Controversial plans by nuclear power station Hinkley Point C to dump mud from the Bristol Channel into the sea off Cardiff Bay could be carried out near Somerset instead.
EDF Energy wants to deposit hundreds of thousands of tonnes of sediment as part of works to install water cooling tunnels under the channel.
It is considering two locations - Cardiff Grounds, two miles off the coast from the Welsh capital, and a private disposal site off Portishead on the English side of the water.
The South Wales site is the closest to EDF's offshore dredging operations, the company said, but it is understood the Portishead site would also have enough capacity for the disposal of the sediment - although it is further away.
The Bridgwater-based nuclear plant said it would complete its application later this month, with a public consultation following afterwards. It plans to resume mud dredging later in 2021.
The original mud dumping by the power station caused a backlash by environmental campaigners in Wales in 2018.
An online petition attracted hundreds of thousands of signatures and led to Wales’ Senedd undergoing a full debate over the issue.
Campaigners were concerned the mud could be contaminated with nuclear waste.
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However, the claims were dismissed by EDF, Natural Resources Wales (NRW) and the Welsh Government, which said the sediment was no different to elsewhere in the channel and posed no threat to people or the environment.
EDF is making applications to NRW for the Cardiff Grounds licensed disposal site and to the Marine Management Organisation for the Portishead licensed disposal site.
The energy giant is planning to dump up to 469,000m3 of mud - compared to a previous estimate of 600,000m3.
Either Cardiff Grounds or Portishead will be used for the entirety of the disposal and the volume will not be split across the two sites.
EDF said its latest applications would include a full Environmental Impact Assessment (EIA) and the results and analysis of the latest testing of the sediment.
“Hinkley Point C is one of many companies - over many decades – which has dredged and deposited mud in the Bristol Channel for industrial or construction purposes,” an EDF spokesperson said.
“We will again comply with all requirements and fully support efforts to inform and explain the dredging work to the public.”
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EDF said it had tested the mud “beyond internationally recognised best practice”, including tests for pure alpha emitting particles and tritium.
"We believe it is right to go beyond technical arguments to provide the necessary public confidence that all concerns have been addressed," the spokesperson added.
According to the energy company, the mud has to be disposed of within the Severn Area of Conservation (SAC) in order to maintain the balance of sediment and mud in the area.
The decision on which site will be used will be made at a later date, EDF said, and will be driven by regulatory approval and project schedule.
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