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Phosphorus and nitrogen mitigation

Nutrient pollution is a big environmental issue for many of our most important places for nature in England. In rivers and estuaries, increased levels of nutrients (especially nitrogen and phosphorus) can harm wildlife. These nutrients are affecting the condition of internationally protected rivers, such as the Hampshire Avon, the River Lambourn, the Somerset Levels and Moors, and coastal waters such as the lower reaches of the River Test and the wider Solent and Southampton Water.

Nutrient neutrality is a concept promoted by Natural England as a means of ensuring that development does not add to existing nutrient burdens. This provides certainty that the whole of the scheme is deliverable in line with legislation (Conservation of Habitats and Species Regulations 2017 (legislation.gov.uk) (opens new window)).
 
Nutrient neutrality involves the calculation of a nutrient burden from a development. If there is an increase, mitigation through land use change or wetlands is needed to remove nutrients and counterbalance the output from development. Mitigation can be delivered by the developer or through strategic mitigation schemes. For Wiltshire, nutrient neutrality is needed in four catchment areas - the Hampshire Avon, River Test and the River Lambourn and the Somerset Levels and Moors.

Any proposal for a net addition of overnight accommodation is affected. This includes housing, retirement homes, care home, overnight tourism (B&B, hotel, camping, glamping). It does not generally apply to householder applications such as extensions as the NE nutrient budget calculator uses an average occupancy figure of 2.4 people per dwelling.

Other applications will be considered on their individual merits, for example certain industrial facilities, such as breweries, high water use developments (e.g. car washing centres), tourism attractions or regional transport hubs. Applications for the intensification of agricultural uses including new fish farms and watercress beds are also included, and these will require bespoke nutrient assessments.

Check if your proposal site is within one of the relevant river catchments using the interactive planning map (arcgis.com) (opens new window).

If your site falls within one of the catchments, read the relevant guidance below.

Natural England released water quality and nutrient neutrality advice to councils and a generic methodology in March 2022.

Natural England water quality and nutrient neutrality advice to councils (PDF, 499 KB)(opens new window)

Natural England: Nutrient Neutrality Generic Methodology (opens new window)

Site-specific guidance

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