PAS Guide to better Sustainability Appraisal

Section 19 of the Planning and Compulsory Purchase Act 2004 requires a local planning authority to carry out a sustainability appraisal of the proposals in a plan during its preparation. The Environmental Assessment of Plans and Programmes Regulations 2004 (commonly referred to as the ‘Strategic Environmental Assessment' or 'SEA' Regulations) require a strategic environmental assessment (SEA) of any plan or programme that sets the framework for future development consent of projects and is likely to have a significant effect on the environment.  In practice, the sustainability appraisal should incorporate the requirements of the SEA Regulations as one and the same process. The SEA Regulations set the requirement to identify, describe and evaluate the likely significant effects on the environment of implementing the plan and reasonable alternatives, taking into account the objectives and the geographical scope of the plan or programme. The SEA Regulations transpose the European SEA Directive into English law. It is often the Directive rather than the SEA Regulations that is referred to by lawyers. Although the UK is no longer subject to the European SEA Directive’s requirements, it is the basis for pre-2021 caselaw. In this guide, we will mainly refer to Sustainability Appraisal or SA, but users should assume this encompasses SEA.

Failure to carry out the sustainability appraisal process properly can expose the local plan to legal challenge. PAS worked with No.5 Chambers in 2014 to produce legal updates on key areas of plan making including Sustainability Appraisal. These slides from Landmark Chambers summarise legal judgements on SEA in Local Plan making to June 2018. Whilst dated, they provide useful background on legal issues with SEA/SA. It’s important to recognise that whilst legal challenge is a risk, it is rare and your response to this risk should be pragmatic and proportionate. Fear of challenge drives much of the bad practice in SA. The tips in this guide aim to support a pragmatic and proportionate approach.

The most common reason for challenge to SA is that reasonable alternatives have not been properly considered. The SEA Regulations state that within the Environmental Report ‘reasonable alternatives taking into account the objectives and the geographical scope of the plan or programme, are identified, described and evaluated’. The word ‘reasonable’ is key here: an alternative is reasonable if it fits with the plan’s objectives and geographical scope. Tips on the consideration of reasonable alternatives in a proportionate way are outlined below. 

A further reason for challenge is that consultation was not sufficient. The SEA Regulations set out consultation requirements: you need to consult consultees and the public properly on the environmental report, alongside the draft plan. In 2020,  Harrogate Local Plan was subject to a legal challenge on three grounds. The only one that was upheld was that “the full council did not take into account the final SEA material and consultation responses, or a summary and analysis thereof, when they resolved to adopt the local plan.” Good practice for making sure SA is integrated into your Local Plan process and transparency on how you have taken account of SA/SEA in preparing your plan is outlined below.

Government published the Planning practice guidance on Strategic environmental assessment and sustainability appraisal in 2015 accompanied by a SEA Regulations checklist for Local and Neighbourhood plans and a Sustainability appraisal process flowchart. The PPG provides some guidance on assessing alternatives and identifying likely significant effects, plus it explains the difference between SA/SEA and Environmental Impact Assessment (EIA), which is applied at the project level. A more general guide, published in 2005, on applying the Strategic Environmental Assessment Directive provides further detail on developing and assessing alternatives (Appendix 6) and forming a judgement on whether or not a predicted effect will be environmentally significant (Section B4).

The Royal Town Planning Institute (RTPI) published practice advice on SEA/SA for land use plans in 2018.

The PAS Local Plan Route Mapper and accompanying Evidence for Plan Making note provides guidance on how to integrate sustainability appraisal into Local Plan preparation and review. This guide supplements the route mapper to provide more focused good practice for better sustainability appraisal and is based on the PAS Can we make Sustainability Appraisal more sustainable? blog of July 2024. One reason for producing this guide was to provide an up-to-date resource for local authorities with a focus on strategic assessment of Local Plans.

The Levelling Up and Regeneration Act (LURA) includes provisions for a new form of environmental assessment known as Environmental Outcome Reports (EOR). The intention is that Environmental Outcome Reports will replace the existing system of Sustainability Appraisals (SA), Strategic Environmental Assessments (SEA) and Environmental Impact Assessments (EIA) and make the process simpler, using more consistent data and focussed on measuring environmental effects against improving environmental outcomes. PAS completed a piece of work on Barriers and Challenges for Environmental Assessment in 2022 and ran a webinar on the Government's consultation on EORs in 2023.

Developing your SA in house facilitates an iterative approach that fits with plan-making and means that the team preparing the plan will have a good understanding of the SA process, enabling them to bake in the sustainability implications early in the process. Local knowledge is seen as invaluable and helps in producing a locally-focused assessment. Doing the SA in-house also allows for an accessible, short summary to be produced that brings together the story of the Local Plan and the SA as one - written communication skills are key to producing a good SA. Most of the LPA officers we spoke to that had experience of doing SA in-house felt this approach saves time and money as compared to contracting an external consultant, but it is difficult to demonstrate whether this is actually the case, as the costs are not comparable.

This approach relies on the local authority employing someone that has the appropriate skills and expertise or enabling an existing member of staff to develop these. Central Lincolnshire Local Plan team are lucky enough to have their own SA/SEA expert in-house, who they also loan out to other local authorities preparing their plans. It’s important to factor in the need to invest in appropriate training and personal development for in-house SA officers, including going to seminars and learning from others. You also need to make sure your process is robust and make sure you don’t get too much scope creep, which can create extra work. 

Some LPAs are concerned about objectivity when doing the SA wholly in-house - the key thing here is to make sure that whoever is doing your SA can ‘see the wood for the trees’ and has the confidence to respond to unreasonable challenges and requests to avoid a risk averse approach. Mid Sussex District Council contracted an external consultant to do an audit of their SA before Reg 19 of their Local Plan to make sure it was robust for examination (though this approach allows little opportunity for revision if there were issues with the assessment early on). Other LPAs made sure to house SA officer(s) outside the team directly writing policies or developing the draft plan.

Consultancies that specialise in SA/SEA can use their experience and expertise to ensure you meet all the legal requirements and offer an independent, third-party, objective view. They bring knowledge and experience from appraising other plans and an outsider’s perspective, all of which can be a bonus in terms of additional insight and advice and in challenging key assumptions. They will usually have a tried-and-tested approach to SA.

It can, however, be harder to make sure the outcomes of the assessment are integrated into the Local Plan than when SA is done in-house, so you will want to make sure your contract allows for this and factors in consideration of your locality and what is special/different about it. Good practice is to agree with consultants that they will be involved in setting the SA Framework and options development and to define scope of works in line with the Local Plan. It is also good practice to keep a record of how you have taken account of the SA findings in your plan (see Be transparent and tell the story), which will help address the integration issue too. It can be challenging managing consultants alongside their other commitments, especially through the time-tabling vagaries of local plan-making. You will need to be realistic about the costs - a good SA takes time and you should consider tenders carefully to make sure you choose the right consultant for you, not just the cheapest. You may want to look at other examples of the consultancy’s work to judge whether the approach they take will work for you. Manchester City Council chose to contract the external consultant for the SA of their Local Plan Review on the basis of their proposed approach of a more narrative based analysis of the plan, which the MCC team felt would result in a more accessible SA product.

A half-way house between doing the SA in-house and using an external consultant can be to use a ‘critical friend’ approach: locating external expertise in-house to help ensure the sustainability appraisal process is as integrated with the plan making process as possible. Best practice is to involve the consultant from the start of preparation of the plan, rather than, for example, doing a review of a SA produced in-house or externally at the end: there is very little scope for rectifying mistakes at the end of the plan-making process. Having used an external consultant for their most recent Local Plan, South Downs National Park Authority Local Plan team are using a planning consultant that has done a lot of work for the authority previously and understands their issues well for the SA of their Local Plan review. This allows for some integration into the Local Plan process and the local knowledge that is so valuable, but also gives the SA a bit of distance and independence from the policy writing and site selection process, which the team feels gives them the best of both worlds. They also feel that it offers them good value for money. North Yorkshire Council and Wealden District Council are also using a ‘critical friend’ approach alongside their in-house expert to prepare the SA for their new Local Plan.

Your SA scoping will include identifying the key sustainability issues for the area covered by the plan and it is good practice to use these to set a focused list of appropriate objectives. You can use the issues set out in Appendix 2 of the SEA Regulations as a basis for your list and may also want to add to these where particular issues are of relevance in your plan area. Remember your previous SA will have set a Framework and listed relevant strategies and plans, so you can go back to that rather than starting from scratch. 

You can scope out objectives, but there is a careful balance to be made between having too many objectives and missing out key issues that you should be assessing. Too many objectives can result in the assessment multiplying to unmanageable levels and the production of long unwieldy reports full of tables where the key messages are lost. You may also want to combine more than one issue into a single objective to help ensure the list is manageable. Remember that the consultation bodies will want to see sustainability objectives relevant to their areas of interest included, but you will also want to keep things relevant and proportionate. Be clear on why the objectives you have chosen are the right ones for your plan and local context (see Be transparent and tell the story well below). Remember you can change the objectives after scoping as long as you give clear reasons for why you have done this. The SA for the Purbeck Local Plan used a short, focused set of eight objectives with three to four key decision-aiding questions aligned to each.

In our view, it is helpful to have draft plan objectives at the point when you are doing the SA scoping, as it can ease assessment of the plan objectives and identification of reasonable alternatives. An approach some local authorities have taken is to use the same objectives for the plan as for the SA on the basis that as the plan’s overall aim is to deliver sustainable development, its objectives should reflect the key sustainable issues for the area. This has been done successfully for a number of adopted Local Plan SAs, including Central Lincolnshire and Peterborough, and meant that they could miss out the stage of comparing objectives to each other, saving time and paperwork. For this approach, it’s important to ensure the plan objectives will enable you to undertake a systematic assessment (see also below on choosing objectives that are not policy-led). Timing can make aligning SA objectives with your plan tricky, as you may be scoping to set the SA objectives before you have decided the plan objectives.

Wording is important, for example, 'minimise' can have very different connotations to 'reduce'. Remember you will be using these objectives to assess alternative growth options, policies and (most likely) site allocations, so make sure they are flexible enough to allow this and they enable you to assess likely significant effects (not every eventuality). You will need to make sure you can actually measure and assess against the objectives you have chosen. In good practice, objectives reflect genuine sustainability aims and are not policy-led or influenced by pre-defined targets. For example, Erewash Borough Council knew they would have to allocate some sites in the Green Belt in their Local Plan review, so decided that, as the location of Green Belt is a policy decision, it wasn’t appropriate to include avoidance of impacts on Green Belt as a SA objective. 

You can use questions or indicators to do the assessment against each objective. A key tip is to make sure your list of questions or indicators is manageable: you need to assess positive and negative effects, cumulative and in-combination impacts, but only ‘significant’ effects need to be considered. As for setting a list of objectives, you need to make sure you can actually measure the indicators and/or answer the questions you have set: you can use scores or commentaries to do this. Quantitative scores, like distance criteria, enable quick, transparent and consistent assessment. Commentaries are often preferred where there is not a direct measure for the criterion, as they can make it easier to weight objectives against each other to reach conclusions and are likely be less open to challenge than a subjective score. Surrey County Council are using an impact-pathway based approach to assess their Minerals and Waste Local Plan with three key pathways identified for each of the 12 objectives in their SA/SEA Framework and the Scoping Report includes a clear, accessible overview of the Framework as a table (Table 3-1) and a reporting graphic (Figure 3-1). 

If you think early about what you want the plan to do and where SA fits in, it will save time and make for better plan-making. The SEA guidance and PPG make it clear that SA/SEA should be iterative and proportionate to the plan under consideration and the stage that is at. The SA should reflect the plan and the available evidence in terms of the level of detail. So, it’s likely that SA of a Local Plan Review will be lighter touch than what is required for a new Local Plan. For example, you could filter out and just assess those policies that are changing, though you will need to consider the impacts of the plan as a whole, including any saved policies. This is the approach being taken by South Kesteven District Council and South Downs National Park Authority for their Local Plan Review SAs, with the latter focusing on cross-cutting themes and how the plan is holistically addressing issues, as well as any updated policies. See also Identify reasonable alternatives early on.

It’s worth taking into account the level of detail you’re going into at Regulation 18 stage and making sure you don’t over-do any assessment at this stage if your consultation is light touch, e.g. you might just need to publish the scoping report alongside the consultation, but it is good practice to start the SA process at this stage whatever level of detail you are going into. You should also consider carefully how much assessment you need to do if your plan goes through modifications. Where there are multiple modifications stages, there is a risk that the amount of assessment can quickly multiply resulting in potentially lots of unnecessary, time consuming assessment and long reports. Consider whether any changes alter the effects of the plan or its reasonable alternatives - only if they do, do you need to re-assess. 

The Sustainability Appraisal Report should show how the SA has informed the local plan in a user-friendly way. The story behind the plan's preparation and the role of the sustainability appraisal in developing, refining and choosing between options (including the reasoning behind your choice of reasonable alternatives) should be articulated. This helps Planning Inspectors, members of the public, developers and others to engage and understand the process. One way to ensure this is to include formal recommendations for the local plan within the Sustainability Appraisal Report. This response can be recorded together with any subsequent amendments to the emerging plan, as a simple table with what you've done with hyperlinks to relevant documents, which will help explain why the proposed plan is the best solution to the needs and demands of the locality. It is also good practice to keep a log of plan changes. Telling the story well should help head off any challenges to how you have undertaken the SA and demonstrate that you have met due process. 

Remember that you do not need to publish everything, as long as you have explained your approach clearly - think about what needs to be in the report and what is just your ‘workings out’ (which you can keep to refer to in due course if needed, but do not need to publish). Consider how to present information in a user-friendly format, for example, a diagram, flow chart or table with an explanatory paragraph rather than reams of matrices or text. Wealden District Council’s SA Scoping Report (Update) has an engaging structure providing a clear outline of baseline data with key messages pulled out for each topic area and diagrams and charts to summarise, plus an explanation of the SA Methodology and Framework.

An Environmental Impact Assessment (EIA) for a development proposal may suggest specific mitigation measures, such as construction of a noise barrier, but a sustainability appraisal is more likely to suggest changes in policy wording or emphasis. For this reason, mitigation measures may emerge throughout the Sustainability Appraisal process as the options and draft policies are developed and you will need torecord how you have taken steps to mitigate adverse effects (and maximise positive ones).

The SA Report non-technical summary can be a good way to outline the ‘story’ of the SA and the Local Plan. Good practice is to:

• Explain what you have looked at and why it’s important, as well as what was considered unimportant and the reasons why.
• Use text rather than tables to explain the assessment of impacts and how these were addressed
• Make sure there is no need to refer to other documents/appendices to see the ‘story’
• Provide short summaries of key issues.

Purbeck Local Plan went through a significant number of iterations before being adopted in 2024. The Sustainability Appraisal New Homes for Purbeck, Non-Technical Summary (2018) provides a clear summary of the story of SA and its integration into the Local Plan to that point taking a mainly narrative approach. The SA Non-Technical Summaries for the Uttlesford Local Plan Reg 19 consultation and Surrey Heath Local Plan Reg 19 consultation (both produced by AECOM) are both 8-page documents setting out the SA Framework, approach to considering reasonable alternatives and SA findings at this stage. The Surrey Heath document includes maps of alternative growth scenarios.

Sustainability appraisal is a tool to aid the selection of the most appropriate option and is not the actual decision-making mechanism. It is only effects likely to be significant that need to be assessed. Therefore you don’t need to assess options or policies that are not likely to have any significant effects. The 2005 SEA guide provides guidance on forming a judgement on whether an effect will be significant (Section B4).

Evidence gathering is hugely resource intensive and most LPAs don’t have enough money to get all the evidence they would like to inform their Local Plan. Bear in mind that the SA is part of your evidence base and that you can link through to other evidence base studies and assessment, such as transport, landscape flood risk and biodiversity net gain, without needing to repeat what they cover. If the relevant study isn’t ready yet, you can refer to the forthcoming assessment, rather than duplicating work. You can also use your previous SA to inform how you do your new one. See PAS's Evidence for Plan Making: A focus upon proportionality for more guidance on preparing your evidence base in an efficient, focused way. PAS can also offer bespoke support on preparing your Local Plan Evidence Base.

Where the SA is being done in-house (or at least the assessment of policies is), many LPAs use policy officers to appraise individual policies as they write them, so they can adapt the policy to meet the outcomes of assessment as they go along. This approach can save on resources, but you will need to make sure you follow the SA process and capture what changes have been made as a result of SA to tell the story. Remember you only need to assess policies with likely significant effects and that the SA requirement is to assess the plan as a whole, i.e. there is no legal requirement to assess every policy, and the combined effect of policies will be important. See also Considering reasonable alternatives.

You need to consult consultees and the public properly, as you do on the draft plan. As a minimum, consultation should be undertaken on: the scope and the sustainability appraisal report at Reg 19 stage. It is also best practice to consult on sustainability appraisal during the plan preparation process, for example, through the production of an interim Sustainability Report and through other means such as workshops and working groups. Ideally consultation on the Sustainability Appraisal can be done alongside other engagement work, for example, through workshops to identify sustainability issues at the scoping stage or events that debate the effects of options. This will help to ensure that views of stakeholders can be taken into account during the appraisal and facilitate an open and transparent assessment. Plan for consultation on the plan and SA at the outset of plan preparation, as well as how you will deal with representations - bear in mind that respondees may comment on the SA within their wider Local Plan response, so you will need to have a way to glean these comments - as well as how to present representations in a transparent, concise way.

If a new option or alternatives are introduced after consultation on the publication plan and the supporting Sustainability Appraisal Report, another round of consultation may be needed. The central requirement is to publish an SA Report for consultation alongside a true draft plan that presents an assessment of the plan and reasonable alternatives in order to inform the consultation and subsequent plan finalisation.

You may also wish to consider opportunities to integrate the sustainability appraisal with other types of assessments where possible. This might include health impact assessment or equalities impact assessment. This can avoid duplication of effort, save time and make the process more effective. However the documents do tend to be very long! Examples include the London Plan Integrated Impact Assessment and Greater Manchester’s Places for Everyone Integrated Assessment.

SEA/SA practitioners recommend integrating SA into your consideration of alternative growth scenarios/spatial strategies as the best way to look at reasonable alternatives to the plan. SA can be a key tool to allow you to choose the best spatial strategy in an objective way, increase transparency and integrate the SA and plan. SA is about assessing the likely significant effects of the plan and reasonable alternatives, so appraising the overall strategy and its alternatives is the best way to make sure you are doing this properly. You can use alternative key diagrams from your Local Plan as a basis for this. It will help you demonstrate how your spatial strategy has been chosen and why it is the best of the options presented in terms of delivering sustainable development and that the preferred strategy is ‘justified’ - a key aspect that Inspectors will look at. It should also make assessment of site allocations simpler and more efficient. Surrey Heath and Uttlesford both provide examples of this approach.

Reasonable alternatives should be real options that would be likely to be chosen. Consider alternatives which would secure the objectives of the plan proposed within the geographical area of the plan and don’t include options that cannot be delivered; reasons do not need to be given for rejecting obvious non-starters. It is not helpful to present hundreds of options as reasonable alternatives and it’s likely you’ll only have ten or fewer real alternatives. Where there are no or few options, explain why in the sustainability appraisal, as there is a legal requirement to assess alternatives. Sometimes this will be obvious - for example, a minerals plan may have few if any options given that minerals can only be worked where they exist. The rationale for the options considered and the reasons for the selection or rejection of each alternative, referring to the evidence, should be included in the SA Report. It’s not legitimate to select alternatives which have obviously more significant adverse effects than the plan or programme as proposed in a bid to promote the latter. 

Alternative objectives do not have to be assessed; the focus of SEA is alternative ways of meeting those objectives (this was confirmed by Heard v. Broadland DC [2012] Env LR 23 referenced here: Slide 1 (landmarkchambers.co.uk)). 

It is not necessary to keep open all options for the same level of detailed examination at all stages but, at each stage, the preferred option and the alternatives under consideration must be assessed to the same level of detail. This may include reappraising any options that are changed or are a hybrid of more than one option, where these have been incorporated in the plan, as well as considering alternatives for any modifications (even if they are late in the Local Plan process).The selected options which are in the published local plan need to be included in the SA Report. Alternatives can be sifted out as you go along and do not have to be reassessed at later stages, but reasons for sifting out need to be included in the final SA Report (readers should not have to go back through previous reports). 

See Be transparent and tell the story above.

It’s likely you’ll have at least some site attributes that will rule out sites completely, for example, flood risk. If you check for these first, it means you only need to do a full assessment on a smaller number of sites and might be able to leave these assessment criteria out of the SA completely. Applying strict criteria for discounting sites at the earliest possible opportunity means that fewer sites reach the assessment stage saving lots of time and reporting. Dorset Council have discounted sites that are beyond a distance from certain facilities (such as health, shopping and public transport) or within close proximity to (or within) various environmental designations before any SA of the sites. 

Both Peterborough CC and South Kesteven DC have effectively integrated site assessment and SA to avoid re-assessing the same issues twice as part of the site allocations process. Make sure you capture the reasons why you have ruled out any sites as part of telling the story (see above). You could also consider engaging with developers on the SA of site allocations alongside the SHLAA (Strategic Housing Land Availability Assessment).

One way to do an initial filter of sites and to make any distance-based criteria assessment much easier is via an automated/digital Geographical Information System (GIS)-based approach. This might be done for the SHLAA or equivalent, but still feeds into the SA. Peterborough City Council have used this to good effect in the Strategic Housing, Economic Land Availability Assessment (SHELAA) for their Local Plan Review, which then fed into their SA. They reckon it saved around three weeks of work: sites were submitted directly onto the Hawkeye (ESRI ArcGIS) system through their call for sites, which also helped. Though they highlighted that site assessment can’t be completely automated and that local knowledge to do a check-over is needed to make sure things haven’t been missed, plus there will still be a need to consult with internal and external experts and do site visits.

If you don’t have the relevant systems, another way to reduce site assessment work that could be done automatically might be to get a consultancy to do this aspect for you, as South Kesteven DC have done for the SA of their Regulation 18 Local Plan Review. 

Choose your criteria based on your reasoning for doing the assessment, remembering you only need to assess likely significant effects. See also Decide how you will assess against the objectives.

Data and evidence from monitoring can be really useful for SA preparation, but many LPAs find that they are not monitoring the right indicators, so have to go and get further information to do their baseline assessment. It’s worth thinking about the indicators you need to measure for the SA in advance. This will also feed into any future Local Plan review: doing the AMR usually assists with policy writing. If EORs do come forward, sorting this out now will also help transition to a new assessment system, as a key premise of EORs is to monitor outcomes.

Think about how you will measure indicators and whether you actually have the means to track them over time. It is good practice for indicators to be place-based, but it is not always easy to find indicators that are measured regularly at a local authority level. The South Downs National Park Authority and the Greater London Authority have locally specific indicators and link monitoring back into development management. In London, monitoring is helped by the Planning London Datahub, but most other places don’t have anything like this, so are either looking at DM officers recording key information when planning permissions are granted or collating information against indicators afterwards.