Nutrient Neutrality Assessments

The legal background

In 2019 the European Court of Justice ruled that any additional nutrient loading to 'designated sites' that were already in an unfavourable condition would not be permissible by law. Designated sites in this instance refers to Special Areas of Conservation (SAC), Ramsar, Special Protection Areas (SPA) and potential SPA sites. Additionally, the law stated that any developments in their respective catchments would have to demonstrate that there would be no likely significant effect (LSE) from the development on the downstream designated site. This ruling has come to be known as 'The Dutch Case'. Designated sites in England and Wales are protected under the Water Framework Directive Regulations 2017 and the Conservation of Habitats and Species Regulations 2017.

In practice, this means that all developments in the affected catchment will have to demonstrate nutrient neutrality, meaning that the nutrients (nitrogen and/or phosphorus) from all surface water runoff and wastewater generated by the development must be less than or equal to the nutrients generated by the existing land use.

Assessment

Achieving nutrient neutrality often requires mitigation as part of development, either in the form of onsite treatment of wastewater and surface water runoff, or by offsetting any increase in nutrient loading by converting land on- or offsite with woodlands or wetlands.

Water Environment have been at the forefront of this issue, successfully dealing with several cases in Kent (Great Stour), Hampshire (Solent), Herefordshire (River Wye/Lugg) and the Somerset Levels. We have been instrumental in expediting the release of Natural England's guidance to developers in the Stodmarsh catchment. We have helped achieve agreements with Local Planning Authorities and Appropriate Assessments as well as with Natural England for several sites.

This issue is becoming more and more prominent across the country and we can provide expert advice on Nutrient Neutrality to unlock residential developments.

Wetland nutrient mitigation scheme at Conningbrook, Kent

How we work

Nutrient budget — we calculate the development's nutrient load using the relevant Natural England methodology for the catchment, establishing the surplus that has to be mitigated.
Mitigation strategy — we identify the most cost-effective route to neutrality for your scheme, whether through on-site treatment and drainage design or off-site land-use change such as wetland or woodland creation and nutrient credits.
Mitigation design — we design the mitigation and the surface water management that delivers the calculated nutrient reduction, integrated with the wider drainage strategy.
Agreement and sign-off — we prepare the nutrient budget and Appropriate Assessment inputs and negotiate agreement with the Local Planning Authority and Natural England.

Why Water Environment?

We have worked on nutrient neutrality since the issue first arose, across the Solent, Stour, Wye/Lugg and Somerset catchments, and helped shape the guidance developers now rely on. As water and drainage engineers we don't just calculate the nutrient budget — we design the treatment, drainage and land-use mitigation that delivers it, giving you a single team to take the scheme from problem to planning agreement. We work across all of England and Wales.

We are members of the Chartered Institution of Water and Environmental Management (CIWEM) and hold professional qualifications with the Institution of Civil Engineers (ICE).