London Convention Guidelines for Assessment of Dredged Material

PIANC-Dredged MaterialManagement Guidance Documents

Robert.m.engler@erdc.usace.army.mil

Specific Guidelines forAssessment of Dredged Material

Introduction

Dredging is essential to maintain navigation in ports, harbours, marinas and inland waterways; for the development of port facilities; for flooding mitigation; and for removal of sediments from structures, basins and water intakes. Dredged material worldwide is, by nature, similar to undisturbed sediments in inland and coastal waters. A smaller proportion of dredged material, however, is contaminated by human activity.

Evaluation of Need forDredging and Disposal

CAPITAL DREDGING - for navigation, to enlarge or deepen existing channel and port areas or to create new ones

MAINTENANCE DREDGING - to ensure that channels, berths or construction works, etc., are maintained at their designed dimensions; and

CLEAN UP DREDGING - deliberate removal of contaminated material for human health and environmental protection purposes.

The schematic provides a clear indication of the stages in the application of this guidance where important decisions should be made.Components are:1. Dredged material characterization2. Waste prevention audit and evaluation of disposal options3. Is material acceptable4. Identify and characterize dump-site5. Determine potential impacts and prepare impact hypothesis(es)6. Issue permit7. Implement project and monitor compliance8. Field monitoring and assessment (monitoring)

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DREDGED MATERIAL

CHARACTERIZATION SOURCECONTROL

NEED FOR DREDGING

IS MATERIAL

ACCEPTABLE?

BENEFICIAL USE

POSSIBLE?

CAN MATERIAL

BE MADE ACCEPTABLE?

OTHER

BENEFICIALUSE

NO

YES

NO

YES

NO

YES

IDENTIFY AND CHARACTERIZE DISPOSAL SITE

DETERMINE POTENTIAL IMPACTS AND PREPARE IMPACT HYPOTHES(UE)S

NO

ISSUE

PERMIT? NO

YES

IMPLEMENT PROJECT & MONITOR COMPLIANCE

FIELD MONITORING & ASSESSMENT

YES

For dredged material, the goal of waste management should be to identify and control the sources of contamination.

SOURCE CONTROL STRATEGY1. The continuing need for dredging;2. The hazards posed by contaminants and the relative contributions of the individual sources to these hazards;3. Existing source control programmes and other regulations or legal requirements;4. Technical and economic feasibility;5. The evaluation of the effectiveness of measures taken; and6. Consequences of not implementing contaminant reduction.

Waste Prevention Audit

• Reduce or control impacts to a level that will not constitute unacceptable risks

• Treatment

• Disposal management techniques

• Methods of containing dredged material in a stable manner

• The practical availability of other means of disposal should be considered in the light of a comparative risk assessment involving both dumping and the alternatives

Management Options

Physical characterization• The basic physical characteristics required are the amount of material

Exemptions from detailed characterization• Dredged material is excavated from a site away from existing and historical sources of appreciable pollution, so as to provide

reasonable assurance that the• dredged material has not been contaminated, or• dredged material is composed predominantly of sand, gravel and/or rock, or• dredged material is composed of previously undisturbed geological materials.

Dredged Material Characterization

• Available information

• Geochemical characteristic

•Contaminant routes /sources

Chemical Characterization

Biological tests should incorporate:

• Acute toxicity

• Chronic toxicity and sub-lethal effects

• The potential for bioaccumulation

• The potential for tainting

at and in the vicinity of the disposal site.

Biological Characterization

• Chemical and/or biological screening resulting in:- Wastes containing specified substances, or causing biological responses, exceeding the relevant

upper level shall not be dumped, unless made acceptable.

- Wastes which contain specified substances, or which cause biological responses, below the relevant lower levels should be considered to be of little environmental concern.

- Wastes, which contain specified substances, or which cause biological responses, below the upper level but above the lower level require more detailed assessment before their suitability for dumping can be determined.

Action List

Site Selection Considerations:• Physical, chemical and biological characteristics of the water-column and the seabed

• Location of amenities, values and other uses of the sea in the area under consideration

• Assessment of the constituent fluxes associated with dumping in relation to existing fluxes of substances in the marine environment

• Economic and operational feasibility

Dump-Site Selection

• The shoreline and bathing beaches• Areas of beauty or significant cultural or historical importance• Areas of special scientific or biological importance, such as sanctuaries• Fishing areas• Spawning, nursery and recruitment areas• Migration routes• Seasonal and critical habitats• Shipping lanes• Military exclusion zones• Engineering uses of the seafloor

Important Amenities, Biological Features and Uses of the Sea

• Size of the dump-site

• Site capacity

• Evaluation of potential impacts

• Contaminant mobility

Site Selection Consideration

• Impact hypothesis

• Integrate waste characteristics / site information

• Comprehensive assessment

• Emphasis on biological effects / habitat modification

• Cumulative impacts

Assessment of Potential Effects

Compliance monitoring,Field monitoring•Modify or terminate the field-monitoring programme

•Modify or revoke the permit

•Redefine or close the dump-site

•Modify the assessment basis

Monitoring

• The types, amounts and sources of materials to be dumped

• The location of the dump-site(s)

• The method of dumping

• Monitoring and reporting requirements

Permit and Permit Conditions

• Assessment framework (LC)

• Material characterization

• Sustainable relocation

International NavigationAssociation PIANC

Dredged Material Management Guide(Supplement to Bulletin no. 96, 1987

• Management options

• Contamination source control

• Management strategy

• Relevant background literature

• Aquatic (LC guides)

• Land-based confined disposal- Contaminant release mechanisms- Processes- Pathways- Isolation- Surplus water treatment

Disposal

• Implementation guidelines

• Monitoring (physical and environmental)

• Evaluation

• Optimization

Confined Disposal Site Management

• Pretreatment

• Biological

• Chemical

• Thermal

• Immobilization

Treatment

• Beneficial or adverse

• Long- or short-term

• Direct or indirect

• Reversible or irreversible

• Local or strategic

• Independent or cumulative

Impact Assessment

• Specification of baseline conditions

• Port operational monitoring

Monitoring

International NavigationAssociation

PIANC

Management of AquaticDisposal of Dredged Material

(Working Group 1 - 1998)

1. Introduction2. Management framework3. Dredged material and site characterization

Outline

• Survey and sampling methods• Dredged material characterization

- Physical- Chemical- Ecotoxicological- Biological

Outline (cont.)

• Characterization of disposal site- Physical- Chemical- Biological- Functional uses of receiving area

Outline (cont.)

• Effects of disposal- Physical processes- Physical effects on ecology- Chemical and ecotoxicological- Functional uses / amenities

Outline (cont.)

• International, regional and National environmental controls

- General approaches- Marine and estuarine disposal- Inland waterways disposal

• Planning and engineering for aquatic disposal- Regulatory decision framework- Technical decision framework- Project decision framework

• Operational aspects of aquatic disposal- Operations plan- Monitoring requirements

• References

• Annexes- Description of physical properties of dredged material- Metals in sediments- List of international agreements, protocols and guidelines- Beneficial uses of dredged material in the aquatic environment- Mitigation measures- Consideration in design of monitoring plans

Managing ContaminatedDredged Material

• Defining CDM

• Risks

• Chemical characteristics and sources

Identifying, Assessing, andSelecting Options

• Planning CDM projects

• State-of-the-art technologies

• PIANC technical position

• Documenting results with case studies

Dredging: The Environmental Facts

Where to Find What You Need to Know

• Dredging a vital process

• Dredging for sustainable development

• Dredging must be safe and sound

Sources of Information

• CEDA

• IADC

• WODA

• PIANC

• IAPH

• WEDA

• EDA

• CEDA

• IAPH

• WEDA

• EDA