Nutrient neutrality - how might it affect development

Nutrient pollution is a big environmental issue for many of our most important river catchments and waterbodies. In freshwater habitats and estuaries, excessive levels of nutrients can cause the rapid growth of certain plants through the process of eutrophication. This is damaging to wildlife.

The sources of nutrients generally include sewage treatment works, septic tanks, livestock, arable farming, industrial processes and urban runoff. Where sites are already in unfavourable (poor) condition new development can make matters worse.

Nutrient neutrality is one approach to ensuring that new housing development does not lead to an increase in the levels of nutrients flowing from the development to the receptor (the protected river and its catchment). In the affected areas developers must prove their schemes would be nutrient neutral by demonstrating how they would remove or offset the full amount of nutrients anticipated. At its simplest level this could be through demonstrating through the use of a ‘calculator’ that after development a scheme would generate the same or less nutrient outputs than the site was already contributing before development.  However in many, if not most developments, additional interventions may be required to ensure that development does not increase nutrient levels added to sensitive sites.

In practice, this could mean that developers may need to identify, fund and in some cases deliver additional offsite and onsite mitigation measures.  Onsite mitigation measures, such as the adoption of water efficiency measures and the appropriate use of sustainable drainage could help, especially if your site is large, previously developed (and in particular already discharges wastewater), or offers the potential to include measures to reduce the levels of nutrient in the watercourse or one of its tributaries directly (for example through the construction of reed beds, silt traps or other measures).  If mitigation has to be offsite these can take time to identify and deliver, meaning development could be delayed.  It is expected off site measures would be identified and coordinated by local authorities. Clearly, these could take time to identify, although the government has made some funding available to councils, presumably to help address the need for offsite measures to be identified.

Additionally, wherever you are planning for development, which is caught by this requirement, it is likely that you will need to include mitigation to specifically deal with the impact on a sensitive site.  Wherever you include measures specifically to do this, there is a requirement for the council to prepare a Habitat Regulation Assessment (HRA), sometimes called an Appropriate Assessment. In practice, many councils will not be geared up, or have the expertise to do this so developers may be asked to submit a shadow HRA to assist the council in discharging their obligations in respect of the Habitat Regulations.

Finally, it’s always worth checking the areas affected.  Catchments rarely cover the whole district, though given the way the government has published recent announcements you may think that whole districts are affected. In practice, it may only be a small or localised part of the council area subject to this additional requirement.  It is also worth being mindful of where any foul flows from your new development go.  If your site is on the edge of the catchment it is always worth checking which treatment works will receive any foul water. In some instances, the foul water from a development that sits inside a sensitive catchment is taken out of the catchment to treatment works that discharge to watercourses unaffected by nutrient neutrality requirements.  Where this is the case it significantly reduces the potential for development to affect water quality in the sensitive site.