How new phosphate targets may impact on your development

Page updated on: 22/06/2022

Natural Resources Wales (NRW) has published new targets to reduce river phosphate levels in special areas of conservation (SAC) across Wales.

The review follows new evidence from the Joint Nature Conservation Committee that warmer and drier weather, predicted as a result of climate change, could reduce river flows during the summer and therefore increase phosphate concentrations. It is also based on new evidence about the damaging effects of phosphates to water ecosystems and species.

At present, over 60% of waterbodies in Wales fail against the tighter targets, and Welsh local planning authorities are being asked to take more action to avoid further deterioration of the environment. It means any proposals for development within SAC river catchments - in particular those that will generate increased volume or concentration of wastewater - must now prove that the design will not contribute to increased phosphate levels.

In Carmarthenshire, the Afon Teifi, Afon Tywi, River Wye and Afon Cleddau are located in special areas of conservation. At present the Afon Teifi and Afon Cleddau are failing against NRW’s targets. Developments in proximity to these rivers may have limited capacity to connect to the public sewerage system and alternative solutions must be found that will meet the new targets, either by being phosphate neutral or bettering phosphate levels. Download the Carmarthenshire catchment area map (.jpg) 

Until we have received further guidance and are able to measure and mitigate the impact on phosphate levels, we are unable to determine some planning applications in these SAC areas. This is not unique to Carmarthenshire - many other Welsh local planning authorities are in the same situation which has caused many construction projects across Wales to be put on hold. Whilst we are working hard to reach a solution, this may unfortunately take some time.

Next steps

We have written to Welsh Government outlining our concerns about the impact on development and have made clear that we want to find a solution as quickly as possible. We are taking a number of other proactive steps:

  • Producing guidance to help developers understand what is required
  • Creating a phosphate calculator for developers to calculate the level of phosphates their development will generate, together with calculations to mitigation and offset phosphate levels
  • Setting up a phosphate stakeholder forum

We recognise that this situation will be frustrating for developers - we want to work with you to find solutions that improve the condition of our rivers, that are feasible and can be implemented quickly and successfully. We want to engage with a wide range of people representing homebuilders, employers, the farming community, residents, environmental groups and more to discuss these issues.


Our nutrient budget calculator is now live in test mode - we will be gathering feedback over the next few weeks and using this to make any necessary improvements. 

This enables you to calculate the phosphate levels that a proposed residential development in Carmarthenshire could produce. This is an important first step in allowing nutrient neutral development to proceed and is the first of its kind launched in Wales.

This is a free resource, designed specifically for Carmarthenshire, it will support you to understand the impact of your development and will allow you to confirm the proposed development’s phosphate budget and consider mitigations.

Although it is not required that you use this calculator, we strongly encourage you to do so. Any applications submitted using alternative calculators will be subject to additional scrutiny to determine their relevance to conditions in Carmarthenshire.

Calculator Guidance documentThis document has been produced as an instructional guide to help you use the calculator


How it works

Simply input the information specific to your development, and site, into the calculator and work through the stages - instructions have been provided to help you. 

The calculator will produce a value of phosphorous in kg per annum. The end value can be used to help you consider your phosphate mitigation options. The calculator will not estimate the amount of land required for any form of mitigation due to the numerous variables in nature-based solutions that may vary depending on proposed maintenance, maturity and site-specific conditions.

A set of mitigation guidelines, to be published shortly, will further assist you in the selection and implementation of mitigation options.

Use The Carmarthenshire Nutrient Budget Calculator

We welcome your feedback during the test period of the calculator. If you have any comments, please let us know by emailing During the test period, we will be carrying out a technical review of the data and calculations used and will use this - together with your feedback - to develop the calculator and our guidance further.

Phosphorous is a nutrient that occurs naturally in low levels and is necessary for the healthy functioning of rivers. It is released slowly at low levels from natural sources, from natural bankside erosion for example. However, in high levels it is the most harmful nutrient in freshwater and can lead to eutrophication - where an excess of nutrients causes a dense growth of plant life and subsequent death of animal life due to lack of oxygen.

The main sources of phosphorous are agriculture (found in fertilisers and runoff from manure) and sewage (from homes and other developments that generate wastewater containing sewage, food waste and cleaning products).

Whilst farmland is naturally able to absorb phosphorous, much of the land in Wales has now reached a saturation point and is unable to absorb the excessive quantities. Growing populations and increased housing has resulted in rising levels of phosphorous in wastewater. This is causing damage to the rivers and ecosystems it supports.

Types of development that may be affected include (this list is not exhaustive and is subject to review):  

  • New residential units including homes, gypsy and traveller sites/pitches
  • Residential extensions where there will be an increase in water volume
  • Tourism attractions and commercial developments where overnight accommodation is provided
  • Agricultural development, including prior notifications (developments that don’t require planning permission, but where the local planning authority needs to check that it is allowed) including additional barns and slurry stores likely to lead to increased herds
  • Prior notifications for change of use of office to homes and agricultural buildings to homes

Currently we are unable to process some applications of this type. Our position will be updated once we have received further guidance and are able to measure and mitigate the impact on phosphate levels.

We are still able to determine some applications in phosphate sensitive areas, including:

  • Any development that does not increase the volume or concentration of wastewater, including extensions that do not increase occupancy or the volume or concentration of wastewater
  • Any development which improves existing water quality discharges by reducing phosphates in wastewater, or by decreasing the volume of wastewater produced (for example, by improvements to existing wastewater treatment infrastructure)
  • Any development connecting to a public wastewater treatment works where the permit has phosphate conditions in place and there is confirmation that there is capacity to treat the additional wastewater, and additional phosphate, from the proposed development
  • Private sewage treatment systems discharging domestic wastewater to ground that are:
    • Built to the relevant British Standard (BS 6297:2007+A1:2008)
    • Where the maximum daily discharge rate is less than 2 cubic metres (m3)
    • The drainage field is located more than 40m from any surface water feature such as a river, stream, ditch or drain
    • The drainage field is located more than 50m from a SAC boundary
    • To ensure that there is no significant in combination effect, the discharge to ground must be at least 200m from any other discharge to ground and the density of discharges to ground must also not be greater than 1 for every 4ha (or 25 per km2).

If you have not yet submitted an application you may wish to wait for further progress on solutions.

If you still wish to proceed, or have already submitted an application, please provide us with as much information as possible regarding the foul drainage proposals for your site - especially if you are in a non-mains sewer area - to assist us when considering the impact of your development on phosphate levels.

You could withdraw your application and wait for further progress on solutions or speak to your planning officer to agree an extension to your application.

You could also exercise your right of appeal if no decision has been made after eight weeks from when your application was registered/validated, however the Planning Inspectorate will also consider the impacts of the development on phosphate levels.

We also advise you to keep an eye on your application progress on our system and sign up for updates. 

Our initial understanding of the guidance meant that we screened in any application for a domestic extension that created the potential for increased occupancy in a dwelling.

The application of this rule has numerous implications, including quality of life for occupancy levels that do not change, and socio-economic implications including the retention of families in affected catchments. The efficacy therefore of correlating extensions with an increase in wastewater levels is not satisfactorily reliable.

NRW have not issued new guidance in this regard, but have instead provided clarification on the screening of applications for domestic extensions, stating that it would be unreasonable to assume that a domestic extension (i.e. an extension to a dwelling house comprising a single household, which will remain a single household) would result in a corresponding increase in foul water volume from the property, as the occupancy of that property is outside the control of the planning system. As such, a potential change in the number of inhabitants of the property should not justify the triggering of likely significant effects on a SAC.

We have taken the decision to apply this interpretation to applications for domestic extensions in the SAC catchments in Carmarthenshire, as a practical and common-sense approach.

Please note that this rule does not apply to applications for an annexe.

It is not normally considered environmentally acceptable to install a private sewage treatment facility in areas where there are main sewers because there is greater risk of failure, which could lead to pollution.

Welsh Government planning guidance states that, where possible, new development foul drainage should be discharged into a public sewer.

If, because of cost and/or practicability, it can be demonstrated that connection to a public sewer is not feasible, then a private treatment plant - or non-mains foul sewage disposal - could be considered.

Please note that you must have an environmental permit, or register an exemption with Natural Resources Wales, to operate a private drainage system. NRW will not normally grant a discharge permit for a private sewage treatment system where it is reasonable to connect to the public foul sewer.

When there is a change from existing commercial (or other similar) use to residential use it is assumed that this will result in more waste-water being produced and therefore more nutrient discharges to waste-water treatment plants.

Such plants have a capacity, and when reached there is no easy way to create more space. This creates greater risk of overloading which could increase nutrient discharges into watercourses.

This type of change of use will therefore require a Habitats Regulations Assessment (HRA) and mitigation.

New agricultural developments involving the storage, management and spreading of organic material, and within the catchment of a river SAC have the potential to contribute towards the amount of phosphorus entering the designated site. It is likely that such developments will be affected and need to provide mitigating measures.

There are nutrient management, land, manure, and habitats management measures that can be put in place to reduce the amount of phosphate entering rivers from diffuse sources. There are also immediate changes that can be made, for example erecting fencing along riverbanks to prevent livestock entering the rivers.

We would like to explore catchment management ideas with the farming community. Please get in touch with us.

Unfortunately yes - the LDP process will be delayed as we re-assess the implications and remove development allocations within phosphate sensitive catchments. We have written to those who have asked to be kept up to date on progress of the LDP - if you wish to be added to this mailing list, please sign up.

Healthy rivers support social, economic, and environmental resilience and the capacity to adapt to change. We want to find solutions that enhance biodiverse natural environments and promote healthy functioning ecosystems. We want to work with environmental and river groups in finding solutions and would welcome your involvement. Please get in touch with us.

Yes, and they are primarily nature based. The issue can be complex and a range of measures such as removal of phosphate at source, mitigation, and offsetting, needs to be explored on a catchment and site-specific basis.

Mitigation simply means finding a way to prevent phosphate pollution from entering the water. Measures may include the control of pollutant sources, restoration of damaged ecosystems, catchment management, and features such as Sustainable Drainage Systems and river buffer zones that can be used to filter out agricultural run-off and create betterment. Mitigation closest to the source of phosphate pollution is preferable.

Offsetting simply means taking action to reduce phosphorous production to compensate for increased levels elsewhere.

Using agriculture as an example - phosphate is produced by the spreading of fertiliser and livestock grazing on agricultural land. Rain-water carries these phosphates to water courses, particularly on sloping land. Taking a section of agricultural land out of production could halt the addition of phosphates creating an off-set.

The area of land needed to offset new homes would depend on the geology and gradient of the land, and how intensively it was farmed.

Certain areas, (known as European sites) are protected by conservation law - the Conservation of Habitats and Species Regulations 2017 as amended (known as the Habitats Regulations).

These areas include Special Areas of Conservation (SACs) and Special Protection Areas (SPAs).

If a development is proposed in such an area, we must carry out an assessment under the Habitats Regulations, known as the Habitats Regulations Assessment (HRA), to test if whether the proposal could significantly harm the designated features of the site.

The ‘appropriate assessment’ would look at the potential adverse effects of a plan or project (in combination with other plans or projects).

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