Cardiff Parkway: Final decision on St Mellons railway station
A major new railway station was planned to open in 2024 - instead, it will again go before planners who will decide if work can even get started.
It was estimated Cardiff Parkway would provide 6,000 jobs in St Mellons and could accommodate 800,000 passengers a year between Cardiff and London.
However, after changes to planning policy, the Welsh government said it merited re-looking at plans.
A planning hearing is on Tuesday and developers said they were frustrated.
Cardiff Parkway had long been described as a key development, linking passengers on the South Wales Metro network to north Wales, Bristol, Manchester and London, as well as potentially having eight trains an hour between Newport and Cardiff.
It was to be built on farmland between the two cities, near Cypress Drive in St Mellons.
East Cardiff currently has no railway station - there was one just over the council border in Marshfield, Newport, but this closed in 1959.
Cardiff council had given the green light to the development in April 2022, although concerns were raised about the impact on ecology and wildlife and the fact some buildings could be 15 storeys.
A hearing was held in July 2023 to see if it did comply with rules to protect the environment.
But after key changes were made to its planning policy in October 2023, the Welsh government decided it needed to be looked at in light of these, which is why Tuesday's hearing is going ahead.
A Cardiff Parkway spokesperson said: "Throughout the extensive planning process for Cardiff Parkway, we have remained convinced that Cardiff, and south Wales more broadly, stands to benefit significantly from major investment in transport infrastructure and new jobs that a new station and sustainable business district would bring."
They said they were disappointed the process has been extended again, adding: "Especially as we know that many people want quicker progress."
But the developers are hopeful that this hearing will finally reassure decision-makers and the "much needed development" can go ahead.
The key changes in the Welsh government's Planning Policy Wales includes a greater emphasis on the protection of green spaces, biodiversity and sites of special scientific interest (SSSIs).
Two specific SSSIs that could be affected are those at Rumney and Peterstone, according to the Local Democracy Reporting Service.
A group called Friends of the Gwent Levels said they were not convinced by the offer of compensation land in mitigation by the developers, claiming that the development would still put biodiversity in the area at risk.
They welcomed the decision to reopen the hearing.
A statement read: "The recent changes to Planning Policy Wales mean that building on a Site of Special Scientific Interest can now happen only in wholly exceptional circumstances.
"We do not believe that another business park in close proximity to existing business parks constitutes 'wholly exceptional circumstances', especially as there are currently literally hundreds of thousands of square feet of empty, unused office space in Cardiff."
The planning hearing takes place at County Hall, Cardiff, on Tuesday.
After it has concluded, the planning inspector will submit another report to Welsh ministers for consideration.
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