FLOOD RISK ASSESSMENT DAMHEAD CREEK 2 POWER STATION

Transcription

1 FLOOD RISK ASSESSMENT DAMHEAD CREEK 2 POWER STATION

2 Name Job Title Date Prepared Joanne Somerton Senior Consultant (Flood Risk) 14/01/2016 Checked Kerry Whalley Technical Director 04/02/2016 Technical Review Ian Small Associate Director 15/01/2016 AMENDMENT RECORD Issue Date Issued Date Effective Purpose of Issue and Description of Amendment 1 January 2016 January 2016 Draft for Client Comment 2 February 2016 February 2016 Final for Submission

3 TABLE OF CONTENTS 1. Introduction Commission... Error! Bookmark not defined. 1.2 Background Scope of Services Data Sources Site Information Site Description Existing Development Topography Surface Water Resources... 5 Proposed Development Policy Context National Policy National Policy Statements for Energy National Planning Policy Framework... 7 The Sequential Test and Exception Test... 8 Development and Flood Risk Vulnerability Local Policy Medway Local Plan Other Relevant Policy and Guidance Medway Strategic Flood Risk Assessment (2012) Medway Draft Local Flood Risk Management Strategy (2014) Flood Risk Sources of Flood Risk Tidal Flood Risk Flooding History Modelled Flood Levels Flood Defences Overtopping and Breaching of Defences... 13

4 4.3 Fluvial Flood Risk Flooding from Artificial Sources Groundwater Flooding Pluvial Flooding Flooding from Drainage Infrastructure Climate Change Context Tidal Flooding Fluvial Flooding Groundwater Sewers Surface Water Run-off Generation and Overland Flow Proposed Flood Risk Management Measures Mitigation against Tidal Flooding Mitigation against Fluvial Flooding Mitigation against Artificial Flooding Mitigation against Groundwater Flooding Mitigation against Pluvial Flooding and from Drainage Infrastructure Surface Water Management Existing Conditions Existing Runoff from the Site Policy and Stakeholder Requirements National Planning Policy Framework Proposed Conceptual Strategy Restricted Surface Water Runoff Rate Sustainable Drainage Systems Surface Water Attenuation Volumes Off-Site and Residual Risks Off-Site Impacts Residual Risks Conclusions Page iv

5 Figures: Figure 2-1: Damhead Creek 2 CCGT Power Station Site Location Figure 2-2: Application Site Boundary and Areas 1 to 3 Figure 4-1: Environment Agency Flood Extent Map Tables: Table 1-1: Sources of Data Reviewed Table 3-1: Flood Risk Vulnerability and Flood Zone Compatibility Table 4-1: Defended Modelled Tidal Flood Levels for the Site Table 4-2: Un-defended Modelled Tidal Flood Levels for the Site Table 5-1: Recommended Contingency Allowances for Climate Change Table 7-1 Site Areas and Surfacing Table 7-2 Approximate Surface Water Runoff Rates for the Existing Site Areas 1 and 3 (litres/second) Table 7-3 Rainfall Values Table 7-4 Indicative Attenuation Storage Requirements Annexes: Annex A: Annex B: Annex C: Annex D: Data Consultation Topographic Survey Development Plans Proposed Permeable and Impermeable Site Areas Page v

6 1. Introduction AECOM has undertaken a Flood Risk Assessment (FRA) for the proposed Variation under Section 36(c) of the Electricity Act 1989 to the Damhead Creek 2 (DHC2) power station. On 25 January 2011, ScottishPower secured consent under Section 36 of the Electricity Act 1989, for the development, construction and operation of a new 1,000 MW Combined Cycle Gas Turbine (CCGT) adjacent to the existing Damhead Creek Power Station. Further to this, on 28 July 2014 ScottishPower secured consent under Section 36(c) of the Electricity Act 1989 to increase the output of Damhead Creek 2 CCGT to 1,200 MW (DECC Reference /265C) and subsequently in October 2015 this was further increased to 1,800 MW output CCGT. ScottishPower now seek to further vary the existing consent to allow flexibility in the make-up of the plant to include up to 300 MW of Open Cycle Gas Turbine (OCGT) peaking plant within the 1,800 MW scheme. The proposed development therefore now comprises either a CCGT or a CCGT/OCGT power station with a total combined electrical capacity up to 1,800 MW, hereafter referred to as the proposed 1,800 MW with peaking plant scheme option. This application to vary the consent retains the option of constructing the already consented 1,800 MW CCGT-only scheme option but also includes the provision of up to 300 MW of that capacity as OCGT units such that the combined output remains at 1,800 MW. This assessment therefore focuses on the new variant including peaking plant, as the already consented CCGT option was fully assessed as part of the 2015 variation 1.1 Background The Site, comprising approximately 30.9 hectares (ha) of brownfield land, is located to the south of the Hoo Peninsula, Kent, and is centrally located upon National Grid Reference (NGR) , The Environment Agency Flood Zone Map issued in December 2015 (Annex A and Figure 4.1) indicates areas to the south; west and north-west of the Site are located within Flood Zone 3 and are classified as having a high risk of flooding from fluvial or tidal sources. Flood Zone 3 delineates areas classed as having a greater than 0.5% (1 in 200) Annual Exceedance Probability (AEP) of flooding from tidal sources or a greater than 1% AEP (1 in 100) from fluvial sources. Land to the east and north is located within Flood Zone 2. Areas located within Flood Zone 2 are classified as having a medium risk of flooding from fluvial or tidal sources. Flood Zone 2 delineates areas classed as having between a 1% AEP and 0.1% (1 in 1000) AEP of fluvial flooding, or between a 0.5% AEP and 0.1% AEP of tidal flooding in any year. The Environment Agency Flood Zone Map also indicates that the Site lies in an area classed as benefitting from flood defences. The National Planning Policy Framework 1 (NPPF) and the Planning Policy Guidance 2 (PPG) specifies that planning applications for development proposals located in Flood Zone 3 should be accompanied by a FRA. 1.2 Scope The aim is to undertake a FRA that is appropriate to the nature and scale of the Proposed Development that determines flood risk posed to the Site and arising from the Proposed Development and recommends suitable mitigation measures, where required. The objectives of this report are to: review existing information relating to the flood risk posed to the Proposed Development from all sources (e.g. fluvial, surface water, sewer flooding); consult with Medway Council and the Environment Agency in relation to flood risk and their requirements for management of any risk; 1 Communities and Local Government (2012). The National Planning Policy Framework (NPPF) 2 Communities and Local Government, (2014); Planning Policy Guidance. ( Page 1

7 assess the flood risk to the Proposed Development under existing and post-development conditions (taking into account climate change); and outline any mitigating measures needed to ensure the Proposed Development and its occupants will be safe for the lifetime of the development and to meet the requirements of the NPPF. 1.3 Data Sources The baseline conditions for the site have been established through a desk study and via consultation with the Environment Agency, Medway Council, and Southern Water Limited (SWL). This information has been used to inform the assessment made within the FRA. Data collected during the course of this assessment are described in Table 1-1. Table 1-1Sources of Data Reviewed Purpose Data Source Comments Identification of Hydrological Features Identification of Existing Flood Risk Identification of Historical Flooding Details of the Scheme Surface Water Drainage 1: 25,000 Ordnance Survey (OS) mapping. Topographical survey of the Site. EA Indicative Flood Zone Map (Figure 4.1 and Annex A). EA Flood Inundation Mapping (internet). Environment Agency Consultation (Annex A). Medway Strategic Flood Risk Assessment (SFRA) 3, Medway Preliminary Flood Risk Assessment (PFRA) 4 ; Medway Estuary and Swale Shoreline Management Plan 5 British Geological Survey records. PFRA including Public sewer record (SWL) details. Environment Agency SFRAs and PFRAs. Indicative Development Plans. OS Mapping; SFRA. Identifies the position of the Site and local hydrological features. Provides existing Site levels. Identifies fluvial/ tidal inundation extents and historical flooding Provides information on the risk of flooding from reservoirs (artificial sources). Information from the Environment Agency on existing Flood Risk (Annex A). Assesses flood risk across the Medway Council area. Includes flood risk from fluvial/tidal, sewers, overland flow and groundwater. Provides details of geology and hydrogeology in the vicinity of the Site. Identifies the local drainage system near the Site Gives details of historical flooding. Provides layout of the Proposed Development. Identifies existing Site drainage, public drainage system near the Site and details of existing surface water runoff from the Site. 3 Mott MacDonald (2006). Medway Strategic Flood Risk Assessment, Main Report 4 Medway Council (2011) Preliminary Flood Risk Report 5 Halcrow (2010) Medway Estuary and Swale Shoreline Management Plan Page 2

8 2. Site Information 2.1 Site Description The Damhead Creek 2 Power Station Site comprises a roughly undeveloped, triangular shaped area of approximately 30.9 ha (the total area within the application red line indicated on Figure 2-1), approximately 8 km north east of Rochester, Kent. The Site is located to the south of the Hoo Peninsula, a tongue of land between the Thames and Medway estuaries, at NGR , (see Figure 2.1). Figure 2-1 Damhead Creek 2 CCGT Power Station Site Location Damhead Creek CCGT Power Station and is bounded on the southern and eastern sides by earth bunds with a crest level of approximately 5.6 m Above Ordnance Datum (AOD). The Site is bordered by industrial development to the north- west, by wetland lagoons to the north- east and by Kingsnorth Power Station to the south. The surrounding land comprises: Kingsnorth Business Park to the north and north-west; Kingsnorth Industrial Estate to the north and north east; Damhead Creek to the east and south-east; agricultural land and the former Kingsnorth Power Station to the south; and the existing Damhead Creek Power Station to the west. Page 3

9 2.2 Existing Development The application site is described as three main areas (see Figure 2-2): DHC2 main area (referred to as Area 1 in this report) as shaded grey in Figure 2-2, comprising an area of 18.1 ha (including 10.4 ha of land for DCH2 plus, 4.1 ha of CCS land and 3 ha of CCS land in an old substation plot), is where the majority of the new DHC2 will be constructed and lies to the east of the existing Damhead Creek CCGT Power Station. The area is low-lying undulating ground sloping to the south-east and comprises unmanaged grassland and some hardstanding. Area 1 was largely topsoil-stripped and disturbed during the construction of the existing Damhead Creek CCGT Power Station; carbon capture land and DHC1 mitigation land (referred to as Area 2 in this report) as shaded purple and yellow in Figure 2-2, comprising an area of 4.1 ha, lies to the north of the existing Damhead Creek CCGT Power Station. This land consists of hardstanding and is not currently in use; and carbon capture land and ecological mitigation area (referred to as Area 3 in this report) as shaded orange and green in Figure 2-2, comprising an area of 16.7 ha, lies to the north-east of the existing Damhead Creek CCGT Power Station. Land in Area 3 has previously been used to dispose of fly ash from the nearby Kingsnorth Power Station. It is bounded on the west by an ecological mitigation area associated with the existing Damhead Creek CCGT Power Station. Figure 2-2 Application Site Boundary and Areas 1 to 3 Page 4

10 2.3 Topography Prior to the development of the existing Damhead Creek Power Station, the general level of the site varied from circa 2.0 maod in the south west corner to circa 4.1 m AOD at the northern boundary of the site. During the construction of existing plant, the site was generally raised to circa maod. On the western side of the site, the existing ground level flanking the industrial development is at an elevation of 3.8 maod. A new earth embankment has been constructed along the western boundary with a top elevation of not less than 4.8 maod. An updated topographic survey has been provided for the site as part of this assessment. The survey shows ground levels to the north, adjacent to the roundabout are approximately 6.8 maod and these levels fall away to the south to a ground level of approximately 2.1 maod. An earth embankment that runs from northwest to southeast between the DCH2 site and ecological mitigation area has a crest level of approximately 6.7 maod for the majority of its length. Ground levels to the west of this earth embankment are approximately 6.2 maod. The area of land to be used for the laydown area and any future carbon capture and storage plant, situated to the northeast of the DHC2 site is at an elevation of around 6.1 m AOD. A topographic survey showing all site levels is included in Annex B. 2.4 Surface Water Resources The following local water features have been identified through the inspection of OS 1:10,000 mapping; Damhead Creek is located immediately adjacent to the Site boundary to the east and southeast. The Creek is a tributary of the tidal River Medway and flows from the eastern boundary of the existing Kingsnorth Power Station, past the southern boundary of the DHC2 Site before turning northeast and then south-east and entering the River Medway; A buried drainage system runs down the eastern boundary joining an open drainage ditch that runs around the southern boundary of the current Damhead Creek Power Station Site then runs through the EON Kingsnorth site before discharging through the sea wall to the River Medway. There are two ponds located on the ecological mitigation area (shown as the green area on Figure 2-2) which were used for dust suppression during previous dumping of Pulverised Fuel Ash (PFA). These are man-made ponds and are not recharged by any streams or other surface waters. There is also one pond just outside of the eastern boundary of the DHC2 site. These ponds were created in 2000 / 2001 as alternative habitat for reptiles following the development of the existing Damhead Creek CCGT Power Station. There is no flow of surface water into these ponds. The River Medway, an Environment Agency Main River, is located approximately 725m to the south of the Site. The Medway is also tidal at this point and approximately 1 km wide. The Medway Estuary is a tidal saline water habitat subject to tidal fluctuations in level. Water drains from the salt flats such as Stoke Saltings during the ebb tide; and The Thames Estuary, an Environment Agency Main River, is located approximately 6.5 km to the north and 9 km to the east of the Site. Proposed Development The proposed development is the construction and operation of a gas fired power station of electrical output capacity up to 1,800 MW adjacent to the existing Damhead Creek CCGT Power Station site located on the southern side of the Hoo Peninsula. The plant would be fired on natural gas from the UK National Transmission network; no back-up firing on distillate fuel is proposed. As with the existing Damhead Creek CCGT, the plant will be air cooled. The power station will comprise a Combined Cycle Gas Turbine (CCGT) plant or alternatively a CCGT and an Open Cycle Gas Turbine (OCGT) peaking plant located on the same Site; the peaking plant would have an electrical output capacity of up to 300 MW but the total combined electrical output from the CCGT and OCGT will not exceed the 1,800 MW capacity. Page 5

11 It is expected that DHC2 will operate in various running modes including full load (maximum continuous rating) and two shifting where the plant can be operated on and off during the day to meet peak demands. The plant will occasionally be shut down for brief periods of essential maintenance and statutory inspections. DHC2 is expected to have an annual availability of the order of 93% with the remainder of the time dedicated to annual maintenance and unplanned plant failures. The operational life time of the development will be of the order of 35 years. It is envisaged that the peaking plant will operate for up to 1,500 hours per year, to respond to peak demand on the UK transmission system although the CCGT units are expected to run at higher load factors of up to 80% in the early years of operation, reducing through time as new renewables come on line. The previously consented 1,800 MW scheme comprised either a single shaft or a multi-shaft combined cycle arrangement with up to three gas turbines, each with a heat recovery steam generator (HRSG), and connected to either a dedicated steam turbine or a single steam turbine respectively, depending on the plant configuration. The total electrical output was 1,800 MW based on ISO conditions. For the 1,800 MW CCGT with peaking plant scheme option, a multi-shaft arrangement has been considered for the CCGT units, comprising two gas turbines, each with a heat recovery steam generator (HRSG), and connected to a single steam turbine. This is to allow sufficient space for the peaking plant to be accommodated within the Site footprint without compromising the space to be retained for the CCR land. The peaking plant capacity will be generated through up to two OCGTs which will be gas fired with no diesel back-up. The General Arrangement Plan for the 1,800 MW CCGT with peaking scheme option (Annex C) is based on this arrangement of the multi shaft CCGT and up to two peaking plant units and comprises the following plant: Turbine Hall (comprising 2 No. gas turbine buildings 72 m x 31 m x 30 m and 1 No. steam turbine building 60 m x 30 m x 25 m); 2 No. peaking plant stacks up to 50 m x approximately 8.4 m external diameter and 2 No. HRSG stacks modelled up to 95 m x approximately 8.4 m external diameter; HRSG enclosure (1 HRSG building approximately 36 m x 34 m x 45 m); and Air Cooled Condenser (1 No. unit approximately 84 m x 135 m x 46.5 m). The exact dimensions for the proposed 1,800 MW CCGT with peaking plant scheme option cannot be confirmed until the detailed design stage and will be agreed with Medway Council prior to the commencement of construction. The above dimensions however represent the likely sizes of the main components based on ScottishPower s discussions with OEMs The total electrical output of the proposed development would therefore be up to 1,800 MW at ISO conditions. Both the currently consented 1,800 MW CCGT-only scheme option and the proposed 1,800 MW CCGT with peaking plant scheme option would export the electricity generated to the National Grid via the existing Kingsnorth substation, which lies approximately 500 m to the south of the existing Damhead Creek CCGT Power Station boundary. The CHP-Readiness study (Appendix D to the EIR) has demonstrated that there are no potential heat users in the area. The plant will, however, be designed in such a way that future connections will be possible to export heat if heat users are identified. Page 6

12 3. Policy Context Flood risk and surface water management related planning policies and guidance that are relevant to the Proposed Development are described below. 3.1 National Policy National Policy Statements A number of National Policy Statements (NPS) for Energy Infrastructure were designated by the Secretary of State (SoS) under the Planning Act 2008 on 19th July NPS EN-2 6, together with the Overarching NPS for Energy (EN-1) 7, provides the primary basis for decisions on applications for nationally significant fossil fuel electricity generating infrastructure defined at Section 1.8 of EN-2, which includes gas-fired electricity generation. Whilst this application is for a variation under the previous Electricity Act regime, the NPS for Energy provides applicable context and guidance. EN-1 states that applications for energy projects of 1 hectare or greater in Flood Zone 1 and all proposals for energy projects located in Flood Zones 2 and 3 should be accompanied by a NPPF compliant flood risk assessment. In determining an application for development consent, the Planning Inspectorate and SoS (or, in this case, DECC) should be satisfied that where relevant: the application is supported by an appropriate FRA; the Sequential Test has been applied as part of site selection; a sequential approach has been applied at the site level to minimise risk by directing the most vulnerable uses to areas of lowest flood risk; the proposal is in line with the relevant national and local flood risk management strategy; priority has been given to the use of SuDs; and in flood risk areas the project is appropriately flood resilient and resistant, including safe access and escape routes where required, and that any residual risk can be safely managed over the lifetime of the development National Planning Policy Framework The NPPF is supported by the PPG, an online resource published in March The PPG supersedes the PPS25 Practice Guide 8 and the Technical Guidance to the National Planning Policy 9, as detailed in the Ministerial Statement Making the planning system work more efficiently and effectively 10. The NPPF and PPG must be taken into account in the preparation of local and neighbourhood plans, and is a material consideration in planning decisions. It constitutes guidance for local planning authorities and decision-takers both in drawing up plans and as a material consideration in determining applications. The NPPF and PPG recommends that Local Plans should be supported by a Strategic FRA (SFRA) and develop policies to manage flood risk from all sources, taking account of advice from the Environment 6 Department of Energy & Climate Change (2011) National Policy Statement for Fossil Fuel Electricity Generating Infrastructure (EN-2) Planning for New Energy Infrastructure, June Department of Energy & Climate Change (2011) Overarching National Policy Statement for Energy (EN-1) Planning for New Energy Infrastructure, July Communities and Local Government, (2012); Planning Policy Statement 25: Development and Flood Risk, Practice Guidance 9 Communities and Local Government, (2012); Technical Guidance to the National Planning Policy Framework 10 Communities and Local Government (2014); Making the planning system work more efficiently and effectively Page 7

13 Agency and other relevant flood risk management bodies, such as Lead Local Flood Authorities (LLFAs) and Internal Drainage Boards (IDBs). Local Plans should apply a sequential, risk-based approach to the location of development to avoid, where possible, flood risk to people and property and manage any residual risk, taking account of the impacts of climate change, by: - applying the Sequential Test; - applying the Exception Test, if necessary; - safeguarding land from development that is required for current and future flood management; - using opportunities offered by new development to reduce the causes and impacts of flooding; and - where climate change is expected to increase flood risk so that some existing development may not be sustainable in the long-term, seeking opportunities to facilitate the relocation of development, including housing, to more sustainable locations. The Proposed Development will comply with the requirements of the NPPF and EN-1. The Sequential Test and Exception Test The overall aim of the Sequential Test is to steer new development to Flood Zone 1. Where there are no reasonably available sites in Flood Zone 1, local planning authorities allocating land in Local Plans or determining planning applications for development at any particular location should take into account the flood risk vulnerability of land uses and consider reasonably available sites in Flood Zone 2, applying the Exception Test if required. Only where there are no reasonably available sites in Flood Zones 1 or 2 should the suitability of sites in Flood Zone 3 be considered, taking into account the flood risk vulnerability of land uses and applying the Exception Test if required. For the Exception Test to be passed: it must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk, informed by a SFRA where one has been prepared; and, a site-specific FRA must demonstrate that the development will be safe for its lifetime taking account of the vulnerability of its users, without increasing flood risk elsewhere, and, where possible, will reduce flood risk overall. Both elements of the test will have to be passed for development to be allocated or permitted. Development and Flood Risk Vulnerability Table 3.1 shows the classification of flood risk vulnerability and flood zone compatibility according to Section 7, Paragraph 066 of the PPG. Table 3-1 Flood Risk Vulnerability and Flood Zone Compatibility Flood risk Vulnerability classification Essential Infrastructure Water Compatible Highly Vulnerable More Vulnerable Less Vulnerable Zone 1 Zone 2 Exception test required Zone 3a Exception test required Exception test required Page 8

14 Flood risk Vulnerability classification Essential Infrastructure Water Compatible Highly Vulnerable More Vulnerable Less Vulnerable Zone 3b Functional Flood plain Exception test required Key Development is appropriate. Development should not be permitted. According to the PPG the Proposed Development (electricity generating power station) would be classed as Essential Infrastructure. Essential infrastructure is defined within the PPG as b) Essential utility infrastructure which has to be located in a flood risk area for operational reasons, including electricity generating power stations and grid and primary substations. Based on classification shown in Table 3.1, the Proposed Development use is appropriate in Flood Zones 1, 2 and 3a provided that the Sequential Test is passed and the Exception Test is passed for development in Flood Zone 3. Although located within Flood Zone 3, the proposals include the redevelopment of a site that is owned by ScottishPower and is a variation to an existing consented scheme and therefore the application of the Sequential Test is not considered appropriate. In addition, the Proposed Development would be located on land already designated as part of a power station site or as land set aside for future employment under the Medway Local Plan and it is assumed that the Sequential Test for the Site was passed during the site allocation process. The proposed development is similar to the existing consent that already exists for the site. Much of the infrastructure required for such a development already exists at the site and can support the development with minimal impact upon the surrounding environment. In terms of wider sustainability benefits to the community, the potential increase in construction staff would result in beneficial socio-economic effects including employment of local people and sourcing of local goods, services and contractors, and indirect employment benefits. The total investment in the proposed scheme would be around million which represents a substantial investment for the region. The proposed development provides electricity generation that strengthens the local and regional grid network, which, in turn, underpins the development of other services within the south east region. The plant will be highly efficient when compared with other power stations currently in operation and will assist the UK Government in their aims of reducing overall emissions of carbon dioxide through the displacement of coal and oil power stations which are due to close in the coming years and contribute to security of supply. Based on this information and the information provided within this FRA, it is considered that the Proposed Development passes the Exception Test. 3.2 Local Policy Medway Local Plan The Local Development Scheme (LDS) (June 2014) provides an updated programme for the production of a new local plan that will provide the basis for development policy in Medway (it is noted that the Issues and Options document associated with the new Local Plan was consulted on in November 2015, but this plan is not yet adopted therefore the existing policy remains the LDS). The scheme covers the period from 2014 to 2017, and updates the Medway LDS published in August However, some Page 9

15 Medway Local Plan (2003) policies have been retained and will continue to be considered as robust and up-to-date policies within Medway LDS. The following Policies are relevant to the Proposed Development in terms of flood risk and surface water management: Policy BNE45:Undeveloped Coast development will be permitted in and alongside the undeveloped coast, as defined on the proposals map, only if iii) the development is not likely to be at risk from flooding or coastal erosion to the extent that it would require defence works for its safety and protection; Policy CF13: Tidal Flood Risk Areas Development will not be permitted within a tidal flood risk area if; i) it harms the integrity of the flood defences; or ii) it fails to provide for a means of escape for people in the event of a flood; or iii) it introduces residential living and sleeping accommodation below the estimated flood level; or iv) it introduces mobile homes or caravans; or v) it introduces new holiday accommodation between October and May. The Medway Local Plan identifies the Proposed Development site as an existing employment area and the site adjacent as a proposed employment area. The Council has started work on a new Local Plan, which, once adopted, will replace the current Medway Local Plan This will be a single document, containing strategic level and development management policies, land allocations, minerals and waste, and a policies map. The process of producing a new plan is anticipated to take around three years. The plan will cover the period up to 2035 and statutory consultation process for the Issues and Options Consultation Document is underway and will conclude on 29 February Other Relevant Policy and Guidance Medway Strategic Flood Risk Assessment (2012) The SFRA was prepared to assist Medway Council in spatial planning decisions that are required to inform the Development Plan preparation. Existing information and additional hydraulic modelling was undertaken to identify the level of flood risk posed in the Borough. The SFRA reported that there was a residual tidal flood risk to urban areas in the event of a breach in the flood defences along the River Medway, but there is limited historical information with regards to surface and sewer flooding. Medway Draft Local Flood Risk Management Strategy (2014) The Medway Local Flood Risk Management Strategy 11 (LFRMS) outlines the responsibilities of the Risk Management Authorities in Medway and how they are working in partnership to coordinate local flood risk management. This includes engagement with communities, preparing for floods, responding to flood events and collaborating on flood risk studies. 11 Capita Symonds and URS (2014) Medway Council Local Flood Risk Management Strategy. Final Report June Page 10

16 4. Flood Risk 4.1 Sources of Flood Risk There are five potential sources of flooding at the DCH2 site. The dominant flood sources are: tidal flooding from the Medway Estuary and Damhead Creek; fluvial flooding from inland watercourses; site-related flooding (surface water runoff and sewers); overland flow from adjacent sites; and groundwater flooding. The impacts that each may have on the site are discussed in detail in the following sections. 4.2 Tidal Flood Risk Flooding from tidal sources can occur through inundation of floodplains from rivers and watercourses, or inundation of areas outside the floodplain due to the influence of bridges, embankments and other features that artificially raise water levels and/or through the overtopping of defences. Given the distance of the Site from the Thames Estuary (approximately 6.5 km to the north and 9 km to the east of the Site) it is considered unlikely that flooding from the Thames would impact the Site. The River Medway and Damhead Creek are both tidal watercourses in this location with the main tidal influence being the River Medway (Medway Estuary) and are included in this assessment of tidal flooding. The Flood Zone maps produced by the Environment Agency, and shown in Figure 4.1, indicate an area within the south, west and north-west of the Site lies within Flood Zone 3 of the River Medway, representing land with a high risk of flooding from tidal or fluvial sources, whilst land to the east and north lies within Flood Zone 2, representing land with a medium risk of flooding from tidal or fluvial sources. The Flood Zone Map shows the Site is located in an area that benefits from flood defences Flooding History Data provided by the Environment Agency (Annex A) indicates that the Site is known to have flooded in 1953, prior to the installation of flood defences, when a tide level of 4.75 m AOD was recorded. Both the SFRA and the PFRA state that flooding in the Medway area has also been recorded in 1927 (3.92m AOD), 1949 (4.54m AOD), 1960 (3.80m AOD), 1965 (4.60m AOD), 1978 (4.51m AOD) and The December 2005 event, a tidal surge caused low level flooding in parts of Rochester but had no impact at the site of the current Damhead Creek Power Station or the Proposed Development Site. There is no record of any flooding on the DHC2 site or adjacent land since the construction of the existing Power Station development in the late 1990s. Page 11

17 Figure 4-1 Environment Agency Flood Extent Map Modelled Flood Levels The Environment Agency has provided defended modelled flood levels for the River Medway located relative to the Site for the 0.5% (1 in 200) AEP event. The modelled flood water levels for the River Medway have been taken from the detailed 2D Tuflow tidal modelling of the North Kent Coast, completed in August Table 4.1 shows details of the flood levels for the floodplain grid cells relevant to the Site for both the current day 0.5% AEP and 0.1% AEP tidal events and flood levels for the 0.5% AEP climate change scenarios for 2070 and Grid cell locations are shown in Annex A. Table 4.1 Defended Modelled Tidal Flood Levels for the Site Node ID Return Period Water Levels for AEP shown in maod 0.5% (2012) 0.5% (2070) 0.5% (2115) 0.1% (2012) Page 12

18 Node ID Return Period Water Levels for AEP shown in maod 0.5% (2012) 0.5% (2070) 0.5% (2115) 0.1% (2012) Table 4.1 confirms that taking into account the presence of defences the Site does not flood during both the 0.5% (2012) AEP and 0.1% (2012) AEP flood event Flood Defences The Site is protected from flooding associated with tidal sources due to the presence of primary flood defences along the north bank of the River Medway, to the south of the existing Damhead Creek Power Station and to the east of the Proposed Development Site. The Environment Agency has stated that The site is currently defended to a 1 in 1000 year standard of protection. Defences are comprised of raised earth embankments and concrete sea walls. The Environment Agency does not currently have any planned improvement works to the defences in this area. The previous FRA undertaken for the Site indicates the general area within which the site lies is protected by primary sea defences with a crest elevation of 5.7 m AOD or higher. It is understood that the defences are under riparian ownership and responsibility for maintenance lies with the riparian owners. In addition to the primary sea defences, the Proposed Development is protected by secondary earth bunds adjacent to the site, with a crest elevation of approximately 5.6 m AOD. These bunds provide further protection from tidal inundation to a standard of between a 0.5% and 0.1% AEP flood event. In addition, a substantial area to the north and east of the site (proposed for the development of the carbon capture and storage/laydown area) is situated above 6 m AOD due to large quantities of PFA deposited on the site from its former use as a landfill. Therefore, based on Tables 4-1 and 4-2, much of this site area is not considered at risk from flooding during a 0.1% AEP flood event. The North Kent Rivers Catchment Flood Management Plan 12 (CFMP) is a report which has been produced by the Environment Agency and identifies flood risk management policies to assist all key decision-makers in the catchment. The North Kent Rivers CFMP indicates that the Proposed Development falls within Sub-area 4 North Kent Marshes Policy Option 3: areas of low to moderate flood risk where the Environment Agency is generally managing existing flood risk effectively. This policy tends to be applied where the risks are currently appropriately managed and where the risk of flooding is not expected to increase significantly in the future. Tidal flooding represents the most significant risk to the Site but the risk of tidal flooding is considered to be low as the Site is protected to the 0.1% AEP indicative standard. Overtopping and Breaching of Defences As the Site is afforded protection from defences up to the 0.1% AEP flood event, the primary risk from tidal sources is the residual risk from overtopping and/or failure of the defences. 12 Environment Agency (2009) The North Kent Rivers Catchment Flood Management Plan. Summary Report December 2009 Page 13

19 A breach analysis was undertaken as part of the Medway SFRA however the analysis concentrates largely on allocated development sites within the residential areas around Rochester and Chatham. Although inundation maps have been produced for these breaching scenarios, these do not extend as far downstream as the Site of the proposed power station. The Site is protected by both primary sea defences and secondary earth embankments and it would take a breach of both the primary and secondary defences to cause inundation into the site. As part of their consultation response the Environment Agency have stated, Depending on the type of development proposed we would not necessarily expect breach modelling to be provided. An FRA for the site would need to consider the residual risk of flooding in defended areas. Reference to the undefended flood levels may aid in this assessment. Table 4.2 presents the undefended modelled flood water levels for the River Medway for the floodplain grid cells relevant to the Site for the 0.5% (1 in 200) AEP event. Grid cell locations are shown in Annex A. Table 4.2 Un-Defended Modelled Tidal Flood Levels for the Site Node ID Return Period Water Levels for AEP shown in maod 0.5% (2012) 0.5% (2070) 0.5% (2115) 0.1% (2012) In the unlikely event that both primary and secondary defences were to fail information in Table 4.2 provides an indication as to the extent of flooding at the Site. Should a breach in the flood defences occur grid cells 5, 8 and 9 are inundated during a 0.5% AEP flood event. These grid cells (5, 8 and 9) represent Area 1 (the main DHC2 area) within the Site boundary as shown in Figure 2.2. Ground levels in these areas of the Site are approximately m AOD therefore the maximum depth of flooding, to the south of the DHC2 site, would be approximately 2.84 m. Area 3 (the CCS land and ecological mitigation area) remains unaffected as ground levels are above the modelled flood water levels for this event. 4.3 Fluvial Flood Risk Fluvial flooding most commonly occurs after intense or heavy rainfall when any water that falls will naturally migrate toward the nearest river or stream. Where there are instances of especially heavy or long term rain the volume of water may exceed the channel capacity of the river downstream resulting in water levels exceeding the height of the river bank. Page 14

20 A land drainage ditch/small watercourse enters the Site from the north (Area 3) which flows from north to south. At the south east Site boundary this drain then turns west, flowing adjacent to the southern Site boundary and continuing west along the boundary of the exiting Damhead Creek Power Station. The ditch runs through the Kingsnorth site before turning north and discharging into the River Medway. The ditches vary from 2.0 m to m wide and approximately 1.5 m to 2.0 m deep. OS mapping suggests that this drainage ditch flows to a drain to the west of the Kingsnorth Power Station and outfalls via a sluice to the River Medway approximately 0.9 km south west of the Site. The catchment area of the drainage pipe and ditch is relatively small, accepting flows from the Site, the adjacent existing Damhead Creek Power Station and a small area to the north. Given the dimensions of the ditch and the limited catchment area it is considered that any flooding would remain local to the drainage corridor and would be shallow in depth. The risk of flooding from fluvial sources is therefore considered to be low. The open areas of ditch have recently been dredged to allow easier flow. 4.4 Flooding from Artificial Sources The Environment Agency s Risk of Flooding from Reservoirs Mapping shows that there is no residual risk of flooding from a large reservoir in the event of a structural failure or breach. The Reservoir Act defines a large reservoir as one that holds over 25,000 cubic metres (m 3 ) of water, although under the Flood and Water Management Act this has been reduced to 10,000 m 3. There are no canals located in close proximity to the Site. It is considered that the site is at low risk of flooding from artificial sources. 4.5 Groundwater Flooding Groundwater flooding can occur when groundwater levels rise above ground surface levels. The underlying geology has a major influence on where this type of flooding takes place; it is most likely to occur in low-lying areas underlain by permeable rocks (aquifers). British Geological Survey (BGS) information shows that superficial geology beneath the majority of the Site comprises Alluvium - clay, silty, peaty, sandy deposits. A small area to the west and north is underlain with River Terrace Deposits comprising clay and silt. Environment Agency groundwater maps show that the superficial deposits at the Site are designated as Secondary Undifferentiated. This is assigned in cases where it has not been possible to attribute either category A or B to a rock type. In most cases, this means that the layer in question has previously been designated as both minor and non-aquifer in different locations due to the variable characteristics of the rock type. The Site is underlain by a bedrock geology comprising clay and silt of the London Clay Formation overlying Upper Chalk base rock. Environment Agency groundwater maps show that the London Clay beneath the Site is designated as a non-aquifer. Non-aquifers are described as formations which are generally regarded as containing insignificant quantities of groundwater and are therefore unimportant for abstraction or supplying base flow to rivers. The Upper Chalk is designated a Principal Aquifer. These are layers of rock or drift deposits that have high intergranular and/or fracture permeability - meaning they usually provide a high level of water storage. They may support water supply and/or river base flow on a strategic scale. Section 15 of the 2009 Damhead Creek 2 Environmental Statement 13 reports groundwater was observed under Area 1 in the Phase 2 intrusive ground investigation at depths ranging from to 9.5 m below ground level (bgl), from where the levels rose to between 1.45 m and 4.70 m bgl over a period of 20 minutes. Groundwater was observed under Areas 2 and 3 during the Phase 2 Intrusive Site Investigation at depths between m bgl during two monitoring rounds. The relatively high groundwater levels are likely to be due to the close proximity of the site to Damhead Creek, and as such, the two are most likely in hydraulic continuity. Standpipes recorded a tidal variation of approximately 0.10 m in the groundwater. 13 Parsons Brinkerhoff (2009) Scottish Power Damhead Creek 2 Environmental Statement Volume 1 Page 15

21 The Site does not lie within a Groundwater Source Protection Zone. There are no historical records of groundwater flooding in the SFRA and the PFRA states that no historic data is available for local groundwater flood events. Areas Susceptible to Groundwater Flooding (AStGWF) is a strategic scale map showing groundwater flood areas on a 1 km square grid. It was developed specifically by the Environment Agency for use by LLFAs for use in PFRA as required under the Flood Risk Regulations. The AStGW map shows the site is not located in an area susceptible to groundwater flooding. Based on this information, the risk of flooding at the Site from groundwater sources is low. 4.6 Pluvial Flooding Overland flow results from rainfall that fails to infiltrate the surface and travels over the ground surface; this is exacerbated where the permeability of the ground is low due to the type of soil and geology (such as clay soils) or urban development with impermeable surfaces. The Site is currently undeveloped, comprising a combination of hardstanding and grassland. It is not known if the areas of hardstanding are connected to a formal drainage system, therefore it is assumed that surface water run-off from these areas drain to the surrounding local drainage ditches and grassland and the site therefore drains via natural processes, i.e. infiltration to ground. The site of the proposed Damhead Creek 2 plant is surrounded by earth bunds to the west, south and east therefore; the site is well protected from overland surface flooding from adjacent sites and is, in effect, self-contained. Land to the east has been previously raised to above 5.3 m AOD through the artificial deposition of PFA and is higher than the surrounding land preventing surface water run-off entering the Site. The Environment Agency published the updated Flood Maps for Surface Water (ufmfsw) in December The maps indicate areas at risk from surface water flooding, when rainwater does not drain away through the normal drainage systems or soak into the ground, but instead pools on or flows over the ground. The mapping can be viewed on the Environment Agency website. It indicates that overall the Site is considered to be a very low to low risk of surface water flooding. The site is considered to be at very low risk of flooding from pluvial sources. 4.7 Flooding from Drainage Infrastructure Sewer and surface water flooding are often interconnected; insufficient drainage capacity in the sewer network can result in extensive surface water flooding and, by the same rationale, large volumes of surface water can overload the public sewers, causing the sewer network to back up, surcharge and ultimately flood. No underground asset information has been received for the development Site and therefore no information is available regarding the private drainage network within the Site. The Site currently comprises a mixture of permeable and impermeable areas and, with the exception of one private drainage pipe, it is understood that there is no formal drainage within Site Areas 1 and 3. Permeable areas will drain via natural methods (i.e. infiltration to ground) whilst surface water from the impermeable areas will run-off and drain via the permeable Site areas. Area 2 comprises hardstanding and it is assumed that this area drains to the wider surrounding industrial estate drainage system. The 2012 Proposed Drainage Scheme Report 14 states that the Site drains into surface ditches primarily located around the Site. The ditches vary from 2.0 m to m wide and approximately 1.5 m to 2.0 m deep. The 2012 Proposed Drainage Scheme Report also notes that at the southeast corner of the existing Damhead Creek power station, a discharge pipe is located below the earth bund/headwall discharging process waste and surface runoff into Damhead Creek/ River Medway from the existing Damhead Creek power station. 14 ScottishPower (2012) Damhead Creek 2 Power Station Proposed Drainage Scheme Report Page 16

22 There are no historical records of flooding from drainage infrastructure in the Medway SFRA and historical flood records based on postcode data provided by Southern Water to inform the PFRA indicate no drainage infrastructure flooding at or near the Site or in the wider area. Based on this information the risk of flooding from drainage infrastructure is considered to be low. Page 17

23 5. Climate Change 5.1 Context Environment Agency climate change guidance for the NPPF 15 indicates that climate change is likely to have an impact on river flows, sea levels, rainfall intensity, wave height and wind speed. Therefore, the risk of flooding is likely to increase in the future and precautionary climate sensitivity ranges from the Environment Agency guidance are shown below in Table 5.1. Table 5.1 Recommended Contingency Allowances for Climate Change Parameter Peak rainfall intensity +5% +10% +20% +30% Peak river flow +10% +20% Net sea level rise (East of England, East Midlands, London, SE England (south of Flamborough Head)) mm 8.5 mm 12 mm 15 mm Extreme Wave Height +5% +10% The outputs of the UK Climate Projections (UKCP09) 16 climate change scenarios are indicative of a shift towards wetter winters over the whole of England by as much as 20% by the 2050s (Murphy et al., 2009). Shifts in seasonal patterns of rainfall are also expected, with summer and autumn becoming much drier than at present. Snowfall amounts are anticipated to decrease significantly throughout the UK, but the number of rain-days and the average intensity of rainfall are expected to increase. 5.2 Tidal Flooding The impact of climate change on flood levels within the Site for the years 2070 and 2115 are presented in Table 4.1 and Table 4.2. The operational life time of the development will be of the order of 35 years therefore a climate change horizon of 2070 has been used to assess the impact of climate change on the Proposed Development. Based on the predictions of the tidal modelling of the North Kent Coast, the data in Table 4.2 indicates that the risk of fluvial flooding to the Site as a result of climate change will increase. Table 4.2 shows grid cells 2, 5, 8 and 9 (Areas 1 and 2) are flooded to a maximum level of approximately 5.3m AOD (Grid Cell 2). However, the general area within which the site lies is protected by primary sea defences with a crest elevation of 5.7 m AOD or higher and in addition to the primary sea defences, the Site is protected by secondary bunds adjacent to the site, with a crest elevation of circa 5.6 m AOD, therefore the impact of climate change is not expected to impact the Site over the lifetime of the development. The Site is located within the Medway Estuary and Swale Shoreline Management Plan 17 Policy Unit E4-03 Kingsnorth Power Station where the proposed policy approach over the next 100 years is to hold the line and to continue to protect the area and improve the defences that protect existing development. It is considered that the existing defences will be maintained to an appropriate standard to keep providing protection to the area. 15 Environment Agency (2013) Climate change allowances for planners, September Defra (2009) UK Climate Projections (UKCP09) Briefing Summary 17 Halcrow (2010) Medway Estuary and Swale Shoreline Management Plan Page 18

24 5.3 Fluvial Flooding There is no data available for the drainage pipe and ditch within the Site boundary that demonstrate the potential effects of climate change; however, Table 5.1 indicates fluvial peak flows may increase by up to 20% over the lifetime of the development. The Proposed Development is classed as at low risk of flooding from fluvial sources and it is considered unlikely that any change to the magnitude of fluvial flooding will present a significant hazard to the Proposed Development. 5.4 Groundwater The predicted increase in the wetness of winters and the intensity of storm events could impact the groundwater level fluctuations at the Site and possibly increase the level of the water table. As the likelihood of groundwater emergence under the climate change scenario is likely to increase, the potential for groundwater flooding to impact infrastructure will also increase. The Proposed Development is classed as at low risk of flooding from groundwater sources and it is considered unlikely that any change in groundwater levels will present a significant hazard to the Proposed Development. 5.5 Sewers It is difficult to predict precisely the impact of climate change on sewer flooding; however, the anticipated increase in rainfall intensity may cause greater volumes of rainfall to enter the foul/ combined and surface water sewer network during storm events. AECOM does not anticipate that the risk from the wider sewer system would increase significantly to the point that it would pose a risk to the Site from the wider area; therefore the risk of sewer flooding will remain low. 5.6 Surface Water Run-off Generation and Overland Flow An increase in rainfall intensity will increase surface water runoff rates and volumes, however, as indicated in Section 4.6 the risk from this source of flooding is considered to be very low to low. Climate change must be taken into account when considering surface water runoff generated by development sites. This is usually represented by increasing the peak rainfall intensities. An increase in intensity will increase surface water runoff rates and volumes and therefore the design of the Site s drainage infrastructure will need to take this into account in accordance with the guidance of the NPPF, the Environment Agency and the SFRA. Page 19

25 6. Proposed Flood Risk Management Measures 6.1 Mitigation against Tidal Flooding As discussed in Section 4.2, flood defences along the River Medway protect the Site against tidal flooding (based on still water levels) for events that have a 0.5% annual probability of occurring. Since the application site is protected from flooding through extensive primary and secondary flood defences, the risk of tidal flooding is considered to be low. The undefended modelled flood water levels in Table 4.2 suggest that the Site is at risk of being flooded to significant depths (>0.5 m) in the event of a breach in both the primary and secondary defences. Although the risk to the Site in the event of a breach is high, the probability of a breach occurring is considered to be very low. A Flood Warning and Evacuation Plan (FWEP) will be prepared for the combined site when the Damhead Creek 2 station is built. A flood warning procedure is already in place for the existing power station to ensure those present have enough time to evacuate the site should a significant flood risk occur. A FWEP will be prepared for both the construction and operational phases of the new development. ScottishPower currently subscribe to the Environment Agency s Flood Warning Service in the area. If notified of a possible flood event ScottishPower shut mitigation land drainage valves are to prevent backflow flooding within the site. Areas 1 and 2 within the Site boundary sit within the Tidal River Medway and Medway Estuary Flood Warning Area. The Flood Warning Area has two levels of warning codes: Flood Alert; and Severe Flood Warning. Tidal flood warnings are issued based on forecast information, and therefore the lead time provided is longer than that provided for fluvial flooding. The Environment Agency aim to issue tidal Flood Warnings a minimum of 6 hours in advance, but depending on confidence in the forecast they could be issued 24 or even 36 hours in advance. Tidal flood warnings are triggered by a combination of forecast high water (astronomical tide level plus any additional surge), forecast wind speed, and forecast wind direction. Due to the flood defences in place, it is quite rare that Flood Warnings are issued for tides. It is more common to issue the lowerlevel Flood Alerts, which are issued when the Environment Agency expect wave splash and wind-blown spray to cause localised pooling of water on land but no actual flooding of properties. The Environment Agency issues direct flood warnings using their Flood Warnings Direct system (FWD). FWD is a computerised system which issues voice messages, faxes, pager and text messages. On receipt of a Flood Alert warning from the FWD, the occupants at the Site are made aware of the possibility of flooding and prepare for possible evacuation. The scaling down of activities at the Site at this time is also be considered. On receipt of a Severe Flood Warning, the Site would be evacuated. 6.2 Mitigation against Fluvial Flooding The Site is considered to be at low risk of fluvial flooding, therefore no mitigation has been recommended. 6.3 Mitigation against Artificial Flooding The Proposed Development site is considered to be at low risk of artificial flooding. No further mitigation measures would therefore be required to manage the risk of artificial flooding to the Proposed Development. Page 20

26 6.4 Mitigation against Groundwater Flooding The Proposed Development site is considered to be at low risk of groundwater flooding. No further mitigation measures would therefore be required to manage the risk of groundwater flooding to the Proposed Development. 6.5 Mitigation against Pluvial Flooding and from Drainage Infrastructure The risk from pluvial flooding and from drainage infrastructure is considered to be low at the site and the flood risk associated with pluvial flooding, presented in Section 4.6, is likely to remain the same following redevelopment of the site. As a precaution, flood resilience measures can be incorporated into the development to minimise the amount of damage and reduce the recovery time in the unlikely case of the site becoming inundated. AECOM recommends that during construction the opportunity be taken, where possible, to adopt flood resilient design techniques for the Proposed Development (e.g. flood sensitive equipment raised a minimum of 600 mm above surrounding ground levels etc.). Page 21

27 7. Surface Water Management The NPPF requires that the new development should not increase flood risk both on the Site and in the area surrounding it. Surface water runoff should therefore not exceed the volumes already generated by the existing site and betterment should be provided where possible. Both the NPPF and the Medway SFRA include guidance that promotes the use of SuDs within new developments. 7.1 Existing Conditions The existing site is approximately 309,000 m 2 (30.9 ha) of which approximately 47,000 m 2 (4.7 ha) comprises impermeable surfacing (concrete and hardstanding). The remaining site area (262,000 m 2 /26.2 ha) comprises grass and soft landscaping and therefore drains at greenfield rates via natural infiltration to ground. Table 7.1 provides a breakdown of the Site areas and surfacing. Table 7-1 Site Areas and Surfacing Area No. Permeable Area (ha) Impermeable Area (ha) Total Area (ha) No formal drainage information is available for the Site but it is assumed that the small area of hardstanding within Area 1 drains to the surrounding grassed areas and therefore drains at greenfield rates. The impermeable surfacing within Area 2 drains to a private drainage system within the wider industrial estate and enters the drain that runs adjacent to the access road to the east of this area and then runs through the ScottishPower mitigation land and eventually out through the sea wall to Damhead Creek. Existing Runoff from the Site The Scottishpower land holding to the north, shaded purple in Figure 2-2 above, forms part of the red line boundary for the Site but will not be developed initially as part of this planning application and therefore it is assumed that surface water drainage from this area of the Site will continue to drain via existing methods. The land will be retained for future CCS plant, should it ever be required, as part of this planning application. The grey and orange areas (26.8 ha) shown in Figure 2-2 form the main areas of development for DHC2 and comprises approximately 0.6 ha of hardstanding and 26.2 ha of grassland which drains at the greenfield run-off rate. The approximate surface water runoff from the existing impermeable area has been calculated using the Wallingford Procedure, which uses a modified version of the rational method to estimate runoff based on the nature of the ground surface (hard standing, vegetation etc.) and rainfall depth, duration and frequency information for the immediate area. A runoff coefficient of 0.85 for hard standing has been used for the impermeable area. Existing runoff values for the existing hardstanding area in these areas is shown in Table 7-2 as a function of associated rainfall values (Table 7-3). Page 22

28 Table 7-2 Approximate Surface Water Runoff Rates for the Existing Site Areas 1 and 3) (litres/second) Storm Durations (hr) % % % % Table 7-3 Rainfall Values 18 Storm Durations (hr) % % % % In accordance with Table 7-2, the 100 year return period storm with 15 minute duration would yield a runoff value of l/s from a 0.6 ha impermeable area. 7.2 Policy and Stakeholder Requirements There are a number of national and regional policy requirements which need consideration in the design of any drainage strategy for this site to ensure that the development will be sustainable and can, if possible, contribute to a decreased flood risk elsewhere. These are outlined below. National Planning Policy Framework The NPPF requires that the new development should not increase flood risk both on the site and in the area surrounding it. Surface water runoff should therefore not exceed the volumes already generated by the existing site and betterment should be provided where possible. 18 Data from: FEH CD-ROM V3 DDR rainfall modelling (1km 2 grid cell) for the site co-ordinates Page 23

29 Building Standards Regulations 2000 Part H The Building Standards Regulations 2000 Part H 19 requires that surface water runoff be preferentially discharged first to soakaway, then to surface watercourse and finally to sewer. Environment Agency The EA Advisory Comments sets out the requirements for surface water drainage for development sites: 1) Drainage from new developments must not increase flood risk on-site or elsewhere; 2) Runoff should not exceed that of the existing site; 3) Flooding of open spaces during the 30 year rainfall event is acceptable for short periods of time and no flooding of property should occur for the 1 in 100 year rainfall event; and, 4) Sustainable drainage techniques should be used wherever possible. 7.3 Proposed Conceptual Strategy Restricted Surface Water Runoff Rate Following completion of the Proposed Development, the area of impermeable surfacing within the main development area (10.4 ha DHC2 development area shaded grey in Figure 2-2) will increase from 0.6 ha to approximately 6.8 ha (worst case scenario based on the layout and associated permeable and impermeable areas as shown in Annex D) and as a consequence of this surface water run-off from the Site, if not managed, will increase. The remaining Site area will remain as permeable soft landscaping. Consultation with Medway Council has stated that run-off from developed areas of the Site, as a rule of thumb, should be restricted to the greenfield runoff rate of approximately 7 litres per second per hectare. Based on this greenfield run-off rate the restricted surface water discharge has been calculated as follows: Impermeable area of 6.8 ha x 7 l/s = 47.6 l/s Sustainable Drainage Systems There are a number of SuDS options which could be utilised to both manage and attenuate runoff, however, consideration of site characteristics must be made to ensure that the drainage system is compatible. The NPPF and the Environment Agency encourage the use of such systems where practicable, to ensure a reduction in flood risk to the site and elsewhere, and to provide water quality benefits. It is likely, based on ground conditions across the majority of the Site (underlaid with Alluvium) that infiltration based SuDs methods would be unsuitable, however SuDs such as storage/ attenuation basins and closed pervious paving systems should be considered. Surface Water Attenuation Volumes In order to limit the discharge of surface water runoff to the Greenfield runoff rate of 7 l/s/ha, surface water attenuation will be required. A restriction rate of 47.6 l/s has been used in Micro Drainage modelling software to calculate an indicative storage volume that would be required to store surface water for rainfall events up to the 1% AEP storm event plus climate change (30%) based on a 15 minute duration rainfall event. A storm water basin will be provided to the south east of the Proposed Development to attenuate surface water runoff from the impermeable areas to the greenfield runoff rate, similar to the storm water attenuation system used for the DHC1 power station. The attenuation storage will be sized accordingly 19 Office of the Deputy Prime Minister (2002) The Building Regulations 2000, Drainage and Water Disposal (Approved Document H) Page 24

30 to provide storage for all storms up to and including the 1% AEP (1 in 100 year) critical duration storm event plus climate change (30%) before being pumped into the Damhead Creek. WinDes modelling software was used to estimate the total storage volumes required on Site. Detailed surface water modelling will be required as part of the detailed Site design and the figures below are provided only as an indication of the volumes likely to be required. Table 7-4 presents the minimum and maximum storage volume results obtained. Table 7-4 Indicative Attenuation Storage Requirements Return Period (AEP) Minimum Storage Volume (m 3 ) Maximum Storage Volume (m 3 ) 1% % + 30% climate change allowance During the detailed design phase it may be possible to identify methods to decrease the total impermeable area within the built development from that assumed. For example, as a worst case scenario hardstanding has been assumed beneath the Air Cooler Condenser Unit but in practice it is likely to be gravel or stone to minimise noise from the coolers. Measures such as thisand minimising hard standing in other parts of the site will therefore decrease the volume of storm water attenuation required in the storm water basin. Page 25

31 8. Off-Site and Residual Risks 8.1 Off-Site Impacts The drainage strategy provides storage for up to and including the 1% AEP storm event with a 30% allowance for climate change. This will ensure that the scheme will not increase flood risk elsewhere and should provide betterment over the existing situation. The proposed surface water drainage strategy will therefore meet with the requirements of the NPPF. It is considered that the Proposed Development will not result in any significant offsite flood risk impacts. 8.2 Residual Risks There is a residual risk of flooding from a breach in the tidal flood defences. The Site is protected by both primary sea defences and secondary earth embankments and it would take a breach of both the primary and secondary defences to cause inundation into the site. The probability of this occurring is very low due to regular inspection of the defences to ensure that they remain fit for purpose. A further residual risk to the Site is from the surface water management scheme; this may be due to exceedance of the design event and/or failure of the drainage system. The proposed drainage strategy provides storage for up to and including the 1% AEP storm event with a 30% allowance for climate change however, if a storm event was to occur that exceeds this capacity (e.g. 0.66% and 0.5% AEP return period rainfall events) flooding from the drainage system may occur. Regular maintenance of the drainage system should be undertaken to ensure that the system continues to perform as designed. ScottishPower will adopt the SUDS features once operational and it will be the responsibility of ScottishPower to make sure that the SUDS features are regularly inspected and maintained to ensure their design standard is not compromised over the lifetime of the development. To manage the risk from exceedance flows, the drainage design will need to follow such guidance as CIRIA C to provide flow paths such that any overland flow is directed away from impacting the proposed development. 20 Balmforth D, Digman C, Kellagher R, Butler D (2006), Designing for Exceedance in Urban drainage Good practice, (CIRIA 635) Page 26

32 9. Conclusions The following conclusions can be made with regards to flood risk to the Site and as a result of the Proposed Development: The Environment Agency Flood Zone mapping identifies the Site to be located within Flood Zone 2 and Flood Zone 3, which equates to a medium to high risk of tidal flooding; The Site is afforded protection by primary and secondary tidal flood defences up to the 0.1% AEP flood event, as can be seen in the Environment Agency mapping. Therefore the actual risk of flooding from tidal sources is considered to be low; There is a residual risk of flooding from a breach in the tidal flood defences. Despite this, the likelihood of a breach occurring in both the primary and secondary flood defences during the same flood event is very low due to regular inspection of the defences to ensure that they remain fit for purpose and maintenance by the riparian owners; The risk of fluvial flooding from the drainage ditch within the Site and adjacent to the southern Site boundary is considered to be low; Based on the predictions of the tidal modelling of the North Kent Coast, the risk of fluvial flooding to the Site as a result of climate change will increase. However, the general area within which the site lies is protected by primary sea defences with a crest elevation of 5.7 m AOD or higher and in addition to the primary sea defences, the Site is protected by secondary bunds adjacent to the site, with a crest elevation of circa 5.6 m AOD, therefore the impact of climate change is not expected to impact the Site over the lifetime of the development (approximately 35 years). The risk of flooding from groundwater is considered to be low; The Site is considered to be at low risk of flooding from sewers; The Site is at low risk of flooding from artificial sources; The Site is at low risk of flooding from surface water. A conceptual surface water drainage strategy is included within this FRA to support the application and this incorporates suitable SUDS. Surface water runoff from hardstanding areas within the development area will be limited to a greenfield runoff rate of 7 l/s/ha; Areas within the Site that remain as permeable soft landscaping (grassland etc.) will continue to drain at the greenfield rate as the existing scenario; The required surface water attenuation could be provided via a storm water basin located to the south east of the Site although this will be confirmed at the detailed design stage. Attenuation storage will be provided up to the 1% AEP + 30% climate change and will be pumped to Damhead Creek and/ or local drainage ditches internal to the Site at the restricted rate of 47.6 l/s (or less). The actual discharge rate will be determined during final design and agreed as part of the Environmental Permit for the facility; The residual risk posed to the Proposed Development will be managed by a combination of the following measures: subscription to the Environment Agency Flood Warnings Direct Service; flood resilience measures (being measures that minimise damage and reduce the recovery time following a flood) will be incorporated, where possible, to adopt flood resilient design techniques for the Proposed Development (e.g. flood sensitive equipment raised a minimum of 600 mm above surrounding ground levels etc.); Page 27

33 flood-proofing or flood resistance (being measures to exclude water from specific compartments, plant or other equipment that would otherwise be sensitive to flooding, but which cannot be placed above the level of an anticipated flood); and a Flood warning and Evacuation Plan (FWEP) will be extended to include the new development. The FWEP will include details of evacuation procedures to be implemented if the risk of a breach is considered high, identify evacuation routes and provision of safe refuge in the event staff are unable to be safely evacuated, and will consider both construction and operational phases. The proposed development is a variation to an existing consent and is located on a brownfield site owned by the applicant, which is located within an area identified for employment in the Medway Local Plan. The proposed power station use is classed as Essential Infrastructure in line with NPPF, which is considered appropriate within Flood Zone 3; therefore it is considered that the Propose Development passes the Sequential Test. It is considered that the Proposed Development will provide the local area and region with wider socio-economic benefits (employment of local people and sourcing of local goods, services and contractors, and indirect employment benefits etc.) and also provides electricity generation that strengthens the local and regional grid network, which, in turn, underpins the development of other services within the south east region. It is therefore considered that the Proposed Development passes the Exception Test This FRA provides the evidence and serves to demonstrate that the Proposed Development will remain safe during its lifetime, will not increase flood risk and is, therefore, considered to be acceptable in flood risk terms. Page 28

34 Limitations AECOM Infrastructure & Environment UK Limited (hereafter referred to as AECOM, formerly known as URS) has prepared this Report for the sole use of ScottishPower DCL Limited ( Client ) in accordance with the Agreement under which our services were performed. No other warranty, expressed or implied, is made as to the professional advice included in this Report or any other services provided by AECOM. This Report is confidential and may not be disclosed by the Client nor relied upon by any other party without the prior and express written agreement of AECOM. The conclusions and recommendations contained in this Report are based upon information provided by others and upon the assumption that all relevant information has been provided by those parties from whom it has been requested and that such information is accurate. Information obtained by AECOM has not been independently verified by AECOM, unless otherwise stated in the Report. The methodology adopted and the sources of information used by AECOM in providing its services are outlined in this Report. The work described in this Report was undertaken between October 2014 and December 2015 and is based on the conditions encountered and the information available during the said period of time. The scope of this Report and the services are accordingly factually limited by these circumstances. Where assessments of works or costs identified in this Report are made, such assessments are based upon the information available at the time and where appropriate are subject to further investigations or information which may become available. AECOM disclaim any undertaking or obligation to advise any person of any change in any matter affecting the Report, which may come or be brought to AECOM s attention after the date of the Report. Certain statements made in the Report that are not historical facts may constitute estimates, projections or other forward-looking statements and even though they are based on reasonable assumptions as of the date of the Report, such forward-looking statements by their nature involve risks and uncertainties that could cause actual results to differ materially from the results predicted. AECOM specifically does not guarantee or warrant any estimate or projections contained in this Report. Where field investigations are carried out, these have been restricted to a level of detail required to meet the stated objectives of the services. The results of any measurements taken may vary spatially or with time and further confirmatory measurements should be made after any significant delay in issuing this Report. Copyright This Report is the copyright of AECOM Infrastructure & Environment UK Limited, a wholly owned subsidiary of AECOM. Any unauthorised reproduction or usage by any person other than the addressee is strictly prohibited Page 29

35 Annex A Data Consultation Page 30

36 Product 4 (Detailed Flood Risk) for: Damhead Creek Requested by: Joanne Somerton - AECOM Reference: KSL151124/KR58 Date: 11 December 2015 Contents Flood Map Confirmation Flood Map Extract Model Output Data Data Point Location Map Modelled Flood Outlines Map Defence Details Historic Flood Data Historic Flood Event Map Additional Data Environment Agency Standard Notice The information provided is based on the best data available as of the date of this letter. You may feel it is appropriate to contact our office at regular intervals, to check whether any amendments/ improvements have been made to the data for this location. Should you re-contact us after a period of time, please quote the above reference in order to help us deal with your query. This information is provided subject to the enclosed notice which you should read. Orchard House, Endeavour Park, London Road, Addington, West Malling, Kent, ME19 5SH. kslenquiries@environment-agency.gov.uk

37 Flood Map Confirmation The Flood Map: Our Flood Map shows the natural floodplain for areas at risk from river and tidal flooding. The floodplain is specifically mapped ignoring the presence and effect of defences. Although flood defences reduce the risk of flooding they cannot completely remove that risk as they may be over topped or breached during a flood event. The Flood Map indicates areas with a 1% (0.5% in tidal areas), Annual Exceedance Probability (AEP) - the probability of a flood of a particular magnitude, or greater, occurring in any given year, and a 0.1% AEP of flooding from rivers and/or the sea in any given year. The map also shows the location of some flood defences and the areas that benefit from them. The Flood Map is intended to act as a guide to indicate the potential risk of flooding. When producing it we use the best data available to us at the time, taking into account historic flooding and local knowledge. The Flood Map is updated on a quarterly basis to account for any amendments required. These amendments are then displayed on the internet at At this Site: The Flood Map shows that this site lies within the outline of the 0.5% chance of flooding in any given year from the sea. Enclosed is an extract of our Flood Map which shows this information for your area. Method of production The Flood Map at this location has been derived using detailed tidal modelling of the North Kent Coast, completed in August Orchard House, Endeavour Park, London Road, Addington, West Malling, Kent, ME19 5SH. kslenquiries@environment-agency.gov.uk

38 Flood Map Centred on Damhead Creek Created 11 December 2015 (Ref KSL151124/KR58) Legend Main Rivers Flood Defences Areas Benefiting From Flood Defence Flood Zone 3 Flood Zone 2 Scale 1:10, Meters Environment Agency Copyright and/or database rights All rights reserved. Crown copyright and database rights 2015.All rights reserved. Ordnance Survey licence number Contact us: National Customer Contact Centre, PO Box 544, Rotherham, S60 1BY. Tel: enquiries@environment-agency.gov.uk

39 Model Output Data You have requested flood levels for various return periods at this location. The modelled flood levels for the closest most appropriate model grid cells, any additional information you may need to know about the modelling from which they are derived and/or any specific use or health warning for their use are set out below. Using a 2D TuFLOW model the floodplain has been represented as a grid. The flood water levels have been calculated for each grid cell. A map showing the location of the points from which the data is taken is enclosed. Please note you should read the notice enclosed for your specific use rights. Table 1: Defended Modelled Tidal Flood levels for Annual Exceedance Probability shown in maod Modelled Tidal Flood levels for Annual Exceedance Probability shown in maod Node Location ID National Grid Ref Defended Easting Northing 5% AEP % AEP % AEP % AEP % AEP (2012) Orchard House, Endeavour Park, London Road, Addington, West Malling, Kent, ME19 5SH. kslenquiries@environment-agency.gov.uk

40 Table 2: Undefended Modelled Tidal Flood levels for Annual Exceedance Probability shown in maod Modelled Tidal Flood levels for Annual Exceedance Probability shown in maod Node Location ID National Grid Ref Undefended Easting Northing 5% AEP % AEP % AEP % AEP % AEP Data taken from North Kent Coast Modelling and Mapping Study, completed by JBA Consulting, in August There are no health warnings or additional information for these levels or the model from which they were produced. Orchard House, Endeavour Park, London Road, Addington, West Malling, Kent, ME19 5SH. kslenquiries@environment-agency.gov.uk

41 Modelled Node Locations Centred on Damhead Creek Created 11 December 2015 (Ref KSL151124/KR58) Legend NodeLocations Main Rivers Scale 1:10, Meters Environment Agency Copyright and/or database rights All rights reserved. Crown copyright and database rights 2015.All rights reserved. Ordnance Survey licence number Contact us: National Customer Contact Centre, PO Box 544, Rotherham, S60 1BY. Tel: enquiries@environment-agency.gov.uk

42 Defended Modelled Tidal Flood Outlines Centred on Damhead Creek Created 11 December 2015 (Ref KSL151124/KR58) Legend Main Rivers 5% AEP (2012) 0.1% AEP (2012) Annual Exceedance Probability (AEP) The probability of a flood of a particular magnitude, or greater occuring in any given year. Scale 1:10, Meters Environment Agency Copyright and/or database rights All rights reserved. Crown copyright and database rights 2015.All rights reserved. Ordnance Survey licence number Contact us: National Customer Contact Centre, PO Box 544, Rotherham, S60 1BY. Tel: enquiries@environment-agency.gov.uk

43 Defended Modelled Tidal Flood Outlines Centred on Damhead Creek Created 11 December 2015 (Ref KSL151124/KR58) Legend Main Rivers 0.5% AEP (2012) 0.5% AEP (2070) 0.5% AEP (2115) Annual Exceedance Probability (AEP) The probability of a flood of a particular magnitude, or greater occuring in any given year. Scale 1:10, Meters Environment Agency Copyright and/or database rights All rights reserved. Crown copyright and database rights 2015.All rights reserved. Ordnance Survey licence number Contact us: National Customer Contact Centre, PO Box 544, Rotherham, S60 1BY. Tel: enquiries@environment-agency.gov.uk

44 Undefended Modelled Tidal Flood Outlines Centred on Damhead Creek Created 11 December 2015 (Ref KSL151124/KR58) Legend Main Rivers 5% AEP (2012) 0.1% AEP (2012) Annual Exceedance Probability (AEP) The probability of a flood of a particular magnitude, or greater occuring in any given year. Scale 1:10, Meters Environment Agency Copyright and/or database rights All rights reserved. Crown copyright and database rights 2015.All rights reserved. Ordnance Survey licence number Contact us: National Customer Contact Centre, PO Box 544, Rotherham, S60 1BY. Tel: enquiries@environment-agency.gov.uk

45 Undefended Modelled Tidal Flood Outlines Centred on Damhead Creek Created 11 December 2015 (Ref KSL151124/KR58) Legend Main Rivers 0.5% AEP (2012) 0.5% AEP (2070) 0.5% AEP (2115) Annual Exceedance Probability (AEP) The probability of a flood of a particular magnitude, or greater occuring in any given year. Scale 1:10, Meters Environment Agency Copyright and/or database rights All rights reserved. Crown copyright and database rights 2015.All rights reserved. Ordnance Survey licence number Contact us: National Customer Contact Centre, PO Box 544, Rotherham, S60 1BY. Tel: enquiries@environment-agency.gov.uk

46 Defence Details The site is currently defended to a 1 in 1000 year standard of protection. Defences are comprised of raised earth embankments and concrete sea walls. The Environment Agency does not currently have any planned improvement works to the defences in this area. Orchard House, Endeavour Park, London Road, Addington, West Malling, Kent, ME19 5SH. kslenquiries@environment-agency.gov.uk

47 Historic Flood Data We hold records of historic flood events from rivers and the sea. Information on the floods that may have affected the area local to your site are provided on the enclosed map (if relevant). Flood Event Data Please note that our records are not comprehensive. We would therefore advise that you make further enquiries locally with specific reference to flooding at this location. You should consider contacting the relevant Local Planning Authority and/or water/sewerage undertaker for the area. We map flooding to land, not individual properties. Our historic flood event record outlines are an indication of the geographical extent of an observed flood event. Our historic flood event outlines do not give any indication of flood levels for individual properties. They also do not imply that any property within the outline has flooded internally. Please be aware that flooding can come from different sources. Examples of these are: - from rivers or the sea; - surface water (i.e. rainwater flowing over or accumulating on the ground before it is able to enter rivers or the drainage system); - overflowing or backing up of sewer or drainage systems which have been overwhelmed, - groundwater rising up from underground aquifers Currently the Environment Agency can only supply flood risk data relating to the chance of flooding from rivers or the sea. However you should be aware that in recent years, there has been an increase in flood damage caused by surface water flooding or drainage systems that have been overwhelmed. Orchard House, Endeavour Park, London Road, Addington, West Malling, Kent, ME19 5SH. kslenquiries@environment-agency.gov.uk

48 Historic Flood Outlines Centred on Damhead Creek Created 11 December 2015 (Ref KSL151124/KR58) Legend Main Rivers Feb 1953 Scale 1:10, Meters Environment Agency Copyright and/or database rights All rights reserved. Crown copyright and database rights 2015.All rights reserved. Ordnance Survey licence number Contact us: National Customer Contact Centre, PO Box 544, Rotherham, S60 1BY. Tel: enquiries@environment-agency.gov.uk

49 Additional Information Use of Environment Agency Information for Flood Risk / Flood Consequence Assessments Depending on the enquiry, we may also provide advice on other issues related to our responsibilities including flooding, waste, land contamination, water quality, biodiversity, navigation, pollution, water resources, foul drainage or Environmental Impact Assessment. In England, you should refer to the Environment Agency s Flood Risk Standing Advice, the technical guidance to the National Planning Policy Framework and the existing PPS25 Practice Guide for information about what flood risk assessment is needed for new development in the different Flood Zones. These documents can be accessed via: You should also consult the Strategic Flood Risk Assessment produced by your local planning authority. You should note that: 1. Information supplied by the Environment Agency may be used to assist in producing a Flood Risk / Consequence Assessment (FRA / FCA) where one is required, but does not constitute such an assessment on its own. 2. This information covers flood risk from main rivers and the sea, and you will need to consider other potential sources of flooding, such as groundwater or overland runoff. The information produced by the local planning authority referred to above may assist here. 3. Where a planning application requires a FRA / FCA and this is not submitted or deficient, the Environment Agency may well raise an objection. 4. For more significant proposals in higher flood risk areas, we would be pleased to discuss details with you ahead of making any planning application, and you should also discuss the matter with your local planning authority. Orchard House, Endeavour Park, London Road, Addington, West Malling, Kent, ME19 5SH. kslenquiries@environment-agency.gov.uk

50 Surface Water We have provided two national Surface Water maps, under our Strategic Overview for flooding, to your Lead Local Flood Authority Medway Council, who are responsible for local flood risk (i.e. surface runoff, ground water and ordinary watercourse), which alongside their existing local information will help them in determining what best represents surface water flood risk in your area. Medway Council have reviewed these and determined what it believes best represents surface water flood risk. You should therefore contact this authority so they can provide you with the most up to date information about surface water flood risk in your area. You may also wish to consider contacting the appropriate relevant Local Planning Authority and/or water/sewerage undertaker for the area. They may be able to provide some knowledge on the risk of flooding from other sources. We are working with these organisations to improve knowledge and understanding of surface water flooding. Orchard House, Endeavour Park, London Road, Addington, West Malling, Kent, ME19 5SH.

51 Standard Notice [not for use with Special Data, Personal Data or unlicensed 3 rd party rights] Information warning We (The Environment Agency) do not promise that the Information supplied to You will always be accurate, free from viruses and other malicious or damaging code (if electronic), complete or up to date or that the Information will provide any particular facilities or functions or be suitable for any particular purpose. You must ensure that the Information meets your needs and are entirely responsible for the consequences of using the Information. Please also note any specific information warning or guidance supplied to you. Permitted use The Information is protected by intellectual property rights and whilst you have certain statutory rights which include the right to read the Information, you are granted no additional use rights whatsoever unless you agree to the licence set out below. Commercial use is subject to payment of a 50 licence fee (+VAT) for each person seeking the benefit of the licence, except for use as an Environment Agency contractor or for approved media use. To activate this licence you do not need to contact us (unless you need to pay us a Commercial licence fee) but if you make any use in excess of your statutory rights you are deemed to accept the terms below. Licence We grant you a worldwide, royalty-free, perpetual, non-exclusive licence to use the Information subject to the conditions below. You are free to: copy, publish, distribute and transmit the Information adapt the Information exploit the Information commercially, for example, by combining it with other Information, or by including it in your own product or application You must (where you do any of the above): acknowledge the source of the Information by including the following attribution statement: Contains Environment Agency information Environment Agency and database right ensure that you do not use the Information in a way that suggests any official status or that We endorse you or your use of the Information ensure that you do not mislead others or misrepresent the Information or its source or use the Information in a way that is detrimental to the environment, including the risk of reduced future enhancement ensure that your use of the Information does not breach the Data Protection Act 1998 or the Privacy and Electronic Communications (EC Directive) Regulations 2003 These are important conditions and if you fail to comply with them the rights granted to you under this licence, or any similar licence granted by us will end automatically. No warranty The Information is licensed as is and We exclude all representations, warranties, obligations and liabilities in relation to the Information to the maximum extent permitted by law. We are not liable for any errors or omissions in the Information and shall not be liable for any loss, injury or damage of any kind caused by its use. We do not guarantee the continued supply of the Information. Governing Law This licence is governed by the laws of England and Wales. Definitions + Information means: the information that is protected by copyright or by database right (for example, literary and artistic works, content, data and source code) offered for use under the terms of this licence. + Commercial means: - offering a product or service containing the Information, or any adaptation of it, for a charge, or - Internal Use for any purpose, or offering a product or service based on the Information for indirect commercial advantage, by an organisation that is primarily engaged in trade, commerce or a profession Orchard House, Endeavour Park, London Road, Addington, West Malling, Kent, ME19 5SH. kslenquiries@environment-agency.gov.uk

52 Somerton, Joanne From: mumby, priscilla Sent: 11 January :43 To: Somerton, Joanne Cc: Mike Watson Subject: RE: Enquiry - Land near Damhead Creek - Flood Risk Assessment Joanne, Do you have any more information regarding the proposed development? Size, type, etc. I assume it s industrial. I believe there is a site wide drainage strategy for the area the case officer should be able to advise further on this as it will be attached to the outline application. A general rule of thumb here would be to attenuate discharges to ditches to the greenfield runoff rate (7 litres per second per hectare). Most of the ditches here are under the remit of the Lower Medway Internal Drainage Board (Clerk and Engineer is Mike Watson, Cc d). They will also review any planning application for the area and advise of any additional requirements, but we d need a more detailed location plan to ascertain which ditches would be impacted. Consent under the Land Drainage Act 1991 will likely be required for any works to the ditches/connections/outfalls. We d recommend rainwater harvesting where possible to deal with water at source and limit the impact on the ditch network. I m not aware of any local drainage issues but Mike may be able to advise further. Best regards, Priscilla Priscilla Mumby Flood, Drainage & Special Projects Officer Tel: Fax: priscilla.mumby@medway.gov.uk From: Somerton, Joanne [mailto:joanne.somerton@aecom.com] Sent: 08 January :16 To: mumby, priscilla Subject: RE: Enquiry - Land near Damhead Creek - Flood Risk Assessment Importance: High Priscilla Please see the string of s below. We are looking to submit the report in the next week or so and are still awaiting a response from the Council Kind Regards Jo Somerton MSc BSc (Hons) Senior Flood Risk Consultant, Flood and Water Management DD: +44 (0) Mob: +44(0) joanne.somerton@aecom.com 1

53 Annex B Topographic Survey Page 31

54 EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL WT EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL MH MH MH MH MH MH EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL 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EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL StkdSTS EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL TPS EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL PF PF PF PF PF PF PF PF PF PF PF PF PF PF PF PF PF PF PF NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT NEWT STS STS STS STS STS EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL CONC CONC CONC CONC EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL PAL PAL PAL PAL PAL PAL PAL PAL PAL PAL PAL PAL 8 39 PAL PAL PAL PAL 4 03 PAL PAL PAL NF NF NF NF NF (2) MON WELL MON WELL BB BB BB BB BB BB BB BB BB BB BB BB BB BB EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB TB NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF NF (1) EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL EGL 9 73 EGL EGL 7 79 EGL 6 06 EGL 5 31 EGL 4 97 EGL EGL EGL TB TB TB TB TB TB TB TB TB TB TB TB TB 5 76 TB TB TB TB 1 70 BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB BB 9 51 BB BB BB BB BB BB BB BB NF NF NF NF NF NF NF NF NF NF NF 9 53 NF NF NF NF NF NF 3 52 NF 2 91 NF PF PF PF PF PF18 12 PF17 28 PF16 56 PF PF PF PF PF11 33 PF PF PF PF7 33 PF PF PF PF PF PF STS STS 9 22 STS STS STS STS STS STS STS STS date: drawn: revision no. - EGL 04 dwg no. job no. SP003 Damhead Creek Power Station Levels & labels scale: No scale date: NR drawn by: drawing title: project: t: e: enquiries@siteteamservices.com revision: NOTES: xxxx client:

55 Annex C Plant Layout Page 32

56 Client: Prepared: Site/Project: DAMHEAD CREEK 2 POWER STATION - SECTION 36 CONSENT VARIATION Title: PROPOSED CCGT WITH PEAKING PLANT SCHEME INDICATIVE LAYOUT Date: Jan 16