Nitrogen Mitigation

The approach is required for all development with overnight accommodation, including all residential / hotel (all C class) uses and large HMOs.

The Council’s approach includes an occupancy rate calculator which takes into account the effect of smaller and larger dwellings (smaller dwellings needing less mitigation).

The nitrogen budget calculation should be undertaken as follows:

  1. Where the dwelling size (number of bedrooms) is specified in the planning application, complete the Council’s occupancy rate calculator and input the results into Natural England’s latest Solent Nutrient Budget Calculator
  2. For outline applications where the number and size of dwellings are not yet known, base the calculation on the maximum number of dwellings and then either:
    • Just complete Natural England’s latest Solent Nutrient Budget Calculator (which is based on an average dwelling size), or
    • Clearly demonstrate the likely mix of dwelling sizes (based on a precautionary approach, i.e. do not overestimate the number of smaller dwellings) and then follow the approach in 1
    • The calculation will be further refined at the reserved matters stage when the dwelling sizes are formally specified in the application

Where the outcome of the nitrogen budget calculation, in Stage 4 of Natural England’s Budget Calculator, results in a nitrogen load to mitigate, applicants will advise which mitigation scheme they will use, to enable the Council to consider whether this meets the requirements for mitigation as set out in its Position Statement. For example, Eastleigh’s mitigation schemes meet these requirements, where they are located within the Itchen catchment.

The provision of the information above is required to validate the planning application, and will enable the Council to undertake the necessary Habitat Regulations Assessment (for outline, full and reserved matters applications).

Further information:

Please note, for mitigation schemes to count in Southampton, they must be located in the Test, Itchen or Bartley river catchments and meet the other tests in the Position Statement.