from theslope of the line represents an average over a 100 yeartime frame. Sometimes shorter segments of profilesare analysed, as will be shown, which lead to sedimen-tation rates averaged over shorter time periods.

Once a steady sedimentation rate has been derivedfrom a Pb-210 profile, calendar dates at various levels inthe sediment are easily calculated. For a given depth,the time interval between the deposition date and thecore sampling date is equal to the depth divided by the sedimentation rate. This interval is subtracted from theyear in which the core was taken. In the present exam-ple, if the core sample were taken in 1998, the dateassociated with 50 cm depth would be: 1998 - 50/0.95 = 1945.

The “steady” sedimentation rate illustrated does notimply that the rate is strictly constant. The 2 cm incre-ments taken from this core encompass a time periodof 2.1 years (2 cm increment / 0.95 cm/y = 2.1 y ).Therefore, seasonal or short-term fluctuations of thesedimentation rate would be averaged by the sampling.This shows that logarithmic trends of Pb-210 can beproduced even with short-term variations of the sedi-


24

Figure 4. A logarithmic fit to the data presented in Table I andFigure 1. The “excess” Pb-210 concentration is caused bynatural fallout. It is calculated in this case by subtracting theaverage of the two deepest measurements (0.53 pCi/g).

Figure 5. Two distinct sedimentation rates were found in atributary core sample when an ox bow (loop) was cut off.

cm/y or greater may be found. At 10 cm/y, excessPb-210 would be produced to a depth of 10 m if nodredging were performed. Cores of this length arerarely taken in surveys of rivers or estuaries, and sedi-mentation rates are calculated based on shorter, incom-plete cores.

CHRONOLOGY STUDIES OVER THE LAST 45YEARS: THE CS-137 METHOD

Another powerful chronology method is based on thefallout of Cs-137 (cesium-137) from the atmospherictesting of nuclear weapons. This fission product hasbeen in the atmosphere since the early days of thenuclear age and continues to deposit on the earth insmall quantities today. Profiles of Cs-137 in sedimentsindicate its deposition history which can be interpretedto assign calendar dates. Measurements can be

mentation rate. Similarly, the rate of Pb-210 supply tothe sediment does not need to be strictly constant, butsteady when averaged over periods of about 2 years inthis example.

An unusual case of Pb-210 chronology is shown inFigure 5. This sediment core is derived from a meander-ing tributary leading into one of the Great Lakes, whichformed an ox bow (loop) which was subsequently cutoff, straightening its path. Two logarithmic lines withdifferent slopes are shown which indicate two differentsedimentation rates. The date when the stream changed course is calculated from the depth of theslope break and from the shallower sedimentation rate.The discontinuity in profiles occurs near 66 cm depth.Because the core was taken in 1996, the date of thisevent is calculated as 1996 - 66/1.8 = 1959. Cases havebeen reported where multiple straight line segmentsare found on logarithmic plots of Pb-210 concentrationversus depth.

Figure 6 illustrates the variation in performance of thePb-210 method. Both logarithmic Pb-210 profiles wereobtained in the same river system (the Passaic River)and both indicate nearly the same sedimentation rate.The upper profile exhibits significantly more scatter ofthe data points which is indicated by its lower value ofthe correlation coefficient, R2. This scatter may becaused by intermittent deposition during storm, floodand seasonal events. Scatter of Pb-210 data are oftenassociated with layers of sand found between layers ofsilt. The sand layers, produced by high energy erosionevents, often have low values of Pb-210. Profiles whichexhibit significant scatter of the data imply greateruncertainty of the sedimentation rates, such as theexample of the Passaic River given above. For thisreason, the Pb-210 method is often augmented orreplaced by the Cs-137 method for fast flowing rivers,as described in the next section.

The Pb-210 method is usually applied to sedimentationrates greater than 0.1 cm/y, which are of primary in-terest in dredging studies. In the case of a 0.1 cm/ysedimentation rate, the 100 year time frame wouldproduce excess Pb-210 over the shallowest 10 cm ofsediment. Often the first few cm of sediments produceanomalous Pb-210 trends, however, which are difficultto interpret. These anomalous measurements may becaused by mixing of the sediments by biological organ-isms or by physical processes. In addition, the densityof sediments may vary considerably in this region,making the application of the simplest model invalid.Often Pb-210 data in the first few centimetres departfrom the logarithmic trend found at greater depths, andthese data points are excluded in the fitting of logarith-mic profiles.

For high sedimentation areas such as bends in riverchannels and in river deltas, sedimentation rates of 10


25

Figure 6. Logarithmic Pb-210 profiles from cores taken at twolocations in the same river system (Passaic River). Thecalculated sedimentation rates are nearly equal but the lowerplot exhibits greater certainty because the profile shows lessscatter of the data points.

performed in the laboratory by direct analyses of thegamma radiation from a sediment sample (Figures 7and 8) without any chemical processing.

The Cs-137 method is fundamentally different from thePb-210 method in that it provides date “markers”rather than concentration slopes which can be interpre-ted. The first appearance of Cs-137 in sediments gene-rally marks the year 1954, for that is the year when

concentrations generally achieved detectable levels.Thus, if Cs-137 is detected at a given depth, the date isinterpreted to be 1954 or afterward. The level in thesediment at which Cs-137 is first detected is called theCs-137 “horizon”, following geological terminology.

If a series of analyses are made at various depths in asediment core, another Cs-137 marker is often found inthe form of a concentration maximum at the year 1963.This is caused by the increase in nuclear testing in thelate 1950s and early 1960s, followed by a subsequentdecrease in testing.

Figure 9 and Table II show a Cs-137 profile measured ina sediment core in 1995. The profile shows a Cs-137horizon near 48 cm depth. This marker can be used tocalculate a sedimentation rate as follows: (48 cmdepth) / (41 y between 1954 and 1995) = 1.2 cm/y.The profile also shows a Cs-137 maximum near 37 cmdepth. This marker can also can be used to calculate asedimentation rate: (37 cm depth) / (32 y between1963 and 1995) = 1.2 cm/y. In this case, the samesedimentation rate is calculated from both markers.

This is not always the case, however, because eventssuch as unusual floods could occur between the years1954 and 1963, causing the two calculations to differ.A study in the Delaware River estuary showed sedi-mentation rates between 1954 and 1963 to be twiceas high as sedimentation rates after 1963 because ofstorm events in the earlier interval (Ref. 9).


26

Figure 7. A sample prepared in a standard cylindrical containeris placed on a germanium-lithium diode detector to measureits gamma radiation.

Figure 8. The gamma ray energy spectrum shown on thisscreen represents several radioactive species being analysedby the germanium-lithium diode detector in the background.

Figure 9. A profile of Cs-137 concentrations measured in asediment core. The concentration maximum indicates theyear 1963 and the depth at which Cs-137 disappears marksthe year 1954.

found marking the year 1954, but no maximum con-centration is found to mark the year 1963. This oftenhappens at locations where all the Cs-137 concentra-tions are low or near the detection limit. Other casesshow more than one maximum in concentration,although the larger maximum generally marks the year1963. The shape of the Cs-137 maximum can be sharpand distinct or broad and blunt. This shape has beenrelated to the depth of surface mixing of sediments bybiological organisms or by physical processes. Modelling studies show that broader maxima in Cs-137concentrations are produced when several cm ofsurface sediment are mixed (Ref. 4).

CHRONOLOGY STUDIES OVER THE LAST

HALF YEAR: THE BE-7 METHOD

Several radioactive species are continually produced inthe atmosphere by the interaction of cosmic radiation(from outer space) with gas molecules. One of thesespecies is Be-7 (beryllium-7) which was confirmed bymeasurements of rain water (Ref. 10). This nuclideforms part of the natural fallout which accumulates inthe surface sediments of water bodies. It is used toprovide additional information in surveys for chronologypurposes.

It is practical to measure Be-7 by direct gamma spectralanalysis of a sediment sample simultaneously with theCs-137 measurement, without additional cost. Thesetwo radioactive species produce gamma radiation atdifferent energies, so that they appear in differentregions of the spectrum (Figure 8). Such measure-ments are not as sensitive, however, as the morelaborious chemical separation procedures which aresometimes used in scientific studies.

It is often useful to compare sedimentation rates calcu-lated by the Pb-210 method and the Cs-137 method.The core illustrated in Figure 9 is the same core whichwas illustrated for Pb-210 in Figure 1. Analysis of thePb-210 profile resulted in a calculated sedimentationrate of 0.95 cm/y, which is lower than the rate of 1.2cm/y calculated from both markers of the Cs-137profile. The discrepancy is explained by the differenttime frames characterised by the two methods. Thesedimentation since 1954 (characterised by the Cs-137method) has been more rapid than the 100 year aver-age characterised by the Pb-210 method.

The shapes of Cs-137 profiles vary significantly (Figure10). Cases commonly occur where a Cs-137 horizon is


27

Figure 10. Profiles of Cs-137 in sediments exhibit different shapes. Overall concentration levels and mixing of the surface sediments are contributing factors.

Table II. Cs-137 concentrations plotted in Figure 9.

Depth cm Cs-137 pCi/g

0 – 2 0.27 + – 0.118 – 10 0.26 + – 0.08

10 – 12 0.36 + – 0.1112 – 14 0.31 + – 0.1216 – 18 0.39 + – 0.1122 – 24 0.38 + – 0.1030 – 32 0.51 + – 0.1036 – 38 1.19 + – 0.1138 – 40 1.03 + – 0.1140 – 42 0.55 + – 0.1146 – 48 0.13 + – 0.0754 – 56 < 0.0962 – 64 < 0.09

Tolerances of the measurements are based ondetection uncertainties at the 2 sigma (95% confidence) level.

Beryllium-7 decays relatively quickly, with a half-life of53 days ( in one half-life the concentration of a radioac-tive species decays to half of its original level). Forcomparison, the half-life of Pb-210 is 22 years and thatof Cs-137 is 30 years. Because of its rapid decay, Be-7is only found in the first few cm of sediments. Conse-quently, it has limited utility in the practical study ofsedimentation rates for characterising water systems.It has been used effectively, however, for the scientificstudy of vertical mixing processes in surface sediments(Ref. 11).

For practical survey work, the primary utility of Be-7 isto indicate whether there has been very recent deposi-tion at a sampling location (within the last half year) andwhether the sediment core has been taken with thesurface sediments intact. Detection of Be-7 in the firstcm or two of a core gives affirmative answers to thesequestions. But conversely, if Be-7 is not detected in thesurface sediments, these questions are not necessarilyanswered in the negative. The reason for this is thatvertical mixing of the surface sediments by biologicalorganisms or by physical processes can dilute the Be-7concentration to the point where it is undetectable bythe practical, direct gamma analysis method.

To illustrate, in two different studies of the PassaicRiver system, one study showed reliable detection ofBe-7 in 38% of the cores taken. In the other study, only16% of the cores showed Be-7 near the surface. It isevident that Be-7 can provide supplemental informationin a practical survey, but that it is not as useful asPb-210 or Cs-137 for measuring sedimentation rates(Ref. 8).

Conclusion

In recent years, many surveys of contaminated riversystems have included analyses of sediment cores toprovide chronology information. These analyses havebeen used to calculate sedimentation rates and toprovide calendar dates associated with various levels inthe sediments. Chronology information of this kind canassist in determining which industries caused thecontamination, for industrial production, or releaserecords can be compared to the dates of buried mate-rials. Chronology information is also useful for deter-mining whether buried substances are migrating ordegenerating, knowledge which is often useful inplanning dredging operations. The techniques used in sediment chronology are de-rived from universities and from scientific studies.Although many techniques have been developed, onlymeasurements of man-made Cs-137 and naturalPb-210 and Be-7 have emerged as practical approachesto the chronology of sediments accumulating withinthe last 100 years for site characterisation and remedia-tion studies.

References

1. ED Goldberg (1963). “Geochronology with Pb-210”. Proceedings of a Symposium on

Radioactive Dating, International Atomic Energy Agency.

Vienna, Austria. pp 121-131.

2. S Krishnaswami, D Lal, J Martin and M Meybeck (1971). “Geochronology of lake sediments”. Earth and Planetary

Science Letters, 11, pp 407-414.

3. M Koide, A Soutar and ED Goldberg (1972).“Marine geochronology with Pb-210”, Earth and Planetary

Science Letters, 14, pp 442-446.

4. JA Robbins and DN Edgington (1975). “Determination of recent sedimentation rates in Lake Michigan

using Pb-210 and Cs-137”. Geochemica et Cosmochimica Acta,

39, pp 285-304.

5. HJ Simpson, CR Olsen, RM Trier, and SC Williams (1976). “Man-made radionuclides and sedimentation in the Hudson

River Estuary”. Science, 194, pp 179-183.

6. NH Cutshall, IL Larsen and MM Nichols (1981). “Man-made radionuclides confirm rapid burial of kepone in

James River sediments”. Science, 213, pp 440-442.

7. RF Bopp, HJ Simpson, CR Olsen, RM Trier, and N Kostyk(1982).“Chlorinated hydrocarbons and radionuclide chronologies in

sediments of the Hudson River and estuary”. New York,

Environmental Science and Technology, 16 (10), pp 666-676.

8. RF Bopp, ML Gross, H Tong, HJ Simpson, SJ Monson, BLDeck, and FC Moser (1991). “A major incident of dioxin contamination: sediments of New

Jersey estuaries”. Environmental Science and Technology, 25,

pp 951-956.

9. RA Orson, RL Simpson, and RE Good (1992). “A mechanism for the accumulation and retention of heavy

metals in tidal freshwater marshes of the upper Delaware River

estuary”. Estuarine Coastal and Shelf Science, 34, pp 171-186.

10. JR Arnold and HA Al-Salih (1955).“Beryllium-7 produced by cosmic rays”. Science, 121, pp 451-

453.

11. S Krishnaswami, LK Benninger, RC Aller, and KL Von-Damm (1980).“Atmospherically-derived radionuclides as tracers of sediment

mixing and accumulation in near-shore marine and lake sedi-

ments: evidence from Be-7, Pb-210, and Pu-239,240”. Earth and

Planetary Science Letters, 47, pp 307-318.


28

Charles W. Hummer, Jr.

Books/Periodicals Reviewed

of deltas.” The keynote speakers focussed on the fourareas that had been selected to define the essentialfunctions of publics works departments:– Political Objectives and Financial Means– Public Opinion and Interest Groups– Local and Regional Interests– Technological Innovation.

One of the last sections of the proceedings is theConference Statements. These statements wereformulated in parallel sessions. The highest level ses-sion consisted of the Directors-General of Public WorksDepartments. Other sessions focussed on specificthemes, which correspond to the four areas mentionedabove. The value of these statements is that theysynthesise the thoughts and ideas of the participatingrepresentatives from the nations attending and theyprovide a framework for future attention and study.

Without diminishing the importance of other sectionsof the proceedings, the section entitled, “Visions ofNetherlands Organisations”, bears special attention.Because of the preeminence of The Netherlands indredging and related technologies, it has been andremains a centre of expertise on such technologies.Combined with the Dutch population concentrated in adelta, it is logical that past and current policies as wellas the vision of the future, the visions expressed in thissection, are timely, relevant and filled with experiencethat exists no where else.

The proceedings are published in a first-class hardcoverbook and are divided into discrete sections, which, afterthe Preface and Introduction, include:– Opening and Closing Addresses– Keynote– Country/Delta Position Papers– Characteristic Data of the Delta Countries– Visions of International Organisations– Visions of Netherlands Organisations– Conference Statements– Committees

Sustainable Development of DeltasProceedings of the International Conference at theOccasion of the 200th Year of the Directorate-Generalfor Public Works and Water Management. Amsterdam,The Netherlands. November 23-27 1998. Delft Universi-ty Press. Hardbound, 473 pp, illustrated.

Edited by Henk Oudshoorn, Bart Schulz, Anne van Urk and Paul Zijderveld

It goes without saying that the matter of developmentin river deltas is intrinsically linked to the history of TheNetherlands and the Dutch Rijkswaterstaat. The occa-sion of the 200th anniversary of the Rijkswaterstaatprovided an excellent opportunity to share these expe-riences and to exchange ideas on issues of futurerelevance with countries that also have densely popula-ted deltas. The event let to the international conferencethat is summarised in these proceedings.

The conference included high-level representatives ofpublics works departments from Argentina, Bangla-desh, China, India, Indonesia, Mozambique, Pakistan,The Philippines, Russia, Rumania, Sri Lanka, Surinam,The Netherlands, Thailand and Vietnam. The proceed-ings include the national summaries of each country’srepresentatives, highlighting the following aspects:– situation of the country or delta in the country;– overview of developments and future constraints;– overview of policy plans to meet the challenges; and– future prospects and needs for co-operation.

Each session was prefaced with a keynote addressestablishing the session’s primary theme. The keynotepresented by Mr. P. Kieft, Acting Director-General ofthe Rijkswaterstaat, is of particular interest and rele-vance. The presentation has wide application to anyand all who deal with public works functions andespecially in a marine or riverine setting.

Likewise, the other keynote papers are especiallyvaluable and have much broader application than thesubject of the conference, “sustainable development


29

– Participants– 200 Years Directorate-General of Public Works and

Water Management– Abbreviations

The subject of the proceedings is expansive and whilstsome of its elements bear on the technology of dredgingand marine technology, its scope is far greater. Itplaces in a context to the technological applicationswithin the structure of the four areas mentioned earlier.Readers in nations where delta populations existshould obtain and familiarise themselves with thecontents of these proceedings. An interesting note isthe absence of participation from the United States, anation where a number of deltas and populations fallwithin the scope of this conference.

This publication may be obtained from:Delft University PressPO Box 98, 2600 MG Delft, The Netherlandstel. +31 (0)15 278 3254fax +31 (0)15 278 1661

Dredgers of the World, 2nd Edition.Oilfield Publications Ltd/Dayton’s Publishing Ltd.Herefordshire, UK. 680 pp, illustrated. 1999.

Prepared in cooperation with the International Association of Dredging Companies

The first edition of this world-wide catalogue of dredging vessels was published two years ago. It wasso well received by clients and principals alike whorequire dredging services that the publishers wereencouraged to continue the endeavour. Hence a new,updated better-than-ever book has recently beenpublished.

Obviously, this second edition has built upon the expe-riences of the first, and this comprehensive register ofthe world’s fleet of dredgers has been expanded andimproved. The new edition has been carefully updatedwith assistance of the IADC and others, and providescharacteristics of the dredgers, owners, managers,affiliations and in many cases a drawing or photographof the dredger. Furthermore, the list of owners/managers and affiliated companies gives the currentaddresses, telephones, facsmile and telex contacts forthe vast majority of those listed. It is apparent that tocompile the detailed listing of such a comprehensivenature, the owners had to have been major cooperatorsin the publication.

The dredgers types and number of units included in thebook are as follows:– Backhoe/Dipper/Grab Dredgers (178)– Barge Unloading Dredgers (21)– Bucket Ladder Dredgers (72)– Cutter Suction Dredgers/Bucket Wheel Dredgers (19)

– Special Equipment (agitation, water injection andwormwheel dredgers) (19)

– Suction Dredgers (26)– Trailing Suction Hopper Dredgers (261)

The criteria for including dredgers have provided alisting of all dredgers of consequence that may be ofinterest in terms of most conceivable dredging projects,and it has done so in a manner where one may look forthe information on the basis on a variety of startingpoints. The publication quite effectively meets thechallenges of organising a tremendous amount ofinformation and a variety of indices allows the user toaccess the equipment in a variety of ways.

Enough particulars for each dredger are presented toallow an initial screening of those suitable for a specificset of circumstances on a project. Specifically listed foreach dredger are the following categories:– General: name, owner, marine manager, year built,

type, classification, flag, call sign;– Main Dimensions: LOA, breadth, depth, drafts (dred-

ging loaded and unloaded), GRT, NRT, DWT;– Machinery and Power: main engines, available

horsepower (all modes of operation)), performance– Dredging and Discharging Equipment: dredging

depths, capacities (dredging and discharge), shoredelivery system (if applicable), hopper capacity, pipediameters;

– Accommodations (if applicable); – Mooring System; and


30

– the high bridge across the Flinte Channel; and– the railway engineering system and installations.

The conference deals primarily with the first of thelarge separate parts of the total project; namely, thedredging and reclamation work. This work involved theexcavation of nearly 8 million cubic metres of material.The conference provided an overview of the planning,design and construction of the dredging and reclama-tion part of the Link Project, and the proceedings cap-ture the technical papers and posters related to thisspecialty conference.

The Link Project is one of the major public works capitalprojects in the world today and presented monumentalengineering, environmental and operational challenges.Beyond that, it involved two nations and the EuropeanUnion, and the political aspects that impinge on aproject such as this that crosses so many borders.

The value of these proceedings is that they encompassthe full spectrum of the issues and problems related toa major international public works project. They sum-marise the approaches that led to the successful exe-cution of the project. For these reasons, they makefascinating reading, even for one not particularly tech-nologically inclined. For those in the engineering field,these proceedings present some real-world experien-ces and expertise in the many complex aspects of sucha major project.

The proceedings contain 28 papers and 10 posters, ofwhich 3 posters fall within dredging and reclamation-related topics. The papers cover such broad subjectmatter ranging from geographical, political and socialdevelopment issues related to such a project, to theplanning, execution, contract development andmanagement, equipment selection and utilisation, aswell as the many aspects of the engineering, design,construction and environmental matters.

A quick read through the papers finds one wanting todelve deeper into each subject and paper, so the readbecomes an extended read after all. This is a tribute tothe organisers, and the authors of this conference, whochoose the subject matter and to the editors whoassembled the proceedings. As one of the few verylarge civil works project in the world today, this com-pendium of experience is extremely valuable to thosewho will consider, plan and execute future projects. Itis a significant written record for future generations ofengineers and builders of major works. For the resear-cher and archivist, it is notable that the editors took thetime and trouble to include abstracts and key words formost papers.

To assist the reader in gaining an appreciation for thescope and depth of the papers presented, a listing isherewith provided.

– Additional Data, which includes all other informationnot elsewhere specified.

Dredging News Online

With the ever-increasing number of worldwide dredgingprojects, an update every two years is far from adequate. Therefore the publishers have initiated awebsite www.sandandgravel.com/news as a freeonline service. Every fortnight it is updated with currentinformation on tenders and contracts, new technology,new vessels, R&D, company news and other pertinentinformation in the dredging industry. Though the sub-scription is free, there is an opportunity to advertise(contact address: [email protected]).

In summary, this most recent addition to dredgingliterature is extremely comprehensive and far surpassesany periodicals which, limited by size, can only attemptto publish an annual listing of dredgers. It is highly recommended for users or libraries where dredgers playan important role and up-to-date information is prized.

To order the publication contact:IADC Secretariat, Duinweg 21, 2585 JV The Hague, The Netherlandstel. +31 70 352 3334/ fax +31 70 3512 2654 or use the attached publication form.

Or contact:Oilfield Publications Limited/Dayton’s Publishing Ltd.Homend House, PO Box 11, Ledbury, Herefordshire HR8 1 BN, United Kingdomtel: +44 (0) 1531 634563, fax: +44 (0) 1531 634239email: [email protected]

Challenges, Solutions and Lessons on EnvironmentalControl, Project Management ConstructionMethodology, Dredging and Reclamation Technology.Proceedings of the Øresund Link Dredging and Recla-mation Project, 26-28 May 1999, Copenhagen, Denmark.Published by Øresundskonsortiet/Central DredgingAssociation/Öresund Marine Joint Venture, Denmarkand The Netherlands, 1999.Softcover, 356 pp, A-4, illustrated.

Edited by Iversen and Morgensen

The Øresund Fixed Link Project creates a link betweenDenmark and Sweden, an area occupied by threemillion inhabitants. It is a combined rail and motorwaylink extending 16 km between Kastrup on the Danishside to Lernacken on the Swedish side. The project issplit into five large sub-projects:– dredging and reclamation work;– the immersed tunnel under the Drogden Channel;– the low and approach bridges;


31

Technical Papers– Potential Integration of Copenhagen and Malmö-

Lund. A Cross Border Integration– Project on the European Metropolitan Level.– “Build a Link!” - Goals, principles, strategies and

results.– The D & R works that make the foundation for the

link.– The role of the International Expert Panel in the

design and execution of environmental managementof the Øresund Link.

– Translation of bi-national legislation into specificoperational criteria.

– Environmental management and the impact onexecution.

– How to secure co-operation between the Contractor,the Owner and the Authorities.

– Choosing the right Contract and the right Contractor.– Control is good, Confidence is better.– Geotechnical Investigations: Subterraneous mapping.– An Assessment of the Limestone. Planning and

estimation of the dredging and reclamation works.– Dredging Operations and Technology – Meeting

Challenges with the Dredge Chicago.– Dredging Operations and Technology – Castor.

Increasing the efficient use of 3680 kW cutter power.

– Construction of the perimeter for the island andpeninsula.

– Optimised use of Dredged Materials for Reclama-tion.

– How deep and how much? The development of anintegrated survey package.

– Introduction to Spill, Spill Monitoring and Spill Management.

– Feedback Monitoring Programme — Strategies andprinciples.

– Feedback Monitoring — Implication on the dredgingworks.

– The Authorities’ Monitoring Programme. – How essential were the Environmental Requirement-

Alternatives?– What did project management learn? (The Owner).– The Öresund Marine Joint Venture — An integrated

management for a non-integrated joint venture.– What did the Authorities learn?– Engineering solutions to environmental concerns and

the Northumberland Strait Crossing Project.– Reflections made by the Dredging Industry.– Reflections made by an Owner — Different Environ-

ments, Different Solutions Experience at HarwichHaven.

– Jamuna Bridge Project- Lessons Learned and Experiences.

PostersPosters related to the Øresund Link Project:– Efforts made by the Owner to go hand in hand with

the Contractor.

– Investigations of the Properties of Dredged Lime-stone Fill.

– Dredged Moraine Clay as High Class Fill Material.– Spill Monitoring Set-up - Evaluation of the Optimisa-

tion Process.– Spill from Dredging Activities.– Environmental Research prior to Construction– Establishing Baseline Conditions as Basis for Environ-

mental Impact Assessments and Design of Monitor-ing Programmes, Marine Biology and SedimentStudies (combined paper).

– Management of the Authorities' EnvironmentalControl and Monitoring Programme for the ØresundFixed Link.

Posters within D&R related topics:– New Software for the Estimation of Sediment

Release during Dredging and Dredged MaterialDisposal.

– Improvements to the Environment as a result of theKhor Faridah Dredging and Reclamation Projectcarried out in Abu Dhabi.

– Enhancing Dredging Efficiency by Selecting the RightPipeline.

Certainly these proceedings are a must for anyoneconnected with dredging or marine constructionprojects. The book is very well laid out and the printingis of a fine quality. One trivial but important element ofthe book is that it has the title well displayed on thebinding so it is readily seen on the library shelves. Theproceedings may be obtained from the following sources:

ØresundkonsortietKastruplundgade 20-24DK-2770 Kastrup, DenmarkEmail: [email protected]

Central Dredging AssociationP. O. Box 4882600 AL Delft, The NetherlandsEmail: [email protected]

Öresund Marine Joint VentureC/o Per Aarsleff A./SLokesvej 15DK-8230 Aabyhoej, DenmarkEmail: [email protected]


32

Seminars/Conferences/Events

SingaPort 2000Singapore Expo

March 29-31 2000

Asia’s premier maritime exhibition and conferenceincorporates port and maritime equipment, shipbuildingand repair, and logistics and warehousing. The exhibitors include suppliers of ships, engines, cargohandling, marine safety equipment as well as portplanners, environmental and research and develop-ment services and insurance and financial services.

Attendees will include port authorities, government andtrade organisations, cargo and container terminal opera-tors, and all types of marine consultants and relatedservices.

For further information please contact:Mr Chandran Nair, PSA Exhibitions Pte Ltd.1 Maritime Square #09-72, WTCSingapore 099253tel. +65 321 2103, fax +65 274 0721email: [email protected]

Shipping Eurasia 2000Feshane Fuar Exhibition Centre,

Istanbul, TurkeyApril 6-9 2000

Trade fair organiser Jaarbeurs Utrecht, The Netherlandshas announced Shipping Eurasia 2000, a brand-newactivity focussing on the fast-growing Turkish andregional shipping market. Bordered by the Black Sea,the Aegean and the Mediterranean, Turkey is expectedto see a remarkable expansion of its port and harbouractivities in the coming years.

Special events include: a high-ranking pavilion on portequipment and management; a shuttle seabus fromthe exibition to the main Turkish shipyards at Tuzla anda comprehensive range of technical presentations andseminars.

World Water FairNetherlands Congress CentreThe Hague, The Netherlands

March 16-21 2000

This international fair is being held in conjunction with the 2nd World Water Forum and Ministerial Conference, at the invitation of the Dutch Governmentand under the auspices of the World Water Council. Inthe last two days of the forum, a conference of Headsof Government and Ministers will be held.

The aim of the forum is to discuss one of the majorproblems facing the world in the new millennium: howto supply and manage clean water sustainable for thebenefit of people, the food chain, and the environment.

Water management experts from all over the worldrepresenting NGOs, government on all levels, watercompanies and public utilities, water-related industries,engineers, consultants, researchers, trade associationsand educational institutions are expected to attend.A special WaterPlanet VISION pavilion, including spectacular multimedia effects, will be featured.

For further information contact:www.worldwaterforum.org orwww.aquatech-rai.com

Amsterdam RAI/Aquatech Business Media, Organisation World Water FairPO Box 777771070 MS Amsterdam, The Netherlandstel. +31 20 549 1212, fax +31 20 549 1843email: [email protected]

Second World Water Forum & Ministerial Conference, Ministry of Foreign Affairs, DML/PSPO Box 20061, 2500 EB The Hague, The Netherlandstel. +31 70 348 5402, fax +31 70 348 6792email: [email protected]


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For further information please contact:In Turkey:FGS Fuarçilik AS, Att: Mr Ali ÇivÇeliktepe, Inönü cad. No: 11/34. Levent/Istanbul — Turkeytel. +90 212 282 8808, fax +90 212 281 2713email: [email protected]://www.fgsfair.net

For other countries:Royal Dutch Jaarbeurs, Att: Mr. Harold Mol, PO Box 83003503 RM Utrecht, The Netherlandstel. +31 30 29 55 662, fax + 31 30 29 55 585email: [email protected]://www.jaarbeursutrecht.nl

River Trans China 2000Central China International Fair Center,

Wuhan, PR ChinaJune 13-16 2000

The 2nd China Wuhan International River Transporta-tion, Port & Shipbuilding Technology and EquipmentExpo is being organised by the Chang Jiang RiverTransportation Administrative Bureau, an agency of theMinistry of Communication. The Chang Jiang (formerlyYangtze) river is the number one river in China and nowranks as the second largest economic region after thesoutheast coastal area.

A plan from 1995-2010 for future development of theChang Jiang area has been approved by the WuhanGovernment. Its aim is to construct ports and channels,strengthen the support and maintenance systems aswell as renew modern cargo ships in order to meet theneeds of the national economy and social development.

The first exhibition was held in 1998 and was wellattended by many European and Asian exhibitors. Thisyear’s exhibits will include ports and channels enginee-ring; ports communication systems; harbour and dockequipment; marine management and engineering; andother related exhibits.

For more information please contact:Ms Carmen Yeung, Managing Directoror Ms Michelle LeeUnits A&B, 14/F, Guangdong Tours Centre18 Pennington St., Causeway Bay, Hong Kongtel. +852 2881 5889, fax +852 2890 2657email: [email protected]://www.together-expo.com

WEDA XX & TAMU 32Crowne Plaza Hotel,

Warwick, Rhode Island, USAJune 25-28 2000

The Twentieth Western Dredging Association AnnualMeeting and Conference and the Thirty-second TexasA&M University Dredging Seminar will be held simulta-neously in June 2000 in Rhode Island. The theme ofthe conference is “Dredging Technology for the Millen-nium” and will be a forum amongst port and harbourauthorities, agencies, users, dredging companies,environmentalists, consultants and academicians in this field. A technical paper committee will reviewand select all submitted papers. In addition, “a studentcall for papers” has been issued to selected academicinstitutions asking students to submit abstracts. Four student papers will be selected, included in theconference papers and given a monetary reward. An exhibition will also accompany the conference, andspace is presently available.

For further information please contact:Executive Director, WEDA, PO Box 5797, Vancouver, WA 98668-5797 USAtel. +1 360 750 0209, fax +1 360 750 1445email: [email protected]

BaltExpo-2000Olivia Hall, Gdansk, Poland

September 5-8 2000

This 10th International Maritime Exhibition BaltExpo-2000 has established itself amongst Europe’s leadingexhibition in the maritime sector and has created aforum for Polish and foreign suppliers and end-user.The exhibit is sponsored the Polish President, PrimeMinister and Minister of Transportation and MaritimeEconomy. Exhibits will include shipbuilding, repairs andconversion; eguipment, machinery and engines; com-munication, navigation and position; ports, services andterminals; cargo handling; offshore; pollution controland much more.

For further information please contact:Agpol Promotion Ltd.17, Sniadeckich Str., 00-654 Warsaw, Polandtel. +48 22 628 7295 or 628 7296fax +48 22 625 23 98email: [email protected]

Biuro Reklamy SA9, Flory Str., 00-586 Warsaw, Polandtel. +48 22 849 6081 or 849 6006fax +48 22 849 3584email: [email protected]


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Prospective authors are requested to submit a 300-word abstract by March 1 2000 either as hard copy orelectronically. Notification of acceptance will be by April15. The deadline for the submission of draft manu-scripts is September 1 and the final submission isFebruary 1, 2001.

For further information, please contact:EADA Secretariat, John DobsonGPO Box 388, Hamilton Central,Qld 4007, Australiatel/fax +61 7 3262 3834email: [email protected], or

Authors from the CEDA region (Europe, Africa, Middle East) should contact:CEDA Secretariat, Anna CsitiPO Box 488, 2600 AL Delft, The Netherlandstel. +31 15 278 3145, fax +31 15 278 7104email: [email protected]

4th PIANC-PCDC SeminarBuenos Aires, Argentina

November 20-24 2000

Camara Argentina de Consultores with the support ofthe Subsecretaria de Puertos y Vias Navegables and incooperation with the Spanish National Section ofPIANC is organising this seminar in Buenos Aires. Papers are invited on inland waterways and shipping;capital and maintenance dredging; maritime ports andshipping; multi-modal transport, fishing ports and coas-tal zone managment.Deadline for a one or two page abstract is March 12000. The seminar will be conducted in Spanish withsimultaneous translation into English and vice versa.

For further information please contact:PIANC Secretariat,Graaf de Ferraris, 11éme ètage, Boïte 3 Bld. Emile Jacqmain 156, B-1000 Brussels, Belgiumtel. +32 2 553 7159 or 7160, fax +32 2 553 71 55email: [email protected]://www.tornado.be/~navigation-aipcn-pianc

Oceanology International 2001 AmericasMiami Beach Convention Center,

Miami Beach, Florida, USAApril 3-5 2001

The first OI Americas exhibition and conference will beheld in April 2001 and will be held biennially thereafter.It is set to become a joint ocean forum bringing togetherall sides of industry, science, research, government andacademia, with a natural focus on the opportunitiesfacing the Americas.As a transport hub handling 60 percent of airline trafficbetween the Americas, Miami has been chosen forease of travel for the global ocean community as wellas for the concentrations of ocean science and techno-logy institutions in Florida.

For further information please contact:In the Americas:Kari Jacobson, OI AmericasPGI/Spearhead, PGI Inc,2200 Wilson Boulevard, Ste. 200Arlington, VA 22201-3324, USAtel. +1 703 312 9129, fax +1 703 528 1724

For other countries:Jane Blinkenberg, OI AmericasPGI/Spearhead, Spearhead Exhibitions Ltd,Ocean House, 50 Kingston Road,New Malden, Surrey KT3 3LZ, United Kingdomtel. +44 181 949 9813 or 949 9222,fax +44 181 949 8186email: [email protected]://www.oiamericas.com

Call for Papers

WODCON XVI and ExhibitionHotel Shangri-la,

Kuala Lumpur, MalaysiaApril 2-5 2001

The Sixteenth World Dredging Congress and Exhibitionwill be entitled “Dredging for Prosperity; AchievingSocial and Economic Benefits”. New ways of dredgingand handling dredged materials are continually beingfound. These need to be promoted in order to achievesocial and economic benefits. Papers showing thebenefit/cost relationship of dredging works are espe-cially encouraged, including new forms of dredging,and reclamation contracts, monitoring dredging withrespect to environmental benefit, developments ineducation and training, case studies and other develop-ments in the industry.


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Day 1: Why Dredging?The Need for Dredging/Project Phasing

Day 2: What is Dredging?Dredging Equipment/Survey Systems (includes a Site Visit)

Day 3: How Dredging?Dredging Projects

Day 4: Preparation of DredgingContract

Day 5: Cost/Pricing and Contracts

Representatives of port authorities, companies, and individuals interested in attending are requested to complete the preliminary registration form below as soon as possible and prior to August 31, 2000, and return to:IADC Secretariat, Duinweg 21,2585 JV The Hague, The Netherlandstel. +31 70 352 3334, fax +31 70 351 2654e-mail: [email protected]

Place: SingaporeDate: October 9-13, 2000

In cooperation with the National University of Singapore(NUS) and the Applied Research Corporation (ARC),International Association of Dredging Companies ispleased to organise, for the fifth time, an intensive,one-week seminar on dredging and reclamation.

The last course, held in February 1998, met with suchenthusiastic response, that IADC, building on thissuccess, has decided to present this seminar again in2000. The costs are US$ 2950, which include six nightsaccommodation at the conference hotel, breakfast andlunch daily, one special participants dinner, and a generalinsurance for the week.

The seminar includes workshops and a site visit to adredging project. Highlights of the programme are:

International Seminar onDredging and Reclamation

(please print)

Name ..........................................................................................................................................................................

Title ..........................................................................................................................................................................

Company ..........................................................................................................................................................................

Address ..........................................................................................................................................................................

..........................................................................................................................................................................

Tel. ................................................................................... Fax ...............................................................................

E-mail ..........................................................................................................................................................................

Please send this form and your deposit by cheque or credit card for US$ 500 in order to guarantee your place atthe seminar. Upon receipt of this form and your deposit your place in the seminar is confirmed. We will then sendyou further detailed information, final registration forms, and an invoice for the correct amount.

Without your deposit we cannot guarantee your place and accommodations at the seminar.

�� A Cheque is enclosed.

�� Please charge my credit card:

�� American Express �� Eurocard/Master Card �� VISA �� Diners Club

Account no.:

Expiry date:

Signature .............................................................................................................. Date ................................................

AfricaBoskalis South Africa (Pty.) Ltd., Capetown, South AfricaBoskalis Togo Sarl., Lomé, TogoBoskalis Westminster Cameroun Sarl., Douala, CamerounBoskalis Zinkcon (Nigeria) Ltd., Lagos, NigeriaDredging International Services Nigeria Ltd., Lagos, NigeriaHAM Dredging (Nigeria) Ltd., Ikeja, NigeriaNigerian Dredging and Marine Ltd., Apapa, NigeriaWestminster Dredging (Nigeria) Ltd., Lagos, Nigeria

The AmericasACZ Marine Contractors Ltd., Brampton, Ont., CanadaBeaver Dredging Company Ltd., Calgary, Alta., CanadaDragamex SA de CV, Coatzacoalcos, MexicoGulf Coast Trailing Company, New Orleans, LA, USAHAM Caribbean Office, Curaçao, NANorham/Dragagens, Rio de Janeiro, BrazilStuyvesant Dredging Company, Metairie, LA, USAUscodi, Wilmington, DE, USA

AsiaBallast Nedam Malaysia Ltd., Kuala Lumpur, MalaysiaBallast Nedam Dredging, Hong Kong Branch, Hong KongBoskalis International BV., Hong KongBoskalis International Far East, SingaporeBoskalis Taiwan Ltd., Hualien, TaiwanDredging International Asia Pacific (Pte) Ltd., SingaporeDredging International N.V., Hong KongDredging International N.V., SingaporeFar East Dredging Ltd., Hong KongHAM Dredging (M) Sdn Bhd, Kuala Lumpur, MalaysiaHAM East Asia Pacific Branch, Taipei, TaiwanHAM Hong Kong Office, Wanchai, Hong KongHAM Philippines, Metro Manila, PhilippinesHAM Singapore Branch, SingaporeHAM Thai Ltd., Bangkok, ThailandJan De Nul Singapore Pte. Ltd., SingaporeMumbai Project Office, Mumbai, IndiaPT Penkonindo, Jakarta, IndonesiaTideway DI Sdn. Bhd., Selangor, MalaysiaVan Oord ACZ B.V., Dhaka, BangladeshVan Oord ACZ B.V., Hong KongVan Oord ACZ B.V., SingaporeVan Oord ACZ Overseas B.V., Karachi, PakistanZinkcon Marine Malaysia Sdn. Bhd., Kuala Lumpur, MalaysiaZinkcon Marine Singapore Pte. Ltd., Singapore

Middle EastBoskalis Westminster Al Rushaid Ltd., Dhahran, Saudi ArabiaBoskalis Westminster M.E. Ltd., Abu Dhabi, UAEDredging International N.V., Middle East, DubaiDredging International N.V., Tehran Branch, Tehran, IranGulf Cobla (Limited Liability Company), Dubai, UAEHAM Dredging Company, Abu Dhabi, UAEHAM Saudi Arabia Ltd., Damman, Saudi ArabiaJan De Nul Dredging, Abu Dhabi, UAEVan Oord ACZ Overseas BV., Abu Dhabi, UAE

AustraliaCondreco Pty. Ltd., Milton, QLD., AustraliaDredeco Pty. Ltd., Brisbane, QLD., AustraliaNew Zealand Dredging & General Works Ltd., Wellington

Van Oord ACZ B.V., Victoria, AustraliaWestHam Dredging Co. Pty. Ltd., Sydney, NSW, Australia

EuropeACZ Ingeniører & Entreprenører A/S, Copenhagen, DenmarkAnglo-Dutch Dredging Company Ltd., Beaconsfield,United KingdomA/S Jebsens ACZ, Bergen, NorwayAtlantique Dragage S.A., Nanterre, FranceBaggermaatschappij Boskalis B.V., Papendrecht, NetherlandsBaggermaatschappij Breejenbout B.V., Rotterdam, NetherlandsBallast Nedam Bau- und Bagger GmbH, Hamburg, GermanyBallast Nedam Dredging, Zeist, NetherlandsBallast Nedam Dragage, Paris, FranceBoskalis Dolman B.V., Dordrecht, NetherlandsBoskalis International B.V., Papendrecht, NetherlandsBoskalis B.V., Rotterdam, NetherlandsBoskalis Westminster Aannemers N.V., Antwerp, BelgiumBoskalis Westminster Dredging B.V., Papendrecht, NetherlandsBoskalis Westminster Dredging & Contracting Ltd., CyprusBoskalis Zinkcon B.V., Papendrecht, NetherlandsBrewaba Wasserbaugesellschaft Bremen mbH, Bremen, GermanyCEI Construct NV, Afdeling Bagger- en Grondwerken, Zele, BelgiumDelta G.m.b.H., Bremen, GermanyDraflumar SA., Neuville Les Dieppe, FranceDragados y Construcciones S.A., Madrid, SpainDravo S.A., Madrid, SpainDredging International N.V., Madrid, SpainDredging International N.V., Zwijndrecht, BelgiumDredging International Scandinavia NS, Copenhagen, DenmarkDredging International (UK), Ltd., Weybridge, United KingdomEnka-Boskalis, Istanbul, TurkeyEspadraga, Los Alcázares (Murcia), SpainHAM Dredging Ltd., Camberley, United KingdomHAM, dredging and marine contractors, Capelle a/d IJssel,NetherlandsHAM-Van Oord Werkendam B.V., Werkendam, NetherlandsHeinrich Hirdes G.m.b.H., Hamburg, GermanyHolland Dredging Company, Papendrecht, NetherlandsJan De Nul N.V., Aalst, BelgiumJan De Nul Dredging N.V., Aalst, BelgiumJan De Nul (U.K.) Ltd., Ascot, United KingdomNordsee Nassbagger- und Tiefbau GmbH, Wilhelmshaven,GermanyN.V. Baggerwerken Decloedt & Zoon, Brussels, BelgiumS.A. Overseas Decloedt & Fils, Brussels, BelgiumSider-Almagià S.p.A., Rome, ItalySkanska Dredging AB, Gothenborg, SwedenSociedade Portuguesa de Dragagens Lda., Lisbon, PortugalSociedad Española de Dragados SA., Madrid, SpainSocietà Italiana Dragaggi SpA. “SIDRA”, Rome, ItalySociété de Dragage International “S.D.I.” S.A., Marly le Roi, FranceSodranord SARL, Paris, FranceTideway B.V., Breda, NetherlandsVan Oord ACZ B.V., Gorinchem, NetherlandsVan Oord ACZ Ltd., Newbury, United KingdomWasserbau ACZ GmbH, Bremen, GermanyWestminster Dredging Co. Ltd., Fareham, United KingdomZanen Verstoep B.V., Papendrecht, NetherlandsZinkcon Contractors Ltd., Fareham, United KingdomZinkcon Dekker B.V., Rotterdam, NetherlandsZinkcon Dekker Wasserbau GmbH, Bremen, Germany

Membership List IADC 2000Through their regional branches or through representatives, members of IADC operate directly at all locations worldwide.


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