Drainage Strategy – Sidlesham We’ll update and republish this Drainage Strategy as we continue to engage with our customers and stakeholders. (Manhood Peninsula) You can find further information on how to share your feedback via our website: southernwater.co.uk/drainagestrategies

Southern Water Southern House Yeoman Road Worthing West Sussex BN13 3NX 4593_04.18 Page 2 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 3

Executive summary

Environment Agency and other organisations The Drainage Strategy for Sidlesham Long-term outcomes Current issues and future challenges (Manhood Peninsula) focuses on to find and fix the causes of pollution which for Sidlesham (Manhood Peninsula) are preventing the bathing water from being the current pressures and future Our Five-year Business Plan 2015 to 2020 sets out details of the improved water and consistently rated as ‘excellent’. Some challenges that will impact on the Over the next 25 years, population growth is wastewater services we will provide in expected to result in a 12% increase in domestic rivers, groundwater and other water bodies sewerage network and wastewater the future. It was developed as a result of properties connecting to our sewers in the in the catchment were classified as ‘bad’ treatment works. the company’s biggest ever consultation Sidlesham wastewater catchment. Climate to ‘moderate’ status in 2015 according to programme which included feedback from change and urban creep are expected to add the Water Framework Directive (WFD) and more than 34,000 customers and stakeholders. to surface water flows into our sewers which, in require improvement to ‘good’ status by 2027. It will enable us to take a more strategic Partnership working will be key to achieving the approach to drainage planning across the area, The business plan is built around the delivery turn, will increase the number of properties at risk from surface water flooding. higher environmental standards required under providing a long-term (25-year) strategy to of six outcomes which our customers and the WFD. ensure we deliver a reliable and sustainable stakeholders told us were their priorities. For Maintaining and improving bathing water wastewater service for the region while each outcome, we have developed a clear set quality is essential for encouraging tourism and We have assessed the risks to the delivery of accommodating population growth, new of promises that detail what we will achieve for supporting economic prosperity in the region. our key outcomes if we were to do nothing, development, climate change and stricter our customers. Three of these outcomes are The Manhood Peninsula has a ‘Blue Flag’ summarised in table 1. These risks will be environmental quality standards. relevant to the Drainage Strategy for Sidlesham award for its West Wittering beach. At Selsey, identified, assessed and reduced through our and are shown in figure 1 below alongside the ‘business as usual’ activities. The Sidlesham wastewater catchment we are working with the local authorities, the relevant promises associated with them. includes the villages of Almodington, Birdham, Bracklesham, Selsea, Sidlesham, East/West Table 1. Key outcomes at risk in the Sidlesham catchment (Manhood Peninsula) if we do nothing Wittering and West Itchenor in the Manhood Peninsula, south of Chichester. Risk of not delivering the outcome by: Key outcome Comments 2020 to 2025 2040 Figure 1. Outcomes relevant to the Drainage Strategy for Sidlesham (Manhood Peninsula) Maintain compliance at Medium to high High Sidlesham Wastewater Treatment Works is currently operating at wastewater treatment its treatment capacity and is likely to require an uplift in treatment Removing wastewater Looking after Better information works capacity and dry weather flow consent in line with the anticipated growth in new connections. Additional capacity could be delivered in effectively the environment and advice parallel with development. Minimise flooding due to Medium Medium to high The Sidlesham network can accommodate approximately 53% of the • Minimise flooding due to • Minimise wastewater pollution • Improve advice on how to wastewater forecast new wastewater connections over the next 25 years without wastewater and surface water so that by 2020 there will be prevent blocked drains to help an unacceptable deterioration in our wastewater service. Additional with a 25% reduction in internal no serious (Category 1 & 2) reduce blockages capacity could be delivered in parallel with development. sewer flooding incidents by 2020 pollution incidents caused by our Minimise flooding due Medium Medium to high Groundwater infiltration is considered to be significant across the operations. We are also aiming to surface water and catchment and has been an issue in the village of Sidlesham where to halve the number of minor groundwater repairs have been carried out. Groundwater levels may get higher as a consequence of rising sea levels due to climate change. (Category 3) incidents from 2017 onwards Surface water flooding has been a significant issue due to the limited capacity of the land drainage system. Flooding is likely to increase • Maintain wastewater treatment due to more intense storms caused by climate change and more works compliance by ensuring run-off due to urban creep. that any releases to the Minimise pollution Low Low to medium The number of pollution incidents in 2015 and 2016 were relatively environment comply with permit low. The likelihood and severity of pollution incidents may increase conditions due to additional wastewater, surface water and groundwater in the sewerage system. • Maintain ‘excellent’ bathing Improve water bodies Medium Medium Nine out of 11 water bodies on the Manhood Peninsula are predicted water quality and improving (river, lake, coastal to achieve ‘good’ status by 2027 with the remaining two at other bathing waters groundwater) ‘moderate’ status. Partnership working will be key to achieving the higher environmental standards required under the WFD. Maintaining ‘excellent’ Low to medium Low to medium Three out of four bathing waters in the region have generally bathing water quality ‘excellent’ bathing water quality. At Selsey, we are working with partners to improve bathing water quality to ‘excellent’ by 2019–20. Page 4 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 5

Table 3. Action plan for the Drainage Strategy for Sidlesham (Manhood Peninsula) No. Action Lead Supporting Due date Action delivery status action action owner owners 1 Through the SW WSCC, EA, End of 2016 A draft drainage strategy was issued to external stakeholders in drainage strategy, CDC November 2016 for comment and discussion. Feedback has been We are assessing a range of traditional identify current received from WSCC, CDC and the EA during the winter of 2016-17. engineering and alternative strategies to Next steps drainage issues, key risks, shared tackle the current drainage issues and future We will update and revise this drainage outcomes and risks that have been identified for the area. strategy to reflect consultations with our potential actions We are also investing in the development customers and stakeholders in the region. 2 Publish the drainage SW All Following The drainage strategy will be updated with feedback from external of innovative techniques that will bring a We will continue to work with the local strategy on the stakeholders receipt of stakeholders before publication. significant improvement to our capabilities and community to gain important feedback from Southern Water comments performance. Potential strategies are being our customers and local stakeholders which we website from assessed against whole life costs, constraints will use to shape our solutions. We have already external Customers and other stakeholders will have the opportunity to and benefits to both the environment and stake- provide feedback on the final drainage strategy. begun discussions with our regional drainage holders stakeholders. Table 2 lists the key outcomes at partners and we will work collaboratively to risk and offers potential strategies which could agree and implement a strategy that ensures a 3 Improve Selsey’s SW WSCC, EA, 2019–20 In May 2017, Selsey was named as one of seven bathing waters be implemented to overcome the issues and reliable and effective wastewater service bathing water CDC to be improved to ‘excellent’ as detailed in the action plan for the quality to ‘excellent’ bathing water. challenges that threaten them. for the region in the long term. 4 Review the needs SW WSCC, EA, End of 2017 In March 2015, a meeting was held with external stakeholders to Table 3 provides an action plan for this strategy and options CDC identify risks in the Sidlesham catchment to inform the DAP. which we will implement in partnership with identified in the Sidlesham DAP Structural, operational, growth, flooding and environmental needs other stakeholders in the region. and potential options have been identified and are being reviewed. 5 Produce an action SW WSCC, EA, Summer A Sidlesham DAP action plan is provided in appendix B of this Table 2. Key outcomes at risk and potential strategies for Sidlesham (Manhood Peninsula) plan following CDC 2017 drainage strategy. completion of the Key outcomes at risk Potential strategies Sidlesham DAP Maintain compliance at • Collaboration with the local authority and developers to understand the timing, size and location of 6 Complete the SW 2018 The Pagham DAP will be produced as part of Southern Water’s wastewater treatment works developments with planning certainty Pagham DAP which ongoing 2015 to 2020 DAP programme prior to updating the • Reduce groundwater infiltration of foul sewers covers part of the drainage strategy for the Manhood Peninsula. Manhood Peninsula • Provide additional treatment capacity at the works as required 7a Identify sewerage SW Not stated An investigation of the sewer flooding issues in the eastern part • Transfer wastewater to other treatment works with spare capacity flooding issues in SWMP of Selsey has been carried out as part of the Sidlesham DAP using and remedial hydraulic modelling of the sewerage system. A potential cause of Minimise flooding and • Collaboration with the local authority and developers to understand the timing, size and location of measures in Selsey sewer flooding has been identified as a lack of capacity in parts of pollution due to wastewater developments with planning certainty (SWMP Ref. the sewerage system. Possible options to reduce sewer flooding • Upsize foul/combined sewers, pumps and rising mains as required SELS_004) have been identified and will be considered during the assessment of all options identified in the DAPs in the Southern Water region. • Reduce groundwater infiltration of foul sewers 7b Identify sewerage SW Not stated As part of the Sidlesham DAP, sewer flooding issues have been • Transfer wastewater to other treatment works with spare capacity flooding issues and in SWMP investigated in property flooding clusters to the south and west • Construct offline storage tanks to attenuate high flows remedial measures of Sidlesham village. The flooding mechanism has been identified in Sidlesham. Local as possibly being due to groundwater infiltration or surface water • Reduce surface water flows in combined sewers residents have inundation of the foul sewer network. reported concerns Minimise flooding and • Remove misconnections of surface water to foul sewers about foul flows in Southern Water carried out surveys and repairs for groundwater pollution due to surface Jury Lane. (SWMP infiltration in the village of Sidlesham in 2013. Ongoing monitoring of water and groundwater • Maintain public sewers, highway drains and land drainage system Ref. SIDL_009) flow levels are to be carried out to check whether the repairs have • Upsize surface water/combined sewers and pumps as required been successful or whether further infiltration reduction is required. Southern Water does not manage sewers in Jury Lane, Sidlesham. • Construct offline storage tank/s to manage the impact of high flows 7c The foul pumping SW Not stated An investigation of sewer flooding issues in West Wittering was • Installation of sustainable drainage systems (SuDS) station on Pound in SWMP included in the Sidlesham DAP. Hydraulic modelling has predicted • Separation of surface water from foul water in combined sewers Road in West potential flooding in Pound Road. Groundwater infiltration of the foul Wittering is thought sewer network may be a cause of the flooding and requires further • Reduce groundwater infiltration of foul sewers to be the cause investigation using long term flow monitoring and possible CCTV Improve water bodies to • Implementation of Integrated Water Cycle Management and working with external stakeholders to reduce of sewer flooding surveys of the sewers. ‘good’ status by 2021–27 the pollution of water bodies (SWMP Ref. WWIT_004) Maintain ‘excellent’ bathing • Minimise pollution due to additional wastewater, surface water and groundwater flows using the potential waters strategies described above 8 Investigate the use SW WSCC, EA, 2018 Consultants have been appointed to carry out a study on the of SuDS to manage CDC benefits of SuDS for Southern Water and its customers. Drainage surface water issues partners are to be consulted on SuDS policy and implementation in each region. 9 Provide support WSCC Community Ongoing Communities are being encouraged to prepare for and reduce the and funding groups, town risk and impacts of flooding in West Sussex through the provision of for Operation and parish funding of £1.25m in 2013, £1.1m in 2014–15 and £0.5m in 2016–17. Watershed Active councils Communities Fund

(SW=Southern Water, EA =Environment Agency, WSCC=West Sussex County Council, CDC=Chichester District Council, DAP= Drainage Area Plan, SuDs=sustainable drainage systems, SWMP=surface water management plan) Page 6 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 7

Contents 1. Introduction

2 Executive Summary The Manhood Peninsula is located connected to the public sewerage system and south of Chichester and falls within also treats the wastewater produced by visitors 7 1. Introduction to the region and trade effluent where these the administrative boundary of 8 2. What is a Drainage Strategy? businesses connect to public sewers. Some Chichester District Council and West rural areas are not connected to the public 9 3. Working in partnership Sussex County Council. sewerage system and properties in these areas 10 4. Current drainage and flooding issues in the Manhood Peninsula may discharge their wastewater into septic The region extends from Chichester Harbour tanks or private sewage treatment systems 10 4.1 Environmental quality in the west to Pagham Rife in the east and to which are not operated by Southern Water. 11 4.2 Protection of groundwater sources Selsey at the southernmost tip of the peninsula. The wastewater from the Manhood Peninsula 11 4.3 Bathing waters Villages in the region include Almodington, villages of North Mundham and Hunston flows Birdham, Bracklesham, East/West Wittering, southwards to the Pagham WTW which serves 13 4.4 Shellfish waters Sidlesham and West Itchenor. a catchment area of approximately 4km² and 13 4.5 Flooding Sidlesham Wastewater Treatment Works (WTW) approximately 4,000 properties connected to 18 5. Wastewater services in the Sidlesham catchment treats wastewater that Southern Water collects the public sewers. This drainage strategy will from a catchment which covers an area of be reviewed and updated when information is 18 5.1 Wastewater collection and treatment process approximately 16km² as shown in figure 2. The available from the Pagham drainage area plan as discussed in section 2. 19 5.2 Wastewater catchment maps and schematic works serves approximately 10,500 properties 20 5.3 Wastewater service performance Figure 2: Location of wastewater catchments serving the Manhood Peninsula 22 6. Risks to Wastewater services 22 6.1 Growth 22 6.1.1 Network capacity for growth 24 6.1.2 Treatment capacity for growth

25 6.2 Climate change KENT 26 6.3 Urban creep 26 6.4 Asset deterioration EAST SUSSEX 27 6.5 Infiltration HAMPSHIRE WEST SUSSEX 28 6.6 Clean water consumption

29 6.7 Environmental legislation 30 7. Strategic assessment

30 7.1 Outcomes for the Sidlesham catchment (Manhood Peninsula) ISLE OF WIGHT 32 7.2 Key outcomes at risk 33 7.3 Strategies: Business as usual activities 34 7.4 Strategies: Least whole life cost approach

35 7.5 Strategies: Innovation Key: 35 7.6 Strategies: Sustainable drainage systems Southern Water water supply 36 7.7 Strategies: Surface water separation and wastewater treatment area 36 7.8 Strategies: Removal of misconnections Designated bathing waters 37 7.9 Strategies: Integrated Water Cycle Management 37 7.10 Strategic assessments for the delivery of key catchment outcomes 39 8. Next Steps 40 9. Action Plan 41 10. Glossary of Terms 43 11. References 44 Appendix A – Strategic assessments 56 Appendix B – Sidlesham DAP Action Plan Page 8 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 9

2. What is a Drainage Strategy? 3. Working in partnership

We will work with our key stakeholders to The Drainage Strategy for Sidlesham What is a Drainage Area Plan? To ensure we develop and implement (Manhood Peninsula) will enable us the most effective and sustainable improve our knowledge and understanding of issues such as population growth, climate to take a more strategic approach to This drainage strategy incorporates information strategies, we will need to work in from the Sidlesham Drainage Area Plan change and urbanisation of green spaces. drainage planning across the area. (Southern Water/MWH, 2015). partnership with other organisations who also have important drainage A high level representation of the main Southern Water maintains a rolling programme stakeholders who contribute to the It will provide a long-term (25-year) strategy to of drainage area plans (DAPs). The Pagham responsibilities. development of an effective drainage strategy ensure a reliable and sustainable wastewater DAP is included in our DAP programme for is shown in figure 4. service for the region while accommodating 2015 to 2020 and when it is completed we will For the Sidlesham catchment (Manhood population growth, new development, climate Since the South-West Sussex Internal Drainage update this drainage strategy. Peninsula) this will include: change and stricter environmental quality Board was dissolved recently, there is no standards. We prioritise the production of DAPs with • Chichester District Council internal drainage board for the Manhood the highest priority being those catchments Peninsula. To help develop the strategy, we have adopted • West Sussex County Council with existing issues such as sewer flooding, the Drainage Strategy Framework (Environment (Lead Local Flood Authority) and where there are proposals for future Agency et al., 2013), outlined in figure 3. This development which may affect the performance • Environment Agency framework recommends a four-stage planning of the sewerage system. Sidlesham was process when preparing drainage strategies. • Parish Councils selected as a priority DAP for these reasons. This is similar to that used in the development • Manhood Peninsula Partnership of surface water management plans. The schemes identified from all DAPs are reviewed and prioritised against competing • Local Flood Action Groups (eg West The Drainage Strategy for Sidlesham (Manhood needs across the region and are critical in Manhood, Birdham & Earnley, Sidlesham) Peninsula) covers the first (initialise/prepare) identifying investment requirement in the stage and the second (risk assessment) stage. production of five- yearly business plans. Figure 4. Roles and responsibilities for drainage Our activities as part of stage three include DAPs are internal Southern Water documents an options appraisal of both traditional and are not intended to be public-facing. DAPs and alternative strategies which we will be are a major source of information for drainage undertaking in collaboration with our key local strategies which have a wider remit and are drainage partners. designed for public consumption. Figure 3. Four stage process for the development of Drainage Strategies

Partnership Uncertainty Risk based

Whole life and Innovative and Live process costs benefits sustainable

Initialise/prepare Risk assessment Options appraisal Intervention

Establish Aligned delivery partnership and Consultation Consult and collaborative consultation on risk issues on options solutions process

Define Quantify Plan for Innovative and uncertainties uncertainties uncertainties sustainable

Demonstrate Prepare Quantify Live whole life cost risk data risks and visible and benefit Page 10 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 11

4. Current Drainage and Flooding Issues in the Manhood Peninsula The Broad Rife had an overall ‘bad’ ecological status in 2015. The Environment Agency 4.2 Protection of (EA) has identified saline intrusion affecting groundwater sources 4.1 Environmental quality invertebrates as a main contributor to the West Sussex has a high number of groundwater ‘bad’ status. A ‘poor’ to ‘moderate’ ecological The Manhood Peninsula benefits from a high-quality environment which includes a number of sources which provide clean, healthy drinking status for the Broad Rife has been identified water that Southern Water and Portsmouth designated sites where wildlife, habitats, landscapes and heritage are protected as detailed in as being due to dissolved oxygen and table 4. Water supplies to customers in the region. phosphates in continuous sewage discharge This groundwater is vulnerable to from wastewater treatment sources. However, Table 4. Designated sites on the Manhood Peninsula contamination from natural and man-made phosphates in rivers can also be due to run-off pollutants on the ground surface which pass Designated Site Description Sites on the Manhood Peninsula from agricultural land and leaking septic tanks. down through thin soils and fissures into the The Sidlesham Wastewater Treatment Works Ramsar and Special Protection Areas chalk aquifers. Pagham Harbour, Chichester & Langstone Harbours (wetlands, rare and migratory birds) discharges into the Broad Rife and further work is required to understand the source of Groundwater source protection zones show Special Areas of Conservation Solent Maritime (habitats and non-bird species) phosphates and dissolved oxygen and how the risk of contamination from any activities Southern Water can assist in improvements to that might cause pollution in the area and can Marine Conservation Zones Selsey Bill and the Hounds, Pagham Harbour the Broad Rife. be seen on maps at the EA’s ‘What’s in your backyard’ website. There are no protection Sites of Special Scientific Interest Selsey East Beach, Pagham Harbour, Bracklesham Bay, Chichester Harbour The Bremere Rife had a ‘bad’ ecological status zones in the Manhood Peninsula apart from in 2015 which the EA has identified as being a small zone 1 (inner) which is just south of Local Nature Reserves Pagham Harbour probably due to pollution in rural areas from Fishbourne and is outside the Sidlesham agricultural sources. Under the Water Framework Directive (WFD), the South-East River Basin Management Plan aims to wastewater catchment. The main protection achieve at least a ‘good’ status for all water bodies by 2027 with some expected to reach this status The Pagham Rife had a ‘failed’ chemical status zones are in the chalk downlands to the north by 2021 (Environment Agency, 2016). Table 5 shows the current and predicted status of the different in 2015 which is probably due to diffuse sources of Chichester. water bodies on the Manhood Peninsula. of pollution from rural areas, towns, cities and Under the WFD, the South East Hants transport (EA, 2016). Partnership working is Bracklesham groundwater body had a ‘poor’ Table 5. Water body status on the Manhood Peninsula in December 2015 (EA, 2016) key to achieving the higher environmental chemical status in 2015 which the EA identified Water body name Category Status type Classification Predicted Predicted standards required under the Water Framework as probably due to pollution from landfill (2015) outcome outcome Directive (WFD). leaching and industry. (2021) (2027) Ecological Bad Poor Good Broad Rife River Chemical Good Good Good 4.3 Bathing waters Ecological Bad Bad Good Bremere Rife River Chemical Good Good Good The Manhood Peninsula has four designated bathing water sites which have weekly Ecological Moderate Moderate Good Pagham Rife River assessments of bathing water quality during Chemical Fail Fail Fail the bathing season from May to September. Ecological Moderate Moderate Good Table 6 shows the historical and current annual Blue Flag Seaside Chichester Harbour Transitional water assessment for each of these bathing waters. award award Chemical Good Good Good Ecological Moderate Moderate Moderate Pagham Harbour Transitional water Table 6. Bathing waters classification for the Manhood Peninsula (Based on EU Bathing Waters Directive 2006/7/EC) Chemical Good Good Good Defra’s four-year rolling assessment Ecological Good Good Good Pagham Lagoon Transitional water Bathing Water 2009–12 2010–13 2011–14 2012–15 2013–16 2014–17 Chemical Good Good Good

Ecological Moderate Moderate Good Bracklesham Bay Excellent Excellent Excellent Excellent Excellent Excellent Sussex Coastal water Chemical Good Good Good

Ecological Moderate Moderate Good Pagham Excellent Excellent Excellent Good Good Good Chichester Canal Canal Chemical Good Good Good

Quantitative Good Good Good Selsey Good Good Sufficient Good Good Good South East Hants Bracklesham Group Groundwater Chemical Poor Poor Good

Quantitative Poor Good Good West Wittering Excellent Excellent Excellent Excellent Excellent Excellent Sussex Lambeth Group Groundwater Chemical Good Good Good

Quantitative Poor Good Good Littlehampton Anticline West Groundwater Chemical Good Good Good Page 12 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 13

West Wittering beach has been assessed as We are working with local authorities, the 4.4 Shellfish waters • West Sussex Local Flood Risk Management having ‘excellent’ bathing water quality over EA and other organisations over the next Strategy 2013 to 2018 (WSCC, 2014) the last five years and was awarded a Blue Flag five years to find and fix sources of pollution There is a shellfish water protected area in Manhood Peninsula Surface Water for its beach in 2017. In Bracklesham Bay and preventing seven bathing waters in our region Chichester Harbour (Thornham Channel) to •  Management Plan (ch2m for WSCC, 2015) Pagham, bathing water quality has also been from achieving ‘excellent’ standard – this is one the west of the Manhood Peninsula (Defra, consistently ‘excellent’ or ‘good’ over the last measure required for bathing waters to gain 2016) which is harvested for oysters, clams Groundwater flooding five years. ‘Blue Flag’ status. This added benefit is over and cockles. Further information is available in and above our statutory duties, which water The geology of the Manhood Peninsula Over the last 20 years, Southern Water has the Local Action Plan for Shellfish Harvesting companies are normally only funded to meet. determines whether the region is vulnerable to invested significantly to meet the requirements Beds in Chichester Harbour (Chichester District groundwater flooding. The chalk South Downs of the EU Urban Wastewater Treatment We have undertaken a rigorous selection Council and Havant Borough Council, 2015). are immediately north of Chichester from which Directive (91/271/EEC) to improve the quality of process to shortlist 21 bathing waters from Sidlesham WTW discharges into the Broad groundwater emerges at Fishbourne Springs treated wastewater that we discharge into the the 83 in our region for further investigation. Rife which flows into Bracklesham Bay in the northern extremity of the Manhood sea. This investment has included the provision Based on the Department for Environment, approximately 9km east of Chichester Harbour. Peninsula. It is believed that the groundwater of additional treatment at Sidlesham WTW Food & Rural Affairs’ (Defra’s) four-year rolling flow in the South Downs may contribute to the and at two large wastewater treatment works assessment, table 6 shows that the Selsey baseflow (the level of ground water that seeps (Ford near Arundel and Budds Farm, Havant) bathing water has generally been of ‘good’ 4.5 Flooding into the banks of a river or riverbed) in the which discharge into the sea in the vicinity of quality over the last five years, although it was The Manhood Peninsula is at risk of flooding upper reaches of the Pagham Rife. the Manhood Peninsula. assessed as ‘sufficient’ in 2014. As Selsey’s from groundwater, surface water, river and tidal bathing water has failed to reach ‘excellent’ In the central region of the Manhood Peninsula, Bathing water is affected by various sources of sources. The EA’s ‘What’s in your backyard’ quality in recent years, it was included in the the chalk layer is much deeper and is confined pollution such as: website provides maps which show the flood below thick layers of impermeable ‘London 21 shortlisted bathing waters. risk in the region. • the release of surface water after heavy Clay’ and ‘Reading Beds’ so that groundwater We spent a year carrying out a range of rain which contains contaminated rainwater It is Southern Water’s responsibility to ensure in the chalk is generally unable to flow to the detailed investigations including watercourse run-off from roads our customers can continue to use their surface. At the southern end of the peninsula, sampling, DNA analysis and CCTV surveys of wastewater services in the event of a flooding around Selsey, Earnley and Wittering, the sewers to understand the causes of pollution • diluted, partially-treated wastewater from incident. We will work alongside local councils, underlying geology is the ‘Bracklesham Group’. at each of the shortlisted bathing waters. We combined sewer overflows or pumping the EA and others to help alleviate the effects This formation comprises a mixture of silt, sand also held a series of customer focus groups stations that has been released to prevent of flooding on the community. and clay and may contain some groundwater in and have surveyed more than 3,600 customers heavy rainfall overwhelming the sewerage the more permeable areas. system and flooding properties and 300 businesses across the Southern Water As a flood risk management authority, Southern region to get a better understanding of the Water has the following responsibilities: The underlying strata are generally not misconnections of foul sewage into •  views and needs of the communities at each exposed at the surface and are covered by surface water sewers which discharge into • adopting new-build sewers location. thin superficial drift deposits. These deposits watercourses without treatment • managing public sewer flooding may contain coarse sands and gravels which In May 2017, seven bathing waters including wastewater from private treatment works can contain groundwater which is recharged •  Selsey were selected for improvements to • being scrutinised by the democratic and leaking septic tanks which are not relatively quickly following rainfall. This enable them to reach ‘excellent’ quality by processes of the lead local flood authority owned by Southern Water ‘shallow’ groundwater will then generally 2019–20. An action plan has been developed • acting in accordance with the national and discharge into drainage ditches that flow into decaying seaweed and algae reaching which provides an overview of the issues our •  local strategies for flooding performing as the rifes (rivers) on the peninsula. nuisance levels investigations uncovered at Selsey and the a Category 2 responder to flood incidents steps required to improve bathing water quality. Consequently, groundwater may increase under the Civil Contingencies Act. • heavy rainfall run-off from agricultural land flows in ditches and rifes which can contribute into rivers This project is part of our long-term plan to Southern Water’s management of public sewer to the risk of river flooding when surface water improve bathing water quality in our region. flooding is discussed later in this section. from heavy rainfall is added to the flow. Direct • animals and seabirds on or near beaches As part of this, we have committed to work groundwater flooding from emerging springs is with other agencies, local communities • waste from boats. Further information on groundwater, surface unlikely to occur in the Manhood Peninsula. and landowners to bring all coastal waters water and river flooding risk in the Manhood Our business plan for 2015–20 was developed at bathing beaches in the region up to the Peninsula and West Sussex can be found in the High groundwater levels can prevent surface through the biggest programme of customer standard required to achieve Blue Flag status following documents: water dispersing from sewers into the ground research in our history. During this process, our by 2040, provided there is continued support in soakaways which can result in surface water • Arun and Western Streams Catchment Flood customers indicated that clean bathing waters from our customers and regulator to do so.. flooding. There have been reports of flooding Management Plan (EA, 2009) and beaches are a priority and they are willing around soakaways in Stockbridge which is to contribute more towards improvements • Strategic Flood Risk Assessment of West just south of the A27 (CH2M for West Sussex where these are required. We are committed to Sussex (Capita Symonds for WSCC, 2010) County Council, 2015). maintaining the number of our bathing waters with ‘excellent’ water quality at 54 beaches • West Sussex Preliminary Flood Risk High groundwater levels can also cause across Hampshire, Isle of Wight, Kent and Assessment (WSCC, 2011) infiltration of sewers which is discussed further Sussex. in section 6.5. • West Sussex County Council Report on June 2012 Flood Event (WSCC, 2012) Page 14 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 15

River and tidal flooding We also have a stock of temporary flood Surface Water Management Plans (SWMP) are • run-off into the ditch network needs to barriers and mobile generators which can be used to identify and assess flood risks from be controlled including run-off from new The Manhood Peninsula is a low lying coastal used to ensure that our sites can continue to surface water and also local flooding due to developments and glass houses area which is artificially drained by a series of operate at normal output if the site should be groundwater and ordinary watercourses as main rivers known as ‘the rifes’ which are fed flooded. defined in the Flood and Water Management • the continuity of the ditch network is critical. by the ditch network. The rifes discharge into Act 2010. A SWMP will also include actions to Land drainage consents are important Sidlesham WTW is in a high risk EA flood zone Chichester Harbour, Pagham Harbour, the area reduce local flooding that have been agreed by in preventing culverting or infilling of 3 for river flooding (greater than 1% annual protected by the Medmerry scheme or directly the drainage partners. Progress on the actions watercourses where it will increase the probability) or sea flooding (greater than 0.5% into the sea. is reviewed periodically. These partners flood risk annual probability). However, the Medmerry include the lead local flood authority, highways In 2005, tidal flooding occurred to the west coastal flood defence scheme provides some • a consequence-based approach should be authorities, EA, sewerage undertaker and of Selsey when coastal defences were protection to the works from tidal flooding. adopted which focuses on the most critical overtopped. Since then, the Medmerry coastal others. parts of the drainage network. flood defence scheme has been completed Surface water flooding In 2015, the Manhood Peninsula Surface Water Southern Water is fully participating in between Selsey and Bracklesham and protects Management Plan was completed (CH2M for over 300 properties from tidal flooding. The low Significant flooding has occurred on several the development and implementation of occasions in the Manhood Peninsula due to the West Sussex County Council, 2015) based on the Manhood Peninsula Surface Water lying nature of the area means it is at particular the following objectives: risk from tidal flooding due to potential sea incapacity of the drainage ditches and rifes to Management Plan with our drainage partners. level rises as a result of climate change. drain surface water flows during prolonged wet • to understand the surface water drainage Actions include: winters – such as those experienced in 2012–13 in the area and gather additional data to • ongoing maintenance of the public High tides can prevent the rifes from draining and 2013–14. reduce gaps in knowledge into the sea which can create back-up in the sewerage network, pumping stations rifes and inland flooding. The EA is currently In June 2012, extreme rainfall resulted in the • to identify pinch points in the network and and combined sewer overflows to ensure reviewing the operation of its Ferry Road flooding of approximately 110 properties on connectivity issues surface water flows can flow freely to pumping station which pumps flows from the the Manhood Peninsula in the villages of East treatment works and/or controlled releases Wittering, Bracklesham, Almodington, Earnley, • to identify potential improvement works Broad Rife when it is tide-locked. Southern • the removal of properties which have been Birdham and Somerley (WSCC, 2012). The to reduce flood risk to communities in Water is currently considering options to listed on a register called the DG5 (see likelihood of this volume of rainfall is around the peninsula including capital and ensure that treated effluent can continue to glossary) as having experienced sewer once every 200 years and it overwhelmed maintenance measures, building on the be discharged from Sidlesham WTW when the flooding from water-pressure overloads the Manhood Peninsula land drainage system work already undertaken by communities, Broad Rife is tide-locked. caused by excessive surface water entering which is typically designed to withstand rainfall partnerships and other organisations the sewerage system During extreme rainfall events or following levels that occur between once in 25 to 100 • to produce up-to-date geographic prolonged wet winters, flooding can occur from years. information data of the ditch network. • the identification of misconnections of the rifes and the ditch network as they do not surface water sewers to foul sewers (and Surface water flooding in the Manhood have the capacity to drain away the surface The SWMP assessed flooding data from the vice-versa) water. Further information is provided in the Peninsula is the result of several factors: WSCC Highways Authority, Southern Water’s • promoting the use of sustainable drainage following section on surface water flooding. the low-lying nature of the area with little sewer flooding DG5 Register, key stakeholder •  systems (SuDS) to reduce surface water gradient to drainage ditches meetings and meetings with local residents. The management of river and tidal flooding risk Based on flooding history, seven high entering the sewers. is primarily the responsibility of the EA, district inadequate capacity of the drainage system •  priority locations were identified at Birdham Southern Water’s main responsibility is to and borough councils and internal drainage which is not designed to drain the surface & Westlands, East Wittering & Bracklesham, provide a resilient wastewater service in the boards. The EA has recently completed the water flows resulting from extreme rainfall Hunston, Selsey, Sidlesham, Somerley and Bookers Lane Flood Alleviation Scheme which event of surface water flooding. inconsistency in the ditch network such as West Wittering. A further five medium priority was partly funded by West Sussex County •  Sidlesham WTW is in a low risk zone (0.1% to 1% large ditches leading into small pipes or no locations were identified at Crouchers (A286), Council and local residents to reduce the risk of annual probability) for surface water flooding. pipes at all Runcton, South Mundham, Stockbridge and river flooding of properties in Earnley. Southern West Itchenor. Potential measures were However, some wastewater pumping stations Water will co-operate with the other relevant • poor maintenance of the network that leads identified for each location and actions were such as Memorial Hall, Itchenor are in high risk authorities in the exercise of their flood and to blockages and collapses of ditches and assigned to key stakeholders. zones (greater than 3.3% annual probability) coastal erosion risk management functions. culverts which remain unfixed for surface water flooding. Southern Water The SWMP identified five principles which are will assess flood risk and protect our sites Southern Water’s main responsibility is to impermeable clay soils which lead to •  key to ensuring the long-term management of from surface water flooding using the same provide a resilient wastewater service in the ground saturation and results in ponds of the drainage system on the Manhood Peninsula principles outlined above for river and tidal event of river or tidal flooding. We assess the surface water. risk of flooding at our wastewater treatment • ditch clearance remains the responsibility flooding. works and pumping stations and whether Surface water can overload combined of riparian (waterside property) owners and flooding could affect critical assets. If potential sewers which can result in flooding of diluted landowners under the Land Drainage Act of loss of service is identified and it is cost- wastewater or controlled releases to the river. 1991 beneficial to do so, we can provide permanent Surface water can also inundate foul sewers by • local communities have a key role to play flood protection measures such as bunding entering the sewer through unsealed manholes through local flood action groups etc (retaining walls), flood walls, watertight doors in flooded areas. and raising the height of critical equipment. Page 16 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 17

Sewer flooding (DG5 Register) Table 7: DG5 Register for the Sidlesham catchment For each of these flooding clusters, a hydraulic • Separate surface water from wastewater modelling assessment has been carried out (eg install separate drainage systems and/ Properties can be flooded internally or Flood Risk Internal External as part of the DAP and the results have been or removal of misconnections) externally if there is insufficient capacity in the Flooding Flooding verified by flow monitoring. Properties at risk Put in place sustainable drainage systems sewers to transfer flows caused by surface 2 in 10 Years 0 10 of flooding were assessed using a predictive •  water due to rainfall. After a sewer flooding, 1 in 10 Years 2 6 model based on a one in 30-year flood scenario • Adopt other solutions such as infiltration we investigate to establish whether it was the and allowed for a 20% increase in extreme reduction 1 in 20 Years 3 86 result of an overload of water pressure or other rainfall that might reasonably be expected For all flooding problems, surface water causes, such as blockages or sewer collapses. Total 5 102 to accompany climate change. An allowance separation has been considered as the We then work to identify events caused by for groundwater infiltration of the sewerage first option for flood alleviation. However, floods beyond our control. If appropriate, network has also been included in the model. the Sidlesham catchment is predominantly properties are added to the DG5 Register DAP flooding needs and options Asset surveys and impermeable area surveys which records properties at risk of flooding separately drained and infiltration removal Our drainage area plan (DAP) for the Sidlesham have been commissioned for this assessment. under a classification based on the number of is the recurring first step in addressing many catchment (Southern Water/MWH, 2015) is times they are likely to be flooded in a 10 or For each flooding cluster, a position statement of the needs. Infiltration reduction would be primarily focused on a hydraulic appraisal of the 20-year period. identifies the flooding mechanisms and highly beneficial to the performance of the drainage network. It includes an assessment of provides a high-level review of the current sewer network and will be likely to reduce the The DG5 Register is managed by Southern properties that are at risk of internal or external preferred solutions based on the following need to expand capacity or introduce storage Water and is regularly reviewed and updated. flooding due to hydraulic overload and are short-term and long-term options: schemes designed to address flooding and Further information may allow us to remove currently on the DG5 Register. growth needs in the catchment. Costs will be properties from the register or to downgrade • Do nothing The properties and locations at risk of flooding developed to enable a full appraisal to be made the risk of sewer flooding by transferring the in the Sidlesham catchment have been grouped • Isolation – disconnection of properties of all the options. property from, for example, a two in 10 to a one from the public sewer network. Flows are into nine priority flooding clusters The Sidlesham DAP action plan in appendix B in 10-year register or from the one in 10 to one transferred to offline storage and then provides a summary of the flooding issues in in 20-year register. • Selsey pumped to the public sewer. the catchment, proposed schemes to resolve Figure 5 shows that there have been two • Memorial Hall, Itchenor • Get the best from the existing system (eg the flooding, and the current status of these internal flooding incidents due to ‘hydraulic make improvements to the pumping station) schemes. overloading’ (excessive water) in the Sidlesham • Church Road, East Wittering Re-direct flows to parts of the network with catchment over the last five years. In 2012–13 •  Further long-term strategies are considered in • Highleigh sufficient capacity and 2013–14, there were a high number of section 7.10 and appendix A. external flooding incidents due to hydraulic • East Bracklesham • Provide additional storage within the Sewer flooding (other causes) overloading which were related to rainfall. • Almodington network There have been significantly fewer external Around 85% of internal flooding incidents are • West Wittering • Increase the size of storm tanks at the flooding incidents in the last three years. treatment works due to other causes such as sewer blockages, • Rookery Lane sewer collapses, or equipment failure. Figure Within the Sidlesham catchment, there are • Expand the existing sewer network currently five properties on the DG5 Register 6 shows a peak in 2012–13 in the number of • Pinks Lane, Birdham Increase the size of existing pumping which are at risk of internal flooding and 102 •  external flooding incidents due to other causes stations or provide new ones locations at risk of external flooding with a which have reduced significantly in the last four return period categorisation shown in table 7. • Provide or make changes to the combined years. sewer overflow

FloodingFigure incidents 5. Flooding due due to to hydraulic hydraulic overloading overloading in in the the Sidlesham Sidlesham catchment catchment Figure 6. Flooding due to other causes in the Sidlesham catchment Flooding incidents due to other causes in the Sidlesham catchment 80 1200 80 Internal Flooding External Flooding Regional Rainfall (mm) Internal Flooding External Flooding 70 1050 70 60 900 60 50 750 50

40 600 40 30 450

20 300 Regional rainfall (mm) 30

10 150 (public + S105A sewers) 20 overloading (public + S105A sewers)

0 0 10 Number of flooding incidents due to hydraulic 2012–13 2013–14 2014–15 2015–16 2016–17

Number of flooding incidents due to other causes 0 2012–13 2013–14 2014–15 2015–16 2016–17 Page 18 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 19

5. Wastewater services in the Sidlesham catchment The wastewater flows by gravity through In Selsey, there are combined sewer overflows 5.1 Wastewater collection 5.2 Wastewater catchment smaller drains and sewers to large diameter map and schematic (CSO) at East Beach Road, Crablands and and treatment process trunk sewers that carry wastewater flows from Church Road. If the flows exceed the capacity Southern Water collects and treats wastewater of the network in these locations then there Southern Water recycles wastewater from whole villages or suburbs of towns. Where from the Sidlesham catchment on the Manhood will be a controlled release of excess diluted almost two million homes in Kent, Sussex, required, the wastewater is pumped from a Peninsula. Figure 8 shows how wastewater screened flows to a watercourse, so that Hampshire and the Isle of Wight. Every day we low level to a higher level using pumps at a flows to the treatment works from the sewerage properties are protected from flooding. treat and recycle an average of 717 million litres wastewater pumping station (WPS). Figure network. These overflows are approved by the EA’s of wastewater at our 365 treatment works after 7 provides a simple diagram showing how permit team and none are currently classed it has been pumped through a sewer network the wastewater is collected, screened and The Sidlesham catchment has a total of as ‘unsatisfactory’ by the EA (Southern Water/ 39,600 kilometres long. processed at a wastewater treatment works approximately 167km of public sewers which MWH, 2015). before the treated water is returned to rivers or primarily comprise foul sewers that transfer Wastewater comes from water used in homes, the sea. Further information on the wastewater waste flows only. Less than 1% of the network Southern Water also manages approximately businesses and factories as well as some of the process can be found at southernwater.co.uk/ is combined sewers which transfer waste and 26km of separate surface water public surface water run-off from rain falling on roofs the-wastewater-process. surface water flows together in the same pipe. sewers mainly in Selsey and a small network or roads which ends up in our sewer network. in Bracklesham. The surface water sewers in There are 46 wastewater pumping stations Selsey flow into a pond at East Beach before in the Sidlesham catchment which have discharging into the sea. Private systems 36km of rising mains associated with them. Figure 7. The wastewater treatment process for surface water drainage may exist but are This is a relatively high number of pumping unrecorded and may drain into soakaways or stations for the size of catchment and they potentially discharge, as illegal connections, generally operate in sequence, pumping flow Homes and factories to the foul sewerage network. from one station sub-catchment to another. The performance of the pumping stations is In most villages there is a positive highway monitored remotely through a telemetry link. drainage system via gullies and pipes which Wastewater flows in sewers Surface water Figure 8. Sidlesham Wastewater Catchment

Arrives at wastewater treatment works

Screening Grit removal Primary Aerobic biological Final comprising Sedimentation treatment settling debris such Organic waste Harmful bacteria is destroyed as wet wipes sinks to the bottom. by good bacteria in aerated Remaining water is water tanks taken from top

Solids are Composting recycled Sludge

Combined heat Anaerobic digestion and power plant of sludge by bacteria Methane produced Treated wastewater during sludge process is returned to the environment burned for heat and Sludge electricity generation

Soil conditioner for agriculture

Methane Page 20 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 21

drain into the ditch network, and surface water Rising mains contain wastewater that is pumped Wastewater treatment works compliance 5.3 Wastewater service performance flows which run into the rifes. West Sussex under pressure from our wastewater pumping with permits County Council is responsible for managing We routinely monitor, analyse and report the stations. A burst will often result in pollution of and maintaining the highway drainage network. performance of our wastewater sewerage the environment or flooding. There have been As part of the wastewater treatment process, two rising mains bursts per year on average we must comply with permits issued by Sidlesham Wastewater Treatment Works networks and treatment processes to enable over the last five years in the Sidlesham the EA to release treated wastewater into serves approximately 10,500 properties in the us and our regulators to assess the service catchment. watercourses. For 2010–15, the Sidlesham villages of Almodington, Birdham, Bracklesham, provided to our customers and the impact of our activities on the environment. Wastewater Treatment Works was compliant Selsey, Sidlesham, West Itchenor, East and Pollution incidents with its permits. West Wittering. The treatment works is located Sewer blockages approximately 2km south-west of Sidlesham. Pollution incidents due to a failure of our Every year there are thousands of avoidable wastewater assets are reported to the EA. The inlet to the works receives wastewater blockages in our sewers caused by people The severity of the pollution is agreed and flows from pumped rising mains located at flushing the wrong things down the toilet or categorised as 1 (major), 2 (significant), 3 (minor) Crablands Selsey WPS, East Beach Selsey by pouring fat, oil and grease down the sink. or 4 (no pollution). WPS, Almodington Lane Earnley WPS, Chalk Sewer blockages can result in flooding to Figure 10 shows that there have been no Lane Sidlesham South WPS and Manhood Lane customers’ properties or pollution. Sidlesham WPS. Flow is discharged into the serious pollution incidents (Categories 1 and inlet screen chamber where screens remove Figure 9 shows that the number of blockages 2) in the Sidlesham catchment over the last non-biological items such as wet wipes. During recorded per km of public sewer in the five years. Following a peak in 2013, there has storms, excessive flow is diverted into two Sidlesham catchment has generally been close been a significant drop in Category 3 pollution storm storage tanks which have an overflow to the Southern Water regional average. In incidents in the last three years. should the storm tanks be filled to capacity. the Sidlesham catchment, 85% of blockages occurred in Selsey with a high proportion on The wastewater is pumped from the inlet Figure 10. Pollution incidents in the Sidlesham catchment works to primary settlement tanks. This is the High Street. We use high-powered water Pollution incidents in the Sidlesham catchment followed by biological treatment to break down jets to clear blockages and ensure our sewers 10 are running freely. In 2015, we launched our Category 1 Category 2 Category 3 organic matter and further treatment to reduce 9 nitrogen. ‘Keep it Clear’ campaign which involves teams visiting ‘blockage hotspot’ areas to educate 8 The final treated effluent is discharged into the customers on how to safely dispose of items. Broad Rife which, in turn, discharges into the 7 sea to the west of Selsey. Sewer collapses and rising main bursts 6 In some locations on the Manhood Peninsula, The Sidlesham DAP (Southern Water/MWH, 5 there are private sewage treatment plants or 2015) has identified seven sewer collapses 4 septic tanks which are not owned or maintained of public sewers in the Sidlesham catchment by Southern Water. over the last five years. We have an ongoing 3

programme to replace or refurbish ageing Number of pollution incidents 2 sewers at high risk of collapse. 1 0 Figure Blockages9. Blockages in in the the Sidlesham catchment catchment (public sewers only) 2012 2013 2014 2015 2016 1.0 Sidlesham SW Regional Average 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1

Number of blockages per km public sewer 0.0 2012–13 2013–14 2014–15 2015–16 2016–17 Page 22 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 23

6. Risks to wastewater services

We have assessed the future risks DAP growth needs and options Effect of growth on releases to the delivery of an effective and The hydraulic modelling in the DAP has During periods of intense rainfall, high volumes reliable service in the Sidlesham identified 12 new developments which would of surface water can quickly enter our sewers. wastewater catchment. Our risk create an unacceptable deterioration in the In these circumstances, we may have to carry assessment is based on a ‘do nothing’ performance of the network. A series of options out a controlled release of diluted screened have been assessed to improve the network wastewater from combined sewer overflows scenario where we do not carry out to accommodate this growth. In general, the or sea outfalls into watercourses, to protect any activity to reduce the risk. preferred options to meet growth needs in the properties from flooding. We monitor the catchment are similar to the flooding options number and duration of these releases against Table 8: Growth in wastewater connections in the Sidlesham catchment (Source: Office for National Statistics and local plan) and include: our consent for these overflows. We also have alarms to notify us of releases into sensitive Wastewater catchment Number of properties % change in properties connecting to our wastewater service from a • Reducing the amount of groundwater areas such as bathing or shellfish waters. connected to the 2015 baseline getting into the sewer network public sewers (infiltration reduction) Table 10 lists three consented network 2015 2020 2025 2040 overflows within the Sidlesham catchment and • Increased storage Sidlesham 10,500 approx. +2.3% +4.8% +11.6% a storm tanks overflow at Sidlesham WTW. • Expand sewer capacity and send a higher The DAP reports that none of these are volume of wastewater for treatment to the currently classed as ‘unsatisfactory’ by the For each new development, an assessment works by installing bigger, more powerful EA (Southern Water, 2015). 6.1 Growth pumps has been made on whether there is In addition to an increase in surcharged sewers Over the next 25 years, population growth sufficient capacity in the sewerage system to It should be noted that carrying out infiltration and flooding, the growth in new wastewater in the Sidlesham catchment is expected to accommodate the new wastewater connections reduction first would reduce the scope and connections can also result in an increase in result in a 12% increase in domestic properties to 2020 and 2040. This assessment is based on cost of capital schemes such as providing extra releases from overflows. In our DAP, we have connecting to our sewers as detailed in table 8. the modelled change in sewer surcharge and offline storage or upsizing sewers and pumps. modelled the increase in releases due to the flooding from manholes and whether there is forecast growth in new connections to the Costs are to be developed to enable a full an unacceptable deterioration in the hydraulic network as shown in table 10. 6.1.1 Network capacity for growth performance of the network. Table 9 shows the appraisal to be made of the options identified percentage of new wastewater connections in the DAP. These options would only resolve An assessment of the impact of growth on the which can be accommodated by the sewerage the forecast deterioration in sewer surcharge sewerage network has been carried out for the network without unacceptable deterioration and flooding back to 2015 levels and would not drainage area plan. To understand the impact in our wastewater service. This percentage remove the 2015 baseline flooding. of population growth, the forecast number should be considered an approximate value as The Sidlesham DAP action plan in appendix of new wastewater connections between it is dependent on the assumed location and 2015 and 2040 has been added to hydraulic B provides a summary of the growth issues size of developments. In addition, the results of in the catchment, proposed schemes to computational models of the sewerage system. hydraulic modelling are conservative to ensure The location of new connections over the next manage growth and the current status of these that we do not under predict the impact of both schemes. 25 years is unknown. However, from local flooding and growth. authority plans we know the potential locations Further long-term strategies are considered in and number of new connections over the next The sewerage network in the Sidlesham section 7.10 and appendix A. five years or so. Based on this, an informed catchment has sufficient capacity to judgment has been made on the location and accommodate only 53% of the forecast new number of new connections in the catchment to development over the next 25 years depending Table 10: Overflow releases due to the growth in wastewater connections in the Sidlesham catchment on location. This should not be seen as a 2020 and 2040. Annual % change in annual overflow constraint to development but as an indicator overflow releases from 2015 that investment may be required to meet Overflow Receiving water releases (m³) demand. Our customers have a right to connect to the sewerage network irrespective of 2015 2020 2040 Table 9: Network capacity for the growth in sufficient sewerage capacity. Where hydraulic Sidlesham WTW Storm Tank Broad Rife 56,134 +7.2% +18.2% wastewater connections in the Sidlesham catchment issues have been identified, we would look Year Assumed % of new to the application of planning conditions East Beach Road, Selsey English Channel (East Selsey) 34 +6% +6% number of new wastewater that require a customer to agree a suitable developments connections Crablands, Selsey Minor watercourse None 0% 0% which can be solution for drainage with ourselves or another accommodated supplier. If a connection is made under these Church Road, Selsey CSO Minor watercourse None 0% 0% circumstances then we will look to address 2020 12 30% the hydraulic issues in accordance with our 2040 19 53% prioritised investment programme. Page 24 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 25

Table 11. Network growth risk assessment for the Sidlesham catchment – a ‘do nothing’ scenario Table 13. Climate change risk assessment for the Sidlesham catchment – a ‘do nothing’ scenario

Wastewater catchment 2020 to 2025 2040 Comments Catchment 2020 to 2025 2040 Comments Sidlesham Medium Medium to high The Sidlesham sewerage network can accommodate approximately Sidlesham Low to medium Medium More intense storms and higher sea levels due to climate change 53% of the forecast new wastewater connections over the next are likely to have an effect on our sewerage network in the area. 25 years without an unacceptable deterioration in our wastewater service. Additional capacity could be delivered in parallel with development. Sidlesham WTW is operating at the limit of its – higher groundwater levels resulting DWF consent and it is likely that we will need in increased sewer infiltration by Network growth risk assessment treated (see glossary). The total population to apply to the EA to increase the dry weather groundwater and a potential increase in equivalent served by a works is primarily based flow consent at Sidlesham WTW in line with saline intrusion If we do nothing to accommodate the forecast on the permanent resident population in the the anticipated demand. However, based new connections to our sewerage network, – increased sea level preventing the free catchment but also includes non-permanent on flow data, it is estimated that groundwater table 11 shows the risk that this would create for discharge of surface water from outfalls. visitors to the region. Trade effluent generally infiltration comprises 37% of winter DWF and delivery of a reliable wastewater service in the makes up less than 1% of the load treated at 24% of summer DWF (Southern Water/MWH, An increase in temperature is likely to result Sidlesham catchment. •  the Sidlesham WTW and is less significant. The 2015). A reduction in infiltration may provide in: It is our statutory duty to provide the required population equivalent served by the Sidlesham sufficient headroom to accommodate additional – increased demand for water for drinking, sewer capacity for new developments as WTW is predicted to increase in line with the wastewater flows within the current DWF agriculture, horticulture etc they are built, and to protect our customers forecast growth in properties connected to the consent. and the environment from additional flooding public sewers. – demographic change (a redistribution of or pollution that could arise. We will work in population across the region due to water We have assessed the capacity of our process 6.2 Climate change collaboration with developers and the planning treatment assets at our Sidlesham WTW in stress) authority to understand the location and timing terms of the population equivalent load that Climate change is likely to result in changes in – increased microbial action and of new developments. However, we should can be treated. Sidlesham WTW is currently rainfall, sea level and temperature. Southern only deliver new capacity where there is a consequential increase from H2S attack operating at the limit of its treatment capacity. Water has recently assessed the risks from on sewers and mains demonstrable need to deliver this for growth. It is likely that an increase in treatment capacity climate change and identified actions to reduce Developer contributions may be required in will be required in line with the anticipated them in our report on ‘Adapting to Climate – a potential detrimental effect on line with the regulatory framework for the water demand. As part of our business plan for Change 2015’ (Southern Water, 2015). The wastewater treatment processes industry. 2015–20, we have plans to boost the treatment report found the following: – ground movement that can damage capacity at Sidlesham WTW when there is • Less rainfall is likely to result in: sewers and other wastewater assets 6.1.2 Treatment capacity for growth certainty that new developments will be constructed. – increased demand for water for – potential increased impact on receiving Process treatment growth is the increase in agriculture, horticulture, gardening etc waters due to lower river flows. hydraulic (water) and organic load, which may Dry Weather Flow (DWF) – longer dry periods and potential for Based on advice by the EA (2010), the increase require additional investment at wastewater Wastewater treatment works are issued with increased blockage rates in sewers. in extreme rainfall intensity by the 2050s is treatment works to maintain existing levels a discharge consent to limit pollution of the predicted to be 5%, 10% and 20% for lower, of service to customers and to protect the watercourse receiving the treated effluent. • Increase in extreme rainfall intensity is likely average and upper forecasts respectively. environment. We measure growth in terms of The EA sets DWF consents for each works to result in: When assessing network capacity for new the predicted rise in ‘population equivalent’ which are based on the flow of the receiving – surcharging of combined/surface water developments or schemes to relieve hydraulic and ‘dry weather flow’ (DWF). Our statutory watercourse being at its lowest after a long overloading, Southern Water uses an upper obligation is to allow timely connection of sewers which can result in flooding of period of dry weather. After a dry period, the properties forecast of a 20% increase in extreme rainfall new developments and ensure we maintain treated effluent will have minimal dilution and to model the affect of climate change. We will compliance with the works’ permit conditions. maximum potential pollution impact on the – increase in controlled releases from work in collaboration with developers and combined sewer overflows potentially Population equivalent receiving watercourse. We monitor the DWF planning authorities to ensure that the risk and report any breaches of the DWF consent affecting bathing/shellfish water quality caused by climate change is not a constraint to The capacity of a sewage treatment works conditions to the EA. – direct flooding of critical assets at new development. is measured in terms of the ‘population wastewater treatment works and Climate change is generally considered equivalent’ served by the works and is based pumping stations on the amount of organic material that can be to create a medium risk to the long-term – loss of power supply, logistic and performance of our wastewater services in the transport difficulties caused by extreme Manhood Peninsula. This is due to the following weather. reasons: Table 12. Process growth risk assessment for the Sidlesham catchment – process growth risk assessment for a ‘do nothing’ scenario • A sea-level rise is likely to result in: • An increase in intense storms will result Wastewater catchment 2020 to 2025 2040 Comments in more surface water run-off which we – direct flooding of customers’ properties, Sidlesham Medium to high High Sidlesham WTW is currently at its treatment capacity and is likely already know is a cause of historic flooding to require an increase in population equivalent capacity and DWF wastewater treatment works and issues in the area. consent in line with the anticipated growth in new connections. pumping stations Page 26 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 27

Table 14. Urban creep risk assessment for the Sidlesham catchment – a ‘do nothing’ scenario Table 15. Asset deterioration risk assessment for the Sidlesham catchment – a ‘do nothing’ scenario

Catchment 2020 to 2025 2040 Comments Catchment 2020 to 2025 2040 Comments Sidlesham Low to medium Medium The area is mainly rural but urban creep will occur due to new Sidlesham Low to medium Medium An average % of long-life vitrified clay sewers and a below average development and extensions of existing properties. % of short-life pitch-fibre sewers.

An above average % of PVC rising mains laid in the 1970s are at risk.

• New developments will increase the In Southern Water’s design standards, we impermeable area in the catchment and currently allow for creep in new properties of For the purposes of this drainage strategy, surface water run-off entering the sewers. 0.4 square metres per year per property up to a we have carried out an assessment of the 6.5 Infiltration maximum of 4 square metres per property. This age and material types of sewers and rising Infiltration of groundwater into sewers generally • The projected rise in sea-level would allowance for creep is currently under review. result in more tide-locking of outfalls and mains to be found in the Sidlesham wastewater occurs through cracks or joints. In areas discharges from the land drainage system There is some uncertainty regarding the catchment. This has been compared with where the groundwater level is high following which would cause the back up of flows in relationship between urban creep and the the sewerage system in the county of West prolonged rain, then groundwater infiltration the rifes and potential flooding. volume of surface water run-off entering the Sussex and the entire Southern Water region can be significant and fill the sewers to their sewerage system. Further work is required to which also includes Hampshire, East Sussex, capacity which can cause restricted toilet use • Tidal flooding risk is likely to increase due to understand this relationship and to model the Kent and the Isle of Wight. This enables us to or sewer flooding of properties. higher sea levels and the low lying nature of effect of urban creep on network models. identify any particular risks in these catchments the peninsula. and whether there will be a requirement for In recent winters, groundwater infiltration has Urban creep is considered to create a medium significant investment to manage risks due to caused significant issues to our customers • Higher sea levels would also increase risk to the long-term performance of our sewer deterioration. in a number of villages across Hampshire, groundwater levels that could result in more wastewater services in the Manhood Peninsula. Sussex and Kent. In West Sussex, these include infiltration. This is due to the following reasons: In general, we have found that the risk of villages in the Lavant Valley to the north of deterioration of our infrastructure assets • The uncertainty in the effects of climate Chichester and Maudlin and Westhampnett • The area is predominantly rural with a affecting long-term performance is generally change makes it difficult to predict the to the east of Chichester. In many areas, it has low density of properties that could be a medium risk in the Sidlesham catchment potential impact on, and degree of risk to, been necessary to protect our customers from extended. compared with other areas of the Southern our sewerage system. flooding by removing additional groundwater • New developments in the region will Water region. This is due to the following flows from our sewers by tanker or over- increase the impermeable area in the reasons: pumping dilute screened wastewater into 6.3 Urban creep catchment with more potential for further • An average percentage of vitrified clay watercourses. urban creep as homeowners improve their ‘Urban creep’ describes the gradual change of sewers which have high integrity and long Our DAP study has identified that the Sidlesham properties. permeable land areas to impermeable areas life. catchment suffers from significant groundwater within the urban environment. Typical ‘urban Southern Water will work in collaboration with • A below average percentage of pitch fibre infiltration (Southern Water/MWH, 2015). During creep’ activities include new developments, developers and planning authorities to ensure sewer pipes which have a short life. the winter, sewers can remain surcharged for the creation of impermeable hard-standings that the risk caused by urban creep is not a long periods between rainfall events. Based for vehicles in front gardens, the laying of constraint to new development. • An above average percentage of asbestos on flow data, it is estimated that groundwater patios in back gardens or the building of house cement pipes which have a limited life. infiltration comprised 37% of winter DWF and extensions and conservatories. The resulting 24% of summer DWF to the treatment works 6.4 Asset deterioration • An above average percentage of PVC rising loss of permeable land in urban areas results mains laid in the 1970s. PVC pipes have a (Southern Water/MWH, 2015). in more rainwater and surface water run- The deterioration of our wastewater assets is short life and are vulnerable to bursts. In the village of Sidlesham, groundwater off entering the surface water or combined an ongoing risk to the wastewater service we • The sewers in the Sidlesham catchment infiltration of the sewerage network has drainage system. This increases the risk that provide to our customers both now and in the were laid in the 1970s on average, which resulted in six incidents of external flooding and the capacity of the drainage system will be future. These assets include pumps, process compares to the 1950s as the average six incidents of restricted toilet use between exceeded during storms with an increased treatment equipment and all mechanical and laying date across the entire Southern 2000 and 2016. During the winter of 2013–14, potential for flooding or pollution. electrical equipment. It also includes the Water region. the wettest winter on record, flows in the Research has found that urban creep is related sewers and rising mains which deteriorate over sewers exceeded their capacity in Sidlesham to the density of housing in an area (Allitt & time depending on the material type and age, and unfortunately it was necessary to make Tewkesbury, 2009). For low to medium density the soil type etc. discharges from the sewers to the local housing, the average urban creep would be We reduce the risk of asset deterioration approximately 0.8m²/house/year for detached by identifying which assets will require Table 16. Infiltration risk assessment for the Sidlesham catchment – a ‘do nothing’ scenario housing and 0.4m²/house/year for semi- maintenance, refurbishment or replacement detached housing. For high density housing in the short, medium and long term. We use Catchment 2020 to 2025 2040 Comments such as terraced houses, which have smaller deterioration modelling which is a risk-based Sidlesham Medium Medium to high Sources of infiltration in the Sidlesham catchment have been gardens, the average urban creep would be system that identifies optimal future investment identified and repaired. Based on flow data, there are likely to be approximately 0.15 to 0.2m²/house/year. to achieve a specified level of service at other areas which require infiltration reduction. There is a risk that further deterioration of the sewers may result in future groundwater least cost. infiltration. Page 28 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 29

Table 17. Per capita consumption for the Portsmouth Water region Table 18. Clean water consumption risk assessment for the Sidlesham catchment – a ‘do nothing’ scenario

Portsmouth Water region 2015 2020 2025 2040 Catchment 2020 to 2025 2040 Comments

Per capita consumption (PCC) (litres/head/day) for a dry year (annual Sidlesham Low Low PCC is forecast to reduce with a corresponding reduction in 157 155 152 149 company average) wastewater.

Percentage change in PCC from 2015 -1% -3% -5% It should be noted that the Southern Water The introduction of the Water Framework region has a lower forecast PCC (144 l/h/d Directive has established a strategic approach watercourse to maintain sewerage services to The removal of groundwater infiltration from the in 2020 and 138 l/h/d in 2040) than the to managing the water environment. It takes Southern Water customers. network has the following benefits: Portsmouth Water region. This is mainly a common approach to setting environmental In areas where high infiltration has caused • Protection of customers’ properties and due to Southern Water’s universal metering objectives for groundwater, dependent flooding or restricted toilet use, we carry out: public areas from sewer flooding programme which has resulted in more wetlands and surface water bodies. It also than 90% of households being metered. If manages compliance with standards and • CCTV sewer surveys • Reduction in the scope and cost of solutions a similar level of metering is achieved in the objectives for protected areas and the to resolve flooding issues due to hydraulic • ‘lift and look’ manhole surveys Sidlesham catchment then there is scope for a implementation of programmes to meet those overloading (eg smaller offline storage further reduction in PCC which would reduce objectives. monitoring of flows including comparison to tanks) •  wastewater flows. A reduction in PCC would borehole data on groundwater levels To understand current and future legislation • Increased capacity in the foul and combined also free up capacity in the sewerage network and policies, Southern Water liaises closely techniques for infiltration investigations (eg sewer network and treatment works which to acccommodate the predicted growth in •  with agencies including the Environment electrical resistance techniques) can be used to accommodate additional wastewater flows from new developments. Agency (EA), Department for the Environment, wastewater flows due to the growth in sewer rehabilitation or replacement Food and Rural Affairs (Defra) and the Drinking •  connected properties Water Inspectorate (DWI) who are responsible sealing/repairs of sewers and lateral 6.7 Environmental legislation •  • Increased capacity in combined sewers for developing and implementing legislation in connections to accommodate additional surface water Over the last 25 years, the UK water the UK. This provides us with a view of potential In 2013, we surveyed approximately 1.4km of flows due to more intense storms resulting environment has been significantly improved changes to legislation in the short to medium sewers for groundwater infiltration in Sidlesham from climate change through the introduction of tightened term. For the long-term, 25-year view, it is and consequently repaired 170m of sewer in the environmental legislation implemented difficult to predict changes in legislation that • Reduction in pumping and treatment costs Fletchers Lane/Rotten Row area of the village. by the UK government and the European would need to be considered in this drainage which affect customers’ bills We have recently carried out some sewer Commission. For example, the environment strategy. Southern Water will work in collaboration with has been protected from the adverse effects sealing in Itchenor to reduce infiltration. Where required to meet more stringent developers and planning authorities to ensure of discharges of urban waste water through the The EA’s Regulatory Position Statement environment legislation, Southern Water will that the risk caused by infiltration is not a Urban Waste Water Treatment Directive (91/271/ (Environment Agency, 2014) requires water seek investment to improve the quality of constraint to new development. EEC) introduced in the early 1990s. This has and sewerage companies who are aware resulted in cleaner seas and bathing waters in the effluent through traditional or alternative of sewerage systems in their area that are our region. solutions and at the same time allow new vulnerable to infiltration, to submit infiltration 6.6 Clean water consumption development to connect to our services in line reduction plans (IRP) to the EA for approval. with our statutory obligations. An IRP has been prepared for Sidlesham and The volume of wastewater in the sewerage was submitted to the EA for approval in the system is directly related to the volume of summer of 2016. clean drinkable water supplied for domestic, Table 19. Environmental legislation risk assessment for the Sidlesham catchment – a ‘do nothing’ scenario business, industrial, agricultural and The Sidlesham IRP is not yet ready for general horticultural use. In general, we assume that Catchment 2020 to 2025 2040 Comments publication but it will be similar to the IRP for St 92.5% of the clean water supplied to a domestic Sidlesham Low to medium Medium Southern Water will seek investment to comply with changes in Mary Bourne near Andover which can be found property is disposed of as wastewater through environmental legislation where applicable. at www.southernwater.co.uk/st-mary-bourne- the sewerage system. The remaining 7.5% is infiltration-reduction-plan. used for watering the garden, car washing, etc. Southern Water has invested £14 million Portsmouth Water supplies clean water to between 2013 and 2016 to improve the the Manhood Peninsula. The average water performance of the sewer network in the consumption per person in the region is 60 towns and villages affected by high called ‘per capita consumption’ or PCC. Based groundwater levels across the company’s on the Water Resources Management Plan region. Due to the number of villages affected (Portsmouth Water, 2014), table 17 shows by groundwater infiltration issues, we prioritise that PCC is forecast to reduce across the the catchments that require infiltration Portsmouth Water region over the next 25 reduction plans, sewer investigations and years. This is due to water efficiency measures repairs. and customers opting for a water meter. Page 30 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 31

7. Strategic assessment

The plan is built around the delivery of In the medium term (five to 10 years) and long 7.1 Outcomes for the Sidlesham six outcomes which our customers and term (10 to 25 years), our outcomes have catchment (Manhood Peninsula) stakeholders told us were their priorities. been developed during the preparation of Our Five-year Business Plan 2015 to 2020 For each outcome we have developed a clear outcome delivery strategies for key promises (Southern Water, 2013) sets out details of the set of promises that detail what we will achieve and outcomes. In table 20, we have identified improved water and wastewater services we for our customers. Three of these outcomes are the outcomes for the Sidlesham catchment to will provide in the future. It was developed relevant to the Drainage Strategy for Sidlesham be achieved by 2020, 2025 and 2040. These as a result of the company’s biggest ever (Manhood Peninsula) and are shown in figure include generic outcomes applicable to the consultation programme which included 11 alongside the relevant promises associated entire Southern Water region and outcomes feedback from more than 34,000 customers with them. specifically related to the drainage issues and stakeholders. identified for the Sidlesham catchment.

Figure 11. Outcomes of relevance to the Drainage Strategy for Sidlesham (Manhood Peninsula) Table 20. Key outcomes for the Sidlesham catchment (Manhood Peninsula) Year to achieve Minimise Minimise Minimise Maintain Improve Clean seas key outcome flooding due to flooding due pollution from compliance at water bodies (bathing waters) Removing wastewater Looking after Better information wastewater to surface wastewater wastewater (groundwater, water and treatment works river, estuarine effectively the environment and advice groundwater and shellfish waters)

• Minimising flooding from our • Minimising wastewater pollution • Improved advice on how to 2020 Reduce internal Complete Aim for zero Maintain Aim to achieve Maintain current sewers with a 25% reduction in so that by 2020 there will be prevent blocked drains to help sewer flooding agreed actions Cat 1 & 2 population ‘good’ status for ‘excellent’ internal sewer flooding incidents no serious (Category 1 & 2) reduce blockages incidents by for Southern pollution equivalent all water bodies classification of by 2020 pollution incidents caused by our 25% and no Water in the incidents and compliance at by 2021 or 2027 bathing waters increase in Manhood reduce Cat 3 99.9% or above in partnership in the region and operations. We are also aiming • No increase in the number of external flooding Peninsula incidents by and numeric with others improve Selsey to halve the number of minor incidents of sewer flooding incidents Surface Water more than half compliance at bathing water to (Category 3) incidents from 2017 Management 97.7% or above ‘excellent’ affecting outside areas onwards Plan • Maintaining stable asset health • Maintaining wastewater 2025 Reduce internal Minimise Aim for zero Aim for 100% Aim to achieve Maintain current which includes our performance treatment works compliance by and external flooding due to Cat 1 & 2 compliance ‘good’ status for ‘excellent’ for sewer collapses and external sewer flooding surface water pollution all water bodies classification of ensuring that any releases to the flooding due to other causes incidents further and groundwater incidents and by 2021 or 2027 bathing waters environment comply with permit in collaboration reduce Cat 3 in partnership in the region • No increase in the number of conditions with our incidents further with others and potentially blockages in our sewer network drainage improve others • Maintaining ‘excellent’ bathing partners to ‘excellent’ • A 5% reduction in complaints water quality and improving about smells from our other bathing waters 2040 Aim for zero Minimise Aim for zero Aim for 100% Aim to achieve All designated wastewater treatment works and internal and flooding due to Cat 1, 2 & 3 compliance ‘good’ status for bathing waters external sewer surface water pollution all water bodies in region to meet pumping stations by 2020 flooding and groundwater incidents in partnership the ‘excellent’ incidents in collaboration with others classification with our drainage partners Page 32 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 33

7.2 Key outcomes at risk 7.3 Strategies: Business In section 6, we assessed the current and as usual activities future risks to the delivery of an effective We carry out ‘business as usual’ activities to and sustainable wastewater service in the identify and reduce risks to delivery of our short Sidlesham catchment. In table 21, we have and medium term outcomes as detailed in table assessed these risks against delivery of our key 22. outcomes if we do nothing.

Table 22. Business as usual activities to manage risk Table 21. Key outcomes at risk in the Sidlesham catchment (Manhood Peninsula) if we do nothing Future risk Identification and assessment of risk Activities to reduce risk Key outcome Risk of not delivering the Comments outcome by; Growth Working closely with planners and developers Where there is an identified need, deliver the to understand the location and timing of new required network and treatment capacity to 2020-25 2040 developments accommodate growth. Developer contributions may be required in line with the regulatory framework for Forecasts of growth at catchment level based on Maintain compliance Medium High Sidlesham WTW is currently operating at its treatment capacity and is likely the industry data from local plans and the Office for National at wastewater to high to require an expansion of treatment capacity and DWF consent in line with Statistics treatment works the anticipated growth in new connections. Additional capacity could be delivered in parallel with development. Hydraulic modelling of the impact of growth on our wastewater service Minimise flooding Medium Medium The Sidlesham network can accommodate approximately 53% of the forecast due to wastewater to high new wastewater connections over the next 25 years without an unacceptable Climate change and Review published research and participate in When upgrading the network to accommodate deterioration in our wastewater service. Additional capacity could be urban creep industry research projects growth, make an allowance for an uplift in extreme rainfall intensity due to climate change delivered in parallel with development. Partnership-working on surface water management plans and flood risk management strategies Minimise flooding Medium Medium Groundwater infiltration is considered to be significant across the catchment due to surface water to high and has been an issue in the village of Sidlesham where repairs have been Hydraulic modelling of the impact of additional and groundwater carried out. Groundwater levels may get higher as a consequence of rising surface water flows sea levels due to climate change. Asset deterioration Modelling of asset deterioration to optimise Maintenance programmes to repair, refurbish or Surface water flooding has been a significant issue due to the limited capacity maintenance programmes replace sewers, rising mains, pumping station or of the land drainage system. Flooding is likely to increase due to more intense process equipment storms caused by climate change and more run-off due to urban creep. Infiltration Survey of networks with known infiltration issues in Sealing of sewers and manholes to minimise the catchment infiltration in catchments with known issues Minimise pollution Low Low to The number of pollution incidents in 2015 and 2016 were relatively low. The medium likelihood and severity of pollution incidents may increase due to additional Preparation and implementation of infiltration wastewater, surface water and groundwater in the sewerage system. reduction plans Clean water Measurement and assessment of per capita Provision of water meters to 92% of Southern Improve water Medium Medium Nine out of 11 water bodies on the Manhood Peninsula are predicted to consumption consumption (PCC) in each Water Resource Zone Water customers through the Universal Metering bodies (river, achieve ‘good’ status by 2027 with the remaining two at ‘moderate’ status. Programme lake, coastal Partnerships will be key to achieving the higher environmental standards groundwater) required under the WFD. Forecasts of PCC Education of customers on water efficiency Environmental Close liaison with the Environment Agency, Identification and implementation of schemes to Maintain ‘excellent’ Low to Low to Three out of four bathing waters in the region have generally ‘excellent’ legislation Department for Environment, Food and Rural Affairs, meet our statutory obligations under the EA National bathing water medium medium bathing water quality. At Selsey, we are working with partners to improve Drinking Water Inspectorate on environmental Environment Programme quality bathing water quality to ‘excellent’ by 2019–20. legislation and policy Review of EU and UK government legislation on Upgrade of wastewater treatment assets to meet the environmental issues requirements of environmental legislation The risk assessments in section 6 and table 21 were based on a ‘do nothing’ scenario. However, these risks will be identified, assessed and reduced through our ‘business as usual’ activities which are detailed in section 7.3. Page 34 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 35

7.4 Strategies: Least whole 7.5 Strategies: Innovation 7.6 Strategies: Sustainable life cost approach A key driver for improving our capabilities is the drainage systems The risks to delivery of our key catchment use of innovative techniques. Between 2015 Sustainable drainage systems (SuDS) can be outcomes (objectives) can be reduced by and 2020, we will be investing significantly used to manage the quantity of surface water traditional solutions to upgrade the sewerage in research and development to investigate run-off from new and existing developments in network or wastewater treatment works. and implement innovative techniques that a natural way by replicating natural processes. However, the cost of traditional solutions can will enable a significant improvement in our The implementation of SuDS can have a be high and the benefits may be limited. capabilities and performance. significant impact on reducing the peak flows of To deliver our outcomes, we will always seek We will be bringing leading edge new surface water being discharged through drains to implement the least whole life cost solution approaches and technology to operational and sewers following intense rainfall. The such as elimination or education before we use. We will also develop solutions to primary benefits from the use of SuDS include: carry out more expensive activities such as support outcome delivery strategies and our • reduced flooding risk from surface water fabrication as illustrated in table 23. technology roadmap. Our innovation priorities include the following: • reduced surface water in combined sewers which releases capacity for wastewater Table 23. Strategies to achieve outcomes at least whole life cost • Real time control systems (RTS) to monitor flows Strategy Definition Examples the sewerage network (sewer/wet well levels and flow) to detect blockages, • reduced carbon emissions and energy Investigate Understand better ways to achieve improved outcomes Impact of climate change, improvements in growth collapses, equipment failures and hydraulic costs due to less pumping and wastewater or reduce the whole life cost planning, use of ‘big data’, investigations for the overloading. Alarms will provide warning treatment National Environmental Programme, opportunities for CSO removal, measurement of infiltration to control centres and intelligent systems • reduced ‘urban heat island’ effect can automatically control flows to prevent Eliminate Remove the root cause Surface water separation, Integrated Water Cycle flooding. Real time control systems could • improved water quality of water bodies Management (IWCM), sustainable drainage systems also be used to manage high flows during due to reduced diffuse urban pollution and (SuDS), improved targeting of blockages in sewer combined sewer overflow (CSO) releases jetting programme storm events and enable the transfer of flows to areas with available capacity. • the recharging of aquifers in water-stressed Engage and educate Change behaviours to reduce demand for improved Educate customers on fat, oil and grease (FOG) and wet areas such as Southern England service levels wipe disposal, identification of misconnections, trade • Network modelling and optimisation effluent control, reduce diffuse agricultural pollution and predictive analytics to drive more • the enhancement of urban spaces to through engagement with landowners and diffuse responsive management and better improve the quality of life for local residents urban pollution by engagement with customers and targeted intervention to reduce the local authorities frequency of asset and service failure and • increased biodiversity. Optimise Operational or maintenance solution to extend asset Optimal operational maintenance with capital improve resilience to extreme events. life/ improve performance maintenance, optimisation supported by fault cause There are a range of SuDS techniques that analysis • Plant and process optimisation to reduce are suitable for various ground conditions, topography etc. Infiltration SuDS techniques Leverage of asset capability and unused headroom Real time network control, reconfiguration of works the use of power and chemicals, lower control/ process, flood reduction measures costs and improve water and wastewater allow the surface water to infiltrate the compliance. ground in a controlled manner, reducing the Management action to reduce risk/improve Lean processes, standards, risk management, capability, risk of surface water flooding. Examples of performance swifter response to failures • Energy efficiency and renewables to infiltration SuDS techniques include filter Work in partnership Partnership with others, finding synergies to meet Drainage Strategies, SWMPs, flood management plans, reduce our carbon footprint and energy strips, permeable pavement, soakaways, overall service infiltration reduction plans, improving bathing waters in costs. conjunction with others swales (shallow channels which lead surface • Recovering value from wastewater by water overland away from the drained surface Fabricate Design and construct new assets Lean design and build of physical assets seeing wastewater as a potential resource to storage or a different point of discharge), rather than as waste. infiltration basins and wetlands. Alternative long-term strategies such as the use • Integrated Water Cycle Management In some areas, infiltration techniques are not of innovation, sustainable drainage systems, (IWCM) to provide strategic direction in the suitable due to pollutants in the surface water surface water separation and integrated water management of water and environment or soil, high groundwater levels or unavailability cycle management are described in Sections pressures through strong partnership of land for swales or wetlands etc. There are 7.5 to 7.8 respectively. working and collaboration. other SuDS techniques which involve non- infiltration or attenuation (temporary storage of surface water) such as green roofs, rainwater harvesting, water butts, detention basins and underground storage tanks. Page 36 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 37

There are no Groundwater Source Protection Between 2012 and 2014, Southern Water Zones in the Manhood Peninsula apart from invested £20 million in a surface water 7.9 Strategies: Integrated 7.10 Strategic assessments for the a small Zone 1 (inner) which is just south of separation scheme in Portsmouth. The project Water Cycle Management delivery of key catchment outcomes Fishbourne. However, it has been identified has been successful and has reduced the risk The South-East faces a number of challenges Table 24 summarises the key outcomes that that high groundwater levels in the area are of sewer flooding for thousands of properties including water stress, stringent environmental have been identified as requiring a strategic likely to be preventing surface water flows from and businesses in the city. needs, high population growth, and a risk of approach to reduce the risk. We are currently discharging to ground through soakaways. drought or flooding and climate change. To assessing a range of traditional engineering Therefore, infiltration SuDS techniques may not 7.8 Strategies: Removal meet our long-term challenges, Southern Water and alternative strategies to reduce these be suitable in parts of the Manhood Peninsula. needs to develop a more integrated approach risks which are listed in table 24. The strategic As an alternative, the discharge of surface water of misconnections to managing the water environment. We will assessment is based on a SWOT (strength, to non-infiltration SuDS options or watercourses Illegal connections of surface water drainage work across the whole water cycle rather than weakness, opportunities, threats) analysis is considered more appropriate than a discharge to foul sewers can cause hydraulic overloading seek individual solutions that only address where each strategy has been assessed under to combined sewers. of sewers during heavy storms or prolonged specific environmental aspects in certain the following criteria, described in more detail A land drainage study of the Manhood Peninsula rainfall. Foul drainage can also be illegally geographical areas. This is an innovative in table 27 of appendix A: approach and will show leadership in the (Royal Haskoning for Chichester District Council, connected to surface water sewers which flow These are: 2006) concluded that: into watercourses or into the ground without region. Greater collaboration and working with treatment and consequently cause pollution. third parties, as well as enhanced technical • Residual risk • The viability of using SuDS on the peninsula understanding, will be required to realise the Whole life costs (capital and operational as a method for reducing existing problems is These misconnections can occur during the expected benefits. •  limited due to the difficulty of retrofitting. construction of new developments or when expenditure) extensions or improvements are made to Integrated water cycle management (IWCM) • SuDS would be effective and should be • Environmental impact properties. It is the responsibility of local recognises that issues related to water are included in all future development whatever authorities to monitor construction to prevent complex and that the main causes of negative • Input required from other stakeholders the scale. The inclusion of SuDS techniques misconnections and to enforce private impacts are inter-linked. IWCM requires the should be viewed as a valuable asset to any • Other constraints individuals to rectify their drainage. integration of all elements of the water cycle development. such as water resources, water use, natural • Programming Southern Water can work collaboratively • Suitable ongoing management and water processes and treatment of wastewater. with local authorities, construction firms and • Uncertainty. maintenance of SuDS are essential to their property owners to reduce misconnections Between 2015 and 2020, we will pilot IWCM in continued effectiveness and therefore future Tables 28 to 31 in appendix A provide the through: two catchments in Kent and West Sussex with responsibilities must be fully agreed at the a combined catchment area of over 3,200 km², detailed assessment for each of the strategies time of implementation. • collaborative inspection teams with local 108 wastewater treatment works and over 130 to reduce the key outcomes at risk. authorities water bodies. These catchments have been 7.7 Strategies: Surface water • post-construction sewer flow monitoring selected on the basis of the environmental circumstances, a mix of stakeholders and separation • educating property owners, local building responsibilities and representation of varied firms etc In the Victorian age and the first half of the 20th water cycle challenges. We will be identifying century, most sewers were designed to carry • providing rainwater harvesting equipment world-wide best practice and emerging wastewater and surface water run-off together in such as water butts. methodology including catchment management combined sewers. During storms, the rainwater and restoration, sensitive urban design, surface in combined sewers can be up to 25 times the water management, wastewater re-use, volume of wastewater which is carried in all changes in customer behaviour and adopting weathers. Extreme rainfall intensity increases the new technology. By 2040, we intend to be risk of dilute wastewater flooding, pollution or operating a fully integrated water environment overflows from combined sewers. and working seamlessly with all water users. In more modern developments, separate networks have been provided for wastewater and surface water. In areas with a high density of combined sewers, it is possible to separate some of the surface water from the wastewater by providing a separate surface water network. However, retrofitting a new surface water sewerage system in an urban environment is expensive and may require the construction of new pumping stations and outfalls to watercourses. Page 38 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 39

8. Next steps

Table 24. Key outcomes at risk and potential solutions for the Sidlesham catchment (Manhood Peninsula) The Drainage Strategy Framework It is proposed that the development and (Environment Agency et al., 2013) implementation of this drainage strategy will Detailed follow the timeline shown in figure 12. This will strategic recommends a four-stage planning Key outcomes at risk Risk Potential strategies enable the strategy to be in line with the water assessment in process when preparing a drainage industry’s regulatory framework that requires Appendix A strategy as discussed in section 2. each water company to submit an investment • Collaboration with the local authority and developers to business plan to Ofwat for a price review on a Insufficient headroom understand the timing, size and location of developments in treatment capacity The Drainage Strategy for Sidlesham five-yearly cycle. with planning certainty and dry weather Maintaining compliance with • Reduce groundwater infiltration of foul sewers (Manhood Peninsula) is currently at stage 3 flow consent to Table 28 When preparing business plans, we undertake permits at our treatment works • Provide additional treatment capacity at the works as (options appraisal) and we are consulting with accommodate growth surveys of our customers to determine their required in excess or ahead of customers and key stakeholders in the region priorities. This could be clean drinking water, • Transfer wastewater to other treatment works with spare our forecast to identify and agree: capacity cleaner beaches, sewer flooding etc. As part • current drainage issues, future risks and of the survey, customers are asked how much • Collaboration with the local authority and developers to shared outcomes for the region they would be willing to pay to improve these understand the timing, size and location of developments Insufficient network service levels. All schemes to enhance the with planning certainty capacity to • potential strategies to reduce risk in the • Upsize foul/combined sewers, pumps and rising mains as existing level of service afforded by sewerage accommodate forecast short, medium and long-term Minimising flooding and required systems are subject to cost-benefit analysis. new wastewater Table 29 pollution due to wastewater • Reduce groundwater infiltration of foul sewers In determining the cost-benefit of individual connections due to • a preferred strategy to achieve the • Transfer wastewater to other treatment works with spare growth in excess or schemes against the results of the ‘willingness capacity outcomes required by Southern Water and ahead of our forecast to pay’ survey, analysis is undertaken • Construct offline storage tank/s to attenuate high flows key stakeholders • Reduce surface water flows in combined sewers to determine the monetary benefit of • actions to be carried out by Southern Water improvements (eg reducing flooding risk results and key stakeholders which will be added to • Remove misconnections of surface water to foul sewers in less damage to properties and cleaning up) Insufficient • Maintain public sewers, highway drains and land drainage the action plan provided in section 9. in comparison with the cost of delivering that network capacity system to accommodate improvement. • Upsize surface water/combined sewers and pumps as Minimise flooding and pollution groundwater required due to surface water and infiltration and surface Table 30 • Construct offline storage tank/s to attenuate high flows groundwater water flows which Figure 12. Timeline for development and implementation of a drainage strategy • Installation of sustainable drainage systems may increase due to • Separation of surface water from foul water in combined climate change and sewers urban creep • Reduce groundwater infiltration of sewers 2016 to 2017 2017 to 2018 2020 to 2025 2021 to 2023 Improving water bodies to • Implementation of integrated water cycle management Stakeholder Investment Investment ‘good’ status by 2021 or 2027 and working with external stakeholders to reduce the Review the and improving bathing waters Diffuse and point pollution of water bodies engagement Planning Delivery Drainage Strategy urban and rural Table 31 • Minimise pollution due to additional wastewater, surface Maintain ‘excellent’ bathing pollution Discuss the risks and In line with the pre- Deliver the approved Review the current water and groundwater flows using the potential strategies waters solutions. Agree a ferred strategy and schemes/strategy described above strategy and realised preferred strategy following customer benefits. Review consultation, de- potential changes velop cost-beneficial to the strategy. schemes to be includ- Further stakeholder ed in Southern Water’s engagement. Prepare business plan for 2020 the strategy for the to 2025 to next investment be submitted to Ofwat planning stage for approval Page 40 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 41

9. Action plan 10. Glossary of terms

Table 25. Action plan for the Drainage Strategy for Sidlesham (Manhood Peninsula) Table 26: Glossary of terms No. Action Lead Supporting Due date Action delivery status Term Description action action owners The process of retaining water on site and slowly releasing it in a controlled discharge to a surface water or Attenuate owner combined drain or watercourse.

1 Through the drainage SW WSCC, EA, End of 2016 A draft drainage strategy was issued to external stakeholders in Large and complex external data sets that can be analysed to provide information that may not be available from Big data strategy, identify current CDC November 2016 for comment and discussion. Feedback has been routine company performance data. drainage issues, key risks, received from WSCC, CDC and the EA during the winter of 2016–17. Combined sewer/ shared outcomes and Enables a release of wastewater and storm water into a watercourse or the sea to protect properties from potential emergency overflow potential actions flooding. (CSO/CEO) 2 Publish the drainage SW All Following The drainage strategy will be updated with feedback from external Defra Department for Environment, Food and Rural Affairs. strategy on the stakeholders receipt of stakeholders before publication. Southern Water website comments A water-company held register of properties which have experienced sewer flooding due to hydraulic overload, or DG5 Register from external properties which are ‘at risk’ of sewer flooding more frequently than once in 20 years. stake-holders Customers and other stakeholders will have the opportunity to provide feedback on the final drainage strategy. Drainage Area Plan Modelling of wastewater catchments to identify hydraulic overloading and other issues due to new developments, (DAP) climate change etc. The DAP provides outline solutions to resolve flooding issues and accommodate growth. 3 Improve Selsey’s SW WSCC, EA, 2019–20 In May 2017, Selsey was named as one of seven bathing waters to Drainage Strategy Long-term (25-year) strategies to provide a reliable and sustainable wastewater service in a catchment while bathing water quality CDC be improved to ‘excellent’ as detailed in the action plan for the Framework (DSF) accommodating growth, climate change and improving water bodies, bathing and shellfish water quality etc. to ‘excellent’ bathing water. Dry Weather Flow The average daily flow to a wastewater treatment works during seven consecutive days without rain. 4 Review the needs and SW WSCC, EA, End of 2017 In March 2015, a meeting was held with external stakeholders to (DWF) options identified in CDC identify risks in the Sidlesham catchment to inform the DAP. the Sidlesham DAP Structural, operational, growth, flooding and environmental needs EA Environment Agency. and potential options have been identified and are being reviewed. Fat, oil and grease (FOG) that is poured down kitchen sinks and harden in sewers which restricts flow and can cause FOG 5 Produce an action plan SW WSCC, EA, Summer 2017 A Sidlesham DAP action plan is provided in appendix B of this blockages. following completion of CDC drainage strategy. Headroom Spare capacity in a sewerage network or wastewater treatment works. the Sidlesham DAP 6 Complete the Pagham SW 2018 The Pagham DAP will be produced as part of Southern Water’s Hydraulic overload Too much water in the system. DAP which covers part of ongoing 2015 to 2020 DAP programme before updating the the Manhood Peninsula drainage strategy for the Manhood Peninsula. Infiltration reduction Infiltration is the ingress of groundwater into sewers through cracks and joints. IRPs are an EA requirement for water plan (IRP) and sewerage companies to report on the activities being carried out to reduce infiltration. 7a Identify sewerage SW Not stated in An investigation of the sewer flooding issues in the eastern part flooding issues and SWMP of Selsey has been carried out as part of the Sidlesham DAP using Integrated water cycle An integrated approach to managing the water environment to meet long-term challenges of water stress, stringent remedial measures hydraulic modelling of the sewerage system. A potential cause of management (IWCM) environmental needs, high population growth, risk of drought or flooding and climate change. in Selsey (SWMP Ref. sewer flooding has been identified as a lack of capacity in parts of SELS_004) the sewerage system. Possible options to reduce sewer flooding Lead Local Flood LLFA are county councils and unitary authorities that have a number of flood management responsibilities including have been identified and will be considered during the assessment Authority (LLFA) the local flood risk management strategy. of all options identified in the DAPs in the Southern Water region. 7b Identify sewerage SW Not stated in As part of the Sidlesham DAP, sewer flooding issues have been Offline Refers to water which is diverted from its course and stored in a separate area flooding issues and SWMP investigated in property flooding clusters to the south and west remedial measures in of Sidlesham village. The flooding mechanism has been identified Ofwat Ofwat is the economic regulator of the water sector in England and Wales. Sidlesham. Local residents as possibly being due to groundwater infiltration or surface water have reported concerns inundation of the foul sewer network. Outcomes Objectives about foul flows in Southern Water carried out surveys and repairs for groundwater Jury Lane. (SWMP Ref. Online Refers to water which is temporarily stored at points within the water channel SIDL_009) infiltration in the village of Sidlesham in 2013. Ongoing monitoring of flow levels are to be carried out to check whether the repairs have Per capita Generally refers to the volume of water consumed by a person. The units for PCC are normally measured in litres per been successful or whether further infiltration reduction is required. consumption (PCC) day. Southern Water does not manage sewers in Jury Lane, Sidlesham. One population equivalent is the biodegradable load (matter) in wastewater having a five-day biochemical oxygen 7c The foul pumping station SW Not stated in An investigation of sewer flooding issues in West Wittering was Population equivalent demand (BOD) of 60g of oxygen per day. Population equivalent does not necessarily reflect the actual population of on Pound Road in West SWMP included in the Sidlesham DAP. Hydraulic modelling has predicted a community and will include effluent from industrial or commercial premises. Wittering is thought to potential flooding in Pound Road. Groundwater infiltration of the foul be the cause of sewer sewer network may be a cause of the flooding and requires further Preliminary Flood Risk Similar to a SFRA and provides a high level overview of flood risk in a county. flooding (SWMP Ref. investigation using long term flow monitoring and possible CCTV Assessment (PFRA) WWIT_004) surveys of the sewers. A simple treatment which will typically involve screening to remove rags and other similar large solids, maceration of Preliminary treatment 8 Investigate the use of SW WSCC, EA, 2018 Consultants have been appointed to carry out a study on the benefits solids and grit removal. SuDS to manage surface CDC of SuDS for Southern Water and its customers. Drainage partners are water issues to be consulted on SuDS policy and implementation in each region. Primary treatment involves a physical and/or chemically-enhanced settlement of suspended solids that is not Primary treatment removed by preliminary treatment. 9 Provide support and WSCC Community Ongoing Communities are being encouraged to prepare for and reduce the funding for Operation groups, town risk and impacts of flooding in West Sussex through the provision of The ownership of private sewers and lateral drains was transferred to water and sewerage companies on 1 October Private sewers Watershed Active and parish funding of £1.25m in 2013, £1.1m in 2014–15 and £0.5m in 2016–17 2011. Private pumping stations ownership was transferred on 1 October 2016 subject to certain criteria. Communities Fund councils Secondary treatment involves biological treatment where bacteria are used to break down the biodegradable matter Secondary treatment (SW=Southern Water, EA =Environment Agency, WSCC=West Sussex County Council, CDC=Chichester District Council, DAP=drainage area in wastewater. plan, SuDs=sustainable drainage systems) Page 42 Drainage Strategy – Sidlesham Drainage Strategy – Sidlesham Page 43

11. References

Table 26: Glossary of terms – continued Allitt M and Tewkesbury A (2009) ‘Investigations into Urban Creep at 5 Cities’, WaPUG Autumn Term Description Conference 2009. A study carried out by one or more local planning authorities to assess the risk to an area from flooding from all Strategic Flood Risk sources in a district. The SFRA reviews the impact of climate change, and to assess the impact that land use changes Chichester District Council and Havant Borough Assessment (SFRA) will have on flood risk. Council (2015) Local Action Plan for Shellfish Harvesting Beds in Chichester Harbour, Sustainable drainage Techniques used to manage the quantity of surface water run-off from new and existing developments by replicating systems (SuDS) natural processes. An SAB is a SuDs approval body to ensure that SuDS schemes meet requirements. Chichester District Council.

Surface Water A SWMP is used to assess the flood risks due to local flooding by surface water, groundwater and ordinary Chichester District Council and Royal Management Plan watercourses using a partnership approach. Haskoning (2006), Manhood Peninsula, Land Drainage – Phases 1 to 3, Royal Haskoning for Swale A valley-like intersection of two slopes in a piece of land that can be used to store and manage surface water run-off. CDC. Tertiary treatment can involve disinfection to reduce pathogenic bacterial and viral organisms by treating wastewater Defra (2016) Water Framework Directive: List Tertiary treatment with ultra violet light. It can also involve nutrient removal to help prevent the dense growth of algae and other organisms. of Shellfish Water Protected Areas in England, London: Defra. Upsize Expand Environment Agency (2009) Arun and Western Urban Waste Water This European Union Directive was agreed in 1991 and sets standards for sewage treatment. The general principle Streams Catchment Flood Management Plan, Treatment Directive of the directive is to provide treatment of sewage from the largest discharges first and to protect sensitive waters. (UWWTD) Worthing: Environment Agency.

Water Framework The EU Water Framework Directive is aimed at ensuring the sustainability of all activities that impact on water, Environment Agency (2010) Adapting to Directive (WFD) thereby securing the availability of good quality water for sustainable and equitable water use Climate Change: Advice for Flood and Coastal Erosion Risk Management Authorities, Bristol: Environment Agency. Environment Agency, Ofwat and Halcrow (2013) Drainage Strategy Framework. Good practice guidance, Swindon: Halcrow. Environment Agency (2016) Water for life and livelihoods: South East River Basin Management Plan, Bristol: Environment Agency. Portsmouth (2014) Water Resources Management Plan, Havant: Portsmouth Water. Southern Water (2013) Five-year Business Plan 2015 to 2020, Worthing: Southern Water. Southern Water (2015) Adapting to Climate Change 2015, Worthing: Southern Water. Southern Water (2015) Sidlesham Drainage Area Plan: Needs and Options Report, MWH for Southern Water. West Sussex County Council and Capita Symonds (2010) Strategic Flood Risk Assessment of West Sussex, East Grinstead: Capita Symonds for WSCC. West Sussex County Council (2011) West Sussex Preliminary Flood Risk Assessment, WSCC. West Sussex County Council (2012) West Sussex County Council Report on June 2012 Flood Event, WSCC. West Sussex County Council (2014) West Sussex Local Flood Risk Management Strategy 2013 to 2018, WSCC. West Sussex County Council and ch2m (2015) Manhood Peninsula Surface Water Management Plan, Swindon:CH2M for WSCC. Page 44 Drainage Strategy – Sidlesham

Appendix A – Strategic assessments

Table 27: Key to strategic assessments

Strategic Assessment Level Residual Risk Whole Life Costs Environmental Impact (due to Input Required from Other Other Constraints Programming Uncertainties implementation of the strategy) Stakeholders Capital Expenditure (Capex) Operational Expenditure (Opex)

Low The strategy reduces the Low Minimal additional operational Minimal environmental Southern Water would lead Zero or minimal other Short term Minimal uncertainty in the data original risk to an acceptable = < £1 Million (estimate) expenditure impact due to construction or on the strategy with minimal constraints against successful The strategy could be or methods used to evaluate the level within the required time operational activities resulting input required from other implementation of the strategy implemented within the next risk or strategy frame in; stakeholders 5 years • insignificant increase in carbon emissions • temporary noise, odours or traffic disruption.

Medium The strategy would not fully Medium A significant increase in There would be a significant Some input would be required Other constraints which would Medium term Some uncertainty in the data or reduce the original risk to £1 Million to £10 Million operational expenditure (power, impact on the environment as a from other stakeholders such need to be considered in the The strategy could be methods used to evaluate the an acceptable level within (estimate) labour etc) due to additional: result of the strategy due to; as; strategic assessment such as; implemented within the next risk or strategy. the required time frame. The 5 to 10 years strategy would either: • pumping • a permanent increase • partnership to develop and • customer behaviour The uncertainties would affect in carbon emissions (eg implement the strategy the assessment of the risks and/ • be effective in the long • operation of treatment assets increased pumping or • potential changes or strategic assessment. term but insufficient for major construction) • joint development and to legislation • cleaning and maintenance management of policies Work is required to increase the short to medium term • approval by other • education campaigns • an increased risk of pollution quality and/or quantity of data to • effective in the short to • provision of land or planning stakeholders improve our understanding. medium term but insufficient • stakeholder/customer • an increase in discharge of permission for construction treated/untreated effluent • availability of land for the long term engagement plans • review of permit consents for construction • Analysis and modelling. • significant traffic disruption, (DWF, discharges). noise, odours etc. • ease of access to land for construction/ operational activities • potential upgrading of associated assets as a result of the strategy.

High The strategy would be High Capex The strategy would result in a The strategy would result High input would be required A high number of additional Long term A high level of uncertainty in ineffective at reducing the £10 Million to £30 Million high increase in operational in a very high impact on the from other stakeholders to constraints which would have a The strategy could be the data or methods used to original risk to an acceptable (estimate) expenditure which would environment which would enable the strategy to be significant impact on successful implemented within the next evaluate the risk or strategy. level in the short, medium and significantly affect the whole life be unacceptable. Additional successful. Activities would implementation of the strategy 10 to 25 years This uncertainty significantly long term Very high Capex total expenditure (totex). investment would be required include; affects the quality of the risk/ => £30 Million (estimate) to reduce the environmental strategic assessment. Significant impact to an acceptable level. • activities listed above work is required to improve the for the medium level quality and/or quantity of data. • partnerships to share risks, costs and resources • implementation of additional actions and activities by stakeholders which are essential to successful achievement of the strategy. Page 46 Drainage Strategy – Sidlesham

Appendix A – Strategic assessments continued

Table 28: Strategic assessment for maintaining compliance with permits at our treatment works

Outcome: Maintaining compliance with permits at our treatment works Risk: Insufficient headroom in treatment capacity and dry weather flow consent to accommodate growth Strategy description Residual risk Whole life costs Environmental impact Input required from other Other constraints Environmental and societal Programming Uncertainties stakeholders benefits Capital expenditure (Capex) Operational expenditure (Opex)

1) Reduce groundwater Medium Low to medium Low to medium Low Low Medium • Reduction in flooding Short to medium Low to medium infiltration of foul sewers to Reduces the risk of • Sewer repairs. • CCTV surveys. • Reduced carbon • Minimal input required • Surveys require optimal and pollution incidents. Benefits could be realised by • Percentage of reduce DWF breaching the DWF consent emissions due to reduced from other stakeholders. conditions of high 2020 if funding is available, DWF attributable to but doesn’t increase • Manhole sealing. • Look and lift surveys. pumping and processing. groundwater level and • Enables economic or 2025 if funding requires groundwater infiltration. development of treatment capacity and • Flow surveys. low flows in the sewer. external approval. change the risk of breaching • Less risk of pollution the region. • Location of groundwater treated effluent consents at (Costs of surveys would or controlled releases • Available funding in infiltration. the works. be offset by reduced if groundwater flows infiltration reduction costs for pumping and are reduced. budget which will be processing groundwater.) prioritised for a number of • Some traffic disruption villages across the region. during survey and repair work. • This strategy would need to be combined with an expansion in treatment capacity to reduce overall risk.

2) Provide additional Low to medium Medium Medium Medium to high Medium Medium • Enables economic Medium Low to medium treatment capacity at the Reduces the risk of • New treatment assets. • Operation of • Additional treated • Requires EA consent for • Availability of land to development of Benefits could be realised • Population works as required breaching treated effluent additional assets. effluent would be additional discharges construct new assets. the region. by 2025 if the scheme is equivalent capacity consents at the works but • There is a potential discharged to the Broad to the Broad Rife. approved. of Sidlesham WTW. doesn’t change the risk of scheme to uplift Rife which needs to be • Approval of funding breaching the DWF consent . population equivalent improved from ‘bad’ to • Requires EA consent for the scheme in the • Growth in region to 2040. capacity at Sidlesham ‘good’ status by 2027. for change to DWF. next business plan. WTW in our business • Environmental impact. plan for 2015 to 2020 • Increased carbon • Planning permission • This strategy would need if anticipated growth emissions from may be required to to be combined with a takes place. construction and extend the works. DWF consent change operation of new assets. or infiltration reduction to reduce overall risk.

3) Transfer wastewater to Low to medium Medium Medium Medium Medium Medium • Reduction in flooding Medium Medium to high other treatment works with Reduces the risk of • Construct new pumping • Additional pumping • Additional treated • May require changes • Availability of land for and pollution incidents. Benefits could be realised • Capacity of network spare capacity breaching DWF and station or install new cost to a neighbouring effluent discharged to to consents for the construction work. by 2025 if the scheme is and treatment works treated effluent consents transfer pumps at catchment. a watercourse in the neighbouring WTW. • Enables economic approved. in the neighbouring at Sidlesham WTW but an existing WPS. neighbouring catchment. • Approval of funding development of catchments to be increases the risk at • Additional process costs • Planning permission for the scheme in the the region. confirmed by the DAP. neighbouring WTW. • Construct a new rising at the neighbouring WTW. • Increased carbon for potential new next business plan. main to a neighbouring emissions due pumping station. wastewater catchment to construction with spare capacity. and pumping to a neighbouring catchment. Page 48 Drainage Strategy – Sidlesham

Appendix A – Strategic assessments continued

Table 29: Strategic assessment for minimising flooding and pollution due to wastewater

Outcome: minimising flooding and pollution due to wastewater Risk: insufficient network capacity to accommodate forecast new wastewater connections due to population growth Strategy description Residual risk Whole life costs Environmental impact Input required from other Other constraints Environmental and societal Programming Uncertainties stakeholders benefits Capital expenditure (Capex) Operational expenditure (Opex) 1) Upsize foul/combined Low High Medium to high Medium Medium Low to medium • Reduction in flooding Medium Low sewers, pumps and rising Reduces the original risk of • Upsize trunk and • Additional pumping costs. • Increase in carbon • Requires changes to • Access to land to and pollution incidents. Benefits could be realised by Check capacity of existing mains as required flooding and pollution due to strategic sewers. emissions due to consents due to treatment upgrade/install 2025 if scheme is approved. network to accommodate additional wastewater flows. • Additional process construction and of additional wastewater. new sewers. • Provide capacity in the growth in sewer flows. • Upsize pumps and costs at the works. additional pumping/ network accommodate rising mains at processing. • Approval of funding new wastewater pumping stations. for the scheme in connections. • Traffic disruption. next business plan.

2) Reduce groundwater Low to medium Low to medium Low to medium Low Low Medium • Reduction in flooding Short to medium Medium infiltration of foul sewers If infiltration is identified as • Sewer repairs. • CCTV surveys. • Reduced carbon • Minimal input required • Surveys require optimal and pollution incidents. Benefits could be realised by • Percentage of DWF a major component of DWF emissions due to reduced from other stakeholders. conditions of high 2020 if funding is available. attributable to in foul sewers then repairs • Manhole sealing. • Look and lift surveys. pumping and processing. groundwater level and • Provide capacity in groundwater infiltration. the sewerage network should provide capacity for • Flow surveys. low sewer flows. additional wastewater flows. • Less risk of pollution and treatment works • Location of groundwater (Costs of surveys would or controlled releases • Available funding to accommodate new infiltration. be offset by reduced costs if groundwater flows in infiltration wastewater connections. for pumping/processing are reduced. reduction budget. of groundwater.) • Some traffic disruption during survey/repair work.

3) Transfer wastewater to Low to medium Medium to high Medium Medium Medium Medium • Reduction in flooding Medium Medium to high other treatment works with Reduces the risk of flooding/ • Construct new pumping • Additional pumping • Additional treated • May require changes • Availability of land for and pollution incidents. Benefits could be realised Capacity of network spare capacity pollution in the Sidlesham station on the edge cost to neighbouring effluent discharged to to consents for construction work. by 2025 if the scheme is and treatment works in catchment but increases of the catchment. catchment. a watercourse in the neighbouring WTW. • Provide capacity in approved. neighbouring catchments to the risk in neighbouring neighbouring catchment. • Approval of funding the sewerage network be confirmed by DAP. catchments. • Construct a new rising • Additional process costs • Planning permission for for the scheme in the and treatment works main to a neighbouring at the neighbouring WTW. • Increased carbon new pumping station. next business plan. to accommodate new wastewater catchment. emissions due to wastewater connections. construction/pumping.

4) Construct offline storage Low to medium High Medium Medium Medium Medium to high • Reduction in flooding Medium Low to medium tanks to attenuate high Reduces the risk of hydraulic • Construction of one or • Additional cleaning • Impact during Planning permission • Availability of land for and pollution incidents. Benefits could be realised by • Required size of the flows overloading of the sewers more large concrete and maintenance costs construction of required for underground construction work. 2025 if scheme is approved. tank to accommodate but may not have the underground tanks in confined space. underground tank/s. • Provide capacity in groundwater and capacity to accommodate storage tank/s. • Approval of funding the sewerage network surface water flows. high infiltration or surface • Additional pumping costs for the scheme in the and treatment works water flows to/from storage tank. • Increase in carbon next business plan. to accommodate new emissions from wastewater connections. construction and additional pumping.

5) Reduce surface water in Medium to high See table 30 combined sewers Combined sewers are a small percentage of Sidlesham’s sewerage network. Page 50 Drainage Strategy – Sidlesham

Appendix A – Strategic assessments continued

Table 30: Strategic assessment for minimising flooding and pollution due to surface water and groundwater

Outcome: minimising flooding & pollution due to surface water and groundwater Risk: insufficient network capacity to accommodate groundwater infiltration and surface water flows

Strategy description Residual risk Whole life costs Environmental impact Input required from other Other constraints Environmental and societal Programming Uncertainties (to be stakeholders benefits investigated) Capital expenditure (Capex) Operational expenditure (Opex)

1) Remove misconnections Low to medium Low Low to medium Low High Medium to high • Reduces the risk of Short to medium Medium of surface water to foul Removes the direct • Property owners would • Cost of impermeable Little environmental impact. • Local authorities • Property owners may surface water flooding of A campaign to remove Volume of surface water sewers connection of surface pay the cost of removing area survey. may need to enforce refuse to remove properties and pollution misconnections could be in foul sewers due to water drains to foul sewers. misconnections and the removal of misconnections. of water bodies. started reasonably quickly if mis-connections and the The residual risk depends connecting to the • Cost of surveys to identify. misconnections funds are available. potential success of the on the extent of the correct sewer. misconnections (eg flow as Southern Water strategy. misconnections. survey, dye tracing). does not have the • Some property owners power to enforce. may be provided with • Education of property water butts to reduce owners, local • Local authorities surface water drainage. building firms etc. may need to lead on education through building controls etc.

2) Maintain public sewers, Medium Medium Medium Low to medium High Medium to high • Reduces risk of flooding Short to medium Low to medium highway drains and land Partially reduces the risk of • Complete actions • Complete actions • Traffic disruption • Maintenance of highway • Riparian owners may not of properties. Ongoing benefits realised Quantity of additional drainage system surface water flooding but in the SWMP. in SWMP. during the replacement gullies, drainage ditches, maintain watercourses. as actions are completed surface water flows due to may require additional work of sewers. watercourses by others. • Reduces risk of pollution in SWMPs and routine climate change and urban to reduce long term risks • Repair or renew sewers • Jetting of sewers to • Customers may leading to improved maintenance is carried out. creep etc. due to climate change. and rising mains in prevent blockages. • Low impact from • Enforcement of Land continue to dispose of water bodies. poor condition. sewer jetting or other Drainage Act by others. inappropriate objects in • Root removal. routine maintenance. the sewerage system. • Maintain/renew • Others to complete flood equipment at pumping • Education of customers reduction actions. stations and CSOs for to reduce FOG in sewers. optimal performance.

3) Upsize public surface Medium Medium Low to medium Low to medium Medium to high Low to medium • Reduction in flooding Medium Low to medium water/combined sewers as Surface water and combined • Upsize existing public • Surface water flows by • Increase in carbon • Highways drains to be • Access to land to and pollution incidents. Benefits could be realised by • Quantity of additional required sewers are a low percentage surface water sewers. gravity to watercourses. emissions due to maintained or improved upgrade/install 2025 if scheme is approved. surface water flows of the sewerage network. construction work. by local authorities new sewers. due to climate change • Maintenance and to reduce surface and urban creep etc. cleaning costs. • Traffic disruption during water flooding risk. • Approval of funding construction work. for the scheme in the next business plan.

4) Construct offline storage Low to medium High Medium Medium Medium Medium to high • Reduction in flooding Medium Low to medium tank/s to attenuate high Reduces the current risk of • Construction of one or • Additional cleaning • Impact during • Planning permission • Availability of land for and pollution incidents. Benefits could be realised by • Required size of the flows hydraulic overloading of the more large concrete and maintenance costs construction of required for construction work. 2025 if scheme is approved. tank to accommodate sewers but may not have underground tanks. in confined space. underground underground tank/s. • Provide capacity in groundwater and the capacity to reduce the storage tank/s. • Approval of funding the sewerage network surface water flows. increased risk due to climate • Additional pumping costs for the scheme in the and treatment works change. to/from storage tank. • Increase in carbon next business plan. to accommodate new emissions from wastewater connections. construction and additional pumping.

5) Encourage take up of Medium Medium Low to medium Low Medium Low to medium • Reduces some Short to medium term Medium SuDS by others through; Removes some surface • Low cost for each • Cleaning and Minimal environmental Partnership working on • Potential changes in risk of flooding, Policy adoption could realise • Quantity of additional • adopting SuDS in water flows in the sewers. water butt. maintenance of impact SuDS adoption policy legislation on SuDS pollution, releases. benefits in the short term. surface water flows due public open spaces Would not be sufficient to adopted SuDS adoption etc to climate change etc. reduce the risk of additional • Costs depend on number • Reduces bills for property • reducing bills for partial/ surface water flows due of properties provided • Reduced pumping costs. • Obtaining Ofwat support owners who install SuDS. • Quantity of flows with water butts etc. for investment in SuDS. removed by SuDS. full disconnection to climate change & urban • SuDS improves of domestic surface creep. public spaces. water flows • Reduces carbon • provision of water emissions from pumping. butts to customers

continues on next page Page 52 Drainage Strategy – Sidlesham

Appendix A – Strategic assessments continued

Table 30: Strategic assessment for minimising flooding and pollution due to surface water and groundwater – continued

Outcome: minimising flooding & pollution due to surface water and groundwater Risk: insufficient network capacity to accommodate groundwater infiltration and surface water flows

Strategy description Residual risk Whole life costs Environmental impact Input required from other Other constraints Environmental and societal Programming Uncertainties stakeholders benefits (to be investigated) Capital expenditure (Capex) Operational expenditure (Opex)

6) Large scale retrofitting Low to medium Medium to high Low to medium Low High Medium to high • Reduces some Medium to high Medium of SuDS Reduces the risk of • Retrofitting of basins, • Cleaning and • Some environmental • Partnerships to • High groundwater level risk of flooding, Initial benefits could be • Quantity of surface additional surface water swales, planters, maintenance of impact during the share risks, costs restricts infiltration pollution, releases. realised by 2030. water flows due to flows causing flooding and permeable surfaces. adopted SuDS. construction of SuDS. and resources. SuDS techniques. climate change etc. pollution. • Improves public • Costs may be shared • Reduced pumping costs. • The strategy will • Availabilty of land for open spaces. • Quantity of flows with other stakeholders. improve the environment swales, planters etc. removed by SuDS. significantly. • Reduces carbon • Obtaining Ofwat support emissions. for investment in SuDS.

7) Separation of surface Medium to high Medium to high Low to medium Medium Medium Medium • Reduces risk of flooding Medium Medium water from foul water in Sidlesham has mainly • Construction of new • Additional surface water • Impact during • Partnership working to • Availability of land of properties. Benefits could be realised • Quantity of surface combined sewers separate foul and surface surface water sewers, pumping costs offset construction work separate surface water to construct new by 2025 to 2030. water flows due to water networks. Less than pumping stations by reduced pumping of new sewers and from combined sewers. surface water pumping • Reduced pollution climate change etc. 1% of the sewerage network and outfalls. of combined flows. pumping stations. stations or outfalls. leading to improved is combined sewers. • Planning permission bathing & shellfish waters • Additional surface • Increase in carbon for new pumping • Availability of suitable and watercourses. water sewers to emissions from stations, outfalls etc. discharge points. maintain and clean. construction.

8) Reduce groundwater Low Low to medium Low to medium Low Low Medium • Reduction in flooding Short to medium Medium infiltration of foul sewers If groundwater infiltration • Sewer repairs. • CCTV surveys. • Reduced carbon • Minimal input required • Surveys require optimal and pollution incidents. Benefits could be realised by • Percentage of flow is identified as a major emissions due to reduced from other stakeholders. conditions of high 2020 if funding is available attributable to component of flow then • Manhole sealing. • Look and lift surveys. pumping and processing. groundwater level and • Provide capacity in or 2025 if funding requires groundwater infiltration. the sewerage network repairs should reduce the • Flow surveys. low flows in the sewer. external approval. risk of flooding due to • Less risk of pollution and treatment works • Location of groundwater hydraulic overloading by (Costs of surveys would or controlled releases • Available funding in to accommodate new infiltration. groundwater. be offset by reduced if groundwater flows infiltration reduction wastewater connections. costs for pumping and are reduced. budget to be prioritised processing groundwater.) for a number of villages • Some traffic disruption across the region. during survey and repair work. Page 54 Drainage Strategy – Sidlesham

Appendix A – Strategic assessments continued

Table 31: Strategic assessment for improving water bodies to ‘good’ status by 2021 or 2027

Outcome: improve water bodies to ‘good’ status by 2021 or 2027 and maintaining ‘excellent’ bathing waters Risk: diffuse urban and rural pollution. Increase in pollution and releases due to insufficient capacity Strategy description Residual risk Whole life costs Environmental impact Input required from other Other constraints Environmentaland societal Programming Uncertainties stakeholders benefits (to be investigated) Capital expenditure (Capex) Operational expenditure (Opex)

1) Implementation of Medium Low to medium Medium Low High Medium • Improve biodiversity. Medium to long Medium to high integrated water cycle IWCM is a long-term strategy • Requires investment • Collection and analysis • The strategy will • Requires significant • IWCM requires the Benefits from pilot schemes • Will IWCM be effective? management and working and may not achieve the in research and of data to assess improve the environment engagement and input development of an • Improve the wellbeing of could be realised between (Use trials to investigate). with external stakeholders required improvements by development of sources of pollutants. significantly. from other stakeholders institutional and residents and visitors. 2020 and 2025 and from • Willingness of other to reduce the pollution of 2021. innovative solutions to including local authorities legal framework. • Increase recreational other catchments in the water bodies aid the delivery of IWCM. • Modelling of catchments. and landowners. longer term. stakeholders to change use of water bodies. their behaviour. • May require • Use of decision • Requires a change in analysis tools. • Increase tourism improvements to practice and behaviour and improve the wastewater treatment. • Ongoing engagement of all polluters of local economy. with all stakeholders. water bodies.

2) Minimise pollution See tables 29 and 30 and sewerage network releases due to additional wastewater, surface water and groundwater flows using the potential strategies described in tables 29 and 30. Page 56 Drainage Strategy – Sidlesham

Appendix B – Sidlesham DAP Action Plan

Table 32: Sidlesham DAP Action Plan DAP Location Capital/ Issue Location Location of flooding Outline scheme Proposed scheme Status Action Programme ref Maintenance of growth description owner Flooding/Growth 5 Itchenor and Capital Sewer condition Itchenor and Various Sewer replacement Sewer lining Complete SW Complete Birdham Maintenance Birdham

10.3 Selsey Capital Flooding to properties Flooding Manor Lane, Maresfield Place, Gainsborough Road, Option 1: upgrade WPS New up-rated WPS. New rising main Upsize 1,935m Feasibility SW Dependant on willingness to pay and cost (internal & external) Grafton Road and James Street and upsize network of gravity sewer benefit analysis

10.3 Selsey Capital Flooding to properties Flooding Manor Lane, Maresfield Place, Gainsborough Road, Option 2: upgrade CSO New overflow structure Feasibility SW Dependant on willingness to pay and cost (internal & external) Grafton Road and James Street and upsize network New outfall benefit analysis Upsize 1,665m of gravity sewer 10.3 Selsey Capital Flooding to properties Flooding Manor Lane, Maresfield Place, Gainsborough Road, Option 3: offline storage Upgrade WPS. New rising main Feasibility SW Dependant on willingness to pay and cost (internal & external) Grafton Road and James Street and upsize network Upsize 1,513m of gravity sewer benefit analysis Offline storage tank 10.3 Selsey Capital Flooding to properties Flooding Manor Lane, Maresfield Place, Gainsborough Road, Option 4: new WPS at New WPS Feasibility SW Dependant on willingness to pay and cost (internal & external) Grafton Road and James Street Holford Green New rising main benefit analysis Upsize 1,340m of gravity sewer 10.3 Selsey Capital Flooding to properties Flooding Manor Lane, Maresfield Place, Gainsborough Road, Option 5: separation of Removal of all hard standing area (roads and roofs) Feasibility SW Dependant on willingness to pay and cost (internal & external) Grafton Road and James Street flows from the Selsey model benefit analysis

10.4 East Bracklesham Capital Flooding to properties East Bracklesham Drive and Bracklesham Lane Option 1: offline storage Off-line storage tank with pumped return New Feasibility SW Dependant on willingness to pay and cost (internal & external) 180m rising main benefit analysis 180m of new gravity sewer 10.5 West Wittering Capital Flooding to properties Pound Road, Seaward Drive & Rookwood Road Option 1: offline storage Off-line storage tank with pumped return New 70m Feasibility SW Dependant on willingness to pay and cost (external) and sewer reinforcement rising main 370m of new gravity sewer benefit analysis

10.6 East Wittering Capital Flooding to properties Solent Road, Church Road, Shore Road & Marine Drive Option 1: Offline storage Offline storage tank with pumped return New 70m Feasibility SW Dependant on willingness to pay and cost (internal & external) and sewer reinforcement rising main Upsize 547m of gravity sewer benefit analysis

10.7 Birdham Capital Flooding to properties Florence Close & Crooked Lane Option 1: Offline storage 125m of twin box culvert Feasibility SW Dependant on willingness to pay and cost (external) (gravity return) New weir arrangement in existing chamber benefit analysis

10.7 Birdham Capital Flooding to properties Florence Close & Crooked Lane Option 2: Offline storage Storage tank with pump return Feasibility SW Dependant on willingness to pay and cost (external) (pumped return) New 70m rising main benefit analysis Upsize 250m of gravity sewer 10.8 Itchenor Capital Flooding to properties Memorial Hall Itchenor Option 1: Offline Storage Storage tank with pump return. New 25m rising Feasibility SW Dependant on willingness to pay and cost (external) (Pumped Return) and main. New 25m gravity sewer. benefit analysis Upsizing 10.8 Itchenor Capital Flooding to properties Memorial Hall Itchenor Option 2: surcharge relief New bifurcation Chamber Feasibility SW Dependant on willingness to pay and cost (external) 285m of new gravity sewer benefit analysis

10.9 Almondington Capital Flooding to properties Almondington Lane & Third Avenue Option 1: sewer upsize Upgrade WPS Feasibility SW Dependant on willingness to pay and cost (external) Extend rising main 202m benefit analysis Upsize 825m of gravity sewer 10.9 Almondington Capital Flooding to properties Almondington Lane & Third Avenue Option 2: flow transfer Upgrade WPS Feasibility SW Dependant on willingness to pay and cost (external) Extend rising main 202m benefit analysis Upsize 300m of gravity sewer New gravity sewer 450m 10.9 Almondington Capital Flooding to properties Almondington Lane & Third Avenue Option 3: online Storage Upgrade WPS Feasibility SW Dependant on willingness to pay and cost (external) New gravity sewer 95m (including online storage) benefit analysis Upsize gravity sewer 200m 10.9 Almondington Capital Flooding to properties Almondington Lane & Third Avenue Option 4: offline storage Storage tank with pumped return Upsize 566m of Feasibility SW Dependant on willingness to pay and cost (external) (pumped return) gravity sewer benefit analysis

11.3 Highleigh Road Capital Flooding to properties Highleigh Road WPS Infiltration reduction Sewer Sealing Feasibility SW Investigate when conditions arise Maintenance (external)

11.3 Rookery Lane Capital Flooding to properties Rookery Lane WPS Infiltration reduction Sewer Sealing Feasibility SW Investigate when conditions arise Maintenance (external) Page 58 Drainage Strategy – Sidlesham

Appendix B – Sidlesham DAP Action Plan continued

Table 32: Sidlesham DAP Action Plan continued DAP Location Capital/ Issue Location Location of flooding Outline scheme Proposed scheme Status Action Programme ref Maintenance of growth description owner Flooding/Growth 11.3 Rookery Lane Capital Flooding to properties Rookery Lane WPS Infiltration reduction Sewer Sealing Feasibility SW Investigate when conditions arise Maintenance (external)

11.3.1 Highleigh Capital Growth Braemere Lane, To be determined on Options to be considered: surface water removal, Feasibility SW Timing dependent on planning certainty Highleigh receipt of planning sewer upsize, storage application approval

11.3.5 Bracklesham Capital Growth Off Barton Way, To be determined on Options to be considered: surface water removal, Feasibility SW Timing dependent on planning certainty Bracklesham receipt of planning sewer upsize, storage application approval

11.3.3 Birdham Capital Growth Rowan Nursery, To be determined on Options to be considered: surface water removal Feasibility SW Timing dependent on planning certainty Bell Lane, receipt of planning sewer upsize and storage Birdham application approval

11.3.2 Birdham Capital Growth Crooked Lane, To be determined on Options to be considered: surface water removal Feasibility SW Timing dependent on planning certainty Birdham receipt of Planning sewer upsize and storage Application Approval

11.3.2 Birdham Capital Growth Coppice Barn, To be determined on Options to be considered: surface water removal Feasibility SW Timing dependent on planning certainty Church Lane, receipt of planning sewer upsize and storage Birdham application approval

11.3.2 Birdham Capital Growth Church Lane, To be determined on Options to be considered: surface water removal Feasibility SW Timing dependent on planning certainty Birdham receipt of planning sewer upsize and storage application approval

11.3.4 Selsey Capital Growth Park Farm, To be determined on Options to be considered: surface water removal Feasibility SW Timing dependent on planning certainty Selsey receipt of planning sewer upsize and storage application approval