How new phosphate targets may impact on your development

Page updated on: 21/02/2023

In January 2021 Natural Resources Wales (NRW) published new targets to reduce river phosphate levels in special areas of conservation (SAC) across Wales.

The review followed 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 designated as riverine special areas of conservation. At present the Afon Teifi, river Wye and Afon Cleddau are failing against NRW’s targets. Although the river Tywi is passing its targets, there is limited headroom. The NRW Compliance Assessment report of Welsh River SACs against Phosphorus Targets report can be accessed here. 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. You can view a map of the river catchment areas here. 

What action have we taken?

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 have also taken a number of proactive steps:

  • We have produced guidance to help developers understand what is required
  • We have produced a phosphate calculator for developers to calculate the level of phosphates their development will generate. This is the only phosphate calculator in Wales, and has been modelled specifically with data for Carmarthenshire.
  • We have produced a Technical Guide – detailing all of the calculations and data inputs used in the calculator.
  • We have produced comprehensive Mitigation Guidelines that explain the most effective types of mitigation that could be utilised in Carmarthenshire.
  • We have established a Nutrient Management Board (NMB) for the river Tywi. This board will be responsible for producing a Plan to improve the condition of the river and to facilitate nutrient neutral development to proceed. Further details of this Board, including a webpage displaying live updates will be posted on this page when it becomes available.
  • We have helped to establish and are members of the Tywi NMB and the Cleddau NMB. We represent the interests of Carmarthenshire at these boards.
  • In July 2022, in recognition of the leadership we have demonstrated in Carmarthenshire, we were invited to the Phosphate Solutions Summit held by the First Minister at the Royal Welsh Show.

Next Steps

  • We are establishing a Technical Advice Group to provide evidence review, scenario modelling and proposals that will be presented to the Nutrient Management Boards for approval.
  • We are in the process of establishing up a River Stakeholder Forum. Membership of this group is open, and we welcome all contributions to help facilitate constructive and lasting change for river health. Further details, including joining information will be posted on this page when it becomes available.
  • The challenges of addressing phosphate pollution are complex, and there is no easy solution. Long lasting solutions will require collaboration with neighbouring Local Authorities, Dŵr Cymru Welsh Water, the farming sector, NRW, Welsh Government and environmental bodies. CCC actively collaborate and share information will all parties on a regular basis via regional and all-Wales meetings.
  • A Strategic Mitigation programme that maximises mitigation and delivers the benefit of that via a credit exchange is being explored. This will remove many of the mitigation barriers that developers are having to address.

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.

This tool 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              

Nutrient Budget Calculator     Mitigation Guidelines


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 phosphorus 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.

The mitigation guidelines, will further assist you in the selection and implementation of mitigation options.


The Council, does not accept liability for any direct or indirect damage, loss or inconvenience caused by the downloading and use of this phosphate calculator from the Council’s website.

Please refer to the Technical Guide for an explanation of the data sets and calculations used in the calculator. If you have any comments, please let us know by emailing The calculator will be subject to periodic reviews and updates to ensure it is based on the best available evidence and accurately reflects the local conditions.

Mitigation Measures

Mitigation measures need to reflect site specific circumstances, and have an understanding of the source of that phosphate pollution.

Dŵr Cymru Welsh Water are in the process of undertaking a review of P sources. Information, this information will help shape the right mitigation in the right place. You can access the source apportionment data here.

More research is required on the efficacy of different types of mitigation options.

Any mitigation measures intended to avoid or mitigate potential phosphorus impacts must demonstrate that they are based on ‘best available evidence’, will be effective ‘beyond reasonable doubt’, are based on estimates that are ‘precautionary’, and can be secured ‘in perpetuity’ (80-125 years).

The proposed measures must also be legally enforced.

For each measure, we need to receive information:

  • detailing how the measure(s) would avoid or reduce adverse effects on the SAC (considering the predicted duration of the effects)
  • demonstrating how the measure(s) would achieve nutrient neutrality
  • confirming how the measure(s) will be implemented, and by whom
  • detailing how the measure will be maintained and who will be responsible for maintenance.
  • showing how the measure will be monitored to ensure it is effective.

Further information on mitigation measures can be found in the latest NRW Phosphate Planning Advice.

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 phosphorus 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 phosphorus, some 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 phosphorus 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
  • Tourism attractions and commercial developments where overnight accommodation is provided
  • New large commercial or industrial developments where customers will be attracted from outside of the catchment such as large retail sites, conference facilities, or major tourist attractions 
  • 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

Further guidance and advice can be found on the NRW Phosphate Planning Advice Page.

The following developments can be screened out as not likely to have a significant effect on a river SAC in relation to phosphorus inputs, as there is unlikely to be a source of additional phosphorus or pathway for impacts:

  • any development that does not increase the volume and phosphorus concentration of wastewater
  • any development that improves existing water quality discharges by reducing the phosphorus concentration of wastewater without increasing volume or by decreasing the volume of wastewater produced without increasing the concentration of phosphorus
  • developments intended to provide services, facilities, commercial sites, or places of employment (e.g., community buildings, schools etc.) for a local population already served by residential connections to existing public or private sewers discharging within the SAC river catchment
  • any development that reduces the frequency, or volume of irregular phosphorus discharges within a SAC river catchment such as the erection of agricultural structures and drainage schemes to separate rainwater from manures and slurries by covering yards and existing manure/slurry stores. Note that any such development must not be linked to an increase in livestock numbers or the capacity for an increase in livestock numbers through provision of additional infrastructure
  • private sewage treatment systems discharging domestic wastewater to ground, which are built to the relevant British Standard (BS 6297:2007+A1:2008),the maximum daily discharge rate is less than 2 cubic metres (m3) and the drainage field is located more than 40m from any surface water feature such as a river, stream, ditch or drain and located more than 50m from a SAC boundary and at least 200m from any other known discharge to ground.

Further guidance and advice can be found on the NRW Phosphate Planning Advice Page.

If your planning application is within a SAC river catchment area, you will need to:

  1. Ascertain if the development can be ‘screened out’ as not likely to have a significant effect on a river SAC in relation to phosphorus inputs. This stage is called ‘the Test of Likely Significant Effects (TLSE)’. Please refer to ‘What sort of development is affected?’ If you feel that your application will not have a significant effect, you will need to provide us with information in support of this.
  2. If the development cannot be ‘screened out’, you will need to calculate the additional phosphate loading from the proposed development using the Nutrient Budget Calculator. There is a written instructional guide and a video to assist you in using the calculator.

  3. You will then need to submit a Mitigation Proposal that demonstrates how the additional phosphate generated will be mitigated. Please see the Mitigation guidelines for detailed information on the most appropriate measures that could be employed within Carmarthenshire.

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. 

Domestic extensions can provide increased living space within existing properties. They may not result in a change in the number of occupants and in our opinion, it would appear reasonable for domestic extensions to be screened out at the test of likely significant effect.  Our view is that unless the proposal would result in the creation of independent living accommodation, a separate planning unit and/or a change in use, where it can no longer be said to be ancillary to the main residence, such developments are unlikely to lead to significant effects on a SAC through changes in discharge of wastewater. However, proposals that lead to the creation of independent living accommodation as a separate planning unit may lead to an increase in occupancy by residents from outside a SAC river catchment, and in these instances, proposals require further assessment.


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.

For more information on the use of PTP’s in relation to phosphate removal please refer to the NRW Phosphate Planning Advice Page.

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


Work has commenced on producing a second Deposit LDP which will incorporate previously agreed Focussed Changes (where they remain relevant). It will also reflect and respond to Covid-19 recovery, the net zero carbon and decarbonisation agenda, new Technical Advice Note 15 / Revised Flood Maps, and Future Wales: The National Plan 2040.

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 phosphorus 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. Rainwater 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).

This phrase refers to the removal of nutrients by developers or local planning authorities to create capacity for growth without causing further deterioration in nutrient levels.

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