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Marine licence to dispose dredged material off the coast of south Wales

  • Contrary to what you may have read on social media, the dredged material is not radioactive waste. It is sediment from the Bristol Channel sea bed at the Hinkley Point C power station site
  • It contains only a very small amount of radioactivity, most of which is naturally occurring, and is well within legal limits
  • Before we issued the licence in 2014, sediment samples were tested in line with international guidance. Results showed the material was suitable for disposal at sea, having been independently assessed by Cefas[1]
  • Samples of the sediment were tested again in 2017 and showed those results also showed the material was safe for disposal
  • We would not grant the licence if we weren’t satisfied that the activity could take place without harming the health of people or the environment
  • Our responses to detailed questions sent to us from Neil McEvoy AM can be found in this letter

What is the marine licence for?

The marine licence is to dispose dredged material from the sea bed at Bridgewater Bay in the Bristol Channel, into the Cardiff Grounds Disposal Site. This is an established disposal site for marine dredged materials off the coast of south Wales.

The source of the sediment is from the construction site of the Hinkley Point C power station off the Somerset coast in England.

Every element of the application was considered thoroughly. With the right Marine Licence conditions in place, we’re confident the proposed activity will not harm people or the environment.

We granted the licence in July 2014.

Why are you allowing this to be dumped near Cardiff?

Independent testing by radiological experts at Cefas have shown that the mud contains only a very small amount of radioactivity, most of which is naturally-occurring and not from the nuclear industry. It is also well within safe limits. There is no reason not to allow this to happen – the legal limits are place to protect people’s health and the environment.

What environmental assessments were made before the licence was granted?

The applicant was required to undertake a chemical and radiological assessment of the dredge sites.

Chemical contaminants were assessed against Cefas Action Levels[2], UK guidelines to assess dredged material and its suitability for disposal to sea. The Radiological Assessment followed the conservative generic radiological assessment procedure developed by the International Atomic Energy Agency (IAEA).

Cefas concluded that the material tested did not have unacceptable levels of chemicals or radiological materials and was suitable for disposal at sea.

We consulted with the Environment Agency (EA) as the lead regulator for Hinkley, and we both agreed it was a robust assessment of the radiological impacts and agreed with Cefas’s conclusion.

But if people are unhappy, why don’t you just suspend the licence?

We have no powers to suspend the licence unless we are presented with new evidence demonstrating that the mud contains radioactive levels above a certain threshold - and no such evidence exists. If we suspended the licence without that evidence we’d be operating illegally and the operator could challenge our decision through the courts. We can only act on evidence.

Why can’t it be dumped near its present site?

Sediment dredging operations are very common around the UK and Welsh coast, and the material needs to be disposed of at designated disposal sites. This means we can ensure the sediments are released at a suitable site and will not harm sensitive habitats or wildlife. By using a designated disposal site, we can also make sure sediment does not build up in one place, creating a hazard to shipping, for example. For the sediments coming from the Hinkley site, the Cardiff Grounds disposal site is the closest designated disposal site.  This will also make sure carbon emissions from transporting the material are kept to a minimum. 

Why does it have to come to Wales from England?

That is a political question and not a matter we can consider. If a company makes an application, we judge it on the evidence. Legally, we cannot refuse an application based on anything which is outside the Regulations with which we must comply.

In the case of Hinkley, the material is being dredged from the Severn Estuary, which is designated as a Special Area of Conservation (SAC). From a conservation point of view, it is preferable that material dredged in the estuary remains in the SAC as it supports wildlife and habitats. Our habitats do not have hard borders, and material in the estuary will mix between the English and Welsh waters. Keeping the material in the SAC is subject to the suitability of the material, which has been demonstrated though testing.

Why have you not tested for the three types of spectrometry (beta, gamma and alpha) as requested by Neil McEvoy AM?

The choice of method depends on the reason for analysis. For example, three methods are used for routine annual monitoring for ‘Radioactivity In Food and the Environment (RIFE)’ reports[3], which considers the people's exposure to radiation and is carried out annually on a National basis.

For dredging applications, an assessment is used (as the starting point) which only requires gamma spectrometry, and produces a very conservative estimate of dose. The other two methods would only be used if the dose limit was exceeded after undertaking the initial assessment. This was not necessary for the samples from the Hinkley dredge area as the dose limit was not exceeded. Further sampling would also be undertaken if the dose was exceeded and the assessment would be repeated to give a more accurate dose. 

Why don’t you conduct further tests, including from deeper samples?

The OSPAR (a name derived from the Oslo/Paris conventions regarding the disposal of waste) guidelines for the management of dredged material cover physical, chemical and biological characterisation of sediment to be dredged/disposed and the IAEA guidelines refer to radiological assessments.

The IAEA guidelines are based on expert knowledge. Many research programmes have been carried out for more than 40 years (and peer reviews published) to determine sources and behaviour of radioactivity below the surface sediment. The areas where radioactivity is known to have accumulated below the sediment surface is well known and documented in the scientific literature. There is no research (or monitoring) evidence to suggest that accumulation of radionuclides has occurred at any time around Hinkley.

For these reasons, five sample stations, including surface and depth samples down to 4.8 metres was considered appropriate. The 2009 depth samples have continued to be valid due to the deep sediments not changing. In 2013, 17 surface samples were collected and analysed and in 2017, 12 surface samples were collected and analysed as the area to be dredged had reduced.

The combination of these core samples and the additional 2013 surface samples provide a good representation of the material to be dredged, and we are content that this is in line with the OSPAR guidelines. Similarly, with the 2017 sampling, 12 surface samples were collected and analysed and considered in conjunction with the 2009 depth sampling as the material at depth would not have changed. The combination of surface and depth samples were used to determine the materials suitability for disposal at sea.

Our judgement on the number of sampling stations required for the 2017 analysis was based on the OSPAR guidelines, knowledge of the 2009 and 2013 sampling results, and the assessment that was undertaken in determining the marine licence application.

The aim of the sampling and analysis is to obtain representative results of the material to be dredged/disposed and we are content that this was obtained through the combination of the 2009, 2013 and 2017 sampling and analysis data.

But results from the few samples you have taken from depth show much higher radium levels. Why do you say it’s is OK to dump these off the coast of Cardiff?

Concentrations of uranium-238 and radium-226 might appear to be elevated in deeper sediments, in comparison to those at the surface, but these levels have still been assessed as within safe limits. If these apparently higher levels were used to calculate the effect on human health and the environment, the resultant dose would still be below threshold levels.

Why are you disputing the claims of some scientists?

The safe limits are defined by the International Atomic Energy Agency (IAEA) – following consultation with the international scientific community.

If the evidence shows that materials are within certain limits – deemed by the international scientific community to be safe levels - we have no option other than to grant a licence

If some scientists have evidence that these guidelines should be changed, they need to present this to the UK Government and their advisors.

How confident are you that the radioactive material in this mud will not harm the health of people in Cardiff and the wider Severn estuary?

We would not have granted a licence if we weren’t satisfied that there was no risk to people or the environment. There are only very low levels of radioactivity in this mud, which are well within the legal limits to protect people and the environment. Most of the radioactivity is naturally-occurring and not from the nuclear industry. The procedures used to determine the risk follow International guidelines and the method used is robust. The analytical methods used are fully accredited to an International standard, which are reviewed annually by the accreditation body to ensure quality is maintained. Public Health Wales and Public Health England were both consulted as part of the process and they, along with our partners the Environment Agency, are happy that this material poses no threat to people’s health or the wider environment.

Is it correct that you have no nuclear experts to advise you on this?

We run the permitting and licencing system in Wales to protect people and the environment. As part of that we consult in detail with expert organisations including Centre for Environment, Fisheries and Aquaculture Science (Cefas) the Environment Agency and Public Health Wales who have specialist radioactivity expertise. Their views are considered thoroughly before we issue a licence. If they had flagged any concerns during this consultation we would not have issued a licence.

So how can we have any confidence in your decisions?

Because the people we consult with are the experts and they follow internationally agreed guidelines. We trust their knowledge and expertise and are confident that they have given us the right advice.

What are the conditions in the licence that ensure that people and the environment are protected?

Samples of dredged material are tested every three years to meet international guidelines. The licence required the licence holder to submit a new sampling plan for our agreement if they wished to deposit dredged material after March 2016, when the original sample data would be three years old. The licence prohibits any disposal after March 2016 without our written permission, to allow us to act should the new sample results raise any concerns.

We agreed a new sample plan with the licence holder in January 2017, following advice from Cefas. The new plan also required a chemical and radiological assessment of the samples. This assessment has now been completed and we received the sample results in December 2017. We consulted with experts, including Public Health Wales, on the results of the latest analysis and are satisfied that the results show that the material is safe for disposal with no risk to people or the environment. 

The licence holder has an obligation as part of their licence to survey the disposal site before and after disposal to ensure the sediment they deposit has dispersed.  More details can be found in this survey plan.


If you would like further information on the licence, please email

Updated on 3 September 2018 


[1] Centre for Environment, Fisheries and Aquaculture Science

[2] Cefas Action Levels. Marine Licensing: sediment analysis and sample plans. GOV.UK. 11 October 2016

[3] Radioactivity in Food and the Environment report 2015. GOV.UK. 27 October 2016.

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