Advice to planning authorities for planning applications affecting nutrient sensitive river Special Areas of Conservation
Our advice
Version 4 of this advice, published 28/06/24.
This advice to Planning Authorities is the opinion of Natural Resources Wales (NRW) in relation to nature conservation, and the impacts of proposed developments requiring planning consent, on nutrient sensitive river Special Areas of Conservation (SACs).
For the purposes of the Conservation of Habitats and Species Regulations 2017 (as amended) (referred to in this Advice as the Habitats Regulations), the Planning Authority is a competent authority responsible for undertaking the Habitats Regulations Assessment (HRA) to consider the implications of a plan or project on an SAC. As such, it is a matter for the Planning Authority to determine whether a plan or project is likely to have a significant effect on an SAC having considered this advice.
NRW must be consulted for the purposes of the Appropriate Assessment, as the Appropriate Nature Conservation Body (ANCB), where we will advise on the implications of proposed developments for the site's conservation objectives. We will not advise on matters beyond our responsibilities as ANCB. Planning Authorities should have regard for our advice, but it will ultimately be the responsibility of the competent authority to ensure that the requirements of the Regulations are satisfied prior to consent being given. For this purpose, Planning Authorities should obtain their own independent advice wherever necessary.
Given the diversity of development proposals received by Planning Authorities, we advise that the principles set out below are considered and applied on a case-by-case basis – exceptions will apply, and this will be a matter of judgment for Planning Authorities. Note that the term nutrients is used in this advice to describe phosphorus and ammonia.
What is the issue?
There are nine rivers in Wales that are designated as SACs under the Habitats Regulations. They are the Afonydd Cleddau, Eden, Gwyrfai, Teifi, Tywi, Glaslyn, Dee, Usk and Wye. These river ecosystems support some of Wales’s rarest and most important wildlife including Atlantic salmon, freshwater pearl mussel, white-clawed crayfish, and floating water-plantain.
The environmental targets these rivers should meet to be in favourable condition are detailed as conservation objectives in site Core Management Plans (CMPs). NRW are responsible for the CMPs which can be found for each SAC river on our website
Find Core Management Plans for all river SACs on our webpage 'Find protected areas of land and sea'.
The revised water quality targets in CMPs are set out in the Joint Nature Conservation Committee Common Standards Monitoring (JNCC CSM) guidance (JNCC 2015b, 2016). Public bodies in Wales have a statutory duty to achieve these targets and protect the river SACs through regulation of activities for which they are responsible.
In January 2021 we published a report 'Compliance Assessment of Welsh River SACs Against Phosphorus Targets' in which we presented our assessment of how much phosphorus there is in SAC rivers measured against revised water quality targets. The evidence review showed that over 60% of the water bodies assessed in SAC river catchments were failing to meet the revised water quality targets for phosphorus. An update to phosphorus targets was published in August 2023 'Update to phosphorus targets for water bodies in Special Area of Conservation (SAC) rivers in Wales'.
Read both reports in our Water Reports section
Phosphorus is naturally present in river environments but at very low levels. Human activities such as agriculture and discharge of treated wastewater elevate levels of phosphorus in river flow. High concentrations of phosphorus lead to the process of nutrient enrichment, also known as eutrophication, and can alter the balance of plant species in our rivers causing significant ecological damage.
In January 2024 we published an assessment of other water quality attributes against targets in SAC rivers 'Compliance Assessment of Welsh River SACs Against Water Quality Targets'. The study included an assessment of ammonia which can have direct toxic effects on aquatic life or be a pollutant leading to nutrient enrichment. While most SAC catchments were found to be meeting ammonia targets, Planning Authorities will need to consider the effect of development on ammonia discharges to SAC rivers. Further information is provided in the next section.
Read Compliance Assessment of Welsh River SACs Against Water Quality Targets
For the purposes of this Advice a SAC river catchment describes the hydrological catchment area for a designated river SAC. This includes non-designated tributary catchments draining into the SAC. Under the Water Environment (Water Framework Directive) (England & Wales) Regulations 2017 hydrological features are formally divided into units known as water bodies, with each given a unique identification reference. Water bodies represent a length of river or estuary, a lake, artificial or heavily modified feature such as a canal. Water body catchments are hydrological catchments associated with a given water body.
How does this affect development planning?
Some new developments including housing or agricultural enterprises can lead to increased amounts of nutrients entering the river environment from additional wastewater or land management. Under the Habitats Regulations, Planning Authorities must consider the nutrient impacts of proposed developments on water quality within SAC river catchments.
Planning Authorities should consider case law when determining planning applications or reviewing Local Development Plan policies with the potential to affect river SACs. More detail on case law is provided at the end of this advice.
In SAC catchments failing to meet revised nutrient targets, it is possible that new developments can be authorised if it can be demonstrated they will not lead to further deterioration of water quality and will not undermine the ability for the SAC to meet its conservation objectives.
This may be achieved if:
- developments are not a source of nutrients or
- developments are a source of nutrients but there is no pathway for them to enter the SAC river environment or
- measures associated with a given development are put in place so that nutrient neutrality can be achieved.
Phosphorus and ammonia react differently in the river environment. Phosphorus has a very low decay rate and can accumulate in the river system from multiple point source and diffuse discharges. Conversely ammonia has a much higher decay rate, breaking down through the process of nitrification within the river system. The toxic impacts of ammonia discharges therefore tend to be local to the point of discharge and assessment of impacts should be at that scale. On this basis ammonia failures can be addressed at water body level instead of catchment scale. This means ammonia neutrality is not required and ammonia discharges will be addressed through limits on individual Environmental Permits.
In addition, there may be a limited number of cases where increases in final effluent nutrient discharges may be made from a wastewater treatment works up to the limits conditioned on the associated environmental permit. This will only be possible in certain circumstances as explained in the section What does this mean for development proposals involving connection to public wastewater treatment works?
In SAC catchments meeting nutrient targets, it is possible that new developments can be authorised if it can be demonstrated they will have no likely significant effect or not lead to an adverse effect on site integrity (i.e., will not undermine the ability for an SAC to meet its conservation objectives).
The following sections offer advice for Planning Authorities to consider when determining planning applications or reviewing LDPs that have the potential to affect river SACs.
What is a Habitats Regulations Assessment (HRA)?
Development proposals within a SAC river catchment must undergo an HRA to determine their impact on the designated site and its features. Two principal stages of an HRA are:
- Test of Likely Significant Effect – this is a screening assessment to determine whether a development has the potential to affect an SAC. Where a likely significant effect can be ruled out, no further assessment under the Habitats Regulations is required.
- Appropriate Assessment – where a proposed development is considered likely to have a significant effect, or such an effect cannot be ruled out, a more detailed assessment of the potential impacts is required. The purpose of the Appropriate Assessment is to assess the implications for the river SAC in view of that site’s conservation objectives, and thereby determine whether the proposal could have an adverse effect on the integrity of the site.
What development proposals are unlikely to increase nutrient levels within a river SAC?
Every development should be considered by Planning Authorities on a case-by-case basis.
The following developments can be screened out as not likely to have a significant effect on a river SAC in relation to nutrient inputs, as there is unlikely to be a source of additional nutrients or pathway for impacts:
- any development that does not increase the volume and concentration of nutrients in wastewater
- any development that improves existing water quality discharges by reducing the nutrient concentration of wastewater without increasing volume or by decreasing the volume of wastewater produced without increasing the concentration of nutrients
- 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 nutrient 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. Further information on agricultural developments is provided in the next section.
- private sewage treatment systems discharging domestic wastewater to ground, built to the relevant British Standard (BS 6297:2007+A1:2008) having a maximum daily discharge rate of less than 2 cubic metres (m3) and where 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 50m from any other known discharge to ground.
Note that the screening criteria above should be used to determine if there is a likely significant effect and where the criteria are not met, an Appropriate Assessment should be undertaken.
Find details of registered water quality exemptions on the Data Map Wales website.
Note that not all exempt discharges in Wales have been registered. Applicants should check drainage arrangements with neighbours in addition to use of information available on the DataMap Wales website to determine drainage field locations.
There may also be cases where developments proposing new connections to a public sewer can be screened out as having no likely significant effect. Please see the section 'What does this mean for development proposals involving connection to a public wastewater treatment works?'
What does this mean for agricultural developments?
New agricultural developments involving the production, storage, management and spreading of organic manures and slurries within a SAC river catchment have the potential to contribute towards the amount of nutrients entering a designated site.
The following types of agricultural development are not considered to have a likely significant effect on SAC features in relation to water quality impacts:
- Covering an existing yard
- Roofing for manure / slurry or silage storage that does not impact the existing store structure.
Agricultural developments must be fully compliant with current regulations for activities relevant to agricultural practices and should adhere to management good practice guidance, including the Code of good agricultural practice.
Read the Code of good agricultural practice on Gov.Wales
The following types of agricultural developments are considered to have a likely significant effect on riverine SAC features and should therefore undergo an Appropriate Assessment:
- Livestock housing - any proposals where there is a change in type of livestock or an increase in numbers
- Facilities and buildings for treatment of livestock manure, slurries and other organic manures e.g., anaerobic digestion or composting
- New or substantially altered manure / slurry store - all manure types including other 'organic manures' for example digestate or compost.
- Silage clamps and associated infrastructure to contain high nutrient content effluent
- Farm constructed wetlands (Read Constructed wetlands for improving water quality)
- Horticultural development, including packhouses and polytunnels.
- Livestock handling facilities
Where a new agricultural development is proposed that will lead to an increase in generation of organic manures and slurries, applicants should provide the Planning Authority with evidence to confirm that organic manures and slurries will only be applied to land at rates that meet soil and crop need. When manure or slurries are applied to land with no demonstrable benefit to the soil or crop growth or when they exceed the nutrient requirements of the crop, they are considered waste materials and environmental permitting regulations apply.
Read advice on using manures and slurries
Applicants should provide the Planning Authority with information showing:
- where the manures and/or slurries from the development will be spread to land
- where the manures and/or slurries from the development will be treated if being exported as a feedstock for anaerobic digestion
- how they will have control over the destination of the material for land spreading
- a manure management plan for the land area on which the manures, slurries or digestate will be spread, demonstrating that the holding has the capacity to receive the material and comply with regulations for spreading. The plan should include details of volumes of organic manures and slurries produced, how it will be transferred, stored and used. Read advice on manure and nutrient management plans.
- a contingency plan for the management and spreading of manures and slurries for use in circumstances when the manure management plan above cannot be applied (e.g., extreme, prolonged wet weather)
Farmers and landowners must also consider soil management measures in addition to effective nutrient management (as set out above) and should meet Cross Compliance rules if they apply for payments under the Basic Payments Scheme.
Download the Cross Compliance rules from the Welsh Government website
Maintaining good soil structure is critical to limit nutrient losses and maximise nutrient uptake by crops. There is a risk that nutrients may enter river systems through run-off during rainfall events.
Read advice on soil management to prevent nutrient or sediment run-off on the AHDB website
Nutrient or sediment run-off to a river or stream can cause pollution and is an offence under the Environmental Permitting Regulations.
What types of non-residential development lead to increases in nutrient discharges?
These include developments expected to serve a population from outside of an SAC catchment who are not already served by residential connections to existing public or private sewers discharging within the SAC river catchment. This includes, but is not limited to, self-service and serviced tourist accommodation such as hotels, guest houses, bed and breakfasts, self-catering holiday facilities, camping and caravan sites. There may be cases where planning applications for new commercial or industrial developments, such as conference facilities, large retail sites or major tourist attractions could result in the release of additional nutrients into the river system.
In such cases, further assessment is likely to be required to determine if the proposal will have an adverse effect on the integrity of the river SAC.
What does this mean for domestic extensions?
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.
What does this mean for development proposals involving connection to public wastewater treatment works?
For new developments proposing connections to a public sewer, 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 public sewer and proposed connection point
Planning Authorities should then consult with the sewerage undertaker to determine whether the environmental permit for the associated wastewater treatment works has been assessed against the revised nutrient targets set out in the conservation objectives for the river SAC.
NRW is undertaking a review of existing water company permits (with a dry weather flow, final effluent discharge of =>20m3/day) against revised water quality targets. This work is being done as an appropriate measure under Article 6(2) of the Habitats Directive. As such, Appropriate Assessments have not been produced in support of the Review.
Planning Authorities may access permit information via our public register or by contacting us at: sacriversenquiries@cyfoethnaturiolcymru.gov.uk
Where a wastewater treatment works permit has been reviewed against the revised water quality targets and, in some cases, varied accordingly, new developments connecting to the associated public sewer should still be subject to an HRA by the Planning Authority. While the nutrient impacts of new connections should be considered on a case-by-case basis, it is likely that a conclusion of no likely significant effect could be drawn in the context of water quality impacts where the sewerage undertaker confirms the following apply:
- there is capacity to treat additional wastewater from the proposed development within revised environmental permit limits (meaning both nutrient limits with immediate effective dates and for some permits, tighter nutrient limits with future effective dates), and
- the WwTW is currently operating in compliance with permit conditions or will be in advance of new connections being made, where permit conditions include those for flow, final effluent standards and flow passed forward (for works with storm tanks or direct storm overflow).
Although, it should be noted that the scope of an HRA may need to be wider than the scope of the permit review and consider other site characteristics, new information or changes in circumstances.
Where appropriate, Planning Authorities are advised to condition timing of development to correspond with delivery of future improvements at wastewater treatment works including those scheduled under AMP. Grampian conditions may be used but, as development specific mitigation, should be considered on a case-by-case basis at Appropriate Assessment. Where future improvements or enhancements are required to enable a treatment works to meet reviewed permit limits, conclusions of no likely significant effect or no adverse effect on site integrity can only be made if there is certainty at the time that the HRA is being carried out that these improvements proposed within the AMP will be implemented.
Where a wastewater treatment works has no nutrient limits conditioned on its permit, is not part of the current NRW Review of Permits programme and/or no improvements are being proposed under the AMP, we advise that the Planning Authority undertake an Appropriate Assessment of new connections to a public sewer taking into consideration the revised phosphorus targets for the river SAC and local water body targets for ammonia. It is likely that development proposals connecting to such a works will need to demonstrate phosphorus neutrality for a conclusion of no adverse effect on site integrity to be drawn.
The list of Welsh Government mitigation measures can be downloaded from the Welsh Government website
In water bodies meeting ammonia targets, the ammonia impacts of developments connecting to a public sewer will need to be assessed through Appropriate Assessment where the permit for the works does not have an ammonia limit. The assessment should determine whether the increase in wastewater will lead to an exceedance of local ammonia targets in the receiving watercourse at the point of discharge.
There is a presumption for all developments that 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 web page.
Can chemical pre-treatment be used to enable connection to a public sewer where phosphorus constraints apply?
Chemical pre-treatment to reduce phosphorus in wastewater discharging to a public sewer may adversely affect the hydraulic and biological performance of the wider sewer system and treatment works. In the first instance Planning Authorities / developers should seek advice from the water company for any such proposals.
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.
Read Planning policy Wales on the gov.wales website.
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 private sewage treatment system consisting of package 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 private package treatment plant is not feasible, should a septic tank system be considered.
With regards to feasibility, it is NRWs position that connection constraints associated with the standard of effluent quality that can be achieved at a wastewater treatment works, and/or the capacity of the SAC catchment to receive increased nutrient discharges and meet water quality targets is not a valid reason to justify use of a private sewage treatment system in a sewered area. Private sewage treatment systems are likely to require an environmental permit for a discharge activity unless they meet the criteria to register an exemption. We are unlikely to issue a permit for such systems if the proposal is within a sewered area.
Where private treatment systems can be justified, small discharges to ground (<2m3/day) via a suitable drainage field, built in accordance with criteria set out in this advice, should be prioritised over direct discharges to watercourses as they are considered unlikely to have a pathway for nutrients to enter the river environment and are unlikely to have a significant effect on an SAC. Larger discharges to ground will need to be subject to an Appropriate Assessment along with other forms of development involving private sewage treatment systems not addressed above.
For advice on cess pits, please refer to the section below on sludge disposal.
We encourage developers to use our environmental permitting pre-application advice service when considering private sewage treatment systems to identify and discuss any constraints that may apply. It is unlikely that permits authorising new discharges to surface water will be granted in SAC catchments failing to meet their phosphorus targets unless it can be demonstrated that other phosphorus reduction measures have been secured and nutrient neutrality achieved. Ammonia discharges will be assessed on a local impact basis as set out earlier in this advice.
Current legislation, the Environmental Permitting Regulations (England and Wales) 2016, allows some small, new discharges to ground and surface water to be exempt from the Environmental Permitting regime. These include discharges usually associated with small private drainage schemes. Where an operator has determined that their discharge meets the exemption criteria they must register their scheme as exempt from permitting. It is important to note that registering an exemption does not mean that a permit has been issued by NRW or that an assessment of impact on water quality has been undertaken. In addition, registration of an exempt discharge does not mean that planning consent for a development with a new private drainage system can be granted and as such activities which are exempt from the permitting regime may nevertheless need to be subject to HRA in considering the planning application.
We advise Planning Authorities to seek the following information in support of a planning application or Habitats Regulations 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 public 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.
The Planning Authority should also ensure that, where available, copies of any Natural Resources Wales environmental permit or registered exemptions to discharge to ground or to a watercourse are made available.
Where a new drainage field is proposed close to other known existing and proposed drainage fields, there is risk that the effectiveness of the drainage fields could be compromised. Many private drainage systems qualifying for an exemption from Environmental Permitting have not been registered with NRW and as such there may be limited data available on the location of existing drainage fields. In the absence of complete data, Planning Authorities are advised to use mapping/aerial photography to assess proximity to existing properties likely to have a private drainage system and consider whether further site investigation may be required. Poor operation of drainage fields can lead to increased nutrient discharges to SAC river systems. We therefore advise Planning Authorities to consider site conditions (such as proximity to adjacent drainage fields, soil type, depth to groundwater, distance to surface water features and SAC boundary etc.) to determine with certainty that existing and proposed drainage fields will operate effectively in the future and prevent nutrients from entering a river SAC. Planning Authorities may wish to refer to advice on groundwater risk assessments to inform any technical assessments.
Read Groundwater risk assessment for your environmental permit on Gov.uk.
Can additional wastewater be discharged to existing private sewage treatment systems?
Development proposals resulting in additional wastewater being discharged to an existing private treatment system are not likely to have a significant effect if:
- the existing discharge is to ground 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
- the design of the existing private sewage system (including the drainage field) has the capacity to effectively treat and discharge the additional wastewater and
- increases in effluent discharge to ground can be made where the discharge remains eligible for an existing exemption under the Environmental Permitting Regulations or can operate in compliance with conditions of an extant environmental permit.
Where increases in wastewater to an existing private sewage treatment system are being proposed in association with a development, Planning Authorities are advised to obtain a detailed design of the private drainage system (including an assessment of ground conditions in the drainage field) to demonstrate that it can accommodate increased flow and continue to operate effectively.
Will separator (compost) toilets increase nutrient discharges to SAC rivers?
Separator toilets, also known as compost toilets, are unlikely to lead to increases in nutrient discharges to the SAC river environment. Well-designed and maintained separator toilets can reduce water usage and provide material that is suitable for use as a fertiliser. The design of both permanently sited and portable separator toilets should separate the urine and sanitary waste from the solids. Permanent separator toilets are appropriate for remote, small scale, low use sites. Permanent sites with high use such as activity venues should seek to connect to a public sewer or install a permanent, private treatment system.
Any temporary or compost type toilet that does not separate solids and liquids is a cesspool and should have the resultant waste collected by a registered waste carrier for treatment at an appropriately permitted site and should not be applied to land.
Advice on temporary events and use of temporary toilet facilities
Planning Authorities should consider how temporary events may affect the ability of an SAC and its features to meet their conservation objectives and whether the potential impacts are strictly temporary. A short-term impact may have a long-term effect on a SAC - an assessment should therefore not be based on the duration of the temporary activity.
Sites with planning consent to hold frequent seasonal events or activities on a long-term basis should be considered permanent development. Such sites should use a long-term drainage solution consistent with Welsh Government guidance.
Read Planning Requirements for Private Sewerage in New Development on gov.wales.
This should include connection to a public sewer or installation of an appropriate private drainage system. Examples of this type of site include seasonal wedding venues, touring caravan parks and outdoor activity venues.
Temporary events including music or sporting festivals may benefit from permitted development rights. An event organiser should follow the process we set out in the Permitted Development section of this advice when considering the development planning implications of an event’s environmental impacts.
We advise Planning Authorities to obtain a drainage plan from organisers of temporary events seeking prior approval, setting out how wastewater will be collected, managed and disposed.
How should waste water from temporary facilities be disposed?
Chemical toilet waste from portable caravan/camping units should be discharged directly to a public sewer or to a sealed cesspool on site and removed by a licensed waste carrier. Chemical toilet waste should not be discharged to a private drainage system with package treatment plant or septic tank treatment.
Grey water (from wash basins, showers, kitchen facilities) must be discharged directly to a public sewer, an appropriately permitted private treatment system with capacity to receive the wastewater (e.g., package treatment plant or septic tank) or to a temporary sealed cesspool on site and removed by a licensed waste carrier.
All waste material from commercial chemical toilets should be removed from site by a licensed waste carrier and disposed at a permitted treatment facility.
Portable separator toilets may be used for temporary events but like commercial chemical toilets, all waste must be removed from site by a licenced waste carrier for treatment at a permitted facility. Liquids from portable commercial separator toilets/urinals must not be discharged directly to ground.
Permitted Development
The Habitats Regulations impose a condition on development proposals which comprise permitted development under a General Development Order, such that development likely to have a significant effect on a SAC must not commence until the Planning Authority has given written approval.
For such proposals, developers may first seek the opinion of NRW as to whether they are likely to have a significant effect on an SAC. If a conclusion of no likely significant effect is drawn, then NRWs opinion on the issue can be considered conclusive. Unless NRW rules out there being a likely significant effect, then developers must obtain prior approval to proceed with that development from the Planning Authority who must complete an Appropriate Assessment and consult further with NRW.
The use of land for caravans as a certified site will mostly be permitted development under the General Permitted Development Order 1995 (GDPO) and is therefore caught by the relevant provisions of the Habitats Regulations. NRW considers that there will be no likely significant effect where foul drainage arrangements are in place such that occupancy of the caravans / tents would not increase the amount of nutrients being discharged from the site, although such proposals will be assessed on a case-by-case basis.
Can phosphorus reduction technology be used in private sewage treatment systems?
Technologies to reduce phosphorus in effluent discharges from private sewage treatment systems are usually based on a chemical dosing technology. The use of chemical dosing systems in small, private treatment systems may not be able to deliver phosphorus reductions in the long term. Such systems require high standards of maintenance for them to operate effectively including management of the chemicals and dosing system, as well as regular desludging where dosing increases the amount of sludge deposited.
Many small, private treatment systems are not well maintained and failure to maintain a private system with chemical dosing system may lead to chemical contamination of river water, deterioration of effluent quality and increases in phosphorus discharges over time. Their use may also lead to breaches of permit conditions as well as being a risk to personal and environmental safety where handling and storage of chemical substances is involved. Chemical dosing systems are more suited to operation in large scale, public wastewater treatment works.
If phosphorus reduction technologies are proposed for a private system, developers applying for planning consent should provide sufficient information with their application for Planning Authorities to demonstrate with certainty that the proposed system can be installed and operated effectively in accordance with manufacturers specifications for the lifetime of the development. Supporting information should include: ·
- test performance certification issued by a recognised body demonstrating the effluent phosphorus standards that can be achieved by the proposed treatment system
- a method statement detailing how the sewage treatment plant and phosphorus reduction technology will be operated and maintained.
Note this information is in addition to the provision of manufacturers specifications, design information and drainage plans that should accompany any application.
Phosphorus reduction in private systems does not remove all the nutrient from effluent. Therefore, developers and Planning Authorities will need to consider the effect of residual phosphorus in effluent on a river SAC, as a pathway for impacts remains where discharges are to watercourses or discharges are to ground not meeting the criteria set out in this advice. Guidance on private system sludge is provided below.
Private treatment systems involving chemical dosing will require an environmental permit for the discharge activity. We recommend that developers proposing additional treatment to reduce phosphorus refer to our pre-application advice service prior to applying for an Environmental Permit. There is a charge for this service. Once constructed, the private treatment plant should be maintained by a suitably qualified contractor in accordance with the manufacturers requirements and comply with conditions of the environmental permit.
Apply for pre-application advice for environmental permits
How should the disposal of sludge from private wastewater treatment systems and portable toilets be considered in a Habitats Regulations Assessment?
In our opinion, with the current regulatory framework in place governing carriage, disposal and treatment of sewage sludge, Planning Authorities can reasonably conclude that the disposal of sludge from new, private sewage treatment systems or portable toilets is unlikely to have a significant effect on a river SAC.
Developments connecting to private drainage systems will lead to accumulation of sludge in the treatment unit and require regular desludging to operate effectively. In most cases, the waste removed from a private treatment system tank will include a combination of the liquid fraction, treated waste and untreated sewage. For the purposes of this advice, the combined waste will be given the generic term of private system ‘sludge’. Sludge is also collected from portable toilets operated by commercial providers for temporary events. Sludge from these sources should be taken via a registered waste carrier to an appropriate public wastewater plant for further treatment. After being deposited at the public wastewater plant, treated sewage sludge in Wales follows a pathway with resultant material spread to land. The process of treatment at the public works, anaerobic digestion and spreading to land is governed by a range of environmental regulations, an assurance scheme, and codes of practice. Controls are set out within this governance framework to reduce the risk of nutrients, from entering the river environment where compliant land spreading operation is undertaken.
For private drainage systems i.e., septic tanks and package treatment plants without phosphorus reduction technologies, the phosphorus in effluent presents the greatest risk to the river environment. We advise in earlier sections of this guidance how the impacts of effluent discharges to ground and watercourses should be considered in an HRA. The sludge only retains a small proportion of total phosphorus.
Where phosphorus reduction technology is installed in private sewage treatment systems, it alters the balance of phosphorus distribution between effluent and sludge, with increased accumulation of sludge and most of the phosphorus being retained in-tank in this material. The risks associated with the use of phosphorus reduction technology in private systems are detailed above. As a result of the altered balance of phosphorus distribution between effluent and sludge, such systems will lead to an increase in phosphorus rich sludge being taken to public works for treatment. However, key water company infrastructure currently has capacity and the regulatory framework to receive this material.
Sealed cesspits are not a sustainable drainage solution and proposals for their use should be regulated in accordance with Welsh Government Circular 008/2018. Planning Authorities are advised to carry out an Appropriate Assessment for any proposals involving use of sealed cesspits as a likely significant effect from disposal and treatment of waste from these systems cannot be ruled out due to their retention of all wastewater from a development.
Download the Welsh Government Circular 008/2018 from the Welsh Government website
Avoidance and mitigation measures
As a result of the 'People over Wind' ruling (case C-323/17), mitigation 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 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.
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 nutrient loading if:
- the associated developments or activities are not a source of nutrients or there are no pathways for additional nutrients to enter the river environment or
- Allocations requiring connection to a public sewer can meet the screening criteria set out in the section What does this mean for development proposals involving connection to public wastewater treatment works?
Any LDP policies 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 advice.
Allocations for developments with proposed connection to a mains wastewater treatment works that do not meet the screening criteria and have the potential to increase nutrient loading, should be subject to an Appropriate Assessment in accordance with advice set out earlier in this document.
Allocations where there is no capacity for additional wastewater
Where a development is proposed with connection to a public sewer, but the associated wastewater treatment works has insufficient capacity to accommodate additional nutrients from new connections or no improvements to increase treatment capacity of nutrients is planned within the AMP programme, the Planning Authority should undertake an Appropriate Assessment of the proposals. The Appropriate
Assessment should consider any other mitigation, nutrient neutrality, or avoidance measures.
Case law
As a result of the Court of Justice of the European Union (CJEU), “Dutch nitrogen case” (Joined Cases C-293/17 and C-294/17), the scope for authorising new development that will lead to additional phosphorus loading is necessarily 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.
In addition, the Wyatt case (R (Brook Avenue RAD) v Fareham BC) clarified that the duty under the Habitats Directive to take appropriate steps to avoid the deterioration of SACs does not preclude a nutrient neutrality approach to consenting development which would otherwise give rise to further nutrient loading in European sites already in unfavourable condition.
The Dutch, Compton and Wyatt cases related to nitrogen, but NRW considers that the principles should apply to other nutrients, including phosphorus.
Whilst the nature of development will depend on the facts of each case, Planning Authorities should refer to the relevant legislation and principles outlined in case law when assessing the nutrient impacts of proposed developments as part of the Habitats Regulations Assessment process.