Southbourne Allocation Development Plan Document: Regulation 18 Consultation Main Document

No

Southern Water supports the vision and objectives set out in the Southbourne Allocation Development Plan Document; however, we would welcome some additional wording that recognises the role of climate change in increasing the risk of fluvial, pluvial and sewer flooding, and the risk of water scarcity. Recommendation: Therefore, we recommend the following additional wording (in brackets) to paragraph 4.8 of Chapter 4. Climate change and moving towards net zero carbon living 4.8 Respond positively to the environment to ensure climate resilience and future-proofing, by adopting the Future Homes Standard, strengthening green and blue infrastructure, promoting walking and cycling as the preferred options for short journeys, (reducing flood risk through the adoption of sustainable drainage systems and increasing resilience to water scarcity through water efficient house design), and contribute towards achieving net zero lifestyles. We make this recommendation as we believe sustainable drainage systems (SuDS) should be a requirement for all new all development. Whilst some parts of the sewer network were originally designed to accommodate surface water, the expansion of towns, cities and villages, in particular of ‘urban creep’ can exacerbate capacity issues. As stated in Water UK’s 21st Century Drainage Programme; “The country’s built environment is constantly changing and “urban creep” – home extensions, conservatories and paving over front gardens for parking – can all add to the amount of water going into our sewers and drains. Green spaces that would absorb rainwater are covered over by concrete and tarmac that will not. In fact, studies show that “urban creep” results in a larger increase in predicted flooding than new housing, because it adds more rainwater to these systems’. In terms of flood risk, better rainwater management is key to achieving not only a reduced risk of flooding, but also a reduction in storm overflow releases and reduced demand on water resources. To help achieve this, Southern Water supports objectives, policies and design practice that prioritise on-site surface water management through effective SuDS provision. As set out in the Chichester Local Plan, Water efficiency is regulated by Part G of the Building Regulations which require (section G2) that reasonable provision must be made by the installation of fittings and fixed appliances that use water efficiently for the prevention of undue consumption of water. Whilst we are not the water supplier for Southbourne, we would welcome wording that recognises water efficiency as an objective.

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Wastewater Sewer Catchment: Southern Water is the statutory wastewater undertaker for the Southbourne area. In accordance with this, we have undertaken an assessment of the existing capacity of our sewer network and its ability to meet a possible forecast demand for this proposal, based on a calculated flow rate. Please note that in recognition of paragraph 5.3 in Chapter 5 Site Scenario Options, we assessed capacity for 1,050 dwellings as referred to in the Policy A13 of the local plan, and the 800 dwellings planned for in this DPD. The assessment reveals that the local sewer network in closest proximity to the site has sufficient sewer network capacity for 800 dwellings. The assessment also reveals that the local sewer network in closest proximity to the site has limited capacity to accommodate a proposed development of 1,050 dwellings. Limited capacity is not a constraint to development provided that planning policy and subsequent conditions ensure that occupation of the development is phased to align with the delivery of wastewater infrastructure. Proposals for 1,050 dwellings at this site could generate a need for reinforcement of the wastewater network in order to provide additional capacity to serve the development. This reinforcement would be provided through the New Infrastructure charge, but Southern Water would need to work with site promoters to understand the development programme and to review whether the delivery of network reinforcement aligns with the occupation of the development. Connection of new development at this site ahead of new infrastructure delivery could lead to an increased risk of flooding unless any requisite works are implemented in advance of occupation. Southern Water has limited powers to prevent connections to the sewerage network, even when capacity is limited. Planning policies and planning conditions, therefore, play an important role in ensuring that development is coordinated with the provision of necessary infrastructure, and does not contribute to pollution of the environment, in line with paragraph 180(e) of the revised National Planning Policy Framework (NPPF) (2023). Therefore, there is currently capacity on the sewer network to accommodate 800 dwellings. However, should this be 1,050 dwellings, then we would recommend the following Challenge (in brackets) for Scenario 1: Land to the West. (Due to capacity constraints on the public wastewater network, occupation of the development will need to be phased to align with the delivery of sewerage infrastructure, in liaison with the service provider.) Thornham Wastewater Treatment Works (WwTW): Wastewater Treatment Works (WTWs) treat wastewater collected from homes and businesses within their ‘catchment’ via a network of connecting pipes and pumping stations. WTWs are significant assets, upgrades to which are funded through the water industry’s 5 yearly investment plan which sets out spending requirements over the next 5 year period (AMP) using customer generated income. Wastewater from development in Scenario 1 would drain through the sewer network to Thornham Wastewater Treatment Works (WwTW) for treatment. As set out in paragraph 4.107 of the Chichester Local Plan, a position statement to manage development in the Thornham Wastewater Treatment Catchment was agreed in November 2021. This is a joint Chichester District Council, Southern Water Services and Environment Agency position statement and is required due to the ‘headroom’ at the WwTW being environmentally constrained. Therefore, any Residential development within the catchment of the Thornham Wastewater Treatment Works would need to be in accordance with Policy NE16 ‘Water Management and Water Quality’ of the Chichester Local Plan, which mandates that a “drainage impact assessment should show that the development complies with the principles set out in the latest Thornham Position Statement”. As such we propose the inclusion of the following additional Challenge (in brackets) to Scenario 1. (Due to the ‘headroom’ at the Thornham Wastewater Treatment Works being environmentally constrained, any Residential development within the catchment would need to be in accordance with Policy NE16 ‘Water Management and Water Quality’ of the Chichester Local Plan, which mandates that a “drainage impact assessment should show that the development complies with the principles set out in the latest Thornham Position Statement”.) We recognise the concerns of residents and developers in relation the environmental constraints at Thornham Treatment Works and the impact this can have on development in Southbourne. During the next 5 yearly investment period (2025-30) we will be increasing the hydraulic and process capacity of the site to accommodate the population growth forecast in the Local Plan. Over the same 5 year period we will also be undertaking sewer rehabilitation and maintenance to increase the operational resilience of the Thorhnham WwTW sewer catchment, and use SuDs and storage in various locations to reduce storm overflows. We will keep Chichester District Council updated with the progress of this work through our quarterly meetings.

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Wastewater Sewer Catchment: Southern Water is the statutory wastewater undertaker for the Southbourne area. In accordance with this, we have undertaken an assessment of the existing capacity of our sewer network and its ability to meet a possible forecast demand for this proposal, based on a calculated flow rate. Please note that in recognition of paragraph 5.3 in Chapter 5 Site Scenario Options we assessed capacity for 1,050 dwellings, as referred to in the Policy A13 of the local plan and the 800 dwellings planned for in this DPD. The assessment reveals that the local sewer network in closest proximity to the site has sufficient sewer network capacity for 800 dwellings. The assessment also reveals that the local sewer network in closest proximity to the site has limited capacity to accommodate a proposed development of 1,050 dwellings. Limited capacity is not a constraint to development provided that planning policy and subsequent conditions ensure that occupation of the development is phased to align with the delivery of wastewater infrastructure. Proposals for 1,050 dwellings at this site could generate a need for reinforcement of the wastewater network in order to provide additional capacity to serve the development. This reinforcement would be provided through the New Infrastructure charge, but Southern Water would need to work with site promoters to understand the development programme and to review whether the delivery of network reinforcement aligns with the occupation of the development. Connection of new development at this site ahead of new infrastructure delivery could lead to an increased risk of flooding unless any requisite works are implemented in advance of occupation. Southern Water has limited powers to prevent connections to the sewerage network, even when capacity is limited. Planning policies and planning conditions, therefore, play an important role in ensuring that development is coordinated with the provision of necessary infrastructure, and does not contribute to pollution of the environment, in line with paragraph 180(e) of the revised National Planning Policy Framework (NPPF) (2023). Therefore, there is currently capacity on the sewer network to accommodate 800 dwellings. However, should this be 1,050 dwellings, then we would recommend the following Challenge (in brackets) for Scenario 2: Land to the East. (Due to capacity constraints on the public wastewater network, occupation of the development will need to be phased to align with the delivery of sewerage infrastructure, in liaison with the service provider.) Thornham Wastewater Treatment Works (WwTW): Wastewater Treatment Works (WTWs) treat wastewater collected from homes and businesses within their ‘catchment’ via a network of connecting pipes and pumping stations. WTWs are significant assets, upgrades to which are funded through the water industry’s 5 yearly investment plan which sets out spending requirements over the next 5 year period (AMP) using customer generated income. Wastewater from development in Scenario 2 would drain through the sewer network to Thornham Wastewater Treatment Works (WwTW) for treatment. As set out in paragraph 4.107 of the Chichester Local Plan, a position statement to manage development in the Thornham Wastewater Treatment Catchment was agreed in November 2021. This is a joint Chichester District Council, Southern Water Services and Environment Agency position statement and is required due to the ‘headroom’ at the WwTW being environmentally constrained. Therefore, any Residential development within the catchment of the Thornham Wastewater Treatment Works would need to be in accordance with Policy NE16 ‘Water Management and Water Quality’ of the Chichester Local Plan, which mandates that a “drainage impact assessment should show that the development complies with the principles set out in the latest Thornham Position Statement”. As such we proposed the inclusion of the following additional Challenge (in brackets) to Scenario 2. (Due to the ‘headroom’ at the Thornham Wastewater Treatment Works being environmentally constrained, any Residential development within the catchment would need to be in accordance with Policy NE16 ‘Water Management and Water Quality’ of the Chichester Local Plan, which mandates that a “drainage impact assessment should show that the development complies with the principles set out in the latest Thornham Position Statement”.) We recognise the concerns of residents and developers in relation the environmental constraints at Thornham Treatment Works and the impact this can have on development in Southbourne. During the next 5 yearly investment period (2025-30) we will be increasing the hydraulic and process capacity of the site to accommodate the population growth forecast in Local Plan. Over the same 5 year period we will also be undertaking sewer rehabilitation and maintenance to increase the operational resilience of the Thorhnham WwTW sewer catchment, and use SuDs and storage in various locations to reduce storm overflows. We will keep Chichester District Council updated with the progress of this work through our quarterly meetings.

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Wastewater Sewer Catchment: Southern Water is the statutory wastewater undertaker for the Southbourne area. In accordance with this, we have undertaken an assessment of the existing capacity of our sewer network and its ability to meet a possible forecast demand for this proposal, based on a calculated flow rate. Please note that in recognition of paragraph 5.3 in Chapter 5 Site Scenario Options we assessed capacity for 525 dwellings at each location (split of 1,050 as referred to in the Policy A13 of the local plan) and we assessed capacity for the 400 dwellings at each location (split of 800 dwellings planned for in this DPD). The assessment reveals that the local sewerage network in closest proximity to the site has sufficient sewer network capacity for 400 dwellings allocated at the two sites. The assessment also reveals that the local sewer network in closest proximity to the site has limited capacity to accommodate a proposed development of 525 dwellings allocated at the two sites. The fact that the allocation is split into two locations does not reduce the overall volume of wastewater draining to the wastewater catchment, which would still equate to the same volume as 1,050. Limited capacity is not a constraint to development provided that planning policy and subsequent conditions ensure that occupation of the development is phased to align with the delivery of wastewater infrastructure. Proposals for 1,050 dwellings split across the two sites could generate a need for reinforcement of the wastewater network in order to provide additional capacity to serve the development. This reinforcement would be provided through the New Infrastructure charge, but Southern Water would need to work with site promoters to understand the development program and to review whether the delivery of network reinforcement aligns with the occupation of the development. Connection of new development at this site ahead of new infrastructure delivery could lead to an increased risk of flooding unless any requisite works are implemented in advance of occupation. Southern Water has limited powers to prevent connections to the sewerage network, even when capacity is limited. Planning policies and planning conditions, therefore, play an important role in ensuring that development is coordinated with the provision of necessary infrastructure, and does not contribute to pollution of the environment, in line with paragraph 180(e) of the revised National Planning Policy Framework (NPPF) (2023). Therefore, there is currently capacity on the sewer network to accommodate 400 dwellings at each site. However, should this be 525 dwellings at each site, then we would recommend the following Challenge (in brackets) for Scenario 3: Mixed Scenario. (Due to capacity constraints on the public wastewater network, occupation of the development will need to be phased to align with the delivery of sewerage infrastructure, in liaison with the service provider.) Thornham Wastewater Treatment Works (WwTW): Wastewater Treatment Works (WTWs) treat wastewater collected from homes and businesses within their ‘catchment’ via a network of connecting pipes and pumping stations. WTWs are significant assets, upgrades to which are funded through the water industry’s 5 yearly investment plan which sets out spending requirements over the next 5 year period (AMP) using customer generated income. Wastewater from development in Scenario 3 would drain through the sewer network to Thornham Wastewater Treatment Works (WwTW) for treatment. As set out in paragraph 4.107 of the Chichester Local Plan, a position statement to manage development in the Thornham Wastewater Treatment Catchment was agreed in November 2021. This is a joint Chichester District Council, Southern Water Services and Environment Agency position statement and is required due to the ‘headroom’ at the WwTW being environmentally constrained. Therefore, any Residential development within the catchment of the Thornham Wastewater Treatment Works would need to be in accordance with Policy NE16 ‘Water Management and Water Quality’ of the Chichester Local Plan, which mandates that a “drainage impact assessment should show that the development complies with the principles set out in the latest Thornham Position Statement”. As such we proposed the inclusion of the following additional Challenge (in brackets) to Scenario 3. (Due to the ‘headroom’ at the Thornham Wastewater Treatment Works being environmentally constrained, any Residential development within the catchment would need to be in accordance with Policy NE16 ‘Water Management and Water Quality’ of the Chichester Local Plan, which mandates that a “drainage impact assessment should show that the development complies with the principles set out in the latest Thornham Position Statement”.) We recognise the concerns of residents and developers in relation the environmental constraints at Thornham Treatment Works and the impact this can have on development in Southbourne. During the next 5 yearly investment period (2025-30) Southern Water will be increasing the hydraulic and process capacity of the site to accommodate the population growth forecast in the Local Plan. Over the same 5 year period we will also be undertaking sewer rehabilitation and maintenance to increase the operational resilience of the Thorhnham WwTW sewer catchment, and use SuDs and storage in various locations to reduce storm overflows. We will keep Chichester District Council updated with the progress of this work through our quarterly meetings.

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