Complexities of nutrient neutrality, learnings from Somerset Council

On a recent visit to Somerset Council, the local team shared a key challenge from recent years: Nutrient Neutrality.

Somerset Council were one of the first Local Planning Authorities to receive a notification from Natural England about phosphate pollution in their area, and this article details the steps they took in response. Nutrient pollution and nutrient neutrality requirements are having widespread effects on development in England, impacting both the public and private sectors.

At a time when house-building is at the top of the agenda, we explore the Somerset Council team's innovative work to upskill their team and the wider development industry in the face of this complex and evolving challenge.

Nutrient pollution is a critical ongoing environmental issue for many natural habitats and protected sites. Disrupted nutrient levels affect the plants and animals that rely on freshwater habitats for survival. An increase in nutrients, especially nitrates and phosphorus, damages the quality of the water, reducing its oxygen-carrying capacity and speeding up the growth of certain plants (1). This creates water conditions that are unfavourable and harmful to those living in these precious habitats.

The sources of excess nutrients are very site-specific but include sewage treatment works, septic tanks, livestock, arable farming and industrial processes (2). The issue of nutrient pollution is affecting the ability of some local planning authorities to increase housing, as they cannot approve projects unless they are sufficiently certain it won’t negatively impact or increase pollution on the site. According to the Department for Environment, Food and Rural Affairs, the issue of nutrient pollution is currently impacting housing delivery across 74 local planning authorities (3).

Housing development, lifestyles, and water quality are all interconnected, and the increase in nutrients entering our water is an urgent problem.

Nutrient neutrality is an interim solution to support local planning authorities to approve developments. It doesn’t, however, replace the need to tackle water pollution at the source or restore protected sites. Natural England describes nutrient neutrality as a means of ensuring that a development plan does not add to existing nutrient burdens within catchments (4). The ambition is for no increase in nutrients as a result of a development or project, and it’s a requirement for new housing development in certain areas with protected habitat sites.

Developers can show that pollution can be mitigated through nutrient neutrality, using a range of methods, including creating new wetlands or buffer zones along rivers. This can help mitigate the increase of nutrients in our waterways as a result of new housing and population growth.

Somerset is a rural county in the heart of South West England. The county is home to many Outstanding Areas of Natural Beauty, including parks, hills, coastline, and internationally important wetlands. According to the Joint Nature Conservation Committee, the Somerset Levels and Moors is one of the largest and richest areas of traditionally managed wet grassland and fen habitats in lowland UK (5).

In August 2020, Natural England notified the former Somerset Councils that the phosphate levels at the Somerset Levels and Moors Ramsar site were too high.

This meant an extensive geographical area was being affected by nutrient pollution. Somerset was one of the first councils in England to be notified about phosphate pollution, and at the time, there was very little guidance available to support them in navigating this issue.

At the time, Somerset Council was still various district and county councils, so the policy team started by setting up a project team to first examine the hydrological links and the geographical extent of the areas affected.

One of the first steps they took was to automate the calculator for phosphate loading from new development.

Somerset was one of the first councils to automate this process, saving officers from carrying out this lengthy calculation manually. The calculator reviews land use and current phosphate loading, allowing officers to input proposed land uses and see which types will affect the overall loading whilst articulating how many tons of phosphate per annum they need to remove or mitigate against.

This work was followed by the publication of their Solutions Report. Part of the complexity of nutrient neutrality is the constant movement of water, the interconnection of different rivers, and the fact that the response to this movement changes throughout the year. In the winter, water is moved around to manage flooding, whereas in the summer, it’s moved for ecological reasons to prevent drying. Hundreds of structures are involved in regulating water movement.

The resulting report details river catchment areas in Somerset and can be used by developers, to support them in exploring different phosphate mitigation options for new development. The Somerset Levels and Moors catchment area is connected to three rivers, and developers must ensure that their phosphate offsetting efforts benefit the affected river.

This report marked the start of Somerset Council's response to nutrient pollution and provided guidance for nutrient mitigation. Due to the lack of guidance at the time, some members of the Somerset team had to become experts in nutrient neutrality swiftly. Following this, their focus moved to upskilling the various teams and ensuring that they understood how nutrient neutrality would affect their work.

It wasn’t only Development Managers who needed to learn more about this topic quickly. It was also crucial for members, agents and developers to better understand the impacts of nutrient pollution and mitigation. The team created user videos and held training sessions, events and forums to upskill wider colleagues. Every piece of guidance they’ve produced has been published on their website, which supports the development industry and other Local Planning Authorities facing similar issues.

Somerset Council has now been awarded government capital grant funding, allowing them to implement an interim strategy. The funding allows them to move forward and deliver their own schemes, which would have been impossible without financial government support. Following the development of the nutrient loading calculator and mitigation guidance, their focus has been on facilitating the third-party credit market. Nutrient credits deliver a mitigation scheme, which could range from producing a wetland to water-saving measures or upgrading septic tanks. Credits are traded as a kilogram of phosphates that come with a set price.

Going back two years, a significant number of planning applications were caught due to phosphate issues. These were urban, brownfield development sites where they had very little opportunity to unlock their schemes through mitigation measures.

Members underwrote a programme of activities that resulted in the River Tone phosphate credits, a council-run scheme now in its third round of releasing credits.

This has meant the team now understands how to release third-party credits, allowing them to inform the market and stimulate others to enter the market as well. The team at Somerset Council responded swiftly to this highly complex issue. Up-skilling their team while creating new guidance and innovative tools, allowed them to unlock housing schemes at a time when new housing is so desperately needed. There is much the wider public sector and built environment community can learn from their approach and the technical resources they’ve produced.

1. ‘Nutrient pollution: reducing the impact on protected sites’, The Department for Environment, Food and Rural Affairs, June 2023
2. ‘Nutrient Neutrality and Nutrient Mitigation’, Natural England, February 2024
3. ‘Nutrient pollution: reducing the impact on protected sites’, The Department for Environment, Food and Rural Affairs, June 2023
4. ‘Nutrient Neutrality Principles (TIN186)’, Natural England, July 2023
5. ‘Phosphates in Somerset background information’, Somerset Council

• ‘Phosphates in Somerset background information’, Somerset Council
• ‘Phosphates – Guidance, Template Documents and Useful information’, Somerset Council
• ‘Legal advice on Phosphates on the Somerset Levels and Moors Ramsar Site’, Somerset Council
• “Nutrient Neutrality and the planning system”, Local Government Association