DRAINAGE STRATEGY
Project Ref: Goodshaw Baptist Church, Chapel Street. Crawshawbooth
Date: January 21
Project: Goodshaw Baptist Church, Chapel Street, Crawshawbooth Reference: Drainage Strategy Job No.: 4533 Revision: B Designer PC Checker AS Date 18/01/2021
Contents Site Details 3 Project Overview 3 Consideration of SUDS hierarchy 3 Infiltration 4 Surface Water Body 5 Surface Water Sewer 6
Figures & Photos Figure 1 – Distance to Surface Water Body – satellite view 5 Figure 2 – Distance to Surface Water Body – Google maps view 5 Figure 3 – Extract of Public Sewer Map 7
Photo 1 – Trial hole showing cohesive ground 4 Photo 2 – Location of surface water manhole in Chapel Street 6
List of Appendices Appendix A - Edge Structural Design preliminary drainage drawing 4533-01-P2 Appendix B - Former Rossendale Engineers Department drainage plan Appendix C - Architects Existing Site Layout / Location Plan Appendix D - Architects Proposed Site Layout drawing Appendix E - United Utilities pre-application response email dated 17/12/2020
REVISION HISTORY
REVISION STATUS
ISSUE DATE STATUS PREPARED BY SIGNATURE CHECKED BY SIGNATURE
Adam Sedgwick First Penny Clark - 07/12/2020 BSc(Hons) CEng Issue BSc (Hons) MIStructE Adam Sedgwick Second Penny Clark A 08/01/2021 BSc(Hons) CEng Issue BSc (Hons) MIStructE Adam Sedgwick Third Penny Clark B 18/01/2021 BSc(Hons) CEng Issue BSc (Hons) MIStructE
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Project: Goodshaw Baptist Church, Chapel Street, Crawshawbooth Reference: Drainage Strategy Job No.: 4533 Revision: B Designer PC Checker AS Date 18/01/2021
Site Details
Site Name: Goodshaw Baptist Church, Chapel Street, Crawshawbooth, BB4 8BS
Purpose of Development: Single-storey front extension to the church, along with the creation of additional car parking adjacent to Chapel Street
Site Area: 0.16 Hectares
Existing Land Use: The site is currently an existing church building with small car parking and soft landscaped areas
Grid Reference: E381118, N425927
Country England
County: Lancashire
Local Planning Authority: Rossendale Borough Council
Planning Reference: 2020/0272
Lead Local Flood Authority (LLFA): Lancashire County Council
Flood Zone: Flood Zone 1
Critical Drainage Area (CDA) Not Applicable
Internal Drainage Board: Not Applicable
Other Authority (e.g. British Waterways / Not Applicable Harbour Authority)
Project Overview Edge Structural Design has been asked to provide a drainage strategy for the proposed extension and additional car parking at Goodshaw Baptist Church, Chapel Street, Crawshawbooth.
As with all new developments, an assessment shall be carried out of the potential for disposing of surface water utilising a sustainable drainage system in accordance with the principles set out in Section 10 of the National Planning Policy Framework and the accompanying Technical Guidance (or any subsequent version or replacement guidance).
Consideration of SUDSUDSSSS hierarchy Paragraph 080 of the NPPG: Flood Risk and Coastal Change sets out the following hierarchy of drainage options: • into the ground (infiltration); • to a surface water body; • to a surface water sewer, • highway drain or another drainage system; • to a combined sewer.
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Project: Goodshaw Baptist Church, Chapel Street, Crawshawbooth Reference: Drainage Strategy Job No.: 4533 Revision: B Designer PC Checker AS Date 18/01/2021
Infiltration We have assessed the SUDS hierarchy, in which the preferred option is to drain any rainwater to an adequate soakaway or other infiltration system. If this is not possible, the next favoured option is to discharge to a watercourse. Only if neither of these options is possible should the site discharge rainwater to a sewer.
Various trial holes were dug on site and clay was found from 300mm below ground level. The existing surface water drainage for the church and car park is also currently connected into an existing piped drainage system.
None of the trial holes indicated granular material on site, therefore the ground is not deemed suitable for the use of infiltration or soakaways.
Photo 1 – Trial hole showing cohesive ground
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Project: Goodshaw Baptist Church, Chapel Street, Crawshawbooth Reference: Drainage Strategy Job No.: 4533 Revision: B Designer PC Checker AS Date 18/01/2021
Surface Water Body Having assessed the locality of the site, it is evident that there are no surface water bodies within a practicable distance of the site – the nearest is over 130m away and across 3 rd party land – see Figures 1 & 2. The area of the existing site that is proposed for the new drainage system is an extension which measures 73m 2 and is being constructed in an area that is already hardstarding, and a new small car park which measures 370 m2. The existing church and car park are positively drained and connect into the local sewer system, therefore it would be economically unviable to construct over 100m of new pipework and obtain the legal permissions to excavate across 3 rd party land, for a new catchment area of less than 450 m2. Therefore, disposal to a surface water body is not deemed to be a feasible solution for this site.
Figure 1 – Distance to Surface Water Body – satellite view
Figure 2 – Distance to Surface Water Body – Google maps view
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Project: Goodshaw Baptist Church, Chapel Street, Crawshawbooth Reference: Drainage Strategy Job No.: 4533 Revision: B Designer PC Checker AS Date 18/01/2021
Surface Water Sewer A pre-development enquiry has been sent to United Utilities (UU) for this scheme, along with the draft copy of this drainage strategy. We are seeking approval to connect into an existing private surface water manhole in Chapel Street, which can be seen on the image below and also on on the former Rossendale Engineers Department drainage plan found in Appendix B. A proposed drainage strategy drawing can be found in Appendix A.
Photo 2 – Location of surface water manhole in Chapel Street
The private manhole in Chapel Street is believed to connect into the existing public surface water sewer in Burnley Road. The public sewers are shown on United Utilities public sewer records – extract below, and the private drainage is shown on the former Rossendale Engineers Department drainage plan found in Appendix B. Existing and proposed architectural layouts can also be found in Appendix C & D respectively.
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Project: Goodshaw Baptist Church, Chapel Street, Crawshawbooth Reference: Drainage Strategy Job No.: 4533 Revision: B Designer PC Checker AS Date 18/01/2021
Figure 3 – Extract of Public Sewer Map
United Utilities pre-application advice is provided in Appendix E, however they have stated that if the drainage hierarchy has been followed and all other options discounted, they would “consider a connection to the 375mm diameter public surface water sewer located 7.4m East of the proposed site at a pass forward flow to be agreed by the Lead Local Flood Authority. United Utilities request that any agreed rate does not exceed 5 l/s.”
As mentioned above, we are proposing a connection into the private sewer in Chapel Street, which then connects into the 375mm diameter public surface water sewer located East of the proposed site.
We require the following confirmation from the LLFA to allow our drainage design: - Acceptance of our drainage strategy and confirmation that we can connect into the private sewer in Chapel Street - Confirmation of allowable pass forward flow rate (we are proposing 5 l/s) - Confirmation of climate change allowance that our drainage design should account for (we are proposing 40%)
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APPENDIX A
375 dia VC Foul water sewer New + 99.39 Catchment
Area 375 dia VC Foul water sewer
+ 99.39 1 1
Extg SW MH 771 + 98.94 CL 99.23 7 + 98.87
+ 99.02 IL 96.85 BURNLEY ROAD + 98.75 CHAPEL ST 771 + 98.50 + 98.675
+ 98.35 + 98.35
+ 98.94 Extg 375mm Ø public combined sewer
+ 98.225 7 + 98.87 new carparking + 98.10 Existing Catchment Area extg carparking + 99.02 Proposed SW drain BURNLEY ROAD + 97.85 + 98.75 CHAPEL ST G
Extg 375mm Ø public surface water sewer + 97.15
FFL 97.85 + 97.85 G New flow + 98.50 + 98.675 control MH FFL 98.00
Goodshaw Baptist Church SCHOOL STREET 750
Proposed 15 1 SW drain
(assumed highway drain?) Assumed line of extg 150mm Ø SW sewer Fall + 98.35 Catchment Areas + 98.35 1:500 G
Total Site Area = 1600m² Existing Catchment Area = 775m² Fall New Catchment Area = 1175m² New SW Channel drain catchpit MH Increase in Catchment Area = 400m² + 98.225 new carparking G + 98.10
Fall
Channel drain
extg carparking
Proposed SW drain
+ 97.85
New rwp G NOTE: Existing drainage information taken from Public Sewer Records and former Rossendale Engineers + 97.15 Department drainage plan
FFL 97.85 + 97.85 New foul water connection into existing MH 1900 P2 Rev 2 PC AS 18/01/21 FFL 98.00 P1 PRELIMINARY ISSUE PC AS 08/12/20
REV DESCRIPTION BY CHK DATE
New rwp Extg FW MH Ref 1900 Goodshaw Baptist CL 96.20 Church IL 94.70 SCHOOL STREET 750 Edge Structural Design Limited, Chambers Business Centre, Oldham, OL84QQ [email protected] | 0161 620 9988 | edgestructuraldesign.com
Client Members of Goodshaw Baptist Church
Project Goodshaw Baptist Church, Extg 225mmØ public foul water sewer Chapel Street, Crawshawbooth, BB4 8BS
15 1 Drawing Title Drainage Strategy
Project No. 4533
Drawing No. 01
Revision Proposed Drainage Strategy Layout P2 1:125
Original Drawing Size A1 FOR APPROVAL
APPENDIX B
APPENDIX C
extg 375 dia VC Foul water sewer
1 + 99.39
771
+ 98.94
extg parking spaces for houses 5500 7 + 98.87
+ 98.94 SL + 99.02 BURNLEY ROAD + 98.75 CHAPEL ST G + 98.50 + 98.675
+ 98.35 + 98.35 G
+ 98.20
+ 98.50 + 98.225 lawned area extg stone wall
G+ 98.10
+ 97.15 extg carparking + 97.95 + 97.85 grassed banking + 98.50
+ 97.50 G natural stone flagged path
+ 97.15 G + 97.85
Goodshaw Baptist + 97.15 Church FFL 98.00 750
15 1 SCHOOL STREET (un-made)
Existing Site Layout
APPENDIX D
APPENDIX E
Penny Clark
From: Wastewater Developer Services
Follow Up Flag: Follow up Flag Status: Flagged
Good afternoon Penny,
We have carried out an assessment of your application which is based on the information provided. This pre- development advice on your drainage strategy will be valid for 12 months. Your drainage strategy will need to be reviewed by other competent authorities as part of the planning process, and we advise that you carry out the necessary site investigations to confirm the viability of your proposals.
If your investigations require a ccess to our public sewer network, we ask that you contact our network engineers with a request for an access certificate via our main contact telephone number 0345 3723223 or refer to the link below: https://www.unitedutilities.com/builders-developers/working-near-our-assets/
Foul Water
Foul flow from this site will be allowed to drain into the public foul water sewer system using the exsisting connection as proposed in your drainage strategy.
If you are able to identify an alternative, more suitable point of discharge, we request that you contact us at your earliest convenience so that we can assess suitability.
Surface Water
All surface water flow from the proposed development should drain in-line with the drainage hierarchy, as outlined in Paragraph 80, (Reference ID: 7-080-20150323), of the National Planning Practice Guidance. We also recommend you prioritise the use of multi-functional sustainable draina ge systems for the management of surface water in accordance with national planning policy.
Generally, the aim should be to discharge surface run off as high up the following hierarchy of drainage options as reasonably practicable. This is outlined as follows, in order of priority: 1. into the ground (infiltration); 2. to a surface waterbody; 3. to a surface water sewer or highway drain; 4. to a combined sewer. For guidance, The North West SuDS Pro-Forma provides information on the appropriate evidence required at each stage of the hierarchy, to demonstrate how each level has been discounted.
1 The Lead Local Flood Authority has responsibility for all surface water drainage concerns and their input to your proposal is critical. You should also consider whether it is necessary to discuss your proposal with the Environment Agency, or Internal Drainage Board (if operating in your area).
The Local Planning Authority are the determining authority for any application for planning permission and the appropriate authority for determining cost viability of a proposed drainage scheme, such assessments are outside of the jurisdiction of United Utilities.
Infiltration
Surface water runoff generated from this development should discharge to the ground via infiltration system where feasible. We acknowledge your drainage strategy which suggests the ground is not suitable for infiltration.
Waterbody
If an evidence based assessment has been carried out and confirms that infiltration is not feasible, we recommend that you contact the Lead Local Flood Authority and/or Environment Agency to discuss a point of discharge to the watercourse 126 m West of the proposed site.
We would encourage you to identify and engage with any third party landowner and riparian owner to agree access and discharge rights to the water body if this is not in your ownership.
2 Public Sewer
In accordance with the hierarchy of drainage options within the National Planning Practice Guidance, both discharge to ground via infiltration and discharge to a waterbody should be discounted prior to consideration of discharging surface water to the public sewer system. Evidence should be provided to demonstrate how these have been discounted, as outlined in the North West SuDS pro-forma.
Once evidence is provided as outlined above, United Utilities will consider a connection to the 375mm diameter public surface water sewer located 7.4m E ast of the proposed site at a pass forward flow to be agreed by the Lead Local Flood Authority. United Utilities request that any agreed rate does not exceed 5 l/s.
As a Water Company, we have no obligation to accept highway drainage into our public sewer network. However, should your proposals include runoff from highways, we would request that consideration is given to SuDS components that deliver source control are incorporated within the design of the scheme to reduce the volume and frequency of discharges of these flows to the public sewer.
Levels
For low-lying sites, (where the ground level of the site or the level of a basement is below the ground level at the point where the drainage connects to the public sewer), care should be taken to ensure t hat the property is not at increased risk of flooding. If these circumstances exist, we recommend that you contact us to discuss further. It could affect the detailed design of your site and result in the need to incorporate appropriate mitigating measur es in your drainage scheme.
Existing Water Assets Crossing the Site
It is the developer responsibility to identify utilities on-site. Where clean water assets are shown on our records, we recommend that you contact our Water Pre-Development Team, via the following email address: [email protected] . Further information for this service can be found on our website via the link below: https://www.unitedutilities.com/builders-developers/larger-developments/pre-development/water-pre-dev/
Connection Application
Althoug h we may discuss and agree discharge points and rates in principle, please be aware that you will have to apply for a formal sewer connection. This is so that we can assess the method of construction, Health & Safety requirements and to ultimately inspect the connection when it is made. Details of the application process and the form itself can be obtained from our website by following the link below: https://www.unitedutilities.com/builders-developers/larger-developments/wastewater/sewer-connections/
We recommend that the detailed design should confirm the locations of all utilities in the area and ensure that any proposed drainage solution considers routing and clash checks where required.
If we can be of any further assistance please don’t hesitate to contact us further.
Kind regards,
3 Marie Mura Assistant Developer Engineer Developer Services & Metering Customer Services T: 01925 537745 unitedutilities.com
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From: Penny Clark [mailto:[email protected]] Sent: 08 December 2020 09:39 To: Wastewater Developer Services
To whom it may concern,
Please find attached a completed pre-development enquiry form, site location plan, proposed site layout and drainage strategy for the above project.
If you require any further information, please let me know.
Kind regards,
Penny Clark BSc(Hons) PROJECT ENGINEER [email protected] 0161 620 9988 07859 982510
4 Edge Structural Design Limited Chambers Business Centre Chapel Road Oldham
OL8 4QQ
edgestructuraldesign.com
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