Winchester is committed to balancing both the need for housing and the environment and therefore achieving sustainable development.

In 2019, Natural England issued advice to Winchester that requires new “overnight accommodation” (e.g. houses, hotels, care homes, etc) to mitigate for any increase in nutrients pollution coming from the development site for 100 years. Within the Winchester district, all areas must consider nitrate impact. For certain areas, nitrates and phosphates must be considered which is explained below.

One of the impacts of building a new home is an increase in nutrient pollution entering the environment. This pollution can come from increased use of wastewater treatment works and runoff from roads and gardens. Nutrient (Total Nitrogen and Phosphorus) pollution can have a significant impact on lakes, rivers, ponds, and the sea through a process called eutrophication. Eutrophication causes excessive algae growth which can damage the environment. High levels of nutrients and signs of eutrophication have been found across the Solent.

Nutrients Illustration ^{(pdf, 1.4mb)}

The Nutrient Map below shows the three riverine catchments that fall within the Winchester district in relation to nutrient neutrality. This includes East Hampshire and the Test and the Itchen catchment.

All relevant development in these catchments must consider nitrate neutrality. If the development site is within the catchment of the river Itchen, the development must consider both nitrate and phosphate neutrality.

We've worked closely with partners over the previous years to find a process to enable developments to meet nutrient neutrality.

When making planning decisions, we are required by law to take the nutrient issue into account as part of the overall planning assessment. We can only grant approval for affected development when we're satisfied that the site does not contribute to the nutrient issue. If the site does result in additional nutrients, we're able to approve development if an acceptable mitigation solution is secured. 

In 2020, we adopted a Nutrient Position Statement for nitrate neutrality, which sets out a strategy that allows development to be approved subject to a condition that secures acceptable nitrate mitigation. More recently, we've prepared a topic paper to explain progress made to provide solutions for mitigation. You can find this topic paper on our Local Plan website.

For phosphate neutrality, third-party mitigation schemes are available, and your case officer will be happy to discuss any mitigation solution proposed alongside our partners at Natural England.

For more information on schemes available to purchase credits, see our Nutrients Illustration ^{(pdf, 1.4mb)}.

Some private suppliers of nutrient credits are providing homeowners with grants or lower fees for upgrading their septic tanks in return for the value of the nutrient credit.  We can’t promote private companies, so if you’re interested in this route, make sure to thoroughly research your options and any legal consequences before entering into any agreements such as these.