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Dandi Nine Ltd Vaughan Road Aparthotel
Planning Stage Drainage Strategy Vaughan Road Aparthotel
Vaughan Road Aparthotel Planning Stage Drainage Strategy copy MLM Consulting Engineers Limited
mlmipscomworkTier2MLM66010006601343MLMREPDrainage Report
Notice
This document and its contents have been prepared and intended solely for Dandi Nine Ltd information and use in relation to the Vaughan Road Aparthotel scheme
MLM Consulting Engineers Limited assumes no responsibility to any other party in respect of or arising out of or in connection with this document andor its contents
Document History
Client Dandi Nine Ltd Project Vaughan Road Aparthotel Document Title Planning Stage Drainage Strategy Document Reference 6601343-MLM-ZZ-XX-RP-C-0001 MLM Reference JR 6601343 JJB
Revision Status Description Author CheckedApproved Date
P01 S2 Issued for Comment James Noble Martin Cozens 28082020
P02 S2 Amendments throughout James Noble John Barrell 22092020
Vaughan Road Aparthotel Planning Stage Drainage Strategy copy MLM Consulting Engineers Limited
mlmipscomworkTier2MLM66010006601343MLMREPDrainage Report
Contents
1 Introduction 1
2 Thames Water Asset Map 1
3 Foul Drainage 2
31 Existing Foul Water Drainage 2 32 Proposed Foul Water Drainage 2
4 Flood Risk 3
5 Exceedance Routes 3
6 Surface Water Drainage 4
61 Existing Surface Water Drainage 4 62 Proposed Surface Water Drainage 4
7 Treatment 5
8 Future Maintenance 6
9 Conclusion 6
91 Foul Water 6 92 Surface Water 7
Appendix A - Thames Water Correspondence
Appendix B - Thames Water Pre-planning Enquiry
Appendix C - Flood Exceedance Routes
Appendix D - Drainage Calculations
Appendix E - Drainage Strategy
Appendix F - SuDS Maintenance Plan
Appendix G - Foul Water Pump Specification
Appendix H - Surface Water Pump Specification
Vaughan Road Aparthotel Planning Stage Drainage Strategy copy MLM Consulting Engineers Limited
mlmipscomworkTier2MLM66010006601343MLMREPDrainage Report 1
1 Introduction
This report has been prepared for the sole use of Dandi Nine Limited and the contents should not be relied upon by others without the express written authority of MLM Consulting Engineers Limited If any unauthorised third party makes use of this report they do so at their own risk and MLM owes them no duty of care
MLM have been appointed for the Civil and Structural design of a new aparthotel in Harrow
The proposed 129 room aparthotel with associated fifth-floor restaurant gym ground floor commercial space external hard and soft landscaping small car parking area to the rear of the site and external amenity space located on an existing (disused) carpark on Vaughan Road Harrow The current site is approximately 012ha and mostly impermeable with a small area of vegetation verge running along the northern and eastern boundaries
MLM were also appointed in 2017 for Civil and Structural design for a previous residential scheme on the same site which gained various approvals in relation to the sites surface amp foul water connections and flood exceedance routes
This report has been produced in support of the proposed developments planning application and relates to all onsite private drainage proposals within the sites red line boundary only All offsite works beyond the sites boundary is not included within this report
Whilst this report will discuss elements of flood risk a flood risk assessment (FRA) is not required under NPPF guidelines due to the size of the site being below 10ha and its location within flood zone 1
2 Thames Water Asset Map
Figure 1 below is an extract of Thames Water assets located in surrounding the site The map has been extracted from correspondence with Thames Water within Appendix A
Figure 1
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3 Foul Drainage
31 Existing Foul Water Drainage
There are no known existing foul sewers located on the existing car park site With reference to Thames Water Asset plans all potential offsite existing foul sewer connection points have been assessed as follows
There are a number of other existing Thames Water Foul manholes located approximately 45m to the East adjacent to the BP garage Any proposed connection to these sewers would require crossing the busy Bessborough Road therefore connection into this sewer has been discounted
The nearest existing Thames Water Foul sewer is located 25m to the West along Vaughan Road indicated as Manhole EXFW A on the drainage strategy drawing 6601343-MLM-ZZ-XX-DR-C-0001 within Appendix E A number of smaller adoptable sewers connect from the recently built houses (4No) to the West of the development which connect into the head of the existing Thames Water main foul sewer
No manhole reference cover or invert level information has been identified on the Thames Water records and all existing site surveys do not extend to this location It is proposed to connect the developments onsite foul network to a new length of gravity sewer within Vaughan Road discharging into manhole EXFW A
In advance of detail design further survey works will need to be carried out to confirm the assumed invert level of existing Thames water manhole EXFW A
32 Proposed Foul Water Drainage
The Northern lower half of the development is at a lower level that Vaughan Road with an approximate proposed floor level of 649m The proposed private onsite foul network therefore will have an approximate outfall invert level of 6374m
The developments foul outfall connection point at Thames Water manhole EXFW A is assumed to have the water authority minimum standard depth to invert of 12m resulting in an invert level of approximately 6395m
The invert level of existing manhole EXFW A is therefore higher than the onsite invert level which means a full gravity connection will not be feasible
It is therefore proposed to use an onsite private package pump with associated 24hr storage (storage in manhole or tank) and pump flows at an agreed rate with Thames Water to a final onsite gravity manhole Details of the foul pump can be found within Appendix G
From the boundary of the development a new foul gravity sewer will be constructed below Vaughan Road to existing manhole EXFW A The new foul sewer will be constructed in accordance with Thames Water requirements and will be offered for adoption under a Section 104 agreement
A pre-planning enquiry was submitted to Thames Water for the proposed connection into the existing manhole EXFW A at a peak discharge rate of 82ls Thames Water have confirmed in principle that this connection point and discharge rate are acceptable For further detail refer to Thames Water Pre-planning enquiry Appendix B
All proposals are subject to the additional survey work described above a Thames Water Section 106 and Section 104 application (and Thames Water approval) and full coordination with the design team at detailed design
Vaughan Road Aparthotel Planning Stage Drainage Strategy copy MLM Consulting Engineers Limited
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Details of the proposed foul drainage strategy can be found on drawing 6601343-MLM-ZZ-ZZ-DR-C-0001 within Appendix E
4 Flood Risk
The site is located within flood Zone 1 and is smaller than 10ha therefore the site is considered Low Risk and a scheme specific flood risk assessment (FRA) is not required
The below extract taken from the GOVUK Flood Risk from Surface Water indicates a very low risk with no surface water flooding onsite
There is however Low Risk surface water flooding on the adjacent highway (Vaughan road) A new drop crossing is required to access the site from Vaughan Road This crossing and all works along the existing highway site boundary to the south will retain the existing levels Therefore risk of flooding from offsite will not be effected with the onsite risk remaining very low
5 Exceedance Routes
In accordance with good drainage practice consideration must be given to the effects of drainage system failure or for storm events greater than those used in the design analysis
lsquoSurface Water Flood Flow and Exceedance Routesrsquo drawing 6601343-MLM-ZZ-XX-DR-C-0002 shows proposed finished floor and external levels above ground exceedance flow routes (blue arrows) across the site which routes run-off away from the new building and prevents water leaving site In extreme cases the flood waters will overtop into a high level overflow pipe as indicated by the red arrow preventing surface water from entering the building The lsquoSurface Water Flood Flow and Exceedance Routesrsquo drawing is included as Appendix C
Vaughan Road Aparthotel Planning Stage Drainage Strategy copy MLM Consulting Engineers Limited
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6 Surface Water Drainage
61 Existing Surface Water Drainage
An existing 25m diameter 135m deep concrete Thames Water trunk sewer crosses the site in the South East corner
During the previous residential scheme Thames Water requested a build over or near agreement be entered into to ensure the proposed development does not impact the trunk sewer The new Aparthotel scheme has where appropriate ensure that Thames Waterrsquos build over or near requirements have been met when positioning the building and developing the preliminary foundation design A full detailed application will be made to Thames Water at the detail design stage
The scheme site survey has confirmed that the previous car park drained via five existing gullies located on the lower Northern boundary of the car park A CCTV survey confirmed that these gullies discharge to a lsquoyrsquo connection at point 901B as shown on the Thames Water asset map From point 901B the sitersquos surface water discharges into the existing Thames Water network within the adjacent underpass manhole ref 9009
The existing underpass network then outfalls to an existing 28m diameter 812m deep Thames Water surface water catchpit ref 901A located in the South Eastern corner of the site The catchpit then discharges via a 300dia sewer to the trunk sewer below
62 Proposed Surface Water Drainage
The developments proposed surface water run-off from the building will be collected via a combination of green blue roof and rainwater pipes with the external hard paved areas by porous paving
The inclusion of a large roof garden and smaller planted roof terraces (green roofs) not only increases the bio-diversity water treatment and improves air quality of the existing site which currently is predominantly hard paved but also aids with the capture control and delay of surface water runoff at source A portion of the surface water will also be harvested for irrigation purposes The inclusion of porous paving for the external hard paved areas will also contribute to water treatment control and delay of surface water runoff at source
Due to the non-porous nature and restricted external space infiltration is not feasible The surface water run-off will therefore be conveyed to a below ground attenuation tank located below the external car park The attenuation tank and associated network will be installed approximately 2-25m deep due to the low lying level of the adjacent underpass and eastern courtyard
The developments will re-use the existing carparks surface water outfall A new adoptable onsite demarcation chamber will be required at the boundary of the site and a new adoptable manhole (ref 901B) will be built on the line of the existing 150dia lateral sewer The existing offsite 150dia sewer downstream of the new manhole is to be offered for adoption by Thames Water
The surface water offsite discharge rate will be restricted to 50 ls for up to and including the 1 in 100 year storm event plus a 40 allowance for climate change Due to the depth of the proposed drainage network and attenuation it will be necessary to pump surface water flows up into the demarcation chamber From this point surface water will flow by gravity into manhole 901B Details of the surface water pump can be found within Appendix H
A high level overflow from the pump chamber to the demarcation chamber will also be installed to ensure that in the unlikely event of pump failure surface water flows will overtop into the network and not flood the building or leave site
Vaughan Road Aparthotel Planning Stage Drainage Strategy copy MLM Consulting Engineers Limited
mlmipscomworkTier2MLM66010006601343MLMREPDrainage Report 5
The proposed discharge rate of 50ls connection point and adoption of the existing 150dia lateral sewer have been approved in principle by Thames Water Correspondence can be found within Appendix A The proposed connection will be subject to full technical approval and a Thames Water Section 106 agreement during the detailed design
The design team have liaised with Harrow InfrastructureHighways team throughout the pre-planning stage and have received confirmation that in principle the strategy is acceptable
It is proposed to attenuate in below ground storage tanks and where achievable within the porous paving sub-base Based on the restricted 50ls an onsite attenuation volume approximately 50m3 ndash 72m3 (with the 40 climate change) will be required for the development For the surface water calculations please refer to Appendix D
Details of the proposed surface water drainage strategy can be found on drawing 6601343-MLM-ZZ-ZZ-DR-C-0001 within Appendix E
7 Treatment
With reference to the SuDS manualrsquos pollution hazard land use classification table 262 the Aparthotel roof and external pedestrian areas parking spaces are classified as having a very low and low pollution hazard levels respectively
The required hazard indices for a site of this type should achieve or better the hazard indices identified for Total suspended Solids Metals and Hydrocarbons Refer to Figure 1 below indicating the SuDS manual
Table 262 Figure 1 ndash Pollution hazard indices for different land use classification Table 262
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mlmipscomworkTier2MLM66010006601343MLMREPDrainage Report 6
In order to provide adequate treatment the proposed drainage network components should have a total pollution migration index that equals or exceeds the pollution hazard index In order to comply with these requirements a series of individual components within the proposed network is required In line with the SuDS manual factor of 05 is to be used to account for the reduced performance of the secondary or tertiary components associated with already inflow concentrates
Please refer to table 2 for scheme specific pollution mitigation indices
Surface Water Runoff
Treatment -Individual devicesequence
Total suspended solids mitigation index
Total metals mitigation index
Hydrocarbons3
Residential Roof Debris leaf guard within roof gutters
Sealed downpipes
Catchpit Siltrap Manholes
Blue Green Roof
Reference to Chapter 24 of the SuDS manual table 43 Minimum water quality requirements for discharge to receiving surface waters and groundwater
States for very low pollution hazard level the requirement for discharging to groundwater is the lsquoRemoval of gross
solids and sediment onlyrsquo
Private porous external pedestrian areas and parking spaces
Porous Paving with type 3 sub-base
07 06 07
Table 2 ndash Scheme Pollution Mitigation Indices
The total proposed treatment for the private drainage networks will provide appropriate levels of water quality treatment prior to discharge to Thames Water network
8 Future Maintenance
Maintenance of SuDS features shall be carried out in accordance with the MLM document entitled lsquoSurface Water Drainage Maintenance Planrsquo This is included as Appendix F
9 Conclusion
The schemes proposed foul and surface water drainage strategy detailed within the report identifies the intended means of connection and discharge of estimated peak flows The design team have liaised with Harrow Highways Infrastructure team and Thames Water throughout the pre-planning stage and have received confirmation in principle that both the surface water and foul water strategies are acceptable
Summary of foul and surface water drainage strategy
91 Foul Water
911 The developments foul water connection is based on a peak flow rate of 82 ls discharging into the existing Thames Water manhole EXFW A to the West of the development in Vaughan Road
912 Thames Water have confirmed that the proposed peak flow rate and connection into their foul sewer in Vaughan Road is acceptable in principle and will not have a detrimental effect on their network
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913 Connection details of the proposed Section 104 gravity sewer within Vaughan Road into the existing Thames Water foul manhole will be subject to confirmation of the invert level
92 Surface Water
921 The developments surface water will discharge at a maximum of 5ls for all storms up to and including the 1 in 100 year storm event plus 40 allowance for climate change The development will discharge via the existing car parks outfall lateral outfall
922 Thames Water have confirmed that the proposed surface water discharge rate adoption of the 150dia lateral and ultimate connection into their trunk sewer below site is acceptable in principle and will not have a detrimental effect on their network
An approved Thames Water pre-planning enquiry has been received for the developments foul and surface water discharge Refer to Appendix B for details
Both connections will be subject to Thames Water full technical approval at detail design
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Appendix A - Thames Water Correspondence
From Siva RajaratnamTo John BarrellCc James NobleSubject RE 6601343 - RE RE DS6075526 - Pre-planning enquiry Car Park Vaughan Road Harrow HA1 3XDDate 14 August 2020 102423Attachments image001jpg
image003jpgimage004jpg
Hi John This will be acceptable to Thames Water RegardsSiva RajaratnamDeveloper Services ndash Adoptions Engineer Mobile 07747 640477 Landline 0203 577 9811 sivarajaratnamthameswatercouk
Clearwater Court Vastern Road Reading RG1 8DB Find us online at developersthameswatercouk
From John Barrell ltJohnBarrellmlmgroupcomgt Sent 13 August 2020 1827To Siva Rajaratnam ltSivaRajaratnamthameswatercoukgtCc James Noble ltJamesNoblemlmgroupcomgtSubject RE 6601343 - RE RE DS6075526 - Pre-planning enquiry Car Park Vaughan Road Harrow HA13XDImportance High
This email contains a reference to Coronavirus or COVID-19 Please be aware ofcoronavirus-themed active phishing campaigns and use extra vigilance whenresponding or clicking
Many thanks for the swift reply Siva Yes we would pump up to a manhole within the site boundary then gravity into a new manhole atlocation 901A We do not believe there is currently a manhole at location 901A we believe there is a lsquoyrsquo connectiononly On this basis we would propose a new manhole (to adoptable standards) at location 901A Wewould then put new manhole 901A and the existing downstream 150mm dia lateral to manhole 9009forward for Thames Water adoption This would of course be subject to a formal adoption process toThames Waters requirements at detail design We have updated the design to reflect the above and also updated manholes pipes that are nowconfirmed to be in Thames Waters ownership Details have been clouded on the attached drawing6601343-MLML-ZZ-XX-DR-C-0001 P03 Please note that the development boundary is indicated by the red dashed line and so the area to theeast is currently highway owned It should also be noted that this existing sewer does pass parallel with the new building frontagehowever all necessary protection measure will be in place and CCTV survey carried out (if required)to ensure all existing sewers are not affected by the works If you could confirm the above is acceptable in principle (subject to Thames Waters adoption S106
requirements) at the previously agreed 5ls SW discharge rate we can confirm back to the plannersthat we have an agreeable solution Thanks again for your help Happy to discuss over the phone Kind regards
John BarrellSenior Engineer
D +44 1473 350114M +44 7736 058012T +44 1473 231100E JohnBarrellmlmgroupcomA MLM Group North Kiln Felaw Maltings 46 Felaw Street Ipswich Suffolk IP2 8PNW wwwmlmgroupcom
Buildings bull Infrastructure bull Compliance bull Environment
One to Watch Best Company 2020
Twitter bull LinkedIn bull Instagram bull YouTube
Emails are sent on behalf of the MLM company which is named in the relevant signed appointment or if noneexists in our fee proposal or (if MLM is acting as client) in our order Companies Act information for MLM Groupcompanies is available at wwwmlmgroupcomcompanies-act-information
For COVID-19 client service continuity update please click the link httpswwwmlmgroupcomnews-centrenewsclient-update-sweco-business-continuity
From Siva Rajaratnam [mailtoSivaRajaratnamthameswatercouk] Sent 13 August 2020 1416To John Barrell ltJohnBarrellmlmgroupcomgtCc James Noble ltJamesNoblemlmgroupcomgtSubject RE 6601343 - RE RE DS6075526 - Pre-planning enquiry Car Park Vaughan Road Harrow HA13XD Hi John The method of connection would be checked as part of the S106 but an external backdrop (backdrop isoutside of the manhole chamber) would be possible with the connection at the soffit level of theoutgoing pipe Manhole 901B is a private manhole as this is only serving the one property Where the pipe leaves theproperty boundary it becomes Thames Waters responsibility We can only adopt the gravity drainageoutside of the property boundary and the pumped flows should discharge within the site and then bygravity to a Thames Water sewer to be consider for adoption I happy to discuss this further on the phone if you have any further queries Regards
Siva RajaratnamDeveloper Services ndash Adoptions Engineer Mobile 07747 640477 Landline 0203 577 9811 sivarajaratnamthameswatercouk
Clearwater Court Vastern Road Reading RG1 8DB Find us online at developersthameswatercouk
From John Barrell ltJohnBarrellmlmgroupcomgt Sent 13 August 2020 1349To Siva Rajaratnam ltSivaRajaratnamthameswatercoukgtCc James Noble ltJamesNoblemlmgroupcomgtSubject RE 6601343 - RE RE DS6075526 - Pre-planning enquiry Car Park Vaughan Road Harrow HA13XDImportance High
This email contains a reference to Coronavirus or COVID-19 Please be aware ofcoronavirus-themed active phishing campaigns and use extra vigilance whenresponding or clicking
Hi Siva No problem thanks for your email it cleared up a number of issues and provides us with a possiblealternative connection which is great Before we look further into a connection at 8002 we would be grateful if you could confirm thefollowing
It seems that it may be feasible to connect into the onsite SW catchpit ref 901A which yourrecords confirm is owned by Thames Water by means of an external backdrop
The developments original connection Option 1 which you previously approved in principleutilises the existing 150 dia pipe from the old car park between the blue dot ref 901B and9009 Can you please confirm if Thames Water own this sewer as it is not clear from theimage If Thames Water do own the car park lateral or would be prepared to adopt it as part ofthe new development then we should be in a position to revert back to the original connectionoption 1 This would negate the need to backdrop or pipe down the road
I would be happy to discuss if it is easier and am avaible on the mobile number below Many thanks again for your continued assistance on this project it is greatly appreciated Kind regards
John BarrellSenior Engineer
D +44 1473 350114M +44 7736 058012T +44 1473 231100E JohnBarrellmlmgroupcomA MLM Group North Kiln Felaw Maltings 46 Felaw Street Ipswich Suffolk IP2 8PN
W wwwmlmgroupcom
Buildings bull Infrastructure bull Compliance bull Environment
One to Watch Best Company 2020
Twitter bull LinkedIn bull Instagram bull YouTube
Emails are sent on behalf of the MLM company which is named in the relevant signed appointment or if noneexists in our fee proposal or (if MLM is acting as client) in our order Companies Act information for MLM Groupcompanies is available at wwwmlmgroupcomcompanies-act-information
For COVID-19 client service continuity update please click the link httpswwwmlmgroupcomnews-centrenewsclient-update-sweco-business-continuity
From Siva Rajaratnam [mailtoSivaRajaratnamthameswatercouk] Sent 13 August 2020 1330To John Barrell ltJohnBarrellmlmgroupcomgtCc James Noble ltJamesNoblemlmgroupcomgtSubject RE 6601343 - RE RE DS6075526 - Pre-planning enquiry Car Park Vaughan Road Harrow HA13XD Good afternoon John Sorry it appears I have overlooked your original email High level connections will not be accepted and an external backdrop should be used if you wish toconnect to a deep sewer An alternative point of connection is surface water manhole 8002 (next toyour foul water connection) although this is only 151m deep It appears the catch pit manhole you mention is manhole 901A as per below sewer records If so this isa Thames Water manhole
Should you have any further queries please feel free to contact me RegardsSiva RajaratnamDeveloper Services ndash Adoptions Engineer Mobile 07747 640477 Landline 0203 577 9811 sivarajaratnamthameswatercouk
Clearwater Court Vastern Road Reading RG1 8DB Find us online at developersthameswatercouk
From John Barrell ltJohnBarrellmlmgroupcomgt Sent 13 August 2020 1159To Siva Rajaratnam ltSivaRajaratnamthameswatercoukgtCc James Noble ltJamesNoblemlmgroupcomgt Developer ServicesltdeveloperservicesthameswatercoukgtSubject 6601343 - RE RE DS6075526 - Pre-planning enquiry Car Park Vaughan Road Harrow HA13XDImportance High
This email contains a reference to Coronavirus or COVID-19 Please be aware ofcoronavirus-themed active phishing campaigns and use extra vigilance whenresponding or clicking
Good morning Siva I just tried to reach you on the phone numbers below without success I have however left a messageon your voicemail With reference to my email below (and your previous confirmation that a high level connection would
not be permitted) I would be grateful if you could confirm if Thames Water would permit a SWconnection via and internal external backdrop into either location option proposed We would also be grateful if you could confirm that Thames Water own the onsite catchpit which isnot shown on the 3 year old TW asset plan we have Many thanks for your ongoing assistance Kind regards
John BarrellSenior Engineer
D +44 1473 350114M +44 7736 058012T +44 1473 231100E JohnBarrellmlmgroupcomA MLM Group North Kiln Felaw Maltings 46 Felaw Street Ipswich Suffolk IP2 8PNW wwwmlmgroupcom
Buildings bull Infrastructure bull Compliance bull Environment
One to Watch Best Company 2020
Twitter bull LinkedIn bull Instagram bull YouTube
Emails are sent on behalf of the MLM company which is named in the relevant signed appointment or if noneexists in our fee proposal or (if MLM is acting as client) in our order Companies Act information for MLM Groupcompanies is available at wwwmlmgroupcomcompanies-act-information
For COVID-19 client service continuity update please click the link httpswwwmlmgroupcomnews-centrenewsclient-update-sweco-business-continuity
From John Barrell Sent 24 July 2020 2020To DEVELOPERSERVICESTHAMESWATERCOU ltDEVELOPERSERVICESTHAMESWATERCOUKgtsivarajaratnamthameswatercoukCc James Noble ltJamesNoblemlmgroupcomgtSubject RE RE DS6075526 - Pre-planning enquiry Car Park Vaughan Road Harrow HA1 3XD Dear Siva Many thanks for your response in relation to the above mentioned scheme confirm in principle thedevelopments FW and SW rates and connection Whilst liaising with the planning team who have suggest that a direct connect into Thames Watersexisting trunk sewer should be investigated With this in mind and so that I can respond to theplanning team could you please review connection Options 2 and 3 below and as identified on theattached sketch Please note that Option 1 is the current proposal that you have agreed to inprinciple
Option 2 (highlighted yellow) The developments surface water connection made directly into theexisting trunk sewer via manhole TW REF9006 at high level Note that this chamber is 1366m deeptherefore a soffits level connection would not be viable Can you confirm that a high level connectioncascading into this manhole would be acceptable to Thames water Option 3 (highlight green) The developments surface water connection made directly at high levelinto the existing onsite catchpit located over the trunk sewer which has a connection through thebottom down to the trunk sewer below We believe this is owned by Thames Water Note that thecatchpit manhole is 811m deep therefore a soffits level connection would not be viable Can youconfirm that a high level connection cascading into this catchpit would be acceptable to Thameswater All three option suggested result in the developments SW discharge entering the trunk sewer at 5lsIf you could clarify if either option would be acceptable or perhaps suggest an alternative connectionmethod that would not involve digging 13m or 8m below existing ground Many thanks for the time you have spent on this inquiry Kind regards
John BarrellSenior Engineer
D +44 1473 350114M +44 7736 058012T +44 1473 231100E JohnBarrellmlmgroupcomA MLM Group North Kiln Felaw Maltings 46 Felaw Street Ipswich Suffolk IP2 8PNW wwwmlmgroupcom
Buildings bull Infrastructure bull Compliance bull Environment
One to Watch Best Company 2020
Twitter bull LinkedIn bull Instagram bull YouTube
Emails are sent on behalf of the MLM company which is named in the relevant signed appointment or if noneexists in our fee proposal or (if MLM is acting as client) in our order Companies Act information for MLM Groupcompanies is available at wwwmlmgroupcomcompanies-act-information
For COVID-19 client service continuity update please click the link httpswwwmlmgroupcomnews-centrenewsclient-update-sweco-business-continuity
From DEVELOPERSERVICESTHAMESWATERCOU[mailtoDEVELOPERSERVICESTHAMESWATERCOUK] Sent 24 July 2020 0914To James Noble ltJamesNoblemlmgroupcomgt sivarajaratnamthameswatercoukCc John Barrell ltJohnBarrellmlmgroupcomgtSubject RE RE DS6075526 - Pre-planning enquiry Car Park Vaughan Road Harrow HA1 3XD
Hi James
Thank you for providing the additional information Please find attached Thames Waters responseletter to your Pre-planning enquiry confirming there is sufficient capacity
Regards
Siva Rajaratnam
Developer Services ndash Adoptions Engineer
Mobile 07747 640477 Landline 0203 577 9811
sivarajaratnamthameswatercouk
Clearwater Court Vastern Road Reading RG1 8DB
Find us online at developersthameswatercouk
From James Noble ltJamesNoblemlmgroupcomgtTo sivarajaratnamthameswatercouk
CCJohn BarrellltJohnBarrellmlmgroupcomgtDEVELOPERSERVICESTHAMESWATERCOUltDEVELOPERSERVICESTHAMESWATERCOUKgt
Sent 170720 165138Subject RE DS6075526 - Pre-planning enquiry Car Park Vaughan Road Harrow HA1 3XD
This email contains a reference to Coronavirus or COVID-19Please be aware of coronavirus-themed active phishingcampaigns and use extra vigilance when responding or clicking
ltcolor=salmongt
Hi Siva Please find point by point response to the question you have raised below in blue Hopefully the below is clear but should you have any questions or require any further informationplease do not hesitate to call Kind regards
James NobleHND BRE AcademySenior Technician
D +44 1473 350184
T +44 1473 231100E JamesNoblemlmgroupcomA MLM Group North Kiln Felaw Maltings 46 Felaw Street Ipswich Suffolk IP2 8PNW wwwmlmgroupcom
Buildings bull Infrastructure bull Compliance bull Environment
One to Watch Best Company 2020
Twitter bull LinkedIn bull Instagram bull YouTube
Emails are sent on behalf of the MLM company which is named in the relevant signed appointment or if noneexists in our fee proposal or (if MLM is acting as client) in our order Companies Act information for MLM Groupcompanies is available at wwwmlmgroupcomcompanies-act-information
For COVID-19 client service continuity update please click the linkhttpswwwmlmgroupcomnews-centrenewsclient-update-sweco-business-continuity
From DEVELOPERSERVICESTHAMESWATERCOU[mailtoDEVELOPERSERVICESTHAMESWATERCOUK] Sent 15 July 2020 1604To James Noble ltJamesNoblemlmgroupcomgtCc John Barrell ltJohnBarrellmlmgroupcomgt sivarajaratnamthameswatercoukSubject RE DS6075526 - Pre-planning enquiry Car Park Vaughan Road Harrow HA1 3XD
Dear James
I have received a response from the Asset Planner and they require further information in regardto your surface water drainage strategy Can you provide the following
1 ndash The existing surface water flow rates for the range of storms (11 110 130 and 1100)Existing surface water flow rates as follows based on the existing car park ndash 100 impermeablerunoff
11 Year = 205ls
110 Year = 414ls
130 Year = 507ls
1100 = 585ls
2 ndash The proposed surface water flow rates for the range of storms (11 110 130 and 1100) Theproposed scheme requires a pumped surface water discharge therefore the maximum flow rate foreach storm event will be restricted to the maximum allowable pump rate Below ground storagewill provided onsite to attenuate the flows generated for each storm event up to and including the1 in 100 year plus an allowance for climate change
11 Year = 5ls
110 Year = 5ls
130 Year = 5ls
1100 Year = 5ls
3 ndash The Greenfield runoff rates for the site The greenfield runoff rate for the site isapproximately 062ls Due to various site constraints a surface water pump is required is per ourpreviously issued drainage strategy drawing and letter The greenfield rate of 062ls is notachievable or practical for a pumped outfall
4 ndash Can you provide further details of how the surface water drainage strategy for thisdevelopment follows policy 513 of the London Plan The hierarchy lists the preference forsurface water disposal as follows
lt[if supportLists]gtlt[endif]gtStore Rainwater for later use ndash The scheme proposes to use aboth green blue roof attenuation to store water at source and to increase biodiversity Therewill also be a small element of rainwater recycling for irrigation purposeslt[if supportLists]gtlt[endif]gtUse infiltration techniques such as porous surfaces in non-clayareas The site lies within an area of London clay therefore the use of infiltration techniques is notpossible Please see attached image from the British Geological Survey (BGS) website highlightingthe strata below and surrounding the sitelt[if supportLists]gtlt[endif]gtAttenuate rainwater in ponds or open water features for gradualrelease Due to the restricted nature of the site ponds or other open water features are notpossible for the storage and gradual release of water lt[if supportLists]gtlt[endif]gtDischarge rainwater direct to a watercourse The nearest watercourse is Wealdstone Brook approximately 3400m to the east of the site therefore outfall to awatercourse would not be practicallt[if supportLists]gtlt[endif]gtDischarge rainwater direct to a surface water sewerdrain It isproposed to discharge the surface water at a restricted pumped 5ls rate utilising the existing carpark on site surface water laterallt[if supportLists]gtlt[endif]gtDischarge rainwater to the combined sewer The surface wateris not proposed to discharge into a combine sewer
6 lt[if supportLists]gtlt[endif]gtndash Can you provide a plan showing the existing surfacewater drainage layout Please find attached plan of existing surface water sewers
6 ndash Can you confirm whether it is possible to restrict the surface water discharge rate furtherReducing the pumped discharge rate is subject achieving a practical pump minimum and balanceof health and safety risks and maintenance
The proposed pump rate of 50ls achieves the correct balance and is significant reduction on thesites current unrestricted surface water discharge rates as stated above
Please note a previous scheme for this site was proposed in 2018 This scheme gained LLFAapproval and Thames Water S106 technical approval for a 50ls pumped surface water dischargerate prior to the scheme being put on hold Previous application approval Thames Waterreference number = DS6045627
The revised scheme remains largely unchanged in terms of the site layout site constraints etc andtherefore the same previously approved drainage strategy is proposed
7 ndash Can you confirm why a gravity discharge is not possible The depth of the existing surfacewater lateral serving the existing carpark gullies is approximately only 300mm deep at the siteboundary Due to the shallow outfall invert the size of the site and the required attenuation due tothe flow rate restriction a gravity discharge is not achievable
Should you have any further queries please feel free to contact me
Regards
Siva Rajaratnam
Developer Services ndash Adoptions Engineer
Mobile 07747 640477 Landline 0203 577 9811
sivarajaratnamthameswatercouk
Clearwater Court Vastern Road Reading RG1 8DB
Find us online at developersthameswatercouk
Original Text
From DEVELOPERSERVICESTHAMESWATERCOUltDEVELOPERSERVICESTHAMESWATERCOUKgt
To jamesnoblemlmgroupcom
CC John Barrell ltJohnBarrellmlmgroupcomgtsivarajaratnamthameswatercoukltsivarajaratnamthameswatercoukgt
Sent 080720 164037Subject DS6075526 - Pre-planning enquiry Car Park Vaughan Road Harrow HA1 3XD
Dear James
Thank you for your Pre-planning enquiry I have consulted with the Asset Planner to confirmwhether there is sufficient capacity and I should have a response in a weekrsquos time
Should you have any further queries please feel free to contact me
Regards
Siva Rajaratnam
Developer Services ndash Adoptions Engineer
Mobile 07747 640477 Landline 0203 577 9811
sivarajaratnamthameswatercouk
Clearwater Court Vastern Road Reading RG1 8DB
Find us online at developersthameswatercouk
From James Noble ltJamesNoblemlmgroupcomgtTo developerservicesthameswatercou ltdeveloperservicesthameswatercoukgtCC John Barrell ltJohnBarrellmlmgroupcomgt
Sent 030720 175106Subject 6601343 - Vaughan Road Pre Planning Enquiry
This email contains a reference to Coronavirus or COVID-19Please be aware of coronavirus-themed active phishingcampaigns and use extra vigilance when responding or clicking
ltcolor=salmongt
Dear Developer services Please find attached pre planning application form and associated plans as required for proposeddevelopment - Vaughan Road Hotel Should you require any further information please do not hesitate to call Kind regards
James NobleHND BRE AcademySenior Technician
D +44 1473 350184T +44 1473 231100E JamesNoblemlmgroupcomA MLM Group North Kiln Felaw Maltings 46 Felaw Street Ipswich Suffolk IP2 8PNW wwwmlmgroupcom
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The information contained in this communication from the sender is confidential It is intended solely for use bythe recipient and others authorised to receive it If you are not the recipient you are hereby notified that anydisclosure copying distribution or taking action in relation of the contents of this information is strictlyprohibited and may be unlawful
Vaughan Road Aparthotel Planning Stage Drainage Strategy copy MLM Consulting Engineers Limited
mlmipscomworkTier2MLM66010006601343MLMREPDrainage Report 9
Appendix B - Thames Water Pre-planning Enquiry
Thames Water Utilities Limited ndash Registered Office Clearwater Court Vastern Road Reading RG1 8DB Company number 02366661 VAT registration no GB 537-4569-15
Mr James Noble MLM Group North Kiln Felaw Maltings 46 Felaw Street Ipwich Suffolk DS6075526 IP2 8PN
24 July 2020
Pre-planning enquiry Confirmation of sufficient capacity
Dear Mr Noble
Thank you for providing information on your development
Carpark at Vaughan Road Harrow Middlesex HA1 3XD
Existing Carpark
Proposed 146 bedroom hotel and restaurant (80 person) Foul water discharging by
pump (82ls) via a new connection to the foul water sewer in Vaughan Road Surface
water to discharge by pump (5ls for all storm events) to the surface water manhole 901B
via an existing connection
We have completed the assessment of the foul water flows and surface water run-off based on the information submitted in your application with the purpose of assessing sewerage capacity within the existing Thames Water sewer network
Foul Water
If your proposals progress in line with the details yoursquove provided wersquore pleased to confirm that
there will be sufficient sewerage capacity in the adjacent foul water sewer network to serve your development This confirmation is valid for 12 months or for the life of any planning approval that this information is used to support to a maximum of three years
Yoursquoll need to keep us informed of any changes to your design ndash for example an increase
in the number or density of homes Such changes could mean there is no longer
sufficient capacity
Surface Water Please note that discharging surface water to the public sewer network should only be considered after all other methods of disposal have been investigated and proven to not be viable In accordance with the Building Act 2000 Clause H33 positive connection to a public sewer will only be consented when it can be demonstrated that the hierarchy of disposal methods have been examined and proven to be impracticable The disposal hierarchy being 1st Soakaways 2nd Watercourses 3rd Sewers
Only when it can be proven that soakage into the ground or a connection into an adjacent watercourse is not possible would we consider a restricted discharge into the public surface water sewer network
If the peak surface water run-off discharge is then restricted to Greenfield run-off ratesa maximum of 5ls as your drainage strategy indicates then we would have no objections to the proposals
Thames Water Planning team would ask to see why it is not practicable on the site to restrict to Greenfield run-off rates if they are consulted as part of any planning application
In considering your surface water needs we support the use of sustainable drainage on development sites Yoursquoll need to show the local authority andor lead local flood authority how yoursquove taken into account the surface water hierarchy that wersquove included
Please see the attached lsquoPlanning your wastewaterrsquo leaflet for additional information
What happens next Please make sure you submit your connection application giving us at least 21 daysrsquo notice of
the date you wish to make your new connections If yoursquove any further questions please contact me on 0203 577 9811
Yours sincerely
Siva Rajaratnam ndash Adoptions Engineer
Thames Water
Vaughan Road Aparthotel Planning Stage Drainage Strategy copy MLM Consulting Engineers Limited
mlmipscomworkTier2MLM66010006601343MLMREPDrainage Report 10
Appendix C - Flood Exceedance Routes
(6472)
(6477)
(6502)
(6537)
(6577)
FFL 6520
(6543)
(6554)
(6565)
(6600)
(6609)
FFL 6550
FFL 6494
113
(6512)
(6511)FFL 6494
(6511)(6519)(6520)
FFL 6550
FFL 6550
FFL 6535
FFL 6520
FFL 6520
VAUGHAN ROAD
CHILTERN RAILWAYS MAINLINE AND METROPOLITAN LINE
ONSITE THAMES WATER CATCHPIT MANHOLE
EXISTING HIGHWAY UNDERPASS RETAININGWALL TO BE REMOVED
DETAIL SUBJECT TO HARROW HIGHWAYSCONFIRMATION REQUIREMENTS REFER TOTHE LANDSCAPE ARCHITECT INFORMATIONFOR FURTHER DETAILS OF THE OFFSITEPUBLIC REALM WORKS
SUBJECT TO THE FINAL ONSITE EXTERNALLEVELS AND OFFSITE SITE BOUNDARYTIE-IN LEVELS (BY OTHERS) LINEARDRAINAGE ALONG SITE BOUNDARY MAY BEREQUIRED TO PREVENT WATER FROMENTERING HIGHWAY LAND
HIGHWAYUNDERPASS
ALLOWANCE TO BE MADE TO RAISE THE FFL OF THEPLANT ROOMS THE PROPOSED OFFSITE SURFACEWATER CONNECTION POINT IS ASSUMED TO BE ONLYAPPROXIMATELY 03m DEEP THEREFORE ADEQUATEONSITE COVER TO THE PROPOSED HIGH LEVELOVERFLOW AND RISING MAIN WILL BE REQUIRED
REDUCTION IN BOUNDARY TIE-IN LEVELSSUBJECT TO CONFIRMATION OF OFFSITELEVELS WITHIN NETWORK RAIL LANDAND CONFIRMATION OF THE OFFSITESURFACE WATER CONNECTION POINTINVERT LEVEL
VAUGHAN ROAD
PROPOSED SURFACE FLOOD FLOW LOWPOINT SURFACE STORAGE
HIGH LEVEL OVERFLOW FROM SURFACE WATER PUMPDISCHARGING INTO SITE DEMARCATION CHAMBER TOPROVIDE ECXEEDANCE ROUTE INVERT OF THE HIGHLEVEL OVER FLOW TO ENSURE NO FLOODING OF THEBUILDING IN AN EXCCEDANCE EVENT
KEY
1xx PROPOSED GRADIENT
PROPOSED LEVEL
EXISTING LEVEL
6550
PROPOSED ONSITE EXTERNAL LEVELSSTRATEGY FLOOD FLOW ROUTE
(6550)
ARCHITECT LANDSCAPE ARCHITECTPROPOSED LEVEL amp GRADIENTGRADIENT
1xx6550
SITE BOUNDARY
ASSUMED HIGHWAY BOUNDARY
EXISTING ADOPTED HIGHWAY UNDERPASSFOOTWAY ACCESS RAMP
EXISTING ADOPTED HIGHWAY UNDERPASS STAIRS
EXISTING ADOPTED HIGHWAY VERGE WITHRETAINING WALL TO BE REMOVED SUBJECTTO HARROW HIGHWAY APPROVAL
ONSITE POROUS PAVING
SURFACE CREASE LINE
PROPOSED SURFACE WATEREXCEEDANCE ROUTES
P01 28072020 FIRST ISSUE JBN JJB JJB
P02 15092020 UPDATED TO INCLUDED THE LATESTEXTERNAL LAYOUT
JBN JJB JJB
3rd Floor Eldon House2 Eldon StreetLondon EC2M 7LSTel 020 7422 7800Website wwwmlmgroupcom
PROJECT
DRAWING TITLE
PURPOSE OF ISSUE
CLIENT
DRAWNDESIGN REVISIONSCALE
REV DATE REVISION MADE CHK
MLM REF
SUITABLE FOR
PRINT ACCURACY INDICATOR 50mm 100mm
100m
m50
mm
APP
STATUS
DRAWING REFERENCE
DANDI NINE LTD
VAUGHAN ROAD HOTEL
SURFACE WATER FLOOD FLOWAND EXCEEDANCE ROUTES
JBNJJB1100 A1 6601343
6601343MLM ZZ XX DR C 0005P02
PRELIMINARYCOMMENTINITIAL STATUS OR WIPS0
ALL WORKS OFFSITE WORKS BEYONDTHE REDLINE BOUNDARY BY OTHERSREFER TO THE LANDSCAPE ARCHITECTTO DETAIL OF THE OFFSITE PUBLICREALM WORKS
INFORMATION SHOWN IS INDICATIVEONLY AND IS SUBJECT TOCOORDINATE DETAILED DESIGN
NOTE DISCHARGE OF WATER OFF SITEWILL NOT BE PERMITTED WHERE POSSIBLEALL BOUNDARY LEVELS TO FALL ONSITEWHERE LEVELS DICTATE A FALL TOWARDSTHE PUBLIC HIGHWAY SUITABLEDRAINAGE (LINEAR DRAINS GULLIES ampKERB UPSTANDS ETC) WILL BE REQUIREDTO ENSURE SURFACE WATER IS NOTDISCHARGED ONTO THE PUBLIC HIGHWAY
1 THIS DRAWING IS TO BE READ IN CONJUNCTION WITH ALL RELEVANTENGINEERS ARCHITECTS AND SPECIALISTS DRAWINGS AND THESPECIFICATION
2 DO NOT SCALE FROM THIS DRAWING MANUALLY ORELECTRONICALLY WRITTEN PERMISSION MUST BE OBTAINED FROM MLMPRIOR TO SCALING ELECTRONICALLY OR USING THIS ELECTRONIC FILE
3 ALL WORK IS TO BE CARRIED OUT IN ACCORDANCE WITH THE RELEVANTBRITISH STANDARDS EUROPEAN NORMS CODES OF PRACTICE ANDBUILDING PRACTICE
4 PRIOR TO COMMENCEMENT OF THE WORKS THE CONTRACTOR SHALLDETERMINE THE LOCATION AND DEPTH OF EXISTING UTILITIES ACROSSTHE SITE LIAISE WITH ALL RELEVANT AUTHORITIES AND SERVICEPROVIDERS TO ENSURE THAT ALL PIPES CABLES AND OTHER PLANTISARE LOCATED PROTECTED AND WHERE NECESSARY DIVERTED
5 ALL DIMENSIONS ARE TO BE CHECKED BY THE CONTRACTOR PRIOR TOSTARTING THE WORKS ON SITE ANY DISCREPANCIES ARE TO BEREPORTED TO THE ENGINEER IMMEDIATELY
6 FOR CIVIL amp STRUCTURAL HEALTH amp SAFETY HAZARDS PLEASE REFER TODESIGNERS RISK ASSESSMENTS
7 IF YOU DO NOT UNDERSTAND FULLY ANY OF THE DETAILS SHOWN ONTHIS DRAWING CONTACT THE ENGINEER FOR CLARIFICATION
8 SURVEY INFORMATION TAKEN FROM G8633-1-R1 BY Laser SurveysDATED FEB 2017 AND DRAWING MJ REES 8722 BY MJ REES DATED APRIL2017
9 ARCHITECTURAL LAYOUT BASED ON DRAWING AKA_085_L100_ Level 00Floor Plan BY ADAM KHAN ARCHITECTS RECEIVED 26082020
10 EXTERNAL LAYOUT BASED ON ADAM amp SUTHERLAND DRAWINGSK_200828_06_312_02 AampS Proposed Levels Plan RECEIVED 28082020
11 THE CONTRACTOR SHALL OBTAIN PRIOR APPROVAL AND ALL NECESSARYLICENSES FROM THE THE HIGHWAY AUTHORITY BEFORE CARRYING OUTANY WORKS WITHIN THE EXISTING PUBLIC HIGHWAY
GENERAL NOTES