A CHANGE in legal advice surrounding phosphate mitigation for housing development could unlock thousands of new homes across Somerset in the next few years.

About 12,000 homes across the county are being held up following a court ruling and resulting Natural England legal advice that developers had to provide additional mitigation to prevent any net increase in phosphates reaching the Somerset Levels and Moors protected nature reserves.

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 Government grant.

But the problems may soon be consigned to history after lawyers concluded the homes could be approved simply by allowing Wessex Water to complete upgrades to its large waste water treatment plants 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 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, such as the Somerset Levels.

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 bordering the county.

In addition to the Somerset Levels and Moors, which includes the catchments of the Rivers Tone, Parrett, and Brue, the county’s’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 court 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’, which the council is 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 as urgently.

The 11,600 homes in these two categories, roughly equivalent to the population of Minehead, are spread across the levels and moors catchment area, with the former Taunton Deane and South Somerset areas 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, including 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, covering Bruton, Castle Cary, Glastonbury, and Highbridge, 715 dwellings are being held up.

What has been tried so far?

To date, phosphate mitigation has taken a number of forms at specific sites, including:

The average phosphate credit costs about £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 £9.6 million in Government grants in December, 2023, to fund several projects designed to deliver further mitigation.

Three of these projects are being taken forward:

One trialled piece of technology, put forward by Salinity Solutions, has proven somewhat successful but is not being taken forward, despite £108,500 of the Government grant having been spent on it.

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.

The 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 has been carrying out monitoring of the water quality on the Levels and Moors with his latest findings suggesting Wessex Water’s work was starting to bear fruit.

Dr Clegg 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.

“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 the improvement we report will continue, but slowly.”

Dr Clegg said Wessex Water’s improvements would not unilaterally solve the phosphate issue within the River Parrett catchment, partly because large quantities of phosphate were tied up in river sediment which can only be removed through dredging or other physical extraction.

What does the new legal advice say?

Somerset Cllr 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 specialist environmental law barristers at London firm Landmark Chambers.

Cllr Hobhouse calculated about 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.

He said Wessex Water 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 upheld those figures, ruling that Wessex Water ‘over-engineered’ its upgrades to create significant headroom, or, 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 more than half the total population of Somerset.

The opinion concluded that the council could use this headroom as mitigation for housing development, meaning 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.

Landmark Chambers said: “Should the council establish with Wessex Water that at least four tonnes per annum of the phosphate stripping 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, arguing it would make a huge difference to both Somerset’s housing crisis and other affected parts of the UK.

Development portfolio holder Cllr Mike Rigby said: “I am 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 quickly and allows us to take a new approach to nutrient neutrality.”

Cllr Hobhouse said he was confident Wessex Water would issue agreement with the legal opinion in writing in the coming weeks.

He said: “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.”

Cllr Gwil Wren, whose Upper Tone division includes Wiveliscombe, said 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 does not fix the problem regarding the deterioration of the moors.”

Cllr Norman Cavill said the ruling would be a huge receive to many small developers whose livelihoods had taken a hit since the court ruling.

He said: “The phosphates problem has crucified many businesses across the Taunton Deane area in particular.

“A solution cannot 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?

Council executive director Chris Hall said the legal opinion would need further analysis before he could comment in detail on its implications.

He said: “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.”

Council planning service manager Kate Murdoch said Dr Clegg’s monitoring work would also inform the 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 feed back with their response.”

Council officers will now analyse the legal opinion and use it as the basis for a new policy on phosphate mitigation, which is expected to be put to councillors in September.