Severn Tidal Power The Severn Estuary has the second largest tidal range in the world. The possibility of harnessing that energy for power generation has been mooted from the 1800s. The latest proposals involve the building of a tidal lagoon at Swansea Bay, as a prelude to building several more near Cardiff, Newport and elsewhere. The developers have gone to great lengths to promote the scheme as being both environmentally and ‘people’ friendly. However, the Foundation is concerned over the high cost of electricity production, damage to fish stocks and the significant and permanent changes in the Bay. In Cornwall, there will be negative effects of quarrying the stone required to build the lagoon. If built, there may also be unresolved problems of siltation too. Read more on Severn Tidal Power.