The River Itchen catchment, which spans a significant area of the Winchester District, has been facing challenges due to nutrient pollution from nitrogen and phosphorus. This has impacted housing development within this region due to the new requirement that projects are nutrient neutral in order to prevent further pollution.
In March 2022, Natural England issued new guidelines for local planning authorities (LPAs) within the Itchen catchment. These guidelines state that all developers must demonstrate nutrient neutrality for their projects, ensuring that developments do not add to the nutrient load in these sensitive ecosystems. The River Itchen is a Special Area of Conservation (SAC), so it is vital that this is protected.
To address this issue and unlock new housing developments, funding has been allocated through the Local Nutrient Mitigation Fund (LNMF). This funding will be used to upgrade several septic tanks owned by Winchester City Council. These upgrades will improve the tanks’ ability to capture nutrient pollution, ensuring that more nutrients are removed from the wastewater before being released into the environment. The tanks will contribute to the preservation of habitats for wildlife in this protected area.
These upgrades will generate both nitrogen and phosphorus nutrient credits, which developers can purchase to offset the nutrient load of their development. This creates a pathway for housing developments to proceed while maintaining compliance with environmental regulations, helping to balance development needs with protection of sensitive ecosystems such as the River Itchen.
Developers will be able to purchase Nitrogen Credits if their development is in the Test and Itchen Catchment, or Phosphorus Credits if it is within the Itchen Catchment. Winchester City Council is the sole benefitting authority of this scheme, and developments must be located in their administrative area to be eligible to purchase credits from this scheme.
The number of available credits will be confirmed once the scheme goes live and will be verified by Natural England’s discretionary advice service.
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A former farmland site in Stubbington is now a nature recovery area, reducing nutrient runoff into the Solent. The project has generated over 400 verified nutrient credits to support sustainable development in the region.
The Solent Mitigation Partnership is working across the Solent region to deliver wastewater treatment works upgrades, enabling sustainable development.
