Campaigners say sediment has not been tested properly and may do ‘irreversible harm’

An eclectic group of activists including scientists, surfers and a member of the Welsh band Super Furry Animals is attempting to halt the dumping of “nuclear mud” excavated as part of the vast Hinkley Point C construction project.

The activists are appearing in court in Cardiff on Tuesday to try to obtain an injunction to stop 300,000 tonnes of sediment from the power station site in Somerset being disposed of a mile and half from the Welsh capital.

If the legal action does not succeed, a Welsh assembly member, Neil McEvoy, is calling for boat owners to form a “people’s flotilla” to take direct action and blockade a sandbank called Cardiff Grounds, where the mud is being dumped. McEvoy has already boarded a barge disposing of the mud to try to block the operation.

Campaigners claim the mud has not been tested properly and could contain particles that may pose a health risk. They have dubbed the sediment “nuclear mud” and nicknamed the sea off Cardiff “Geiger Bay”, a play on “Tiger Bay”, the old slang name for the city’s docklands. One of their main concerns is that the sediment could be washed ashore in a storm.

EDF Energy, which is building Hinkley Point C on the English side of the Bristol Channel, along with the Welsh government and Natural Resources Wales (NRW) have insisted the mud is safe.

The legal action is being financed by crowdfunding and is being fronted by the keyboard player from Super Furry Animals, Cian Ciarán, who said he was angry and sad the mud was already being dumped at Cardiff Grounds.

He told the Guardian: “I’m involved as a Welshman and a concerned earthling. I felt compelled to play a part. I felt at a loss over the lack of action by the Welsh Labour government and the apathy of NRW. This is about reasonable people asking reasonable questions.”

Ciarán said he did not have faith in the international standards that EDF, by which the Welsh government and NRW said they were bound. “They try to convince us that the mud is safe and there’s nothing to worry about but I can’t take the nuclear industry’s word for it.

“The Welsh government has had ample opportunity to stop it but they haven’t. They’ve put their heads in the mud rather than sand.”

Ciarán said he had been out to Cardiff Grounds to view the mud dumping at close hand. “I felt angry, saddened, desperate. Potentially it’s causing irreversible harm,” he said.

Among those backing the objectors is the Emeritus Prof Keith Barnham, a distinguished research fellow in the physics department at Imperial College London, who argues it is possible that large amounts of uranium and dangerous levels of plutonium could have reached the mud when cooling water from the decommissioned Hinkley Point A was discharged.

Nuclear watchdog raises Hinkley Point C concerns Read more

Surfers from the Gower peninsula to the west of Cardiff were among those who joined a demonstration against the dump at the Welsh assembly last week.

At the demonstration, McEvoy, the independent assembly member for South Wales Central, called for boat owners to contact him to try to form a “lawful blockade” of the dumping ground. “We must make this out-of-touch Labour government listen,” he said. “The dumping should never have started and must be stopped.”

EDF said the mud had been tested by the Centre for Environment, Fisheries and Aquaculture Science (Cefas), an executive agency of the UK government, in 2009, 2013 and 2017, and the levels of radioactivity were found to be so low that they equated to “not radioactive” under British law.

A spokesperson said: “The mud is typical of sediment found anywhere in the Bristol Channel and no different to sediment already at the Cardiff Grounds site. It poses no threat to human health or the environment.”

EDF says it is dredging mud and sediment from the seabed ahead of the drilling of six vertical shafts for the cooling water system. It says Cardiff Grounds is the only suitable site large enough to handle the amount of the type of sediment it is dredging.

John Wheadon, the permitting service manager for Natural Resources Wales, said: “Every element of the application was considered thoroughly including testing of the sediment from the dredge sites by independent experts in accordance with international standards and guidelines, and advice from health experts. We’re confident the proposed activity will not harm people or the environment.”

A Welsh government spokesman said: “All tests and assessments concluded the material is within safe limits, poses no radiological risk to human health or the environment and is safe and suitable to be disposed of at sea.”

• This article was amended on 1 October 2018 because an earlier version described the physicist Emeritus Prof Keith Barnham as a physician. This has been corrected.