Nutrient Neutrality Assessments

All developments within certain designated areas require a Nutrient Neutrality Assessment and Mitigation Strategy (NNAMS).  Many LPAs also now require an applicant to provide a Shadow Habitats Regulations Assessment (sHRA) to determine a planning application.

A Nutrient Neutality Assessment and Mitigation Strategy (NNAMS) is the report that demonstrates how your development meets the requirements for nutrient neutrality.

WCI has produced many NNAMS reports for a wide range of developments across many Local Planning Authorities including Somerset West & Taunton Council, South Somerset District Council, Mendip District Council, East Devon District Council, Cornwall Council, Dorset Council, Sedgemoor District Council, Wiltshire Council, Exmoor National Park Authority, and others.  We have a strong working relationship with Natural England and the LPAs and have achieved notable successes in defining nutrient neutrality strategies that have gained Natural England and Planning Authority approval.

Our reports provide developers with clear guidance on the scale of the phosphates generated from the proposed development, options for mitigating these phosphates and probable costs.  We complement all agreed phosphate strategies with a ‘Shadow Habitats Regulations Assessment (sHRA) to speed up the process of achieving Planning Approval.

Phosphate Balance

A phosphate balance is calculated on the basis of:

  • Phosphates arising due to changes in occupation
  • Phosphates arising due to changes in land use

Each of the two sources of phosphate must be calculated in accordance with the relevant guidance and methodologies.


Any NNAMS must start with establishing the foul drainage strategy for the development.  This determines what the sewage treatment method will be and subsequently how much the treatment will reduce phosphates.

The foul drainage strategy for the development remains subject to all the normal Planning Regulations, Building Regulations, Environmental Permitting Regulations and the Water Industry regulations.  Establishing a functional and compliant foul drainage strategy has never been easy and corners can’t be cut just because you need to achieve nutrient neutrality.


The way in which land is used can also result in nutrients reaching a watercourse.  Take, for example, the idea of land used for diary farming.  This land will receive nutrients, either through livestock defecation or through fertilisation, and some of this will be washed off into surrounding watercourses.  

Changing the nature of the land use then implies a change in the nutrient balance for that area of land.  It is this change in land use that defines the ‘land use’ phosphate balance for a proposed development.  

WCI are familar with all the various methodologies employed for the calculation of ‘Total Nitrogen’ (TP) and ‘Total Phosphorus’ (TP) including the Royal Haskoning method employed by many LPAs and the Ricardo method promoted by Natural England.

Once the ‘phosphate balance’ for a development has been established, it is likely that there will be a residual amount of ‘Total Phosphorus’ which must be offset elsewhere in order for the development to be deemed nutrient neutral.  Identifying how and where this offset is achieved is called the Mitigation Strategy.  Mitigation strategies can include ‘on-site’ (within the development boundary) or ‘off-site’ (on third party land) offsets.  Offsets can also be based on land use mitigation (changing land use to reduce phosphates) or occupation mitigation (improving on the phosphates discharged from a site through the foul drainage system).


WCI will provide you with honest, knowledgeable advice on how to achieve Nutrient Neutrality for your development.

Book a NNAMS today