Y Bwthyn Palliative Care Unit, Pontyclun

Transcription

1 Flood Consequence Assessment (Level 1) Y Bwthyn Palliative Care Unit, Pontyclun March 2017 Prepared by: Giuliano Guadagnino BEng Reviewed by: Dimitris Linardatos BEng (Hons) MSc CEng MICE Reference: Revisions Ver Date By Notes 1 Sept 2016 GG Draft for comment 2 Oct 2016 GG Draft for comment 3 Mar 2017 GG Issued as Supporting document for Planning Application Page 1 of 23

2 Y BWTHYN PALLIATIVE CARE UNIT Contents 1 Introduction 2 Site Context Site Description & Location 3 Development Proposals 4 Flood Consequence Assessment Flood Risk from Watercourses/Sea Flood Risk from Groundwater Flood Risk from Sewers and Overland Flows Flood Risk from Reservoirs Flood Mitigation Measures 5 Warning and Flood Evacuation Plan 6 SuDS Assessment 7 Surface Water Management Existing Run-off Proposed Run-off 8 Conclusions & Recommendations Appendix A - Topographical Plans Appendix B - Correspondence Appendix C - Drawings Appendix D - Calculations Abbreviations AOD Above Ordnance Datum NRW Natural Resources Wales FFL Finished Floor Level FCA Flood Consequence Assessment TAN 15 Technical Advice Note 15 SFRA Strategic Flood Risk Assessment FRMP Flood Risk Management Plan Flood Consequence Assessment Page 2 of 23

3 1. Introduction Y BWTHYN PALLIATIVE CARE UNIT Price & Myers have been commissioned to undertake a Flood Consequence Assessment (FCA) for the proposed development of the Y Bwthyn Palliative Care Unit at The Royal Glamoran Hospital in Ynysmaerdy, Pontyclun. This FCA has been carried out in accordance with the Planning Policy Wales (PPW), Rhonnda Cynon Taf County Borough Council Flood Risk Management Plan (FRMP), Technical Advice Note 15 (TAN 15), along with advice and guidance from Natural Resources Wales (NRW) and CIRIA documents to support the outline planning application for the proposed development at the above site. The TAN 15 states that an appropriate FCA is required for all development proposals within a tidal or fluvial floodplain. The Natural Resource Wales (NRW) indicative map shows that the site is within the River Ely s floodplain. Therefore, the flood risk must be focused on flood risk from the River Ely as well as assessing the flood risk from other sources. This report is based on a desk-top review of published information. The objectives of this FCA are to: Identify and assess the risks of all forms of flooding to the development and demonstrate how these flood risks will be managed. Establish whether the proposed development will be safe from all sources of flooding. Assess the Risk of flooding from the proposed works to the surrounding areas. Figure 1 - Location Map Flood Consequence Assessment Page 3 of 23

4 2. Site Context Site Description & Location The site is currently fully developed and occupies an area of approximately 0.48 Ha. An existing carpark, an access road, soft and hard landscaped areas currently cover the site, as seen in Figure 2. Access is available from an access road coming off the Ely Valley Road which is approximately 60m east of the site s eastern boundary. The River Ely runs approximately 200m west of the site s western boundary in a southerly direction. The existing Royal Glamoran Hospital buildings bound the site to the north and west. The site falls to the south, having a maximum ground level difference of approximately 1m. The average ground level is 59.5m AOD. A topographical survey drawing showing the existing site levels can be found in Appendix A. Figure 2 - Existing Site Arrangements The site has approximate OS coordinates of / at Grid Reference ST036841, and the postcode is CF72 8XR Flood Risk Assessment Page 4 of 2123

5 3. Development Proposals Y BWTHYN PALLIATIVE CARE UNIT The site will be redeveloped for a new single storey hospital building consisting of a new palliative care unit, providing inpatient based care, specialist day centre care and palliative outpatient services. The development will have a carpark on the eastern side of the site, as can be seen in Figure 3. It is proposed that the site of the new building be raised to match the existing hospital platform which has a Finished Floor Level (FFL) of approximately 60.12m AOD. The existing carpark levels will be retained with new additional carpark areas tying into these levels. Figure 3 - Proposed Development Flood Consequence Assessment Page 5 of 23

6 4 Flood Consequence Assessment Y BWTHYN PALLIATIVE CARE UNIT Flood Risk from Watercourses/Sea There is a risk of flooding from watercourses as identified on the Natural Resources Wales (NRW) indicative flood outline map. The map shows that the site lies partly within Flood Zone 2 (1 in 1000 year undefended flood event) and is at risk of flooding from the River Ely and the Nant Muchudd. Land in this flood zone is assessed as having an annual probability of river flooding between 0.1% and 1%. The NRW s map suggests that the site is not located in an area which benefits from flood defences. Refer to Figure 4 for the NRW s flood map for planning purposes. The River Ely flows through Tonyrefail, and then through the grounds of the Royal Glamoran Hospital at Ynysmaerdy, west of the site. The Nant Muchudd stream flows past the eastern side of the site before flowing into the River Ely at the Llantrisant & Pontyclun Golf Club. These sections of the rivers are fluvial only as the local topography indicates and therefore pose no tidal risk in the local area, including the site. NRW have provided modelled flood level information for this area. The site is located between cross sections NtMchdd1641U and NtMchdd1774D which are taken along the Nant Muchudd, and cross sections ELY06170 and ELY06380 which are taken along the River Ely, as can be seen in Figure 5. The flood map indicates that flooding will most likely occur from the River Ely at cross section ELY06170 and the Nant Muchudd at NtMchdd1641U. Therefore, ELY06170 and NtMchdd1641U will be used to assess the flood risk to the proposed development as it is located upstream of the site and represents the worst case scenario. The 1 in 100 year, 1 in 100 year plus climate change for the River Ely and the Nant Muchudd are AOD and 60.00m AOD respectively. Refer to Appendix B for NRW plans to scale. Price & Myers have done further modelling based on the Product 7 information received from NRW, as seen in Figure 7.1 and Figure 7.2. Structures along the watercourses have been incorporated into the model to more accurately mimic flood conditions. The Welsh Government s policy clarification letter for Flood Consequence Assessments: Climate change allowances (issued 23 rd August 2016) states, it is recommended that the central estimate, or change factor, for the 2080s for the relevant river basin district should be used to assess the potential impact of climate change as part of a flood consequence assessment. The LPA has expressed that, as the proposed building is a stand-alone unit and non-hospital/emergency unit, the building should be classified as Highly Vulnerable and therefore designed to 1 in 100 year plus climate change standards. A 1 in 100 year plus 25% climate change storm event was used for the model. Additionally, a 1 in 1000 year storm event was used to determine the worst case flood scenario. Refer to Appendix C for the River Model Plan to scale. The results show that the entire site is at risk of flooding from both the River Ely and the Nant Muchudd. The model shows that, for the developed site, the highest flood water level will be approximately m AOD at the north east corner of the site for the 1 in 100 year plus 25% climate change storm event. The level of flood water at the proposed building location will vary from m AOD on the southern side to m AOD on the northern side. The model shows that the proposed building will not increase the flood risk to third party land. Additionally, the flood model for the 1 in 1000 year storm event shows that the proposed building will reduce flooding in the neighbouring property to the south by acting as a barrier steering a portion of the flood water on the site back towards the main watercourse before the flood water reached the southern properties Flood Consequence Assessment Page 6 of 23

7 Y BWTHYN PALLIATIVE CARE UNIT Figure 4 - Natural Resources Wales Indicative Floodplain Map for Planning Figure 5 - Natural Resources Wales Cross Sections for Flood Modelling NRW s maps show the extent of historical flooding, as seen in Figure 6. However, NRW s flood maps confirm that the specific site has not been flooded since records began Flood Consequence Assessment Page 7 of 23

8 Y BWTHYN PALLIATIVE CARE UNIT Figure 6 - Historic Flooding Map (extract from Natural Resources Wales website) Figure in 100 year plus 25% climate change allowance flood f model without the proposed building (Price & Myers model based on NRW Product 7 information) Flood Consequence Assessment Page 8 of 23

9 Y BWTHYN PALLIATIVE CARE UNIT Figure in 100 year plus 25% climate change allowance flood model with the proposed building (Price & Myers model based on NRW Product 7 information) Existing Flood Defences The NRW s Flood Defences map shows that there are flood defences along the eastern bank of the River Ely, as seen in Figure 8. The NRW flood map (Figure 4) does not indicate that the site benefits from these defences. However, it should be noted that the site is bounded by the existing hospital building to the west and that this building will act as a barrier for flood waters from the River Ely. It is assumed that Figure 4 shows the flood extent in the event that the existing hospital building was not present. Although the flood model drawing produced by Price & Myers (Appendix C) confirms that the building will act as a barrier, it also shows that flood water will still reach the site along the southern access road. Therefore the flood risk to the site from the River Ely can be deemed as medium. The topographical survey drawing (Appendix A) shows that there are some raised defences at the eastern side of the site and the ground levels are below the 1 in 100 year flood level. However, the Price & Myers flood model drawing (Appendix C) shows the raised defences will be overtopped in a 1 in 100 year plus 25% climate change storm event which will flood the site. This suggests the site is currently at medium risk of flooding from the Nant Muchudd. Flood protection measures and how the flood risk to the site will be reduced are discussed later in this section Flood Consequence Assessment Page 9 of 23

10 Y BWTHYN PALLIATIVE CARE UNIT Figure 8 - Flood Defences Map (extract from Natural Resources Wales website) Flood Risk from Groundwater The British Geological Survey (BGS) maps show that superficial deposits underlie the site, as seen in Figure 9. This indicates that groundwater could be present at shallow depths. The Site Investigation report by ListersGeo (2016) confirms the presence of Glacial deposits underlying the Topsoil or Made Ground on the site. Subsequent monitoring recorded standing water levels of between 3.3m and 3.6m. Figure 9 - Local Geology -Superficial Deposits (extract from British Geological Survey website) Flood Consequence Assessment Page 10 of 23

11 Y BWTHYN PALLIATIVE CARE UNIT The BGS maps show the flood risk from groundwater is considered low to moderate in the area of the site, as seen in Figure 10. As the proposed building does not have a basement and the FFL will be raised above the existing ground levels, the risk from ground water is considered low. Figure 10 - Areas Susceptible to Groundwater Flooding (extract from British Geological Survey website) Flood Risk from Sewers and Overland Flows Topographical information for the area shows that the ground falls from the east to the west without creating a valley at the site location, as seen in Figure 11. This means that any overland water will flow to the east without significant ponding in the local area. However, the topographical survey (Appendix A) shows that the site falls to the south and overland water will flow to the south before flowing west along the access road Flood Consequence Assessment Page 11 of 23

12 Y BWTHYN PALLIATIVE CARE UNIT Figure 11 - Local Topography (extract from British Geological Survey website) The RWA s surface water flooding map also confirms that parts of the site may are at low risk of ponding, as seen in Figure 12. This ponding is more likely related to low lying areas rather than to overland flow paths which direct surface water at this location from the surrounding areas. The proposed levels will ensure that no local ponding will occur on site. Figure 12 - Surface Water Flood Map (extract from Natural Resources Wales website) Flood Risk from Reservoirs NRW s flood map shows that the site is not at risk of flooding from reservoirs, as seen in Figure Flood Consequence Assessment Page 12 of 23

13 Y BWTHYN PALLIATIVE CARE UNIT Figure 13 - Reservoir Flood Map (extract from Natural Resources Wales website) Flood Mitigation Measures The LPA has expressed that, as the proposed building is a stand-alone unit and non-hospital/emergency unit, the building should be classified as Highly Vulnerable and therefore designed to 1 in 100 year plus climate change standards. To reduce the risk of flooding from the River Ely and Nant Muchudd to the site, it is proposed that the Finished Floor Level (FFL) for the proposed building will match the existing hospital building FFL of 60.38m AOD. This will be well above the flood model s design flood levels of m AOD for the 1 in 100 year plus 25% climate change flood event. A FFL of 60.38m AOD will also be well above the flood model s design flood levels of m AOD for the 1 in 1000 year flood event. This shows that although the proposed building will be classified as Highly Vulnerable. However the design meets the flood design criteria for Emergency Services too. Furthermore, NRW has requested all Finished Floor Levels (FFL) to be constructed at least 300mm above the 1 in 100 year plus climate change flood level with appropriate flood resistant and resilient measures incorporated throughout the design and construction of the development (Appendix B). The following flood resistant and resilient measures are proposed Flood Resistance & resilient Measures: Locate all sockets at least 300mm above the FFL. Water, electricity and gas meters should be also located above the flood level (if possible). Use concrete floors at ground floor level to eliminate potential for damage from flood water. Floor finishes should be also made from water resistant materials (such as tiles). Incorporate damp proof membranes into the structure to minimise the passage of water through ground floors. The local topography shows that overland flows from any source will flow downstream without causing a major inconvenience on site. However, levels should be set to direct any overland flows away from building s entrances and car parking areas (if possible) Flood Consequence Assessment Page 13 of 23

14 5 Warning and Evacuation Plan Y BWTHYN PALLIATIVE CARE UNIT In accordance with the SFRA and the NRW s advice a Warning and Evacuation Plan must be prepared in liaison with the Local Authority and the Emergency Services to allow site users to leave the premises in the event of a flood. The NRW is responsible for monitoring flood events and for issuing warnings to people in properties and businesses at risk of flooding. In order to fulfil their responsibilities, the NRW operates a coded warning system. This is a four stage warning system and each stage will trigger a set of procedures for various organisations. Whilst the site is not at risk of flooding from a breach of defences there is still a residual risk that the defences could be overtopped, however this is extremely low. The site is within an area that receives free warning from the NRW, as seen in Figure 14. Flood Alert Flooding is possible. Be prepared - Is used from two hours to two days in advance of flooding. Following Actions: Watch water levels Monitor local news and weather forecasts on radio, TV or internet. Ring Floodline on Make sure you have what you need to put your flood plan into action. Check flood kit is fully equipped. Alert your neighbours, particularly the elderly and less able. Reconsider travel plans. Ensure all residents are accounted for. Flood Warning Flooding is expected. Immediate action is required - Is used from half an hour to one day in advance of flooding. Following Actions: As with Flood Alert plus; Move valuables and other items to safety Prepare flood kit. Prepare to turn off gas, electricity and other services. Be prepared for evacuation. Protect yourself and others that need your help. Severe Flood Warning Severe flooding. Danger to life - Is used when flooding poses a significant threat to life. Following Actions: As with Flood Warning plus; Stay in a safe place. Turn off gas, electricity and water supplies if safe to do so Try to keep calm, and to reassure others, especially children Co-operate with emergency services and local authorities Prepare for evacuation. Call 999 if you are in immediate danger. Warnings No Longer In Force No further flooding is currently expected in your area - Is used when river or sea conditions begin to return to normal. Following Actions: Keep listening to weather reports. Be careful. Flood water may still be around for several days Only return to evacuated buildings if you are told it is safe by emergency services. The site users will be able to evacuate the development once a flood has occurred. The site will therefore be registered with the NRW s Flood Warning Service as well as having a copy of a Flood Management Plan on site. A comprehensive and effective Flood Warning and Emergency Response Plan shall be produced with recommendations for required site procedures that should be taken in Flood Consequence Assessment Page 14 of 23

15 Y BWTHYN PALLIATIVE CARE UNIT response to forecasted flooding (Flood Warnings from the NRW) and for any scenario where flooding starts to occur without prior warning. If flooding does occur without prior warning, the residents will not be able to leave the site safely, however the development will be raised above the flood level and will act as a safe haven. Residents should therefore remain indoors and wait for the emergency services. Figure 14: Flood Warning Areas (extract from Natural Resources Wales website) Flood Consequence Assessment Page 15 of 23

16 6 Surface Water Management Y BWTHYN PALLIATIVE CARE UNIT Existing Run-off Impermeable areas currently occupy approximately 90% (0.43ha) of the site area. The existing runoff rate has been calculated for a 1 in 100 year storm event using the Modified Rational methods. Q 100 = 2.78 x A x i (where A is the catchment area in Ha and i is the rainfall intensity in mm/hour as estimated from the Microdrainage software). Q 100 = 2.78 x 0.43 x = l/sec Proposed Run-off The proposed development will increase the impermeable area of the site therefore there will be an increase in the surface water runoff rate. Q = 2.78 x 0.46 x = l/sec Flood Consequence Assessment Page 16 of 23

17 7 SuDS Assessment Y BWTHYN PALLIATIVE CARE UNIT In accordance with the Local Plan, NRW guidelines, the SFRA, and CIRIA documents, surface water run-off should be managed as close to its source as possible. The NRW states that all new developments should aim to reduce run-off to Greenfield rates utilising SUDS unless there are practical reasons for not doing so. The following drainage hierarchy was used to assess the possibility of implementing SUDS at the site: 1. Store rainwater for later use; 2. Use infiltration techniques, such as porous surfaces in no-clay areas; 3. Attenuate rainwater in ponds or open water features for gradual release; 4. Attenuate rainwater in tanks or sealed water features for gradual release; 5. Discharge rainwater direct to a watercourse, 6. Discharge rainwater to a surface water sewer/drain; 7. Discharge rainwater to a combined sewer. The capacity of rainwater harvesting systems to attenuate rainwater depends on the water use within the building. If there is no activity in the building and the harvester is full, no attenuation will be provided during a subsequent storm event. In the worst case scenario the rainwater harvester will provide no attenuation. The SUDS manual states that the hydraulic performance of green roofs during extreme events tends to be fairly similar to standard roofs. This means that green roofs will reduce the run-off rates in small storm event such as the annual and the 1 in 2 year events. However, these systems provide no attenuation benefits in high storm events such as the 1 in 30 year and 1 in 100 year storms which are considered in the design of surface water drainage systems. The benefits of these systems therefore cannot be considered in the design of any attenuation systems. In accordance with NRW guidelines, Building Regulations and Water Authorities advice, the preferred means of surface water drainage for any new development is into a suitable soakaway or infiltration drainage system. Sustainable urban drainage systems (SUDS) can reduce the impact of urbanisation on watercourse flows to ensure the protection and enhancement of water quality and encourage the recharging of groundwater in a manner that mimics nature. If drainage to an infiltration system proves to be an unsuitable option for a site then drainage to a watercourse must be assessed. Drainage to the public sewers can be considered only when all other alternative options are not suitable. The SI report indicates that the fine grained Glacial Deposits beneath the site are practically impermeable. However the course grained Glacial Deposits soil below 3.0m depth at the northwest corner of the site have a permeability rate of 6x10E-4 m/s. Further tests at the proposed location of the attenuation tank will be undertaken in order to assess the porosity properties of the ground. Groundwater monitoring must also be undertaken on site as the depth of infiltration system depends on groundwater levels. A minimum easement of 1m must be provided between the infiltration systems and the maximum groundwater table. The performance of the infiltration systems depend on this unsaturated zone. A ground contamination assessment must be also undertaken to ensure that any infiltration techniques will not increase the risk of contaminating the groundwater. Infiltration systems which may be suitable include soakaways, swales and permeable pavement. If further investigation confirms that the site is unsuitable for infiltration techniques, then surface water from the site could be discharged into the existing surface water drainage system which could be connected to the public sewers or could discharge directly to the river. The site layout Flood Consequence Assessment Page 17 of 23

18 Y BWTHYN PALLIATIVE CARE UNIT drawing shows that the proposed development will increase the impermeable areas on site and therefore will increase the run-off rates. The NRW requested attenuation to Greenfield run-off rates from the proposed development. The Greenfield run-off rate for the proposed development was calculated for various storm events using the online UKSUDS tool developed by HR Wallingford. The results show that the site has a Greenfield run-off rate of 6.63l/s in the 1 in 1 year storm event. The full UKSUDS reports can be found in Appendix B. Therefore, the surface water run-off rate from the proposed development will be attenuated to the 1 in 1 year storm event Greenfield run-off rate of 6.5l/s. The surface water drainage system must be designed for the 1 in 1 year, 1 in 30 year and 1 in 100 year storm event also making allowances for 25% climate change. Excess water will be temporarily accommodated in SUDS systems. Preliminary calculations showed that a storage volume of 441m³ will be required in SUDS such as permeable pavement, swales and underground tanks in order to provide the required attenuation from the entire site area (Appendix D). Detailed calculations must be undertaken during the detail design stage, when the total impermeable area will be known and the most appropriate type of SUDS to serve the specific development have been selected. Surface water from large vehicle trafficked areas must pass through a petrol interceptor before draining to a soakaway, to the public sewer or to the river Flood Consequence Assessment Page 18 of 23

19 8 Conclusions & Recommendations Y BWTHYN PALLIATIVE CARE UNIT NRW s flood map shows that the site is within Flood Zone 2 (medium risk of annual flooding from rivers). These areas can be suitable for development providing that the Sequential and Exception Tests have been applied successfully. Flood defences in the area reduce the flood risk from medium to low. The existing hospital building acts as a barrier to flooding from the River Ely. Considering this and that the ground levels around the new building will be raised above the 1 in 100 year plus climate change flood level, the actual risk is low. A flood defence breach analysis exercise has confirmed that the site is at risk of flooding from breached defences. However this will only affect the carpark as the ground around the new building will be raised. Therefore, the residual risk is considered low. The flood modelling carried out by Price & Myers shows that the proposed building will not increase the flood risk to third party land. Additionally, the flood model for the 1 in 1000 year storm event shows that the proposed building will reduce flooding in the neighbouring property to the south by acting as a barrier steering a portion of the flood water on the site back towards the main watercourse before the flood water reached the southern properties. NRW s warning service currently serves this area. All site users will be registered with this service. Surface water will be attenuated before draining to the existing site connections to the public sewers and/or the river. The proposed drainage system will reduce the peak flow rates to 6.5 l/sec, which is the minimum recommended attenuation rate. Excess water will be temporarily accommodated to SUDS. The surface water drainage system will be designed for the 1 in 1 year, 1 in 30 year and 1 in 100 years plus 25% climate change allowance storm event. Surface water from vehicle trafficked large areas will pass through a petrol interceptor before discharging to the ground, the public sewers or the river. Therefore, the proposed redevelopment has an acceptable flood risk within the terms and requirements of the NPPF Flood Consequence Assessment Page 19 of 23

20 Y BWTHYN PALLIATIVE CARE UNIT Appendix A Topographical Survey Information Flood Consequence Assessment Page 20 of 23

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22 Y BWTHYN PALLIATIVE CARE UNIT Appendix B - Correspondence Flood Consequence Assessment Page 21 of 23

23 ATI-10707a Ynysmaerdy, Pontyclun E: N: Current Flood Map Figure 1 shows the current Flood Map (version ) at this location. The Flood Map represents a combination of the undefended fluvial and tidal flood extents derived from a combination of detailed local modelled and nationally generalised modelled data. More information on the Flood Map can be obtained from the Natural Resources Wales website Local Flood Risk Mapping Study Model Summary The results summarised below are TuFLOW results taken from the River Ely Velocity Depth Mapping study undertaken by Atkins in This study builds on the existing Section 105 flood risk mapping model for the River Ely and the River Clun and has been converted into ISIS format. In Cardiff and Pontyclun the 1D ISIS model has been linked to 2D Tuflow modelling on the floodplain. This was updated by Atkins in January 2011 to fix an error with the Z line data near the Millennium stadium in Cardiff. The results are taken from version 4.2 of the hydraulic model, dated January The flows were estimated based on FEH. The downstream boundary applied to the model is defined by the joint probability work carried out by HR Wallingford ( A new joint probability appraisal of flood risk, P.G Samuels and N. Burt). 1D Results Tables 1-2 show the defended modelled water levels (maod) and flows (m 3 /s) for the model node points in the site vicinity, including a 1 in 100 year scenario with climate change (+20% flow). Figure 3 shows the location of these ISIS cross-sections. Table 1: Defended Design Levels Peak Water Levels (maod) Cross-Section Q5 Q10 Q20 Q50 Q75 Q100 Q100+ CC Q200 Q1000 ELY ELY NtMchdd1641U NtMchdd1774U NtMchdd1774D Table 2: Defended Design Flows Peak Water Flows ( m 3 /s ) Cross-Section Q5 Q10 Q20 Q50 Q75 Q100 Q100+ CC Q200 Q1000 ELY ELY NtMchdd1641U NtMchdd1774U NtMchdd1774D

24 4.0 Additional Information Figure 2 shows the approximate outline from localised flooding in1981. The local authority may be able to provide information on issues such as localised flooding from sewers, drains and culverts. 5.0 References 1. Department for Environment, Food and Rural Affairs, Technical Report Design sea levels. R&D Report SC Defra/Environment Agency 2. River Ely and Tributaries: Model Update and Hazard Mapping, Atkins. Final Issue, July Notes Undefended scenarios are provided as being a possible worst case scenario in the event of defence failure. They are used as the basis of the Flood Map. The scope of the model is the mapping of flood risk, it is not intended for detailed design. The model should be considered as the starting point for more detailed modelling, commensurate with the consequences of flooding at the site of interest. NRW models are available under licence agreement for the purpose of further development. Contact Natural Resources Wales Data Distribution team for details of terms, conditions and pricing. If the data is used in support of an FCA, please include the reference number. Please refer to NRW standard terms and conditions. Flood Risk Analysis 29/07/2016

25 Legend ^_ Site Location Flood Zone 3 (1 in 100 year undefended fluvial and 1 in 200 year undefended tidal extents) Flood Zone 2 (1 in 1000 year undefended fluvial and tidal extents) Areas benefiting from defences!! Defences ^_ Flood Storage Areas Main Rivers Project Ynysmaerdy, Pontyclun, CF72 8XR [Ref: ATI-10707a] Drawing Figure 1: Current Floodmap [v201607] Ordnance Survey data Crown copyright and database right OS , Ordnance Survey data Crown copyright and database right 2015 ± Date 29th July 2016 Scale 1:5,000

26 Legend ^_ Site Location Approximate extent of historical flooding ^_ Project Drawing Ynysmaerdy, Pontyclun, CF72 8XR [Ref: ATI-10707a] Figure 2: Historic Floodmap (v4) Ordnance Survey data Crown copyright and database right OS , Ordnance Survey data Crown copyright and database right 2015 ± Date 29th July 2016 Scale 1:5,000

27 Legend ^_ Site Location 1D Cross Section ELY06170 NtMchdd1641U ^_ ELY06380 NtMchdd1774U NtMchdd1774D Project Ynysmaerdy, Pontyclun, CF72 8XR [Ref: ATI-10707a] Drawing Figure 3: 1D Cross Section Locations Ordnance Survey data Crown copyright and database right OS , Ordnance Survey data Crown copyright and database right 2015 ± Date 29th July 2016 Scale 1:3,000

28 Ein cyf/our ref: CAS Z1X9 Eich cyf/your ref: n/a Rivers House St Mellons Business Park Fortran Road Cardiff CF3 0EY Rhondda Cynon Taf CBC Sardis House Sardis Road Pontypridd CF37 1DU Ebost/ Ffôn/Phone: FAO: Guiliano Guadagnino 11 November 2016 Annwyl Syr/Madam / Dear Sir/Madam Y Bwthyn Palliative Care Unit, Pontyclun- Advice on Flood Consequences Assessment (FCA) Thank you for referring us to the above, which we received on 19 October We understand that you have submitted the Flood Consequences assessment (FCA), produced by Price and Myers, dated September 2016, in order for us to provide you with advice on the acceptability of flooding consequences. We understand that this document will be submitted in support of a future planning application. As you are aware, the proposed development is partially within Zone C2, as defined by the Development Advice Map (DAM) referred to in Technical Advice Note 15: Development and Flood Risk (TAN15) (July 2004). Our Flood Map information, which is updated on a quarterly basis, confirms the site to be partially within the 0.1% (1 in 1000 year) annual probability fluvial flood outlines of the Nant Muchudd, a designated main river. The FCA states that the topographical survey drawing shows the ground levels of the site to be below the predicted 1 in 100 year plus climate change flood level, suggesting the site is currently at risk of flooding from the Nant Muchudd. We note that the intention is to raise the ground levels of the site to 60.00m AOD. Based on this level the development is predicted to be flood free during the1 in 100 year plus climate change flood event. The FCA states that during the predicted 1 in 1000 year flood event the site will flood to a depth of approximately 710mm. We refer you to Section 5 of TAN15, which classifies hospitals within the Emergency Services development category. The guidance set out in section A1.14 of TAN15 states that Emergency Services should be flood free up to and including the predicted 1 in 1000 year flood event. We do acknowledge however the particular nature of this proposal and that it is an extension to an existing hospital. We therefore recommend you seek advice Tŷ Cambria 29 Heol Casnewydd Caerdydd CF24 0TP Cambria House 29 Newport Road Cardiff CF24 0TP Croesewir gohebiaeth yn y Gymraeg a r Saesneg Correspondence welcomed in Welsh and English

29 from the LPA on how they intend to classify the development and whether they will expect it to be flood free in events up to and including the 1 in 1000 year flood event, as per the guidance in A1.14. In any case, it should be noted that a flood depth of 710mm is in excess of the indicative thresholds for both residential development and Emergency Services, as described in A1.15 of TAN15. Furthermore, no information has been provided on the other elements within A1.15 i.e. maximum velocity of floodwaters, speed of inundation and rate of rise. As a minimum, information is needed regarding maximum velocity before we can provide further comment. It is of concern that there is no discussion of impact to third parties within the FCA. If the site is being raised to mitigate the flood risk to the site, the potential risk of displaced water to third parties should be quantified. It is not known if compensation has been investigated for this loss of flood plain and what this flood compensation will be. We note that the FCA suggests an alternative mitigation measure with the use of voids as form of mitigation. We do not recommend the use of voids as they can become blocked and there is no guarantee that they will remain as an open area indefinitely. The use of stilts reduces the impact on the development but does not guarantee that the flood plain will be retained in the same way as a compensation scheme (which is a form of risk substitution). We therefore suggest that you address the above points in an amended FCA and then submit it to us for further comment. Please note, on 23rd August 2016 the Welsh Government published a Policy Clarification Letter regarding climate change allowances for planning purposes, supplemented by a guidance note and map. The letter and supporting documents supplement the policy advice provided in TAN15. Local planning authorities, applicants and their consultants are expected to use these climate projections from 1 st December Therefore, if your amended FCA is submitted after this date, it must use the revised climate change allowances. We recommend that you also seek advice from the Council s Land Drainage Department in relation to the disposal of surface water. If you have any further queries, please don t hesitate to contact us. Yn gywir / Yours faithfully Helen Griffiths Ymgynghorydd Cynllunio Datblygu / Development Planning Advisor Cyfoeth Naturiol Cymru / Natural Resources Wales Ffon / Tel: Gwefan / Website: / Page 2 of 3

30 Ein diben yw sicrhau bod adnoddau naturiol Cymru yn cael eu cynnal, eu gwella a u defnyddio yn gynaliadwy, yn awr ac yn y dyfodol. Our purpose is to ensure that the natural resources of Wales are sustainably maintained, enhanced and used, now and in the future. Page 3 of 3

31 Y BWTHYN PALLIATIVE CARE UNIT Appendix C - Drawings Flood Consequence Assessment Page 22 of 23

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33 Y BWTHYN PALLIATIVE CARE UNIT Appendix D - Calculations Flood Consequence Assessment Page 23 of 23

34 Greenfield runoff estimation for sites Site name: Y Bwthyn Macmillan Palliative Care Unit Site coordinates Site location: Royal Glamoran Hospital Latitude: N This is an estimation of the greenfield runoff rate limits that are needed to meet normal best practice criteria in line with Environment Agency guidance Preliminary rainfall runoff management for developments, W5-074/A/TR1/1 rev. E (2012) and the CIRIA SUDS Manual (2007). It is not to be used for detailed design of drainage systems. It is recommended that every drainage scheme uses hydraulic modelling software to finalise volume requirements and design details before drawings are produced. Longitude: Reference: Date: W gcjt4zgdm348 / Sep 2016 Site characteristics Total site area Significant public open space Area positively drained Methodology Greenfield runoff method Qmed estimation method BFI and SPR estimation method HOST class BFI / BFIHOST Qmed Qbar / Qmed Conversion Factor FEH N/A Specify BFI manually ha ha ha Calculate from BFI and SAAR l/s Hydrological characteristics Default Edited SAAR mm M5-60 Rainfall Depth mm r Ratio M5-60/M5-2 day FEH/FSR conversion factor Hydrological region Growth curve factor: 1 year Growth curve factor: 10 year Growth curve factor: 30 year Growth curve factor: 100 year Greenfield runoff rates Qbar in 1 year l/s 1 in 30 years l/s 1 in 100 years l/s Please note that a minimum flow of 5 l/s applies to any site Default Edited l/s HR Wallingford Ltd, the Environment Agency and any local authority are not liable for the performance of a drainage scheme which is based upon the output of this report.

35 Price & Myers Page 1 30 Newman Street London W1T 1LT Date 08/03/ :10 Designed by gguadagnino File 100yr +25%.srcx Checked by XP Solutions Source Control Summary of Results for 100 year Return Period (+30%) Half Drain Time : 684 minutes. Storm Event Max Level (m) Max Depth (m) Max Infiltration (l/s) Max Control (l/s) Max Σ Outflow (l/s) Max Volume (m³) Status 15 min Summer O K 30 min Summer O K 60 min Summer O K 120 min Summer O K 180 min Summer O K 240 min Summer O K 360 min Summer O K 480 min Summer O K 600 min Summer O K 720 min Summer O K 960 min Summer O K 1440 min Summer O K 2160 min Summer O K 2880 min Summer O K 4320 min Summer O K 5760 min Summer O K 7200 min Summer O K 8640 min Summer O K min Summer O K 15 min Winter O K Storm Event Rain (mm/hr) Flooded Volume (m³) Discharge Volume (m³) Time-Peak (mins) 15 min Summer min Summer min Summer min Summer min Summer min Summer min Summer min Summer min Summer min Summer min Summer min Summer min Summer min Summer min Summer min Summer min Summer min Summer min Summer min Winter XP Solutions

36 Price & Myers Page 2 30 Newman Street London W1T 1LT Date 08/03/ :10 Designed by gguadagnino File 100yr +25%.srcx Checked by XP Solutions Source Control Summary of Results for 100 year Return Period (+30%) Storm Event Max Level (m) Max Depth (m) Max Infiltration (l/s) Max Control (l/s) Max Σ Outflow (l/s) Max Volume (m³) Status 30 min Winter O K 60 min Winter O K 120 min Winter O K 180 min Winter O K 240 min Winter O K 360 min Winter O K 480 min Winter O K 600 min Winter O K 720 min Winter O K 960 min Winter O K 1440 min Winter O K 2160 min Winter O K 2880 min Winter O K 4320 min Winter O K 5760 min Winter O K 7200 min Winter O K 8640 min Winter O K min Winter O K Storm Event Rain (mm/hr) Flooded Volume (m³) Discharge Volume (m³) Time-Peak (mins) 30 min Winter min Winter min Winter min Winter min Winter min Winter min Winter min Winter min Winter min Winter min Winter min Winter min Winter min Winter min Winter min Winter min Winter min Winter XP Solutions

37 Price & Myers Page 3 30 Newman Street London W1T 1LT Date 08/03/ :10 Designed by gguadagnino File 100yr +25%.srcx Checked by XP Solutions Source Control Rainfall Details Rainfall Model FSR Winter Storms Yes Return Period (years) 100 Cv (Summer) Region England and Wales Cv (Winter) M5-60 (mm) Shortest Storm (mins) 15 Ratio R Longest Storm (mins) Summer Storms Yes Climate Change % +30 Time Area Diagram Total Area (ha) Time From: (mins) To: Area (ha) XP Solutions

38 Price & Myers Page 4 30 Newman Street London W1T 1LT Date 08/03/ :10 Designed by gguadagnino File 100yr +25%.srcx Checked by XP Solutions Source Control Model Details Storage is Online Cover Level (m) Cellular Storage Structure Invert Level (m) Safety Factor 5.0 Infiltration Coefficient Base (m/hr) Porosity 0.95 Infiltration Coefficient Side (m/hr) Depth (m) Area (m²) Inf. Area (m²) Depth (m) Area (m²) Inf. Area (m²) Hydro-Brake Outflow Control Design Head (m) Hydro-Brake Type Md4 Invert Level (m) Design Flow (l/s) 6.5 Diameter (mm) 91 Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s) XP Solutions