kensington and chelsea local suds decision tool tool user guide... · 2012-10-25 · suds decision...

Kensington and Chelsea Local SuDS Decision Tool User Guide

The Royal Borough of Kensington and Chelsea

October 2012

Final Report

9W8590

All rights reserved. No part of this publication may be reproduced in any form, including photocopying or, transmitted by electronic means or stored in an electronic retrieval system without express permission in writing from Haskoning UK Ltd. This report has been prepared by Haskoning UK Ltd solely for The Royal Borough of Kensington and Chelsea in accordance with the terms of appointment for the production of a SuDS in small developments Decision Tool dated 10th August 2011and should not be relied upon by third parties for any use whatsoever without express permission in writing from Haskoning UK Ltd.

A company of Royal Haskoning

Document title Kensington and Chelsea Local SuDS Decision Tool

User Guide

Document short title SuDS Decision Tool – User Guide

Status Final Report

Date October 2012

Project name SuDS in Small Developments Decision Tool

Project number 9W8590

Client The Royal Borough of Kensington and Chelsea

Reference 9W8590/R120914/303313/Hayw

Burns House

Harlands Road

Haywards Heath, West Sussex RH16 1PG

United Kingdom

+44 1444 458551 Telephone

01444 440665 Fax

[email protected] E-mail

www.royalhaskoning.com Internet

HASKONING UK LTD.

WATER

Drafted by Richard Stevens

Checked by Folahan Ogunyoye / Helena Wicks

Date/initials check 14/09/12 HW

Approved by Folahan Ogunyoye

Date/initials approval 14/09/12 FO

SuDS Decision Tool – User Guide 9W8590/R120914/303313/Hayw

Final Report -iii- October 2012

CONTENTS Page

1 INTRODUCTION 1

2 COPYRIGHTS AND DISCLAIMERS 2

3 DATA INPUT 3

3.1 Existing Site Conditions 3

3.2 Developed Site Conditions 3

3.3 Site Constraints 4

3.4 Example Completed Data Input Form 6

4 APPROPRIATE SUDS AND VOLUME REQUIREMENTS 7

4.1 Indicative Attenuation Storage Volumes 7

4.2 SuDS Guidance 8

5 REPORTING 9

6 EXITING THE DATABASE 9

APPENDIX A – EXAMPLE REPORT 10

9W8590/R120914/303313/Hayw SuDS Decision Tool – User Guide

October 2012 -iv- Final Report


Final Report -1- October 2012

1 INTRODUCTION

This document gives a brief overview of how to use the Royal Borough of Kensington and Chelsea (RBKC) Small Scale SuDS Decision Tool. The tool is a Microsoft Access database. To open the tool double click on Small Scale SuDS Tool.mdb. The tool is designed such that for each individual development application a new database is used from a master copy. Once the master copy has been opened the database should be saved with a new file name that includes the unique planning application reference number.

This is the front screen and from here you can access the data input sheet of the tool. It sets out the background and key assumptions to the tool that any new user should read and understand before starting to use the tool. The about button gives the user information about the origins of the tool and its legal status as shown below:


October 2012 -2- Final Report

To start using the tool the user needs to click on the start button to access the data input page.

2 COPYRIGHTS AND DISCLAIMERS

Any use or re-use of the tool is subject to the restrictions set out in the About information box. Any external modifications carried out to the tool cannot be verified in terms of the outputs derived as a result of these amendments. The tool provides a summary of the SuDS solutions that the user is committing to provide with the development proposal and will need to be reflected in the drawings submitted with the planning application. This should be designed by a suitably qualified professional. The use of the tool and submission of the output report is deemed to be a declaration of honesty that the tool has been used in the manner it was intended without external amendment or modification.



3 DATA INPUT

The data input page allows the user to input the required information about the development proposal. The data input page is shown below:

Site location, postcode and planning application reference are entered in the appropriate boxes to enable easy identification of the development proposal.

3.1 Existing Site Conditions

The existing site conditions of the total site area and existing impermeable area on the site are entered into the appropriate boxes to allow the tool to calculate the hydrological conditions and requirements.

An ‘i’ box is included beside the Impermeable area of existing site to provide further guidance. These are used throughout the tool for this purpose and can be accessed by clicking on the ‘i’ symbol.

3.2 Developed Site Conditions

The developed site conditions required by the tool are the type of new development being considered and the impermeable area of the site which will result from this development. A list of possible new development types can be entered from the drop-



down list supplied. Development types not on this list have not been considered by the tool. An ‘i’ box is included beside to provide further guidance.

The area of impermeable ground surface after development is required to calculate the hyrdological requirements for the SuDS solution. An ‘i’ box is included beside to provide further guidance. The type of surfaces present in the new development affect the number of water quality treatment stages required by the SuDS solution. This is based on the guidance provided by the SuDS Manual (CIRIA 2007). The type of surface present in the development can be selected from the drop down box as shown below. An ‘i’ box is included beside to provide further guidance.

3.3 Site Constraints

There are site specific constraints within RBKC that may affect the use of certain types of SuDS. If one of the appropriate constraints applies to the development proposal in question then the corresponding tick box should be selected.

The majority of the borough is designated a conservation area for heritage reasons and there are numerous listed properties. To assist the user in deciding whether the property is within a conservation area a map is included within the tool that can be opened when the View Map button is clicked. Once opened the map can be enlarged by clicking on the appropriate location as shown below.



If a property is listed or the development is located within a conservation area this may impact upon the types of SuDS features than can be applied. Green roofs in particular may be an issue if they alter the apperance of the area or the property being developed. RBKC should be consulted to determine the restrictions that would apply.



3.4 Example Completed Data Input Form

Below is an example of a completed data input form for a theoretical development.



4 APPROPRIATE SUDS AND VOLUME REQUIREMENTS

Clicking on the next button from the data input form will take the user to the second form of the tool which provides an indicative appraisal of the applicable SuDS features which could supply the necessary attenuation storage. This can be compared with the required attenuation storage calculated by the tool which is displayed in the box at the bottom of the form. The appropriate SuDS features are dependent upon the type of development and are listed with the ranking appropriate to RBKC. In addition the number of treatment features required to achieve the water quality requirements is also indicated. An example is shown below:

4.1 Indicative Attenuation Storage Volumes

For some of the SuDS features suggested the user can input a size and the tool will give a range of attenuation storage volumes that could be achieved. These volumes are indicative and would change depending upon site specific considerations and constraints that may affect the SuDS features. The size is inputted either in terms of the surface area covered by the SuDS feature (e.g. permeable pavements, ponds and basins), length (e.g. swales) or number of properties (e.g. rainwater harvesting). The total range of attenuation storage that may be achieved by the combination of SuDS selected is given in the box below the individual SuDS types. The colour of the box will change depending upon whether enough storage has been provided or not. If there is too little it will remain red, if the volume required sits between the upper and lower estimate of the volume potentially provided it will be amber and green amount required is lower than the lower end of the range that potentially is being provided.



An example of a completed form is shown below:

4.2 SuDS Guidance

Additional guidance on the different types of SuDS features is also available by clicking the guidance button. This displays a new window which informs the user what the feature is, basic best practice guidance on their design and directs the user to sources of further information that should be consulted to undertake detailed designs. The guidance box for green roofs is shown below as an example:



5 REPORTING

Once the data input and attenuation storage volume forms have been completed the user can produce a report outlining the results of the tool. By clicking the Preview Report button at the bottom of the form the user will see the message below to ensure they are happy with the outputs before moving onto the final report.

The report gives all the relevant information supplied by the user, indicative sizes of appropriate SuDS, the hydrological conditions and attenuation requirements, water quality requirements and relevant guidance for all the SuDS features that could be used. An example report for a theoretical development is shown in Appendix A. To save the report electronically it can be printed to a .pdf document or, alternatively, a hard copy of the report may be printed.

6 EXITING THE DATABASE

To exit the database the user can click on the exit button on any of the forms.

A company of Royal Haskoning

Appendix A – Example Report

Small Scale SuDS Tool

Site Location 15 Hollywood Road, Royal Borough of Kensington and Chelsea, London

Postcode SW10 9HT

Greenfield runoff rate (1 in 100yr) 4.9

Greenfield runoff rate (QBAR) 1.5

Hydrological Conditions

l/s/ha

l/s/ha

Site Summary

Planning Appl. No. App001 (for reference only)

Storage Requirement

Volume of attenuation storage 1.00 m³

SuDS treatment features required 1

Water Quality Requirement

m²m²

m²

Existing Site Conditions Developed Site Conditions

Total impermeable area 80Total impermeable area 60

Type of development ExtensionTotal area of site 100

SuDS treatment features are individual SuDS measures that treat water filtration and detention, the water quality performance varies between different SuDS features. If multiple features are required these must be linked to ensure that adequate treatment is provided before water reaches the receiving water course.

Rainwater harvesting and geocellular systems are not considered as treatment features due to their poor pollutant removal performance.

The table below shows the SuDS solutions you are co mmitting to provide with the development proposal and will need to be reflected in the drawings submitted with the planning application. This solution should be desig ned by a suitably qualified professional.

Appropriate SuDS SolutionsProposed Size of

SuDS OptionsPotential Volume of

AttenuationRank

1 Green Roofs 25 m² 0.63 2.88to m³May be inappropriate due to conservation area/listed building.

1 Brown Roofs m² to m³May be inappropriate due to conservation area/listed building.

1 Rainwater Harvesting 1 properties 2.00 2.00to m³

3 Geocellular Systems m² to m³

Site Constraints

Conservation Area


SuDS treatment features are individual SuDS measures that treat water filtration and detention, the water quality varies between different SuDS features. If multiple features are required these must be linked to ensure that adequate treatment is provided before water reaches the receiving water course.

Yes2.63 4.88to m³Proposed indicative volume of attenuation storage

Guidance

Green Roofs Green roofs comprise systems that cover the roof of a building with a vegetation cover over a drainage layer. They intercept and store rainwater attenuating flows and improving water quality.

The water storage capacity is highly dependent upon site-specific considerations, however the main factors are vegetation cover, and the size of the drainage layer that the building can support. The range of indicative storage volumes suggested is based upon the impact of different types of vegetation cover in a typical situation. If the roof has the capacity to accept higher than normal loading its storage capacity could increase.

Further information can be found in the SuDS Manual (CIRIA 2007) and the Environment Agency’s Green Roof Toolkit. Detailed guidance on the design of green roofs for run-off attenuation has been developed in Germany by Forchungsgellschaft Landschaftsentwicklung und Landschaftsbau.

http://www.ciria.com/http://www.environment-agency.gov.uk/http://www.fll.de/

RBKC accepts no responsibility for data held on other websites, the location of which may be changed by the third party without notice.

Brown Roofs Brown roofs comprise systems that cover the roof of a building with vegetation cover over a drainage layer. They intercept and store rainwater attenuating flows and improving water quality.

Brown roofs are similar to green roofs, sharing many of the same benefits and construction methods. However the focus is to deliver biodiversity benefits in terms of variety of species and habitat provision.

The water storage capacity is highly dependent upon site-specific considerations, however the main factors are vegetation cover, and the size of the drainage layer that the building can support. The range of indicative storage volumes suggested is based upon the impact of different types of vegetation cover in a typical situation. If the roof has the capacity to accept higher than normal loading its storage capacity could increase.

Further information can be found in the SuDS Manual (CIRIA 2007), the Environment Agency’s Green Roof Toolkit and at BrownRoofs.co.uk. Detailed guidance on the design of green roofs for run-off attenuation has been developed in Germany by Forchungsgellschaft Landschaftsentwicklung und Landschaftsbau.

Http://www.ciria.com/http://www.environment-agency.gov.uk/http://www.fll.de/http://www.brownroofs.co.uk/



Rainwater Harvesting Rainwater harvesting involves storing rainwater that falls onto roof surfaces for use by the property owner. This can vary between relatively small water butts and more complex systems incorporating underground storage tanks. Water butts are not generally designed to provide storage of rainwater in extreme events and therefore cannot be included as part of the storage assessment for a site. This is the case because if they are already full they will not provide storage in any given rainfall event.

Rainwater harvesting systems are generally larger and offer greater potential for management of storm water in addition to providing water for reuse within properties. The amount of storage that can be provided for dealing with storm water is dependent upon the system installed, however the SuDS Manual suggests that for a standard house the typical storm water component is 2m³ (CIRIA, 2007).

http://www.ciria.com/http://www.environment-agency.gov.uk/


Geocellular Systems Geocellular systems are typically modular plastic systems with high void ratios that can be used to create below ground storage structures. They provide significant storage volumes and flow attenuation, however do not provide any of the other benefits of SuDS such as treatment, ecology or amenity.

The SuDS Manual (CIRIA, 2007) states that geocellular systems should be designed in accordance with Sewers for Adoption 6th Edition (WRc, 2006). The typical void ratio for tanked systems is 0.9; therefore the storage capacity can be taken as 90% of the volume of the storage layer. The typical depths of storage tanks vary between 0.2m and 0.5m depending upon the product used.

The range of indicative storage volumes suggested is based upon the range of systems avalable on the market. The amount of storage may be increased if products allow multiple layers to be used and there are no other site-specific constraints.

http://www.ciria.com/http://www.environment-agency.gov.uk/


kensington and chelsea local suds decision tool tool user guide... · 2012-10-25 · suds decision...

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