Our response to desalination plans

Desalination is the process of removing salt and other impurities from seawater to produce fresh water that is suitable for human consumption. Desalination is typically achieved in one of two ways:

(i) by heating seawater to separate the salts, or;

(ii) by passing seawater through membranes to separate the salts.

Both approaches are necessarily energy intensive and produce hypersaline brine as a waste product.

South West Water are currently proposing a two-phase development.  

Phase one: This will involve construction of seawater abstraction infrastructure and a desalination plant at Par docks, a freshwater holding and treatment lagoon, an underground pipeline between Par and Restormel Water Treatment Works, and above ground pipelines between Par docks and Par Waste Water Treatment Works. Phase one is relatively small in scale and will only run at capacity during periods of water scarcity.  

Importantly, phase one will combine desalination brine with treated wastewater (treated in line with permits issued by the Environment Agency), meaning that the discharge into the bay will not be hypersaline (i.e. not saltier than seawater). As such, Cornwall Wildlife Trust’s concerns regarding phase one relate mainly to the ecological impacts of construction.  

Phase two: The specifics of phase two are currently less clear. We anticipate that it will be significantly larger in terms of volume of seawater processed, require the construction of a dedicated discharge pipeline in the bay and discharge hypersaline water (more salty than seawater) into the bay.  

Cornwall Wildlife Trust would be especially concerned about the potential impacts of hypersaline discharge on the bay’s ecosystem. We already know that hypersaline water negatively impacts the growth and survival of seagrasses, and there are many documented impacts of brine on other species. For maerl, the impacts are entirely unknown. 

In June 2024 we sent a holding objection to the Marine Management Organisation (responsible for marine licencing) following South West Water’s application to conduct investigative drilling in the bay. Our objection was due to insufficient evidence being used for boreholes in areas containing seagrass, and the potential secondary impacts associated with drilling work. We will continue to review our position as new information becomes available. 

Our intention is to engage constructively and openly with all stakeholders involved in this complex, multi-phase proposal. Cornwall Wildlife Trust is committed to evidence-based decision making throughout and, should the evidence suggest negative impacts are likely for specific aspects of the proposal, we will take action accordingly. 

Cornwall Wildlife Trust is deeply committed to protecting nature in St Austell Bay.

We: 

1. Work with citizen science groups and organisations to collect data on marine wildlife and habitats, much of which now underpins what we know about the Bay. 

2. Campaign and advocate locally and nationally for bigger, better, and more joined up marine protected areas. 

3. Work with local communities to increase awareness of the bay’s importance, the threats facing its marine wildlife, and the actions we can take to protect it. 

4. Through the Cornwall and Isles of Scilly Coastal Partnership, work collaboratively with the council, businesses, regulators, fishers, and other conservation organisations to protect our marine ecosystems. 

We have worked with South West Water on their Upstream Thinking initiative in other parts of Cornwall for many years. South West Water covers the costs of us working in several drinking water catchment areas to reduce agricultural pollution, encourage regenerative farming and enhance and restore habitats.  

Our experience suggests we can secure the best outcomes for nature by engaging constructively with organisations outside the conservation sector, using our expertise and knowledge to positively influence policies and practices. Nevertheless, with any corporate partner, we always reserve the right to object to their activities if we feel they are in conflict with our aims. 

There will be risks to species and habitats on land with the proposed construction of a new pipeline. If sensitive habitats are avoided by careful route planning and advanced construction methods (for example drilling under Cornish hedges rather than removing sections) then the most significant impacts may be avoided. The terrestrial impacts are likely to be associated with construction rather than any on-going operation and there is established best practice for how to reduce these impacts. The detailed plans will need to be scrutinised, but we feel the risks to terrestrial habitats are lower than the risks to marine habitats.  

Tor to Shore is a multi-faceted project focussed on enhancing wildlife and engaging people on our largest nature reserve, at Helman Tor, and with communities around St Austell Bay, as well as working in partnership with farmers on the land in between. With our overall aim of enhancing wildlife locally, the impact of the proposed desalinisation plant is relevant, particularly the potential impacts on important marine habitats.  

We have learnt much more about the extent of the marine habitats whilst preparing the project bid over several years, so we are better equipped to challenge proposals that we feel fall short. Our strong connections with local community groups in the area also keeps us well informed. If desalination plans do progress during the lifetime of the Tor to Shore project, we feel that our evidence-based approach and our strong community links will help us to make sure that harm to important habitats is avoided and opportunities for enhancement are maximised.