Back to the drawing board

Gerry Brooke takes a look back at the many schemes for a

Severn Barrage.

AFTER many years on the back burner, a barrage across the river

Severn from Brean Down, near Weston- super-Mare, to Lavernock

Point, near Cardiff, is now emerging as a real possibility.

Other plans envisage a barrage from Minehead to Aberthaw, or

a smaller one from Aust to Beachley, upstream of the old Severn

Bridge.

Another alternative option is a “tidal fence” with floating

turbines and a wave power station facing the incoming tide.

The Severn Tidal Power Group (STPG) – a consortium made up

of construction giants such as Sir Robert McAlpine and Taylor

Wimpey – backs the barrage idea.

A £9 million two-year feasibility study ends soon and a

shortlist of schemes will be announced in December.

But this isn't a new idea – not by any means. The concept

has been around for more than 150 years.

Victorian engineer Thomas Fulljames, for instance, proposed

one in 1849 from Aust to Beachley (now the site of the first

Severn Bridge), a span of just over a mile.

Rather than generating electricity this was based on the

need for a large, safe harbour, railways and flood

protection.

All went quiet until 1925, when an official study concluded

that the best place to barrage the Channel was at English

Stones, near the Welsh coast. Although considered technically

feasible, it was turned down on the grounds of its projected

£25 million cost.

A few years later, in 1931, Paul Shishkoff, a Russian

immigrant, showed off a prototype tidal generator at Avonmouth

which included a novel mechanism for spreading the power output

over 24 hours.

In the Forties, Nazi Germany even drew up plans for a Severn

barrage. It would, of course, have to win World War II

first.

Post war, in 1948, the Government took another look at the

options.

The scheme then was estimated at £60 million – but five

years later this had escalated to £200 million.

In 1971, Bristol tidal power expert Dr Tom Shaw proposed a

barrage from Brean Down to Lavernock Point at an estimated cost

of £500 million.

But four years later a Central Electricity Generating Board

(CEGB) study concluded that this wouldn't be economically

viable unless the country's energy situation deteriorated.

By now, of course, North Sea gas and oil was coming on

stream.

In 1981, with fuel costs rising, the barrage plans were

reinvestigated by a committee headed by Professor Sir Hermann

Bondi.

This looked at six possible locations, from the English

Stones down to Lynmouth in North Devon and Porthcawl in South

Wales.

The committee favoured Tom Shaw's 10-mile barrage between

Brean Down and Lavernock Point, with sluice and plain caissons

together with sand and rock-fill embankments.

In 1984, builder Wimpey Atkins came up with the idea of a

smaller barrage at English Stones which avoided the

environmental impact of a larger one.

But this was criticised because it would have caused too

much silting.

In 1987, Arthur Hooker, in conjunction with Parsons

Brinckerhoff, prepared a revised, cheaper scheme, a shoots

barrage, just below the Second Severn Crossing.

But even this, it was estimated, would cost between £1.4 and

£1.8 billion to build over some four years.

Portbury and Avonmouth would be unaffected, with smaller

locks allowing shipping access to the Sharpness canal and

Gloucester docks.

Electricity generation would be on the ebb tide.

A £4.2 million study by the STPG a few years later concluded

that the energy output from a Brean Down barrage – generated in

the flow direction – would be equivalent to about 18 million

tons of coal or three nuclear reactors.

A huge set of shipping locks would handle the largest

container vessels.

Construction costs over eight years (and employing some

35,000 workers) would be about £8 billion.

But environmental issues proved unacceptable and the plans

were shelved.

Of course the issues of global warming and soaring energy

prices have now made the economics much more favourable.

Two years ago, Welsh businessman Gareth Woodham submitted

plans for a Brean Down to Lavernock Point barrage. Featuring 14

electricity-generating turbines, a dual carriageway, a light

railway, four marinas and two lock gates, it would cost about

£650 million and take up to 20 years to complete.

Last October, the UK's Sustainable Development Commission

published a report looking at the potential of tidal power but

focusing on the Cardiff-Weston and the shoots schemes.

Following on from this came a proposal for a hydro-electric

barrier which would meet five per cent of Britain's power

needs.

This will culminate in a full public consultation in early

2010.

The estimated construction costs are huge, generally in the

£10 to £15 billion range, but have even been put as high as £23

billion.

Perhaps the Victorian engineers should have got on with it

after all.