SOMERSET residents may see a rise in their water bills to allow new homes to be built over the border in Dorset, according to a local councillor.

Both Somerset and Dorset have seen thousands of new homes held up by the phosphates crisis, with both local authorities having to agree additional mitigation with developers to prevent damage to wetlands protected by international law.

Both the Somerset Levels and Moors and the Poole Harbour area were identified by Natural England in August 2020 as ‘special catchment areas’, where additional mitigation would be needed to prevent any increase in phosphates.

As part of recent central government legislation, Wessex Water has committed to upgrading a significant number of its waste water treatment plants, reducing the amount of phosphates flowing into the protected areas and thereby allowing more new homes to be built.

But councillor Henry Hobhouse has revealed that more waste plants in Dorset will be upgraded than in Somerset – and Somerset taxpayers may be footing the bill for this.

Under the Levelling Up and Regeneration Act 2023, water companies were commanded to upgrade their waste water treatment plants to remove larger quantities of phosphates than was originally permitted.

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 also entered into an agreement with the council to implement “stretch permits” at its Langport, Taunton and Wells site which will see additional phosphates removed on top of the LURA requirements.

However, in Dorset, Wessex Water has committed to upgrading all waste plants which serve 1,000 people or more – allowing larger quantities of phosphate to be taken out of the Poole Harbour catchment.

Mr Hobhouse (who represents Castle Cary and the neighbouring villages) made this claim at a meeting of Somerset Council’s strategic planning committee in Taunton on Monday morning (September 16).

He said: “The history of this lies in work between Natural England and Dorset Council’s economic development team.

“They have taken 1.5 tonnes [of phosphates] out of the Poole Harbour catchment, by lowering the figures from Wessex Water – instead of sewage farms that serve 2,000 people or more, it’s gone down to farms that serve 1,000 people of more.

“The consequences if we took this to Somerset are incredibly expensive.

“Wessex Water has also been told that they are going to be allowed to charge Somerset residents for the removal of phosphates from the small sewage farms to create the benefit to Poole Harbour. I want that fact acknowledged.”

Mr Hobhouse asserted at the same meeting that Wessex Water’s planned upgrades to treatment plans across Somerset would remove more than enough phosphates to unlock all the remaining delayed homes – rendering other forms of mitigation (such as phosphate credits) redundant.

The Poole Harbour catchment area includes the River Frome (which flows through Dorchester and Wareham), its tributaries and other smaller rivers within the Dorset national landscape (formerly area of outstanding natural beauty, or AONB).

Most of the catchment lies within the Dorset Council area, with a small area lying under the remit of Bournemouth, Christchurch and Poole Council.

Around 3,500 homes in Dorset have been delayed by the phosphates issue – far fewer than the 18,000 Somerset homes which were originally caught up in the Dutch N ruling, or the 12,000 which remain in limbo after Somerset Council’s mitigation efforts to date.

Kate Murdoch, the council’s service manager for planning policy and implementation, said that the approach being taken in Dorset was in accordance with the legal advice provided by Natural England in August 2020.

She said: “Poole Harbour was subject to a legal challenge back in 2015. As a result of the court order, the Environment Agency has done work to understand what measures would be required for the restoration of that special catchment area.

“Poole Harbour is affected by both phosphates and nitrates; Dorset Council and the developers still need to deliver nitrate mitigation.

“Dorset Council has been awarded money through the government’s nutrient mitigation fund – as have we – and they are delivering nitrate mitigation to help unlock development in that catchment.”

Dorset Council received £4.63m from the government’s nutrient mitigation fund to “aid the delivery of nitrogen mitigation within the Poole Harbour catchment”.

Like the £9.6m awarded to Somerset Council from the same fund in December 2023, this grant is intended to support nutrient credit schemes (which typically involve taking agricultural use out of active use) and to identify additional mitigation projects on top of work being carried out by Wessex Water.

Wessex Water said that decisions over bills were a matter for the regulator, but confirmed Mr Hobhouse’s assertion that their upgrades would help to remove far more phosphates than would be needed to unlock all the outstanding homes in Somerset.

A spokesman said: “Councillor Hobhouse is correct to assert that our treatment sites outperform their discharge permits, outweighing any additional phosphorus from new developments.

“How this is accounted for in planning decisions surrounding nutrient neutrality requirements is a matter of policy for the planning authority.

“Our upgrades to our treatment sites are intended to meet tighter discharge standards laid down by both environmental and economic regulators.

“Bills and how and where we invest to meet new environmental standards are also determined by the industry regulator Ofwat.”