Appendix 7.A Flood Risk Assessment Pro-forma

Transcription

1 Appendix 7.A Flood Risk Assessment Pro-forma Entec UK Limited

2 Entec UK Limited

3 1 PPS25 Flood Risk Assessment Pro-forma 1. Development description and location 1a. What type of development is proposed and where will it be located? A wind farm comprising 7 turbines and associated infrastructure, details of which are presented in Chapter 3 of the Environmental Statement (ES), located approximately 7km to the south of Market Harborough and 1.4km south west of the village of Kelmarsh. The central grid reference of the site is approximately SP b. What is its vulnerability classification? Wind turbines are classed as Essential Infrastructure according to PPS25. They are designed for continued exposure to the elements and suitable for use in a marine environment. The control building for the wind farm is also considered Essential Infrastructure, while the remaining infrastructure of the development, for example, the access track, is considered to be of Low Vulnerability. 1c. Please provide evidence that the Sequential Test or Exception Test has been applied in the selection of this site for this development type? The development site is located within the lowest Flood Risk Zone, Zone 1, suitable for all development types (see paragraph of ES). 2. Definition of the flood hazard 2a. What sources of flooding could affect the site? (see Annex C PPS25). Flooding from River Ise: the fluvial flood risk is confined along the route of the River Ise in the eastern half of the development site where there is a risk of minimal overtopping of the stream s banks. There are no other sources of flooding identified on the development site. The remainder of the development site is relatively permeable (it is undeveloped and comprises fields and woodland) and slopes toward the channel of the River Ise, hence any rainfall falling on the site will be quickly absorbed or diverted to the River Ise, such that the risk of surface water flooding is negligible. Shallow buried pipes also encourage drainage of the fields for agricultural use. Any potential ponding is likely to occur within the fluvial flood zone indicated by the Environment Agency. Groundwater flooding is unlikely as the underlying geology is predominantly a Non-Aquifer (Jurassic Whitby Mudstone) that is unlikely to yield large quantities of groundwater. There are no sewers, reservoirs or canals on or in close proximity to the development site that would be a source of flooding. 2b. For each identified source, describe how flooding would occur, with reference to any historic records wherever these are available. During intense rainfall there is a risk of the River Ise channel exceeding its capacity. The Flood Zones provided by the Environment Agency indicate that any bank overspill will be confined close to the channel as the floodplain is very narrow. l:\data\projects\ea-210\23125 kelmarsh wind farm (subfolder)\g030 general\environmental statement\es final\volume 3, appendices\appendix 7a pps25 fra pro forma.doc Entec UK Limited 21 January 2010

4 2 2c. What are the existing surface water drainage arrangements for the site? The development site is entirely agricultural land. Small ditches are present on the perimeter of fields that flow into the River Ise, which flows from west to east through the centre of the development site. The location of the ditches and River Ise is presented on Figure 7.1 of the ES. Shallow buried plastic pipes, or underdrainage, are located in the agricultural fields that divert flow into the perimeter field ditches and the River Ise. The approximate location of these drains is shown in Figure 7.3 of the ES. 3. Probability 3a Which flood zone is the site within? The development site is predominantly within Flood Zone 1, with a small strip of Flood Zone 3 present along the eastern section of the River Ise. 4. Climate change 4a How is flood risk at the site likely to be affected by climate change? Potential increase in rainfall, as described in paragraphs and of the ES, could increase the potential for flooding from land and from the River Ise. However, as the development site is predominantly located within Flood Zone 1, this increase in flood risk is considered negligible on the balance of probabilities. 5. Detailed development proposals 5a Please provide details of the development layout, referring to the relevant drawings. Refer to Chapter 3 of the ES and Figure b Where appropriate, demonstrate how land-uses most sensitive to flood damage have been placed in areas within the site that are at least risk of flooding. No development takes place within medium or high risk flood zones, with the exception of the use of one existing watercourse crossing over the River Ise. 6. Flood risk management measures 6a. How will the site be protected from flooding, including the potential impacts of climate change, over the development s lifetime? l:\data\projects\ea-210\23125 kelmarsh wind farm (subfolder)\g030 general\environmental statement\es final\volume 3, appendices\appendix 7a pps25 fra pro forma.doc Entec UK Limited 21 January 2010

5 3 The development site lies within a low risk flood zone with high surface permeability as it is predominantly pasture used for grazing. Even with the increase in rainfall the potential flood risks over the future of the wind farm are considered low. New access roads and hardstandings will be constructed of granular material which encourages infiltration and reduces peak flows. Turbine foundations will be reinstated so that the finished footprint will comprise of the tower and crane pad, an area of granular material for siting of cranes and maintenance vehicles. Runoff from impermeable surfaces on the site such as the control building will be via drainage ditches/swales for attenuation and will be discharged to surrounding vegetation following treatment for sediment removal. 7. Off site impacts 7a How will you ensure that your proposed development and the measures to protect your site from flooding will not increase flood risk elsewhere? Paragraphs to and to of the ES describe the sustainable drainage/trackside drains that will be implemented so that runoff from the development site is not increased. Surface water runoff will be discharged into surrounding vegetation in a controlled manner after treatment for removal of sediments. Drainage systems will be designed to cope with storm events as part of the detailed drainage design. Paragraph describes the recommended measures for reviewing flood risk at the crossing point of the River Ise, which includes assessment of flood conditions prior to use of crossing if flooding is predicted. 8. Residual risks 8a What flood-related risks will remain after you have implemented the measures to protect the site from flooding? No residual risks occur. Section 7.7 of the ES concludes that changes to the hydrology from the development will only result in localised changes that are not significant. As the site is within Flood Zone 1 the risk of flooding is already low. Mitigation measures will prevent increased runoff from the site, and recommended measures for assessment of flood conditions will prevent risks from use of the crossing which is in the higher Flood Zone 3. 8b How, and by whom, will these risks be managed over the lifetime of the development? Construction method statements will be prepared by the contractor awarded the construction work, detailing the proposed drainage control measures for the wind farm construction. Regular visual monitoring of flows during construction and operation of the wind farm will be carried out by the developer (or contractor on behalf of the developer). Chapter 7 of the ES describes the mitigation measures for hydrology. l:\data\projects\ea-210\23125 kelmarsh wind farm (subfolder)\g030 general\environmental statement\es final\volume 3, appendices\appendix 7a pps25 fra pro forma.doc Entec UK Limited 21 January 2010

6 Laura Fielding 02/12/ :48 To: "Hambrook, Dawn" cc: Martin Subject: RE: Wind farm - Kelmarsh Dear Dawn Thanks for your help with this Kind Regards Laura Laura Fielding MSc Senior Hydrologist En tec Entec UK Ltd, Pacific House, Imperial Way Reading, RG2 0TD Tel: +44 (0) Mob: fiell@entecuk.co.uk Consider the environment. Please don't print this unless you really need to. - Entec s new Flood Risk Management website "Hambrook, Dawn" <dawn.hambrook@environment-agency.gov.uk> "Hambrook Hambrook, Dawn" <dawn dawn.hambrook hambrook@envi ronment-agency agency.gov gov.uk > 02/12/ :42 To: <fiell@entecuk.co.uk> cc: Subject: RE: Wind farm - Kelmarsh Laura, The example of the FRA format that you attached will be sufficient for the Kelmarsh site. Best regards Dawn From: fiell@entecuk.co.uk [mailto:fiell@entecuk.co.uk] Sent: 27 November :35 To: Hambrook, Dawn Cc: woodm@entecuk.co.uk Subject: Re: Wind farm - Kelmarsh Click here to report this as spam. Dear Dawn Many thanks for your . I attached a table to the I sent in to Rachael which I have used in the past to address flood risk issues at wind farm sites. This is because the impact on flood risks is

7 generally negligible from the wind farm footprint, and surface water drainage is designed as standard within the layout design to be sustainable and cope with storm events. I would like to discuss the scope of a FRA for this site, particularly as the wind farm elements will all be located within Flood Zone 1. Would it be possible to discuss this with you when you are next available? My contact number is , alternatively I could call you tomorrow? Many Thanks Laura "Hambrook Hambrook, Dawn" <dawn dawn.hambrook hambrook@environment -agency agency.gov gov.uk uk> 27/11/ :22 To: cc: Subject: <fiell@entecuk.co.uk> Wind farm - Kelmarsh Laura, Thank you for your . <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> I have included some further details for your attention. The developer should state whether the application is full or outline. Prior to investing resources in completing a FRA, applicants are advised to contact the Local Planning Authority (LPA) and discuss how the flood risk Sequential Test as set out in Planning Policy Statement 25 (PPS25) will affect the proposed development. It is possible that the development will be inappropriate and be refused planning permission irrespective of any FRA. Advice on the evidence required to show that the Sequential and Exception Test has been properly applied is set out in the Sequential Test table within the Environment Agency's Standing Advice on development and flood risk and in the draft Practice Guide to PPS25. The Environment Agency may require evidence that the Sequential Test has been properly applied before commenting in detail on FRAs for development in this category. Please refer to EA standing advice ( ). Assessments - General The FRA should consider all aspects of flood risk for proposed development and potential impact on people and property within the catchment. The applicant should refer to Annex C and Annex E of PPS25. Fluvial Flood Risk Please make sure that no development takes place in the flood zone as indicated on the map. Surface Water Drainage The pre-development surface water calculations should be determined using IOH124. Developer can refer to EA and Defra document W5-074 "preliminary rainfall management for developments" version D (PRRMD v. D) for guidance.

8 Post development surface water should be calculated using micro-drainage or similar software. Once both pre and post development surface water has been determined the design of the development should assist in matching or reducing post volume and rate of runoff to pre-development. Approved Document Part H of the Building Regulations 2000 establishes a hierarchy for surface water disposal, which encourages a SUDS approach. Under Approved Document Part H the first option for surface water disposal should be the use of SUDS, which encourage infiltration e.g. soakaways or infiltration trenches. In all cases, it must be established that these options are feasible, can be adopted and properly maintained and would not lead to any other environmental problems. For example, using soakaways or other infiltration methods on contaminated land carries groundwater pollution risks and may not work in areas with a high water table. Where the intention is to dispose to soakaway, these should be shown to work through an appropriate assessment carried out under Building Research Establishment (BRE) Digest 365. The design will inevitably require attention of excess runoff, this will need to be detailed in the FRA with information such as location, full capacity volume and release volumes and rates. The attenuation facilities should also be suitable for climate change increases in volume and rate of precipitation. The drainage scheme proposed should provide a sustainable drainage strategy to include SUDS elements with attenuation, storage and treatment capacities incorporated as detailed in the CIRIA SUDS Manual (C697). Further information on SUDS can be found in; PPS25 page 33 Annex F PPS25 Practice Guide in the CIRIA C522 document Sustainable Drainage Systems-design manual for <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />England and Wales in the CIRIA C697 document SUDS manual the Interim Code of Practice for Sustainable Drainage Systems. The Interim Code of Practice provides advice on design, adoption and maintenance issues and a full overview of other technical guidance on SUDS. The Interim Code of Practice is available on both the Environment Agency's web site at: and CIRIA's web site at Drainage and Maintenance The long term maintenance and/or adoption proposals for every element of the drainage system proposed on the site should be included for the lifetime of the development. Overland Flood Flow Consideration that the design for surface water may fail and as such a backup plan should be designed. Overland floodwater should be routed away from vulnerable areas. There are excepted depths and rates of flow these are contained in Environment Agency and Defra document FD2320/TR2 "Flood Risk Assessment Guidance for New Developments Phase 2". A further consideration is safe egress and safe access for emergency services when site is flooded. If the agent or applicant wishes to discuss any issues relating to the above information, please contact Dawn Hambrook on

9 Dawn Hambrook Development Control Officer Welland and Nene Environment Agency Nene House, Pytchley Lodge Road, Kettering, Northamptonshire, NN15 6JQ Tel: Mob: Fax: Information in this message may be confidential and may be legally privileged. If you have received this message by mistake, please notify the sender immediately, delete it and do not copy it to anyone else.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> We have checked this and its attachments for viruses. But you should still check any attachment before opening it. We may have to make this message and any reply to it public if asked to under the Freedom of Information Act, Data Protection Act or for litigation. messages and attachments sent to or from any Environment Agency address may also be accessed by someone other than the sender or recipient, for business purposes. If we have sent you information and you wish to use it please read our terms and conditions which you can get by calling us on Find out more about the Environment Agency at