Development in areas with nutrient-rich water must mitigate its effects and provide a nutrient-neutral environment.
Evidence has shown that residential development contributes to high levels of nutrients in the water environment, specifically nitrates in Solent catchments and phosphates in the Avon catchment. Adverse effects on international nature conservation sites in New Forest area cannot be ruled out.
The extent of nutrient enrichment causes an excessive growth of plants and algae, known as eutrophication, which reduces the oxygen content in water. This process makes it more difficult for aquatic insects or fish to survive, in turn removing a food source from the food cycle for protected species such as wading birds and salmon.
Following recent case law, residential and other development providing overnight accommodation will need to mitigate its effects to become nutrient-neutral, to avoid making the current situation worse. Adverse effects arise from increased sewerage treatment, and from surface water run-off from both urban and greenspace areas.
A nutrient avoidance and mitigation package will be needed to achieve nutrient neutral development before a planning permission can lawfully be issued in accordance with The Conservation of Habitats and Species Regulations 2017.
The Wastewater Treatment Areas Map shows the areas within New Forest that are required to achieve nitrate neutrality. If your development is within this area, it is important you follow the requirements.
You can download a map below showing the wastewater areas.
Waste water treatment areas map [622.0KB]
The Mitigation Hierarchy is the accepted national approach to managing harmful impacts on biodiversity. Avoidance of any impacts should be the first consideration. The next step is on-site mitigation of any impacts that cannot be avoided. The last step is compensation measures in an off-site location to offset any unavoidable remaining impacts.
The avoidance and mitigation package for nutrients should start at development master planning stage with avoidance and mitigation measures to manage surface water run-off. The aim should be to achieve run-off neutrality wherever possible (and a credit where practicable), to minimise the extent of offsetting required for the main source of additional nutrients, foul drainage.
In most cases on-site mitigation will not be enough and additional off-site offsetting measures will also be required. Off-site measures may include:
The Council is working with partners to identify appropriate schemes to provide offsetting credits. This web page and the Nutrient Position Statement adopted 2019 will be updated when further details are available. Progress is as follows and the current best estimate is that mitigation credits may be available from the first quarter of 2021.
As part of the information needed to determine relevant planning applications, a European Site avoidance and mitigation checklist will be required. You can download this document below.
European site avoidance and mitigation checklist [211.38KB]
This web page contains the latest information currently, but our adopted 2019 Position Statement on nutrient neutral development can be seen below. Whilst the position statement refers to nitrates in the Solent, the same principles apply to phosphates in the River Avon. The Position Statement will be updated when there are specific mitigation programmes available.
Position statement on nutrient neutral development [277.73KB]
Links to the latest documents on nitrate neutrality in the Solent can be downloaded below
Solent Nutrients June 2020 [2.41MB]
Solent Nutrient Advice - Non-Technical Summary [586.55KB]
Nitrogen Budget Calculator [47.57KB]
An interim development phosphate budget calculator can be downloaded below. This is a modified version of the Natural England Solent nitrate calculator.
Interim NFDC Phosphate Calculator [54.24KB]
Land use leaching data has been sourced from Farmscoper, simplified for general use, and from Natural England nutrient methodology for parts of the upper Stour catchment. Extracts from the Stour methodology most relevant to Avon phosphorus are attached below.
Stodmarsh methodology phosphate extracts [210.48KB]
The calculator is 'interim' as further work is underway in DEFRA and the leaching rates and other assumptions in this document may be updated early in 2021. It will however provide a general estimate of mitigation requirements for planning purposes.
Paragraphs 4.18 - 4.19 of the NE Guidance v5 includes the following statements:
Natural England recommends that, as a starting point, local planning authorities should consider using the average national occupancy rate of 2.4
Competent authorities may choose to adopt bespoke calculations tailored to the area or scheme
Calculations for occupancy rates will need to be consistent with others used in relation to the scheme (e.g. for calculating open space requirements), unless there is a clear justification for them to differ.
For residential planning applications in the NFDC area the following occupancy rates will be applied, consistent with the approach for mitigating the recreational impacts of new housing on the New Forest European sites.
| Dwelling size | Occupancy per unit |
| Studio or 1 bed | 1.4 |
| 2 bed | 2.1 |
| 3 bed | 3 |
| 4+ bed | 3.75 |
| Unspecified | 2.63 |
The unspecified dwelling size assumes a housing mix compliant with 6.1 of Policy HOU1 in the Local Plan 2016 - 2036 Part One: Planning Strategy
For outline planning permissions, at detailed application stage we will require that the nutrient budget for the site be recalculated for the actual dwelling mix and layout. Depending on the final unit mix the number of dwellings that can be accommodated may change from the figure in the outline permission.
Units of visitor or institutional accommodation, or other proposals that include overnight stays including campgrounds, will be calculated on a dwelling-equivalent basis.
As a starting point the occupancy rate for a studio/1-bed dwelling will be applied to a hotel, guesthouse, care home 'room' or a campsite pitch. Relevant and robust evidence on rates of occupancy, including seasonal variations or periods of closure, will be taken into account.
The General Permitted Development Order (GPDO) allows for the change of use of some buildings and land to Class C3 (dwellinghouses) with this development subject to a prior approval process. However the Habitats Regulations also apply to such developments. We are obliged by the regulations to assume that there will be a significant effect on the New Forest and Solent SPAs.
Any development for prior approval should also be accompanied by an application for us to do a Habitats Regulations Assessment on the proposed development (please note there is a £30 fee for this). The development will need to include a mitigation package to mitigate the significant effect on the New Forest and Solent SPAs which new residential development would otherwise result in.
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