- On 26th September 2019
- In General, Sediment Management, Water Management
- By William
If your project in ‘tidal’ water is managed by the Marine Management Organisation (MMO) and involves the movement or dredging of sediment, a sediment survey is often required to determine the quality of the sediment. To do this, samples are required for chemical and physical analysis. We’ve listed the steps below to help you in the process.
A step by step guide to sediment sampling for a Marine License:
- Develop a sampling plan and have it approved by the MMO
The MMO uses the OSPAR Guidelines to determine the number of samples and the depth of sampling required. This ensures the appropriate representation of the volume of sediment dredged or moved. Samples should be distributed spatially in the horizontal and vertical plain to ensure the best coverage. Exo Environmental always drafts a sampling plan on behalf of our clients that we submit to the MMO as part of the application.
- Find a laboratory for the analysis
Following from the approval of the sediment sampling plan by the MMO, a laboratory can be selected. Please note that the laboratory must be validated by the MMO and CEFAS. These validated laboratories used to be only CEFAS and the NLS, but now there are a few other laboratories validated. Further information on these validated laboratory can be found at: https://www.gov.uk/guidance/marine-licensing-sediment-analysis-and-sample-plans
- Prepare for sampling
Generally, the laboratories will send sample receptacles, which need to be clearly labelled and doubled bagged. The survey team will then use the sampling plan with the predetermined locations and depths, to obtain the sediment samples. Sampling locations, depths, conditions, dates and time need to be recorded with substantial accuracy. The team at Exo have received appropriate training to carry out sampling safely in any challenging environment. We utilise our Trimble GNSS with centimetre accuracy to log the sampling locations, and subsequently plot these on a map, processed with GIS.
- Use specialist and approved sampling equipment
At Exo Environmental we use specialist (industry standard) sampling tools, such as ‘Van Veen Grabs’, stainless-steel scoops for surface samples or stainless-steel and acrylic multi-samplers to obtain deeper samples. Each type of parameter (organic or metallic) will have their own bespoke receptable. During the sampling, the ‘Chain of Custody Form’ is kept up to date, as a survey record and information record for the laboratory.
- Safely transport samples
Samples need to be cooled or even frozen when stored. It is best to dispatch samples on the sampling date to ensure integrity of the samples. Samples are packed in a cooler box with cooling elements and plenty of wrapping to avoid any of the glass receptables breaking. Due to the time sensitivity of the samples being processed, samples cannot be sent to the laboratory on a Friday as they won’t be processed on the weekend, and the sampling campaign would have to be repeated.
Once the samples reach the laboratory via a 24 hour courier, they can then be logged and processed, ready for analysis on the predetermined suite described in the sampling plan. It is very conventional to analyse for heavy metals, organotins, total hydrocarbons (THC), polycyclic aromatic hydrocarbons (PAH), Polychlorinated Biphenyls (PCB) and particle size distribution.
- Interpretation of the results
Laboratory analysis generally takes between a week and 30 days to become available. These analysis results are then assessed against the current guidelines and action levels:
– Below action level 1: is regarded as inert and safe for the marine and human environment.
– Between action level 1 and 2: there could be some elevated concentration of parameters, sometimes due to background levels (geology), but possibly due to anthropogenic contamination.
– Above action level 2: the sediment could pose a risk to the marine environment and the project you had in mind can became a lot more complex, if not infeasible.
Regardless of this outcome though, a well designed sampling campaign can provide the necessary information early on and often allows for project design changes to work around any elevated values.
- Furthering your project
Now you know what quality the sediment has you can further plan your project. But remember, the sampling plan and analytical results are only valid for six months, so avoid delaying your project.
If you have any questions about sediment sampling, Marine Licences or similarly at inland waters, contact us for specialist advice. Or for more of our work on Marine Licensing take a look at our page: Consents & Licensing.