Letter: Concerns raised over West Somerset Lagoon proposal

It is understandable that the proposal for the West Somerset Lagoon has developed a large number of attractive economic benefits, ranging widely from reducing coastal erosion to improving tourism.

However, there has been no statement yet published of the possible environmental impact and other potential problems.

This is likely to make the project much more costly and it could even be unsustainable when fully investigated.

Before acceptance by the regulating authorities, both the benefits and the disbenefits would need significant research and advice, before submission of an environmental impact statement, a costly business.

A main concern is that the lagoon would reduce the tidal range to a certain amount throughout the estuary.

Reduction provides the energy that the lagoon's turbines utilise for electricity generation, the same as all other power schemes, including that of Hinkley C.

This reduction can be estimated by calculation from numerical mathematical modelling.

An obvious question would be whether this reduction could affect the estimated power output from Hinkley C power station once it starts.

To maintain the original electricity output for a reduced tidal range would involve either increasing the cooling water discharge rate or allowing higher temperatures to be emitted, both of which may have significant environmental repercussions.

Additionally, the exchange of water across the estuary from the action of the turbines is likely to affect the existing planned cooling water discharge plume from the power station.

Modelling of the tidal movement of the Hinkley C hot water plume has shown that it would travel quite a distance up and down the estuary while the excess temperature dissipates by mixing with cooler water and through loss to the atmosphere, and the temperatures involved.

An interaction with discharges from the lagoon's turbines is a significant possibility.

The changing temperature, of course, affects the fauna and flora that it encounters, both in the water column and on and in the seabed.

This effect was extensively considered by the planning regulators for the power station's environmental impact statement, especially regarding the outfall location, before acceptance.

The same level of research, advice, and analysis would be necessary for consideration of potential interaction between the lagoon and the outfall plume; much of it can be explored by mathematical modelling.

However, there is a difficulty at the moment in defining the baseline situation for comparisons because there are no results yet of the actual plume movement and its influence to base future predictions upon.

When one considers the cost and the timetables involved in consideration of the Severn Barrage, Hinkley C, Swansea Bay, and the many other past proposals, it looks like a difficult road ahead for a West Somerset Lagoon.

Dr Keith Dyer