REPLACING protected habitats that could potentially be destroyed by the world's largest tidal energy project could cost as much as £2 billion, a conference has heard.
A short-list of projects to harness power from the tidal range on the Severn Estuary, which could produce up to 5 per cent of the UK's energy needs, is out for public consultation.
A consultant hired by the Government to examine the massive renewable energy project in the South West acknowledged a thumping compensation package would have to be factored into final costs, which could run into tens of billions of pounds.
Peter Kydd, of consultants Parsons Brinckerhoff, said examining the environmental impact of the five shortlisted schemes – and the two "innovative" schemes in development – required "a bigger slice of work" than the engineering issues.
Environmentalists have long expressed concerns of the risks to the UK over the internationally-protected "soft-coastline", which is heavily populated by birds and fish rare.
Mr Kydd said one of the main reasons for the two-year feasibility study, which is not expected to end until next year, was that "we do not understand the environmental effect on the estuary".
Any development, which could take as long as 10 years to build, would have to compensate for displaced habitats. Mr Kydd said working on a ratio of replacing two hectares of habitat for every one destroyed by a tidal scheme, it "could be £1 billion or £2 billion".
A 10-mile barrage across the estuary from Cardiff to Weston-super-Mare is the most controversial on the shortlist.
"All options have an environmental impact," Mr Kydd added.
He made his comments at the South West and Wales region Institution of Civil Engineers conference in Bristol, which heard from each of the groups behind Severn tidal proposals that have been short-listed.
Aside from the environmental battle, other bones of contention raised included the impact on ships trying to get to the Port of Bristol – one of the country's largest docks.
The final shortlist is expected to be confirmed in June. At present it includes barrages and lagoons fitted with turbines, as well as two ideas that the Department for Energy and Climate Change has yet to rule out entirely.
They are a tidal reef – proposed by Cornwall firm Evans Engineering – and a tidal fence.
Protestors fear for the estuary's inter-tidal habitats, fish such as the shad, European eel and salmon, and the migratory birds such as 7,000 geese that descend on the muddy banks each year.
Given the importance of the scheme to combating climate change, Government would be anxious to avoid costly and lengthy legal battles over the impact on the environment in protected areas.
At the conference, the RSPB's Mark Robins said: "This is not just about walks along the estuary, it is a starting point of facing the extinction of living species. We have got to have a debate about the impacts. This is a whopping great site that is important in the European and global context.
"The effect of high velocity turbines is that you end up with fish pate or fish soup."
The RSPB has argued that the tidal reef – which has a smaller difference between the high tide and low tide, or the so-called "head" – is much more environmentally-friendly.
Rupert Armstrong-Evans, the Cornish engineer behind the reef design, said the "crown jewels" of ship ports, fish and habitats were so important the tidal scheme needed to be designed around them.