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Guidance Note 2: Sediment sampling requirementsLegislative ContextSediment Sample Requirements Appendix A Appendix B Legislative Context
The Water Framework Directive and implementing regulations will, in time, replace existing water quality legislation and will set requirements for continuous improvement to achieve good ecological status in all water bodies. The FEPA replaced the Dumping At Sea Act (1975) and represents the UK’s commitment to International Conventions on the environment including OSPAR (Convention for the Protection of the North East Atlantic) and the London Convention. While the WRA regulates effects on the water column, the FEPA is designed to protect the wider marine environment with particular emphasis on avoiding contaminant input to seabed sediments that may be taken up by sediment-feeding organisms and, via the food chain, consumed by humans. The assessment of the effects of sea Dredging operations themselves do not fall under either piece of legislation, being neither a discharge nor a disposal operation. However, dredging does involve releases of sediment to the water column (and therefore any sediment-bound contaminants) and may also redistribute contaminants from the sediment into the water column. The quantity and rate of sediment release varies according to the dredging methodology. A trailer suction hopper dredger (TSHD) releases sediment via the overflow of low density water, whereas a water injection dredger causes all the dredged material to be mobilised into the lower water column, while the release from a backhoe is limited mainly to sediment falling from its bucket. The type of sediment also affects the release rate since fine sediment will be lost and dispersed to a greater extent than coarser sands. Overflows from dredgers are specifically excluded from requiring FEPA consent. This may be because overflows were considered de minimis or that they would be covered by other legislation.
Sediment Sample RequirementsSample NumbersWithin the limits of the Port of London, dredging is regulated by the PLA (see Guidance Note 1 for details of the application process). The PLA considers that an assessment of the effects of dredging on water quality at the dredge site and the sediment quality of the receiving environment is an integral part of the licensing process. Therefore, the provision of sediment samples is a requirement of all new dredging applications and samples must be provided once every two years for ongoing maintenance dredging operations. The number of samples required is dependent upon the quantity of sediment to be dredged and guideline numbers are set out in Table 1 below, although the actual number required will be site specific.
Table 1 Samples should be taken from sites that are representative of the area to be dredged, for example, in a rectangular berth box, four samples could be taken from evenly distributed locations across the area. If an area is known or thought to be contaminated, sampling should include a site in the contaminated area, for example, adjacent to a slipway (see Figure 1 below).
Figure 1 - Examples of possible sample locations Berth operators should contact the PLA Environmental Scientist in advance for advice on the number and location of samples required. Samples should be taken in accordance with standard marine sediment sampling procedures. Provision of Sampling Equipment & Sample StorageTo ensure comparison of sample results and reduce the potential for error, berth operators are advised to employ a trained contractor. The contractor or analytical laboratory will provide the appropriate sample jars. It is important to store samples in such a way to reduce the possibility of chemical reactions occurring that could change the chemical nature of the original sample. In practice, this involves keeping samples cold (i.e. packaged with ice boxes) and freezing the samples as quickly as possible. Analytical laboratories will provide guidance on the specific requirements. Sample AnalysisThe analysis of sediment samples is complex and can be expensive. The PLA has selected a laboratory (Alcontrol Technichem) to undertake its own sample analysis, based on its ability to demonstrate appropriate quality control techniques at a reasonable cost. Applicants may wish to use this laboratory, as using a single laboratory ensures comparability between the results of the sediment analysis from different dredge locations, but others are available. Should a berth operator wish to use a different laboratory then he should ensure that it has the appropriate quality registration for analysing sediments for the necessary parameters (e.g. UKAS accreditation). There are different analysis requirements depending upon the eventual fate of the material. Appendix A should be used where material is to be retained in the water column or disposed of to a licensed marine disposal site (for marine disposal, samples may also be required by CEFAS). Appendix B contains additional parameters relevant to placement in land disposal sites. Detection limits and analysis requirements are shown for each parameter. Interpretation of Sediment Quality DataIn the absence of published sediment quality guidelines specifically relating to the effects of dredging on the water column and biological communities, the PLA has adopted the following approach: In the event that the sediment quality data falls above this acceptable level then further assessment will be undertaken. Depending on the level of contamination, this assessment would involve one or both of the following: |
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The WRA implements the European Directives on Dangerous Substances, Bathing Water and Shellfish Waters and enforces a set of criteria (Environmental Quality Standards, EQSs) for both individual discharges and the receiving waters. In this way, water quality is managed with a view to achieving acceptable standards.
disposal is undertaken by the Centre for Environment, Fisheries and Aquaculture Science (CEFAS), based on OSPAR’s Dredged Material Assessment Framework. This includes guidance on the number of sediment samples required for analysis. Sediment quality guidelines exist in the form of CEFAS Action Levels, although these are unpublished.
Although dredging does not fall directly within WRA or FEPA, it is controlled by licensing and that indirectly brings it within the scope of the Habitats Directive and Regulations, the Countryside and Rights of Way Act and the Harbours Act (s.48A) (see 
