Advice to planning authorities for planning applications affecting phosphorus sensitive river Special Areas of Conservation

Recent case law

Planning authorities should consider recent case law when determining planning applications with the potential to affect river SACs, particularly those failing to meet phosphorus water quality standards. 

Please see below for further details of the case law.

How do I know if a proposal might increase phosphorus levels within the SAC?

Every development should be considered on a case by case basis.

Developments should first be screened to determine whether they are likely to have a significant effect. The screening process should apply to developments within river SAC water body catchments and non-SAC tributaries flowing into them. Catchment boundaries can be found on DataMapWales.

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 of foul wastewater
  • any development that improves existing water quality discharges by reducing the phosphorus load of wastewater, or by decreasing the volume of wastewater produced (e.g. by improvements to existing wastewater treatment infrastructure)
  • private sewage treatment systems discharging domestic wastewater to ground, built to the relevant British Standard (BS 6297:2007+A1:2008) as long as 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 and is located more than 50m from a SAC boundary.

Also, to ensure that there is no significant in combination effect, the discharge to ground should be at least 200m from any other discharge to ground. The density of discharges to ground should also not be greater than 1 for every 4ha (or 25 per km2).

What does this mean for development proposals involving connection to public wastewater treatment works?

Developments connecting to an existing public wastewater treatment works that has the capacity and associated phosphorus stripping facility to accommodate additional wastewater is unlikely to increase phosphorus inputs to a SAC beyond what has already been assessed and permitted by NRW.

The planning authority, or other competent authority under the Habitats Regulations, should examine the appropriate assessments carried out in respect of the extant environmental permit(s), along with any new information or changes in circumstances, to ensure that adverse effect on site integrity can be ruled out.

There is a presumption that all rainwater is kept separate from foul wastewater and discharged in line with planning guidance on rainwater disposal. 

Read more about drainage on our Sustainable drainage systems page

For such development proposals, we advise the planning authority to seek the following information in support of a planning application:

  • confirmation of how foul drainage will be managed;
  • scale plans showing the location of the nearest mains sewer and proposed connection point

We also advise the planning authority to obtain evidence that an application has been made to the sewerage undertaker for connection to a mains sewer, and a copy of their formal response confirming either:

(a) there is capacity to treat additional wastewater and phosphorus from the proposed development (in combination with other planned development) within the existing discharge permit limits, or

(b) the necessary treatment capacity to remain within existing discharge permit limits will be delivered within the current Asset Management Plan (AMP) period.

What does this mean for development proposals involving private sewage treatment systems?

The first presumption when drawing up sewerage proposals for any development, must always be to provide a system of foul drainage discharging into a public sewer.

See Welsh Government Circular 008/2018 (planning requirement in respect of the use of private sewerage in new development, incorporating septic tanks and small sewage treatment plants).

If, by considering the cost and/or practicability, it can be shown to the satisfaction of the planning authority that connection to a public sewer is not feasible, a package sewage treatment plant can be considered.

Only if it can be clearly demonstrated by the developer that connection to the sewer, or the use of a package treatment plant is not feasible, should a system incorporating septic tank(s) be considered. Additional guidance on the use of private sewage treatment in an area with a public sewer can be found on our page Private sewage treatment in an area with a public sewer, and on the Planning Policy Wales website.

We encourage developers to use our environmental permitting pre-application advice service when considering private sewage treatment systems to identify any constraints that may apply.

We do not consider drainage schemes discharging to ground via a drainage field likely to have a significant effect on phosphorus loads within river SACs as long as it is built to the relevant British Standard and meets the screening criteria set out above.

Other forms of development involving private sewage treatment systems should be subject to HRA.

We advise planning authorities to seek the following information in support of a planning application or Habitats Regulations appropriate assessment for a scheme involving a private sewage treatment system:

  • confirmation of how foul wastewater will be managed;
  • clear scale plans showing the location of the proposed private sewage treatment system and discharge location;
  • where a private sewage treatment system is proposed within a sewered area, evidence to justify why a connection to mains sewer is not feasible in line with Circular 008/2018 and Planning Policy Wales
  • For all other private sewage treatment systems, evidence that Circular 008/2018 has been followed
  • Where discharges to ground are proposed, developers should provide the results of infiltration testing with calculations to demonstrate that the drainage field size and design is appropriate for the volume of discharge proposed and follows the relevant British Standard.

Applicants should also provide, where available, copies of any Natural Resources Wales environmental permit or registered exemptions to discharge to ground or to a watercourse.

What does this mean for development proposals involving agricultural development?

New developments involving the storage, management and spreading of organic material within the catchment of a river SAC have the potential to contribute towards the amount of phosphorus entering the designated site, and should be screened to determine if they are likely to have a significant effect.

Avoidance and mitigation measures

Measures intended to avoid or reduce the harmful effects of a plan or project on SACs should not be considered at the screening stage for likely significant effect.

The efficacy and reliability of any mitigation measures should be established through the appropriate assessment.

Planning authorities should seek evidence from developers who are proposing measures to avoid or mitigate potential phosphorus impacts, demonstrating those measures are guaranteed, effective, reliable, timely and will be maintained for the lifetime of the development.

We also advise planning authorities to seek confirmation that the proposed measures can be legally enforced.

For each measure, we advise planning authorities to receive details on:

  • how the measure would avoid or reduce adverse effects on the SAC (considering the predicted duration of the effects);
  • how the measure will be implemented, and by whom;
  • how the measure will be maintained and who will be responsible for maintenance

Advice for the review of local development plans (LDPs)

All LDPs should be screened to determine whether any policies are likely to have a significant effect on a river SAC

Policies can be screened out as not likely to have a significant effect in relation to increased phosphorus loading if there are no pathways for increased phosphorus impacts.

Any LDP polices relating to schemes for private sewage treatment systems should ensure no adverse effects on the integrity of any river SACs where:

  • discharges are direct to surface waters; or
  • discharges are to ground and do not meet the screening criteria set out in this document.

Allocations for development that are proposed to be connected to a mains wastewater treatment works and have the potential to increase phosphorus loading, should be assessed as follows.

Allocations where there is capacity for additional wastewater

Where the wastewater treatment works has capacity to accommodate additional wastewater and any additional phosphorus from the proposed development (in-combination with other planned development) within existing discharge permit limits, the planning authority should review the appropriate assessments carried out for the extant environmental permit(s), along with any new information or changes in circumstances to be certain there will be no adverse effect on site integrity.

Allocations where capacity for additional wastewater is planned

Where the wastewater treatment works does not currently have sufficient treatment capacity but it is planned under the Asset Management Plan (AMP) - the planning authority should undertake an appropriate assessment or a review of the appropriate assessment already carried out for extant environmental permits (along with any new information or changes in circumstances) to be certain that there will be no adverse effect on site integrity. Considering the Dutch Nitrogen ruling, a conclusion of no adverse effect on site integrity can only be made where future improvements or enhancements within the AMP are certain at the time of appropriate assessment.

Allocations where there is no capacity for additional wastewater

Where the wastewater treatment works has no capacity in place or planned within the current AMP period the planning authority should undertake an appropriate assessment. 

Permitted Development Rights

We advise that any development proposal within the catchment of a river SAC, which benefits from permitted development rights under the General Permitted Development Order 1995 (GPDO) and will increase phosphorus discharge, should be subject to prior approval.

Several classes of development, including agricultural development, benefit from permitted development rights under Article 3 of the Town and Country Planning (General Permitted Development) Order 1995 (the GPDO), subject to conditions and limitations specified in the Order.

The Habitats Regulations impose a condition on permissions granted by the GPDO so that development likely to have a significant effect on a SAC must not commence until the local planning authority has given written approval.

The planning authority must consult us on the proposed GPDO development and take account of any representations. If we consider the proposed development to have a likely significant effect, the planning authority must carry out an appropriate assessment of development.

The procedures for seeking approval can be found in Annex 5 of The Welsh Government Technical Advice Note 5: Nature Conservation and Planning (2009).

Case law

As a result of the Court of Justice of the European Union (CJEU) decision, known as the “Dutch case”, the scope for authorising new development that will lead to additional phosphorus loading is likely to be limited where the conservation status of the SAC is unfavourable as phosphorus standards are being exceeded.

Planning authorities should also be aware of the domestic decision in the Compton case (Compton Parish Council and others v Guildford Borough Council and another [2019] EWHC 3242 (Admin)). This case clarified the approach to be taken in assessing critical loads when considering if a proposed development would adversely affect the integrity of a SAC that is already subject to excess nutrients, by virtue of the development in question resulting in further nutrient deposition.  

Both the Dutch and Compton cases related to nitrogen, but the principles apply to other nutrients, including phosphorus.

Whilst the nature of development which may be permitted will depend on the facts of each case, planning authorities should have regard to the principles outlined in the case law above when assessing the phosphorus impacts of proposed developments as part of the Habitats Regulations process.

Our advice

This advice is the opinion of Natural Resources Wales as statutory consultee to local planning authorities in relation to nature conservation and impacts of plans or projects on designated sites. It is up to individual planning authorities to take their own legal advice when exercising their statutory functions.  This document will be subject to review and periodic update.

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