Nutrient pollution and Nutrient Neutrality in Dorset Council

Introduction to nutrient pollution and Nutrient Neutrality

Dorset is home to many areas that are internationally important for wildlife, including estuaries and freshwater habitats. Excess nutrient levels in protected estuaries and freshwater habitats increases algal growth leading to a loss of biodiversity.

In our area nutrient inputs into the hydrological catchments of these estuarine and freshwater habitat sites comes from two main sources, agriculture, and treated wastewater effluent from development. This pollution has left the habitats in an unfavourable condition and makes them extremely sensitive to further nutrient pollution.

We must consider the impact of new development on these habitats, and as part of this take account of their existing condition, when making planning decisions. In March 2022, Natural England advised us and other councils around the country, that development within the catchments of the protected habitat sites effected by nutrient pollution has the potential to worsen their condition. Natural England advocated an approach of Nutrient Neutrality where applicants use mitigation to offset the increase in nutrient load that would arise from their development. This approach ensures that further development will not worsen the condition of the protected habitat site.

The requirement for Nutrient Neutrality only applies where the increase in nutrient loading arising from the development is significant. This includes:

• any form of development that increases overnight stays within the catchment
• some commercial development that either attract large numbers of people into the catchment (such as a tourist attraction) or where there is a significant discharge into the catchment for example from an industrial process
• development which results in the intensification of agricultural practices, such as an additional cattle barn

Development that increases overnight stays in the catchment may comprise permanent residential development, gypsy and traveller development, care homes, nursing homes, tourist accommodation including both permanent and temporary campsites and hotels. Collectively we refer to this as ‘qualifying’ development.

More detailed information about nutrient pollution and Nutrient Neutrality is available on our pages relating to nutrient pollution and the law.

Since the updated advice from Natural England was released, we have been working to help support nutrient neutrality in the effected catchments in our area to enable development to take place. The government have also put in place legislation and other measures to reduce the mitigation burden on development so that much-needed new homes can be delivered.

These measures include:

• requiring the upgrade of wastewater treatment works through the Water Industry Act 1991 (as amended through the Levelling Up and Regeneration Act 2023 - (Part 7 of the Act refers to the nutrient pollution standards and government has prepared an ‘Nutrient neutrality update’ following announcements on nutrient neutrality)
• providing funding for a Natural England led nutrient mitigation scheme to deliver nutrient mitigation in priority catchments (see government’s written ministerial statement and Natural England’s blog post on their nutrient mitigation scheme)
• the Local Nutrient Mitigation Fund to enable councils to deliver nutrient neutrality mitigation (government has published details of the outcomes of the first round of bids for the fund and of opportunities for a second round of bidding)

Wastewater treatment works upgrades

For those nutrient sensitive catchments designated on 25 January 2024, the Water Industry Act 1991 (through the Levelling Up and Regeneration Act 2023) places a duty on water companies to upgrade the performance of certain wastewater treatment works to achieve higher permitting requirements (known as a technically achievable limit) by 1 April 2030. Government has issued a notice listing nutrient sensitive catchments and maps showing the extent of these catchments. There are exemptions to the upgrading requirements in the Act which can be widened so that they apply to more wastewater treatment works or narrowed so that they apply to fewer wastewater treatment works. The Secretary of State announced the exemptions on 24 May 2024.

The new permitting requirements for wastewater treatment works are, in most cases, significantly lower than the current permit limits and therefore where they are applied the mitigation burden on development will be reduced in the longer term as nutrient concentrations in wastewater discharges are reduced. Despite this there is still likely to be a need to mitigate the impacts of the remaining nutrients in wastewater after the upgrades have been applied. The new permitting requirements and the application of the exemptions have some very specific implications for Poole Harbour catchment. Please refer to the pages relating to Poole Harbour for further explanation. All mitigation for nutrient neutrality needs to be secured in perpetuity (i.e. 80 years) through appropriate planning conditions or legal agreements depending on the circumstances.

Where development receives planning permission before the upgrade date for the new permitting, applicants and developers will need to consider temporary mitigation. The nutrient loading from development will be higher before new permitting takes effect and lower afterwards. This means that there will be a temporary period up to 2030 when the requirements for mitigation are higher. Temporary mitigation will be required to bridge the period from the date of the planning permissions granted before the upgrade date (1 April 2030). Where permission is granted after the upgrade date temporary mitigation will not be required. The amount of temporary mitigation needed will be calculated using the appropriate calculator for the catchment with the temporary mitigation being secured through the necessary legal arrangements or planning conditions depending on the circumstances.

Over-view for securing nutrient mitigation credits

Mitigating nutrient pollution is part of the process of seeking planning permission for any ‘qualifying development’ within the catchment area of a habitat site that is affected by nutrient pollution.

All applications for ‘qualifying’ development must be supported by a nutrient neutrality statement that sets out the nutrient loading from the proposed development and the approach to mitigating this additional nutrient loading. We have prepared separate guidance on the content of the nutrient neutrality statement as required by the Validation Checklist (we expect statements to be concise and focus on the nutrient budget calculations and proposed mitigation measures).

In the Dorset Council area developers now have the responsibility for to securing nutrient mitigation for their development proposal. Mitigation can be secured:

• through an agreement with Dorset Council when acting as a mitigation provider
• through an agreement with an accredited third-party mitigation provider
• on-site or through land in the ownership or control of the developer

(We have prepared separate guidance on applying for credits derived from our mitigation projects, as well as guidance for third parties wishing to develop and deliver their own mitigation to generate mitigation credits for sale or to mitigate impacts from a specific development).

Mitigation credits available from ‘certified’ mitigation schemes:

We have listed those ‘certified’ mitigation schemes below. These are schemes which either we, or Natural England, have delivered, or those delivered by third parties where there is an ‘overarching’ planning obligation between ourselves and the mitigation provider. (We will not enter ‘overarching’ planning obligations unless we are satisfied that the mitigation project is suitable and effective, which must be verified through discretionary advice provided by Natural England). 

Dorset Council acts, and takes decisions, impartially, fairly and on merit, using the best evidence and without discrimination or bias. The list of providers is not exhaustive or closed (we keep the list under review and update it where necessary), and individuals must take their own decisions on where to source nutrient mitigation credits.

Poole Harbour catchment:

• Natural England mitigation scheme 

Somerset Levels and Moors catchment:

• currently no accredited mitigation schemes (Somerset Council has prepared a table of potential phosphorus mitigation schemes in the River Parrett catchment which overlaps the northern part of Dorset Council area – planning obligations or other agreements are required to ‘certify’ these mitigation providers) 

River Avon catchment:

• third party accredited mitigation scheme at Bicton Fish Farm (Pennyfarthing homes - benarnold@pennyfarthinghomes.co.uk)

River Axe catchment:

• currently no accredited mitigation schemes

Chesil and The Fleet catchment:

• currently no accredited mitigation schemes