The River Lambourn and Nutrient Neutrality

1. The River Lambourn SAC – introduction

The River Lambourn Special Area of Conservation (SAC) is a European Protected Site – a designated site of the very highest importance for biodiversity protected under the Conservation of Habitats and Species Regulations 2017 (the “Habitats Regulations”). Like other designated sites, it is a material consideration in planning under the Local Plan and, like other SACs, impacts on it must be assessed via a special process, Habitats Regulations Assessment (HRA). For more detail on designated sites and HRA, see the main page on this topic.

The SAC is designated for the River Lambourn itself, which is one of Southern England’s longest and finest examples of a chalk river. This type of aquatic habitat supports rich aquatic plant and invertebrate diversity and is highly threatened. Chalk rivers rely on crystal clear, nutrient-poor groundwater to remain healthy, and like many other examples the River Lambourn is under significant stress due to excess inflow of dissolved nutrients from agriculture and from domestic sewage (both treated and untreated; the treatment process does not remove dissolved nutrients). Increases in dissolved nutrients are likely to affect the SAC by causing blooms of algae, reducing the oxygen content of the water (eutrophication) and encouraging nutrient-tolerant vegetation which aggressively outcompetes the existing aquatic plant species.

While sources of nutrients close to the river are likely to have the most acute effects, all increases in nutrients within the hydrological catchment are likely to contribute to an in-combination significant effect on the SAC. Although the SAC itself is within West Berkshire, part of this catchment is located within Vale of White Horse (see below). Therefore, there is a risk that some developments within the District may contribute to this significant effect.

In 2022, Natural England issued advice to LPAs, which:

• Confirms that the River Lambourn is already in an unfavourable condition, specifically due to levels of phosphorus pollution.
• Sets out NE’s view that any development delivering a net increase in overnight accommodation, plus certain other types of development, will contribute to an in-combination effect on the SAC, and thus will require assessment under the HRA process.
• Suggested that a “nutrient neutrality” approach may be a possible means of mitigating impacts of nutrient pollution on the SAC.

2. What is Nutrient Neutrality?

Nutrient Neutrality is an approach which ensures that nutrient pollution is not worsened as a result of development. Proposals which generate and discharge phosphorus into the River Lamborn SAC nutrient catchment must demonstrate that, as a minimum, the same amount of phosphorus can be removed through mitigation. To do this, nutrient calculators are used to assess proposals and guide mitigation requirements. A nutrient calculator is a spreadsheet-based tool for calculating nutrient discharges before and after development, including the effects of mitigation, in a manner analogous to a biodiversity net gain calculation.

3. What is nutrient mitigation?

Nutrient mitigation reduces the amount of phosphorus entering into the nutrient catchment to counteract increases caused by development. It works by reducing the intensity of land use or improving drainage systems, for example:

• Taking land out of agricultural production and creating natural habitats
• Retrofitting existing foul water infrastructure with newer, more-efficient systems
• Providing high-quality Sustainable Urban Drainage Systems (SUDS) which prevent nutrients from leaving development sites.

Vale of White Horse is part of a partnership of LPAs with land within the SAC catchment. This consortium, led by West Berkshire Council, is currently developing a whole-catchment approach to delivering nutrient mitigation. Currently this is not complete, so mitigation must be provided by developers on a case-by-case basis, and address the specific nutrient implications of their development.

4. What types of development require Nutrient Neutrality?

If your planning application is located within the hydrological catchment of the SAC (see Figure 2), as a minimum you will need to supply information to inform HRA screening by the Council. Development within the catchment which results in new overnight accommodation is likely to contribute to phosphorus levels, because overnight accommodation generates wastewater containing phosphorous.  Based on Natural England’s advice, the following forms of development are within the scope of Nutrient Neutrality, and as such would additionally require Appropriate Assessment in the planning process:

• Any residential scheme with a net increase in the amount of overnight accommodation.
  • New homes,
  • Barn conversions and annexes creating a new residential unit
  • Mobile home parks, including extensions of existing facilities
  • Communal schemes such as care homes and student accommodation, including extensions of existing facilities
  • Conversions of single houses to create dwellings of multiple occupancy.
• Any tourist scheme with a net increase in the amount of overnight accommodation
• Hotels, guesthouses and B&Bs (including conversions from dwellings)
• Self-catering holiday chalets and campsites (where any wastewater drainage is provided).
• Other types of tourist accommodation.
• Permitted development leading to an increase in overnight accommodation.
• Any new agricultural development that will lead to an increase in intensity and provide additional nutrients to wastewater. Suitable examples are schemes for new indoor poultry or pig farms.
• Other developments likely to create a large amount of wastewater, such as carwash facilities and some types of industrial schemes.

Householder extensions providing new bedrooms, or ‘granny annex’ developments which do not result in creation of a separate planning unit, do not fall within the scope of Natural England’s advice and Appropriate Assessment would not be required.

Developments which propose a package treatment plant, with a discharge rate of no more than 2 cubic metres per day, may also benefit from a specific ‘insignificant phosphorus discharge to ground’ exemption from detailed assessment and mitigation, subject to certain criteria being met. This matter requires detailed scrutiny of proposals. Applicants wanting to see whether their proposal will benefit from the exemption are advised to seek pre-application advice.

5. At what stage does Nutrient Neutrality apply?

A recent judgement issued by the High Court has confirmed that Nutrient Neutrality can apply to all stages of development management approval.

Where there is an extant permission, granted before Nutrient Neutrality advice was in effect, but where some additional approval is required before works can commence, the development needs to be scrutinised for compliance with Nutrient Neutrality. This requirement applies regardless as to whether the additional approval has nutrient implications or not (e.g., principle of development or foul sewerage details).

This is because approval of the additional detail could be the “implementing decision”, which allows development to commence. Without all relevant approvals being issued, development cannot commence lawfully.

Some examples are provided below to provide clarity.

Example 1:
Planning permission was granted for a single new dwelling within the nutrient catchment prior to Nutrient Neutrality being in effect. Nutrient Neutrality was not considered during the assessment of the original planning application. This permission included a planning condition requiring the developer to agree the materials of the new dwelling with the Council, prior to commencement. The developer submits details to discharge the requirements of the condition.

In this example, the whole development would need to demonstrate compliance with Nutrient Neutrality, even though the submitted detail relates only to external materials. The Council cannot lawfully issue an implementing decision without being satisfied that the development would not worsen nutrient pollution within the identified nutrient catchment.

Example 2:
Planning permission was granted for three new dwellings within the nutrient catchment prior to Nutrient Neutrality being in effect. Nutrient Neutrality was not considered during the assessment of the original planning application. The developer now submits an application to vary the approved plans condition applied to that permission (also known as a ‘Section 73’ application).

In this example, the whole development would need to demonstrate compliance with Nutrient Neutrality. When the Council approves a ‘Section 73’ application, a new and separate planning permission is being issued. This application would need to demonstrate compliance with Nutrient Neutrality for the Council to lawfully issue a decision, regardless of the fact that there is a similar extant permission.

Example 3:
Planning permission was granted for a barn conversion, creating a new residential planning unit, within the nutrient catchment after Nutrient Neutrality being in effect. Nutrient Neutrality was demonstrated during the application process and the Council deemed the proposed nutrient mitigation measures to be appropriate.  This permission included a planning condition requiring the developer to agree tree protection details with the Council, prior to commencement. The developer submits details to discharge the requirements of the condition.

In this example, the development has already demonstrated compliance with Nutrient Neutrality. This does not need to be demonstrated again, unless there are material changes which would impact the previous Nutrient Neutrality assessment. The submitted tree protection details can be considered in the normal way.

6. Nutrient Neutrality applies to my proposal. What do I need to support my planning application with?

The onus is on the applicant to demonstrate that their proposal complies with Nutrient Neutrality. Applicants will likely need to engage with specialist consultants and provide technical information to demonstrate compliance.

Nutrient Neutrality tools and guidance can be downloaded using the links below. These resources can assess the nutrient implications of a proposed development and guide the provision of appropriate mitigation. Mitigation proposals will need to be devised in conjunction with specialist consultant help.

Applicants proposing development and mitigation within the nutrient catchment are encouraged to utilise pre-application advice to minimise delays to the application assessment process.