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5th International SedNet conference 27th-29th May 2008, hosted and co-organised by NGI, Oslo, Norway

Urban Sediment Management and Port Redevelopment & Sediment in River Basin Management Plans


NGI_logoThe 5th International SedNet Conference was hosted and co-organised by the Norwegian Geotechnical Institute. It took place in Oslo, Norway. More than 50 presentations were given and about 40 posters were shown. The conference was attended by 180 sediment experts from 19 countries.

The first part of the conference was dedicated to the main title. Sediment in rivers, harbours and marine coastal zones in urban areas is often historically contaminated. Contamination originates from industrial activities, dockyard and harbour operations as well as discharges of municipal wastewater and urban surface water run-off. This ‘legacy of the past’ complicates the redevelopment of harbour areas and the waterfront of cities for housing or commercial purposes. A proper sediment management strategy is required that takes into account environmental risks associated with contaminated sediment as well as the identification of appropriate remediation options for use in the urban environment. Furthermore, European legislation increasingly requires the involvement of stakeholders, who may have conflicting viewpoints and concerns. How to manage such complexity? What challenges with regard to the management of contaminated sediments have been met and what experiences gained in port redevelopment cases in urban areas?
The second part of the conference was dedicated to the state-of-the-art on sediment management in river basin management planning. By this conference part a European discussion was continued which was started in 2006 in Venice with the SedNet Round Table Discussion “Sediment Management – an essential element of River Basin Management Plans”.

At the end of each session, the session chairman summarized the highlights or conclusions. It is foreseen to give a more in-depth summary in the Journal of Soils and Sediments in 2009.

Surveys (chairman Aivo Lepland, Geological Survey of Norway)
The importance of fine, clayey fractions became clear.
Combination of high-resolution acoustic techniques with sediment core data provides insights for reliable assessment of thickness and volume of sediments.
Sediment Profile Imaging (SPI) is a promising and quick tool for environmental monitoring of the seabed and capping.
Modelling of sediment spreading during dredging and deposition of dredged materials using hydrodynamics and sediment properties; verifications from the field are still required.

Solutions (chairman Audun Hauge, Norwegian Geotechnical Institute)
Capping is becoming a widely used remediation technique.
Focus on developing active caps.
Stabilization and solidification of dredged material in land reclamation gives good results.
Special recipies must be found for each situation.
For management of contaminated sediments in fjords with ongoing contaminant sources dredging is not the solution. Thin layer capping with sandy material is a better option.
“Remediation efficiency” tools can be useful for both pre-design assessment and post-construction monitoring of engineered caps.
Capping of contaminated sediments has the potential to severely alter the soft bottom fauna community structure.
Incorporating contaminant budget principles has been a good tool for communicating the progress and status of remediating activities for environmental authorities and stakeholders.
Design and construction aspects of remediation projects offer numerous insights and lessons for other projects of any scale.

Sediment Quality Standards (chairman Piet den Besten, Centre for Water Management, NL)
SQS require the incorporation of a huge number of scientific considerations (most of them valid, but making the work very complex).
As a consequence, use of SQS in the near future will still leave a lot of uncertainties.
Earlier evaluations of strong and weak points of the application of SQSs (e.g. Pellston workshop : Use of Sediment Quality Guidelines and Related Tools for the Assessment of Contaminated Sediments: Proceedings from the Pellston Workshop on Use of Sediment Quality Guidelines and Related Tools for the Assessment of Contaminated Sediments, 18-22 August 2002, Fairmont, Montana, USA. Editor Richard J. Wenning, SETAC 2005 (ISBN 1880611716, 9781880611715) seem to have been ignored. Concerns about the use of SQSs reported earlier are:
The ability to adequately predict the presence or absence of chronic toxicity to sediment-dwelling organisms under field conditions;
The ability of SQSs to predict effects caused by accumulation in foodchains;
Doubts whether SQSs can be used to demonstrate cause-effect relationships;
Concern whether SQSs based on particular endpoints can be used to predict other toxicity endpoints and mechanisms.
The linkage between SQSs and management objectives (WFD!) should be made clear (and be the joint product of stakeholders).
Application of SQSs as trigger values (in tiered approaches) is a way of getting around scientific discussion on the uncertainties of those SQS values.
A risk assessment framework based on the use of SQSs could also consist of two sets of SQS values: a high value, above which there will be no discussion about necessity of measures, and a lower value triggering further research.
The scientific community has shown many times the advantages of tiered approaches (with also the use of biological and ecotoxicological parameters).
Communication is needed about existing experience in EU countries with specific methods how to derive SQSs and the way these are used in risk assessment or in pass/fail quality assessment steps. More insight is needed in the benefits and in the disadvantages of these frameworks, thus enabling a better EU-wide discussion on the perspectives of a (rigid) sediment management system based on SQSs.

Emerging Issues (chairman Jos Brils, Deltares, NL)
Effective management not only requires a good understanding of the biophysical system, but also of the social system, and specifically of the dynamic and complex interaction between both systems. Hence, all stakeholders should be involved.
Spatial planning, such as port revitalisation, is a good opportunity to also address (contaminated) sediment issues. Hence, a ‘sediment check’ – like the water check (‘Watertoets’) in the Netherlands – should become obligatory in spatial planning.

Science for River Basin Management (chairperson Susanne Heise, BIS TU Hamburg-Harburg)
Sediment management objectives need to be driven by regional risk reduction aiming at improvement on river basin scale.
For regional risk reduction, research gaps need to be reduced and they comprise quality as well as quantity issues, as well as linking scientific assessment to decision support systems for stakeholders.
Important quality issues:
remobilization of contaminants from sediments
biological activity may have secondary effects by gas-production
Important quantity issues:
what happens during flood events e.g. with retention areas in terms of resuspension and setting of material (models may help us understand and generalize)
Decision support systems comprising tiered approaches, developed by scientists in cooperation with stakeholders are useful tools which are both economic and support sound science.
Extensive projects like Risk-Base and others stress the importance of RBM but integration of field-specific expertise and regional oriented perception still remains a challenge.

River Basin Management – Fundamentals (chairman Peter Heininger, Federal Insitute of Hydrology, Germany)
River basin in many respects represents the most appropriate unit for sediment management decision making.
Sediment management in terms of quality and quantity should receive due attention in River Basin Management Plans including programmes of measures. Exceptions from including sediment management into the plans should be justified.
As the plans of the 1st management cycle are now well developed it is time to analyse critically whether sediment management has been accounted for to the necessary extent. Conclusions for the 2nd and 3rd cycles have to be drawn.
There is a strong need for developing decision support tools for sediment management, e.g. to assist in balancing the costs and benefits of management options.
Efforts towards a better linking of river and coastal/marine management should be further intensified. The marine strategy aims at a “good environmental status” whereas the WFD aims at a “good ecological status”. This seems to be a progress in thinking.
A general knowledge base on risk assessment approaches and merging the concepts, approaches and models for specific risks (e.g. contamination, erosion) into a common scheme of integrated risk assessment at a river basin scale is required.
Geochemical mapping (monitoring), particularly of overbank sediments, may be a powerful tool to better understand particle bound fluxes and thus to develop management plans.

River Basin Management – Aspects of sediment quality (chairman Igor Liska, ICPDR, Austria)
Sediments play an essential role in urban river basins, however this is often neglected in the management policies. Water quality in municipalities is influenced by the presence of sediments and this has to be taken into consideration in preparation of river basin management plans.
Contaminated sediment remediation must be supported by an effective system of assessing the risks related to the manipulation with a dredged material to avoid any adverse impacts on the status of the water bodies.
High annual throughput of sediment remediation projects necessitates availability of appropriate expert and management systems for risk assessment of dredged material; these expert systems should include quality assurance aspects to guarantee compliance with the standards.

In his concluding speech, Axel Netzband, chairman of SedNet, remarked that SedNet has the aim to give attention to the issues that have come forward at the Oslo conference. The conference clearly showed that SedNet’s scope now is much broader than the original one. Not only are contaminated sediments in inland waters the main topic, but also sediment quantity management, and the scope reaches from the source of a river to the marine environment. SedNet is open for a very broad discussion and therefore would appreciate more active members. Anyone who is interested in playing an active role in SedNet is requested to contact the SedNet secretariat (marjan.euser@tno.nl).

EC Best Paper 2008 Award
At the end of the conference, the Environment Commission (EC) of the Central Dredging Association, CEDA, presented its 2008 Award for a contribution to the literature on dredging and environment at the SedNet conference. CEDA EC has established this award to stimulate the dissemination of good quality information related to dredging and the environment, including technical, regulatory and managerial aspects of dredging operations and dredged material management. The Prize is € 1000 in cash and the publication of the full paper in Dredging and Port Construction Magazine. The winning abstract was ‘The Oslo Remediation Project’ by Torild Jørgensen of the Oslo Port Authorty. The price was handed over by Anders Jensen, vice-chairman of the CEDA EC.

Abstracts and slides of the oral and poster presentations can be found on in the library.

Organising Committee
Piet den Besten, Centre for Water Management, The Netherlands
Gijs Breedveld, Norwegian Geotechnical Institute, Norway
Jos Brils, Deltares, The Netherlands
Marc Eisma, Port of Rotterdam Authority, The Netherlands
Audun Hauge, Norwegian Geotechnical Institute, Norway
Susanne Heise, TU Hamburg-Harburg, Germany
Peter Heininger, Federal Institute of Hydrology, Germany
Igor Liska, ICPDR, Austria
Hans-Peter Nachtnebel, University of Vienna, Austria
Axel Netzband, Hamburg Port Authority, Germany
Sue White, Cranfield University, UK