TonyK
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Posts: 6438
The artist formerly known as Four Track, Now!
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« Reply #49 on: October 27, 2021, 15:58:42 » |
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A causeway would, as pointed out before, be phenomenally expensive. The risks, both economic and environmental, can be modelled, but have a great degree of the unknown about them. The much smaller Rance barrage has caused silting, and seen off a couple of species that previously lived in the estuary. Whether the power it produces swings the balance to positive depends on whether you are talking to an ecologist or a civil engineer, but the effects came as a slight surprise. A Severn Barrage could spring much greater surprises, or it might be perfectly fine, but the uncertainty is probably more than enough to put off private investors. Government knows that if it promoted the barrage, the battle between green power lovers and nature lovers would go on for years before a decision could be taken, even longer than HS2▸ or Hinkley C. For these reasons, I doubt it will happen.
The first tunnel seems to have been a mistake that won't be repeated, even if the engineers of the day did get away with it. A new one would, as stated earlier, need a much more sophisticated design of twin bores or escape towers mid-river, and extra Severn bores don't come cheap.
That leaves a bridge as the favourite. I doubt that it could incorporate wind turbines, as they need regular maintenance, and there is a risk of bits dropping off. Not a high risk, but enough to preclude a rail service. I can't see the benefit would justify the cost as things stand, even though the engineering would be much simpler than for a barrage or tunnel.
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