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Nutrient Neutrality in Norfolk

Posted by James Watchorn on 18th July 2023
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As is well known, the issue of nutrient neutrality has had a significant impact on granting of planning permissions and the delivery of new homes across Norfolk for the last year. However, Sworders are positive about plans and solutions which are coming forward to address the nutrient neutrality issue and below we explain some of these.

To secure planning permission in the future, all developments in the affected catchments of the River Wensum and The Broads will have to demonstrate ‘nutrient neutrality’, meaning that the nutrients (nitrogen and/or phosphorus) from all surface water runoff and wastewater generated by a development must be less than or equal to the nutrients generated by the existing land use.

There are two methods to establish the scale of the impact of a development, and to identify total phosphate and nitrate loading. An assessment can be made either by using the Natural England calculator, or the Norfolk calculator, developed by Royal Haskoning. But once you know how many credits you need to offset the impact of your development, what happens then?

Measures to mitigate the impact of phosphorus and nitrogen on water quality within the catchments of the River Wensum and The Broads include reducing water usage, providing on site or offsite mitigation solutions, and credit schemes.

Seeking to significantly reduce the amount of water used by your development will proportionally reduce its impact on nutrient neutrality and is therefore the best way, when planning a development from the outset, to reduce the potential costs of credits or the need to use offsite land to mitigate the development’s impact. Reducing water usage from a development will have a proportionate corresponding reduction in the generation of nitrates. Key measures to reduce the proposed water usage of a development include the use of grey water systems, rain water harvesting, and installing water efficient systems and appliances and water butts. A grey water system can enable the re-use of up to 45% of the total in-house domestic water. Limits on per person water usage beyond the requirements of current building regulations can be conditioned by any planning permission to ensure that they are delivered, as detailed in the Nutrient Neutrality Generic Methodology.

In terms of onsite mitigation, the use of an approved onsite package treatment plant to manage foul water will significantly reduce the generation of phosphates from that development. Phosphates account for the majority of the impact on protected habitats in the nutrient neutrality calculation, so it is definitely worth considering including a package treatment plant in the plans for a development, to minimise the water discharge from your development. In many rural areas of Norfolk, where there is no connections to mains drains, a package treatment plant is anyway the most pragmatic solution to manage foul water.

Onsite package treatment plants promote the growth of aerobic bacteria and treat the receiving sewage, producing a minimal effluent which is suitable for discharge to a natural watercourse or ground. This can significantly reduce the total phosphate loading generated by a development, and would enable a developer to rule out likely significant effects on the protected habitats.

If these measures do not fully address the issue, examples of onsite or offsite mitigation schemes include creation of wetland to strip nutrients from water, or creating buffer zones along rivers and other watercourses. If an applicant has land within the site or offsite within the same catchment which is suitable for such uses and is available in perpetuity, this could be offered to set up environmental schemes to offset the impact of the development.

Finally, credits can be bought to offset the impact of your development. Plans for a credit scheme are developing; the Norfolk planning authorities have recently set up a joint venture with Anglian Water (Norfolk Environmental Credits Ltd) to enable credits to be traded. The company recently launched its credit trading platform which is expected to start trading shortly. It will sell credits which developers can buy in 0.1kg units, and then will use the money to invest in environmental schemes which provide nutrient neutrality mitigations, such as managing wetlands or fitting water saving devices into homes.

So solutions to the nutrient neutrality issue are starting to evolve and over the coming months we at Sworders will be keeping fully briefed on these, so that we are able to help and advise you on the best course of action to address nutrient neutrality, to enable you to successfully gain a planning consent.

Lois Partridge

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