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There are a lot of options around for nutrient neutrality mitigation and quite often you'll see large documents on council websites offering up lots of different methods by which you can mitigate against phosphorus or nitrogen pollution however these long lists can be confusing and of course some of them have complications which these high-level documents will not highlight so here below is a list of mitigation options that we have used in support of projects in nutrient neutrality areas and have actually worked.
We have given an example in each instance so you can have a look how we did it.
In terms of reliability and simplicity you can't really beat trees for phosphorus mitigation however not everyone will have space for trees you will need about 0.6 hectares of Native woodland to offset phosphorus or phosphates from one dwelling this works best for people who are building a house or converting a barn in a rural setting where there is plenty of space to plant trees you will also need a really really efficient treatment system which treats the effluent down to around 0.06 milligrams per liter this will involve a treatment plant and then a secondary filter to remove nearly all of the phosphorus.
Example: 2022/1945/REM - Mendip Council
Another fairly reliable option is upgrading a septic tank to a treatment plant. This will result in a reduction in nutrient loading to the catchment and the resulting reduction can be used to create a credit which is then used offset the new development. This works quite well if you have a septic tank to upgrade, but if you don't have one then you can always try and find one in the catchment and get it upgraded.
Most people well be amenable to the principle of having their septic tank upgraded plus a small fee for their trouble. However, when the details are revealed of the legal ties which are placed upon the property where the tank is upgraded, this is off-putting for many, if you approach someone who owns their own property in the middle of nowhere with no ties on it and then say that you are going to require them to sign legal documents, binding development sites, to their home where they live . . . then this generally puts people off.
However, if you own a house and you are building next door to it and it has a septic tank that can be upgraded then this is a very good option and in fact we have used this a number of times in Cornwall and Somerset and various other places and it's works reasonably reliably .
Example : 21/03851/FUL - Mendip Council
One of the more recent mitigation measures which we have finally got confirmation that actually works is combined sewer removal this is a really good method for creating mitigation as it can be used in suburban areas which are on main sewer.
It's quite good because the amount of water that you divert from a combined sewer (which is a sewer that takes both surface water and foul water) is treated at the sewage treatment works to a set level and so in areas where the treatment work is very poor (say Wellington and Somerset with a discharged consent limit of five milligrams per liter) the water which is diverted from the sewer saves five milligrams per liter and so in areas where the treatment works doesn't treat the water very well you have slight advantage, or at least the negative impacts of poorly functioning so treatment works are balanced out!
Iin order to work you need around 100 meters squared of area roof and drives for example to be diverted from combined sewer per dwelling to be mitigated against. Diverted roof water will go into a sake of a soak away, this does work and we have a couple of applications which have gone through on this basis.
However, you should be prepared to do soakaway testing which is pretty expensive. When you put in your nutrient your charity report stating that you would like to divert it combined sewer they will want to know what you're doing with the water and if you have a reasonably sized back garden you can put it in a soakaway, but the council then ask for a soakaway testing report to prove that it will actually work. This can be a bit annoying and messy because you have to dig holes in your garden but nonetheless is still a good way of creating mitigation with the advantage that you don't have to pay a deposit on nutrient credits and your also really doing some good because rain water in foul sewers is a really bad idea and is responsible for lots of environmental damage which isn't linked to phosphates or nitrates.
Example: 23/02721/FUL - Sedgemoor Council
The below section was written by a machine.
In many regions across the UK, new residential developments are currently stalled due to "nutrient neutrality" requirements. Natural England has identified numerous catchments where additional inputs of nitrogen or phosphorus from new housing would negatively impact protected habitats. To overcome these hurdles, developers must demonstrate that their projects are nutrient-neutral. This page outlines the technical nutrient neutrality mitigation options available to unlock the planning process.
Mitigation measures are designed to offset the increase in nutrient loading caused by the development’s wastewater and surface runoff. These can generally be categorized into two approaches:
The suitability of mitigation options varies significantly depending on the specific catchment and the nutrient of concern. For instance, developments in the Somerset Levels and Moors are primarily concerned with phosphorus, while sites near the Solent focus on nitrogen. Understanding the nutrient neutrality map and the localized thresholds for small-scale developments is essential for selecting a viable mitigation route that will be accepted by planning officers and Natural England.
At Southwest Environmental Limited, we provide the specialized technical evidence required to support planning applications in nutrient-sensitive areas. Our agricultural consultants combine hydrological data with land-use modeling to calculate precise nutrient budgets and design effective mitigation schemes. With over 15 years of experience and 900+ projects delivered nationwide, we offer the professional accreditation (IES/BIAC) and authority needed to resolve complex nutrient challenges and secure your project’s future.