Guidance for development within the River Clun Catchment


The River Clun in south Shropshire has particular sensitivities in terms of water quality. This is explained further below, along with information on the process that we must follow in determining planning applications in the catchment which are likely to affect the rivers internationally important wildlife interest. Guidance on the information we require to be submitted as part of a planning application to enable consideration of such proposals is also detailed. A map of the river Clun catchment is available viewing.


Part of the River Clun is a European designated wildlife site known as a 'special area of conservation'. Special areas of conservation are amongst the most important and sensitive sites in the UK and are afforded the highest level of legal protection under the Conservation of Species and Habitats Regulations 2017 (as amended) (the Habitats Regulations). Although the River Clun is important for wildlife such as otter, salmon and trout, the sole feature for which the special area of conservation is notified is the presence of the extremely rare freshwater pearl mussel (Margaritifera margaritifera). A plan showing the location and extent of the River Clun Special Area of Conservation is provided at Appendix 2.

Freshwater pearl mussels are very sensitive to water quality, with juvenile mussels being particularly susceptible to pollution. An assessment of the River Clun Special Area of Conservation shows that it's in an unfavourable and declining condition caused by high levels of phosphate, nitrogen and silt. Agricultural activities give rise to all three of these, whilst development mostly contributes phosphates from surface and foul water discharges. Research shows that phosphate levels in the River Clun are already too high for the pearl mussels to breed and also too high to maintain adult pearl mussels. Therefore, any additional phosphate entering the river will make the condition of the special area of conservation worse.

The provisions of the Habitats Regulations mean that when we determine development proposals in the Clun catchment, we must consider whether there's likely to be a significant effect on the River Clun Special Area of Conservation. This is known as a habitats regulations assessment. When carrying out a habitats regulations assessment, any other existing or proposed plans or projects which may also have an effect must be considered as well – the ‘in-combination test’. If the initial findings of the habitats regulations assessment show that a significant effect on the special area of conservation is likely, either from the development proposal alone, or from the proposal in combination with other plans or projects, we must carry out a more detailed appropriate assessment.

An appropriate assessment evaluates the effect of a development proposal on the integrity of a special area of conservation - in this case, on the freshwater pearl mussel population. If the appropriate assessment shows that an adverse effect can't be definitively ruled out, planning permission can't normally be granted unless the proposal can be modified to remove the effect, or if mitigation measures can be found which would completely avoid the effect. For the latter, there must be scientific certainty that the measures proposed will definitely offset the whole of the identified effect, that the measures are financially and practically deliverable and that they'll last for the lifetime of the development. The measures must also normally be in place in advance of the development.

The Habitats Regulations stipulate that it's the responsibility of the applicant to provide sufficient information to enable us to carry out a habitats regulations assessment and appropriate assessment (if necessary).

Statutory agency advice

Natural England and the Environment Agency are statutory consultees on all planning applications which could affect the River Clun Special Area of Conservation. If either object to an application, and it can't be modified to remove their objection, we won't normally grant planning permission.

In 2014, Natural England and the Environment Agency jointly published a Nutrient Management Plan for the River Clun catchment. The nutrient management plan:

  • Documented all sources of phosphates, nitrogen and silt in the catchment
  • Identified what information was still needed to be gathered
  • Outlined phosphates, nitrogen and sediment reduction measures that might be employed in future, by both land managers and developers, to reduce nutrient levels in the river
  • Set out actions for Severn Trent Water to reduce the amount of phosphates entering the river from new development

In line with the recommendations of the nutrient management plan, Severn Trent Water has carried out upgrades to its waste water treatment works in the Clun catchment. These have reduced the amount of phosphates reaching the river by 75%, and for a while we were able to approve development which connected to the public sewer.

However, in November 2018, a legal judgement known as the Dutch Nitrogen Case (Cooperatie Mobilisation for the Environment UA and Vereniging Leefmilieu v College van gedeputeerde staten van Limburg and College van gedeputeerde staten van Gelderland C-293/17 C394/17), clarified that where the conservation status of a special area of conservation is unfavourable (as is the case for the River Clun Special Area of Conservation) the possibility of authorising activities which may subsequently compromise the ability to restore the special area of conservation to a favourable condition is 'necessarily limited'.

This judgement applies to all development proposals in the Clun catchment which would increase the level of phosphates in the river. Any such increase, however small - including from Severn Trent Water’s upgraded waste water treatment works or from other mitigation measures aimed at facilitating development – would fall into this category and so is not permissible.

Other catchments elsewhere in the country where there are failing European sites due to excess nutrients are in similar situations, with some catchments progressing nutrient offsetting schemes to ensure that pollutants from development can be offset by measures elsewhere in the catchment that reduce pollutant levels in the catchment by a corresponding amount (termed ‘nutrient neutrality’).

We've been advised by Natural England that at this time the validity of nutrient neutrality development in the Clun catchment is highly unlikely to be agreed as measures to offset development proposals may be required to restore the site to a favourable conservation status. The Clun catchment differs from the other areas where nutrient neutrality development is being taken forward as it's a small catchment, and therefore land take for nutrient neutrality development may be needed for restoration, as well as all available mitigation measures.

At present, there is not an up to date Nutrient Management Plan or Special Area of Conservation Restoration Plan for the Clun catchment. This means that the measures required for restoration of the River Clun Special Area of Conservation are currently unknown. Without firstly understanding the required restoration measures, it is Natural England’s position that mitigation measures to ensure that development is nutrient neutral cannot be defined or implemented. This is because Natural England want certainty that any such mitigation measures will not compromise the ability to restore the Special Area of Conservation.

Work has now commenced by Natural England and the Environment Agency, as the two responsible bodies, to scope the Special Area of Conservation Restoration Plan and agree a timeframe for its preparation. The Council is committed to supporting both organisations in this work.

At the same time, the Council is separately taking forward detailed work around suitable mitigation measures to ensure a delivery mechanism for mitigation is put in place as soon as possible. This includes exploring whether development which can clearly demonstrate nutrient neutrality can proceed in the absence of a restoration plan.

On 16 March 2022 we received a communication from Natural England concerning nutrient neutrality in relation to the River Clun Special Area of Conservation. This included a 25 page advice letter, guidance on nutrient neutrality principles, a River Clun SAC evidence pack and a nutrient neutrality summary guide, all of which are available for viewing under ‘Related documents’ on this page.

This communication is consistent with the already published guidance on this page.

The Government also published a statement on nutrient pollution on 16 March 2022 which is relevant for the River Clun SAC catchment: Nutrient pollution: reducing the impact on protected sites.

At a local level we've established a Strategic Clun Liaison Group with local leaders from Natural England, the Environment Agency and Severn Trent Water. The group has produced a position statement to provide an up to date overview of the situation, along with setting a programme of work to identify and address both mitigation and restoration needs in the catchment. However, all parties recognise that the environmental challenges are significant. The position statement is available for viewing under ‘Related documents’ on this page.

Whilst the group will provide the basis for developing a long-term plan, all parties recognise the importance for everyone to play their part over the short, medium and longer term by both identifying nature recovery opportunities and the best ways to implement them.

Whilst we're working with both Natural England and the Environment agency through the Strategic Clun Liaison Group as a matter of urgency to try and resolve this situation, at the current time of writing, development which generates sewage is unable to proceed if it:

  • Increases the number of households in the Clun catchment, or
  • Increases overnight accommodation capacity, or
  • Leads to increased visitors to the Clun catchment

These types of development won't, at this time, pass an appropriate assessment, as even small increases in phosphates entering the river can't be shown to have no adverse effect on the integrity of the River Clun Special Area of Conservation.

These above issues and viewpoints are detailed in the respective agencies’ 'Statements of Common Ground with Shropshire Council', which have been produced following objections from Natural England and the Environment Agency to new housing allocations in the Clun catchment proposed through the new local plan. These are likely to form the basis for discussion before the independent planning inspectors at the 'Examination in Public of the new Local Plan' scheduled for 2022. The statements of common ground can be found at:

The sections below provide the most up to date approach to different types of development in the River Clun catchment, and how we'll assess these for their likely significant effects on the River Clun Special Area of Conservation.

Housing and tourism development connecting to the public sewer

Both National Planning Practice Guidance and the Building Regulations 2010 (Approved Document H) set out a presumption in favour of connection to the public foul sewer wherever it's feasible (in terms of cost and/or practicality). However, as set out above, new residential and tourism proposals which can feasibly connect to the main sewer can't currently be permitted under the Habitat Regulations.

In these circumstances, it is not acceptable to propose a non-mains foul drainage solution where a mains connection is feasible in order to achieve a ‘no adverse effect’ Habitat Regulations Assessment. Allowing non-mains drainage where it is otherwise feasible to connect to the public sewer would be contrary to national planning policy which seeks to protect the environment and secure sustainable development.

Employment development connecting to the public sewer

Employment uses aren't considered, at this time, to increase nutrient levels entering the special area of conservation, as it's assumed that the prospective employees are already living in the Clun catchment, so there wouldn't be a net increase in sewage loading.

Development for annexes/ancillary accommodation and extensions

Proposals for ancillary accommodation and extensions to existing residential properties aren't considered, at this time, to increase nutrient levels entering the special area of conservation, as the number of households residing in the catchment wouldn't increase so there wouldn't be a net increase in sewage loading.

Development using package treatments plants or septic tanks

A development where a connection to the mains sewer isn't reasonably available can make use of package treatment plants or septic tanks to treat and dispose of foul waste.

If a package treatment plant or septic tank is proposed to deal with the foul waste arising from a development, evidence demonstrating that all the following criteria have been met should be submitted with the planning application:

  • Discharges are to ground and are less than 2m3 /day
  • The drainage field is more than 50m from the River Clun Special Area of Conservation boundary
  • The drainage field will not be subject to significant flooding, eg it's not in flood zone 2 or 3
  • There are no other known factors which would expedite the transport of phosphorus - for example fissured geology, insufficient soil below the drainage pipes, known sewer flooding, conditions in the soil/geology that would cause re-mobilisation of phosphorus, presence of mineshafts, etc
  • The discharge to ground is at least 200m from any other discharge to ground
  • A percolation test has been performed of the proposed location of the drainage field with the resulting value lying within the required range under the Building Regulations 2010, which specify an average Vp value of between 12 and 100
  • The package treatment plant or septic tank has sufficient capacity to cope with the maximum occupancy or use of the development. To calculate how much sewage a development will discharge per day see the government guidance: Septic tanks and treatment plants: permits and general binding rules
  • All of the following criteria must also be met:
    • The drainage field is more than 40m from any surface water feature, eg ditch, drain, watercourse
    • The drainage field is in an area with a slope no greater than 15%
    • The drainage field is in an area where the high water table groundwater depth is at least 2m below the surface at all times

Natural England have provided us with a GIS layer which contains information on the last three criteria above, but due to the data licence this can't be shared with developers. We will, therefore, carry out the assessment for these three criteria for each application.

A completed FAD1 form, providing full calculations, together with an accurate, annotated drawing and location plan for the soakaway/drainage field should also be submitted as part of the planning application. The drawing should state the make, model and capacity of the proposed package treatment plant/septic tank.

Appendix 3 contains a checklist to aid applicants in submitting the required information.

Last updated 10 October 2023