Thousands of homes could be unlocked after change in phosphates legal advice
Around 12,000 homes across Somerset are being held up following the Dutch N court ruling
Thousands of homes across Somerset could be unlocked in the next few years following a change in the legal advice surrounding phosphate mitigation.
Around 12,000 homes across Somerset are being held up following the Dutch N court ruling and the resulting Natural England legal advice, with developers having to provide additional mitigation to prevent any net increase in phosphates on the Somerset Levels and Moors.
Somerset Council has been attempting to alleviate the problem on several fronts, negotiating mitigation with developers on individual sites (often through fallowing agricultural land) and trialling several long-term solutions paid for through a central government grant.
But these problems may soon be consigned to history after lawyers concluded that these homes could be approved simply by allowing Wessex Water to complete all of the upgrades to its large waste water treatment plans by 2030.
Here’s everything you need to know:
What is the phosphates crisis?
Phosphates can enter rivers and other watercourses through a number of methods, ranging from fertiliser and animal waste being washed off farmland to human sewage.
Large quantities of phosphates in rivers and lakes can cause eutrophication and large algae blooms, which can deprive plants and animals living in these habitats of oxygen.
The Dutch N court ruling outlaws any developments which increase either phosphate or nitrate levels within Ramsar sites – that is, wetlands or other low-lying areas which are protected under international law.
The resulting legal advice from Natural England, which was published in August 2020, identified 16 “sensitive catchment areas” across the UK where this ruling would apply – including three either in Somerset or on its border.
In addition to the Somerset Levels and Moors (which includes the catchments of the River Brue, the River Parrett and the River Tone), Somerset’s rivers also flow into the River Axe catchment in east Devon and the Poole Harbour catchment in Dorset.
In order to build any form of new development – from houses and commercial units to agricultural barns – the developer and the local authorities would have to agree additional mitigation which would offset the phosphates generated from the development site.
How many homes are currently affected?
Of the 18,000 homes which were originally stopped in their tracks by the Dutch N ruling, 6,400 have managed to either secure planning permission with agreed phosphate mitigation, or have mitigation secured but are waiting a decision by councillors or officers.
A further 6,300 are currently “awaiting a phosphate solution”, with the council attempting to address through a variety of different approaches.
The remaining 5,300 homes comprise sites which are not expected to be delivered before 2032 and therefore mitigation is not being pursued so urgently.
The homes in these two categories (which amount to 11,600 homes, or roughly the population of Minehead as of the 2021 census) are spread out across the Levels and Moors catchment area, with the former Taunton Deane and South Somerset areas being especially affected.
In the River Tone catchment (which includes Taunton and Wellington), 5,233 dwellings are being held up, amounting to more than 100 individual sites.
In the River Parrett catchment (which includes Yeovil and Langport), 3,000 homes are currently awaiting a phosphate solution, with a further 1,000 having planning approval in place but waiting for the relevant legal agreements to be signed off.
In the River Brue catchment (which includes Bruton, Castle Cary, Glastonbury and Highbridge), 715 dwellings are being held up – including the planned C. G. Fry development on the A371 Cannard’s Grave Road in Shepton Mallet which will deliver 620 new homes.
What has been tried so far?
To date, phosphate mitigation has taken a number of forms at specific sites, including:
Creating new wetlands, which can filter out and absorb phosphates (such as at the Staplegrove urban extension in Taunton)
Fallowing agricultural land, taking it out of active production and potentially replacing it with woodland (such as the Canal Way development in Ilminster)
Upgrading waste water treatment plants, removing phosphates from sewage (such as at the Lowerside Lane site in Glastonbury)
Upgrading septic tanks with package treatment plants, which take more phosphates out before they leave a residential area (such as at the planned Nynehead Road development in Wellington)
Both Somerset Council and private companies have also created ‘phosphate credit’ schemes, whereby the developer will pay for off-site mitigation to offset the impact of new homes.
To date, this has often taken the form of farmland being taken out of active use – with the fallowing of Manor Farm in Prestleigh, near Shepton Mallet, generating enough credits to unlock up to 1,400 new homes within the River Brue catchment.
The average phosphate credit costs around £35,000 to remove one kilogram – though some third party providers are able to provide credits at closer to £30,000 per kilogram, and this is likely to fall further in the near-future.
On top of this, the council secured £9.6m in central government grants in December 2023 to fund several projects designed to deliver further mitigation.
Three of these projects are being taken forward – namely:
The creation of new wetlands on either council-owned land or private sites (at a projected cost of £5.6m)
The creation of ‘temporary’ or ‘bridging’ phosphate credits (which will provide mitigation up to 2030 without fallowing more land) by growing miscanthus grass and trialling new technology (£3.5m)
Upgrading sewage treatment plants near rural council houses in the former Taunton Deane area (£1m)
One trialled piece of technology, put forward by Salinity Solutions, has proved somewhat successful but is not being taken forward – with £108,500 of the government grant having been spent on this particular element.
What about the water companies?
Under the Levelling Up and Regeneration Act 2023 (known colloquially as LURA), water companies were ordered to upgrade their waste water treatment plants to remove larger quantities of phosphates than was originally permitted.
These upgrades must be implemented by May 2031 and must be applied to all waste water treatment plants which serve a population of 2,000 or more people.
Wessex Water has publicly committed to upgrading all the applicable Somerset plants by April 1, 2030, and has entered into an agreement with the council to implement “stretch permits” at its Langport, Taunton and Wells sites which will see additional phosphates removed on top of the LURA requirements.
Citizen scientist Dr Andrew Clegg, who lives in Martock, has been carrying out monitoring of the water quality on the Levels and Moors – with his latest findings suggesting that Wessex Water’s work had started to bear fruit.
In a statement read to the committee on his behalf, he said ” I have been measuring the phosphate flow in the Parrett catchment for three years.
“For the first time probably for decades, we observed a ‘good’ phosphate reading at Langport on March 10).
“This improvement follows the installation by Wessex Water, at the end of last year, of phosphate removal stages at five upstream sewage treatment plants.
“This programme was designed to remove around 70 tonnes from the river each year. We anticipate that the improvement we report will continue, but slowly.”
Dr Clegg said that Wessex Water’s improvements would not unilaterally solve the phosphate issue within the River Parrett catchment – in part because large quantities of phosphate are tied up in river sediment, which can only be removed through dredging or other physical extraction.
What does the new legal advice say?
Councillor Henry Hobhouse has been outspoken on the phosphates issue for several years, arguing that homes could be unlocked through Wessex Water’s upgrades rather than taking large swathes of productive land out of use.
Frustrated by a lack of progress, he jointly commissioned (with Somerset Council) a new legal opinion on the matter from London law firm Landmark Chambers – which was received shortly before the council’s strategic planning committee met in Taunton on Monday morning (March 17).
Mr Hobhouse had calculated that around three to four tonnes of phosphates would need to be removed via Wessex Water’s treatment plants in order to unlock the entire housing backlog.
Wessex Water, he asserted, had already removed between 17.3 and 20.8 tonnes by the time the legal opinion was commissioned in late-2024 – rising to 70 tonnes in January 2025.
The legal opinion upholds these figures, ruling that Wessex Water is “over-engineered” its upgrades to create significant “headroom” – in other words, the capacity to remove massive additional phosphates which will be generated by future housing growth.
Startlingly, there is enough ‘headroom’ to cope with an additional 300,000 people – the equivalent of half the total population of Somerset.
The opinion concluded that the council could use this ‘headroom’ as mitigation for housing development – meaning that it did not have to spend time and money securing additional mitigation by fallowing land or creating wetlands.
This, in turn, will allow developers to contribute more funding towards local schools, medical facilities and other infrastructure, since they will not have to set aside large sums early on in a development to pay for phosphate mitigation.
The opinion stated: “Should the council establish with Wessex Water that at least four tonnes per annum of the phosphate stripping at treatment plants is
for mitigation of anticipated housing, the council may legitimately take that into account in an appropriate assessment for a planning application”.
How has the council responded?
Numerous councillors welcomed the new judgement warmly on Monday (March 17), arguing it would make a huge difference to both Somerset’s housing crisis and other affected parts of the UK.
Councillor Mike Rigby, portfolio holder for economic development, planning and assets, said: “I’m very pleased to finally see this opinion that where headroom exists at waste water treatment plants that headroom can be used to offset housing without additional mitigation.
“This advice moves us on very quickly and allows us to take a new approach to nutrient neutrality.”
Mr Hobhouse – whose Castle Cary division has seen significant housing growth in recent years – said he was confident Wessex Water would issue agreement with the legal opinion in writing in the coming weeks.
He added: “This is enough to mitigate 30,000 homes or thereabouts – far more than the 11,800 we have lined up.
“It means we will soon have a five-year housing land supply – meaning that we will not have 400 families living in bed-and-breakfast accommodation because we cannot house them.
“We still have habitat regulations, but we are changing the way we approach them.”
Councillor Gwilym Wren (whose Upper Tone division includes Wiveliscombe) said that a balance needed to be struck between delivering much-needed new homes and reversing the ecological decline of the Levels and Moors.
He said: “The council finds itself in a cleft stick – not only are we the local planning authority and have targets to meet, but we are also the appropriate authority for nutrient neutrality.
“If we use the headroom that the waste water treatment plant works have created, we can go forward – but it doesn’t fix the problem regarding the deterioration of the Moors”.
Councillor Norman Cavill (whose Monkton and North Curry division includes the Monkton Heathfield urban extension) said the ruling would be a huge receive to many small developers whose livelihoods had taken a hit since the Dutch N ruling.
He commented: “The phosphates problem has crucified many businesses across the Taunton Deane area in particular.
“A solution can’t come fast enough, and this has the potential to make a huge difference. This needs to be handled with a high degree of urgency.”
What happens next?
Chris Hall, the council’s executive director for community, place and economy, said that the legal opinion would need further analysis before he could comment in detail on its implications.
He told the committee: “The whole matter of nutrient neutrality is a complex one and we are working through the next steps. We are not able to comment further at this time.”
Kate Murdoch, the council’s service manager for planning policy and implementation, said that Dr Clegg’s monitoring work would also inform this new policy.
She said: “Natural England’s response to previous monitoring work was shared with the executive committee in June 2024.
“We will follow up to see whether this further evidence allows us to take a difference approach, and we will feedback with their response.”
Officers will now analyse the legal opinion and use it as the basis for a new policy on phosphate mitigation, which is expected to come back before the committee and the executive in September.
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