AGT1 Supplementary Planning Document

5 - Delivering the Place

5.1 Overall Approach to Development & Infrastructure Phasing

Development of the proposals at AGT1 are expected to take place over at least 8 years and will be likely to include several different house builders with some completions having already taken place. It is therefore recognised that flexibility needs to be retained in setting out proposed phasing and sequencing in order that the development can respond to changing circumstances over time, including changes to planning policy and market conditions.

The overall approach taken towards phasing and infrastructure delivery in this Supplementary Planning Document is to seek to ensure that each phase of development is as self-sufficient as possible whilst delivering necessary strategic elements of infrastructure in a timely manner and not prejudicing the ability of the following phases to do the same. Proposals to bring forward later planned phases sooner than proposed will be likely to be acceptable provided they do not undermine delivery elsewhere within the overall site, the provision of supporting infrastructure and mitigation of the impacts of the development because of early delivery.

In considering the approach to phasing, as well as land ownership / land promoter interest, how the supporting infrastructure specified in this Supplementary Planning Document for the specific number of units proposed in any application will be secured has been considered.

Infrastructure should be provided in a timely way and with certainty to reduce / mitigate the impact of the development. A coherent and coordinated approach to residential and infrastructure delivery, construction management and development phasing will be undertaken to ensure that the overall policy aspirations are met and to avoid the creation of parcels of land or pockets of development that are isolated from each other.

The anticipated time frame/phasing for the residential elements of the site is indicated in the table below.

Critically the pace of delivery will not only relate to house builder take up, but also facilitating infrastructure delivery and how quickly demand for new homes is developed as the provision of an attractive, sustainable, and desirable place to live is formed. The expected completion figures assume two or more house builders on site at any one time, with the build out of the site to be undertaken by 2033, the end of the life of the Vale of Aylesbury Local Plan.

Expected Trajectory from Appendix A of the Vale of Aylesbury Local Plan

The ultimate level of development delivered in South Aylesbury will be based on the approach set out previously in this SPD taking account of the adjacent settlement character and identity whilst responding positively to the best characteristics of the surrounding area. The figures below breakdown the gross area of the site and assesses ANGSt compliant green infrastructure requirements together with other infrastructure benefits that will be provided within AGT1, to provide a net area for potential development for new residential dwellings.

Areas of Development and Infrastructure within AGT1

5.2 Infrastructure Delivery & Phasing

Infrastructure Requirements

The delivery of infrastructure at AGT1 is to be provided in a timely and viable way to ensure that the impact of the development is reduced / mitigated against. Given the scale of the site, its location and subdivision by the London Marylebone to Aylesbury Vale Parkway railway line and the South- East Aylesbury Link Road, once constructed, there is a need to balance certainty of delivery of key infrastructure elements with the need to maintain flexibility over delivery.

The sequencing of development and provision of supporting infrastructure set out in this Supplementary Planning Document has been structured to provide the appropriate flexibility over where and when development takes place. The key infrastructure requirements are noted in the following table and have been derived from the Councils Infrastructure Development Plan Document (Draft September 2017) and the Vale of Aylesbury Local Plan. This table only includes the key infrastructure requirements where coordination of overall delivery is most required. For each element, it identifies the anticipated phase of development and any identified trigger points.

The indicative phasing plan below seeks to show the areas of the AGT1 development (housing and infrastructure) that will be brought forward during each of the short, medium and longer term timeframes described in the earlier housing delivery phasing table.

In compiling a list of infrastructure in relation to this allocation, the Council has had regard to the infrastructure tests set out in Section 122(2) of the Community Infrastructure Levy regulations which state that requests must be:

• Necessary to make the development acceptable in planning terms;
• Directly related to the development; and
• Fair and reasonably related in scale and kind of development

At the time of writing, a Community Infrastructure Levy (CIL) charging schedule is not in place or being prepared for the area within which AGT1 sits (the former Aylesbury Vale District Council area). Accordingly, developers will be required to make Section 106 contributions to fund specific items of infrastructure and services, where required, for the development.

Indicative Phasing Plan

Indicative Delivery Timescales: Short Term = Year 2024 - 2027 / Medium term = Year 2027 - 2029 / Long Term = Year 2029 - 2030

Note:

• Some triggers are expressed as ' before no more than a number of dwellings '. Breaching either of these limits will trigger the requirement to deliver the infrastructure in question.
• The indicative costings were formed using an independent costing consultancy who undertook a costing exercise using current (2021/2022) build cost data and with input from Buckinghamshire Council as appropriate.

Indicative Delivery Timescales: Short Term = Year 2024 - 2027 / Medium term = Year 2027 - 2029 / Long Term = Year 2029 - 2030

Note:

• The indicative costings were formed using an independent costing consultancy who undertook a costing exercise using current (2021/2022) build cost data and with input from Buckinghamshire Council as appropriate.

Apportionment

On the basis that more than one planning application will come forward for development within D-AGT1, an apportionment mechanism is required. This approach is consistent with the approach taken by the Council in other locations in Buckinghamshire where there are multiple landowners within a strategic development.

The preferred method of calculating apportionment is by Net Developable Area held by each landowner or developer. The detailed mechanisms for delivery, the exact costings and permutations for different areas coming forward at different times will be considered at the planning application stage. The Council, working with the landowners/developers, will produce an Infrastructure Delivery Framework. The Infrastructure Delivery Framework will be worked upon as applications are submitted and evolve, and will be a living document to reflect the latest position and more thorough analysis that accompanies planning applications.

The Infrastructure Delivery Framework would not be a binding legal document but it would set out definitive expectations of what would be contained within the legally binding commitments in each application s106 agreement. This will enable the Council to ensure that infrastructure will be costed and delivered in a timely and holistic manner. A separate memorandum of understanding document between the Consortium members would also be produced which will be submitted to the Council as additional assurance (potentially as an additional application document when each application comes forward). The Memorandum would provide a clear basis for the Council to impose lawful planning obligations and conditions to secure the relevant infrastructure in a planned holistic manner, in accordance with this document and Infrastructure Development Framework.

Highways Improvements

Highway modelling work is being undertaken to consider the proposed access locations; trip generation methodology and modelling scenarios in relation to the development of AGT1. This uses existing data together with predicted data estimates of future traffic to calculate the capacity of infrastructure and thus the need for improvements to highway infrastructure. These improvements will be detailed within the infrastructure agreement made between the individual landowners and legally secured through the section 106 agreement and planning conditions for each individual application.

Delivery

The delivery of AGT1 will take place over several years, with the main development expected to take between 2024 to 2030. Development is likely to come forward via the submission of different planning applications, either in outline or detailed form, for individual phases based on the subdivision of the site into smaller parcels.

Subject to the requirement for delivery of necessary infrastructure in relation to the trajectory of development and the location of the application area, all planning applications submitted will need to consider the delivery of appropriate infrastructure required to either make the application development acceptable and / or the development of the wider AGT1 site acceptable. Thus, ensuring that infrastructure is delivered in a timely way to reduce the impact of the development and to ensure that residents have access to the necessary amenities.

Viability and Deliverability

Key to a successful development will be the delivery of a high quality and sustainable place in which to live, including the provision of appropriate infrastructure at the right time. Co-ordination between the Council, landowners / developers and key stakeholders will be key to this.

Given the long timescale for delivery of South Aylesbury the continued viability of the site to ensure its continued long-term delivery is of paramount importance. It may therefore be appropriate to reconsider the viability of proposals at later stages. This may mean that the level and / or timing of affordable housing provision required or the timing of provision of elements of infrastructure as set out in this Supplementary Planning Document may need to be revisited.

Where landowners / developers wish to consider scheme viability, which is likely to be when planning applications are submitted, the Council will require an open book approach to be taken so that the outcomes and implications of viability testing at application stage can be carefully evaluated by the Council in light of the aspirations and requirements set out in this Supplementary Planning Document.

5.3 Infrastructure Delivery Framework

In terms of the mechanisms for securing the timely and comprehensive delivery of infrastructure at AGT1, the Council's preferred approach would be for there to be a single planning application and accompanying S106 legal agreement to cover the whole of the allocation area. However, it is recognised that circumstances may prevail where there are a number of related planning applications and s106 agreements that come forward. In this scenario, it is important that this SPD provides a basis for setting out how those planning applications can demonstrate:

• that policy compliant development can still be achieved;
• how the separate developments will accept their share of the costs;
• how the approach will provide certainty over the delivery of full package of the necessary infrastructure while overcoming issues of phasing; and
• how delivery will be achieved.

This approach is consistent with the approach taken by the Council in other locations in Buckinghamshire where there are multiple landowners within a strategic development.

To respond to the above, in addition to the provisions set out elsewhere in this SPD, delivery of the infrastructure referred to in this Supplementary Planning Document will be guided by a detailed Infrastructure Delivery Framework (IDF).

The IDF, once endorsed by the Council, will expand upon the key delivery principles and infrastructure items, guided by those listed within this Supplementary Planning Document. Importantly, it will also set out the agreed apportionment of financial and in-kind contributions that will ensure delivery of all AGT1 infrastructure. These principles will be legally secured through planning obligations (contained within each section 106 agreement) and planning conditions for each individual application.

Development of the Infrastructure Delivery Framework will be based on the following key principles:

1. Positive engagement and involvement of all parties needed to deliver strategic infrastructure;
2. Identified responsibility for delivery of strategic infrastructure;
3. Agreed triggers for delivery of infrastructure (distinguishing between negotiable and non- negotiable triggers);
4. Speed, pace & sequencing of development. Infrastructure to reflect partners' positions (e.g. what if sites come forward in different order to that envisaged);
5. Apportionment of infrastructure costs by net developable area and proportionality in respect of costs or as may otherwise be agreed
6. Framework for public funding to be levered in if appropriate;
7. Reasonably easy to use and monitor;
8. Does not hold up development starting;
9. Commitments from all parties:
   1. to the delivery of Strategic Infrastructure;
   2. not inhibit other parties' right to develop/deliver;
10. Framework for review mechanism;
11. Flexibility to adapt to changing circumstances, e.g. significant market shifts, housing mix & values;
12. Includes early warning signals to highlight problems including delay with delivery arrangements and explore the possibility of mechanisms e.g. 'step-in' rights
13. Full recovery of costs and forward funding by the Council or any agreed and implemented Delivery Body.

As noted above, the preferred method of calculating apportionment is by Net Developable Area held by each landowner or developer. The IDF will set out the position with regards to the areas and proportions of the AGT1 site under various different land ownerships. To ensure the appropriate mechanism to deliver the required infrastructure, the proposed apportionment and methodology will be set out in the IDF so that both the council and individual landowners / developers within the site are aware of the requirements, thus ensuring the approach to delivery is as comprehensive as possible. The IDF will be worked upon as applications are submitted and evolve and will be able to include detailed mechanisms for delivery, the exact costings and permutations for different areas coming forward at different times resulting in it being a living document to reflect the latest position analysis that accompanies planning applications.

The IDF will be brought forward and adopted by the Council in advance of the determination of the first major planning application for the AGT1 site and each AGT1 planning application is required to be fully compliant with its terms. Any planning application that seeks to be determined in advance of the IDF being adopted would be required to demonstrate full policy compliance, acceptance of a proportionate cost of all of the AGT1 infrastructure and that infrastructure could be delivered in full and how this would be achieved.

The IDF will set out definitive expectations of what would be contained within the legally binding commitments in each application s106 agreement. This will enable the Council to ensure that infrastructure will be costed and delivered in a timely and holistic manner. A separate memorandum of understanding document between the AGT development Consortium members could also be produced and submitted to the Council as additional assurance (potentially as an additional application document when each application comes forward). The Memorandum would provide a clear basis for the Council to impose lawful planning obligations and conditions to secure the relevant infrastructure in a planned holistic manner, in accordance with this SPD document and Infrastructure Development Framework to follow.

Highways Improvements

Further site / area specific highway infrastructure will be required for delivery under individual detailed planning permissions for the relevant phase of the development. This will include the provision of items such as cycle and footpaths, streets, and possible off-site highway improvement works.

Highway modelling work will consider the proposed access locations; trip generation methodology and modelling scenarios in relation to the development of AGT1. This uses existing data together with predicted data estimates of future traffic to calculate the capacity of infrastructure and thus the need for improvements to highway infrastructure.

Provision for these site and highways improvements will need to be made in step with the requirements of each phase of development whilst ensuring that provision is coordinated between phases. These will be detailed within the IDF agreement and legally secured through the section 106 agreement and planning conditions for each individual application.

Viability and Deliverability

Key to a successful development will be the delivery of a high quality and sustainable place in which to live, including the provision of appropriate infrastructure at the right time. Co-ordination between the Council, landowners / developers and key stakeholders will be key to this. Given the long timescale for delivery of South Aylesbury the continued viability of the site to ensure its continued long-term delivery is of paramount importance. It may therefore be appropriate to reconsider the viability of proposals at later stages. This may mean that the level and / or timing of affordable housing provision required or the timing of provision of elements of infrastructure as set out in this Supplementary Planning Document may need to be revisited.

Where landowners / developers wish to consider scheme viability, which is likely to be when planning applications are submitted, the Council will require an open book approach to be taken so that the outcomes and implications of viability testing at application stage can be carefully evaluated by the Council in light of the aspirations and requirements set out in this Supplementary Planning Document.

Chiltern Beechwoods Special Area of Conservation

D-AGT1 will create at least 1,000 new homes. An increase in the number of homes is expected to lead to an increase in the population residing within the 12.6 kilometre Chilterns Beechwoods Special Area of Conservation Zone of Influence.

To mitigate the potential recreational disturbance from this population to the Chilterns Beechwoods Special Area of Conservation a twin mitigation package is required.

It is anticipated that this will take the form of:

1. A financial contribution from each net new home within the Zone of Influence towards a Strategic Access Management and Monitoring Strategy. This strategy will be set out in a Supplementary Planning Document.
2. The delivery of 50% green infrastructure to Accessible Natural Green Space Standard within the allocation. The green infrastructure being provided must have a long-term management and maintenance strategy and be agreed by the council. A mechanism must be secured to manage the green infrastructure in perpetuity. The management and maintenance strategy shall set out details of the owner, the responsible body and how the strategy can be implemented by contractors.

The delivery and the in-perpetuity maintenance of the 50% green infrastructure to Accessible Natural Green Space Standard is capable of satisfying the requirements for Suitable Accessible Natural Green Space; and should be agreed with Natural England. The aim of this green space is to provide a good quality and accessible recreational space capable of reducing the need for the new population to visit the Chilterns Beechwoods Special Area of Conservation. Perpetuity in this context is taken as at least 80 years.

Both of these mitigation measures will be considered as part of the determination of planning applications submitted to the council for this allocation affecting the Zone of Influence.