The Solent Mitigation Partnership is delivering a nutrient mitigation scheme through the upgrade of a council-owned sewage treatment works (STW) in Winchester.
Located within Winchester City Council’s administrative area and the River Itchen Nutrient Catchment, the STW previously discharged nutrients into the local water environment downstream. These nutrients, nitrogen and phosphorus, ultimately flowed into the Solent, affecting water quality and sensitive habitats.
The upgraded STW now operates with improved treatment processes that significantly reduces nutrient output. This reduction has been assessed and verified by Natural England, resulting in the generation of 45.10 nitrogen credits and 4.73 phosphorus credits. These credits are available to help offset the applications requiring both nitrogen and phosphorus mitigation in the eligible catchment.
To purchase or reserve credits from this scheme, the development must meet both of the following conditions and fall within the schemes eligible boundary.
A river catchment refers to the area of land where rainwater flows into a specific river or stream; it includes the river itself and all smaller streams and tributaries that feed into it.
To be eligible, a development must be located within the River Itchen Nutrient Catchment.
Only developments located in Winchester City Council’s administrative area are eligible for this scheme.
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 Hampshire to deliver wastewater treatment works upgrades, enabling sustainable development.
A new scheme in Winchester will reduce nutrient pollution in the River Itchen by upgrading council-owned septic tanks. This will generate verified nutrient credits, helping unlock housing development while protecting the area’s sensitive ecosystems.
