Nutrient Neutrality in the River Avon catchment

The River Avon SAC (special area of conservation) runs through several different administrative areas. The catchment area for this habitat site overlaps part of Dorset Council area. Wiltshire Council act as the lead authority on planning issues relating to nutrient pollution of the River Avon. We have been working closely with Wiltshire Council on these issues to ensure that there is effective joint working across our boundaries.

On 25 January 2024, the Secretary of State designated the River Avon as a nutrient sensitive catchment for phosphorus.

Mitigation and the Local Nutrient Mitigation Fund

Wiltshire Council has been awarded £9.8m of grant funding to aid the delivery of nutrient mitigation within the River Avon catchment. This grant enables mitigation projects to be identified and delivered, and for mitigation credits to be sold. Third-party mitigation providers are also beginning to deliver measures in the catchment of the River Avon.

Within this catchment developers will take responsibility for securing nutrient mitigation for their development proposal. Mitigation can be secured:

• on-site or through land in the ownership of the developer
• through an agreement with an accredited third-party mitigation provider
• through a Wiltshire Council nutrient mitigation scheme

In all instances, the mitigation will need to be secured in perpetuity through the necessary legal agreements or planning condition.

Decision making in the River Avon catchment

Within the River Avon catchment, there is a need for qualifying developments to demonstrate neutrality for phosphorus. Qualifying development 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.

The boundary of the River Avon catchment is defined within the catchment map. Within this area, it is presumed that wastewater and surface water arising from qualifying development is likely to increase phosphorous levels within the River Avon. Where an applicant considers that either wastewater or surface water from their development will not discharge into River Avon they must submit details with their planning application.

The latest River Avon nutrient budget calculator (May 2024) should be used to assess the development’s nutrient budget. Applicants will need to demonstrate that appropriate mitigation measures have been secured to offset the phosphorous arising from qualifying development.

A nutrient neutrality statement must be submitted with any planning application for qualifying development in the River Avon catchment which is also in Dorset Council area. There are further details on the statement in our local list requirements, but it should include:

• an assessment of whether the proposed development is also ‘qualifying development’
• details of arrangements for managing wastewater and surface water arising from the development
• a nutrient budget calculation for both phosphorous made using the Natural England nutrient calculator for the River Avon
• details (including how this mitigation will be delivered and secured in perpetuity) of the mitigation proposed to offset nutrient loading

We have produced a guidance note to assist applicants where they propose to upgrade an existing septic tank or package treatment plant to provide mitigation measures, or where they propose to connect a development to a new package treatment plant. Where relevant, applicants may wish to refer to this note when preparing their planning application.