A development of 280 homes on Somerton Road in Street is finally moving forward after securing outline planning permission in January 2023. The project was unlocked after a nearby pig farm was taken out of commission, allowing the necessary phosphate mitigation measures to be put in place. However, Street is just one of many areas across Somerset affected by the ongoing phosphates crisis, which has left around 12,000 homes in limbo.

The Dutch N court ruling, issued in 2020, has delayed thousands of new homes in Somerset due to the need for developers to mitigate any net increase in phosphates entering protected areas, such as the Somerset Levels and Moors. Developers are now required to secure additional mitigation, which has stalled several housing projects.

Thousands of new properties across Somerset have been prevented from being delivered following the Dutch N court ruling and the resulting legal advice issued by Natural England in August 2020.

The ruling, in summary, requires developers to secure additional mitigation to prevent any net increase in phosphates within the catchments of internationally protected Ramsar sites, including the Somerset Levels and Moors.

Since the ruling, the council has been seeking to 'unlock' housing developments through various methods, including fallowing agricultural land, delivering new wetlands, and creating 'phosphate credits' systems to allow developers to contribute financially to mitigation.

Some of these initiatives have begun to bear fruit, with around 6,000 new homes being unlocked and numerous long-awaited applications being approved.

However, nearly 12,000 homes remain in limbo, and just over half will need to secure mitigation very quickly if they are to be delivered by 2032.

A detailed update on the phosphates crisis came before the council's strategic planning committee when it convened in Taunton on Monday morning (September 17).

The Somerset Levels and Moors catchment area includes three main rivers – the River Brue, the River Parrett and the River Tone.

Each individual river catchment originally had separate phosphate credit systems operating there, since the Natural England legal advice was issued before Somerset Council replaced the four district councils in April 2023.

The cost of phosphate credits varies greatly depending upon the availability of land which can be fallowed and whether the local waste water treatment plant will be upgraded under the Levelling Up and Regeneration Act 2023 (known as LURA).

In the Taunton area, for example, a developer would be expected to pay £37,500 to offset one kilogram of phosphates – which would be sufficient to unlock ten homes.

Councillor Sue Osborne said: "Do we know how much agricultural land has been taken out of commission to secure these phosphate mitigation measures?

"There's increasing concern about how much productive agricultural land could be lost, and food security is becoming a bigger issue."

Ms Osborne's Ilminster division will soon see construction begin on 360 new homes on Canal Way, with Persimmon Homes South West securing outline permission in January after agreeing to fallow substantial quantities of agricultural land to the south of the Herne Hill nature reserve.

Kate Murdoch, the council's service manager for planning policy and implementation, declined to give a precise figure but responsed: "Much of the land being provided for mitigation is regularly waterlogged. This offers an alternative income stream for landowners."

Of the 18,000 homes which were originally delayed by the Dutch N ruling, 4,660 have been successfully unlocked to date, predominantly through the phosphate credit schemes being run by both the council and third parties.

This includes a development of 280 homes on the B3151 Somerton Road in Street, with outline planning permission being granted in January 2023 after a nearby pig farm was taken out of commission.

An additional 1,500 homes have secured approval with mitigation in place but are awaiting the sign-off of legal agreements between the council and developers (known as a Section 106 agreement).

Of these, two-thirds are within the River Parrett catchment, which includes the majority of the former South Somerset district – an area in which more than 50 sizeable developments have been held up to varying degrees since the Dutch N ruling.

This leaves around 6,300 planned homes where some form of phosphate mitigation will be needed – including the planned development of around 620 homes on the A371 Cannard's Grave Road in Shepton Mallet.

A further 5,500 homes are expected to require mitigation in future years, but these are not expected to begin delivery until 2032 and are therefore considered a lower priority for planning officers and phosphate credit providers.

The council secured £9.6m of central government funding in December 2023 to fund half a dozen measures designed to unlock additional housing. These comprise:

• A water filtration technology pilot, using reverse osmosis technology from Salinity Solutions to filter out water-borne phosphates (£2m)
• Identifying new nature-based solutions (such as wetlands) where biodiversity net gain can also be delivered (£3.5m)
• Retrofitting social housing, including the removal and replacement of septic tanks in older properties (£1m)
• Creating nature-based solutions on council-owned land, including the creation of new nature reserves on existing green spaces (£2m)
• Growing miscanthus grass on fallowed land to generate additional phosphate credits (£640,000)
• Researching and developing new technical innovations which could be scaled up in the near future (£400,000)

Ms Murdoch said in her written report: "Currently, there are approximately 370 applications in the planning pipeline, involving around 6,300 dwellings awaiting a phosphate solution.

"With mitigation measures and credit schemes in place, together with the proposed measures being funded through the nutrient mitigation fund, means that all these homes are anticipated to be unlocked."

Wessex Water has committed to upgrading all of its wastewater treatment plants which serve a population of 2,000 people or more, ensuring that fewer phosphates are released into the Somerset Levels and Moors catchment area and therefore less land will need to be fallowed or offset to generate phosphate credits.

Under LURA, Wessex Water must bring the following treatment plants up to the higher standard by May 2031:

• Bishop's Lydeard
• Bruton
• Butleigh
• Castle Cary
• Chard
• Crewkerne East
• East Coker
• Evercreech
• Glastonbury
• Ilchester
• Ilminster
• Langport
• Martock
• Merriott
• Milborne Port
• Shepton Mallet
• Sherborne
• Somerton
• South Petherton
• Taunton
• Thornford
• Wellington
• Wells
• Yeovil (Pen Mill site)

However, Wessex Water has committed to completing these upgrades by April 1, 2030 – and has agreed with the council to implement "stretch permits" at its Langport, Taunton and Wells sites, which will remove additional phosphates.

Ms Murdoch added in her report: "For the period up to 2030, this will further reduce the requirement for temporary phosphate credits for developments feeding into these wastewater treatment plants.

"These upgrades will significantly reduce nutrient loads from these plants in designated catchments, while also reducing the average costs of nutrient mitigation for developers."

Further upgrades on phosphate credits and related mitigation are expected to come back before the committee by March 2025.