OSPAR CONVENTION FOR THE PROTECTIONN OF THE MARINE ENVIRONMENT OF THE NORTH-EAST ATLANTIC

　

Ministerial Meeting of the OSPAR Commission

SINTRA: 22-23 JULY 1998

OSPAR Guidelines for the Management of Dredged Material
(Reference Number: 1998-20)

　

Preface

1. Introduction

2. Scope

3. Requirements of the 1992 OSPAR Convention

4. Evaluation of Need for Dredging and Disposal

5. Dredged Material Characterisation

6. Contaminant Source Evaluation and Control

7. Dredged Material Sampling

8. Evaluation of Disposal Options

9. Sea Disposal Site Selection

10. Assessment of Potential Effects

11. Permit Issue

12. Monitoring

13. Reporting

14. Flow Diagram

　

Background information and supplementary literature to the OSPAR Guidelines for the Management of Dredged Material

Technical Supplements to the draft revised OSPAR Guidelines for the Management of Dredged Material

Technical Annex I:	Analytical Requirements for Dredged Material Assessment
Technical Annex II:	Normalisation Techniques for Studies on the Spatial Distribution of Contaminants
Technical Annex III:	Best Environmental Practice (BEP)

　

These guidelines were adopted at the 1998 Ministerial Meeting of the OSPAR Commission. Contracting Parties are obliged to take these guidelines into consideration in their authorisation or regulation procedures for dredged material. It will, however, be implicit that the detailed procedures described in the guidelines will not be applicable in all national or local circumstances.

　

　

1.1 Dredging is essential to maintain navigation imports and harbours as well as for the development of port facilities. Much of the material removed during these necessary activities requires disposal at sea. Most of the material dredged from within the OSPAR maritime area is, by its nature, either uncontaminated or only slightly contaminated by human activity (i.e. at, or close to, natural background levels). However, a smaller proportion of dredged material is contaminated to an extent that major environmental constraints need to be applied when depositing these sediments.

　

1.2 Within the framework of the Convention for the Protection of the Marine Environment of the North-East Atlantic (hereinafter called the 1992 OSPAR Convention), dredged materials have been listed in Article 3.2 of Annex II as being permitted to be dumped at sea.

　

　

2.1 The guidelines are designed to assist Contracting Parties in the management of dredged material in ways that will prevent and eliminate pollution and thus protect the maritime area. In accordance with the mandate of the OSPAR Commission, the guidelines specifically address the disposal of dredged material by dumping in the maritime area.

2.2 It is recognised that both removal and disposal of dredged sediments may cause harm to the marine environment, but removal by dredging is not covered by the 1992 OSPAR Convention. Nevertheless, Contracting Parties are encouraged to exercise control over both dredging operations, including sidecast and agitation dredging practices and disposal operations using a Best Environmental Practice (BEP) approach designed to minimise both the quantity of material that has to be dredged and the impact of the dredging and disposal activities in the maritime area- see Technical Annex III. Advice on environmentally acceptable dredging techniques is available from a number of international organisations e.g. the Permanent International Association of Navigation Congresses (PIANC).

2.3 In the context of these guidelines, dredged materials are deemed to be sediments or rocks with associated water, organic matter etc. removed from areas that are normally or regularly covered by water, using dredging or other excavation equipment.

2.4 The terms "dumping" and "disposal" are used in accordance with Article I (f) and (g) of the 1992 OSPAR Convention.

　

　

3.1 Article 2.1a requires Contracting Parties to take all possible steps to prevent and eliminate pollution and to take the necessary measures to protect the maritime area against the adverse effects of human activities so as to safeguard human health and to conserve marine ecosystems and, when practicable, restore marine areas which have been adversely affected.

3.2 Article 4 requires Contracting Parties to take all possible steps to prevent and eliminate pollution by dumping or incineration of wastes or other matter in accordance with the provisions of the 1992 OSPAR Convention, in particular as provided for in Annex II.

3.3 With regard to the dumping of wastes or other matter at sea that are permitted under Article 3(2) of Annex II of the 1992 OSPAR Convention. Article 4 (1)(a) of Annex II requires Contracting Parties to ensure that no such materials are dumped without authorisation or regulation by their competent authorities. In addition, Article 4(1)(b) of Annex II requires Contracting Parties to ensure that such authorisation or regulation is in accordance with the relevant applicable criteria, guidelines and procedures adopted by the Commission.

3.4 Furthermore, Article 4(3) of Annex II requires Contracting Parties to keep records and report to the Commission on the nature and quantities of wastes or other matter dumped at sea in accordance with Article 4(1) of Annex II and the locations and methods of dumping used. To this end, OSPAR has agreed on reporting formats for the submission of data on wastes dumped at sea.

　

4.1 There are a number of dredging activities which may give rise to the need to dispose of sediments. These include:

4.2 Before beginning a full assessment of the material and the disposal options the question should be asked "Is dredging necessary?". In the event of a subsequent full assessment indicating no acceptable options for disposal it will be necessary to re address this question in a broader context.

4.3 In addition, attention needs to be given to ensuring that the quantities of material needing to be dredged and disposed of at sea are minimised as far as is practicable. This is dealt with further in Technical Annex III under 'Optimise the disposed quantities'.

　

　

5.1 Guidance on the selection of determinants and methods of contaminant analysis, together with procedures to be used for normalisation and quality assurance purposes, will be found in the Technical Annexes. It is envisaged that developments in biological testing techniques might eventually provide sufficient information to assess the potential impact of the contaminants in the material, so that less reliance would need to be placed on chemical testing.

　

Exemptions from detailed characterisation

5.2 Dredged material may be exempted from the testing referred to in paragraphs 5.4 to 5.9 of these Guidelines (but note that the information listed in paragraph 5.3 below will still be required) if any of the criteria below are met:

Dredged material that does not meet one of these requirements will need further stepwise characterisation to assess its potential impact (i.e. see paragraphs 5.3-5.9).

　

Physical characterisation

5.3 The following information is required:

Evaluation of the physical characteristics of sediments for disposal is necessary to determine potential impacts and the need for subsequent chemical and/or biological testing (cf. Technical Annex I for further guidance).

　

Chemical characterisation

5.4 Sufficient information for chemical characterisation may be available from existing sources. In such cases new measurements may not be required of the potential impact of similar material in the vicinity, provided that this information is still reliable and has been obtained within the last 5 years. Details of the substances recommended to be determined are listed in Technical Annex I.

5.5 Considerations for additional chemical characterisation of dredged material are as follows:

5.6 Further information may also be useful in interpreting the results of chemical testing (cf. Technical Annex I).

　

Biological characterisation

5.7 If the potential impacts of the dredged material to be dumped cannot be adequately assessed on the basis of the chemical and physical characterisation and available biological information, biological testing should be conducted. Further detailed guidance on biological testing is provided in Technical Annex I.

5.8 It is important to ascertain whether adequate scientific information exists on the characteristics and composition of the material to be dumped and on the potential impacts on marine life and human health. In this context, it is important to consider information about species known to occur in the area of the disposal site and the effects of the material to be dumped and of its constituents on organisms.

5.9 Biological tests should incorporate species that are considered appropriately sensitive and representative and should determine, where appropriate.

　

Action List

5.10 The Action List is used as a screening mechanism for assessing properties and constituents of dredged material with a set of criteria for specific substances. It should be used for dredged material management decisions, including the identification and development of source control measures as described in paragraphs 6.1 to 6.3 below. The criteria should reflect experience gained relating to the potential effects on human health or the marine environment.

5.11 Action List levels should be developed on a national or regional basis and might be set on the basis of concentration limits, biological responses, environmental quality standards, flux considerations or other reference values. They should be derived from studies of sediments that have similar geochemical properties to those from the ones to be dredged and/or to those of the receiving system. Thus, depending upon natural variation in sediment geochemistry, it may be necessary to develop individual sets of criteria for each area in which dredging or disposal is conducted. With a view to evaluating the possibilities for harmonising or consolidating the criteria referred to above, Contracting Parties are requested to inform the OSPAR Commission through SEBA of the criteria adopted, as well as the scientific basis for the development and refinement of these criteria.

5.12 An Action List may include an upper and lower level giving these possible actions:

5.13 If dredged material is disposed of at sea when one or more criteria exceed the upper level, a Contracting Party should:

　

　

6.1 Contamination of estuarine and coastal marine sediments both as a consequence of historical and present day inputs presents a continuing problem for the management of dredged material. High priority should be given to the identification of sources, reduction and prevention of further contamination of sediments and should address both point and diffuse sources. Successful implementation of prevention strategies will require collaboration among national agencies with responsibility for the control of point and diffuse sources of contamination.

6.2 In developing and implementing the source control strategy, appropriate agencies should take into account:

6.3 In cases where there has been historical contamination or where control measures are not fully effective in reducing contamination to acceptable levels, disposal management techniques, including the use of containment or treatment methods may be required - see paragraphs 8.3 - 8.4 below.

　

　

Sampling for the purpose of issuing a dumping permit

7.1 Dredged material that is not exempted under paragraph 5.2 will require analysis and testing (cf. Technical Annex I) to obtain sufficient information for permitting purposes. Judgement and knowledge of local conditions will be essential when deciding what information is relevant to any particular operation.

7.2 A survey of the area to be dredged should be carried out. The distribution and depth of sampling should reflect the size and depth of the area to be dredged, the amount to be dredged and the expected variability in the horizontal and vertical distribution of contaminants. Core samples should be taken where the depth of dredging and expected vertical distribution of contaminants suggest that his is warranted. In other circumstances, grab sampling will usually be sufficient. Sampling from dumping vessels or barges is not advisable for permitting purposes.

7.3 The following table gives an indication of the number of separate sampling stations required to obtain representative results, assuming a reasonably uniform sediment in the area to be dredged:

Amount dredged (m3)	Number of Stations
Up to 25 000	3
25 000 - 100 000	4 - 6
100 000 - 500 000	7 - 15
500 000 - 2 000 000	16 - 30
>2 000 000	extra 10 per million m3

The number of sample stations can also be determined on the basis of the area to be dredged. The number of sample stations should take account of the exchange characteristics of the area; more samples may be required in enclosed and semi-enclosed areas and less in open areas.

7.4 Normally, the samples from each sampling station should be analysed separately. However, if the sediment is clearly homogenous with respect to sediment texture, it may be possible to analyse composite samples from two or more adjacent sampling stations at a time, providing care is taken to ensure that the results allow derivation of valid mean contaminant values. The original individual samples should, however, be retained until the permitting procedure has been completed, in case further analyses are necessary.

　

Frequency of sampling

7.5 If the results of the analyses indicate that the material is essentially 'clean', sampling in the same area need not be repeated more frequently than once every 3 years, provided that there is no indication that the quality of the material has deteriorated.

7.6 It may be possible, following assessment of the results of an initial survey, to reduce either the number of sampling stations or the number of determinants and still provide sufficient information for permitting purposes. If a reduced sampling programme does not confirm the earlier analyses, the full survey should be repeated. If the list of determinants is reduced, further analysis of the complete list of determinants is advisable every 5 years.

7.7 In areas where there is a tendency for sediments to exhibit high levels of contamination, analysis of all the relevant determinants should be frequent and linked to the permit renewal procedure.

　

　

8.1 The results of the physical/chemical/biological characterisation will indicate whether the dredged material, in principle, is suitable for disposal at sea. Where sea disposal is identified as an acceptable option, it is nonetheless important, reognising the potential value of dredged material as a resource, to consider the availability of beneficial uses.

　

Beneficial Uses

8.2 There is a wide variety of beneficial uses depending on the physical and chemical characteristics of the material. Generally, a characterisation carried out in accordance with these guidelines will be sufficient to match a material to possible uses such as:

The technical aspects of beneficial uses are well-established and described in the literature - see the references section.

　

Options for material for which criteria exceed the upper level

8.3 Where the characteristics of the dredged material are such that normal sea disposal would not meet the requirements of the 1992 OSPAR Convention, treatment or other management options should be considered. These options can be used to reduce or control impacts to a level that will not constitute an unacceptable risk to human health, or harm living resources, damage amenities or interfere with legitimate uses of the sea.

8.4 Treatment, such as separation of contaminated fractions, may make the material suitable for a beneficial use and should be considered before opting for sea disposal. Disposal management techniques may include placement on or burial in the sea floor followed by clean sediment capping, utilisation of geochemical interactions and transformations of substances in dredged material when combined with sea water or bottom sediment, selection of special sites such as abiotic zones, or methods of containing dredged material in a stable manner. Advice on dealing with contaminated dredged material is available from PIANC - see references.

　

　

9.1 The selection of a site for sea disposal involves considerations of an environmental nature and also economic and operational feasibility. Site selection should try to ensure that the disposal of dredged material does not interfere with, or devalue, legitimate commercial and economic uses of the marine environment nor produce undesirable effects on vulnerable marine ecosystems.

9.2 For the evaluation of a sea disposal site information should be obtained on the following, as appropriate:

Such information can be obtained from existing sources, complemented by field work where necessary.

9.3 The information on the characteristics of the sea disposal site referred to above is required to determine the probable fate and effects of the dumped material. The physical conditions in the vicinity of the sea disposal site will determine the transport and fate of the dredged material. The physico-chemical conditions can be used to assess the mobility and bioavailability of the chemical constituents of the material. The nature and distribution of the biological community and the proximity of the site of sea disposal to marine resources and amenities will, in turn, define the nature of the effects that are to be expected. Careful evaluation will allow determination of environmental processes that may dominate the transport of material away from the sea disposal site. The influence of these processes may be reduced through the imposition of permit conditions.

9.4 In some cases, dumping can augment existing effects attributable to inputs of contaminants to coastal areas through land runoff and discharge, from the atmosphere, resource exploitation and maritime transport. These existing stresses on biological communities should be considered as part of the assessment of potential impacts caused by dumping. The proposed method of dumping and potential future uses of resources and amenities in the marine receiving area should also be taken into account.

9.5 Information from baseline and monitoring studies at already established dumping sites will be important in the evaluation of any new dumping activity at the same site or nearby.

9.6 The use of open-sea sites at distant off-shore locations is seldom an environmentally desirable solution to the prevention of marine pollution by contaminated dredged material.

　

　

General

10.1 Assessment of potential effects should lead to a concise statement of the expected consequences of the disposal option (i.e., the Impact Hypothesis). Its purpose is to provide a basis for deciding whether to approve or reject the proposed disposal option and for defining environmental monitoring requirements.

10.2 This assessment should integrate information on the characteristics of the dredged material and the proposed disposal site conditions. It should comprise a summary of the potential effects on human health, living resources, amenities and other legitimate uses of the sea and should define the nature, temporal and spatial scales and duration of expected impacts based on reasonably pessimistic assumptions.

10.3 In order to develop the hypothesis, it may be necessary to conduct a baseline survey which describes not only the environmental characteristics, but also the variability of the environment. It may be helpful to develop sediment transport, hydrodynamic and other models, to determine possible effects of disposal.

10.4 For a retentive site, where the material deposited will remain within the vicinity of the site, the assessment should delineate the area that will be substantially altered by the presence of the deposited material and what the severity of these alterations might be. At the extreme, this may include an assumption that the immediate receiving area is entirely smothered. In such a case, the likely timescale of recovery or re-colonisation should be projected after disposal operations have been completed as well as the likelihood that re-colonisation will be similar to, or different from the existing benthic community structure. The assessment should specify the likelihood and scale of residual impacts outside the primary zone.

10.5 In the case of a dispersive site, the assessment should include a definition of the area likely to be altered in the shorter term by the proposed disposal operation (i.e., the near-field) and the severity of associated changes in that immediate receiving environment. It should also specify the likely extent of long-term transport of material from this area and what this flux represents in relation to existing transport fluxes in the area, thereby permitting a statement regarding the likely scale and severity of effects in the long-term and far-field.

　

Nature of the impact

10.6 All dredged materials have a significant physical impact at the point of disposal. This impact includes covering of the seabed and local increases in suspended solids levels. Physical impact may also result from the subsequent transport, particularly of the finer fractions, by wave and tidal action and residual current movements.

10.7 Biological consequences of these physical impacts include smothering of benthic organisms in the dumping area. In comparatively rare circumstances, the physical impacts can also interfere with the migration of fish (e.g. the impact of high levels of turbidity on salmonids in estuarine areas) or crustacea (e.g. if deposition occurs in the coastal migration path of crabs).

10.8 The toxicological and bioaccumulation effects of dredged material constituents should be assessed. Disposal of sediments with low levels of contamination is not devoid of environmental risk and requires consideration of the fate and effects of dredged material and its constituents. Substances in dredged material may undergo physical, chemical and biochemical changes when entering the marine environment and these changes should be considered in the light of the eventual fate and potential effects of the material. It should also be taken into account that disposal at sea of certain substances may disrupt the sensory capabilities of the fish and may mask natural characteristics of sea water or tributary streams, thus confusing migratory species which e.g. fail to find spawning grounds or food.

10.9 In relatively enclosed waters, such as some estuarine and fjordic situations, sediments with a high chemical or biological oxygen demand (e.g. organic carbon rich) could adversely affect the oxygen regime of the receiving environment while sediments with high levels of nutrients could significantly affect the nutrient flux.

10.10 An important consequence of the physical presence of dredged material disposal activities is interference with fishery activities and in some instaces with navigation and recreation. These problems can be aggravated if the sediment characteristics of the dredged material are very dissimilar to that of the ambient sediment or if the dredged material is contaminated with bulky harbour debris such as wooden beams, scrap metal, pieces of cable etc.

10.11 Particular attention should be given to dredged material containing significant amounts of oil or other substances that have a tendency to float following re- suspension in the water column. Such materials should not be dumped in a manner or at a location which may lead to interference with fishing, shipping, amenities or other beneficial uses of the marine environment.

　

　

11.1 If sea disposal is the selected option, then a permit authorising sea disposal must be issued in advance. In granting a permit, the immediate impact of dredged material occurring within the boundaries of the disposal site such as alterations to the local, physical, chemical and biological environment is accepted by the permitting authority. Notwithstanding these consequences, the conditions under which a permit for sea disposal is issued should be such that environmental change beyond the boundaries of the disposal site are as far below the limits of allowable environmental change as practicable. The disposal operation should be permitted subject to conditions which further ensure that environmental disturbance and detriment are minimised and benefits maximised.

11.2 The permit is an important tool for managing sea disposal of dredged material and will contain the terms and conditions under which sea disposal may take place as well as provide a framework for assessing and ensuring compliance.

11.3 Permit conditions should be drafted in plain and unambiguous language and will be designed to ensure that:

　

Management of the Disposal Operation

11.4 Where appropriate, disposal vessels should be equippod with accurate positioning systems. Disposal vessels and operations should be inspected regularly to ensure that the conditions of the disposal permit are being complied with and that the crew are aware of their responsibilities under the permit. Ships' records and automatic monitoring and display devices (e.g. blackboxes), where these have been fitted, should be inspected to ensure that disposal is taking place at the specified disposal site.

11.5 This section deals with management techniques to minimise the physical effects of dredged material disposal. The key to management lies in careful site selection and an assessment of the potential for conflict with other interests and activities. In addition, appropriate methods of dredging and of disposal should be chosen in order to minimise the environmental effects. Guidance is given in Technical Annex III.

11.6 In most cases, blanketing of a comparatively small area of seabed is considered to be an acceptable environmental consequence of disposal. To avoid excessive degradation of the seabed as a whole, the number of sites should be limited as far as possible and each site should be used to the maximum extent that will not interfere with navigation.

11.7 Effects can be minimised by ensuring that, as far as possible, the dredged material and the sediments in the receiving area are similar. Locally, impacts may also be reduced if the deposition area is subject to natural physical disturbance. In areas where natural dispersion is low or unlikely to be significant and where reasonably clean, finer-grained dredged material is concerned, it may be appropriate to use a deliberately dispersive disposal strategy to prevent or reduce blanketing particularly of a smaller site.

11.8 The rate of deposition of dredged material can be an important consideration since it will often have a strong influence on the impacts at the disposal site. It may therefore need to be controlled to ensure that the environmental management objectives for the site are not exceeded.

11.9 The infilling of depressions, deliberate capping or other contained methods of disposal of dredged material deposits may be appropriate in certain circumstances to avoid interference with fishing or other legitimate activities.

11.10 Temporal restrictions on dumping activities may be appropriate e.g. tidal and/or seasonal restrictions to prevent interference with migration, spawning or seasonal fishing activity. Silt screens have been used to reduce the impact of suspended solids levels outside working areas in estuaries in order to mitigate the impact of disposal on migratory fish. However, these have proved hard to manage effectively.

　

　

12.1 Monitoring in relation to disposal of dredged material is defined as measurements of compliance with permit requirements and of the condition and changes in condition of the receiving area to assess the Impact Hypothesis upon which the issue of a disposal permit was approved.

12.2 The effects of dredged material disposal are likely to be simiar in many areas, and it would be very difficult to justify (on scientific or economic grounds) monitoring all sites, particularly those receiving small quantities of dredged material. It is therefore more appropriate, and cost effective, to concentrate on detailed investigations at a few carefully chosen sites (e.g. those subject to large inputs of dredged material) to obtain a better understanding of processes and effects.

12.3 It may usually be assumed that suitable specifications of existing (pre- disposal) conditions in the receiving area are already contained in the application for disposal.

12.4 The impact Hypothesis forms the basis for defining the monitoring programme. The measurement programme should be designed to ascertain that changes in the receiving environment are within those predicted. In designing a monitoring programme the following questions must be answered:

12.5 The permitting authority is encouraged to take account of relevant research information in the design and modification of monitoring programmes. Measurements should be designed to determine two things:

The first of these questions can be answered by designing a sequence of measurements in space and time that circumscribe the projected zone of impact to ensure that the projected spatial scale of change is not exceeded. The second question can be answered by the acquisition of measurements that provide information on the extent of change that occurs outside the zone of impact after the disposal operation. Frequently, this latter suite of measurements will only be able to be based on a null hypothesis - that no significant change can be detected.

　

Feedback

12.6 Information gained from field monitoring, (or other related research studies) can be used to:

12.7 Concise statements of monitoring activities should be prepared. Reports should detail the measurements made, results obtained and how these data relate to the monitoring objectives. The frequency of reporting will depend upon the scale of disposal activity and the intensity of monitoring.

　

　

13.1 Reporting of permits issued and amounts of dredged material, dumped together with the associated contaminants, is required according to the 1992 OSPAR Convention - see paragraph 3.5 above. The characterisation process is designed to provide information for permitting purposes. However, it will also provide some information on the contribution of dredged material to total inputs and, at the present time, it is considered the only approach available for this purpose. It is assumed that materials exempted from analysis represent insignificant inputs of contaminants and therefore it is not necessary to calculate or report contaminant loads. See paragraph 3.5 for the basis of this reporting requirement.

13.2 Contracting Parties should also inform the Secretariat of their monitoring activities and submit reports when they are available.

　

FLOW DIAGRAM

Background information and supplementary literature to the OSPAR Guidelines for the Management of Dredged Material

　

GESAMP, 1982. Reports and Studies No. 16: Scientific Criteria for the Selection of Waste Disposal Sites at Sea.

International Association of Dredging Companies (IADC)/Central Dredging Association (CEDA), 1997. Environmental Aspects of Dredging, Guide 2a: Conventions. Codes and Conditions: Marine Disposal.

International Association of Dredging Companies (IADC)/Central Dredging Association (CEDA), 1997. Environmental Aspects of Dredging. Guide 3 (Investigation, Interpretation and Impact). ISBN 90-75254-08-3.

International Association of Dredging Companies (IADC)/Central Dredging Association (CEDA). Environmental Aspects of Dredging. Guide 4: Machines, Methods and Mitigation

PLANC, 1992. Beneficial Uses of Dredged Material: A Practical Guide, Report of Working Group No. 19.

PIANC, 1996. Handling and Treatment of Contaminated Dredged Material from Ports and Inland Waterways, Report of Working Group No. 17 of the Permanent Technical Committee 1 - Supplement to PIANC Bulletin No. 89.

PIANC, 1997. Dredged Material Management Guide. Special Report of the Permanent Environmental Commission- Supplement to Bulletin no. 96.

PIANC, 1998. Handling and Treatment of Contaminated Dredged material from Ports and Inland Waterways, Vol. 2., Report of Working Group No, 17 of the Permanent Technical Committee 1.

PIANC, in prep. Management of Aquatic Disposal of Dredged Material. Report of Working Group 1 of the Permanent Environmental Commission. (to be issued in September 1998)