Why do we need to dredge?

As part of the construction of Hinkley Point C, we will be dredging mud and sediment from the seabed off the Hinkley Point C site ahead of the drilling of six vertical shafts for the cooling water system. The cooling water system is a significant piece of infrastructure, which involves tunnelling more than 3km out into the Bristol Channel.

In order to do this, it is necessary to dredge the immediate area where we will be installing the vertical shafts. This process will take three to six months, and we will begin to dredge the area in summer 2018.

EDF Energy is one of many companies - over many decades - dredging and depositing sediment in the Bristol Channel for industrial or construction purposes.

The sediment we and others are dredging in the Bristol Channel is typical of the sediment found anywhere in the Bristol Channel, and as such it is no different to the sediment already at the Cardiff Grounds. It is not classed as radioactive under UK law and poses no threat to human health or the environment.

Is the mud and sediment radioactive?

The sediment is typical of sediment found elsewhere in the Bristol Channel, and under UK law it is not radioactive.

Radioactivity occurs naturally, including in foods we eat, and can be artificial / produced by human activities. Any sediment in UK coastal waters will contain naturally occurring levels of radiation, and in areas of industrial activity there may be extremely low levels of artificial radiation present.

In the case of the Bristol Channel, the very low levels of radioactivity identified in the sediment are predominantly naturally occurring (over 80%), with a small amount of artificial radioactivity, which will have originated from legacy discharges from hospitals, medical isotope manufacturing facilities (including those formerly based in Cardiff) and nuclear facilities. Whether the radioactivity is naturally occurring or artificial this has no impact on how it interacts with the human environment.

Who carried out the tests?

The tests were carried out by CEFAS, an executive agency of the UK Government. CEFAS has some of the most advanced radiation testing equipment in the world and also provides services to Natural Resources Wales and the Welsh Government, as well as the Marine Management Organisation for the English government.

Why Cardiff Grounds?

Why we are moving the dredged sediment to Cardiff Grounds, why not somewhere else?

While there are other licensed disposal sites in the Channel, the Cardiff Grounds is the only suitable site large enough to handle the amount of the type of sediment we will dredge, and as the sediment was confirmed to pose no environmental or health risks there is no need to relocate it elsewhere.

Cardiff Grounds has been a licensed disposal site since the 1980s, and takes on average 1,500,000m3 of sediment each year. It is important to emphasise that EDF Energy is not the only company licensed to use the Cardiff Grounds - the site will have received several million cubic meters of dredged sediment from other parts of the Bristol Channel over several decades.

Why not relocate the sediment further out to sea or elsewhere?

The area we are dredging is within a recognised Special Area of Conservation (SAC). Any sediment removed from this area, must be put back into this area in order to maintain the natural balance of sediment in the SAC.

Within this SAC, the Cardiff Grounds are the largest and only suitable grounds to deposit sediment from EDF Energy and other companies conducting dredging in the Channel.

Taking account of the natural and artificial radioactivity together, the dose recieved would be:

10,000

times less than a pilot's annual dose

750

times less than the average Radon dose in Pembrokeshire

Equivalent

to eating 20 bananas per year

This is an infinitesimally small level of exposure to radiation, far below the threshold requiring a more detailed assessment or even close to approaching a radiation dose that could impact human health or the environment.

The testing process

YearActivityResult

2009

CEFAS obtained sediment samples at depths up to 4.8m as part of the HPC Planning Application.

Levels of radioactivity in the sediment are found to be so low they equate to ‘not radioactive’ in law. In addition, no artificial radioactivity was observed below 2m.

2013

Natural Resources Wales commissioned an independent analysis by CEFAS to determine the radioactive characteristics of the sediment to assess the licence application. 17 sediment samples were taken in 2013.

Levels of radioactivity in the sediment are found to be so low they equate to ‘not radioactive’ in law.

2017

EDF Energy commissioned CEFAS to undertake a analysis as required, and approved, by NRW to support the Licence. 12 sediment samples were taken in May 2017.

Levels of radioactivity in the sediment are found to be so low they equate to ‘not radioactive’ in law.

 

How thorough were the tests?

The tests were carried out by CEFAS, which carries out work to the highest international standards.

The analysis techniques used detect the presence of alpha, beta and gamma emitting radionuclides (atoms that have excess nuclear energy which makes them unstable), rather than just testing for a few select radionuclides. Simply put, if a radionuclide is present it will be detected by the testing equipment.

Depth of the tests

The sediment has been tested at depth. In 2009 CEFAS obtained sediment samples at depths up to 4.8 m to support the HPC Planning Application. No artificial radioactivity was observed below 2 m This is likely because any sediment at a depth of greater than 2 m depth will have accumulated hundreds if not thousands of years ago, prior to the start of industrial activity in the area. As a consequence repeated testing to greater depth is not required.

As the surface sediment samples contain both the naturally occurring radionuclides and a small portion of artificial radionuclides these therefore provide a conservative estimate of the radioactivity in the sediment for the purpose of assessing its suitability for the disposal at the Cardiff Grounds.

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Contact us

The best way to contact us is by completing our online enquiry form.

Call us on 0800 096 9650 (24 hour free phone number)

Stop by our visitor centre in the Angel Place Shopping Centre, Bridgwater, TA6 3TQ. We are open from 9:00am-4:00pm Monday to Friday and 10am-1pm on Saturday

Drop in between 10:00 am and noon at Stogursey Church Rooms on the first Friday of each month

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Hinkley Point Visitor Centre, Angel Place Shopping Centre, Bridgwater, TA6 3TQ

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