Report No. 724/01r2
FLOOD RISK ASSESSMENT REPORT
AT
S O U T H P A R K M I L L S P U D S E Y
ON BEHALF OF
A C R I V A R N L T D
OCTOBER 2013
ARP ASSOCIATES CHARTERED CONSULTING ENGINEER
Northwest House • 5/6 Northwest Business Park • Servia Hill • Leeds LS6 2QH Telephone: 0113 2458498 • Fax: 0113 2443864 email: [email protected] • www.arpassociates.co.uk
C O N T E N T S
Page 1.0 Introduction 3 2.0 Walkover Survey General 2.1 - 2.3 4 Current Use 2.4 - 2.5 4 Boundaries 2.6 5 Topography and Vegetation 2.7 5 Drainage 2.8 - 2.9 5 3.0 Environment Agency Consultation 6 4.0 Water Authority Consultation 7 5.0 Land Drainage Authority Consultation 8 6.0 Material Consideration in Respect of NPPF and TG Flood Classification 6.1 - 6.2 9 End Use 6.3 - 6.4 9 Sequential Test 6.5 - 6.6 9 Flood Sources 6.7 - 6.13 10 - 11 Climate Change 6.14 - 6.16 11 Flood Mitigation 6.17 12 Sustainable Drainage 6.18 - 6.19 12 - 13 Drainage 6.20 13 Existing Surface Water Run-off 6.21 13 Proposed Surface Water Drainage 6.22 13 - 14 Foul Drainage 6.23 14 Emergency Egress in Times of Flood 6.24 - 6.25 14 7.0 Comment 15 - 16
APPENDICES Appendix A Site Location Plan Appendix B Environment Agency Consultation Appendix C Water Authority Consultation Appendix D Land Drainage Authority Consultation Appendix E Proposed Development Layout Appendix F Indicative Surface Water Drainage Calculations
2 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 1.0 INTRODUCTION
1.1 Acrivarn Ltd are considering sale of South Park Mills off Hare Lane, Pudsey with a view to redevelopment for residential properties. It was considered appropriate for a Flood Risk Assessment Report to be prepared on the site to supplement any Planning Application for the proposed development.
1.2 It is within the general development strategy of the country for development in areas where there is a risk of flooding to be assessed to avoid unnecessary increase in the requirement for flood defence. Under the National Planning Policy Framework (NPPF) and the accompanying Technical Guidance (TG), consultation is required with the Environment Agency, Land Drainage Authority and Water Authority and a Flood Risk Assessment Report should be prepared considering the development proposals and make recommendations for any flood mitigation measures.
1.3 ARP Associates have been appointed by to carry out an assessment of the site, implement appropriate consultations and prepare a Flood Risk Assessment Report, in accordance with NPPF, to satisfy the requirements of the Planning Authority.
1.4 The consultations and walkover survey have been carried out in October 2013.
1.5 This assessment has been prepared for the sole use and reliance of the Client and shall not be relied upon or transferred to any other parties without the written authorisation of ARP Associates. No responsibility will be accepted where this report is used, either in its entirety or in part, by any other party.
3 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 2.0 WALKOVER SURVEY
General
2.1 The site is located at Ordnance Survey Grid Reference SE226 316 and is approximately 1.5km to the south of the centre of Pudsey and 7km to the West of Leeds City centre. The site is basically rectangular and extends to an area of approximately 1.5 hectares.
2.2 The site is located at the bottom of the steeply sloping Hare Lane from the South side of Pudsey. At the end of Hare Lane, the road bends into the site with South Park Terrace residential housing on the northeastern corner. There is no obvious positive drainage system within Hare Lane and, during times of heavy storm, water is anticipated to run down the steep slope and into the site.
2.3 A site location plan is presented in Appendix A.
Current Use
2.4 The site is occupied by a series of buildings and hardstanding areas across the majority of the site and this has positive drainage systems with gutters, downpipes and, what appears to be, an underground positive system. Manholes are present on the site for foul drainage from the South Park Terrace residential houses and the site buildings and connecting to a sewer, which runs across the Southern part of the site, and for surface water drainage which will connect to watercourse.
2.5 The most Easterly part of the site is rough grassland, whilst a former building on the Southern area has been partially demolished in the past leaving this an open flat area on the lower part of the site.
4 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 Boundaries
2.6 The boundaries on the north, east and west of the site are formed by hedgerows and trees with a timber post and rail fence beyond. The southern boundary abuts Pudsey Beck which is flowing in a west to east direction. It appears that a public footpath may be present between the site boundary and the Beck.
Topography and Vegetation
2.7 The site falls relatively steeply from the northern boundary to the southern boundary, although the area adjacent to the Beck is flat.
Drainage
2.8 Surface water run-off from the site and the northern hard paved road area of Hare Lane will discharge into Pudsey Beck adjacent to the southern boundary of the site via a positive drainage system. It is also known that there are some tanks on the site which are adjacent to the Beck, and it is probable that these collected water in the past and allowed discharge directly into the watercourse.
2.9 Pudsey Beck is of rectangular section of varying width, but generally around 1.9m deep adjacent to the site.
5 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 3.0 ENVIRONMENT AGENCY CONSULTATION
3.1 A consultation was requested from the Environment Agency and a copy of their response, reference RFI/2013/27259 dated 8 th October 2013, is presented in Appendix B for reference purposes.
3.2 The Environment Agency have confirmed that this site is generally within Flood Zone 1, apart from the area immediately adjacent to Pudsey Beck, which is classified as Flood Zone 3 (high risk) on the Environment Agency Flood Map. Therefore, a sequential approach to the development layout should avoid this area in favour of the Flood Zone 1 area (low risk).
3.3 Surface water shall be managed in accordance with the Leeds City Council "Minimum Development Control Standards for Flood Risk".
6 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 4.0 YORKSHIRE WATER CONSULTATION
4.1 A consultation was requested from Yorkshire Water, and a copy of their response, reference P014711, dated 22 nd October 2013, is presented in Appendix C for reference purposes.
4.2 Yorkshire Water confirms that there is a 152mm diameter foul and a 450mm combined public sewer crossing the site. No buildings are to be erected within 3m, and no trees planted within 5m of the public sewers. Any diversion would need to be under Section 185 of the Water Industry Act 1991, subject to an application in writing.
4.3 Foul water can discharge to the 450mm diameter public combined sewer crossing the site.
4.4 In respect of surface water, Yorkshire Water refer to Sustainable Drainage Systems and Requirement H3 of Building Regulations 2000.
4.5 The local public sewers do not have capacity to accept any surface water discharge from the development, and Yorkshire Water advise contact with the Environment Agency/Land Drainage Authority with a view to establishing a suitable watercourse for discharge.
7 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 5.0 EXISTING AND PROPOSED SURFACE WATER RUN-OFF
5.1 A consultation was requested from Leeds City Council, as Land Drainage Authority, and a copy of their e-mail response, dated the 7 th October 2013, is presented in Appendix D for reference purposes.
5.2 The site is bounded by Pudsey Beck and the 1 in 100 year flood plain extends into the southerly section of the site. If development is to be located within Flood Zone 3, then some flood compensation may be required, depending upon the type of development and its impact on the extent of the flood plain.
5.3 There are no records of flooding on the site or the surrounding areas. However, flooding of Pudsey Beck in the vicinity of Union Bridge Mills, downstream has occurred due to the blockage of the watercourse from fallen trees and debris.
5.4 There are other open watercourses to the northern and northwestern boundary of the site, but Leeds City Council has no records of connectivity to Pudsey Beck.
5.5 The drainage of the site should be in accordance with Leeds City Council "Minimum Development Control Standards for Flood Risk", which show that existing/proven surface water outfalls to Pudsey Beck would continue to discharge to the watercourse, but at reduced rates. If there is no connection to the watercourse at the present time, then greenfield rates of discharge may be necessary to allow connection to the watercourse.
8 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 6.0 MATERIAL CONSIDERATION IN RESPECT OF NPPF AND TG
Flood Classification
6.1 The Environment Agency and the Land Drainage Authority consultations show that the majority of site falls within land assessed as having less than a 1 in 1000 annual probability of river or sea flooding in any year (less than 0.1%). It will be necessary, however, to exclude development from the most southerly area of the site adjacent to Pudsey Beck where flooding occurs and, subject to compliance with this requirement, Table 1 of the TG shows that the site falls within Flood Zone 1 "low probability".
6.2 Therefore, all uses of land are appropriate within this Zone, but an assessment of the effect of surface water run-off will need to be incorporated in any Flood Risk Assessment.
End Use
6.3 The development proposal is for new residential dwellings and a proposed layout is presented in Appendix E for reference purposes.
6.4 When applying Table 2 of the TG, the flood risk vulnerability classification shows that the proposed end use will fall into a "more vulnerable" classification.
Sequential Test
6.5 As set out in the NPPF, the aim of the Sequential Test is to steer new development to areas with the lowest probability of flooding (Zone 1).
6.6 When the site is evaluated in accordance with Table 3 of the TG, the development shows that the Sequential Test is satisfied.
9 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 Flood Sources
6.7 Flooding from Rivers - There are no rivers maintained by the Environment Agency within the vicinity of the site and, therefore, flooding from this source is considered to be low risk.
6.8 Flooding from Local Watercourses - The watercourse known as Pudsey Beck is located on the southern boundary and this is known to flood during times of high storm. It will be necessary to ensure that the proposed development does not encroach the flood plain, although there have been some buildings in this lower area in the past which are now derelict or partly demolished due to fire or other similar damage. Whilst the buildings fall within the flood plain, it would have been appropriate to be able to protect the building from water ingress and, this should not form part of the flood plain area. Therefore, the main development will be located within Flood Zone 1, but any development in this particular location, on the footprint of the original buildings, will be possible but will need to be raised about the indicative flood plain. However, as the existing sewer in this area will require an appropriate easement, development in this area is not possible and, therefore, this has been discounted. Therefore, the proposed development will all fall within Flood Zone 1.
6.9 Flooding from the Sea - The site is not located near enough to the sea to cause a problem of flooding from this source.
6.10 Flooding from Land - The eastern and western boundaries have levels concordant with the site and, therefore, no overland water will enter the site from this location. However, the northern boundary has land significantly higher than the site levels. It is anticipated that, during times of storm, water will enter the site from this location and it be necessary to provide cut-off drains or ensure that water from the highway is connected into the positive drainage system and designed as part of the scheme. The water will be diverted to the existing Pudsey Beck watercourse to the south.
6.11 Flooding from Groundwater -Whilst no intrusive investigation of the ground conditions has been undertaken, the Geological Survey of Great Britain shows that the site is located on undifferentiated siltstones, mudstones and sandstones of the Lower Coal Measures, with
10 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 weathering of the upper strata to a cohesive clay material. The surface strata of the site will be relatively impermeable to rainwater and therefore, it is unlikely that issues of groundwater will occur and flooding from this source is considered to be low risk.
6.12 Flooding from Sewer - There will be a new surface water drainage system for the development and there are existing sewers and watercourses in the vicinity. It is possible, therefore, that any blockage of sewers or the watercourse will result in flooding from the lowest cover level of manholes or gullies and this will need to be considered as part of any proposed development.
6.13 Flooding from Reservoirs, Canals or Artificial Sources - There are no other reservoirs, canals or artificial sources which will result in flooding on the site.
Climate Change
6.14 The NPPF and TG has indicated that the Global sea level will continue to rise, depending on greenhouse gas emissions, and the sensitivity of the climate system and there will be an increase in rainfall across the country. Table 5 of the TG makes an assessment of the increase in peak rainfall intensity and that this is likely to increase by 20% between 2055 and 2085 and by 30% between 2085 to 2115.
6.15 The site is known to be below the level of the northern boundary and water, particularly from the highway, is likely to enter the site. Therefore, the assessment of climate change will need to consider rainfall not only falling within the site boundaries, but also run-off from the north.
6.16 In accordance with the TG, the published figures show that, for an expected life of greater than 2085 for any new development, the anticipated increase in rainfall will be around 30%. It will be necessary to design any new positive drainage system with a 30% increase in capacity to accommodate this requirement.
11 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 Flood Mitigation
6.17 As the site falls within Flood Zone 1, the Sequential Test is satisfied and flood mitigation measures are only required in the event of a catastrophic storm or blockage of the existing or proposed sewers or watercourse. The following precautionary mitigation measures are recommended:-
6.17.1 The finished floor levels to the property shall be raised above external levels by a minimum of 150mm and preferably 300mm where possible in Flood Zone 1.
6.17.2 The proposed dwellings shall be designed without any basements and shall comprise solid concrete ground floors or beam and block and screed construction.
6.17.3 Incoming electricity supplies shall be raised above ground floor level and ground floor electric sockets shall be served by loops from upper level.
6.17.4 The proposed drainage system will need to be designed to accommodate water flowing into the site from the northern boundary, particularly from the access road.
6.17.5 In the unlikely event of flooding on the site, external levels shall be designed with falls to non-critical areas, such as landscape or through to the southern boundary where the water can pond or run-off naturally into the watercourse to avoid flooding of buildings.
Sustainable Drainage
6.18 In order to comply with the requirements of NPPF, it will be necessary to consider aspects of Sustainable Drainage techniques for the new development.
6.19 No intrusive investigation of the ground conditions has been undertaken, but the Geological Survey of Great Britain shows that the site is located on undifferentiated siltstones, mudstones and sandstones of the Lower Coal Measures with weathering of the upper strata to a cohesive clay material.
12 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 These materials are likely to have very low infiltration rates, if any at all, and, therefore, it is assumed that the soils will be unsuitable for soakaways or other similar infiltration systems on the site. The presence of the Pudsey Beck watercourse on the southern boundary confirms this assessment. For the purposes of this report, it is assumed that a full positive drainage system will be required with discharge to the existing Pudsey Beck watercourse to the south.
Drainage
6.20 It is a requirement to ensure that surface water run-off from any proposed development has negligible consequence on downstream areas either in sewer capacity or discharge to watercourse.
Existing Surface Water Run-off
6.21 The site walkover shows that there is a positive drainage system for the existing buildings on the site and indicative calculations presented in Appendix F show that the existing impermeable area equates to around 7,850m², including Hare Lane. Assuming that the storm intensity of 50mm per hour for a 1 in 1 year storm, the calculations show that the existing discharge rate is 109l/s.
Proposed Surface Water Drainage
6.22 From the proposed layout in Appendix E, the proposed impermeable area, making an allowance for run-off from Hare Lane, is in the order of 0.45ha. Using a proposed discharge of 76l/s, which is based on a 30% reduction of the existing rate of 109l/s, the attenuation for a 1 in 30 year storm, using WinDES Source Control Computer Program, requires on-site storage of 20.2m³. This can be achieved by several methods, including oversize pipes, underground tanks, balance ponds or a combination or some of all of these. However, the discharge is directly into watercourse and it will be necessary, in these circumstances, to ensure that the 1 in 100 year storm plus 30% allowance for climate change can be accommodated within the drainage system. In these circumstances, the
13 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 indicative calculations show that the attenuation will be 59.7m³ and one such option will be to provide 53m of 1.2m diameter oversized pipe located towards the bottom of the site. It will be necessary to ensure that a gravity discharge can be achieved from the attenuation into the watercourse to prevent the use of a surface water pump. This option will need to be assessed in relation to the proposed layout before considering an option of this type in comparison to other attenuation proposals. The indicative surface water calculations are presented in Appendix F, but detailed calculations and proposals will be prepared and submitted to the Planning Authority for approval prior to construction on site.
Foul Drainage
6.23 Foul drainage can discharge to the 450mm public combined sewer crossing the southern part of the site. Gravity discharge to this location should be satisfactory.
Emergency Egress During Times of Flood
6.24 It is a requirement under the TG that occupants should be able to egress any building during times of flood, without being trapped by flood conditions.
6.25 As the proposed development falls within Flood Zone 1, no special mitigation measures are required for emergency egress at times of flood at this location.
14 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 7.0 COMMENT
7.1 The development site will fall within Flood Zone 1 and a Sequential Test is satisfied. However, in order to accommodate the possibilities of flood from extreme storm or blocked sewers and watercourses, the following mitigation measures are recommended.
7.1.1 The ground floor to the proposed dwellings shall be set above external levels by a minimum of 150mm and preferably 300mm if possible.
7.1.2 The new dwellings shall be designed without any basements and ground floors shall comprise solid concrete slabs or beam and block with screed construction.
7.1.3 Incoming electricity supplies shall be raised above ground floor level and ground floor electric sockets shall be served by loops from first floor level.
7.1.4 Overland flood from the northern boundary shall be either accommodated by a cut off drain which will direct water to Pudsey Beck or water off Hare Lane to the north will need to be accommodated within the drainage system across the site.
7.1.5 The external alignment of road and hard paved areas shall be designed to direct any flood water to non-sensitive areas, such as landscaping, or across the site to the watercourse on the southern boundary.
7.2 A 30% increase in rainfall shall be accommodated into any new positive drainage system to satisfy the requirements of climate change for developments extending beyond 2085.
7.3 Sustainable drainage systems of infiltration techniques are considered to be unsuitable on this particular site.
7.4 Surface water discharge shall be to the Pudsey Beck watercourse with outfall restricted to the rate of the existing run-off less 30% to meet the requirements of the Pitt Review.
15 ARP ASSOCIATES – 724/01r2 OCTOBER 2013 7.5 The proposed surface water drainage system shall be designed for allowance for climate change and restricted to the agreed discharge rate with appropriate attenuation incorporated into the design to accommodate a 1 in 100 year storm for outfall into watercourse. The design, details and calculations shall be submitted to the Planning Authority for approval prior to construction on site.
7.6 In respect of foul drainage, outfall to the existing 450mm diameter combined sewer crossing the southern part of the site is satisfactory.
7.7 No special mitigation measures are required for emergency egress during times of flood where the development is located within Flood Zone 1.
7.8 Subject to compliance with the above, the proposed development can satisfy the requirement of the National Planning Policy Framework and the accompanying Technical Guidance in relation to flood risk.
16 ARP ASSOCIATES – 724/01r2 OCTOBER 2013
A P P E N D I X A
SITE LOCATION PLAN
A P P E N D I X B
ENVIRONMENT AGENCY CONSULTATION
Allan Poyser
From: Beech, Cheryl
Our Ref: RFI/2013/27259
Your Ref:
Dear Allan
Provision of Product 3 for South Park Mills, Hare Lane, Pudsey
Thank you for your request of 2 October 2013 to use Environment Agency data, Product 3, in the development of the above site. The information is attached.
If you have requested this information to help inform a development proposal, then you should note the detail in the attached advisory text on the use of Environment Agency Information for Flood Risk Assessments.
Supporting Information
The area immediately adjacent to Pudsey Beck is classified as flood zone 3 (high risk) on the EA flood map. A sequential approach to the development layout should avoid this area in favour of the flood zone 1 area (low risk).
Surface water must be managed in accordance with the LCC ‘Minimum development control standards for flood risk’ document a copy of which is attached for you.
This information is provided subject to the attached notice which we advise that you should read.
We would be really grateful if you could spare five minutes to help us improve our service. Please click on the link below and fill in our survey – we use every piece of feedback we receive: http://www.surveyshack.com/link/a3d10
If you require any further help, please do not hesitate to contact me.
Yours sincerely
Cheryl Beech Customers and Engagement Team Direct Dial 0113 8196360 Email [email protected]
Please note: I only work part time - my usual working days are Tuesday, Wednesday & Thursday
1
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2 Flood Map Centred on SE 22620 31616 - Created on 8/10/13 - Enquiry 27259
Scale 1:10,001
Legend
Flood Map Areas (assuming no defences) Flood Zone 3 shows the area that could be affected by flooding: - from the sea with a 1 in 200 or greater chance of happening each year - or from a river with a 1 in 100 or greater chance of happening each year. Flood Zone 2 shows the extent of an extreme flood from rivers or the sea with up to a 1 in 1000 chance of occurring each year.
© Environment Agency copyright and / or database rights 2013. All rights reserved. © Crown Copyright and database right 2013. Ordnance Survey licence number 100024198.
Contact Us: National Customer Contact Centre, PO Box 544, Rotherham, S60 1BY. Tel: 03708 506 506 (Mon-Fri 8-6). Email: [email protected] MINIMUM DEVELOPMENT CONTROL STANDARDS FOR FLOOD RISK Basic Information to be submitted NOTES Indicative Drainage Strategy required for all sites Soakaways
Flood Risk Assessment (incorporating off-site impact) required for all sites – proportionate to the risk and appropriate BRE365 standard of 1 in 10 years is to the scale, nature and location – taking account of flooding from any source not acceptable (C609, p80).
On-site Standard Climate Change Developers should assume an Demonstrate compliance with Building Regs H3 – i.e. check infiltration feasibility, give preference to soakaways increase in rainfall depth and peak river flows in line with PPS25 Table B2, taking account of the Basically Sewers for Adoption standard development lifetime (e.g. 100 years for residential – PG 3.102). • 1 in 2 year pipe full (with exceptions) Green field run-off •1 in 30 year no site flooding (PPS25 PG, 5.51) For sites < 1ha a maximum No property flooding for 1 in 100 yr (+ CC) (PPS25, PG 5.51) discharge rate of 5 l/s can be used for all storms up to 1 in 100 years For SUDS the same standard (CIRIA C609, p80) +CC.
For larger sites the table of methods Freeboard above 1 in 100 years fluvial flood level should be: 600mm for dwellings, 400mm for office & commercial, in ICOP can be used 300mm for industrial and warehousing, 300mm for entrance to u/ground car parks. These figures can be halved Brown field run-off where CC is taken into account (Leeds SFRA, para.223) Existing peak discharge can be Off-site Impact taken as 140 l/s/ha of connected roofs and paving, in lieu of detailed calculations Flows beyond 1 in 30, but up to 1 in 100 years (+CC), should be stored on site (e.g. in car parks, hollows, etc) unless Flow Control Orifices run-off from site has no unreasonable adverse impacts compared with the existing situation) (PPS25, PG 5.54) Generally must not be less than 75 No Soakaways where history of groundwater flooding or where flows could re-emerge to flood lower level property mm in diameter (C609, p75) Point of Connection
To a watercourse or sewer must be Green field Brown field such that it will not create additional flooding due to increased flow rates (allowable discharges) (allowable discharges) or volumes
Reduce run-off rates as much as is reasonably practicable (PPS25, PG 5.50) Water Quality
To watercourse or to sewer New connection to watercourse or sewer Car park petrol interceptors to be agreed with the EA
• Green field rates up to 1 in 100 years (+CC) • As green field Adoption/Maintenance
• Volume control as per ICOP, p48 Existing connection to watercourse or sewer Clear-cut provisions for future maintenance. Major features (e.g. • Additional downstream works may be required • A minimum 30% reduction to existing peak flow rates balancing tanks and ponds) to be Version 5: 11 Jan 2010 – amended for Dec 2009 Practice Guide up to 1 in 100 year storm (+CC) maintained by a corporate body
SURFACE WATER MANAGEMENT – CALCULATION & DRAWING REQUIREMENTS
Purpose: To assist developers in demonstrating that they are complying with latest guidance on managing surface water run-off the following calculations and drawings shall be submitted:
1) General Drainage Information
A summary sheet (1 page max) showing the global variables which have been used in the design of the surface water sewerage system.
For Leeds, the following values are typical: M5_60 = 19.0mm, Ratio_R = 0.348, Cv (Summer) = 0.750, Cv (Winter) = 0.840.
Note: The values of Cv may be increased by 20% to model the effects of climate change, if there is no other provision in the developer's software.
Pipe roughness: As per Sewers for Adoption guideline values.
The Following Key Data must be provided: (a) The total impermeable area of the whole development (b) The existing impermeable area and the allowable peak discharge from the site. (Refer to Guidance Note) (c) The total volume of attenuation storage which will be provided both above and below ground.
Provide a drawing showing a schematic of the drainage layout, with all pipes, manholes, ponds, etc clearly numbered or referenced to the model output.
On-Site Standards
2) No Surcharge up to 1 in 2 year return period Provide a summary sheet demonstrating compliance
3) No Flooding up to 1 in 30 year return period Provide a summary sheet demonstrating compliance
Off-Site Standards
4) Maximum Discharge Provide results of peak flow from the downstream pipe, which must be ≤ allowable discharge
5) No Additional Run-off from site up to 1 in 100 years + Climate Change Provide results showing the peak water level in any pond, or tank (and hence volume) Provide a drawing showing the size and location of all the attenuation storage provided. Where attenuation storage is located above ground, provide details of finished ground levels and demonstrate flood pathways to the storage areas.
Note: We do not need to see reams of hydraulic calculations. We do not have the means to check these in detail anyway, but we do require the developer to demonstrate compliance with the Leeds City Council’s Minimum Development Control Standards for Flood Risk, which is based on the provisions of PPS25.
In case of general technical queries about these requirements (not individual Applications) Please contact Stuart Pedder, tel 0113 247 8779 Version 3.0 May 2007
A P P E N D I X C
WATER AUTHORITY CONSULTATION
A P P E N D I X D
LAND DRAINAGE AUTHORITY CONSULTATION
Allan Poyser
From: Lezama, Magda
Allan
Re: Requirements for FRA for Park Mills site
The site is bounded by Pudsey Beck and the 1:100 yr flood plain extends into the most southerly section of the site. Development within this flood Zone 3 area may require some flood compensation depending on the type of development and its impact on the extent of the flood plain.
There are no records of flooding of the site or its surrounds however downstream of Pudsey Beck, in the vicinity of Union Bridge Mills, my records indicate reports of flooding problems mainly due to blockage of the watercourse from fallen trees and debris.
An open watercourse runs within the northern and north western boundary of the site however I cannot determine the connectivity of this watercourse to Pudsey Beck. If surface water from the site is to be discharged to this watercourse then its outfall to Pudsey Beck must be verified and detailed on plan.
The drainage of the site should be in accordance with our Minimum development control standards for flood risk so that existing/ proven surface water outfall(s) to Pudsey Beck would be allowed to continue to discharge surface water to the watercourse but at reduces rates as required. However if there are no surface water outfalls to Pudsey Beck at present then greenfield rates of discharge will be allowed to the watercourse and any new outfall connection(s) will have to be approved by the council in accordance with Schedule 2 of the Flood & Water Management Act 2010.
The above should adequately address the drainage and flood risk matters relating to this site but please contact me if you wish to discuss the matter further.
Magda ------Magda Lezama Senior Engineer Flood Risk Management Leeds City Council Phone: 0113 247 8784 Fax: 0113 395 2407 www.Leeds.gov.uk
From: Allan Poyser [ mailto:[email protected] ] Sent: 01 October 2013 16:05 To: Lezama, Magda Cc: [email protected] ; Wayne Walker Subject: South Park Mills, Pudsey
Magda
Please see attached pre-planning enquiry for your attention.
1 Regards
Allan
ARP ASSOCIATES & ARP GEOTECHNICAL LTD
www.arpassociates.co.uk
Tel: 0113 245 8498 Fax: 0113 244 3864
5/6 Northwest Business Park, Servia Hill, Leeds LS6 2QH Pre-planning Geotechnical Civil Engineering Structural Engineering
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2 Open watercourse with unidentified outlet to Pudset Beck.
Aire - Hol Beck Catchment
5656
~ Reproduced from Ordnance Survey material with the permission of Ordnance Survey on behalf of the Controller Drainage records shown on this plan (including locations, sizes and depths) are given in good faith, but must not of Her Majesty's Stationery Office. Crown Copyright. Unauthorised reproduction infringes Crown copyright and be relied upon for any purpose without verification on site. Please note that any sewerage information incidentally may lead to prosecution or civil proceedings. Licence No: LA 100019567 (2012). shown on this plan could well be out of date. Copies of the current statutory sewer map must be obtained from ~ © The Canal & River Trust copyright and database rights reserved 2012 Yorkshire Water.
A P P E N D I X E
PROPOSED DEVELOPMENT LAYOUT
MAP
Architecture and Project Management
A P P E N D I X F
INDICATIVE SURFACE WATER DRAINAGE CALCULATIONS
ARP Associates Page 1 Northwest House Acrivan Servia Hill South Park Mills, Pudsey Leeds LS6 2QH 724/01PrelimStore30yr... Date 04-11-13 Designed by ARP File 724-01Preliminar... Checked by Elstree Computing Ltd Source Control 2013.1.1
Summary of Results for 30 year Return Period
Storm Max Max Max Max Max Max Status Event Level Depth Control Overflow Σ Outflow Volume (m) (m) (l/s) (l/s) (l/s) (m³)
15 min Summer 100.948 0.948 90.4 0.0 90.4 17.9 O K 30 min Summer 100.810 0.810 90.4 0.0 90.4 15.1 O K 60 min Summer 100.514 0.514 86.4 0.0 86.4 8.5 O K 120 min Summer 100.368 0.368 61.9 0.0 61.9 5.3 O K 180 min Summer 100.311 0.311 48.1 0.0 48.1 4.1 O K 240 min Summer 100.276 0.276 39.4 0.0 39.4 3.5 O K 360 min Summer 100.236 0.236 29.7 0.0 29.7 2.8 O K 480 min Summer 100.212 0.212 24.1 0.0 24.1 2.3 O K 600 min Summer 100.195 0.195 20.4 0.0 20.4 2.1 O K 720 min Summer 100.182 0.182 17.8 0.0 17.8 1.9 O K 960 min Summer 100.164 0.164 14.4 0.0 14.4 1.6 O K 1440 min Summer 100.142 0.142 10.6 0.0 10.6 1.3 O K 2160 min Summer 100.123 0.123 7.8 0.0 7.8 1.0 O K 2880 min Summer 100.112 0.112 6.2 0.0 6.2 0.9 O K 4320 min Summer 100.097 0.097 4.6 0.0 4.6 0.7 O K 5760 min Summer 100.089 0.089 3.7 0.0 3.7 0.6 O K 7200 min Summer 100.082 0.082 3.1 0.0 3.1 0.5 O K 8640 min Summer 100.077 0.077 2.7 0.0 2.7 0.5 O K 10080 min Summer 100.074 0.074 2.4 0.0 2.4 0.4 O K 15 min Winter 101.082 1.082 90.4 0.0 90.4 20.2 O K 30 min Winter 100.704 0.704 90.3 0.0 90.3 12.7 O K 60 min Winter 100.425 0.425 74.0 0.0 74.0 6.5 O K 120 min Winter 100.309 0.309 47.6 0.0 47.6 4.1 O K Storm Rain Flooded Discharge Overflow Time-Peak Event (mm/hr) Volume Volume Volume (mins) (m³) (m³) (m³)
15 min Summer 68.836 0.0 58.1 0.0 16 30 min Summer 45.828 0.0 77.3 0.0 24 60 min Summer 29.238 0.0 98.7 0.0 38 120 min Summer 18.112 0.0 122.3 0.0 68 180 min Summer 13.534 0.0 137.0 0.0 98 240 min Summer 10.952 0.0 147.8 0.0 128 360 min Summer 8.106 0.0 164.1 0.0 188 480 min Summer 6.544 0.0 176.7 0.0 248 600 min Summer 5.539 0.0 186.9 0.0 308 720 min Summer 4.832 0.0 195.7 0.0 370 960 min Summer 3.892 0.0 210.2 0.0 492 1440 min Summer 2.866 0.0 232.2 0.0 730 2160 min Summer 2.108 0.0 256.1 0.0 1104 2880 min Summer 1.693 0.0 274.3 0.0 1424 4320 min Summer 1.242 0.0 301.8 0.0 2148 5760 min Summer 0.996 0.0 322.7 0.0 2928 7200 min Summer 0.839 0.0 339.8 0.0 3584 8640 min Summer 0.730 0.0 354.6 0.0 4296 10080 min Summer 0.648 0.0 367.6 0.0 5024 15 min Winter 68.836 0.0 65.1 0.0 17 30 min Winter 45.828 0.0 86.6 0.0 24 60 min Winter 29.238 0.0 110.5 0.0 38 120 min Winter 18.112 0.0 136.9 0.0 68 ©1982-2013 Micro Drainage Ltd ARP Associates Page 2 Northwest House Acrivan Servia Hill South Park Mills, Pudsey Leeds LS6 2QH 724/01PrelimStore30yr... Date 04-11-13 Designed by ARP File 724-01Preliminar... Checked by Elstree Computing Ltd Source Control 2013.1.1
Summary of Results for 30 year Return Period
Storm Max Max Max Max Max Max Status Event Level Depth Control Overflow Σ Outflow Volume (m) (m) (l/s) (l/s) (l/s) (m³)
180 min Winter 100.261 0.261 35.7 0.0 35.7 3.2 O K 240 min Winter 100.233 0.233 29.0 0.0 29.0 2.7 O K 360 min Winter 100.200 0.200 21.6 0.0 21.6 2.1 O K 480 min Winter 100.180 0.180 17.4 0.0 17.4 1.8 O K 600 min Winter 100.166 0.166 14.7 0.0 14.7 1.6 O K 720 min Winter 100.156 0.156 12.9 0.0 12.9 1.5 O K 960 min Winter 100.141 0.141 10.4 0.0 10.4 1.2 O K 1440 min Winter 100.122 0.122 7.6 0.0 7.6 1.0 O K 2160 min Winter 100.107 0.107 5.6 0.0 5.6 0.8 O K 2880 min Winter 100.097 0.097 4.5 0.0 4.5 0.7 O K 4320 min Winter 100.085 0.085 3.3 0.0 3.3 0.5 O K 5760 min Winter 100.077 0.077 2.7 0.0 2.7 0.5 O K 7200 min Winter 100.071 0.071 2.2 0.0 2.2 0.4 O K 8640 min Winter 100.067 0.067 2.0 0.0 2.0 0.4 O K 10080 min Winter 100.064 0.064 1.8 0.0 1.8 0.3 O K Storm Rain Flooded Discharge Overflow Time-Peak Event (mm/hr) Volume Volume Volume (mins) (m³) (m³) (m³)
180 min Winter 13.534 0.0 153.5 0.0 98 240 min Winter 10.952 0.0 165.6 0.0 128 360 min Winter 8.106 0.0 183.8 0.0 188 480 min Winter 6.544 0.0 197.9 0.0 248 600 min Winter 5.539 0.0 209.4 0.0 310 720 min Winter 4.832 0.0 219.2 0.0 364 960 min Winter 3.892 0.0 235.4 0.0 492 1440 min Winter 2.866 0.0 260.0 0.0 716 2160 min Winter 2.108 0.0 286.8 0.0 1080 2880 min Winter 1.693 0.0 307.2 0.0 1452 4320 min Winter 1.242 0.0 338.0 0.0 2148 5760 min Winter 0.996 0.0 361.4 0.0 2888 7200 min Winter 0.839 0.0 380.6 0.0 3544 8640 min Winter 0.730 0.0 397.1 0.0 4248 10080 min Winter 0.648 0.0 411.8 0.0 4976
©1982-2013 Micro Drainage Ltd ARP Associates Page 3 Northwest House Acrivan Servia Hill South Park Mills, Pudsey Leeds LS6 2QH 724/01PrelimStore30yr... Date 04-11-13 Designed by ARP File 724-01Preliminar... Checked by Elstree Computing Ltd Source Control 2013.1.1
Rainfall Details
Rainfall Model FSR Winter Storms Yes Return Period (years) 30 Cv (Summer) 0.750 Region England and Wales Cv (Winter) 0.840 M5-60 (mm) 19.000 Shortest Storm (mins) 15 Ratio R 0.350 Longest Storm (mins) 10080 Summer Storms Yes Climate Change % +0
Time Area Diagram
Total Area (ha) 0.450
Time (mins) Area Time (mins) Area From: To: (ha) From: To: (ha)
0 4 0.000 4 8 0.450
©1982-2013 Micro Drainage Ltd ARP Associates Page 4 Northwest House Acrivan Servia Hill South Park Mills, Pudsey Leeds LS6 2QH 724/01PrelimStore30yr... Date 04-11-13 Designed by ARP File 724-01Preliminar... Checked by Elstree Computing Ltd Source Control 2013.1.1
Model Details
Storage is Online Cover Level (m) 101.500
Pipe Structure
Diameter (m) 1.200 Length (m) 18.000 Slope (1:X) 500.000 Invert Level (m) 100.000
Hydro-Brake® Outflow Control
Design Head (m) 1.236 Hydro-Brake® Type Md4 Invert Level (m) 100.000 Design Flow (l/s) 76.0 Diameter (mm) 290
Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s)
0.100 4.9 1.200 75.2 3.000 113.5 7.000 173.4 0.200 21.5 1.400 78.7 3.500 122.6 7.500 179.5 0.300 45.4 1.600 83.3 4.000 131.1 8.000 185.4 0.400 69.0 1.800 88.0 4.500 139.0 8.500 191.1 0.500 85.1 2.000 92.7 5.000 146.5 9.000 196.6 0.600 90.3 2.200 97.2 5.500 153.7 9.500 202.0 0.800 82.4 2.400 101.5 6.000 160.5 1.000 75.2 2.600 105.7 6.500 167.1
Weir Overflow Control
Discharge Coef 0.544 Width (m) 2.700 Invert Level (m) 101.236
©1982-2013 Micro Drainage Ltd ARP Associates Page 5 Northwest House Acrivan Servia Hill South Park Mills, Pudsey Leeds LS6 2QH 724/01PrelimStore100y... Date 04-11-13 Designed by ARP File 724-01Preliminar... Checked by Elstree Computing Ltd Source Control 2013.1.1
Summary of Results for 100 year Return Period (+30%)
Storm Max Max Max Max Max Max Status Event Level Depth Control Overflow Σ Outflow Volume (m) (m) (l/s) (l/s) (l/s) (m³)
15 min Summer 100.991 0.991 88.4 0.0 88.4 51.2 O K 30 min Summer 101.049 1.049 88.8 0.0 88.8 54.2 O K 60 min Summer 100.860 0.860 88.7 0.0 88.7 43.7 O K 120 min Summer 100.552 0.552 87.6 0.0 87.6 24.1 O K 180 min Summer 100.437 0.437 75.5 0.0 75.5 17.0 O K 240 min Summer 100.378 0.378 63.8 0.0 63.8 13.5 O K 360 min Summer 100.314 0.314 48.6 0.0 48.6 10.0 O K 480 min Summer 100.278 0.278 39.7 0.0 39.7 8.1 O K 600 min Summer 100.254 0.254 33.9 0.0 33.9 6.9 O K 720 min Summer 100.236 0.236 29.4 0.0 29.4 6.1 O K 960 min Summer 100.210 0.210 23.6 0.0 23.6 4.9 O K 1440 min Summer 100.180 0.180 17.4 0.0 17.4 3.6 O K 2160 min Summer 100.155 0.155 12.6 0.0 12.6 2.7 O K 2880 min Summer 100.139 0.139 10.1 0.0 10.1 2.1 O K 4320 min Summer 100.120 0.120 7.3 0.0 7.3 1.5 O K 5760 min Summer 100.109 0.109 5.9 0.0 5.9 1.2 O K 7200 min Summer 100.100 0.100 4.9 0.0 4.9 1.0 O K 8640 min Summer 100.094 0.094 4.2 0.0 4.2 0.9 O K 10080 min Summer 100.089 0.089 3.8 0.0 3.8 0.8 O K 15 min Winter 101.174 1.174 88.6 0.0 88.6 59.3 O K 30 min Winter 101.184 1.184 88.7 0.0 88.7 59.7 O K 60 min Winter 100.786 0.786 88.8 0.0 88.8 39.1 O K 120 min Winter 100.449 0.449 77.4 0.0 77.4 17.7 O K Storm Rain Flooded Discharge Overflow Time-Peak Event (mm/hr) Volume Volume Volume (mins) (m³) (m³) (m³)
15 min Summer 115.731 0.0 97.6 0.0 17 30 min Summer 77.804 0.0 131.3 0.0 26 60 min Summer 49.937 0.0 168.5 0.0 42 120 min Summer 30.956 0.0 209.0 0.0 70 180 min Summer 23.058 0.0 233.5 0.0 100 240 min Summer 18.577 0.0 250.8 0.0 128 360 min Summer 13.656 0.0 276.5 0.0 190 480 min Summer 10.974 0.0 296.3 0.0 250 600 min Summer 9.254 0.0 312.3 0.0 310 720 min Summer 8.046 0.0 325.9 0.0 370 960 min Summer 6.447 0.0 348.2 0.0 492 1440 min Summer 4.709 0.0 381.4 0.0 730 2160 min Summer 3.432 0.0 417.0 0.0 1084 2880 min Summer 2.739 0.0 443.7 0.0 1432 4320 min Summer 1.989 0.0 483.3 0.0 2180 5760 min Summer 1.583 0.0 512.8 0.0 2856 7200 min Summer 1.325 0.0 536.6 0.0 3544 8640 min Summer 1.147 0.0 557.4 0.0 4272 10080 min Summer 1.015 0.0 575.6 0.0 4960 15 min Winter 115.731 0.0 109.4 0.0 18 30 min Winter 77.804 0.0 147.0 0.0 27 60 min Winter 49.937 0.0 188.8 0.0 44 120 min Winter 30.956 0.0 234.0 0.0 70 ©1982-2013 Micro Drainage Ltd ARP Associates Page 6 Northwest House Acrivan Servia Hill South Park Mills, Pudsey Leeds LS6 2QH 724/01PrelimStore100y... Date 04-11-13 Designed by ARP File 724-01Preliminar... Checked by Elstree Computing Ltd Source Control 2013.1.1
Summary of Results for 100 year Return Period (+30%)
Storm Max Max Max Max Max Max Status Event Level Depth Control Overflow Σ Outflow Volume (m) (m) (l/s) (l/s) (l/s) (m³)
180 min Winter 100.361 0.361 59.8 0.0 59.8 12.6 O K 240 min Winter 100.315 0.315 48.8 0.0 48.8 10.0 O K 360 min Winter 100.264 0.264 36.2 0.0 36.2 7.4 O K 480 min Winter 100.234 0.234 29.1 0.0 29.1 6.0 O K 600 min Winter 100.214 0.214 24.5 0.0 24.5 5.1 O K 720 min Winter 100.200 0.200 21.4 0.0 21.4 4.4 O K 960 min Winter 100.179 0.179 17.2 0.0 17.2 3.6 O K 1440 min Winter 100.154 0.154 12.6 0.0 12.6 2.7 O K 2160 min Winter 100.133 0.133 9.2 0.0 9.2 1.9 O K 2880 min Winter 100.120 0.120 7.3 0.0 7.3 1.5 O K 4320 min Winter 100.104 0.104 5.3 0.0 5.3 1.1 O K 5760 min Winter 100.094 0.094 4.2 0.0 4.2 0.9 O K 7200 min Winter 100.087 0.087 3.5 0.0 3.5 0.7 O K 8640 min Winter 100.082 0.082 3.1 0.0 3.1 0.6 O K 10080 min Winter 100.077 0.077 2.7 0.0 2.7 0.6 O K Storm Rain Flooded Discharge Overflow Time-Peak Event (mm/hr) Volume Volume Volume (mins) (m³) (m³) (m³)
180 min Winter 23.058 0.0 261.5 0.0 100 240 min Winter 18.577 0.0 280.9 0.0 130 360 min Winter 13.656 0.0 309.7 0.0 188 480 min Winter 10.974 0.0 331.8 0.0 248 600 min Winter 9.254 0.0 349.8 0.0 310 720 min Winter 8.046 0.0 365.0 0.0 366 960 min Winter 6.447 0.0 389.9 0.0 494 1440 min Winter 4.709 0.0 427.2 0.0 740 2160 min Winter 3.432 0.0 467.0 0.0 1104 2880 min Winter 2.739 0.0 496.9 0.0 1448 4320 min Winter 1.989 0.0 541.2 0.0 2188 5760 min Winter 1.583 0.0 574.4 0.0 2896 7200 min Winter 1.325 0.0 601.0 0.0 3672 8640 min Winter 1.147 0.0 624.2 0.0 4272 10080 min Winter 1.015 0.0 644.7 0.0 5136
©1982-2013 Micro Drainage Ltd ARP Associates Page 7 Northwest House Acrivan Servia Hill South Park Mills, Pudsey Leeds LS6 2QH 724/01PrelimStore100y... Date 04-11-13 Designed by ARP File 724-01Preliminar... Checked by Elstree Computing Ltd Source Control 2013.1.1
Rainfall Details
Rainfall Model FSR Winter Storms Yes Return Period (years) 100 Cv (Summer) 0.750 Region England and Wales Cv (Winter) 0.840 M5-60 (mm) 19.000 Shortest Storm (mins) 15 Ratio R 0.350 Longest Storm (mins) 10080 Summer Storms Yes Climate Change % +30
Time Area Diagram
Total Area (ha) 0.450
Time (mins) Area Time (mins) Area From: To: (ha) From: To: (ha)
0 4 0.000 4 8 0.450
©1982-2013 Micro Drainage Ltd ARP Associates Page 8 Northwest House Acrivan Servia Hill South Park Mills, Pudsey Leeds LS6 2QH 724/01PrelimStore100y... Date 04-11-13 Designed by ARP File 724-01Preliminar... Checked by Elstree Computing Ltd Source Control 2013.1.1
Model Details
Storage is Online Cover Level (m) 101.500
Pipe Structure
Diameter (m) 1.200 Length (m) 53.000 Slope (1:X) 500.000 Invert Level (m) 100.000
Hydro-Brake® Outflow Control
Design Head (m) 1.306 Hydro-Brake® Type Md4 Invert Level (m) 100.000 Design Flow (l/s) 76.0 Diameter (mm) 288
Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s)
0.100 4.9 1.200 74.0 3.000 112.0 7.000 171.0 0.200 21.4 1.400 77.5 3.500 120.9 7.500 177.0 0.300 45.1 1.600 82.1 4.000 129.3 8.000 182.8 0.400 68.4 1.800 86.8 4.500 137.1 8.500 188.4 0.500 84.0 2.000 91.4 5.000 144.5 9.000 193.9 0.600 88.8 2.200 95.9 5.500 151.6 9.500 199.2 0.800 80.7 2.400 100.1 6.000 158.3 1.000 73.8 2.600 104.2 6.500 164.8
Weir Overflow Control
Discharge Coef 0.544 Width (m) 2.700 Invert Level (m) 101.306
©1982-2013 Micro Drainage Ltd