All reports and papers produced by the Sullied Sediments partnership can be viewed and downloaded here.
Few national regulations in Europe require ecotoxicological tests when assessing sediment quality or deciding about the fate of dredged material (den Besten et al. 2003; den Besten 2007; Heise et al. 2020). While scientists argue that ecotoxicological data will improve the environmental safety of dredged material management decisions compared to a solely chemical data based framework, stakeholders claim that reproducibility, precision and accuracy of ecotoxicological data warrant a critical assessment before costly decisions are based on potentially unreliable information. In order to assess the reliability of biotest results from testing natural sediments, several investigations were carried out in the course of the Sullied Sediments project, which are discussed in this report.
The data that have been compiled in Sullied Sediments and the conclusions drawn from it confirm that sediment assessment and management is not a straightforward process. Decisions on the fate of contaminated sediment (and dredged material) are usually required within a certain time window and cannot wait until science has understood completely how contaminants and the biotic environment interact. Consequently, they have to be based on uncertain data including chemical threshold values and bioassays. In order to assess in what status the biological community is, we have to look at the diversity of organisms in the sediment, but even this does not tell us everything what we need to know. None of the tools that we have available so far – chemical, ecotoxicological and ecological – are perfect. All have their strengths and limitations. Combining the information from all three tools, however, will reduce the uncertainty in decision making and the probability to make a false decision.
One of the objectives of the Sullied Sediments Project was to develop a “better assessment” framework for sediments that is environmentally-safe but does not increase costs for managers. Work Package 3 - Better Assessment investigated whether such a framework would need to be biological effect based and whether chemical data should be complemented with biological community evaluation and ecotoxicological information. In order to provide the data to answer this research question, 6 sediment sampling surveys were carriedout in each of 3 different catchments at 3 sites with very different historical background and chemical‐physical characteristics. For each sediment, about 130 chemical contaminants were analysed, up to 10 bioassays performed and 2 biological community indices determined. This report focusses on the added value of ecotoxicological testing for assessing the hazardous properties of sediments, in order to derive a more reliable sediment classification.
In this paper, the Radboud University-led team describe our activities in the Sullied Sediment project, co-financed by the EU Interreg VB North Sea Region Programme’s third priority, which is focused on a Sustainable North Sea Region. The team shows how chemical, toxicological and ecological indicators can be related to each other and provide recommendations on selecting problematic substances and sites as well as incorporating assessment tools in monitoring. The outcomes have been discussed with water management and will be continued to be shared in implementation activities. In addition, the information used and obtained has been made available as reports (in English, German, Dutch and French), articles, datasets, beta-versions of models, videos and presentations at:
The Watch List Chemicals (WLCs) are a class of substances that have been highlighted under the EU Water Framework Directive as potential pollutants that require investigation to determine the risk they may pose to the aquatic environment and organisms living within it. Specifically, these chemicals are highlighted within this project to raise the discussion as to whether Environmental Quality Standards (EQS) should be set for them and their presence in waterbodies routinely monitored. This report represents a measured way of looking at such chemicals that sits in between ignoring them and rushing in and developing legislation based on historically limited data.
This report is a summary of the different contributions from OVAM to Work Package 3 - Sediment Assessment and Work Package 4 - Clean Up Pilots. The initiatives are all situated within the goal of developing better decision tools on risk assessment and remediation of contaminated sediments. The contributions of OVAM are mainly desktop studies that bring together existing knowledge into new guidelines and tools that support decision making.
Every year, a destination is sought for large quantities of dredged sediments. Many valorisation routes have been mapped out, but still too little sediment is finding its way to the market for beneficial use. VLAKWA, the Flanders Knowledge Center for Water, focusses on the environmental, policy and legal aspects concerning the reuse of dredged sediments. The aim of this co-creation project is to look for new solutions for sediment policy. To this end, an exploration has been set up from a systemic perspective. By identifying underlying mental models (in addition to events, patterns, etc.) , the deeper problems (with the associated opportunities) have been explored. This provided a widely broadened and enriched view of the factors that underlie a number of persistent mechanisms within this policy field and provides a broader view of possible causes. A non-exhaustive range of possible systemic levers have been listed throughout this report and may be explored further - preferably in a co-creative context. The above challenge is a valorisation problem. The need for valorisation tracks, due to the large amount of dredged sediments, however, is a social choice: we are dredging to provide a sufficient draft for shipping, because of coastal protection, to ensure efficient water drainage, etc. Functions that in the light of climate change and in case of an approach will increase in importance.
In order to make, in the short term, the right choices for the long term, it is necessary to build up a shared understanding of the main underlying processes that contribute to these volume of sediments, the dynamics that play a role in the reuse and, if possible, how these dynamics are (or will be) influenced by climate change.
In order to increase this understanding, OVAM has set up an additional trajectory to get a clear picture of the complexity of the problem and to identify solution corridors. To this end, several co-creation sessions were organised at Flemish and European level, starting from the joint creation of a connection map. The full report of this trajectory is added as appendix.
The Flemish Region has harmonised the legal framework with regard to the reuse of sediments by integrating the reuse of sediments into the existing legal framework for the reuse of excavated soil. The legal framework of the reuse of excavated soil in the soil legislation has been positive both on the practical side (harmonised and predictable framework for the sector) as on the environmental side (protection of the soil's functions for man and environment). These positive effects were the aim of the integration of the legal framework for the use of sediments in the soil legislation. The decision on how and where to reuse sediment is based both on the chemical and physical (construction/technical) assessment. Additionally the Flemish legislation foresees an economical evaluation as well. The potential for valorisation is assessed on the basis of the theoretical, technical, economical and implementation potential. Subsequently, the cost of using this potential is compared with the cost of using other or primary materials.
The desk study aims to provide tools to European sediment remediation experts, policy makers, industrial companies, waterway managers and private individuals to support decisions regarding management, removal and disposal of contaminated sediments, thereby reducing economic costs and the impact of contaminants on the environment. It was prepared by a consortium consisting of sediment remediation experts from the engineering and consultancy company Witteveen + Bos N.V. and the environmental contractors DEME-DEC, Jan De Nul-Envisan and Ghent Dredging. The report is published as a reference document and the results from the study have been used for the construction of an online decision support tool (BOSS-WB). The decision support tool for sediment remediation techniques (BOSS WB) is developed by VITO on behalf of OVAM.
Arcadis Belgium NV and Witteveen+Bos Belgium NV developed a decision tool for the management of sediments contaminated with contaminants of emerging concern. The decision system described in this report focuses on the Flemish soil framework, however, the principles on which this system is based are widely applicable in other standardization frameworks. The study provides a method for risk analysis and risk management (both in situ and ex situ) with background information to support a framework of threshold values (soil remediation standards, values for Free use, values for reuse as raw material). Watercourse managers who have analytical data can evaluate it to make informed decisions. This framework for threshold values makes it possible to place the use of the sediments in the end of waste framework. The method (approach, strategy) used is elaborated in a code of good practice that describes the approach for substantiating the threshold values for the reuse of sediments contaminated with new substances of emerging concern. The code of good practice enables a soil remediation expert to derive threshold values for the reuse of sediments contaminated with emerging and priority substances. The full report of this methodology is added as appendix.
The measured content of mineral oil in sediments often exceeds the threshold that allows the reuse of sediments. The high content can be caused by measuring biogenic mineral oil instead of petrogenic mineral oil. A procedure is validated to ensure that sediment samples are not wrongly classified as contaminated. The clean-up technique for mineral oil in sediments and the removal of biogenic interferences has been investigated and validated. The procedure seems suitable for the analysis of sediment (soil) samples with (slightly) elevated levels of mineral oil (cf. CMA/3/R.1) from locations where contamination with mineral oil of petrogenic origin is very unlikely. By applying the proposed clean-up method, it can be proved that the mineral oil is of biogenic origin.
Many hazardous substances accumulate in sediments and may cause adverse ecological effects in situ and – if taken out of the system – ex situ. When their concentrations exceed the respective national regulation, they tend to increase dredged material management costs. It has been suggested to put more emphasis on the effects that chemicals have rather than to focus solely on concentration data. In current European national regulations, however, the extent to which information on ecotoxicological effects are used in sediment quality and dredged material assessment ranges from “none” to “being an equally important line of evidence”. In this workshop, people from academia, regulatory bodies and harbour authorities were invited to discuss experiences, challenges and approaches regarding the use of biotesting and ecotoxicological data in assessment and decision frameworks.
In addition to this, the discussion and results from this workshop have been summarised in here.
The objectives of the workshop were (1) to compare existing regional or national regulations with regard to their components, decision making and consequences for the catchment management, and (2) to exchange experiences and difficulties with the different frameworks.