25. Ports and harbours, port construction and operations
Contents - Previous - Next
2. Environmental impacts and protective measures
2.2 Construction or expansion of seaport infrastructure and superstructure
2.2.1 Land-side facilities
2.2.2 Water-side facilities
2.3 Port operations
2.3.1 Land-side port operations
2.3.2 Water-side port operations
3. Notes on the analysis and evaluation of environmental impacts
4. Interaction with other sectors
5. Summary Assessment of Environmental Relevance
The ports and harbours sector includes all those activities undertaken in seaports to ensure the safe transfer, intermediate storage and intermediate transport of solid, liquid and gaseous goods of all kinds in the course of onward forwarding of these goods to and from land vehicles and vessels, or the transport of persons (e.g. ferry ports), or the landing of foodstuffs (e.g. fishing ports); these are the primary functions of a harbour.
Land vehicles Vessels
Rail vehicles Sea-going vessels,
Road vehicles Fishing vessels
Inland water vessels Underwater pipelines
All harbours furthermore have the function of a "safe haven".
The subsector of "seaport infrastructure" encompasses all the land-side and water-side installations of a seaport, which are directly or indirectly required to perform the primary function of a seaport, or which may be established in the form of industrial, commercial, or service facilities, i.e. to perform secondary functions.
Land-side facilities include:
- roads, railway lines and other transport areas;
- storage and stacking areas, warehouses and silo installations, tank farms, crane tracks;
- bridges, underpasses and overpasses, pipelines etc.;
- supply and disposal systems (for water, power, wastewater, refuse, bilgewater, oil, used oil);
- flood defences, dykes etc. (in harbours exposed to high-water and flood risks);
- operational buildings such as administration, equipment and repair facilities;
- industrial installations and buildings for harbour-related and secondary industries including e.g. wharf installations and buildings.
Water-side facilities include:
- harbour basins, approaches, access channels, locks, harbour dams, breakwaters;
- goods transfer quays and piers, shoreline protection, ro-ro and ferry facilities, dolphins and landing bridges;
- shipbuilding berths and fitting quays of wharfs (if located in the port area).
All activities in the subsector of seaport infrastructure are dependent, in terms of their type, design and situation, on:
- the local water and land conditions such as location, topography, soil composition etc.;
- the type and volume of the goods being transferred (general cargo: conventional, containers, ro-ro; bulk cargo: bulk general cargo, bulk goods such as ores, coal, wheat, industrial salts or liquid or gaseous bulk goods such as oil, LNG etc.);
- the land vehicles and vessels used to carry the above;
- the resulting operational requirements and designs;
- the rail, road, inland waterway and pipeline links to the hinterland;
- the surrounding structures which already exist or which are being established (industry, commerce).
The "seaport superstructure" subsector includes all non-permanent operational land-side and water-side facilities of a seaport which are associated with its primary or secondary functions. These include, among others:
- dredgers and other maintenance and repair equipment,
- mobile supply and disposal systems, as well as fire and disaster protection equipment (such as vehicles for dealing with oil spillages).
Non-permanent superstructure facilities in area surrounding the harbour or associated with its secondary function can be summarised as follows:
- supply and disposal superstructure
- transport and traffic structures
- maintenance and repair superstructure of harbour-related industrial and commercial establishments.
(Note: These are not necessarily linked to the harbour superstructure).
New structures, extensions, or conversions of seaports can be summarised in terms of their environmental effects. As far as the environmental impacts of special seaports or of any harbour-related industrial activities are concerned, reference should be made to the relevant environmental briefs.
It is also necessary to distinguish between general-purpose harbours and special harbours used only for handling particular types of goods. Even in "general-purpose harbours", there is an increasing tendency for goods of only one type or category to be handled in specialised facilities referred to as terminals (oil terminals, ore or grain terminals, ro-ro terminals etc.). This is done either for safety reasons or because of the availability of specialist equipment.
Furthermore, seaports are either natural or artificial harbours.
Natural harbours Artificial harbours
Harbours on rivers or estuaries;
Artificial harbour basins and approaches;
Side harbours; Artificial islands
Harbours in bays or fjords;
Natural harbours generally involve less disturbance of the natural environment.
2. Environmental impacts and protective measures
The environmental impacts of sea harbours are usually considerable and arise on the one hand from the construction, conversion or extension of seaport installations (infrastructure as well as superstructure), but also to a large extent from the operation of all harbour installations and from the industrial and commercial installations and transport systems (both on water and on land).
The environmental impacts affect water, soil and air, all types of flora and fauna (both aquatic and terrestrial) and humans.
Causes Effects on
New construction Water
Operation of all installations and systems Flora/fauna (aquatic/terrestrial)
In principle, the larger the construction or expansion projects and the more intensive the port's handling activities (measured in t/a), the greater the environmental impact.
Special impacts are caused by dangerous goods, as defined by the IMDG Code (International Maritime Dangerous Goods Code), even in small quantities.
The environmental impacts can be divided into effects in the "infrastructural and superstructural" sector:
- primarily caused by the harbour installation as the sum total of all the water-side and land-side structures used in shipping and the transfer of goods and
- secondarily caused by industrial installations which may be closely linked to seaports, as infrastructural facilities for the processing or refining of goods and raw materials; erecting such facilities causes changes in the natural peripheral conditions and must therefore be regarded as incursions into the natural environment and landscape.
and in the "operational" sector:
- primarily caused by all activities such as shipping, loading, discharging, storage, transport, supply and disposal, maintenance and repair and
- secondarily by all processing and refining activities in the industrial installations which may be associated with the port.
These activities bring about changes in the natural peripheral conditions and habitats and, as a result, may affect humans, animals, nature and the landscape.
2.2 Construction or expansion of seaport infrastructure or superstructure
2.2.1 Land-side facilities
A harbour installation generally requires large areas of land, particularly where storage areas, warehouses and perhaps industrial facilities are required. This being so, a harbour installation always has a major impact on the natural landscape, since beaches, coastal rocks, expanses of reeds or mangroves and other shoreline areas are artificially stabilised and built over and the surfaces flattened and sealed. Effects and changes occur particularly in sensitive areas such as forests, wetlands and areas of agricultural use, and also in residential areas, due to soil excavation, soil replacement or backfilling, surface sealing, water drainage and high ground loads. Although these are clearly unavoidable given the intended use of the installation, proper infrastructural planning will nevertheless ensure a degree of environmental protection on the land side.
Transfer, storage and deposit areas should be created according to the following principles, bearing in mind the nature and volume of the goods being handled and the operating methods:
a) In the case of ores, coal and salts, care should be taken to ensure that
- storage areas are designed to
be strong enough and dense enough to cope with the apparent
density and dumping height of the material, so as to avoid any
changes in the subsoil and surroundings;
- a water drainage system is planned in and around these locations adequate to deal with the rainfall occurring, to avoid penetration, seepage and draining of contaminated surface water and heavy metals into the soil and sea (settling tanks and clarification plants may be necessary).
b) In the case of bulk goods
storage, dust formation can be effectively prevented by hall
structures or sprinkling systems, though these are expensive to
construct and maintain.
- Bulk goods which are sensitive to weather must in any event be stored under cover or in silos.
c) In the case of handling operations involving oil and other liquids, ground surfaces must be adequately sealed in the discharge and loading area and in the tank area, with a system of oil separators or other wastewater purification systems; otherwise, procedural measures are the only precautions that can be taken against contamination of groundwater and seawater due to spillages.
Land-side harbour expansions must be planned well in advance so that the requisite areas and any land to be provided by way of compensation can be earmarked and kept available by means of appropriate land-use and construction planning. This is the only way of preventing the all too common phenomenon of harbour areas penetrating into established areas of habitation or into areas worthy of protection, involving forced resettlement or land clearance, or the uncontrolled spread of human habitation.
Buildings, functional structures and industrial and residential developments are all part and parcel of the development of a harbour zone. The factors which contribute to a more environment-friendly and environment-oriented planning concept are:
- the separation of areas with different purposes;
- the use of environment-friendly building materials;
- optimisation of maximum construction/utilisation heights in relation to land area demand;
- economical land-use;
- architectural matching of buildings and functional structures to the building style of the country in question;
- landscaping through planting/greening of open spaces in the vicinity of buildings and, if possible, at the edges of the storage areas of the port;
- the use of environment-friendly technologies in industrial installations and in their operation in the harbour area;
- infrastructural measures in the field of water supply and sewage disposal, so as to safeguard groundwater and surface water stocks and maintain seawater purity.
The development of a harbour often involves the erecting of industrial installations. Experience shows that the newly created jobs, and often the mere hope of jobs, lead to an increased and sometimes uncontrolled influx of workers and their families. When planning a harbour, care must therefore be taken to create conditions fit for human habitation in terms of housing and sanitation provision. There is a particular risk of ghettos developing in the vicinity of ports.
The development of a harbour area together with associated industrial establishments places an enormous burden on all supply and disposal facilities. Water demand and sewage generation are particularly important in terms of the environmental effects. However, the consequences for the air and soil, land consumption and the effects of traffic, including questions of safety, must also be taken into account as early as the planning phase.
2.2.2 Water-side facilities
Water-side harbour installations generally require large areas of land and therefore have a major impact on the natural environment and landscape. The environmental impacts can however be limited by careful planning. Therefore when planning and laying out the water-side structures of a seaport, one should aim to gain as much information as possible on the prevailing environmental conditions such as
- wind and wave conditions
- current and sedimentation conditions
- water, soil and air conditions,
on the basis of extensive prior bathymetric and hydrological measurements, natural data surveys and, if possible, model experiments, working with rather than against these conditions.
In addition, efforts should be made to blend the harbour installations into the general landscape as far as possible.
Silting means that regular maintenance dredging is required, to ensure that proper depth conditions are maintained; flushing or dumping of the dredged material causes major environmental problems, in particular because:
- the sludge may be contaminated by general water pollution, sewage discharge, oil or heavy metals;
- over long periods of time large flushing and dumping grounds are needed which are difficult and expensive to recultivate;
- dumping causes changes in the underwater configuration and the aquatic flora and fauna.
These consequences are best avoided by the early planning of structures in harmony with the water currents and the provision of suitable disposal facilities as far away as possible from areas of habitation. The same applies to the operational disposal of sewage, wastewater and refuse produced in the harbour.
The design of harbour facilities should take advantage of the natural effects of the tide and currents in the mouth or delta area of an estuary. This may serve, for example, to keep approaches clear by the careful location of training dykes to guide and concentrate the flow (flushing effect), of harbour defences (particularly in the access area, with a view to avoiding lee erosion) and of quay installations, which if possible should not be located in areas of dead water. Harbour installations should not be built in brackish water areas (where salt water and fresh water converge, leading to greater silting).
Fishing grounds and aquacultures of coastal and river fisheries, as well as other natural flora and fauna, may be adversely affected by harbour construction, because large areas of water, as well as breeding grounds and habitats, will be lost. Another danger posed by a harbour installation is the damage that may result from sewage outfalls or changes to the groundwater level in the harbour area.
Damage to fish stocks may pose a health hazard to consumers of fish and lead to job losses in the fishing industry.
Measures to reduce water pollution in the harbour area basically involve minimising discharges into the water or permitting only the discharge of treated wastewater and sewage.
In addition, ample provision should be made for the fishing industry, as early as the planning phase of the harbour facilities.
There is unlikely to be any adverse environmental impact from the building materials used to erect installations in the water (concrete, rubble); steel piling walls, on the other hand, are prone to severe corrosion in hot regions, particularly under the influence of salt and brackish water, so that they may only be used if anti-corrosion measures are applied. To avoid contamination, only toxin-free paints may be used for this purpose. Wood is only of limited suitability as a building material (in view of the short service life due to rotting in mixed water areas). On no account should certain tropical rainforest timbers be used (such as Bongossi woods), though these are prized as a building material because of their strength and long service life.
2.3 Port operations
The term port operation in this environmental brief covers not only "traditional" harbour operation (i.e. the handling and transfer of goods), but all operational activities which are carried out on the basis of the existing infrastructure of a seaport (including any industrial establishments) in the service, industrial, commercial and transport/traffic sectors, on both the land and watersides.
2.3.1 Land-side port operations
The possible environmental impacts of land-side port operation and the associated hazards are determined essentially by the nature of the goods and materials being handled. The handling method is also a decisive factor.
The following environmental effects, subdivided by the cargo types
- liquid bulk goods
- solid bulk goods
- general cargo
(a) In the transfer of oils, liquid chemicals or other liquids, seawater and groundwater may be contaminated; fire and explosion may occur, resulting in smoke and gas formation;
unintentional release or discharge of oil, petroleum derivates, liquid chemicals or other liquids may occur;
petroleum derivates such as petrol, oil and kerosene may be accidentally mixed, e.g. due to wrong coupling connections or the use of the wrong pipelines or during pigging (the cleaning of a pipeline by means of a "pig") with raising of the flash point;
people - unaware of the danger - may smoke or cook in the immediate vicinity of tank installations or unloading terminals;
tanks may be emptied on board ships or on land, causing dangerous gases to develop.
Measures to prevent environmental damage in the liquid bulk goods sector therefore require not only adequate infrastructural measures in the loading, unloading and tank storage areas, but also an efficient operational organisation with clearly demarcated areas of responsibility and authority. Furthermore, intensive training of the personnel engaged in this sector is required (see MARPOL Convention).
From the technical and operational aspects, the following safety precautions and resources are needed:
- skimming equipment (oil booms, oil skimmers)
- oil-binding substances (for small quantities only)
- stocks of sand
- fire-fighting systems with hydrants
- sprinkler systems
- foam generation systems
- emergency power supplies
- individual water supply pumps
- safety containers in the tank storage area
- safe distances between tanks and other installations.
For projects envisaging the use of oil transfer terminals, tank farms or refineries, the personnel to be deployed must receive training courses in good time, in the interests of environment-oriented planning.
(b) In the bulk transfer of grains and fodders, ores, coal and industrial salts, environmental effects such as groundwater and seawater contamination, serious dust formation and noise are likely. Bulk goods conveying systems are prone to dust explosions and fire and also, because of their size, have a major impact on the natural landscape.
Besides adequate physical infrastructural measures, good management and staff training are also vital to environmental protection. It is also essential that only the designated storage areas which have been sealed in the interest of groundwater protection are used for storage and that maintenance and repair work is carried out regularly (e.g. clearing the rainwater drainage inlets in the storage areas). Dust formation and noise can in most cases only be prevented by expensive overhead cover and dedusting and sprinkler systems, and by erecting halls. Loading and transfer should be enclosed if possible, and the "free fall" of dust-forming goods should be avoided. Dust, depending on its composition and fineness, can cause chemical, biological, mechanical, electrical or electrostatic problems.
(c) In the case of general cargo and container handling, the large-scale equipment used (e.g. container bridges up to 70 m high with the water-side beam arms folded up) is a source of noise and danger.
This type of equipment operates rapidly and precisely and alternatives using ships' tackle or mobile land equipment (e.g. straddle carriers, large fork-lifts) will lead to substantial reductions in speed and safety.
To avoid frequent intermediate movements, containers are stacked on top of one another by means of special handling and stacking machinery. This is usually a necessary measure and requires large areas of land.
The handling and stacking machinery, depending on its manoeuvrability, also requires additional space within which to move, and generates noise. Yet more space is needed for arriving, departing and connecting traffic. These areas, whose surfaces are normally sealed, require an efficient water drainage system with separate water treatment facilities.
The mechanisation of the general cargo sector moreover has socio-economic effects on the people working in the harbour; in this context, education and training should be taken into account as early as at the planning stage.
Mechanised handling also produces high levels of exhaust gas and noise - except in the case of electrically driven equipment. Equipment fitted with silencers and exhaust gas regulators are to be preferred. Exhaust gas emissions and noise should be minimised by regular maintenance; the environmental brief Workshops deals with the relevant environmental aspects.
Containerised, unitised and conventional general cargoes may furthermore contain dangerous solids or liquids (chemicals etc.), which may cause catastrophic environmental damage in the event of inappropriate handling or damage to the containers.
Here too, the risks should be minimised as far as possible through intensive training of personnel, provision of suitable equipment and correct handling/storage of the goods in question.
(d) Conventional general cargo may be directly or indirectly harmed by improper handling or storage, depending on the nature of the goods. Goods may be easily damaged depending on the packing, or they may be damaged in storage if they are not properly protected against the weather. Damaged or incorrectly stored goods, which are usually worthless to the consignee, must be disposed of. Risks of inexpert disposal can only be avoided if the personnel are adequately trained and an appropriate disposal infrastructure is provided.
(e) Fish and seafood present an environmental hazard if improperly processed, stored and treated, through the waste matter and wastewater produced. The consumption of improperly treated fish or seafood can cause illness.
Therefore special care must be taken when handling goods which are liable to deteriorate (e.g. by continuous refrigeration and rapid handling).
(f) The environmental impacts caused by industrial and commercial establishments in the harbour zone and the associated environmental protection measures depend on the types of raw materials and goods being processed or refined. The appropriate environmental brief should be referred to in this regard.
2.3.2 Water-side port operations
This sector is characterised by shipping activities and the associated operational measures, such as:
- guaranteeing ease of shipping movements (particularly the maintaining of appropriate water depths and consequent dredging activities);
- supplies to ships and waste disposal;
- ship-to-ship transfers;
- pilotage and the control of navigation.
Since all these activities which are needed to maintain harbour operations on the waterside are carried out from ships or floating equipment, adverse environmental effects on the water and the sea and consequently on the fauna, flora and groundwater will result in particular from:
- berthing and departure manoeuvres (risk of accident leading to spillages from ships)
- refuelling (and deliveries of other supplies)
- discharging, loading and lighterage
- disposal (sewage, wastewater and refuse)
- cleaning of tanks and holds
The only way to combat these environmental impacts is to train employees in these areas and provide appropriate equipment in the form of tugs, supply ships, lighters, pumps, oil barriers etc. This should be instigated primarily by the port authority or harbour operating company. (Problems of disposal and disposal facilities are dealt with in the environmental briefs Shipping, Solid Waste Disposal and Disposal of Hazardous Waste).
A further source of adverse environmental impact is maintenance dredging of harbours and approaches; in this regard, refer to section 2.2.2.
The above-mentioned environmental hazards can only be countered by responsible behaviour on the part of ships' masters or by close monitoring of shipping (with the threat of penalties); accidents in shipping lanes and the drastic environmental damage which may ensue can be avoided by using the simplest possible shipping control system (VTMS = Vessel Traffic Management System), adapted to local conditions, in conjunction with a well-trained and organised pilotage system. This should be provided for as early as the planning phase.
All the effects of the new building or restructuring of a seaport on the local population - including the female population - should be analysed at an early stage by a socio-economic and socio-cultural survey, whose results should be taken into account in the planning or in accompanying measures.
3. Notes on the analysis and evaluation of environmental impacts
The assessment and evaluation of environmental hazards in this sector relies on the availability of accurate planning documents concerning the types and quantities of the goods being handled and reliable forecasts for future development. It is also necessary to determine the potential for further processing and onward transportation of goods, and also make a careful assessment of local conditions (terrain, soil, climate, groundwater, existing infrastructure etc.).
It is suggested that integrated operational and construction plans be drawn up and that international or comparable German standards be applied for the appraisal of the physical installations and operations, to rule out the adverse environmental consequences of an unsatisfactory assessment.
The following should apply to installations:
- international standards under the MARPOL Convention;
- strength, stability and service-life criteria, e.g. according to German DIN standarads or the redommendations of the German working committee on bank revetments EAU;
- disposal methods (sewage/wastewater/refuse) according to international standards and comparable discharge values, depending on wastewater types;
- methods of maintaining air purity, e.g. according to TA-Luft (Germany's Technical Instructions on Air Quality Control).
For port planning, a detailed locational analysis is required, primarily comprising:
- measurement of currents and oceanographic data;
- physical and mathematical model experiments to determine the optimum flow design and to prevent sedimentation;
- transport and traffic analyses.
Special attention must be paid to guaranteeing and adhering to limit values. To achieve this, the port operating authority must receive appropriate training and be made aware of the problems. Moreover suitable inspection, monitoring and emergency equipment must be provided.
Environmental impacts can only be minimised through a suitable combination of installations, built to European standards and expertly used and monitored, enabling low discharge and emission values to be adhered to.
4. Interaction with other sectors
Seaports and their approaches involve making substantial changes to the existing natural, socio-economic and socio-cultural structures of the region.
In this context, the planning phase is of paramount importance, during which the many possible effects must be identified at an early stage. What is required, therefore, is regional planning, transport and traffic planning, socio-economic planning and also water framework management and overall energy planning.
Table 1 - Environmental effects of adjacent project areas
Interacting project areas
Nature of intensification of impact
|Storage and transport of dangerous goods||* Risk to
* Health hazard to personnel and population
and Natural Gas
Disposal of Hazardous Waste
Trade and Industry briefs
Decent living conditions for larger population attracted by the development
|* Sharp rise
in housing demand
* Demand for utilities and disposal services (water, power, waste disposal)
* Public Facilities (hospitals, schools)
Water Framework Planning
Solid Waste Disposal
|Transport integration and development||* Heavy
burden on existing traffic and transport facilities
(inland waterways, railways, roads)
* Increased expansion of transport facilities, with consequent effects
|All briefs in the transport sector|
|Incorporation into region's industrial development||* Development of processing industries, with consequent effects on e.g. utilities, disposal services, land-use, re-structuring of social conditions||Planning of
Locations, Overall Energy Planning, Water Framwork
Trade and Industry briefs (where particular sectors are affected)
5. Summary assessment of environmental relevance
Generally speaking, environmental effects are unavoidable. Nevertheless, projects in the ports and harbours sector can be planned and executed in a largely environmentally acceptable way if:
- the goals and the elements of the project are clearly defined;
- the operational and physical aspects are planned in an integrated manner;
- the environmental conditions prevailing in the immediate and wider planning area have been thoroughly and adequately researched;
- all conceivable interactions and conflicts of use are taken into account from the outset;
- high standards are applied from the very start, but using the simplest possible designs and methods tailored to local needs, to create installations which will enable environment-friendly operation when completed.
To ensure that the completed harbour installation will, in so far as technically possible, be operated with the minimal environmental burden, it is necessary in the planning phase:
- to take full account of operational needs from the very start;
- to provide for the comprehensive training of the later operating personnel, based on the need to raise their awareness of environmental impacts and environmental damage, and to make provision for the continuing training and further training of harbour personnel.
Affected population groups, and women in particular, should be involved in the planning and decision-making process from an early stage, in order to take account of their interests and help alleviate environmental problems (competing land-use, environmental burden of increased traffic on housing areas etc.).
Only through such a combination of environment-oriented planning and execution with later environmentally acceptable operation of the works, can a lasting contribution be made towards improving economic conditions.
Beseitigung von Ölschlamm nach einem Tankerunfall/Allgemeine Grundlagen der Ölbekämpfung, Mitteilungen aus dem Niedersächsischen Landesamt für Wasserwirtschaft, Hildesheim, Heft 1, 1986.
Boltz: Oberflächenbefestigung und Fahrbahndecken im Hafen, Handbuch für Hafenbau und Umschlagtechnik, Band VI, 1961.
Bundesimmissionsschutzgesetz, BlmSchG: Gesetz zum Schutz von schädlichen Umwelteinwirkungen durch Luftverunreinigungen, Geräusche, Erschütterungen und ähnliche Vorgänge.
Commentz: Befestigung von Container-Umschlagplätzen, Handbuch für Hafenbau und Umschlagtechnik, Band XV, 1970.
Empfehlungen des Arbeitsausschusses: Ufereinfassungen EAU 1985, 7. Auflage., Verleger für Architektur und technische Wissenschaften, Ernst & Sohn, Berlin.
Fachseminar Baggergut: Ergebnisse aus dem Baggergut-Untersuchungsprogramm, Freie und Hansestadt Hamburg, Strom- und Hafenbau, 1984.
Hafentechnische Gesellschaft: Empfehlung des Anschlusses für Hafenumschlagsgeräte, 1977; Gesundheits- und Umweltschutz bei Umschlag und Lagerung von Schüttgütern und Häfen.
Hübler, Karl-Hermann und Zimmermann, Konrad Otto: Bewertung der Umweltverträglichkeit, Eberhard Blottner Verlag, Taunusstein, 1989.
Leo, R. et al.: Ölwehrhandbuch/Bekämpfung von Ölunfällen im Inland und auf See, Verlag K.O. Storek, Hamburg, 1983/87.
Maßnahmen für Bekämpfung von Ölverschmutzungen auf dem Wasser: Projektgruppe Systemkonzept des Ölunfallausschusses See/Küste Cuxhaven, 1980.
Praktikable Entsorgungsmöglichkeiten für Seeschiffe: Schiffsingenieur-Journal, 32. Jahrgang, 1986.
Umweltbehörde Hamburg: Der Hafen, eine ökologische Herausförderung, Internationaler Umweltkongreß, September 1989.
Contents - Previous - Next