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Nutrient Neutrality Assessment and Mitigation Strategy (NNAMS)

Following recent advice from Natural England a planning application could require a Habitats Regulations Assessment (HRA), due to recent CJEU Dutch Nitrogen case law.

This is the case where the application site falls within the water catchment area of the Somerset Levels and Moors Ramsar site, designated for its rare aquatic invertebrates. There is a significant issue with nutrients entering watercourses that flow through this designated site, which adversely changes environmental conditions for these species.

Many new housing schemes (including single dwellings), visitor accommodation/attractions and some other developments, are likely to result in an increase in phosphates contained within foul water discharge. As the designated site is in 'unfavourable' condition, any increase in nutrients (specifically Phosphates) is seen as significant.

For affected applications and development types, an HRA confirming no adverse effect on the integrity of the Ramsar site may be required before planning permission can be granted. Mitigation may also be required. In order to confirm the requirement for an HRA, and to provide any subsequent quantitative and qualitative data required to enable the Local Planning Authority to complete an Appropriate Assessment, a Nutrient Neutrality Assessment and Mitigation Statement is required to be submitted prior to a determination of approval being reached.  A checklist will also be required to be completed and submitted to confirm that all necessary information is provided.

Mendip District Council is of the view that, in order for us to make an initial assessment on the potential impact, if any, of the development on the Somerset Levels of Moors Ramsar Site, a Nutrient Neutrality Assessment and Mitigation Statement is considered necessary at validation stage. 

However, we do acknowledge that the provision of a detailed mitigation strategy, given that achievable mitigation options are currently limited, would be overly onerous for Applicants and Developers.  In light of this we are asking for details of high-level options instead.

It is strongly recommended that you employ an Environmental and/or Ecological Consultant to provide assistance in completing the phosphate budget calculation and to research and design any required mitigation strategy.

This advice should be read in conjunction with the Somerset Nutrient Information Request Sheet and Interim guidelines on small scale thresholds and nutrient neutrality principles for the Somerset Levels and Moors Ramsar catchment.  This later small-scale thresholds guidance document is relevant if you are proposing to use a septic tank or package treatment plant.   A comprehensive explanation of this issue, along with all relevant documents and advice, can be found here: https://www.mendip.gov.uk/phosphates

Due to the complexity of the phosphates issue, and in light of legal advice, the Local Planning Authority is of the view that Reserved matters, Variation/removal of conditions and Listed Building Consents applications are affected and therefore, for affected developments, an NNAMS is required.  Further explanation of this is provided below:

For Reserved Matters applications

Even where an HRA was undertaken at outline stage, the LPA is still required to consider, not least in light of NE's advice (Natural England advice to LPAs on nutrients in the Somerset Levels and Moors (mendip.gov.uk)), whether there has been a material change in circumstances, and therefore whether or not a further/updated assessment is required in relation to reserved matters.

Unfortunately, in most cases where an HRA was carried out at outline stage, it is unlikely to have specifically considered the impact of the development on the Somerset Levels and Moors Ramsar site, particularly in relation to phosphates. Therefore, in these cases, an HRA is almost certainly going to be required before planning permission can be granted. 

In light of this an NNAMS will be required although, as explained below, at validation stage we will only be expecting a high level options statement in respect of any potential mitigation measures.  A detailed mitigation scheme, on which the HRA would be based, would be requested during the application process for agreement before the application can be found acceptable.

For Variation or Removal of Condition applications

With regard to s.73 applications the Habitats Regulations deal with the proposal which is at hand, not an alternative proposal which might already have permission but which has not been implemented, or is not in operation. Therefore, the LPA may not take into account any purported 'fallback' position in terms of s.73 applications or where an extant permission exists for a similar development to that proposed.

In most cases, this will mean that planning permission cannot be granted until the HRA has concluded that there is no likely significant effect.

Notwithstanding this, Mendip District Council have taken the view that if a planning permission has been previously implemented and the development is lawfully taking place on site and the amended proposal does not increase the number of dwellings or amend foul drainage details, then a new s.73 permission can be issued as it can be concluded that there would be no increase in impact above that already permitted. Therefore, whilst each application will be reviewed individually and assessed on its own merits, a NNAMS will be required at validation stage to demonstrate this although, as explained below, it is expected that the mitigation part of the report would conclude that no mitigation is required.

For developments where the planning permission has not previously been implemented and the development has not lawfully commenced on site, then an NNAMS will be required.

For Listed Building Consent applications:

Under Regulation 9(3) of The Conservation of Habitats and Species Regulations 2017, in exercising any of its functions, a competent authority must have regard to the requirements of the Directives so far as they may be affected by the exercise of those functions.  In light of this we are of the view that, for affected development types, an NNAMS will be required.

What should a Nutrient Neutrality and Mitigation Statement include:

For developments that are nutrient neutral and where no mitigation is required:

If you have evidence, or if the Phosphate Budget Calculator results in a zero or minus nutrient loading figure i.e. nutrient neutrality, then the need for mitigation is negated. An NNAMS is therefore required to include:

  • The input and output figures from the completed Phosphate budget calculator, referencing the steps and stages outlined within the Stodmarsh Guidance and appending the phosphate calculator figures to demonstrate nutrient neutrality.
  • For Variation or Removal of Condition applications where a lawful development has already commenced, information evidence to demonstrate that this is the case will be required.
  • In terms of mitigation, the NNAMS should simply state that none is required.

It should be noted that if the development is 'like for like' ie redevelopment of a site to demolish one dwelling in order to construct another, this is considered to be nutrient neutral.

For developments where mitigation is required:

An NNAMS is therefore required to include:

  • The input and output figures from the completed Phosphate budget calculator, referencing the steps and stages outlined within the Stodmarsh Guidance and appending the phosphate calculator figures.
  • A high level list of the potential options for mitigation is considered essential for major developments.  For minor developments it is not considered essential but any information that can be provided would assist the Council in understanding the potential options at a very early stage of the application process. 

If a detailed mitigation strategy is available then we would welcome its inclusion into the NNAMS, particularly if the proposed development falls to be considered under small scale thresholds guidelines (Icon for pdf Interim guidelines on small scale thresholds and nutrient neutrality principles - webpage 25.2.21 [148.81KB]) and where a package treatment plant solution is proposed, a detailed scheme to meet the guidelines would be appreciated. 

Otherwise, in terms of mitigation it would be useful if the following could be explained:

  • Are you including any design features within the development that could count as mitigation for example; water efficiency standard of 110L per person per day for new residential development, a comprehensive SuDS scheme etc?
  • Is there space on site for on-site mitigation?
    • If so, in general, what type of mitigation s are you considering?
    • If not are you looking to develop your own off site mitigation?
  • If on site mitigation is not possible:
    • Are you intending to seek mitigation through a nutrient credit scheme if/when one becomes available? Or
    • Are you intending to seek mitigation through a strategic solution coming forward through the Somerset Phosphate Strategy?

For information, for applications wishing to create constructed wetlands as mitigation, these will need to be designed by a specialist, registered with the Constructed Wetlands Association Home - CWA (Constructed Wetland Association), and we strongly recommend that the proposed wetland is submitted for consideration through the Natural England Discretionary Advice Service, the details of which can be found here: Developers: get environmental advice on your planning proposals - GOV.UK (www.gov.uk), prior to its submission to the Local Planning Authority.

Further details on the above information can be found here:  Somerset Nutrient Information Request Sheet_V2 (mendip.gov.uk)

Further details on small scale thresholds can be found here:  Icon for pdf Interim guidelines on small scale thresholds and nutrient neutrality principles - webpage 25.2.21 [148.81KB]

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