Integrated Water Management
Strategy
LOCAL PLAN
SUPPORTING STUDY
Draft for Regulation 18 Consultation
4 February 2016

Role of this study
This study has been produced to inform the draft Local Plan and should be read alongside otherrelevant studies, the draft Local Plan and the London Plan.

Study overview
Document title
Lead author
Purpose of the study

Stage of production
Key outputs

Key recommendations

Integrated Water Management Strategy
AECOM Global
Review of water infrastructure requirements for water demand,drainage, and flood risk (including OPDC’s Strategic Flood Risk
Assessment). Provides options and costs for integrated water
management.
Draft completed to inform Regulation 18 version of the Local Plan■■ A strategic assessment of current major redevelopment
proposals in the Counters Creek catchment highlighting key
opportunities and constraints.
■■ A strategic level flood risk assessment of the OPDC area.
■■ Assessment of baseline water demands, sewage production
and rainfall runoff for the development using the OAPF
information. Estimates for water demand and sewage andrainfall runoff production for a range of scenarios.
■■ Review of the capacity and performance of the existing
infrastructure. Information on infrastructure capacity andperformance highlighting when and where incapacity will leadto failures in levels of service.
■■ Assessment of individual building and communal scale
opportunities to sustainably manage potable water, sewage,
drainage and flood risk needs of the OPDC area using an
integrated approach. Assessment includes the options andoptions appraisal process; and the preferred strategy.
■■ An assessment of the ‘smart’ technology opportunities toenable scalable, robust and long-term sustainable water
management.
■■ Report detailing costs, implementation mechanisms andtimings for the preferred strategy and how the costs■■ For water management, a range of options are identified atboth strategic and site level for managing surface and storm
water run-off, and for disposing of waste water. These include
the need for a centralised sustainable drainage system, in
addition to site specific measures.
■■ For potable water, recommendations include the need for
rainwater harvesting and greywater re-use to achieve as close
as possible to neutrality in water use.

Relations to other studies

Next steps

Outputs to inform Utilities and Infrastructure Strategy
Outputs to inform and be informed by Green Infrastructure andOpen Space Strategy, Public Realm Strategy, and Old Oak Decentralised Energy Strategy.
The Strategy is in draft and is available for comment. Necessary
revisions will be made following public consultation before thedocument is finalised to sit alongside the Regulation 19 consultation on the Local Plan.
The document will inform the OPDC Infrastructure and Utilities
Strategy in 2016 in regard to options for delivering water infrastructure sustainably, cost-effectively and in an integrated way
with other infrastructure across the area.

Consultation questions
1. Do you agree with the recommendations of this supporting study? If not, please explain why.
2. Do you agree with the methods used in delivering the recommendations? If not, please set out
alternative approaches and why these should be used.
3. Are there any other elements which the supporting study should address? If yes, please define
these.

You can provide comments directly
through:
opdc.commonplace.isOld Oak Common and ParkRoyal
Integrated Water Management
Strategy

Draft ReportOld Oak Common and Park Royal

Integrated W ater Management Strategy

Quality information
Document name

Ref

Prepared for

Prepared by

Date

Reviewed by

Final Draft

Draft 2

OPDC

AECOM

January 2016

Michael Henderson
Galo Pinto
Carl Pelling

Revision date

Details

Name

Position

Revision history
Revision

This document has been prepared by AECOM Limited for the sole use of our client (the “Client”) and in accordance with generally accepted consultancy
principles, the budget for fees and the terms of reference agreed between AECOM Limited and the Client. Any information provided by third parties andreferred to herein has not been checked or verified by AECOM Limited, unless otherwise expressly stated in the document. No third party may rely upon thisdocument without the prior and express written agreement of AECOM Limited.

AECOM

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Old Oak Common and Park Royal

Integrated W ater Management Strategy

Executive Summary
The growth proposed for the Old Oak Common and Park Royal Opportunity Area is of such considerable scalethat it will require a step change in the provision of water supply, wastewater treatment and water infrastructure.
The extent of water challenges facing the Opportunity Area cannot be overemphasised. They include an acutelack of capacity within the drainage infrastructure, areas of surface water and sewer flooding risk locally and inneighbouring areas, and an increasing deficit of available water to meet demand in an over growing city.
An Integrated Water Management Strategy has been developed to set a framework for how water and wastewater
should be managed within the Opportunity Area to move towards a more sustainable new development. The
Strategy has been formed around several core objectives:
To ensure that the rate of wastewater and surface water discharge to the sewer is no greater than it isfrom the site usage of the Opportunity Area in the present day;To minimise the volume of water is discharged to the sewer;
To manage surface water runoff to a position that would match runoff from the site if it were undeveloped(greenfield);
To reduce as far as possible the demand for centralised water supply by re-using water resources andwastewater resource on site;
To deliver these objectives in the most sustainable way bearing in mind the need to ensure the overall
viability of the site.
A strategic review of flood risk sources and water infrastructure coverage has been undertaken to determine thebaseline constraints and conditions. Further, a water balance exercise was undertaken to determine the water
available on the site and the extent of change in water uses and wastewater and surface water generated as aresult of the development.
Within the context of these constraints and the water balance, several water management measures have been
considered and developed, and this process included input from a range of stakeholders with an influence on how
water will be managed and used in the development. The measures were assessed against a range of criteria,
covering deliverability as well as sustainability, to arrive at baskets of measures which can meet the core
objectives but with a range of different benefits and disbenefits.
The baskets of measures have been developed as ‘strategy options’ and six of these options have been defined inorder to ensure flexibility of approach as the masterplanning and detailed infrastructure assessment work
progresses for the Opportunity Area.
Of the six potential Strategy options proposed, a preferred solution has been identified and recommendations for
how this strategy could be taken forward are presented within this document, including strategy delivery and next
technical steps. The output from the Strategy recommendations has been used to draft the water policy elements
and water management approach included within the draft Local Plan.
Views are now sought on this consultation version of the Integrated Water Management Strategy, as part of thewider Local Plan consultation, from a range of interested parties to help shape the Strategy next steps.

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Contents
Executive Summary ................................................................................................................................................. ii
1

Strategy Background ..................................................................................................................... 1
1.1

Introduction....................................................................................................................................... 1

1.2

Strategy Aims and Governance ....................................................................................................... 1

2

Site Context and Proposals........................................................................................................... 3
2.2

Existing Site...................................................................................................................................... 4

2.3

Proposed Development .................................................................................................................... 6

3

Water Challenges ........................................................................................................................... 9
3.1

Drainage and Wastewater ................................................................................................................ 9

3.2

Water Resources.............................................................................................................................. 9

3.3

Infrastructure Coverage.................................................................................................................. 10

3.4

Flood Risk ...................................................................................................................................... 11

3.5

Water Challenges Summary .......................................................................................................... 12

4

Opportunity Area Water Cycle .................................................................................................... 13
4.1

Annual Water Flows ....................................................................................................................... 13

4.2

Peak Instantaneous Water Flows................................................................................................... 21

5

Water Management Measures ..................................................................................................... 24
5.2

Performance Criteria ...................................................................................................................... 24

5.3

Demand Management .................................................................................................................... 27

5.4

Green Roofs ................................................................................................................................... 30

5.5

Roof Water Recycling..................................................................................................................... 32

5.6

Grey Water Recycling .................................................................................................................... 34

5.7

Green Source Control Measures.................................................................................................... 36

5.8

Below Ground Storage ................................................................................................................... 39

5.9

Strategic SuDS Networks ............................................................................................................... 41

5.10

Waterway Storage and Discharge.................................................................................................. 43

5.11

Downstream Stormwater Retention Ponds or Wetlands ................................................................ 45

5.12

Stormwater Recycling .................................................................................................................... 47

5.13

Wastewater Recycling .................................................................................................................... 49

5.14

Expansion of the Counters Creek Flood Alleviation Scheme ......................................................... 53

6

7

Water Management Options ........................................................................................................ 55
6.1

Strategy Formulation ...................................................................................................................... 55

6.2

Multi-Criteria Analysis..................................................................................................................... 57

6.3

Stormwater Management Options.................................................................................................. 57

6.4

Recycling Options .......................................................................................................................... 62

6.5

Scenario Comparison ..................................................................................................................... 65
Strategy Overview ........................................................................................................................ 71

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Integrated W ater Management Strategy

IWM Strategy Delivery.................................................................................................................. 72
8.2

Key Delivery Considerations .......................................................................................................... 72

8.3

Potential delivery approaches ........................................................................................................ 74

9Conclusions and Recommendations ......................................................................................... 76
9.2

The Preferred Strategy ................................................................................................................... 76

9.3

Next Steps for Strategy Development ............................................................................................ 77

Old Oak Common and Park Royal

Integrated W ater Management Strategy

1Strategy Background

1.1

Introduction

1.1.1.1

At the proposed intersection between Cross Rail and HS2, Old Oak Common and Park Royal has been
identified as a key Opportunity Area for growth. This thriving new centre will make a major contribution
to meeting London’s residential and employment needs by providing approximately 25,500 new homes
and an indicative 65,000 new jobs over the next 20 to 30 years. This scale of growth will require a stepchange in utilities infrastructure, and in particular the water infrastructure, needed to ensure thedevelopment is delivered in a more sustainable way. Given the age and limited capacity of the existingwater infrastructure in the area, there are particular challenges to ensuring a more sustainable supply ofwater, as well as more sustainable system for the management of wastewater, storm water and floodrisk.

1.1.1.2

As well as representing a challenge, the scale of development proposed at Old Oak and Park Royal
present a rare opportunity to deliver truly integrated water management; capitalising on the potential toreuse water before it is discharged, and using the principles of water sensitive urban design (WSUD) toshape the fabric of the new development. The development of this Integrated Water Management
Strategy (‘the Strategy’) for Old Oak and Park Royal is therefore vital to set a framework for the deliveryof this step change in water infrastructure provision. Identifying opportunities early in the development
processes will help to ensure that the strategic infrastructure required to deliver more sustainable water
management is appropriately captured in the master plan and ensure that planning policy is developed
to enable the delivery in an efficient, coordinated and cost effective way. The Strategy is therefore an
important evidence base supporting the development of the Local Plan for the Opportunity Area and theconclusions and recommendations made within this Strategy have been used to develop planning policy
within the emerging Local Plan.

1.2

Strategy Aims and Governance1.2.1.1

This strategy and its objectives have been developed in collaboration and consultation with key partners
integral to the delivery and management of water infrastructure for Old Oak and Park Royal. A steeringgroup has overseen the Strategy development made up of:
the Greater London Authority (GLA);
the Old Oak and Park Royal Development Corporation (OPDC);
Thames Water Utilities Ltd;the Environment Agency;
the London Borough of Brent;
the London Borough of Hammersmith and Fulham (LBHF);
the London Borough of Ealing; andthe London Borough Kensington and Chelsea.

1.2.1.2

The main high level aims of the Strategy as identified in consultation with the Steering Group are to:
Embed sustainable water management principles into the Old Oak Common and Park Royal
regeneration masterplan;Set the framework for delivering an exemplary, integrated approach to managing water supply,
waste water and flood risk to guide future infrastructure delivery; andSet a framework which demonstrates workable solutions to the capacity limitations and water
challenges facing the development.

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1.2.1.3

In delivering these aims, a series of water management and sustainability objectives have been set by
the Steering Group. These objectives are included within Section 5 of this Strategy document.

1.2.1.4

In addition to the steering group governance, a wider stakeholder workshop was held during theStrategy development to ensure it captured and considered all potential water management options andthat the approach to assessing options was appropriate.

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2Site Context and Proposals

2.1.1.1

Old Oak Common and Park Royal are located at the meeting point of two major strategic growthcorridors: the London- Luton - Bedford Growth Corridor and the Western Wedge. The area’s wider
context points to the true potential of the area positioned half way between Heathrow and Central
London.

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Sources: Esri, HERE, DeLorme, USGS, Intermap, increment P Corp.,
NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand),
MapmyIndia, © OpenStreetMap contributors, and the GIS User
Community

LegendOPDC Area
Watercourses

Ü

0

250

500

1,000
MetersFigure 2-1: Location context of the Old Oak and Park Royal development area

2.1.1.2

The area provides valuable development capacity to accommodate London’s rapidly expanding
population and to develop a range of uses, including the higher education sector, creative industries,
entertainment and retail, which could help London maintain its world city status.

2.1.1.3

The HS2/Crossrail interchange at Old Oak Common will fundamentally change the development
potential of the area and the role it plays in its wider London context. The new interchange could
become a destination in itself and the heart of a new piece of city that could benefit from a canal side
setting and proximity to one of the largest park spaces in London at Wormwood Scrubs. This could inturn benefit the core of the Park Royal industrial estate which will be retained and developed to build on
its role as London’s premier industrial location of the national economy.

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2.2

Existing Site

2.2.1

Land Use

2.2.1.1

Although small pockets of residential property are situated within the Opportunity Areas, Park Royal and
Old Oak Common are dominated by industrial and commercial land uses. Park Royal in particular isdesignated as a Strategic Industrial Location (SIL), housing approximately 2,000 businesses with 30,000
employees.

2.2.1.2

Park Royal and Old Oak Common are well connected with transport links, with the Great Western MainLine (GWML), West Coast Main Line (WCML), London Overground (LO) and London Underground (LU)
lines, Central Line and Bakerloo Line all pass through the Opportunity Area. This transport network will
be further expanded with the planned development of the HS2 lines and station as well as Crossrail
lines.

2.2.1.3

In addition to the developed areas, Wormwood Scrubs makes up a significant proportion of the Old Oak
area providing valuable amenity and ecological space.

2.2.2

Water Environment

2.2.2.1 Surface Water
2.2.2.2

The River Brent is the only significant natural watercourse located within the Opportunity Area. The
river forms the north-west boundary of the Park Royal. The Grand Union Canal (Paddington Branch)runs through the centre of the Opportunity Area and is a key feature influencing topography andmovement of surface water (see Figure 2-1).

2.2.2.3

The general topography within the Opportunity Areas slopes from north to south. The local topography
results in three natural hydrological drainage catchments as shown in Figure 2-2. The majority of Park
Royal naturally drains in a north-westerly direction towards the River Brent. The southern section ofPark Royal drains to the south into what was known as the Stamford Brook (now culverted andincorporated into the Counters Creek catchment). The Old Oak section of the Opportunity Area drains
into the previously open watercourse the Counters Creek (also culverted and incorporated into thesewer system).

2.2.2.4

The natural topography and how the area drains has been artificially modified by infrastructuredevelopment (e.g. excavation of the siding for the Great Western Main Line (GWML) and the creation of
the Grand Union Canal) and reconfiguration of the sewer system where previously open watercourses
have been incorporated into the combined sewer system (Stamford Brook and Counters Creek).

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LegendOPDC Area
Watercourses
Topographic_Catchment_region
97m 1m LiDAR Digital Terrain Model (DTM)
79m
61m
42m
25m
6m

Figure 2-2: Surface topography and natural hydrological catchments across the Opportunity Areas

2.2.2.5 Geology and Groundwater
2.2.2.6

5

The Opportunity Area lies almost solely on a bedrock of London Clay, with limited superficial deposits of
Alluvium and Gravel in the north-west corner of the development area boundary associated with theRiver Brent, as shown in Figure 2-3. London Clay is a low permeability geological stratum.

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LegendSuperficial Deposits
ALLUVIUMLYNCH HILL GRAVEL MEMBERTAPLOW GRAVEL FORMATION

Bedrock Geology
CLAYGATE MEMBERLONDON CLAY FORMATION

Figure 2-3: Bedrock and superficial geology

2.3

Proposed Development

2.3.1

Old Oak Common

2.3.1.1

Major new development will be focused at Old Oak Common, which is proposed to be a high density
mixed-use development accommodating approximately 25,500 new homes and an indicative 65,000
new jobs. An indicative layout of the current master planning proposals for this part of the Opportunity
Area is shown in Figure 2-4.

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LegendGreen Space
Open Space
Plot Locations

Figure 2-4 - Old Oak indicative masterplan, Old Oak and park Royal OAPF (2015)

2.3.2

Park Royal

2.3.2.1

As part of the regeneration, Park Royal is proposed to remain as a SIL, with the majority of existing
businesses retained. In addition, the Park Royal development will provide approximately 10,000 new
employment opportunities. The primary area for this development will be at the site of the HS2
construction sites following their release upon completion of the project. The current preferred option isfor site re-development as an industrial business park, incorporating 125,750 m2 of new floor space.

2.3.2.2

In the centre of Park Royal, the existing retail area is planned to be enhanced and expanded to become
a local hub for residents and businesses. In addition, 1,500 new homes will be constructed to the westof Park Royal and additional employment opportunities created through regeneration and densificationof the existing land use.

2.3.3

Wider Development Proposals

2.3.3.1

In addition to the growth proposed at Park Royal and Old Oak, several other Opportunity Areas areproposed within west, and north-west London which will share key parts of the same limited capacity
water infrastructure. The Opportunity Area Planning Frameworks (OAPF) for each area have beenreviewed and compared to growth within Old Oak and Park Royal to set the context of additional water
demand and wastewater discharge volumes.

2.3.3.2

The OAPFs provide large scale redevelopment zones, with these areas likely to result in extensive
increases in water demand and wastewater discharge. Table 2-1 summarises the growth projections foreach of the OAPFs likely to share the same drainage and water supply infrastructure as Park Royal and
Old Oak.

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Table 2-1 Opportunity Area Planning Frameworks within north-west London

OAPF

Wembley

Kensal Canalside(Gasworks)

2.3.3.3

1

8

1Overview
2,500 new homes
15,000 jobs
30,000 m2 of retail
New residential district, expanded and redeveloped industrial sites andbusiness parks, civic centre, expanded town centre with Wembley
Stadium at the centre
3,500 new homes
2,000 new jobs
Mixed use development, crossrail station, residential, commercial,
workshops, small offices and studios, creating a creative and cultural hub

White City

6,000 new jobs
10,000 new homes
Mixed use – creative, academic, technology and small businesses, andinvestment in the metropolitan town centre

Earls Court and West
Kensington

7,500 new homes
9,500 new jobs
New urban quarter with residential and mixed use development,
replacing the old Earls Court Exhibition centre

Water demand and wastewater discharge calculations for the wider Opportunity Areas are presented inAppendix A. The growth across all Opportunity Areas sharing the same drainage and water supply
infrastructure is estimated to result in an increase in water demand of over 13 million litres per day and acommensurate increase in wastewater generation. Growth within Old Oak and Park Royal is expected
to contribute approximately 56% of the calculated increase in residential demand and discharge, andbetween 70% and 80% of the employment based demand and discharge.

Source: http://www.futureoflondon.org.uk/2015/02/13/londons-opportunity-areas/

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3

Water Challenges

3.1

Drainage and Wastewater

3.1.1.1

The pressure on the drainage infrastructure within this region of London is particularly prominent. All of
Old Oak and the majority of Park Royal are connected to the Counters Creek sewer sub-catchment of
the larger Beckton wastewater treatment catchment in north London. The remainder of Park Royaldrains to the Mogden wastewater treatment catchment to the west and south west of the site.

3.1.1.2

The Counters Creek catchment is a combined sewer system (transmitting both foul wastewater andsurface water) suffering from a lack of capacity which has resulted in sewer flooding of several
properties during rainfall events which would normally be expected to be accommodated by the sewer
system. The Counters Creek Storm Relief Sewer is proposed to reduce the frequency and extent ofsewer flooding to these properties in the catchment. The scheme is being designed to provide sewer
flood risk reduction to Thames Water’s current design standards and is designed to alleviate the issue
experienced at existing properties. It is not designed to accommodate additional foul flows or surface
water runoff from new areas of development within the catchment. The potential for the option ofincreasing the capacity of the scheme has been considered within this Strategy.

3.1.1.3

This highlights the limited capacity of the sewers within the catchment to accept additional foul flows andsurface water runoff from new development. In many cases there is no capacity for any increase incombined flow volumes during rainfall events without resulting in an unacceptable risk of flooding
downstream and adjacent development. Sewer flooding and surface water flooding are therefore two of
the key water management and flood risk concerns within this area of West London.
Inacknowledgement of this, Thames Water expect all development to reduce peak combined flow off theirsite as part of development so that it is no greater than pre-development discharges as a minimum.

3.1.1.4

Without mitigation, the proposed development at Old Oak and Park Royal would result in significant
increase in foul flows to the Counters Creek system. The potential impact of this would be exacerbatedby the unmitigated development of other identified Opportunity Areas within the drainage catchment
where capacity is severely limited (see Appendix A). This has the potential to result in significant floodrisk both within Old Oak and Park Royal as well as further downstream in the catchment if peak flows
are not managed from all potential development sites. This is a significant driver to ensure that thevolume and rate of wastewater discharge (both foul and surface water) is minimised as far as possible
within the development.

3.2

Water Resources

3.2.1.1

Water resources within London are (and will continue to be) subject to significant levels of stress. This
arises from several pressures including effects of climate change on raw resources, leakage,environmental protection and finite capacity within raw resources. With central planning projections
anticipating a 37 per cent increase in London’s population from 2011 to 2050, with a resident populationof 11.3 million by mid-century2 population growth and density will exacerbate these constraints.

3.2.1.2

Thames Water manages the water supply in London as a single ‘resource zone’; that is, all customers inthis zone share the same water resources and hence share the balance of supply and demand. Under
the current assessment of water resource availability for the next 25 years3, the London Water
Resource Zone is predicted to have an increasing deficit in available supply (demand is greater than
supply) growing from a deficit of 59.4 million litres a day currently to 415.9 million litres a day by 2040.
This highlights the significant pressure that London’s water resource base is under in order to continue
to supply water to meet the growth that is planned across the City.

2
3

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London 2050 plan
Thames Water - Resources Management Plan 2015 to 2040 (2015)
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3.2.1.3

Integrated W ater Management Strategy

Thames Water has developed a plan for removing this deficit through a combination of measures totackle leakage, manage (and reduce) water demand and implement new water supply schemes. The
plan to manage the deficit is reliant on significant demand reduction measures from existing property
and highlights the need for new developments to minimise water use and help identify innovative
solutions to delivering alternative supplies. This is reflected in water use and supply policies within the
London Plan:
Promoting the use of rainwater harvesting and using dual potable and grey water recycling systems,
where they are energy and cost-effective; andRequiring development to minimise the use of mains water by incorporating water saving measuresand equipment and designing residential development so that mains water consumption would meeta target of 105 litres or less per head per day.

3.3

Infrastructure Coverage

3.3.1.1

GIS layers of the existing water, sewer and flood risk management infrastructure within the Opportunity
Area have been provided by key stakeholders, including Thames Water, the Canal and Rivers Trust andLead Local Flood Authorities. These datasets have been consolidated and a GIS infrastructure registerdeveloped. This is presented with in Appendix B. An excel version of the register has also beendeveloped and separately delivered as a part of this study. A summary of the existing water andwastewater infrastructure in the Opportunity Area is shown in Figure 3-1 and described in more detailbelow.
LegendConnection Main
Distribution Main
DrainsGravity Sewer
Pressure Main
Trunk Main
OPDC Region
Counters Creek sub-catchment
Mogden sub-catchments

Figure 3-1 – Existing water and wastewater infrastructure

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3.3.2

Water supply infrastructure

3.3.2.1

There are several trunk and distribution mains which supply water to properties throughout the area. In
general, Park Royal is supported by a dense network of underground pipework. However, there is lessexisting infrastructure within Old Oak Common, reflective of the low density nature of the current land
uses. In order to support the residential and commercial re-development currently proposed within thearea masterplan, the installation of comprehensive new water distribution infrastructure is likely to berequired.

3.3.3

Wastewater infrastructure

3.3.3.1

A small area of the north-western extent of Park Royal does not drain into the Counters Creek system.
This area forms a part of the Mogden sub-catchment with foul flows discharging to the Mogden
Wastewater Treatment Works (WwTW) and surface water from the Opportunity Area discharging to theRiver Brent

3.3.3.2

The coverage of the existing sewer infrastructure follows a similar pattern to the water supply
infrastructure, with relatively comprehensive coverage over Park Royal, and more sparse coverage over
Old Oak Common. Extensive new sewage and drainage infrastructure will be required to be delivered toservice the planned development in this area.

3.4

Flood Risk

3.4.1.1

A Strategic Level Flood Risk Assessment has been undertaken for Old Oak and Park Royal and isreported within Appendix C. Overall, flood risk to the Opportunity Area is relatively low for the majority offlood risk sources.

3.4.1.2

Only a small area of the site, to the north west of Park Royal is affected by fluvial flooding associatedwith the River Brent. Existing property is currently not located within this area of fluvial flood risk.

3.4.1.3

The Strategic Flood Risk Assessment demonstrates that the main source of flood risk directly affecting
the Opportunity Area is surface water flooding. This occurs as surface water ponding or overland flow
during high intensity rainfall events as rainwater is unable to drain into the sewer system. This flooding ispartly explained by the culverting, and subsequent adoption into the combined sewer system of thepreviously open watercourses. The rail and road infrastructure (often set at different levels) also creates
additional barriers to overland flow leading to areas of ponding.

3.4.1.4

Historical records also indicate that sewer flooding has occurred in a number of locations in theOpportunity Area; these are largely confined to the central areas of Park Royal.

3.4.1.5

A combination of fluvial flooding, surface water flood risk, drainage capacity and sewer flooding creates
localised areas of higher flood risk which need to be factored into the more detailed stages ofmasterplanning and subsequent planning applications for development plots. Management of excesswater within three areas also represents an opportunity for storage and re-use and provision ofdispersed flood storage to meet the water management aims derived for the Strategy (see section 6).
The higher flood risk areas are highlighted in Figure 3-2. Recommendations for managing andmitigating risk within these areas are discussed in the context of the various strategy options developed
and detailed in section 6 of this report. Full details are provided in Appendix C.

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LegendOPDC Area
Watercourses
Areas of high flood risk

Figure 3-2: Higher flood risk areas within Old Oak and Park Royal

3.5

Water Challenges Summary

3.5.1.1

The key water challenges shaping the Strategy and its core objectives can be summarised as:
An acute clack of capacity in the sewer network to accommodate additional foul flows without
increasing sewer flood risk downstream;
A growing deficit in available water supply to meet demand, exacerbated by climate change and a
rapidly increasing population in London;
A lack of suitable water supply and wastewater infrastructure to serve the quantum of growth
proposed across the Opportunity Area; andAreas of localised surface water flood risk which could be exacerbated by the scale and location of
proposed development if not sufficiently mitigated.

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4

Opportunity Area Water Cycle

4.1

Annual Water Flows

4.1.1.1

An annual water balance model has been developed for the Opportunity Areas to characterise andquantify the water cycle flows anticipated from the proposed development; this process has been
undertaken to determine the available water during average conditions over the course of a year as well
as determining the demand for water and generation of daily wastewater flows from new development.

4.1.1.2

For the purposes of this exercise, the OPDC development boundary was taken as the system boundary,
and all flows are estimated over an annual timescale. The model estimates flows by building up fromplot level, to simulate the area–wide balance between input and output of water. The two predominant
inflows to the urban cycle are:
The natural hydrological flows, which originate as rainfall and exit the system through groundwater
infiltration, evapotranspiration and urban runoff.
The centralised water supply, which is imported from outside the area boundary, and consumed ordischarged through the wastewater system.

4.1.1.3

Each of the flows included within the water balance is briefly described in Table 4-1 and a schematic of
how the flows contribute to the pre-development (existing condition) water cycle on site is presented in
Figure 4-1 below.
Table 4-1- Urban Water Cycle Flows

Flow

Definition

Rainfall

The volume of natural precipitation falling over the Opportunity Areas over an average
year.

Roof water

The quantity of rainwater which falls directly on rooftops within the Opportunity Areas. Thishas been split from storm water due to the differing water quality characteristics.

Stormwater

Runoff from the urban environment generated during rainfall events. This consists
predominately of runoff from impervious areas. This flow has been split from roof water
above; however, within the current system, both roof water and storm water are combinedand enter the drainage system.

Evapotranspiration

Water which is returned to the atmosphere through the processes of evaporation andtranspiration of vegetation, on permeable surfaces.

Infiltration

The proportion of rainwater which infiltrates through the soil, entering the groundwatertable.

Potable waterHigh quality water supplied for uses within the home, including water used for drinking anduse in the kitchen and bathroom. Within this analysis, potable water has been assumed asnecessary for all household uses except toilet flushing.

Water which is utilised for low-contact uses including irrigation and toilet flushing. In
general, this water is not required to be of the same quality as that used for potable uses.
Non-Potable Water Under the current scenario in the Opportunity Areas, water for all uses is supplied from thecentralised, potable system. In some circumstances, water for use in the laundry may also
be supplied by non-potable sources; however, this has not been included in the presented
analysis at this stage.
Grey Water

Wastewater generated from use in hand basins, baths and showers. Grey water generally
excludes water used in toilets, the kitchen or for cleaning use, which has a greater
concentration of contaminants.

Black Water

Wastewater generated from toilets, kitchen and laundry use. This has a higher
concentration of contaminants than grey water. Under the current scenario both black
water and grey water are combined and disposed to the drainage system.

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Figure 4-1: Conceptualisation of the pre-development water cycle

4.1.1.4

The objective of the water balance model is to provide a framework for addressing and prioritising water
concerns, and highlighting opportunities in terms of alternative supplies and potential mitigation
measures.

4.1.1.5

Figure 4-2 below illustrates of how the pre-development water cycle could theoretically be adapted toutilise the water cycle flows within the development to reduce demand and discharge.

Figure 4-2: Conceptualisation of a post-development water cycle scenario

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4.1.2

Water Balance Calculations

4.1.2.1

The water balance model was constructed to calculate the flows for baseline and the post development
condition using the best available information, and the outputs are presented in the following section.
Key assumptions used in formulating the water balance model are broadly described below.

4.1.2.2

In order to construct the model, Park Royal was divided into 5 separate sub-areas, and Old Oak
Common was divided into 8 separate sub-areas. All calculations were undertaken for individual landplots, building up the water balance for each sub-area, which subsequently fed into the overall wider sitebalance. The sub-area boundaries were developed based on physical infrastructure constraints (such as
major transport routes) but which would not necessarily have hydrological catchment splits within them.
The defined sub-areas are illustrated in Appendix D and Figure 4-3 below.

Figure 4-3: Defined sub areas for Old Oak Common (orange) and Park Royal (Purple)

4.1.2.3

15

Existing and proposed development areas, land use information and occupancy were assumed using
GIS layers and masterplan information provided by the OPDC. Rainfall data provided by theEnvironment Agency was used to generate average monthly rainfall depths; with runoff values
estimated using assumptions of the percentage of imperviousity and average hydraulic conveyance foreach land use. Water demands and wastewater generation was estimated using usage assumptions
based upon the Building Regulations 2010 Part G (2015 Edition) and British Standard BS8524:2001.
For both of these methodologies, the total water demand is based on assumptions on the use ofsanitary fittings. A range of efficiency scenarios were tested for the existing and new land uses;
however, it has been generally assumed that all new development will meet the maximum standards ofwater efficiency as specified in the London Plan.

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4.1.2.4

Estimates for evapotranspiration were obtained using the Penman-Monteith method, using monthly
climate inputs taken from local Bureau of Meteorology online records. A balancing value for infiltration
has also been used to complete the mass balance. These values have not been shown in the figures
below, due to the lower relative confidence and importance of these values to the water management
strategy. In considering these calculations, it should be noted that the master-planning for this area isstill at an early stage, and therefore only limited resolution is currently available regarding the anticipatedresidential, commercial and industrial developments. Additionally, only limited information on the current
water use within these Opportunity Areas could be sourced, particularly for the industrial site uses within
Park Royal. Therefore, whilst the model calculations provide a good indication of the relative magnitude
of various flows, they are based on several assumptions and simplifications in order to facilitate
strategic-level analysis and planning, and should not be regarded as assured volumes. More detailed
analysis will be required at a later stage in order to determine the exact volumes, and a detailed designof the required infrastructure will need to be undertaken.

4.1.3

Existing Scenario

4.1.3.1

The overall pre-development annual water balance for the Opportunity Areas is shown in Figure 4-4.
Given the highly urbanised nature of the catchment, the majority of rainfall is discharged to the drainage
system as urban rainfall runoff (including roof water and storm water). The relatively low density of theindustrial land uses across the current site results in a comparatively lower centralised water demandand sewage discharges, as compared to the runoff volumes.

4.1.4

Developed Scenario

4.1.4.1

The anticipated water balance for the developed site is illustrated in Figure 4-5 below. It may beobserved that the increase in population, as a result of the proposed high-density development will
result in a dramatic increase in the demand for water and subsequent generation of wastewater. Thereis also an increase in the proportion of urban runoff falling on rooftops. A minor increase in permeable
area is also anticipated as a result of the proposed development (associated with community space),
which is anticipated to slightly reduce the overall volume of urban runoff.

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Precipitation

Precipitation

4144 ML

4144 ML
Evapotranspiration

Evapotranspiration

Potable Demand

Potable DemandBlackwater

2803 ML1912 ML

Blackwater
317 ML425 ML
Non-Potable Demand

Grey Water

Non-Potable Demand

170 ML902 ML

Grey Water

232 ML1738 ML

Infiltration
Infiltration
Storm water
1899 ML

Roof water
927 ML

Figure 4-4: Pre-Development annual water balance for the Opportunity Areas

17

Roof water
Storm water
1099 ML
1728 ML

Figure 4-5: Post-Development annual water balance for the Opportunity Areas

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The magnitude of the anticipated increase in water demand and wastewater generation anticipated fromthe proposed development is further illustrated in Figure 4-6 below.

4000

3000

ML/year

Greywater
Generated
Blackwater
Generated

2000

Non-Potable
DemandPotable Demand
1000

0Demands

Discharges

Pre-Development

Demands

Discharges

Post Development

Figure 4-6: Anticipated increase in flow over the Opportunity Areas

4.1.4.3

As these figures illustrate, without intervention, the proposed development of the Opportunity Areas will
significantly increase demand on the regional water supply and wastewater assets. The capacity ofthese systems to cope with increased demand of this magnitude is limited, unless provisions are madeto mitigate this impact. However, in considering Figure 4-5, it can be seen that there are several
opportunities present to mitigate this impact. Significant streams of water are exiting the system,
discharged as waste streams which could be recycled to significantly reduce the overall external
demands and discharges.

4.1.5

Spatial distribution of annual flows

4.1.5.1

The water balance demonstrates the overall flows which are anticipated across the whole of the Old
Oak Common and Park Royal. However, these flows are not expected to be evenly distributed acrosseach of the areas in this pattern. Figure 4-7 illustrates this split of flows across the two areas. This
spatial split presents constraints in holistic management of the water resources across the two areas. In
particular, the majority of the high-density regeneration and new housing is expected in Old Oak
Common, while the largest surface areas, collecting rainfall runoff, are located in Park Royal.

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4.1.5.2

Additionally, the topography and existing water infrastructure influence the split of these flows. Surface
water runoff will tend to drain along the natural topographical catchments of the areas towards the local
waterways (some of which are incorporated into the sewer system). As a result, surface water flows
within Old Oak Common and the eastern extents of Park Royal, including the HS2 construction sites,
will tend to flow towards the south east and Wormwood Scrubs. The majority of Park Royal will tend todrain towards the River Brent.

4.1.5.3

The existing drainage infrastructure also artificially influences the split of these flows as shown. The vast
majority of collected surface water and sewage collected across the two areas is transported to theCounter’s Creek catchment, except the most western extents of Park Royal.

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Precipitation
Precipitation

2624ML

1520 ML
Evapotranspiration

Potable Demand

Evapotranspiration

Blackwater

432 ML

Potable DemandBlackwater

2371 ML1485 ML

Non-Potable Demand

Grey Water

642 ML1528 ML

450 ML

Non-Potable Demand

Grey Water

256 ML242 ML

Infiltration
Infiltration
Storm water
1098 ML

Roof water

Roof water

Storm water

860 ML630 ML298 ML

Figure 4-7 - Post-Development annual water balance for the Opportunity Areas

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4.2

Peak Instantaneous Water Flows

4.2.1.1

The distribution of the flows as described in the water balance are, in reality not uniform, fluctuating
significantly across different days and seasons. Variability in rainfall intensity and subsequent runoff
rates of surface water during heavy rainfall events is a key feature determining capacity in the sewer
system. In addition, peak wastewater flows from site occupation is also a key factor for sewer capacity
in dry weather conditions.

4.2.2

Water Supply and Wastewater Generation

4.2.2.1

Demand for water varies seasonally with the weather. In hot, dry weather, customer usage increases as
more water is used for outdoor uses including garden watering; while in cold weather leakage may risedue to an increased number of burst pipes..

4.2.2.2

Water demand also varies diurnally through the day, with the greatest demands occurring in the morningand evening, before and after the average working day. Thames Water modelling standards indicatethat a peak factor of 2.12 times the average flow should be used to represent peak residential sewage
flows, and 3 used for commercial flows (excluding infiltration)4. Considering the water balance presented
above, the estimated pre and post-development peak sewage flow for each area is indicated in Table
4-2.
Table 4-2- Estimated Increase in peak instantaneous sewer discharge (excluding infiltration)

Estimated Peak Sewer Discharges
Pre-Development

Post-Development

Old Oak Common

14 L/s

217 L/sPark Royal

43 L/s60 L/s

4.2.3

Rainfall, Runoff and Flooding

4.2.3.1

Rainfall varies seasonally across the year. On average, the majority falls in the autumn months ofOctober and November and the driest month is February, as shown in Figure 4-8. Although, there is alarge variance in the annual rainfall totals in London as well as the distribution of that rainfall across theyear. The rainfall occurring within a week or day also varies significantly, depending on the number andintensity of storm events. The volume of rainfall that falls in a short space of time, during significant
storm events has a significant impact on local drainage systems.

4

Peaking factors based on diurnal profile in CIRIA 177: Dry Weather Flows in Sewers (1998)

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7060

Rainfall (mm)

50
40
30
20
10
0

Figure 4-8: London average monthly rainfall (mm), as recorded between 1960 and 2015

4.2.3.2

Catchment urbanisation increases the impact of high intensity storm events, through removal of thenatural processes of infiltration, interception and evapotranspiration on naturally vegetated surfaces.
The resultant increase in the volume and speed of runoff causes significant and rapid loading to be
imposed on drainage systems during storm events. Current Thames Water standards provide for adesign drainage capacity of 1 in 30 years. However, drainage systems across London are of varying
age, with capacity for a highly variable range of storm events. In events exceeding the design capacity,
the system may be susceptible to surcharge and flooding. The majority of the Old Oak and Park Royalregions discharge to the Counters Creek Catchment, which is a combined sewer system. This system isknown to experience surface water and combined sewer flooding during storm events, with drainage
systems known to surcharge during storms as low as a 1 in 2 year event in some cases.

4.2.3.3

As such, a key aspect of the water management strategy for the Opportunity Areas will be in reducing
the surface water flows entering the combined sewer system, and providing attenuation to reduce thepeak flow rate at which this discharges. This discharge of surface water runoff must be decreased to alevel to offset the large increase in peak foul flows and hence allow the scale of development proposed
to be achieved. Currently, the minimum anticipated requirement is for developments to reduce site
runoff to Greenfield rates. This is the rate at which runoff would naturally discharge from an
undeveloped, highly permeable catchment. Currently, the proposed development area is predominately
urbanised, with very little green space (except Wormwood Scrubs), which means that this will be asignificant challenge. Increasing green, permeable areas within the catchment, and providing
attenuation storage and SuDS features will assist in achieving this.

4.2.3.4

Estimated pre-development (brownfield) and Greenfield runoff volumes for the 1 in 20 year storm eventare summarised in Table 4-3 below 5. This is understood to be a critical return period for consideration ofcurrent sewer capacity in this region.
Table 4-3 - Estimated pre-development and Greenfield Runoff Rates for the 1 in 20 year rainfall event

Estimated Runoff
Pre-Development

Greenfield

Old Oak Common

42,130 L/s

3,224 L/s

Park Royal

11,858 L/s

907 L/s5

Due to the size of the Opportunity Areas, the exact Greenfield runoff rate and required attenuation should be confirmed for individual
development plots during planning and design.

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4.2.3.5

Considering these flows in comparison to the peak sewage flows described in in Table 4-2, it may beobserved that the reduction in instantaneous surface water flow entering the combined drainage system
during storm events (through achieving Greenfield runoff rates), will be substantially in excess of the
anticipated increase in peak sewage flows. Therefore, effectively managing the surface water discharge
to achieve Greenfield rates will be essential to creating capacity within the sewer system.

4.2.3.6

In order to establish the attenuation volume required across the Opportunity Areas, anticipated runoff
rates for the critical 1 in 100 year climate change event have been calculated, and required volumes
determined. The volumes required for each sub-area (as illustrated in Figure 4-3) are summarised inTable 4-4 and Table 4-5 below.
Table 4-4- Attenuation storages required to achieve Greenfield Runoff Rates for each sub-area in Old Oak Common.

Old Oak Common Sub- Area

Attenuation Storage Required (m³)

1

1,937

2

1,552

3

7,897

4

1,839

5

2,627

6

9,610

7

6,139

8

1,851

Total

33,452

Table 4-5- Attenuation storages required to achieve Greenfield Runoff Rates for each sub-area in Park Royal.

23Park Royal Sub- Area

Attenuation Storage Required (m³)

1

4,319

2

56,713

3

15,752

4

6,664

5

113,073

6

40,417

Total

236,937

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5

Water Management Measures

5.1.1.1

This section highlights a number of water management measures that may be implemented to mitigate
the anticipated issues associated with the proposed development. The delivery (and performance) of
these measures will vary across the Opportunity Areas, due to the different challenges and water use
characteristics of each area. Within Old Oak Common and new build areas of Park Royal(predominately associated with the HS2 construction sites); a range of new infrastructure will be
required, providing significant opportunities for the simultaneous delivery of efficient, decentralised water
management and sustainable drainage systems as a part of the development. However, to achieve theobjectives across the remaining areas of Park Royal, there would need to be a retrofit or incremental
replacement of systems as the majority of land uses would remain. This area is also constrained by theexisting landscape, which will have significant cost and feasibility implications. Due to these factors, theapplicability of various measures has been considered separately for Old Oak Common and existingand new build areas of Park Royal.

5.1.1.2

Each of the described measures has been scoped using an assumed technology in each of these areas,
and their performance assessed across the key project objectives, and a range of wider deliverability
and sustainability criteria. These criteria have been discussed and refined in conjunction with key
stakeholders, in order to reflect the overall priorities for sustainable water management within thedevelopment, as broadly described below. In addition to assumed technology, a range of potential
innovations for some measures has been included to set initial detail on how each of the measures
could be implemented in the most sustainable and efficient way.

5.2

Performance Criteria

5.2.1.1 Key Water Management Objectives
5.2.1.2

Without mitigation, there are a number of water management issues foreseeable as a result of the
proposed development. Arising from these, the core objectives to be delivered through the integrated
water management strategy are:Providing attenuation and sustainable drainage features to achieve Greenfield quality and quantityof runoff - Providing sufficient attenuation to retain and reduce peak storm flows to the Greenfieldrunoff rate will reduce downstream flood risk, and provide additional sewer capacity to handle thesignificant increase in foul flows arising from the development during high intensity rainfall events.
The incorporation of SuDS features will additionally provide substantial water quality benefit.
Minimising demand on the centralised potable water supply as far as possible - increasing water
efficiency, managing demand and implementing fit for purpose water recycling will contribute to
mitigating the impact of the development on the critical supply levels across London.
Achieving a neutral discharge volume of combined wastewater- Both of the objectives describedabove will also contribute to minimising the volume of wastewater and surface water discharged,
mitigating the impact of the development on the already limited capacity of the existing drainage
infrastructure.

5.2.1.3

24

In assessing each measure against these objectives, the following scoring brackets have been used
(Table 5-1):

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Table 5-1: Scoring brackets used to assess each water management measure.

No Benefit

Low

MediumHigh

Potential Demand
Reduction

No reduction

Anticipated 0-9%
reduction

Anticipated 1019% reduction

Anticipated 20+%
reduction

Potential
Volumetric
Discharge
Reduction

No reduction

Anticipated 0-9%
reduction

Anticipated 1019% reduction

Anticipated 20+%
reduction

No contribution

Anticipated 0-9%
contribution torequired
attenuation

Anticipated 1019% contribution
to required
attenuation volume
required

Anticipated 20+%contribution torequired
attenuation volume
requiredPotential
Attenuation
for
Peak Storm Flow
Reduction

5.2.1.4 Deliverability Considerations
5.2.1.5

The feasibility of each measure relates the overall spatial and financial viability, and the anticipated easeof delivery. This has been considered in term of the below aspects:
Capital cost - Embedded within this criterion are feasibility considerations associated with
infrastructure requirements, construction cost and buildability constraints associated withinstallation in new build and retrofit environments.
Operational and maintenance requirements - Many of the options presented will have continuing
operational, maintenance or monitoring requirements, with an associated ongoing cost implication,and potential challenges in determining relevant responsibility and ownership.
Effective spatial requirements - Spatial requirements for many of the proposed options will present
a particular constraint to the feasibility of delivery, due to the required high density nature of the
proposed development.
Regulatory challenges and public acceptance - Existing regulation and legislation in the water
management area is complex and fragmented, with a lack of a comprehensive regulatory
framework, which may present operational and commercial risks. Additionally, the social effects ofinnovative solutions to sustainable water management need to be carefully considered.
Flexibility and scalability of delivery - The flexibility and scalability of measures relates to the ability
to react to the phasing of development delivery and the extent to which significant upfront costs are
incurred, or whether these may be spread over the re-development delivery, and how these can beclearly distributed amongst delivery partners.

5.2.1.6

To assess these deliverability aspects, each of the presented measures has been assessed in terms of
the estimated capital cost. This has been presented as a proportion of the estimated capital cost of theoverall development (or existing area), and assigned a cost bracket, as shown in Table 5-2 below.
Table 5-2 - Scoring brackets used to assess the capital cost of each water management measure

Low

Indicative Cost

25

Medium0-1% of estimated 1-2% of estimatedcapital construction construction costof area.
cost of areaHigh

Very High

2-3%
ofestimated
construction costof area3+% of estimatedconstruction costof area

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5.2.1.7

Integrated W ater Management Strategy

The remaining deliverability aspects have been assessed comparatively on a qualitative basis, using
quantitative indicators where possible. These have been assigned a score of None, Low, Medium orHigh.

5.2.1.8 Sustainability Considerations
5.2.1.9

Sustainability considerations are those related to broader long term sustainability and climate resilienceof the presented measures, as well as the extent to which they will deliver added benefits to the local
community. This has been considered in terms of the following aspects:
Carbon intensity - Each of the measures has an impact in terms of embedded carbon and ongoing
operational energy, associated with water supply, pumping and wastewater treatment. Green
infrastructure can additionally also contribute to removing greenhouse gasses from the atmosphereand sequestering them over the long term. Shading impacts can also result in reduced use of
mechanical cooling in the summertime and reduction in demand for water.
Blue-green space provided - Through high design and maintenance standards, the delivery of blueand green infrastructure can enhance the urban environment for the benefit of communities andbiodiversity. Particular benefit may be related to the following indicators:
Provision of habitat and biodiversity - when sufficiently planned, the delivery of diverse,high quality green spaces can provide valuable habitat to a range of flora and fauna,
including birds and invertebrates, while contributing to green corridors, allowing the
movement of species through urbanised spaces.
Recreation and community - provision of space for recreation and contribution tocommunity health, wellbeing and social cohesion. Water features can create a sense ofplace.
Microclimate adaptation - Reducing the impact of the urban heat island effect byproviding shading to protect against radiations, reducing local temperatures throughevapotranspiration and reducing heat absorbed and then released by surfaces.
Public realm - street greening and the delivery of effectively landscaped open spaces
can substantially improve the attractiveness and amenity of neighbourhoods.
Climate Resilience - Each of the various options presented differ as in the extent to which the option
is resilient in itself to the effects of climate change. Options which are dependent on rainfall to meetwater supply needs have a potentially lower resilience to climate change. More generally, increasing
the diversity of available water supply options can also contribute to increasing the overall resilienceof the system to climate change and other future disturbance, through increased flexibility andadaptability of supply options.
Surface water quality - Many SuDS components, particularly those incorporating natural, vegetative
or bio-retention processes, provide opportunities to improve water quality (meeting helping to meet
Water Framework Directive targets) and by treating diffuse water pollution through mechanisms
including sedimentation, filtration and biological degradation. These components can also reduce theamount of surface water reaching end watercourses (reducing erosion and pollution), and entering
sewers, adding to subsequent treatment requirements and possible CSO spills

5.2.1.10 These items have similarly been assigned a comparative qualitative score, based on the characteristicsof the presented measure, using quantitative indicators where possible. These have been assigned ascore of None, Low, Medium or High.

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5.3

Demand Management

5.3.1.1

Demand management strategies are generally
the first priority for sustainable water
management and should be considered
wherever possible. Demand management
conserves potable water supplies and reduces
the generation of wastewater. It is assumed in
new build areas that development will bedelivered to the latest guidance issued in the
London Plan, promoting the highest current
industry standards with respect to water
efficiency, through the incorporation of watersaving measures and equipment.

5.3.1.2

A range of new centralised water supply
infrastructure will be required in New Build
Areas, presenting an opportunity for the

Integrated W ater Management Strategy

installation of smart network technologies to
Figure 15 - Water efficient fittings
optimise operation. Such systems andtechnologies enable remote, real time monitoring of water usage, allowing rapid targeting of leakage,
operation issues and system inefficiencies. Additionally, customers can be provided with the informationand tools they need to make informed choices about their behaviours and water usage patterns.
Detailed monitoring of water quality parameters will also be invaluable in assessing the performance andfuture potential of water recycling systems.
5.3.1.3

Within retained existing areas of Park Royal, there are likely to be significant water savings to berealised through targeted water efficiency retrofits, process improvements and installation of modern
technologies. Given the expected age of many of the properties within Park Royal, it is likely thatmodern processes and new technologies may be able to result in substantial reductions at many
locations.

5.3.1.4

Community education, engagement and incentive schemes can also be utilised to improve consumer
behaviours and encourage the uptake of water conservation practices and technologies. A downside of
specifying water efficient fixtures and fittings is that they can be replaced for less efficient versions oncethe development is sold on and as such is not a guaranteed reduction in potable water demand.

5.3.1.5

Innovation in Demand Management

5.3.1.6

Driven by requirements such as those from BREEAM, water efficient fixtures and fittings are now largely
commonplace, such as 6/3.5 dual flush toilets and aerating showers that retain the feeling of power by
mixing pressured air with the water flow. The challenge to retain performance levels however remains,
and at present although it is technically possible to find fixtures and fittings to deliver a reduction in water
use to under 80lpd, the delivery of these additional efficiency savings from around the current 105120lpd risks the ability to maintain user satisfaction. Damaging user satisfaction in turn runs the risk thatthe water saving fixtures and fittings will be replaced by less efficient alternatives, undermining thesekey measures to reducing potable water demand.

5.3.1.7

Duravit Rimless – One of the main performance challenges of low flow toilets is to maintain hygienic
cleaning the power of the flush with limited water. To resolve this, the focus has been to increase thevelocity of horizontal flows as well the traditional vertical flush. The Duravit Rimless is an example of a
new range of toilets that create a cyclonic flow in order to clean the bowl.

5.3.1.8

Advances in sensing and monitoring are allowing more targeted and controlled use of water, as well as
raising awareness that supports behavioural responses that help reduce water demand.

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5.3.1.9

Integrated W ater Management Strategy

Smart Meters – Smart metering systems allow consumers to monitor water usage in real time, giving
greater control and transparency over water bills. Like a number of water companies, Thames Water
have embarked on a programme of installing water meters, and one would be expected that smart water
meters would be installed in new properties, delivering on average around 12% saving. Smart water
metering will also have benefits in detecting leaks, as above normal usage can be easily identified andflagged. The real innovation will come in combining water metering with other smart home and offices
systems to give complete utility control through one device.

5.3.1.10 Network Sensing – As with home/office water management, there are a number of emerging sensing
technologies to reduce network losses and improve the efficiency of water networks. These include leakdetection monitors which area able to pinpoint more accurately the damaged section of pipework bymonitoring the pressure and vibrations caused from flowing water. Potable water distribution andtransmission networks often operate at needlessly elevated pressures. As such, water companies arelooking to optimise network pressures by reducing pressure when demand is low to save on pumping
energy. I2O water has developed a system whereby District Metered Area valves are automaticallycontrolled based on how the pressure at key locations in the network compares with a pre-determined
minimum threshold pressure. Similarly variable frequency drives are becoming a mainstream approachto managing localised fluctuations in pumping demand to be more energy efficient.
5.3.1.11 Micro-climate controlled irrigation – Different plants require different growing conditions, and microclimate can vary considerably across sites. Smart irrigation systems combine soil moisture and localised
wind monitoring, along with an understanding of the plants optimum hydration, to deliver tailoredirrigation requirements to different parts of the same site.

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Sustainability

Feasibility

Core Objectives

Characteristics

Old Oak Common and Park Royal

Integrated W ater Management Strategy

Park Royal - RetainedPark Royal - New Build

Old Oak Common

AssumedTechnology

Retrofit of water efficientdevices within existing
industrial properties to meetthe current efficiency
standards, as specified in
the building regulations.

All new build developments
constructed to the water
efficiency requirements
specified in the London Plan.

All new build developments
constructed to the water
efficiency requirements
specified in the London Plan.

Applicable Scale

Building scale

Potential Potable
Water Savings

HIGH - Up to 27% reduction(122 ML/year)

MEDIUM - Up to 11%
reduction (28 ML/year)

MEDIUM - Up to 14%
reduction (408 ML/year)

Potential
Discharge
Reduction

LOW - 6% reduction of totaldrainage discharge (122ML/year)

MEDIUM - 7% reduction of
total drainage discharge (28ML/year)

MEDIUM - 11% reduction of
total drainage discharge(408 ML/year)

Potential
Attenuation
Contribution

NONE

Indicative Cost

MEDIUM - Estimated 1-2%of capital construction cost(£26,500,000)

LOW - Estimated 0-1% ofcapital construction cost(£2,000,000)

LOW - Estimated 0-1% ofcapital construction cost(£24,000,000)

Spatialrequirements

NONE- Minimal requirements above standard fittings

MaintenanceRequirements

LOW - Minimal requirements above standard fittings

Regulatory andPublicAcceptability

HIGH - Supported by current planning policy and regulation. Potential for public acceptability
uptake to decrease if user satisfaction diminishes,

Flexibility andscalability

HIGH - Ability for gradual implementation and retrofit, harnessing latest available
technologies.

Carbon intensity

LOW - Technologies can also result in reduced energy consumption, through reducing theenergy consumption of pumping and hot water systems.

Blue-green spaceprovided

NONE

ClimateResilience

MEDIUM - Reduced consumption resulting in reduced strain on existing resources.

Surface water
quality

LOW - Marginal benefit through reduced flows to sewer, with reduced associated impact on
downstream receiving waterbodies.

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5.4

Green Roofs

5.4.1.1

Green roofs consist of a planted soil layer, constructed on theroof of a building to create a living surface. The vegetatedsubstrate is generally built on top of a drainage layer. Following
rainfall, water is stored in the soil layer and absorbed byvegetation. Green roofs may be designed to be constructed to beaccessible, and landscaped to provide biodiversity andcommunity benefit. In many cases, it may be beneficial to
combine vegetated roofs with roofwater collection storages tocreate blue-green roofs, where the stored water can be used toprovide an additional balancing irrigation supply for vegetation.
Green roofs may be constructed on new buildings, or retrofitted
onto existing surfaces, although, in some cases there will be
restrictions on the ability to retrofit due to inadequate structural
capacity or overly sloping surfaces, and are likely to be more
expensive.

5.4.1.2

Figure 16 - Intensive green roof
The construction of Green Roofs will result in a reduction of
runoff occurring from roof surfaces, through adsorption, andevapotranspiration by the rooftop vegetation. The reduction in impervious surface will also provide
benefits in reducing the speed of runoff and providing water quality benefits through filtration and bioretention. Green Roofs also have the potential to provide a range of wider benefits, including provisionof habitat for biodiversity, improved air quality, recreational and amenity benefits and amelioration of theurban heat effect. Living walls and green facades may also be suitable for installation and provide
similar functions and benefits as green roofs.

5.4.1.3 Innovation in Green Roofs
5.4.1.4

30

There have been a number of advances in green roof technologies, particularly in the development ofeasier to assemble modular kits, irrigation systems and protective membranes. There have also been
advances in planting application. As with surface SuDS, plant selection and the substrate composition
that can have a number of water quality benefits in addition to reducing run-off rates. Roof-top wetlands
have even been used to treat rain and grey water for reuse in the buildings on which they are situated.

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Sustainability

Feasibility

Core Objectives

Characteristics

Park Royal - RetainedPark Royal - New Build

Old Oak Common

Intensive, landscaped green
roofs installed on all newbuildings.

Intensive, landscaped green
roofs installed on all newbuildings.

AssumedTechnology

Retrofit of lightweight,
extensive green roofs onexisting buildings.

Applicable Scale

Building scale

Potential Potable
Water Savings

NONE

Potential
Discharge
Reduction

MEDIUM - Up to 10%
reduction of total drainage
discharge. (223 ML/year)
through greater absorption
and evapotranspiration.

LOW - Up to 9% reductionof total drainage discharge.
(35 ML/year) throughgreater absorption andevapotranspiration.

LOW - Up to 4% reductionof total drainage discharge(167 ML/year) throughgreater absorption andevapotranspiration.

Potential
Attenuation
Contribution

LOW - Estimated water
storage capacity of
approximately 1% of
required attenuation
volume.

LOW - Estimated water
storage capacity of
approximately 6% ofrequired attenuation
volume.

HIGH - Estimated water
storage capacity of
approximately 25% ofrequired attenuation
volume.

Indicative Cost

VERY HIGH - Estimated
3+% of capital construction
cost (£175,000,000)

HIGH - Estimated 1-2% ofcapital construction cost(£16,000,000)

LOW - Estimated 0-1% ofcapital construction cost(£33,000,000)

Spatialrequirements

LOW - No additional land take.

MaintenanceRequirements

LOW - Irrigation required during establishment of vegetation, ongoing inspection andmonitoring of vegetation cover, removal of litter or debris.

Regulatory andPublicAcceptability

HIGH - Supported by current planning policy and potential to provide recreational andamenity benefit

Flexibility andscalability

HIGH - Ability for gradual implementation as development progresses. Limitations for retrofit
on some existing buildings, due to inadequate structural composition or overly sloping
surfaces.

Carbon intensity

LOW - Potential for carbon sequestration and building insulation, with reduced associatedenergy requirements.

Blue-green spaceprovided

HIGH - provision of green space, with the potential to provide recreational and amenity
benefit, habitat for biodiversity, improved air and water quality and microclimate benefits.

Climate Resilience

MEDIUM - Provision of attenuation and vegetation to assist in mitigating the impacts of climatechange on drainage systems. Delivery of drought tolerant species is recommended.

Surface water
quality

HIGH - Vegetated system reducing the quantity and the speed of runoff and providing water
quality benefits through filtration and bio-retention.

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5.5

Roof Water Recycling

5.5.1.1

Rainwater can be collected from the roof of buildings andstored in underground or over ground tanks for reuse locally.
The collected water may be used for garden watering or indoor
non-potable uses, such as toilet flushing or hot water andlaundry uses. As such, roof water collection contributes to a
reduced discharge of urban runoff to the combined andsurface water sewer systems and a reduction in potable watersupply volume. Due to the reduced exposure to contaminants,
treatment infrastructure is often lower than for other types ofwater; however, disinfection is likely to be required if the water
is to be used for higher contact uses including hot water
systems, laundry uses or spray applications, and particularly ifwater is likely to be mixed with centralised potable supplies.

5.5.1.2

Storage volumes for rainwater harvesting are likely to besignificant, due to the highly variable nature of the inflow. A

Integrated W ater Management Strategy

key constraint within the Opportunity Areas is the misalignmentof demand and catchment availability. Within Old Oak Figure 17 - Plot scale roofwater harvesting
common, the limited rooftop catchments will not provide
sufficient flows to meet the non-potable demand within the high density development. If utilised, thiswould additionally need to be mixed with centralised supplies, with stringent controls necessary to
mitigate any risk of cross-contamination. Conversely, significant supply is present in Park Royal due tolarge rooftop catchments; however, retrofit of dedicated non-potable internal distribution pipework is
unlikely to be feasible, limiting recycling to outdoor irrigation, wash-down use, or for specific industrial
processes not requiring potable quality water. Transferring water between the catchments would requirecomplex pipework retrofits, which may provide only limited benefit over other area scale non-potable
recycling options.
5.5.1.3

Potable re-use of rainwater is also possible, and may present an opportunity for water recycling in the
short term, due to the high raw water quality. Allowance for potable augmentation would mean thatharvested water could be directly reused, avoiding the challenges of separate non-potable pipework.
Stringent water quality control and long-term monitoring and validation would be recommended tomitigate any operational risks.

5.5.1.4 Innovation in Rainwater Harvesting
5.5.1.5

Gravity fed rainwater harvesting – The potential for rainwater reuse is perhaps greatest in retrofittingbuildings with large roof areas such as within Park Royal. Most rain water harvesting systems collectwater at the base of the down pipe for storage underground. This however requires energy to pump therain water back to where it is to be used; often several floors up. David Bultler from the University of
Exeter is one of a number of advocates developing approaches to gravity fed rain water harvesting
systems that hold water in the roof space to build up a head of pressure so that pumping becomesredundant.

5.5.1.6

Aqua-Storm Control – Large buildings generally require large attenuation tanks to manage storm water.
Variation in storm volume and frequency means that this is not viable for reuse. Supplementing this rainwater with grey water means that a more reliable non-potable supply can be maintained, however toensure there is sufficient storm volume reserved in these passive systems, an oversized or dual tank isrequired, increasing the capital installation costs. Aqua-lity’s Aqua-Storm Control systems provides anactive solution by using real time weather data to predict future rainfall events. This means that grey
water stored for reuse can be slowly released ahead of the storm to provide capacity for the rain water
whilst retaining sufficient non-potable water supply all within in a standard sized tank.

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Sustainability

Feasibility

Core Objectives

Characteristics

Park Royal - RetainedPark Royal - New Build

AssumedTechnology

Retrofit of roof water
harvesting systems on all
existing buildings in Park
Royal, with water available
for outdoor or specificprocess re-use.

Applicable Scale

Likely to be most feasible at a building scale or a communal (development) scale.

Potential Potable
Water Savings

UNKNOWN - Sufficientavailable supply to offset
non-potable demand(42% 197 ML/year).
However, pipework
constraints will limit theextent to which this may
be utilised.

HIGH - Up to 27% reduction
in demand (62 ML/year)

LOW - Up to 8% reduction
in demand (238 ML/year)

Potential
Discharge
Reduction

LOW - Up to 9% reductionof total drainage
discharge (197 ML/year)

MEDIUM - Up to 16%
reduction of total drainage
discharge (63 ML/year)

LOW - Up to 6% reductionof total drainage discharge(238 ML/year)

Potential Storage
Contribution

MEDIUM - Water storage
will be provided; however,
it is unlikely that thiscapacity will be allavailable to provide
storage during storm
events.

MEDIUM - Water storage
will be provided; however,unlikely that this capacity
will be all available toprovide storage duringstorm events.

HIGH - Water storage will
be provided; however,unlikely that this capacity
will be all available toprovide attenuation storage
during storm events.

Indicative Cost

VERY HIGH - Estimated
3+% of capitalconstruction cost(£72,000,000)

HIGH - Estimated 2-3% ofcapital construction cost(£13,500,000)

MEDIUM - Estimated 1-2%of capital construction cost(£58,000,000)

Spatialrequirements

LOW - Spatial requirements for water storage, to manage variability in rainfall; however,
below ground or rooftop storage can minimise additional land take.

MaintenanceRequirements

MEDIUM - Ongoing inspection and cleaning of collection systems, filters, valves and pumps.
Requirement for ongoing treatment and pumping.

Regulatory andPublicAcceptability

MEDIUM - Perceived as a relatively high quality water source; however, potential for
regulatory barriers, particularly if harvested supplies are required to be mixed with centralised
supply to meet non-potable demand.

Flexibility andscalability

HIGH - Ability for gradual implementation as development progresses.

Carbon intensity

MEDIUM - Ongoing energy requirements for pumping and reticulation. However, very highquality and can be used for a variety of end uses with minimal treatment requirements, andassociated low-energy intensity of treatment.

Blue-green spaceprovided

NONE

Climate Resilience

MEDIUM - Climate dependant water supply with the requirement for substantial water
storage volumes to mitigate seasonal fluctuations in water availability. However, presents analternative supply option to decrease reliance on centralised system.

Surface water
quality

MEDIUM - Reduced hardscape discharge to drainage system.

33

Localised roof water
harvesting systems on all
new buildings, includingcollection, filtration, UV
disinfection, pumping andnon-potable reticulation.

Old Oak Common
Localised roof water
harvesting systems on all
new buildings, includingcollection, filtration, UV
disinfection, pumping andnon-potable reticulation.

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Old Oak Common and Park Royal

5.6

Grey Water Recycling

5.6.1.1

Grey water is wastewater that excludes toilet waste andis therefore of a higher quality than sewage. It includes
waste from uses such as hand washing and showering.
Water is collected using separate plumbing (to thestandard sewage system), stored, treated andredistributed for non-potable use. Due to the potential
for contaminants and pathogens to be present in grey
water, it requires a higher level of treatment than rainwater. This will include some form of filtration, biologicaltreatment and disinfection, generally undertaken withina package treatment unit. A significant advantage ofgrey water as a supply option is that it is largely climate
independent, so is more reliable and therefore requires
reduced storage volumes. It should be noted thatcombined storage and reuse of rainwater greywaterand storm water is possible, and can result in increased
consistency of water supply and reduced capital costs(see section 10). In order to facilitate cost savings thesefeatures use the same storage volume for recycled
greywater and storm attenuation, discharging recycledvolumes in anticipation of storm events, using intelligent
control systems.

5.6.1.2

Integrated W ater Management Strategy

Figure 18 - Plot scale grey water reuse

Recycling of greywater is a localised solution to significantly reduce booth foul water flows, and potabledemands. As such, this is scalable and avoids many of the feasibility challenges associated with areascale recycling. However, there are likely to be cost savings and energy efficiencies in installing
localised systems within all buildings across the development areas.

5.6.1.3 Innovation in Grey Water Recycling
5.6.1.4

34

Grey water recycling – Grey water recycling has developed from very small scale direct reuse and shortretention systems with limited application to large block scale approaches. Although chemical systems
have been developed, hybrid bio-mechanical systems with UV treatment offer perhaps the mostsustainable application. They use a combination of biological treatment using bacteria and microbes tobreak down solid waste as well as membrane filtration.

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Characteristics

Park Royal - Retained

AssumedTechnology

Applicable Scale

Sustainability

Feasibility

Core Objectives

Potential Potable
Water Savings
Potential
Discharge
Reduction
Potential
Attenuation
Contribution

Unlikely to be feasible forexisting buildings due to theplumbing requirement for
dedicated greywatercollection pipework andnon-potable redistribution
pipework. May beappropriate forrefurbishments or new
developments.

Park Royal - New Build

Old Oak Common

Installation of building scale
greywater recycling and nonpotable re-use systems for
all new buildings.

Installation of building scale
greywater recycling and nonpotable re-use systems for
all new buildings.

Likely to be most feasible at a building scale or sub-area(development) scale.
HIGH - Up to 27% reduction
in demand (63 ML/year)

HIGH - Up to 21% reduction
in demand (642 ML/year)

MEDIUM - Up to 16%
reduction of total drainage
discharge (63 ML/year)

MEDIUM - Up to 17%
reduction of total drainage
discharge (642 ML)

NONE

Indicative Cost

MEDIUM - Estimated 1-2%of capital construction cost(£8,000,000)

Spatialrequirements

LOW - Storage, treatment and distribution infrastructure integrated within building design.
Minimal storage volumes are required due to consistency of supply. Below ground tanks canalso minimise any additional land take.

MaintenanceRequirements

MEDIUM - Inspection and cleaning of collection and treatment systems including filters
valves and pumps.

Regulatory andPublicAcceptability

MEDIUM - Potential for some public perception issues and regulatory barriers, depending on
proposed end uses.

Flexibility andscalability

HIGH - Highly scalable system with minimal space requirements.

Carbon intensity

HIGH - Ongoing energy and maintenance requirements. Potential for lost efficiencies
through delivery of numerous localised solutions.

Blue-green spaceprovided

NONE

ClimateResilience

HIGH - Highly consistent supply of water with low climate dependency, resulting in minimal
storage requirements.

Surface water
quality

LOW - Marginal benefit through reduced flows to sewer, with reduced associated impact on
downstream receiving waterbodies.

35

HIGH - Estimated 2-3% ofcapital construction cost(£95,000,000)

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Old Oak Common and Park Royal

5.7

Green Source Control Measures

5.7.1.1

Implementing Sustainable Urban Drainage Systems(SuDS) aims to recreate more natural drainage systems
within the urban environment. These features celebrate
the presence of water, enriching the urban environment,
while providing valuable function for flood alleviation andbiodiversity enhancement. At the plot or development(sub-area) scale, source control measures look tomaximise permeable surfaces within the site in an effort
to increase the amount of water that is attenuated,
treated and processed within the natural hydrologicalcycle. As such, incorporating features such as
raingardens, filter strips, swales and tree pits will assist inabsorbing runoff generated within the development,
reducing flooding, improving water quality, providing
irrigation for vegetation and improve amenity. Suchfeatures can also contribute to a range of wider benefits,
including provision of habitat for biodiversity, improved air
quality and amelioration of the urban heat effect.

Integrated W ater Management Strategy

Figure 19 - Plot scale raingardens

5.7.1.2

Incorporation of these measures will contribute towards providing the required attenuation storage, andreducing the volume of storage required. Managing surface water quality and quantity on site will be also
be essential to the successes of any downstream measures, preventing inundation of surface water
conveyance networks and effectively managing water quality throughout the development. Many SuDS
measures are designed to promote infiltration of runoff into the ground beneath, promoting recharge of
the water table and reducing runoff. However, these types of measures are unlikely to be suitable within
the development site due to the underlying geology, which is largely impermeable (as well as
contamination risk in some areas). Therefore, SuDS features will need to be focused on surface water
storage and attenuation. While grassed, permeable surfaces should be encouraged on the site; any
incorporated SuDS features designed to collect and transport water should be lined so as to transportwater to an area where it can be safely disposed. While green measures such as those described above
are preferred, hardscape systems like permeable paving, canals, rills and underground storage may besuitable, given the spatial constraints of the site.

5.7.1.3

Within new developments, there are opportunities to provide multi-functional green-blue infrastructure,
incorporated within the landscaping of the site. Within the retained development areas, SuDS measureswould need to be retrofitted to manage runoff, which increases construction costs. The current land uses
are likely to be of a density where this is achievable; however, the feasibility of options may beconstrained by the existing site layouts, topography and drainage infrastructure.

5.7.1.4 Innovation in SuDS
5.7.1.5

6

Despite a long period of uncertainty surrounding the legislative and regulatory requirements forsustainable drainage systems, the National Planning Policy Framework (NPPF), the London Plan andlocal planning policy has long advocated the consideration of SuDS. The recently released update of the
SuDS Manual (2015)6 highlights that SuDS can contribute to water management objectives on any site,
although some sites with specific challenges, such as gradient, low infiltration rates or contamination will
have a more limited suite of potential approaches. Most SuDS are, in themselves, relatively straightforward in design. However, consideration of drainage solutions often occurs late in the master planning
process; generally once plot areas and GFA have been calculated. Innovation really occurs in thedeveloping a holistic approach to a SuDS train – a network of different SuDS – from the outline design
by following where possible the sites natural hydrology to inform design decisions and guide thecharacter of the public realm. This is a process known as WSUD. CIRIA’s UK WSUD Scoping Study(2013) and associated ideas book highlights how this approach applies to different urban character

SuDS Manual, CIRIA (2015) - http://www.susdrain.org/resources/ciria-guidance.html

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areas7. By considering SuDS early in this way as in this integrated water management strategy, they
can provide a more meaningful contribution to controlling runoff rates, improving water quality andincreasingly provide a source of water reuse in the most cost effective way.
5.7.1.6

The updated SuDS Manual includes details of a number of proprietary treatment products and SuDS
approach. Some key emerging themes and products include:
Bioretention and manufactured soils – The accepted approach to bioretention using a loamy soil
filtration layer with a geotextile layer transition has less than desirable water quality performanceand invariably the geotextile layer can become clogged. Building on research by the likes of Wongand Ford, the new SuDS manual recognises that emerging new generation of engineered soils
coming to market can offer greater resilience to blockages and improved water quality.
Tree Pits and rain gardens – Similarly, although tree pits and rain gardens are well understood intheir ability to provide attenuation and preliminary treatment, they are not widely used. Concerns
around invasive roots and salt damage are often cited as reasons for not using them, althoughthese challenges can be overcome.
Crate systems – Although crate systems, such as Permavoid, have been available for a reasonable
length of time they are increasingly being used in a wider range of applications, such as blue roofs.
Thirsty concrete – Hard, durable permeable surfacing has traditionally focused on block pavers
which are generally not acceptable forms of surfacing to be adopted by local and highway
authorities. Tarmac has recently developed Topmix Permeable, a new permeable concrete that theyclaim can absorb up to 4,000l of water in the first minute of saturation. It works by using a new formof permeable top layer concrete which allows water to drain into a matrix of large pebbles and thendown into a loose base of rubble beneath. Although this has been coupled with drainage networks
to help restore ground water, where there is a high water table or impermeable sub-soils, such
London clay, alternative approaches to below ground storage may be required. The concrete ishowever easily damaged by freezing conditions.

Figure 5-6 - Thirsty Concrete (Source: Tarmac)

7

http://www.ciria.org/Resources/Free_publications/Water_Sensitive_Urban_Design.aspx

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Sustainability

Feasibility

Core Objectives

Characteristics

Old Oak Common and Park Royal

Integrated W ater Management Strategy

Park Royal - RetainedPark Royal - New Build

Old Oak Common

AssumedTechnology

Retrofit of SuDS features(bio-retention systems) and
30% additional permeablesurface on all existing landparcels.

Installation of SuDS bioretention systems and 30%
additional permeablesurface on all new
development plots.

Installation of SuDS bioretention systems and 30%
additional permeable surface
on all new development
plots.

Applicable Scale

Plot or development scale.

Potential Potable
Water Savings

NONE

Potential
Discharge
Reduction

MEDIUM - Estimatedreduction of 11% of overalldrainage discharge (237ML/year)

LOW - Estimated reductionof 3% of overall drainage
discharge (11.5 ML/year)

LOW - Estimated reductionof 1% of overall drainage
discharge (24 ML/year)

Potential
Attenuation
Contribution

LOW - Dependent on
extent and type of features
implemented. Estimatedstorage of approximately
2% of required attenuation.

LOW - Dependent on
extent and type of features
implemented. Estimatedstorage of approximately
2% of required attenuation.

LOW - Dependent on
extent and type of features
implemented. Estimatedstorage of approximately
1% of required attenuation.

Indicative Cost

VERY HIGH - Estimated
3+% of capital construction
cost (£149,000,000)

HIGH - Estimated 2-3% ofcapital construction cost(£13,000,000)

LOW - Estimated 0-1% ofcapital construction cost(£27,500,000)

Spatialrequirements

MEDIUM - Reasonable surface spatial requirements, which may be difficult to achieve given
the high density nature of the proposed development. However, this may be integrated withinsite landscaping and delivered to provide multiple benefits,

MaintenanceRequirements

MEDIUM - Regular inspection and maintenance, including removal of litter and debris andvegetation management.

Regulatory andPublicAcceptability

HIGH - Supported by current planning policy and potential to provide recreational andamenity benefit.

Flexibility andscalability

HIGH - Scalable, with the ability for gradual implementation.

Carbon intensity

LOW - Potential for carbon sequestration.

Blue-green
space provided

HIGH - provision of green space, with the potential to provide recreational and amenity
benefit, habitat for biodiversity, improved air and water quality and microclimate benefits.

ClimateResilience

MEDIUM - Provision of attenuation and vegetation to assist in mitigating the impacts of climatechange on drainage. Capacity design for increased storm intensity will be required.

Surface water
quality

HIGH - Vegetated systems providing water quality benefits through filtration and bio-retention.

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5.8

Below Ground Storage

5.8.1.1

Underground geo-cellular storage can be implemented withinsite drainage systems to control and manage runoff generated
on the site. These systems can be designed to withstandtraffic loads, meaning that they can be installed under roads
and car parks as well as recreational areas and other public
open space. During high intensity rainfall events, thesefacilities provide on-site attenuation, restricting outflow to
avoid overloading the drainage system. Installed in isolation,these structures will not have any benefit in reducing total
discharge to the sewer system; however, by restricting thepeak instantaneous discharge rates during storm events, they
contribute to preventing flooding issues. Stormwater
attenuation tanks may be combined with storage for greywateror rainwater recycling systems, resulting in cost efficiencies
and, if appropriate treatment measures are in place, reused
for non-potable supply.

5.8.1.2

Underground storage does not deliver the additional benefit Figure 21 - Underground stormwater attenuation
associated with green infrastructure; however, may provide apractical means of achieving the required attenuation volumes, particularly within development plots,
which are likely to be extremely spatially constrained. There is also likely to be some opportunity to
install below ground attenuation within the retained properties across Park Royal. However, this would
likely require bespoke solutions, and will be limited by constraints of the existing infrastructure.

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Sustainability

Feasibility

Core Objectives

Characteristics

Old Oak Common and Park Royal

Integrated W ater Management Strategy

Park Royal - RetainedPark Royal - New Build

Old Oak Common

AssumedTechnology

Retrofit of geo-cellularstorage within existing
properties providing
attenuation to achievegreenfield runoff rates.

Installation of geo-cellularstorage within development
plots, providing attenuationto achieve greenfield runoff
rates.

Installation of Geo-cellularstorages within development
plots, providing attenuationto achieve greenfield runoff
rates.

Applicable Scale

Plot or development scale is likely to be most suitable.

Potential Potable
Water Savings

NONE

Potential
Discharge
Reduction

NONE

Potential
Attenuation
Contribution

HIGH - Potential to provide
up to 100% of required
dispersed or collective
attenuation, if delivery is
feasible.

HIGH - Potential to provide
up to 100% of required
dispersed or collective
attenuation, if delivery is
feasible.

HIGH - Potential to provide
up to 100% of required
dispersed or collective
attenuation, if delivery is
feasible.

Indicative Cost

VERY HIGH - Estimated
3+% of capital construction
cost (£212,000,000)

HIGH - Estimated 2-3% ofcapital construction cost(£15,000,000)

LOW - Estimated 0-1% ofcapital construction cost(£12,000,000)

Spatialrequirements

LOW - Significant volumes are required to meet Greenfield runoff rates. However,underground installation minimises effective land requirements.

MaintenanceRequirements

MEDIUM - Regular inspection of silt traps, manholes, pipework and pre-treatment devices,with removal of sediment and debris as required.

Regulatory andPublicAcceptability

HIGH - Supported by current planning policy and potential to provide recreational andamenity benefit.

Flexibility andscalability

HIGH - Scalable, with the ability for gradual implementation. Below ground installation limits
flexibility, and opportunities may be limited by, or impact upon, the deliverability of other
underground infrastructure.

Carbon intensity

LOW - minimal ongoing energy requirements.

Blue-green
space provided

NONE

ClimateResilience

MEDIUM - Provision of attenuation to assist in mitigating the impacts of climate change on
drainage. Capacity design for increased storm intensity will be required.

Surface water
quality

MEDIUM - Some water quality benefit provided through storage, sedimentation and reduced
drainage flows; however, limited benefit as opposed to above ground surface water
management.

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5.9

Strategic SuDS Networks

5.9.1.1

A strategic surface water network will be required
across the Opportunity Areas to manage andconvey surface water, while providing attenuation
and water quality treatment. As an alternative to
traditional underground, piped systems, this may
be delivered using a connected sequential train of
SuDS features, such as swales, filter strips andflow spreaders. Providing several SuDS featuresin a series will enhance treatment as the slowed
water passes the different features and treatment
mechanisms. The infrastructure will also have arange of positive benefits to the urban
environment, through improved aesthetics, airand water quality, microclimate management andbiodiversity benefit. The capacity of the network

Integrated W ater Management Strategy

must be sufficient to drain roads and public
Figure 22 - Streetscape swales
space, while conveying water collected from plots,
to downstream locations for storage, harvesting ordischarge. As such, the required configuration will be strongly influenced by selected option forstormwater discharge, and the balance of on-plot to downstream attenuation.
5.9.1.2

The design and configuration of the streetscape network would require detailed consideration of spatial
availability and constraints, topography, water quality and discharge. Desirably, the street network
should be flexibly designed around the natural hydrology of the area, with overall site levels rationalisedin order to facilitate natural drainage pathways over as much of the area as possible. The presence ofextensive rail infrastructure and the canal may place constraints on the ability to install comprehensive
networks, by fragmenting the surface connectivity of the catchment which may require the installation of
supporting conventional underground infrastructure. Availability of space may present a significant
challenge; however, a network of public green space is proposed to be delivered with the regeneration
proposals, which may provide opportunities for distributed blue-green infrastructure within thestreetscape and public spaces.

5.9.1.3

Within retained areas of the Opportunity Areas, the installation of SuDS within the streetscape will beeven more constrained by the existing infrastructure and spatial limitations, so it is unlikely that this
could initially entirely replace conventional drainage infrastructure. However, there are likely to beopportunities for local collection of stormwater in strategically located green infrastructure integrated
within the streetscape, utilising tree planting, traffic calming, parking bays, verges and central
reservations. The provision of these landscaped features could be used to capture surface water runoff
from roofs and road, providing attenuation and treatment before discharge to the sewer system. Porous
paving and hardscape solutions may also be appropriate in this area.

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Sustainability

Feasibility

Core Objectives

Characteristics

Park Royal - RetainedPark Royal - New Build

Old Oak Common

Extensive SuDS networks
installed in the place of
conventional drainage
systems to drain all roads
and public space.

Extensive SuDS networks
installed in the place of
conventional drainage
systems to drain all roads
and public space.

Assumed Technology

Retrofit of green
infrastructure within thestreetscape to collect,attenuate and convey
storm water.

Applicable Scale

Assumed area wide; however, may also be appropriate for development scale.

Potential Potable Water
Savings

NONE

Potential Discharge
Reduction

LOW - Reduced volume
of surface water
discharge throughenhanced
evapotranspiration andbiological uptake.

LOW - Reduced volume
of surface water discharge
through enhanced
evapotranspiration andbiological uptake.

LOW - Reduced volume
of surface water
discharge throughenhanced
evapotranspiration andbiological uptake.

Potential Attenuation
Contribution

LOW - Dependent on
installed features andspatial availability.
Estimated minimum of
5% of required
attenuation volume isachievable.

MEDIUM - Approximately
13% of attenuation
required, dependant on
spatial availability.

HIGH - Estimated 42% ofattenuation required could
be provided dependanton spatial availability.

Indicative Cost

HIGH - Estimated 2-3% ofcapital construction cost
£23,000,000

LOW - Estimated 0-1% ofcapital construction cost(£800,000)

LOW - Estimated 0-1% ofcapital construction cost(£4,000,000)

Spatial requirements

MEDIUM - Reasonable surface spatial requirements, which may be difficult toincorporate into the dense development areas, and particularly challenging to retrofit inexisting areas. However, this may be integrated within site landscaping and delivered
to provide multiple benefits.

MaintenanceRequirements

MEDIUM - Litter and debris clearance and removal, vegetation management,
monitoring and repair of damaged or degraded areas. Above ground systems canincrease the ease of identifying and undertaking required repairs.

Regulatory and Public
Acceptability

MEDIUM - Multi-functional infrastructure can enhance the streetscape and public
realm. Determining responsibility for ongoing maintenance may present some barriers.

Flexibility andscalability

MEDIUM - Delivery can likely be phased in line with construction of the street network;
however, early consideration of topography, street layout and discharge is required tomaximise benefit.

Carbon intensity

LOW - Maximises passive conveyance and treatment by harnessing natural
catchment hydrology. Potential for carbon sequestration.

Blue-green spaceprovided

HIGH - provision of green space, with the potential to provide recreational and amenity
benefit, habitat for biodiversity, improved air and water quality and microclimate
benefits.

Climate Resilience

MEDIUM - Provision of attenuation and increased permeability to assist in mitigating theimpacts of climate change on drainage. Capacity design for increased storm intensity
will be required.

Surface water quality

HIGH - Promote evaporation and absorption of surface water and reduced pollutant
loads through filtration and biological degradation. Drainage from industrial areas may
contain high contaminants of pollutants which will require management.

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5.10

Integrated W ater Management Strategy

Waterway Storage and Discharge

5.10.1.1 There are two significant waterways within
the immediate vicinity of the Opportunity
Areas. These are the Grand Union Canal,
running through the centre of both Areas,
and the River Brent, running along thewestern boundary of the Park Royal.
Currently, the western extents of Park
Royal, within Thames Water’s Mogden subcatchment, discharges surface water to theRiver Brent. To avoid overloading or
exacerbating the sewer flooding issues
within the Counters Creek catchment, it may
be possible to modify the surface water
catchment areas to discharge a greater areaof (retained) Park Royal to the River Brent.
Similarly, discharge of surface water within
Old Oak Common, and certain areas ofPark Royal (including the New Build areas)
Figure 23 - Stormwater discharge to local waterways
to the Grand Union Canal may be an option.
The natural topography of the Opportunity Areas would likely impact how much of the area would be
able to be re-directed to these catchments.
5.10.1.2 Appropriate attenuation and water quality management measures (as described above) would be
required to ensure no adverse impacts on the watercourse hydrology and quality. Detailed hydrologicalanalysis would also be necessary to ensure that these measures did not cause any additional flood risk
to other areas of the catchments or contribute to pollution or ecological deterioration. Allowable
discharge rates and associated impacts on flow regimes, during times of both high and low flow would
require investigation. Additionally, particular consideration would be required to manage surface water
discharge from industrial areas, which may contain contaminants. Detailed consultation with theEnvironment Agency, the Canal and The River Trust would be required in further scoping these options.
5.10.1.3 As an alternative to ultimate discharge to these sources, it may be possible to use the Canal or River for
temporary storage and conveyance of peak surface water flows, which could be subsequently extracted
to avoid any net increase in flows. However, this is likely to require complex pumping mechanisms, andfurther scoping is required to confirm this as an option.
5.10.1.4 Considering wider discharge options, it may also be possible to inject collected surface water to a below
ground aquifer for artificial groundwater recharge. It is understood that there is not an appropriate
aquifer located within the immediate vicinity of the site; therefore water would need to be transported
outside the site, to a suitable location for injection.

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Sustainability

Feasibility

Core Objectives

Characteristics

Old Oak Common and Park Royal

Integrated W ater Management Strategy

Park Royal - RetainedPark Royal - New Build

Old Oak Common

AssumedTechnology

Manageddischargeorstorage of runoff to the River
Brent (or Grand Union
Canal), through connection of
new sustainable drainage
infrastructure.

Managed discharge orstorage of runoff to the
Grand
Union
Canal,
through connection of new
sustainabledrainageinfrastructure.

Managed discharge orstorage of runoff to the
Grand
Union
Canal,
through connection of new
sustainabledrainageinfrastructure.

Applicable Scale

Development or area wide scale

Potential Potable
Water Savings

NONE

Potential Discharge
Reduction

VERY HIGH - Up to 80%
reduction of total discharge
to the drainage system(assuming 100% of surface
water discharged)

VERY HIGH - Up to 42%
reductionof
total
discharge to the drainage
system (assuming 100%ofsurfacewaterdischarged)

VERY HIGH - Up to 23%
reductionof
total
discharge to the drainage
system (assuming 100%ofsurfacewaterdischarged)

Potential
Attenuation
Contribution

Potential to provide a significant proportion of required attenuation; however this isdependent on system configuration and requires further hydrological analysis.

Indicative Cost

Unable to be assessed based on current information; however, primary capital costs arelikely to be associated with provision of a new surface water drainage network (asdiscussed above)

Spatial requirements

LOW - Minimal, excepting associated spatial requirements for surface drainage andattenuation systems (discussed separately)

MaintenanceRequirements

Primary requirements will be as associated with related drainage and attenuation
infrastructure. Potential for additional ongoing costs related to discharge.

Regulatory andPublic Acceptability

MEDIUM - Some regulatory barriers are possible; however, this is consideredmanageable provided appropriate consultation and the discharge is carefully managed tomitigate any downstream increased flood risk or water quality impacts.

Flexibility andscalability

MEDIUM - Provided stakeholder agreement is reached, discharge may be able to be
incrementally transferred to different locations, in line with the delivery of thedevelopment. However, upfront planning of levels, street layout and discharge locations
would be required.

Carbon intensity

LOW - removing surface water flows from the sewer system will reduce the volume ofbeing conveyed to downstream treatment plants.

Blue-green spaceprovided

NONE - no direct impact; however, this may be provided through delivery of associateddrainage infrastructure.

Climate Resilience

MEDIUM - removing surface water flows from the sewer system will assist in mitigating theimpacts of climate change on drainage.

Surface water
quality

MEDIUM - moving towards more natural pre-development catchment conditions willassist in mitigating water quality issues associated with CSO overflows; however,potential water quality and waterway health implications will need to be carefully
considered and mitigated.

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5.11

Integrated W ater Management Strategy

Downstream Stormwater Retention Ponds or Wetlands

5.11.1.1 As an alternative to providing localised, on-plot
storage of storm water runoff, downstream detention
may also be provided. This could be in the form of adry detention basin or a pond or wetland system, withthe potential to provide additional quality andbiodiversity benefits. These systems provide
attenuation and treatment of storm water runoff, andare designed to support emergent and submerged
aquatic vegetation along the shoreline. The retention
time
promotes
pollutantremovalthroughsedimentation and the opportunity for biologicaluptake mechanisms further reduces concentrationsof pollutants. These features also have the potential
to provide significant ecological and amenity
benefits, while contributing to improved air quality,
and amelioration of the urban heat effect.

Figure 24 - Downstream stormwater attenuation

5.11.1.2 Significant volumes of water storage would be required to achieve Greenfield rates, which could be
provided as a single volume, a series of dispersed volumes, or used in conjunction with other means ofproviding attenuation. The natural topography of the two Opportunity Areas and the presence of existingdrainage systems will impact the required location and contributing catchment of the retention storage.
These systems would be most effective if installed in conjunction with upstream SuDS networks, to treat
and convey incoming storm flows. The availability of space will be the major constraint in the delivery of
surface storages, with further challenges presented by the presence of the canal and rail infrastructure,
disrupting the surface connectivity of the catchment.
5.11.1.3 Within retained areas, the availability of space to implement attenuation storage in this area is currently
highly limited by the density of exiting developed industrial land uses. It is unlikely that existing space will
be readily available, sufficient to provide the storage volumes required. However, as a part of thedevelopment proposals, there will likely be opportunities to secure additional community green space,which may provide opportunities for the delivery of dispersed surface water storage and treatment
features. Alternatively, land space could be acquired through direct land purchase.

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Integrated W ater Management Strategy

Sustainability

Feasibility

Core Objectives

Characteristics

Park Royal - RetainedPark Royal - New Build

Old Oak Common

Assumed Technology

Storm water attenuation
provided to thedownstream of thehydrological catchment.

Applicable Scale

Development or area scale. May be delivered as a single storage or multiple dispersed
storages across the development areas.

Potential Potable Water
Savings

NONE

Potential Discharge
Reduction

LOW - Reduced volume of
surface water discharge
through enhanced
evapotranspiration.

Combined storm water attenuation provided to thedownstream of the hydrological catchment, servicing
Old Oak Common and new build areas of Park Royal.

LOW- Reduced volume of surface water discharge
through enhanced evapotranspiration.

Potential Attenuation
Contribution

HIGH - Up to 100%
provided in dispersed or
single attenuation.

HIGH - Potential toprovide up to 100% of
required dispersed orcollective attenuation,
depending on spatial
availability.

Indicative Cost

HIGH - Estimated 3+% of
estimated construction
costs (£113,000,000)

LOW - Estimated 0-1% of estimated construction
costs (£28,000,000)

Spatial requirements

HIGH - Significant spatial requirements. However, this may be integrated withinlandscaping and delivered to provide multiple benefits for the urban aesthetics,
environment and community.

MaintenanceRequirements

MEDIUM - Litter/debris removal and cleaning, vegetation management, sedimentmonitoring and removal.

Regulatory and Public
Acceptability

MEDIUM - High quality design and delivery is required to prevent safety hazards andissues associated with eutrophication and undesirable aesthetics resulting fromfluctuating water levels. Determining responsibility for ongoing maintenance may
present challenges.

Flexibility andscalability

MEDIUM - Site levels would need to be carefully considered in order to facilitate
natural surface drainage pathways over as much of the site as possible. Physicalbarriers, such as infrastructure routes, would need to be navigated.

Carbon intensity

LOW - delivery of associated green space may provide potential for carbon
sequestration.

Blue-green spaceprovided

HIGH - provision of blue- green space, with the potential to provide recreational andamenity benefit, habitat for biodiversity, improved air and water quality andmicroclimate benefits.

Climate Resilience

MEDIUM - Provision of attenuation to assist in mitigating the impacts of climate changeon drainage. Capacity and exceedance design for increased storm intensity and safe
containment of flooding will be required.

Surface water quality

HIGH - Improved surface water quality through attenuation, sedimentation andbiological uptake of contaminants.

46

HIGH - Potential toprovide up to 100% of
required dispersed orcollective attenuation,
depending on spatial
availability.

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5.12

Integrated W ater Management Strategy

Stormwater Recycling

5.12.1.1 Stormwater treatment and harvesting fromurban catchment areas can provide analternative water source to offset centralised
potable demands, while reducing storm flow thesewer system. Stormwater picks up a wide
range of pollutants from the surfaces it flows off
and its quality is highly variable over time.
Typical storm water treatment generally
involves some form of filtration to capture thesuspended solids and pollutants attached to thesediments followed by disinfection. This is often
provided using vegetated systems, designed touse natural, passive processes for filtering
pollutants. Supply is variable due to thedependence on rainfall patterns, with significant
storage infrastructure likely to be required to
manage this, and a back-up water supply
Figure 25 - Stormwater harvesting and reuseconnection may additionally be required forparticularly dry periods. Water could be supplied
for outdoor irrigation use, for specific industrial process or for non-potable uses within residences andbusinesses.

5.12.1.2 This infrastructure would need to be carefully planned in conjunction with the proposed surface waterdrainage network and masterplan layout with spatial constraints likely to impact upon feasibility of
infrastructure delivery in the high density development. Detailed feasibility investigation would
additionally be required to determine the exact extent of the hydrological catchment able to contribute,given the spatial fragmentation of the area, due to dividing infrastructure including rail lines and thecanal. Significant underground infrastructure could be required to manage this, and maximise thecollection of available flows across the Opportunity Areas. Wormwood Scrubs may present an
opportunity for installation, due to potential spatial availability and location to the downstream of the newbuild catchment.
5.12.1.3 Area-scale retrofit of stormwater recycling within retained areas is unlikely to be immediately feasible,
due to spatial constraints and the lack of a non-potable distribution network; however, localised solutions
for irrigation or outdoor use may be feasible, in conjunction with delivery of surface water attenuation
infrastructure. Any new redevelopment or refurbishments could be connected to non-potable recycled
supplies provided for adjacent new build areas.
5.12.1.4 Potable re-use of collected storm water may also eventually be possible, with ongoing technologicaladvancements in this area. Long term research, monitoring and assessment of treated water quality
would be required in order to deliver this.

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Core Objectives

Characteristics

Park Royal - Retained

Potential Potable
Water Savings
Potential
Discharge
Reduction
Potential
Attenuation
Contribution

Sustainability

Feasibility

Indicative Cost

Old Oak Common

Downstream storm water harvesting system incorporating
wetland secondary treatment train, disinfection, balancing
storage and re-distribution for non-potable re-use.

AssumedTechnology

Applicable Scale

Park Royal - New Build

A non-potable network
solution is unlikely to be
immediately feasible forretained areas of Park
Royal; however, newredevelopment or
refurbishments could beconnected to non-potable
recycled supplies, as
provided for new build
areas. Localised solutions
for irrigation may beachievable.

Likely to be most appropriate on an area wide or
development scale.

HIGH - Up to 21% reduction in potable demand (681 ML/year)

MEDIUM - Up to 17% reduction in total drainage discharge(681 ML/year)

VERY HIGH - Up to 100%, dependant on spatial availability.

MEDIUM - Estimated 1-2% of anticipated construction costs(£48,000,000)

Spatialrequirements

HIGH - Significant spatial requirements. However, this may be incorporated into urban
landscape to provide high quality public realm and opportunities for recreational space andamenity.

MaintenanceRequirements

HIGH - Litter/debris removal, cleaning, vegetation and sediment management. Ongoing
operational and energy requirements associated with treatment and distribution.

Regulatory andPublicAcceptability

LOW - Potential public perception issues with re-use of recycled storm water and potential for
regulatory barriers, depending on proposed end use.

Flexibility andscalability

LOW - Centralised system may make it more difficult to phase delivery. Upfront spatialplanning and rationalisation of levels and drainage pathways is essential.

Carbon intensity

HIGH - Ongoing energy and maintenance requirements for treatment and distribution.

Blue-green spaceprovided

HIGH - provision of green space, with the potential to provide recreational and amenity
benefit, habitat for biodiversity, improved air and water quality and microclimate benefits

ClimateResilience

LOW - Climate dependant water source, with associated large storage requirements and lessreliability of supply.

Surface water
quality

HIGH - attenuation, water quality treatment and removal of urban runoff from the sewer andsurface water systems.

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5.13

Integrated W ater Management Strategy

Wastewater Recycling

5.13.1.1 Wastewater recycling comprises collection ofwastewater flows (including both blackwater andgreywater), treatment to a high standard, anddistribution for non-potable re-use. Wastewatercontains a high concentration of contaminants thatcan present risks to human health. As such,significant processing is required to treat flows to ahigh quality in order to adequately manage thisrisk. These treatment processes can be costly andenergy intensive, including advanced water
treatment technologies, such as microfiltration,
reverse osmosis or advanced oxidation, although
new processes such as electrocoagulation andfood chain reaction may provide more costeffective solutions (see section 10).

Figure 26 - Wastewater recycling

5.13.1.2 A package wastewater treatment plant could be supplied to collect and treat wastewater flows from the
new development areas, and re-supply fit for purpose non-potable water for re-use. Spatial requirements
for the new plant would need to be considered, along with management of any potential visual, noise orodour impacts. Ideally, a modular, scalable system could be installed, to allow for gradual expansion
with delivery of the development.
5.13.1.3 Treated wastewater is available in significant quantities, and has the potential to provide a highly
consistent and reliable supply stream to reduce demands on mains water and waste water discharge.
Appropriately treated wastewater may be used for irrigation, process uses, or non-potable reuse within
homes and businesses. This could also be exported outside the Opportunity Areas for use insurrounding developments.
5.13.1.4 Currently, direct recycling of wastewater is unlikely to be appropriate due to the numerous barriers
necessary to mitigate the health risks associated with water quality. However, in the longer term, thismay be possible, with ongoing technological advancements in this area and a changing socioinstitutional climate. Under this scenario, wastewater has the potential to offset almost all potabledemand, presenting an important advantage in terms of flexibility for future technological advancement(as compared to the other recycling options).

5.13.1.5 Innovation in Waste Water Recycling
5.13.1.6 Hydro Industries Electrocoagulation – Electrocoagulation is a technology that separates dissolved
particles from water and has demonstrable application in the oil and gas industry where it is usedprimarily for remediation. As the technology is developing it is becoming increasingly viable for use indomestic waste water treatment. It works by passing a low voltage current through waste water toproduce an extra hydrogen molecule which destabilises the charge holding heavy metals, organics andinorganics in solution. These then separate and can be mechanically removed.
5.13.1.7 Hydro Industries have developed a modular electrocoagulation plant, each processing in the region of
1,400m3 – 2,900m3 per unit a day depending on discharge quality required. The modular design meansthat the plant can be scaled as the development demands change from construction through operationand decommissioning. Alternatively it can form part of a very localised distributed system. The process
is effective at removing a wide range of contaminants and has a number of applications for treating
industrial waste water. As such, there could be potential for location in Park Royal. Hydro Industries
have also used electrocoagulation to produce potable drinking water in India and area currently working
with Welsh Water, Affinity Water, Wessex Water, United Utilities and Northumberland Water to trail theuse of electrocoagulation, primarily for solids-metal removal as part of the drinking water treatment
process.

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Figure 5-13 - Hydro Industries, HydroCurrent (Source Hydro Industries)

5.13.1.8 Living Machine® - The Living Machine® such as the one used at the headquarters of San Francesco,
mimics wetland ecology to treat waste water. The waste water passes through a series of ‘wetland cells’
which contain filtration media that promote the growth of organisms in ‘micro-ecosystems’ that remove
the nutrients and solids from the waste water. This system is known as a tidal system and the wetland
cells are routinely flooded and drained several times a day. These systems can be integrated intogreenhouses and the public realm as all the treatment processes occur below the wetland surface withattractive wetland vegetation at the surface.
5.13.1.9 Organica Food Chain Reactor (FCR) – The FCR is an advanced variation of the traditional activatedsludge approach to waste water treatment plant. Designed to provide more localised treatment of waste
water for an urbanising world, Organica’s FRC approach has been shown to reduce the physicalfootprint by 50%, energy demand by 30% and waste sludge by 35% when compared with traditional
waste water management. The reduction in required size, associated construction costs and the waste
sludge generated is down to an increase in density and diversity of the biomass used to breakdown thesolid waste by creating a more varied ecosystem. This is achieved by introducing vegetation andengineered biomedia into the reaction tanks. The root system of the planting and the biomedia create abiofilm habitat that can accommodate about four times the number of organisms to digest andmetabolise the waste. In turn, these microbes and bacteria are predated upon and metabolised by larger
organisms, as the food chain reaction is activated.
5.13.1.10 For the organisms in any activated sludge process they need to be able to absorb oxygen from thewaste water. As such, aeration of the waste water is one of the biggest operational costs of activatedsludge treatment. The FCR reduces energy demand by significantly reducing the aeration requirements
in two ways. Firstly, the structure of the root system and biomedia creates a biofilm with a much greater
surface area, allowing oxygen to be absorbed more efficiently. Because the root structure and biomedia
and therefore biomass are in fixed locations, as opposed to floating within the waste water, the waste
water has less particulate matter in it. This in turn allows the oxygen from the aeration to be dissolved
more efficiently as well.
5.13.1.11 By locating and treating water close to where it is generated also reduces the energy and costs
associated with pumping waste water over large distances. It also offers the potential for reuse as a
non-potable water source and there are a number of FCR plants in China which utilise the treatedsewage effluent to flush toilets.
5.13.1.12 The FRC can be located within urban areas because it is odour free and has the appearance of an
attractive botanical greenhouse. Although the physical buffer zones can be less than 20m, the attractive,
planted nature of the plant also means that the psychological barriers often associated with waste water
treatment are removed. The replacement of the South Pest WWTW with an 80,000m3/day FRC
unlocked a large area of development land previously taken up by the former plant and buffer area.

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3

Figure 5-14 - Organica’s 80,000m plant in South Pest (source: Organicawater.com)

3

Figure 5-15 - 2,000m waste water treatment plant, Jakata (source: Organicawater.com)

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Core Objectives

Characteristics

Park Royal - Retained

Potential Potable
Water Savings
Potential
Discharge
Reduction
Potential
Attenuation
Contribution

Sustainability

Feasibility

Indicative Cost

Old Oak Common

Package wastewater treatment plant to treat incoming
sewage, incorporating advanced water treatment, andredistribution for non-potable reuse within homes andbusinesses.

AssumedTechnology

Applicable Scale

Park Royal - New Build

A non-potable network
solution is unlikely to befeasible for retained areasof Park Royal; however,
new redevelopment or
refurbishments could beconnected to non-potable
recycled supplies, as
provided for new build
areas.

Area scale. Building or development scale wastewater
recycling systems are also possible; however, greywater
recycling is likely to be more appropriate in this instance.
HIGH - Up to 21% reduction in potable demand (681ML/year)

MEDIUM - Up to 17% reduction in total drainage discharge(681ML/year)

NONE

LOW - Estimated 0-1% of anticipated construction costs(£44,000,000)

Spatialrequirements

MEDIUM - Spatial requirements associated with infrastructure for wastewater collection,
treatment, storage and distribution.

MaintenanceRequirements

HIGH - Ongoing operational and energy requirements associated with treatment anddistribution.

Regulatory andPublicAcceptability

LOW - Potential public perception issues with re-use of recycled storm water and potential for
regulatory barriers, depending on proposed end use. Potential community concerns
associated with potential for noise and odour (these can be mitigated)

Flexibility andscalability

MEDIUM - May be more difficult to phase delivery in line with development; however, newtechnologies have the potential for innovative designs with modular composition.

Carbon intensity

HIGH - Ongoing energy and maintenance requirements.

Blue-green spaceprovided

LOW - Minimal provided through traditional design. However, new technologies may provide
opportunities for use of green, biological treatment processes.

ClimateResilience

HIGH - Highly reliable supply with limited climate dependence.

Surface water
quality

LOW - Marginal benefit through reduced flows to sewer, with reduced associated impact on
downstream receiving waterbodies.

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5.14

Integrated W ater Management Strategy

Expansion of the Counters Creek Flood Alleviation Scheme

5.14.1.1 The public sewer system in central London wasconstructed to accommodate foul water (from toilets,
showers and sinks) as well as surface water (from roofs
and driveways) in the same pipe. The sewers are therefore
called “combined” sewers as they accommodate a
combination of both foul and surface water flow.
5.14.1.2 The available capacity of these sewers varies significantly
depending on precipitation. During heavier rainfall eventsthe local sewers as well as the interceptor sewers run out
of capacity and begin to surcharge. To prevent properties
from flooding during heavy rainfall a network of deep“storm relief” sewers were constructed over time. Thesesewers take excess flow from the interceptor sewers andrelay this flow directly to the River Thames via a combined
sewer overflow (CSO). These direct connections into the environment are going to be addressed by theconstruction of the Thames Tideway Tunnel which will significantly improve the river water quality by
preventing discharge from the storm relief sewers directly into the environment.
5.14.1.3 The Counters Creek programme includes the construction of a new storm relief sewer to prevent
property flooding in Hammersmith, Fulham, Kensington and Chelsea where significant property flooding
has been observed. This solution will allow excess storm flows in the interceptor sewers to spill into it,
and will eventually connect to the Thames Tideway Tunnel to ensure that we do not increase combined
sewer overflows into the River Thames.
5.14.1.4 Any growth and redevelopment opportunities will increase the dry weather flow into the public sewer
system. Development at Old Oak Common can therefore not be accommodated into the new Counters
Creek storm relief sewer as that has the potential to initially yield a discharge of dry weather flow directly
into the environment through a combined sewer overflow or be incorporated into the flow that theThames Tideway Tunnel needs to accommodate. The use and operation of all combined sewer
overflows as well as the Thames Tideway Tunnel are regulated by the Environment Agency and a dry
weather flow discharge from growth would be a breach of these discharge permits.
5.14.1.5 As such, this is not considered to be a feasible option to manage the increase in foul water flow from Old
Oak Common and Park Royal. The preferred approach is to returning capacity in the local andinterceptor sewers by removing surface water, using SuDS techniques.

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Sustainability

Feasibility

Core Objectives

Characteristics

Park Royal - RetainedPark Royal - New Build

Old Oak Common

AssumedTechnology

Expansion of the Counters Creek Flood Alleviation Scheme to provide additional conventional
drainage capacity across the Opportunity Areas.

Applicable Scale

Regional scale solution

Potential Potable
Water Savings

NONE

Potential
Discharge
Reduction

NONE

Potential
Attenuation
Contribution

LOW - Some in-system storage could be provided for stormwater attenuation

Indicative Cost

VERY HIGH - The cost for this option is unknown; however, likely to be significantly in excess
of any of the other options described.

Spatialrequirements

LOW - No surface spatial requirements; however, significant surface construction footprints
would likely be required.

MaintenanceRequirements

MEDIUM - Conventional drainage system maintenanceRegulatory andPublicAcceptability

LOW - Potential breach of Environment Agency discharge conditions for CSOs and likelihoodof highly disruptive construction at significant cost.

Flexibility andscalability

LOW - Reinforcement of centralised infrastructure.

Carbon intensity

HIGH - operational emissions associated with pumping flows out for treatment; however, ahighly intensive construction process is likely to be required.

Blue-green spaceprovided

NONE

ClimateResilience

LOW - Provides increased capacity for increased rainfall intensity; however, reinforces thehydrological impacts of conventional drainage systems.

Surface water
quality

NONE - May contribute to combined sewer overflows

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6

Water Management Options

6.1

Strategy Formulation

6.1.1.1

In order to address the significant challenges of the Opportunity Area development, a suite of measures
will be required to be delivered in combination. The majority of measures introduced in Section 5 arescalable and complementary, or address separate aspects of the urban water cycle. Furthermore,
several of these measures should be delivered within the development as standard best practice; whilst
for others there are various available options/approaches.

6.1.1.2

Table 6-1 below provides an overview of how the various measures could t be alternatively combined, tocreate different water management scenarios. Six scenarios have been generated, representing
different options and combinations of the various strategy aspects, as further discussed in the following
sections.

6.1.1.3

In order to meet the extensive challenges of the proposed development, all of these scenarios
incorporate the following components:
Achieving the maximum possible standards of demand management, by achieving the highest
current and future industry standards in water efficiency, utilisation of smart network technologies,
community engagement and targeted water efficiency retrofits and process improvements.
A cohesive integrated approach to manging surface water quality and quantity, including
attenuation, conveyance and discharge of runoff, across the development areas. The options
available for surface water management are discussed in Section 6.3, below.
A strategic approach to water recycling, considering non-potable use of water as a minimum, withallowance for future implementation of potable water recycling. Options available for water re-use
are discussed in Section 6.4, below.

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Demand Management

Table 6-1: Water Management Scenarios

Maximising demand management through water efficiency,
community engagement and utilisation of smart network
technologies.

Stormwater Management Options
Water Recycling Options

Strategy Components

Green source control features to manage the quality and quantity ofsurface water generated on site.

56

Streetscape strategic SuDS network providing conveyance,
filtration and attenuation of stormwater from development plots toattenuation or discharge locations.

Residualattenuation
provided
underground

Residualattenuation
provided
above ground

Residualattenuation
provided
underground

Residualattenuation
provided
above ground

Residualattenuation
provided
underground

Residualattenuation
provided
above ground

Building scale greywater
recycling

Strategic scale wastewater
recycling

Strategic scale stormwater
recycling

Scenario 1

Scenario 3

Scenario 5

Scenario 2

Scenario 4

Scenario 6

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6.2

Multi-Criteria Analysis

6.2.1.1

In order to evaluate the various options for the surface water management and water recycling
components, a process of Multi-Criteria Analysis (MCA) has been undertaken, using the performance
criteria defined in Section 5.2. Each of the formulated strategy options has been selected to maximise
the achievement of the core project objectives as far as possible. The qualitative assessment of each of
the feasibility and sustainability criteria were translated into a comparative score between 0 and 3, and a
relative weighting applied to each criteria, as shown in Table 6-2 below. These weightings have been
defined to be reflective of discussions held with key project stakeholders and representative of theoverall priorities for water management across the Opportunity Areas. The cumulative scores for eachmeasure were then compared to determine the order of preference between the different measures foreach function.

Sustainability
50%

Feasibility
50%

Table 6-2: Weightings applied to each performance criteria during the Multi-criteria analysis

Performance Criteria

Weighting

Indicative Cost

25%

Spatial requirements

20%

Maintenance Requirements

20%

Regulatory and Public Acceptability

10%

Flexibility and scalability

25%

Carbon intensity

20%

Blue-green space provided

30%

Climate Resilience30%

Surface water quality

20%

6.3

Stormwater Management Options

6.3.1.1

Across the Opportunity Areas, it is essential that a cohesive and integrated approach is adopted toeffectively manage surface water quality and quantity from source generation to ultimate discharge,
including the following aspects:
Plot and development scale source-control measures, to control the quality and quantity of surface
water runoff generated on site. This will prevent inundation of strategic surface water conveyancenetworks and facilitate the management of water quality throughout the surface water treatment
train.
A streetscape surface water drainage network for conveyance of runoff from source to ultimate
discharge, while providing attenuation and water quality treatment.
Ultimate discharge of runoff (either to sewers, surface waterways or recycled end use).

6.3.1.2

Within the stormwater management strategy, attenuation storage must be provided in order to achieve
Greenfield runoff rates, which is central to the viability and vision of the overall development. A number
of approaches have been highlighted to achieve this, including:Green, surface source control measures, including permeable surfacing, bio-retention, swales andsurface water storages;
Green roofs;
Storage provided within the strategic SuDS network; Underground attenuation tanks;
Downstream above ground stormwater retention

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6.3.1.3

The results of the MCA for these measures is shown in Table 6-3 and Table 6-4 and described in thefollowing sections.

6.3.2

New Build Areas

6.3.2.1

For the new build areas within Old Oak Common and Park Royal, the MCA indicates a preferential
hierarchy of measures to achieve the required storage, as described:

6.3.2.2

1)

Green Roofs have been assessed as the most preferential means of providing attenuation, due totheir limited spatial requirements and the potential to provide multiple benefits for attenuation, water
quality, amenity and green space. Preliminary calculations indicate that these have the potential toprovide up to 20% of required attenuation (which could be improved through the incorporation of
integrated water storage). These features should be maximised on all development sites.

2)

Following this, on-plot green source control measures such as green walls, bio retention systems,
swales and surface ponds have been assessed as the next most preferential means of providing
attenuation and should be maximised on all sites. Additionally, permeability should be maximised
wherever possible, with a minimum recommendation of 40% of ground level permeability,
preferably through vegetated surfacing.

3)

The delivery of a strategic surface water drainage network will additionally provide a variable
volume of attenuation, (up to 20%, depending on scale and extent); although it is emphasised thatcapacity must be sufficient for streetscape drainage and conveyance of residual flows from plot toany downstream storages.

Each of these measures should be maximised as far as possible within the Opportunity Areas, as
reflected in the Scenario summary presented in Table 6-1 above. However, due to the spatialconstraints of the development and the significant attenuation volumes required, these measures will beinsufficient to achieve the desired volumes. As such, residual storage would need to be provided
through either:
4)

Strategically dispersed above ground storages, linked to the surface water network, wherever
spatially feasible (scenarios 2, 4 and 6).

5)

Residual storage provided using underground attenuation tanks, preferably installed within thedevelopment plots (scenarios 1, 3, 5).

6.3.2.3

In general, below ground storage is considered the least preferable option for providing storage as
opposed to the other blue-green infrastructure solutions discussed, due to the limited additional benefit
and from competing pressures for underground space from other subterranean uses. For this reason,
Scenarios 2, 4 and 6, presented in Table 6-1 are deemed to be more preferable than Scenarios 1, 3 and5.

6.3.2.4

However, it is acknowledged that below ground storage may be the most practical means of achieving(at least some of) the required attenuation volumes, particularly within development plots, which are
likely to be extremely spatially constrained. This provision of sufficient storage within plots is required inorder to manage water quality and avoid inundation of downstream conveyance networks.

6.3.2.5

Conversely, above ground storages are likely to be more practical when provided downstream of theplots, within areas of the public realm or open green space, such as for example, Wormwood Scrubs.

6.3.2.6

Therefore, a balance of on-plot to downstream storage is required, reflecting the desirability to manage
surface water at the surface wherever possible, whilst recognising the spatial constraints of thedevelopment proposals.

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The location and provision of attenuation storages will need to be carefully designed in conjunction withthe strategic conveyance network, and will be strongly influenced by the natural hydrological catchments
and stormwater discharge location. It will also be important to consider where ponding of surface water
occurs naturally as indicated in the high risk flood areas (see section 3.4). There is opportunity to workwith the natural flow of surface water to promote above ground storage in locations within themasterplan to alleviate surface water flood risk. There are several options available for discharge of thecollected, attenuated, treated and conveyed stormwater, including:Discharge to the combined Counters Creek sewer system;
Discharge to the Grand Union Canal;
Discharge to the Mogden surface water catchment;
Direct discharge to the River Brent;
Discharge to an underground aquifer for groundwater recharge;
Harvesting and reuse for recycling, as discussed below

6.3.2.8

In line with the sustainable drainage hierarchy, recycling of surface water (as discussed below) or
discharge to surface water bodies is considered to be preferable. The Grand Union Canal, in particular,
is likely to present a beneficial discharge option; however, greater hydrological information, consultation
and analysis would be required to confirm suitability.

6.3.3

Retained Areas

6.3.3.1

Within the retained areas of Park Royal, the same preferential hierarchy of attenuation options ishighlighted. However, it is recognised that retrofit may be more reliant on opportunities arising throughthe incremental renovation and redevelopment across the area.

6.3.3.2

It is recommended that targeted and opportunistic SuDS retrofits are undertaken within properties,
particularly including retrofit of green roofs and blue-green infrastructure. Similarly, retrofit of SUDS
should be undertaken within the existing streetscape wherever spatially possible, aiming to remove andattenuate as much surface water as possible from the combined sewage system. In particularly, water
management infrastructure should be integrated within delivery of newly planned green space andplanned streetscape regeneration. The high risk flood areas indicated in Section 3.4 of this report
indicate areas where SuDS systems could retrofitted to manage flows of water as well as provide
attenuation.

6.3.3.3

Within all redevelopments and property refurbishments, attenuation storage to achieve Greenfield rates
should be achieved, with a preference for green, surface SuDS measures. Similarly, incrementallyextended/altered plots should be preferentially discharged to the Grand Union Canal or River Brent,
provided there is appropriate management of water quality and quantity for this to be achieved without
exacerbating flood risk or resulting in detriment to waterway health.

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Table 6-3: Multi-criteria analysis summary for stormwater management measures in new build areas. The defined weightings have been applied to the score for each criterion to indicate a cumulative score
and comparative measure ranking.

Criteria

Downstream Surface
Attenuation

SuDS Source Control

Green Roofs

Underground
Attenuation

Strategic SuDS
Networks

4

2

1

5

3

Capital Cost

Operational and maintenancerequirements
Deliverability

Space Requirements
Regulatory and Acceptability
Challenges
Flexibility and scalability

Carbon Intensity

Blue-green space provided
Sustainability
Climate Resilience

Surface water quality
Measure Ranking

KEYHigh benefit
Medium benefit
Low benefit
No benefit

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Table 6-4: Multi-criteria analysis summary for stormwater management measures in retained areas. The defined weightings have been applied to the score for each criterion to indicate a cumulative score
and comparative measure ranking.

Criteria

Downstream Surface
Attenuation

SuDS Source Control

Green Roofs

Underground
Attenuation

Strategic SuDS
Networks

4

2

1

5

3

Capital Cost

Operational and maintenancerequirements
Deliverability
Space Requirements
Regulatory and Acceptability
Challenges
Flexibility and scalability

Carbon Intensity

Blue-green space provided
Sustainability
Climate Resilience

Surface water quality
Measure Ranking

KEYHigh benefit
Medium benefit
Low benefit
No benefit
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6.4

Recycling Options

6.4.1.1

The installation of a strategic non-potable water recycling solution for the development areas is essential
to offset potable demand and reduce discharges. As illustrated in the water balance section of thisreport, it has been estimated that non-potable water recycling can achieve a minimum expected
reduction in water demand of approximately 20%, with greater savings possible through outdoor use ofwater for public irrigation, as well as use to meet specific commercial and industrial process demands.

6.4.1.2

Additionally, potable reuse of reclaimed water supplies is being increasingly considered globally, withongoing technological advancement in water treatment, allowing for greater water quality outcomes andmitigation of risk. Given the significant timescales proposed for the development, it is anticipated there
will have been significant advances in this area, stimulated by increasing global awareness of climatechange and resource shortage. Furthermore, de-regulation and increased public awareness of watersupply issues are anticipated to create a more favourable climate for delivery. Therefore, flexibility for
future potable use of recycled water supplies should additionally be built into the overall water
management strategy for the Opportunity Areas.

6.4.1.3

The various options for water recycling have been assessed using a multi-criteria analysis, highlighting
the varied benefits and costs associated with each option. The outcomes of this MCA are shown in
Table 6-5 and described below.

6.4.2

New Build Areas

6.4.2.1

Several options for water recycling are present, and could be harnessed to effectively augment
centralised water supplies. These are described in order of assessed preference below:
1) Wastewater Recycling for non-potable use (Scenarios 3 and 4)
This has been selected as the preferential option for delivering a strategic non-potable solution.
Compared to stormwater recycling, wastewater recycling has a higher climate resilience andassociated certainty of supply. This is also likely to present less spatial challenges, with a smaller
anticipated spatial footprint, lower required water storage, and less reliance on overlandhydrological connectivity. Furthermore, a range of innovative systems are entering the market,
providing designs which are increasingly compact, scalable, sustainable and able to be
aesthetically integrated within the urban form.
Importantly, wastewater recycling is also considered to allow for a greater degree of flexibility inimplementation, as the greater volume of available flows means that a recycled supply could be
used to offset potable demands to a more substantial degree, if consideration of appropriate nonpotable end uses is expanded (for example including laundry use), or if future technological andsocio-institutional advancement allows for potable use of recycled supplies. Additionally, utilisingwastewater for non-potable supplies conserves an opportunity to utilise higher raw quality rainwatersupplies for potable use (e.g. from rainwater harvesting from clean roofs). Therefore, if
appropriately delivered, investing in the initial infrastructure for wastewater collection, treatment andredistribution may allow greater flexibility for increased future use.
2) Stormwater Recycling (Scenarios 5 and 6)
Stormwater recycling is indicated to be an alternative approach to providing a network-based nonpotable supply solution. However, climate dependence is a primary disadvantage of this as asupply option, with the requirement for significant balancing storages to manage seasonal
fluctuation, and back up centralised supplies for dry years. Additionally, more detailed assessmentand modelling is required to confirm the feasibility of this option, to gain greater certainty into the
expected flows, and the ability to convey surface flows across the different areas of thedevelopment (given the presence of significant constraining infrastructure) which may limit theeffective catchment area.
Additionally, currently the extent to which centralised water demand can be offset is limited by the
non-potable demand. However, in the event that future potable use is considered, then this will

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become limited by the availability of potable supplies. In this scenario, stormwater recycling will
have limited capacity to support wider uses within the development.
3) Greywater Recycling (Scenarios 1 and 2)
Greywater recycling is indicated to be the least preferable option for non-potable reuse within thedevelopment. This is because the preliminary costing undertaken indicates that there are capitaland operational efficiencies to be gained by delivery of a more centralised, network based solution
to recycling. This is also likely to be more energy efficient than operation of a number of isolated,
plot scale recycling options.
However, greywater nonetheless presents a highly beneficial option to effectively managing watersupplies within the Opportunity Areas. Furthermore, it is recognised that there are a number ofchallenges inherent in the achieving the delivery and ongoing operation of a third pipe network. If
this becomes infeasible, then greywater provides an advantageous plot-based solution to water
recycling.
6.4.2.2

Roofwater recycling has not been included as an individual recycling option in the MCA as it does notmeet the core project objectives. This is because the limited rooftop catchments will not provide
sufficient flows to meet the non-potable demand within the high density development. Roofwater
imported from large rooftop catchments within Park Royal could be collected centrally and utilised tomeet this demand; however, this would require complex retrofit of pipework, with associated cost andfeasibility considerations, and is considered to provide limited additional benefit over stormwater
recycling.

6.4.2.3

However, if potable water recycling is considered in the short term, roof water presents a particular
opportunity, as a source with particularly high quality. Allowance for potable augmentation would meanthat harvested water could be collected, treated and directly mixed with centralised supplies, avoiding
the difficulties associated with piping supplies across the catchment boundaries. If considered, it isrecommended that stringent water quality monitoring be implemented, over a validation period, during
which water supplies could initially be utilised for non-potable use. Following validation, water could bedirectly supplied to the potable network. This would be delivered in combination with a non-potablewastewater recycling system for optimal benefit. New build properties in Park Royal may provide
particular opportunities for the delivery of pilot systems (due to more favourable catchment and demand
characteristics).

6.4.2.4

Whilst a preferred option has been suggested, it should not be assumed that only a single, uniqueapproach to recycling should be implemented. A variety of stormwater conveyance and storage
infrastructure will be required across the development, which may be harnessed to provide more
appropriate localised opportunities for green space irrigation, with lower required water treatment, andtherefore a lower cost of supply. Similarly, plot-scale greywater and rainwater (or combined greywater
rand rainwater) recycling may be appropriate for properties where connection to a distribution network is
not feasible or advantageous. In the long term, the overall objective should be to provide a diverse
portfolio of fit-for-purpose centralised and decentralised supply solutions, allowing greater operational
flexibility and system resilience.

6.4.3

Retained Areas

6.4.3.1

Within existing areas of Park Royal, retrofit of dedicated non-potable internal distribution pipework is
unlikely to be feasible, which will limit the applicability of most recycling options. However, retrofit ofrainwater harvesting systems is likely to be feasible at several properties, due to large available roof
catchments, and the likelihood of specific, high demand water uses which could be met with non-potablesupplies. In order to maximise benefit, this is likely to require a targeted approach to retrofit, based on
the individual water use characteristics. Additionally, as regeneration of the area is gradually stimulated,
all new properties should be installed with an alternative means of water supply. This may be throughconnection to an adjacent non-potable network, if feasible, or through delivery of a localised rainwater or
greywater supply (depending on the flow characteristics of the property).

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Table 6-5: Multi-criteria analysis summary for water recycling measures in new build areas. The defined weightings have been applied to the score for each criterion to indicate a cumulative score andcomparative measure ranking.

Criteria

Stormwater Harvesting fornon-potable re-use

Wastewater Recycling for nonpotable reuse

Greywater Recycling for non-potable
reuse

2

1

3

Capital Cost
Operational and maintenance requirements
Deliverability

Space Requirements
Regulatory challenges and Public AcceptanceFlexibility and scalability
Blue-green space provided

Carbon intensity
Sustainability
Climate Resilience

Surface water quality
Measure Ranking

KEYHigh benefit
Medium benefit
Low benefit
No benefit

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6.5

Scenario Comparison

6.5.1.1

The key available options for water management are primarily associated with the new build areas,
relating to the primary recycling option to be implemented (wastewater, stormwater or greywater) andthe balance of residual attenuation storage provided (on-plot underground attenuation or downstream
above ground storage), reflecting the six key scenarios presented in Table 6-1.

6.5.1.2

These aspects are also interdependent. For storm water recycling, greater capacity of the conveyancenetwork would be required, given the requirement for all flow to be centrally collected for re-use and agreater volume of downstream surface attenuation would be provided. Wastewater and greywater
recycling are, however, less dependent on the surface water network, allowing dispersed disposal towaterways, sewers or for localised reuse.

6.5.1.3

A summary description of each of the six scenarios is provided in Table 6-6 below, including theadvantages and disadvantages of each. Although the type and extent of infrastructure measures todeliver the key objectives varies within each scenario, there are common water management options
which make up the base of all scenarios. These common features are:Achieving the highest standards of water demand management, through installation of highspecification water efficient fixtures and fittings and use of smart network and metering technologies;
Use of on plot source control SuDS measures such as green roofs on buildings.
Management of storm water runoff within a connected network of strategic streetscape SuDS
located at public open areas, streets and roads.

6.5.1.4

Conceptual diagrams of options 2, 4 and 6 are also presented in Figure 6-1 to Figure 6-3 for illustrative
purposes (it should be noted that the spatial configurations indicated have not been confirmed in thesefigures).

6.5.1.5 Preferred solution
6.5.1.6

The identification of six potential option strategies provides a degree of flexibility for the overall Strategy
prior to developing a preferred solution in detail. However, using the outcomes from the MCA process, it
is possible to highlight the currently preferred solution based on the score against the Strategy’s key
performance indicators.

6.5.1.7

The MCA scoring has indicated a preference towards above ground attenuation of stormwater wherever
possible due to the significant potential for the creation of multi-functional, multi-beneficial open space
and the greater scope for flexibility around where attenuated water could eventually be discharged. It
would allow options for the use of the River Brent or the GUC to be used for additional storage where
feasible. This option also allows for cost efficiencies (both build costs and operational costs) through theprovision of strategic storage solutions and SuDS networks.

6.5.1.8

The MCA also demonstrated a preference for wastewater recycling as a strategic water reuse solution
for non-potable demand. Compared to the site based greywater recycling option, wastewater recycling
provides both build and operational cost efficiencies through provision of area-wide strategic
infrastructure such as a centralised treatment facility and area-wide piped network distribution system. It
also provides a more climate resilient source of non-potable supply as wastewater generation isrelatively constant through the year compared to reliance on storm water recycling. Lastly, it provides
flexibility for storm water to be used in the future for other noon-potable uses within the home, or evenpotable use from clean sources such as roof runoff.

6.5.1.9

Scenario 4 combines these preferred storm water management and water re-use options and istherefore indicated to be the preferred Scenario. Section 0 sets out in more detail the key features of thepreferred strategy option.

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Table 6-6: Summary of strategy scenarios, including pros and cons

Scenario

Scenario Description

1

Residual storm water runoff is managed by a
mixture of some above ground SuDS attenuation
storage and use of underground tanks provided atsite level. To reduce overall demand further, allnon-potable demand for new development is met
through greywater recycling units provided at site
level.

No strategic scale infrastructure
required – ease of deliverability andphasing.
Climate resilient supply of recycledwater for non-potable demand.
Future flexibility for use of storm
water for other non-potable orpotable demands.

Minimal provision of multibeneficial open spaces
Less efficient in terms of buildand operational costs for bothstorm water management andwater reuse elements

This scenario focuseson ease of deliverability
but is less cost efficientand also provides less
opportunity for thecreation of multibeneficial space

2

Residual storm water runoff is managed largely
using above ground attenuation storage areas
which are either dispersed through strategic
available space within the opportunity areas and/or
at a centralised storage location (to be identified);
minimal storage is provided by undergroundattenuation tanks. As with scenario 1, to reduceoverall demand, all non-potable demand for new
development is met through greywater recycling
units provided at site level.

Creates opportunity for multifunctional open space throughprovision of surface water SuDS.
Climate resilient supply of re-cycledwater for non-potable demand.
More straightforward delivery of onsite water re-use option.
Future flexibility for use of storm
water for other non-potable orpotable demands.
More efficient in terms of build andoperational costs for area-widestorm water management option.

Significant amount of open
space required to deliver
preferred storm water
management
More challenging delivery ofstrategic storm water
management which could
affect phasing
Less efficient in terms of buildand operational costs forwater re-use option

This scenario balancesdeliverability against
cost efficiency, and also
provide multi-beneficial
above ground water
storage measures.

3

As with Scenario 1, residual storm water runoff ismanaged by a mixture of some above ground
SuDS attenuation storage and significant use ofunderground tanks provided at site level. To
reduce overall demand, all non-potable demand for
new development is met through recycling ofwastewater from development at a central
treatment unit and provided to buildings through a
dedicated area-wide pipe distribution network.

More straightforward delivery of onsite storm water management option
Climate resilient supply of re-cycledwater for non-potable demand.
Future flexibility for use of storm
water for other non-potable orpotable demands.
More efficient in terms of build andoperational costs for area-wide reuse management option.

Minimal provision of multibeneficial open spaces
More challenging delivery ofstrategic re-use option which
could affect phasing
More intensive treatment
required for re-use stream ofwater

This scenario balancesdeliverability against
cost efficiency, but
provides less
opportunity for thecreation of multibeneficial space.

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Advantages

Disadvantages

Summary

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Scenario Description

4

As with Scenario 2, residual storm water runoff ismanaged largely using above ground attenuation
storage areas which are either dispersed throughstrategic available space within the opportunity
areas and/or at a centralised storage location;
minimal storage is provided by undergroundattenuation tanks. As with scenario 3, to reduceoverall demand, all non-potable demand for new
development is met through greywater recycling
units provided at site level.

5

As with Scenarios 1 and 3, residual storm waterrunoff is managed by a mixture of some above
ground SuDS attenuation storage and significant
use of underground tanks provided at site level.
To reduce overall demand, all non-potable demand
for new development is met through recycling ofwastewater from development at a central
treatment unit and provided to buildings through a
dedicated area-wide pipe distribution network.

6

As with Scenario 2 and 4, residual storm waterrunoff is managed largely using above groundattenuation storage areas which are either
dispersed through strategic available space within
the opportunity areas and/or at a centralised
storage location; minimal storage is provided byunderground attenuation tanks. As with scenario 5,
to reduce overall demand, all non-potable demand
for new development is met through recycling ofstorm water from development at a central
treatment unit and provided to buildings through a
dedicated area-wide pipe distribution network.

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Advantages

Disadvantages

Summary

Creates opportunity for multifunctional open space throughprovision of surface water SuDS.
Climate resilient supply of re-cycledwater for non-potable demand.
Future flexibility for use of storm
water for other non-potable orpotable demands.
More efficient in terms of build andoperational costs for area-widestorm water and water re-use
management option.

Significant amount of open
space required to deliver
preferred storm water
management
More challenging delivery ofstrategic storm water
management and re-use
option which could affectphasing

This scenario
maximises cost
efficiency, provision ofmulti-beneficial above
ground water storage
measures, and a more
resilient non-potabledemand source, but is achallenging scenario todeliver in terms ofphasing.

More straightforward delivery of onsite storm water management optionMore efficient in terms of build andoperational costs for area-wide reuse management option.

Minimal provision of multibeneficial open spaces
More challenging delivery ofstrategic re-use option which
could affect phasing
Less climate resilient water
re-use optionLess flexibility for future useof storm water for other nonpotable (or potential potable)
usesThis this scenariobalances deliverability
against cost efficiency,
but provides less
opportunity for thecreation of multibeneficial space, and aless reliable all yearround supply of nonpotable water

Creates opportunity for multifunctional open space throughprovision of surface water SuDS.
More efficient in terms of build andoperational costs for area-wide reuse management option.

More challenging delivery ofstrategic storm water
management and re-use
option which could affectphasing
Less climate resilient water
re-use optionLess flexibility for future useof storm water for other nonpotable (or potential potable)
usesThis scenario
maximises cost
efficiency, and provisionof multi-beneficial above
ground water storage
measures, but is achallenging scenario todeliver in terms ofphasing and offers lessresilience to drought
conditions and dry
periods.

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Figure 6-1 - Scenario 4 - Wastewater Recycling

6.5.1.10 Figure 6-1 illustrates Scenario 4, which has been selected as the preferred approach to integrated water management across the development areas. In this
scenario storm water runoff is treated and managed via attenuation, which is preferentially provided through on-plot and above ground blue green infrastructure, inline with the hierarchy specified in Section 6.3.2, with preferential discharge of managed stormwater to local waterbodies. To reduce overall demand, all nonpotable demand is met through wastewater recycling, with a single centralised treatment facility and an area-wide third pipe network to provide non-potable waterto new build areas. Further benefit may be provided through the installation of a pilot potable rainwater harvesting facility.

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Figure 6-2 - Scenario 6 - Stormwater Recycling

6.5.1.11 Figure 6-2 illustrates Scenario 6, which is an alternative approach to water management through the development. Storm water runoff is treated and managed via
attenuation, which is preferentially provided through on plot and above ground blue-green infrastructure, in line with the hierarchy specified in Section 6.2.1.
Collected, treated stormwater is used to offset potable demand across the development, with a centralised collection and treatment facility and an area-wide third
pipe network to provide non-potable water to new build areas.

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Figure 6-3 - Scenario 2 - Greywater Recycling

Figure 6-3 illustrates Scenario 2, which is an alternative approach to integrated water management across the development areas. Storm water runoff is treated andmanaged via attenuation, which is preferentially provided through on plot and above ground blue-green infrastructure, in line with the hierarchy specified in Section
6.2.1, and preferentially discharged to local waterbodies. To reduce overall demand, all non-potable demand is met through greywater recycling units, provided at aplot scale.

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7Strategy Overview

7.1.1.1

The preferred approach to integrated water management across the development site is conceptually illustrated in Figure 6-1. The key elements of this water management strategy are broadly summarised in Table 7-1 below:
Table 7-1 - Summary of preferred framework for Integrated Water Management across the Opportunity Areas

DemandManagement

Strategy Element

Demand management andwater efficiency

Old Oak Common and New Build Park RoyalAll properties constructed to the maximum possible standards in water and energy efficiency.

Targeted water efficiency retrofits and process improvements.

Delivery of smart water supply network solutions with real time monitoring of water use andquality.

Incentive schemes to encourage property owners to undertake retrofit.

Delivery of educational opportunities integrated within the development.
Plot and development scale
source-control measures, tocontrol the quality andquantity of surface waterrunoff generated on site
A streetscape surface waterdrainage network forconveyance of runoff

Accessible, intensive green or blue-green roofs installed on all new buildings.
Maximise permeable surfacing within all development plots and installation of green SuDS
systems, including bio-retention systems, retention ponds, swales, green walls and facades
to maximise surface storage and treatment of runoff.

Strategic interconnected network of roadside swales and green infrastructure to drain roads
and public spaces; conveying, attenuating and filtering storm water flows along the natural
catchment hydrology.

Surface Water Management

Provision of required storage in line with the following preferential sequence:
An attenuation storage
strategy, providing
attenuation to achieve
Greenfield Rates

Water Recycling

Strategic non-potable water
network

71

Maximise storage provision within blue-green roofs, green source control measures andstreetscape SuDS network.
Remaining attenuation volumes to be provided in strategically dispersed offsite above
ground storages where spatially feasible, in areas of open green space or public realm.
Residual volumes to be provided using underground attenuation tanks.

Discharge of runoff

Allowance for future
implementation of potablewater recycling

Park Royal - Existing

Appropriately attenuated and treated water should be preferentially discharged to existing
surface water bodies, including the Grand Union Canal. Further work and consultation will be
required to confirm whether this is feasible without resulting in additional flood risk, and to
confirm appropriate rates of discharge.
Delivery of a non-potable distribution network, with all buildings to be connected throughnon-potable distribution pipework.
Installation of a dedicated wastewater recycling system with advanced water treatment andnon-potable redistribution. If wastewater treatment is not deemed feasible, then installation ofa strategic stormwater or greywater harvesting solution should be pursued.

Installation of a pilot potable rainwater harvesting system with ongoing water quality
monitoring (initial non-potable use of harvested water may be beneficial during monitoring).
Capacity design of treatment plant such that future potable wastewater recycling may be
implemented.

All new build developments and refurbishments to achieve maximum possible levels of water
efficiency.
Targeted and opportunistic SuDS retrofitting within existing properties, particularly including retrofit ofgreen roofs and blue-green infrastructure.
All new build developments and refurbishments to include attenuation to achieve Greenfield rates,with a preference for green SuDS measures.
Retrofit of sustainable drainage systems within the streetscape wherever spatially possible, aiming to
remove and attenuate as much surface water as possible from the combined sewer system.
Integrating water management infrastructure within delivery of newly planned green space andplanned streetscape regeneration (including the planned enhancement of the Park Royal Centre).

Opportunistic and targeted retrofit of on-plot attenuation wherever spatially possible.
Investigate land acquisition for strategic network storage options, linked to delivery of streetscape
SuDS retrofits.
All new build developments to achieve Greenfield discharge rates, with a preference for this to beachieved using above ground, green SuDS measures.
Newly developed plots should be preferentially discharged to the Grand Union Canal or River Brent,
provided there is appropriate management of water quality and quantity for this to be achieved
without exacerbating flood risk or resulting in detriment to waterway health.
Further investigate extension of Mogden surface water catchment to handle additional flows.
Targeted retrofit of roof water recycling schemes, particularly for properties with outdoor use orprocess demands (not requiring re-plumping of internal pipework).
All new properties connected to adjacent non-potable network, if feasible, or installed with analternative means of water supply. Preferably, localised supplies should be delivered throughrainwater harvesting (if catchment and flow characteristics are appropriate), otherwise localised
greywater recycling should be utilised.
Rainwater harvesting should be investigated for newly proposed development, likely to beparticularly advantageous for industrial properties with large roof space and lower density of
employees. This may present particular opportunities for localised, pilot potable roof water recycling
systems.

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8

IWM Strategy Delivery

8.1.1.1

This section of the report considers how the various options identified within the described strategy
could be effectively procured, constructed and maintained, and which parties might be best placed todeliver these. In general, this should be arranged such that benefits are derived for the Old Oak andPark Royal Schemes in terms of:
Satisfying planning and regulatory requirements;
Optimising cost for the works;
Certainty of delivery of required works to meet the overall programme; andPlacing risk and associated responsibility with the party that is best placed to manage thiseffectively.

8.1.1.2

It is anticipated that the works will be carried out across a variety of scales, from plot, to sub-area(development scale) to area scale and that therefore the solutions for each of these will vary.

8.1.1.3

Additionally, there a variety of mechanisms whereby costs on a strategic scale for the entire
development could be cross-charged to individual plot developers. However, this will be highly
dependent on a large number of factors; particularly, the means by which infrastructure works of thisnature are recovered from the private sector.

8.1.1.4

It is considered that ongoing discussions with the key regional stakeholders and individual developers is
required in order to further confirm the most appropriate of these potential mechanisms and the detail. In
particular, these discussions should involve:
CIL and whether the works could be recovered through this in part;
S1068 / S2789 etc. and how costs could be allocated to the plot developers;
The charging mechanisms between Thames Water and the plot developers; andThe use or otherwise of an ESCO (Energy Services Companies) and/or MUSCO (Multi Utility
Services Companies) and how this would relate to costs paid by the plot developers.

8.1.1.5

The following sections summarise the key considerations which will need to be taken into account during
the delivery of the works, and how delivery of the key components of the strategy might be approached.

8.2

Key Delivery Considerations

8.2.1.1

There are a number of criteria that will need to be considered in the delivery of various aspects of thestrategy, recognising that this may be impacted on by the specific requirements of those organisations
that will both carry out the works and be responsible for the ongoing operation and maintenance. The
major factors that have been considered are described below.

8.2.2

Location

8.2.2.1

There are a number of proposed measures that involve works directly to or adjacent to proposedbuildings, and which are self-contained within the various development plots. As such, these works
would be carried out by the particular plot developers. There are, however, a number of solutions at bothsub-area and area scale, which involve works outside of the plot boundaries. Therefore, these measures
could conceivably be carried out by a number of parties..

8
9

Town and Country Planning Act (1990)
Highways Act (1980)

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8.2.3

Scale of the works

8.2.3.1

The proposed solutions cover some very significant works and, as such, are likely to yield benefits to thewider Old Oak Common and Park Royal area, rather than being specific to an individual plot ordevelopment parcel. In this circumstance, it is likely that these works would be carried out by Thames
Water or others, rather than by individual plot developers, as the need for them is strategic and could
also require the use of statutory powers in terms of land acquisition, which they are best placed todeliver.

8.2.4

Timing of the works

8.2.4.1

Following on from the above, it is clear that there will be some works for which timing will be critical toserve the development, especially in the early phases. Where this is the case, a balance will be required
between those works which are purely for the benefit of a single development, and therefore could be
the responsibility of that plot developer, and those works which are required for the wider development,
but again which need to be procured and delivered at an early stage. For the latter, this could represent
a significant opportunity for Thames Water / others to deliver these works and then for the individual plot
developers to connect to these systems.

8.2.5

Cash flow for the works

8.2.5.1

It is recognised that certain solutions will involve significant cost, and that these costs will have to be
incurred at an early stage in the overall development. In these circumstances, consideration will be
required as to which party is best placed to be responsible for these works. Given the level of cost, it isvery unlikely that one or more of the plot developers would be in a position to fund this, in part or as awhole, as the impact on their cash flow and hence the viability of their developments would besignificant. In these circumstances, it would be preferable if Thames Water or a third party procured andfunded these works, while recognising that there may be cross-charging mechanisms to the plot
developer(s).

8.2.6

Potential for integrated infrastructure delivery

8.2.6.1

The Old Oak Common and Park Royal Opportunity Areas will involve extensive infrastructure delivery,
to support the proposed development. As such, there are likely to be efficiencies which may be realised
through adopting a cohesive strategy for integrated delivery of new water infrastructure in conjunction
with other utilities, public realm or transport infrastructure.

8.2.7

Overall duration of the works

8.2.7.1

There is recognition that the delivery of the Old Oak Common and Park Royal Opportunity could takeplace over 30 years and therefore this needs to be considered when identifying an optimal delivery
strategy. Given these timescales, there is a need to maintain flexibility in the solutions that aredeveloped, so that they may be able to respond to new Regulations, advancements in technology andchanging market conditions over this period. As such, this long term approach and need to maintainflexibility could be more suited to Thames Water or other third parties, who are considered to be better
placed to assess how this could impact on their approach to providing long-term solutions in the context
of the wider network, rather than the plot Developers, who will be primarily concerned with solutions
which meet the needs of their developments at the time when these are being delivered.

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8.2.8

Appetite for taking on risk and responsibility for delivery of the works

8.2.8.1

This will have an impact on the delivery strategy; with a desire to place risk and responsibility with thoseparties who are best placed to manage this, but without this negatively impacting on the wider strategy
for the delivery of Old Oak Common and Park Royal. As such, it is considered that the plot developers
will be best placed to take on the risk and responsibility for those items which are critical to the deliveryof their schemes and for which they have the ability to control the outcome. However, where there is a
strategic solution which is for the benefit of the wider development and which requires a significant
degree of control over the final outcome, then it’s more likely that this will be best placed to be managed
by Thames Water / others.

8.2.9

Nature of companies that can deliver the works

8.2.9.1

This will be a key aspect of the delivery strategy; recognising that the market is developing in terms ofcompanies that have the ability to carry out strategic works of this nature, and that there are changing
Regulations affecting the delivery of such works in the water market. The impact of this is that there will
be significant interest from the market in respect of delivery and long-term management of assets for a
project of this scale and importance, driven by the substantial revenue streams that will be available
from a variety of end occupiers. There are a number of examples of major schemes that are being
delivered currently through ESCO’s and MUSCO’s including Kings Cross in London. The potential for ascheme of this scale to attract interest from the market, allied with the changes in Regulations of theWater Market is anticipated to be substantial.

8.3

Potential delivery approaches

8.3.1.1

Taking in to account all of the above factors, consideration has been given to the proposed solutions
and how their delivery could be approached. This has been broadly divided between the surface water
management aspects of the strategy and the water recycling solutions, including wastewater, storm
water and grey water, while recognising that some solutions will applicable across more than one ofthese options.

8.3.2

Surface water management

8.3.2.1

A number of measures are recommended for installation within individual development plots, including
the installation of green roofs, permeable surfacing, bio-retention systems and below ground attenuation
measures. Being within the development boundaries, these are recommended as being best placed tobe carried out by the plot developers, in line with regional planning policy and guidance given by the
Lead Local Authorities.

8.3.2.2

However, the broader-scale solutions, including the delivery of streetscape surface water networks anddownstream stormwater detention features are likely to have more distributed benefit, and could bedelivered through a range of parties.

8.3.3

Strategic surface water network and attenuation

8.3.3.1

It is considered that this infrastructure may be best placed to be carried out by the party responsible forthe delivery of the primary and secondary highways networks across the wider development, with thedrainage network forming an integral part of the overall streetscape. As such, delivery could be theresponsibility of one or more plot developer(s), where they are carrying out such works under a S278
Agreement (which could be particularly relevant where these works are required to be delivered at an
early stage to serve a particular development rather than the scheme as a whole), the Highways
Authority or another third party who are carrying out these works.

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8.3.3.2

However, with respect to future maintenance requirements, it is likely that this would be best placed towith the Highways Authority, who are generally responsible for adopting and maintaining all SuDS within
the adopted public highway, even where these have been carried out by individual developer(s). The
operation of installed SuDS systems will also impact upon downstream systems, including the Thames
Water sewer network, stormwater harvesting systems or waterway discharge points. Therefore, suchparties may also require varying levels of consultation or responsibility with regards to ongoing
maintenance.

8.3.3.3

Considering downstream attenuation storages, is considered that these works would be best placed to
be delivered by third parties and not by plot developers, as the works will be of a significant scale andwill involve substantial land take which will not be feasible for plot developers to deliver.

8.3.3.4

However, where developers are utilising dispersed, downstream options of network attenuation toachieve Greenfield runoff rates (as opposed to on-plot solutions), it may also be reasonable forcontribution to be made to the capital and operational costs of delivery.

8.3.4

Strategic Water Recycling Options

8.3.4.1

Of the recycling options considered, localised greywater or rainwater harvesting solutions are deemed tobe best suited to be delivered directly by the plot developers, as a part of the development construction
and delivery. Engagement of specialist third party manufacturers and operators is expected to berequired, and consultation with the wider area stakeholders would be recommended in the design of any
such scheme.

8.3.4.2

Area-scale solutions for strategic water recycling networks are likely be unfeasible for delivery and/or
operation by plot developers. Potential developers and/or operators could include Thames Water, third
party operators or a combination.

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9Conclusions and Recommendations

9.1.1.1

The proposed regeneration of the Opportunity Areas presents an opportunity to deliver a new paradigmof water management. Old Oak Common, in particular, presents the chance to deliver a new system,
harnessing the latest technological advancements to deliver an aspirational water sensitive
development, sustained by a flexible and resilient portfolio of water infrastructure. Across existing areasof Park Royal, the transition will be more gradual, focused on targeted retrofit and harnessing
opportunities where available. It is also intended that the water management strategy for these areas issynergistic with the wider sustainability and community aspirations of the redevelopment, delivering avibrant, liveable centre.

9.2

The Preferred Strategy

9.2.1.1

A MCA process using key performance indicators has been undertaken for potential combinations ofwater management measures to derive a number of water management strategy options that meet thethree core water management objectives of:Providing attenuation and sustainable drainage features to achieve Greenfield runoff rates:
Minimising demand on the centralised potable water supply as far as possible; andAchieving a neutral discharge position.

9.2.1.2

Six potential strategy options were developed; all of which meet the core water objectives and therefore
would allow development to proceed. Whilst the detail of how these strategy options would be delivered
would need to be worked up in the next stages of the study, the delivery of any one of these options
would ensure that combined discharges to the sewer system would not be increased (and significantly
decreased in more extreme rainfall events); and, demand would be minimised and Mayoral targets forwater demand met (and exceeded in most locations).

9.2.1.3

Of the options proposed, a preferred water management strategy option was selected based on thescoring against the performance criteria and the flexibility of deliverability which it would provide. Thispreferred strategy includes:
Maximising levels of water efficiency and demand management, through innovation and the deliveryof new technologies, smart networks and community engagement.
A cohesive, integrated approach to managing surface water quality and quantity across thedevelopment, focusing on the provision of green sustainable drainage infrastructure, delivered tomaximise benefit for amenity and biodiversity. This includes a hierarchical approach to providing
attenuation via source control on plot, strategic SuDS networks for the public realm, and theprovision of the remaining attenuation through dispersed or centralised attenuation with water
quality management to achieve Greenfield discharges for storm events up to the 1 in 100 (with anallowance for climate change).
To reduce discharge volumes to the combined sewer, develop options to discharge as muchattenuated surface water possible through alternative discharge such as controlled discharge to theGrand Union Canal.
Delivery of a strategic wastewater recycling solution with a single treatment location, providing nonpotable water to reduce overall demand from centralised supplies. It is recommended that a
strategic network-based solution is developed to provide the recycled water for non-potable use. At
this stage, recycled wastewater has been indicated as the most preferential option; however,reclaimed stormwater and greywater are also potentially advantageous alternative orcomplementary solutions.
To move closer to a position of water neutrality, direct potable water recycling is also recommended
for further investigation. This may include use of harvested rainwater to directly augment potablesupplies, and maintaining design flexibility to allow for non-potable recycling infrastructure to bescaled up to potable recycling; when the technical and social environments are appropriate.

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9.2.1.4

Whilst a preferred strategy has been proposed it is intended that the water management approachremains flexible and able to be adapted in line with the development proposals, technologicaladvancement and the selected delivery strategy. This approach has fed into the development of the
Local Plan with the six potential strategy options highlighted within the draft Plan alongsiderecommended water and flood risk policies to ensure the aims and direction of the strategy areembedded in the plan making process and the planning decision process.

9.3

Next Steps for Strategy Development

9.3.1.1

Following consultation on this Strategy as part of the wider Local Plan consultation for the Opportunity
Area, further refinements will be made to the preferred water management strategy. These refinements
will be a core part of the detailed further assessment of the feasibility and outline design of the preferredstrategy and a detailed plan for how the strategy will be delivered. This further work will take place in2016, alongside the developing utilities strategy and environmental standard setting for the Opportunity
Area.

9.3.2

Recommendations for Further Assessment

9.3.2.1

The following actions are recommended for the next stage of the strategy development in order toprogress with further refining, scoping and delivering this integrated water management strategy:
Greater investigation of the hydrological character of the Grand Union Canal and River Brent andfurther engagement with key stakeholders in order to confirm the suitability of natural catchmentdischarge to these locations.
Spatial planning to target beneficial locations for surface water attenuation and conveyancenetworks. Particularly, it is recommended that preliminary design of a streetscape surface water
network be undertaken and any required refinements to the masterplan targeted in order to harness
the natural area hydrology. Similarly, in order to achieve Greenfield run-off there will be a need toconsider off-site attenuation in surrounding open spaces, such as Wormwood Scrubs. The draft
Local Plan for the development is understood to seek stakeholders’ views regarding preferential
attenuation locations.
Ongoing engagement with key stakeholders across the Opportunity Areas to confirm the preferredmechanism for delivery of the IWM strategy, including capital investment and ongoing operation andmaintenance. This will be central to confirming the preferred water recycling and storage strategy.
Further detailed scoping of each of the recycling options is required. In particular, spatialconfigurations should be confirmed as early as possible, so that potential constraints are managed
through the master-planning process, and infrastructure delivery streamlined to maximise cost
efficiency and feasibility.
Consideration of opportunities to align infrastructure delivery with other significant utilities provision
within the Opportunity Area.
Initial discussions with potential third party service operators and manufacturers should beundertaken to further scope the potential for delivery of innovative technologies and involvement of
new service operators.

9.3.2.2

To support the wider water management options, the Strategic Flood Risk Assessment has highlighted
high risk areas where one or more sources of flooding represent a risk to development. To mitigate risk
within these areas, recommendations are made on how to manage development in some locations, andopportunities to combine flood risk management options with the preferred water management
measures have been highlighted to provide strategic water management. These recommendations are
set out below:
In managing residual risk from canal breach flooding, it is recommended that development in Old
Oak Common is set back from the canal. This is in keeping with the current masterplan proposals tocreate a green corridor along the canal;

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Development in the north west of Park Royal should be set back from the River Brent edges toenable a range of additional flood risk management options for the wider Brent corridor;
Re-configuration of areas of green space proposed within the early Old Oak Common masterplan
should be considered to be located in areas of existing surface water ponding to act as areas ofdispersed attenuation storage.
LBHF has previously considered the feasibility of providing storm water attenuation within
Wormwood Scrubs to reduce the risk of flooding to property and infrastructure to the south of the
Scrubs within the Borough. This could be combined with storm water attenuation from theOpportunity Area to provide benefit both to the Opportunity Area and the wider drainage catchment
to the south.
A drainage study is being carried out by Thames Water in order to establish the flow characteristics
and capacity in the river and drainage system for the River Brent. The study is being carried out onbehalf of North Brent and Harrow Flood Stakeholders Group. This could identify opportunities toprovide discharge for attenuated surface water from Park Royal that fall into the topographicalcatchment of the Brent, thereby reducing discharge to the Counters Creek catchment,.
Thorough retrofit of the Park Royal section of the site, there are opportunities for Blue Corridors (viaraised kerbs) particularly around the high risk areas and associated roads identified to the south ofthe canal within the current industrial areas.

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APPENDIX A
West London Opportunity Area Water
Demand Analysis

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Old Oak Common and Park RoyalAPPENDIX A: Demand and Wastewater Calculations

This Appendix sets out a summary of the calculations for water demand and wastewater generation from the
combined proposed development for Opportunity Areas and major planning applications sharing the samedrainage infrastructure as the Old Oak Common and Park Royal study area.
In order to better understand the likely water demand and wastewater increases as a result of development
occurring, each Opportunity Area has been considered in detail, looking at development proposals as well as(where available) planning applications for specific developments.
In so doing, the likely distribution of development within the Opportunity Areas was established in relation to thedrainage infrastructure, confirming the uses occurring within the drainage catchment. This is summarised in Table
A1.
Table A1: Proposed development within each Opportunity Area

OA NameNew
Homes
Minimum

White City-

Population

Employment Capacity

6,000

12,60010,000Kensal Canalside

3,500

7,350

2,000

Wembley

0

0

1,600

Earls Court and West Kensington

7,500

15,7509,500

Total other OAs

17,00035,70023,100

Old Oak & Park Royal

24,00046,20055,000Total – all OAs

41,00081,90078,100

Old Oak and Park Royal (%)

58.5%

56.4%

70.4%

Based on the expected development, daily residential and employment demands and wastewater volumes havebeen estimated, indicating the additional pressure this development will place on the Counters Creek catchment. A
series of assumptions have been made to calculate per day water demands and waste water for eachdevelopment, these have been outlined in Table A2.
Table A2: Assumptions used to calculate per day water demands and wastewater generation

1

Type

Litres per person per day

Residential Potable

110.65

Water Demands

Residential Non-Potable
Employment Potable
Employment Non-Potable
Residential Grey

20.60
19.53
18.00
75.11

Sewer Discharges

Residential Black
Employment Grey
Employment Black

56.14
7.34
30.19

The day values have then been scaled up to give an annual overview of annual demand and wastewater
generated within the Opportunity Areas, basing figures for residential development on 365 days and employment
development on 253 days, allowing for the nature of use of employment uses. The results are shown in Table A3.

1

These values have been estimated using the usage estimates and maximum fittings consumption, as per the Building Regulations(Approved Document G) and British Standard BS8542

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Table A3: Daily residential and employment demand within each Counters Creek Opportunity Area

OA NameAnnualresidential
demand (Ml/d)Annual employment
demand (Ml/d)Annualresidential
waste (m3/d)

Annual employment
waste (m3/d)

White City

1.65

0.38

1,654

375

Kensal Canalside

0.96

0.08

965

60

Wembley

-

0.06

0

0

Earls Court and West
Kensington

2.07

0.36

2,067

0

Total - other OAs

4.68

0.88

4,686

435

Old Oak and Park
Royal

6.06

2.06

6,063

2,064

Total – all OAs

10.74

2.94

10,7492,499

Old Oak and Park
Royal (%)

56.4%

70.1%

56.4%

82.6%

When combined with the additional demands and wastewater discharge from Old Oak and Park Royal, thedemands and discharges generated from growth within the other Opportunity Areas linked to the same drainage
system represents a significant increase in pressure on the already constrained infrastructure.

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APPENDIX B
Asset Database

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APPENDIX C
Opportunity Area Strategic Flood Risk
Assessment

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Old Oak Common and Park RoyalAPPENDIX C: Strategic Level Flood Risk Assessment

Introduction
This Appendix sets out the Strategic-Level Flood Risk Assessment for the Old Oak Common and Park Royal
Integrated Water Management Strategy (the ‘Strategy’).

Aims
The aim of the strategic-level flood risk assessment is to:
Identify the main sources of flood risk to the development using best available historical and flood risk
datasets and studies made available by London Boroughs, the Environment Agency, Thames Water andother strategic stakeholders.
Assess all sources of flooding (including fluvial, tidal, surface water, groundwater, sewer and artificial
sources) to the ODPC area and consider the flood risk implications within the wider Counters Creek
catchment.
Review the Environment Agency’s 6-year Flood Risk Management Investment Programme and otherstudies undertaken in the OPDC area to identify those schemes that may have an impact on theOpportunity Areas and the wider Counters Creek catchment, and vice versa.
The outcomes from the assessments are reported alongside recommendations for developments in the area, andsupported by mapped outputs of the different sources of flood risk to the OPDC area and wider catchment.

Existing Evidence Base
The flood risk evidence base for the Opportunity Area is extensive. The documents outlined in Table C1 havebeen reviewed as part of this assessment alongside historical records and further information provided by various.
stakeholders.
Table C1: Existing Evidence Base for Old Oak Common & Park Royal Opportunity Area

Evidence

Link

Strategic Flood
Risk Assessment

LB Ealing (2008)
http://www.ealing.gov.uk/downloads/download/564/ldf_evidence_base_strategic_flood_risk_asse
ssment
LB Brent (Level 1 – 2007, Level 2 – 2010 (Sequential Test))
https://www.brent.gov.uk/services-for-residents/planning-and-building-control/planningpolicy/flooding-and-flood-risk/
LB Hammersmith and Fulham
http://www.lbhf.gov.uk/Images/LBHFSFRA_Final_tcm21-148443.pdf

Local Flood Risk
Management
Strategy

LB Ealing (draft, December 2014)
http://www.ealing.gov.uk/download/downloads/id/9272/local_flood_risk_management_strategy_draft
LB Brent (draft, July 2015)
http://brent-consult.objective.co.uk/portal/ens/htdel/flood_risk_strategy_3?tab=files

Preliminary
Flood Risk
Assessment

LB Ealing (2011)
LB Brent (2011)
LB Hammersmith and Fulham (2011)
http://webarchive.nationalarchives.gov.uk/20140328084622/http:/www.environmentagency.gov.uk/research/planning/135542.aspx#9

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Evidence

Link

Surface Water
Management
Plan

LB Ealing
London Borough of Ealing –Surface Water Management Plan (2011)
LB Brent
www.brent.gov.uk/media/documentlibrary/servicesforresidents/planningbuildingcontrol/planning/planningpolicy/ldfrelated/ldfsupportingdocuments/wembleyareaactionplan/climatechange/350116
0/W8.3%20Brent%20Surface%20Water%20Management%20Plan.pdf
www.brent.gov.uk/media/documentlibrary/servicesforresidents/planningbuildingcontrol/planning/planningpolicy/flooding/9515010/Surface%20Water%20Management%20Plan%20Appendices.p
df
LB Hammersmith and Fulham
London Borough of Hammersmith and Fulham – Updated Surface Water Management Plan
(July 2015)

Regional Flood
Risk Appraisal
for Greater
LondonLondon Regional Flood Risk Appraisal - First Review (August 2014)

Thames River
Basin District
Flood Risk
Management
Plan
Individual Flood
Risk Studies
Environment
AgencyDraft (October 2014): https://consult.environmentagency.gov.uk/portal/ho/flood/draft_frmp/consult

http://www.london.gov.uk/sites/default/files/Regional%20Flood%20Risk%20Assessment%20%20First%20Review%20-%20August%202014.pdf

Wormwood Scrubs Surface Water Management Scheme – Feasibility Study (July 2012)
Flood Risk Mapping (provided for the study and available here: http://watermaps.environmentagency.gov.uk/wiyby/wiyby.aspx?topic=floodmap#x=357683&y=355134&scale=2 )Risk of flooding from Surface Water
Risk of flooding from Rivers and Sea
Risk of Flooding from Reservoirs
Flood map for Planning (Rivers and Sea)

Thames Water

Counters Creek: http://www.thameswater.co.uk/counterscreek/17222.htm

Flood Risk
Assessments for
Major
Developments

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Sources of Flood Risk
Flood Risk Summary to Old Oak Common & Park Royal
Table C2 presents a summary of the flood risk from all sources to the study area, based on the datasets outlinedin Table C1 as well as historical flood risk incident data received from various Risk Management Authorities.
Historical flood records are shown in Figure C1 below.

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Old Oak Common and Park RoyalAPPENDIX C: Strategic Level Flood Risk Assessment

Table C2 Summary of flood risk for all sources of flooding

Flood Source
FluvialFlooding Pathways & Historical
Flooding
The Brent is reported to flood regularly
along its floodplain during periods ofhigh rainfall or when the Welsh Harp
Reservoir opens its flood gates torelieve pressure on the reservoir. Ealing
Council Records indicate that areas
previously affected by flooding from theBrent include:
Ealing Golf Course
Perivale Bridge Playing Fields
Perivale Park Golf Course

Summary of Risk
The majority of the Opportunity Area (and allof the Old Oak Common area) is in Flood
Zone 1.
The northwest of Opportunity Area within Park
Royal is in Flood Zones 2 and 3 of the River
Brent, and lies within the natural floodplain.
No built development is proposed within thesehigher risk flood zones as part of theregeneration proposals for Park Royal.
Overall, fluvial flood risk to the Opportunity
Area is low.

Brent Valley Golf Course
Flooding is reported to have occurred in
1977, 1927, 1928 (Ealing SFRA)The River Brent is reported to haveflooded close to the crossing of theA4005 Hanger Lane within Perivale
Park Golf Course.1
The LB Brent SFRA listed several major
flood events on the River Brent (1928,
1977, 1988, 1990 and 2000) and on the
Wealdstone Brook (15 flood events
between 1928 and 1981), thoughspecific locations are not provided. The
LB Ealing SFRA reports flooding tohave occurred in 1977, 1927, 1928.
Tidal

No Source of flooding

No risk

Surface Water

Victoria Road within the study area hasreported surface water flooding inAugust 2004 and minor flooding in May
2006. (Ealing SFRA)The Ealing SFRA reports that drainage
flooding within the study area can be attributed
to either a lack of capacity or due toinfrastructure failure.

Brent is very fortunate not to haveexperienced major flooding incidents inlast 20 years. The most recent floods
were in 2007 and 2010 and much of thisoccurred on the highway, open spaces
and gardens.

Flooding is likely to be severe and of longer
duration in low lying areas but local problems
may result in all areas as a result of very
heavy rain or infrastructure failure (Ealing
SFRA).

The LB Brent PFRA reports that a
number of properties flooded during theJuly 2007 event, although the exact
location of the flooded properties was
not provided. The main cause offlooding was a combination of surface
water runoff and inadequate sewer
capacity. Anecdotal information has
shown that the A4000 Victoria Road
Bridge, close to the junction with
Chandos Road, flooded in August 2004.

Generally, surface water flood risk is low
across the majority of the study area, being
largely constrained to roads, railways andareas adjacent to railway embankments.
Areas of higher risk including surface water
have been identified and are reported insubsequent subsections of this assessment.

Critical Drainage Areas (CDAs) arelocated within the study area and1

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Old Oak Common and Park Royal

Flood Source

Groundwater

Flooding Pathways & Historical
Flooding
detailed within this FRA,The LB Ealing PFRA identifies a
number of groundwater flooding
incidents within the wider Borough, with
the nearest to the study area occurringto the south-east of Hanger Lane
Station (south west corner of Park
Royal).
Groundwater flooding has not been asignificant issue for the study area andthe only historical record identified was
during 2000/01 (Ealing SFRA).
The PFRA reports do not show any
areas to have an increased potential forelevated groundwater.

APPENDIX C: Strategic Level Flood Risk Assessment

Summary of Risk

The majority of the Opportunity Area isunderlain by the impermeable London Claylayer. The geological succession beneath theLondon Clay comprises: 2
the Harwich Formation;
the Lambeth Group;
the Thanet Sand Formation; andthe Cretaceous Chalk Group.
Along the River Brent valley (and hence thewestern boundary of the Park Royal site) there
are potentially water-bearing superficial
deposits comprising alluvium and river terrace
deposits (Taplow Gravel and Kempton Park
Gravel) associated with the river andfloodplain corridor. Shallow groundwater islikely to be in continuity with surface water inthe River Brent. A further narrow ribbon of
alluvial deposits is also present in the westernpart of the study area, along Greenford Road,
which is associated with a now culverted
stream.
The eastern boundary of the study area andthe Brent floodplain appears to be at a higher
risk of potential groundwater flooding due tothe presence of superficial deposits. (Ealing
SFRA). Overall the groundwater flood risk is
considered to be low.
It is recommended that for development inareas identified as ‘high risk’, further analysis
should be carried out to determine thepresence of groundwater onsite. (Ealing
SFRA)

Sewer

The PFRAs and SFRAs within the study
area have reported a number ofhistorical incidents of sewer flooding,however, the exact location of these
events is not available in every case.
Several Thames Water sewer flooding
records have been recorded in the
study area, mostly within Park Royal.
Several flooding incidents have beenrecorded either side of Acton Lane to
the north-east of Central Middlesex
Hospital. Within Old Oak, threeincidents were recorded just south ofNorth Action tube station.
More widely, the LB Ealing SFRA notes
the susceptibility and historicaloccurrence of flooding from overloaded

Sewer flood risk is considered to be highSouth of North Acton Railway line (Ealing
SFRA).
TWUL historical DG5 sewer flooding records
presented in the PFRA reports show that there
have been a number of sewer flooding
incidents within the study area. Records areavailable within the respective PFRA reports
to a resolution of four-figure postcode sector
references. To the south-west of the proposed
HS2 station at Old Oak Common and the
proposed Victoria Road crossover box there
are two further adjacent postcode areas whereagain sewer flooding incidents have occurredand have been recorded in the 21- 50 range
and 51-100 range respectively. 3
Sewer flood risk is considered to be moderate

2

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Old Oak Common and Park Royal

Flood Source

Flooding Pathways & Historical
Flooding
sewers within the borough, particularly
within Northolt and Greenford, withrecorded flood events in Acton during
the 2007 flood event. The SFRA
identifies a total of 140 properties haveflooded in Ealing from the foul waterdrainage systems and 30 properties
have flooded as a result of surcharging
of surface water sewers in the past 10
years, with a further 135 properties
affected by flooding from combined
systems in the same time period. The
majority of these incidents are in Acton,
south of the Study Area.

APPENDIX C: Strategic Level Flood Risk Assessment

Summary of Risk
across within Park Royal and the south east
section of Old Oak.

Property flooding from combined
sewers occurs within the wider counters
creek catchment (to which Old Oak andparts of Park Royal drain) due to lack of
capacity within the wider drainage
network. Surface water and foul waterflow increases from the proposeddevelopment could exacerbate this risk
if not mitigated.
Artificial –Grand Union
Canal

The Grand Union Canal (GUC) has
overtopped historically further west in
Ealing (1977, 1992 and 2000); however,there are no historical recorded
incidents of flooding from the canalwithin the study area.
The RBKC and LBHF SFRA states that
the Grand Union Canal (Paddington
Branch) in the north of the two boroughs
is likely to act as a conveyor of surface
water in an extreme event and it is likely
to convey flow out of the boroughs dueto the topography.
The Canal & River Trust (formerly
British Waterways) is responsible for the
maintenance of the canal network andhas confirmed that there are 43km ofunrestrained water (i.e. no locks) on thisreach of the Grand Union Canal(Paddington Branch). 4
Within the site, the Grand Union Canal(Paddington Branch), close to Old Oak
Common, is retained on the southernside and managed water levels areapproximately 1.75m above surrounding
ground levels, rising to 4.5m. The
towing path is 2.5m wide. Further to thewest the towing path is on the south
side of the canal at a level ofapproximately 30m AOD. Ground levelsin the existing GWML railway to the

The Grand Union Canal is a significant water
course running through the study area andposes a residual flood risk. Since there is astrict maintenance programme in place
managed by British Waterways, any potential
breach is likely to be picked up before any
serious flooding occurs. As such a breach ofGrand Union Canal is considered a residual
risk. (Ealing SFRA)
Condition survey reports were reviewed for theGrand Union Canal as part of the HS2
Environmental Statement and breachmodelling was undertaken. The canal currently
poses a flood risk to the site of the proposed
HS2 station and surrounding area. Twodimensional hydraulic modelling has been
undertaken to determine the extent and depthof flooding associated with a breach of theretaining wall of the canal. For the baseline
case (no HS2 works), breach flood waters willflow to the south before entering the track
beds of the GWML. Flood waters will travel tothe east and to the west along the GWML.
Flood waters will also flow overland acrossWormwood Scrubs Common.5
Depths of flooding are expected to be in theorder of approximately 0.2m–1m dependingon the location of the assessment point, andthe expected width of breach.
Due to the management and maintenance ofthe canal and the limited extent of breach

4

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Old Oak Common and Park Royal

Flood Source

Artificial –Welsh Harp
Reservoir

Flooding Pathways & Historical
Flooding
south are approximately 25m AOD andthe managed water level in the canal istherefore approximately 4.5m above
ground levels on the site. The land
continues to fall away to the south
through Wormwood Scrubs Common
towards mixed land use including theresidential area at Wulfstan Street,
Wormwood Scrubs Prison, Queen
Charlotte's & Chelsea Hospital,
Hammersmith Hospital, Burlington
Danes School and the Linford Christie
Athletics Stadium.
A dam break was experienced in the
1940’s causing significant flooding apartform that incidence, due to a strict
maintenance regime, only minor
seepages and leakages have beenreported. (Ealing SFRA)APPENDIX C: Strategic Level Flood Risk Assessment

Summary of Risk
water, it is therefore concluded that there will
be a low residual risk of flooding from theGrand Union Canal (Paddington Branch) tothe area, due to the failure of the canalretaining structures. 6

The river valley of the River Brent, to thenorthwest of the site, lies within the maximum
extent of flooding from the Welsh Harp
Reservoir. However, proposed development is
not located within this flood extent and hence
the risk from breach or dam break of the
Welsh Harp Reservoir is concluded to be low.

Figure C1: Historical flood records in the study area:

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Old Oak Common and Park RoyalAPPENDIX C: Strategic Level Flood Risk Assessment

Critical Drainage Areas (CDAs)
The SWMPs undertaken for the London Boroughs of Brent, Ealing and Hammersmith & Fulham identified anumber of CDAs covering the Opportunity Area as identified in Figure C2 and described in Table C3.
Table C3: Surface Water Critical Drainage Areas

Borough

CDA

Location

Description

EalingGroup1_009

Flooding of Network
Rail tracks between
Ealing Broadway
station to Acton
mainline station, andthe LUL arms of thissection up to Park
Royal via North
Ealing, and up to A40
via West Acton

The Drain London modelling outputs indicated that ponding
may occur within the railway cutting as it is a topographicallow point within the catchment. The platforms at Acton NR
station, West Acton LU station, North Ealing LU station andPark Royal LU station are all at risk of surface water flooding.

A40/A406 underpass,near Hanger Lane,
Ealing

Surface water is predicted to pond in the low point in road.

Park Royal

Located in a predominantly commercial area, the main
source of flood risk within this CDA is from ponding surface
water in topographic depressions. One Local Flood Risk
Zone (LFRZ) has been designated in the area at mostGroup1_011

Brent

Group2_043
Brent_10

Group2_042

North Circular

Brent_09

Hammers
mith &
FulhamWard Area
1

College Park and Old
Oak

The hazard on the railway tracks is predicted to be moderate/significant, with some areas identified as an extreme hazard
due to the depth of water.

The hazard within the road is predicted to vary between
significant and extreme.

significant risk of surface water ponding, in the vicinity ofCentral Middlesex Hospital, Central Way and CoronationRoad.
A predominantly commercial CDA with a small residential
area to the north west. The main source of surface water
flood risk within this CDA is ponding flow in topographic low
spots. One higher risk area (Local Flood Risk Zone) has
been designated within this CDA which corresponds with thesignificant area of ponding on the A406 North Circular, aregionally important infrastructure asset
This Ward was identified as being at risk from surface waterand sewer flooding. The modelling shows that surface waterflows from the sloped areas of Wormwood Scrubs Park and
Old Oak Common towards the railway embankment to thesouth. The presence of buildings and the railway line causes
surface water to pond in the low lying areas behind theembankment. There is the potential for surcharging of thesewer network at points along Wulfstan Street that would
increase surface water flooding along the railway line.
The main hazards within the Ward are associated within theareas of deep flooding and where there are high velocities,
i.e. the main flow paths along the railway line. There are 39
flooding hotspots within the Ward.
There were no Council records of surface water flooding in
the Ward during the July 2007 flood event. There are 15
records of flooding recorded on the A40 from TfL records.

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Old Oak Common and Park RoyalAPPENDIX C: Strategic Level Flood Risk Assessment

Figure C2: Location of Critical Drainage Areas (in green)High Risk Areas
The baseline and historical flooding incident information from all flood risk sources has been used to identify High
Risk Areas within the study area; these areas are shown in Figure C3.
These High Risk Areas are locations where one of more flood risk sources result in a higher localised flood risk
than the majority of the study area which is concluded to be at low flood risk overall. They have been identified
based on land which is located within, or subject to one or more of the following:
Fluvial Flood Zones 2 or 3;
Close proximity to water bodies (rivers, canals, ponds or water features) with either historical flood records andor susceptibility to surface water flooding;Significant area of land with a modelled surface water flood risk of ‘High’ (1 in 30 year), or ‘Medium’ (1 in 100year);
More than one historical record of flooding from any source.
These locations, and specific mitigation, should be considered carefully when considering individual planningapplications in these locations. With respect to intensification of Park Royal land uses, proposals for additional
development should preferentially be steered away from these higher risk areas. For Old Oak, consideration
should be given at masterplanning stage to plot layout and provision of green space, allowing space for flood
waters specifically associated with surface water.

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Old Oak Common and Park RoyalAPPENDIX C: Strategic Level Flood Risk Assessment

Figure C3: High Risk Areas within the study area (black outline)

Impacts of Other Major Development in Area
HS2 development
There is the potential for the proposed HS2 scheme to change the baseline risk of flooding described in thisappendix. Though designed such that the probability of the Proposed Scheme flooding in any given year is lessthan 1 in 1,000, any change to the baseline risk of flooding could impact on the assessment of flood risk within theOpportunity Area.
A review of the HS2 flood risk assessments within the Environmental Statement suggests that only baseline
surface water flood risk would be altered by the HS2 scheme.
The above ground infrastructure has the potential to alter overland flow routes for surface water, thereby changing
the risk of flooding to local receptors. Surface water runoff from all permanent structures will be controlled atsource by design and will prevent increased rates and volumes of surface water runoff overland flow to the local
sewer network or above ground receptors.
Old Oak Common Station

Significant land levelling works are proposed at Old Oak Common station. These works will therefore change thenatural overland flowpaths and the location of predicted surface water flooding. However, there are no distinct
flowpaths crossing the Old Oak Common station site, and the surface water flood risk at the shafts and stationbuilding is therefore unlikely to increase.
Surface water will be collected in the station drainage network and attenuated up to the 1 in 100 years return
period (1% annual probability) rainfall event including an allowance for climate change. Attenuation volumes up toa maximum of 7,100m3 are proposed in the vicinity of the station. The design states that the provision of SuDS
should be considered, such as green roofs/porous paving. Attenuated surface water will be discharged to the local
Thames Water sewer network. Any connection will be agreed in advance with Thames Water.
The Proposed Scheme will therefore not lead to a change in the risk of flooding from surface water sources at Old
Oak Common station. There will therefore be no adverse effects on the risk of flooding from surface water at Old

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Old Oak Common and Park RoyalAPPENDIX C: Strategic Level Flood Risk Assessment

Oak Common Network Rail depot, Wormwood Scrubs Common or East Acton urban centre arising from the
Proposed Scheme.
A4000 Victoria Road Bridge

The widening of the A4000 Victoria Road is proposed to accommodate traffic requirements for Old Oak Common
as development proposals expect an increase in traffic movement. The design states that one half of thecarriageway will continue to drain to the existing sewer network and the widened part of the road will be restricted
to like-for-like runoff rates based on 50mm/hr. Oversized pipes in the order of 1050mm in diameter will be requiredin order to achieve the attenuation required.
The Proposed Scheme will not lead to any increase in the risk of flooding from surface water sources at the A4000
Victoria Road Bridge.

Flood Risk Management
The linkage of existing proposed flood risk management measures with existing or planned flood risk management
schemes offer the potential to work with other parties to deliver wider flood risk management benefits that benefit
the Old oak Common & Park Royal Opportunity Areas and their regeneration.

Planned Flood Management Schemes
Environment Agency schemes
The Environment Agency is managing a six-year flood risk management investment programme7. Whilst none ofthe projects within the six year plan lie in the Old Oak Common & Park Royal Opportunity Area, some of the
projects could benefit the regeneration of Park Royal and Old Oak and could combine with wider water
management solutions proposed through the Strategy.
To the east – Camden West Surface Water FAS.
To the north – Wealdstone Brook FAS.

Potential Flood Management Schemes
Surface Water Management Schemes

A number of surface water management mitigation schemes were identified for CDAs in the the London Boroughsof Ealing, Brent and Hammersmith & Fulham. These were assessed as part of the SWMP and a preferred option
identified for each CDA, with associated costs and potential benefits. Details are provided in Table C4
Table C4: Surface Water Mitigation Schemes within Critical Drainage Areas

Borough

CDA

Location

Preferred Option

EalingGroup1_009

Flooding of
Network Rail
tracks between
Ealing Broadway
station to Acton
mainline station,and the LULarms of thissection up to
Park Royal via
North Ealing, andup to A40 via

The preferred option for CDA_009 is to reduce ground levels within
the identified open space areas near the CDA (within overland flow
path areas), to provide storage for depths up to 30cm, footpath andkerb modifications are also recommended for nearby roads topromote flow into these areas of open space. This option isestimated to cost in between £501k – £1m.
A flood plan should also be put in place, linked to extreme rainfall
alerts that would enable alternative transportation options to be put
in place, minimising disruption to network rail users. A plan should
already be in use for the stations predicted to be affected by thesurface water flooding.

7

Environment Agency six-year flood risk management investment programme:
https://www.gov.uk/government/publications/programme-of-flood-and-coastal-erosion-risk-management-schemes

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Old Oak Common and Park Royal

Borough

CDA

Group1_011

APPENDIX C: Strategic Level Flood Risk Assessment

Location

Preferred Option

West Acton

Other measures that were considered include the ”do nothing
scenario or provide flood storage within the railway corridor.

A40/A406
underpass, near
Hanger Lane,
Ealing

The preferred option for this CDA was to provide undergroundstorage beneath the A40 and improve entry capacity. It was also
recommended that a flood plan is implemented (or revised if inexistence) as this area is considered critical transport infrastructureof local significance. This preferred option will reduce the depth offlooding in the area and is estimated to cost between £251k and£500k.
Other measures that were considered include the ”do nothing
scenario and increasing the drainage capacity beneath the A40.
Increasing the drainage capacity beneath the A40 depends on
existing services beneath the road and the impact on thedownstream capacity. This measure has the potential to increase
flood risk downstream if the drainage system’s capacity is limited –but could be reviewed during a detailed feasibility study.

BrentGroup2_043

Park Royal

Brent_10

To mitigate the flood risk in this area, the preferred option was toinstall a series of roadside rain gardens along Cumberland Avenue,
Willenfield Road, Abbey Road and Central Way will help to intercept
and reduce surface water runoff in this CDA. The proposed
measures estimated cost: Roadside Rain Garden < £25k
The proposed measures will help to reduce surface water runoff
through the commercial areas. This option will not completely
eliminate the risk posed to property but it should mitigate the risks
and help reduce the deeper areas of ponding.

Group2_042

North Circular

Brent_09

To mitigate the flood risk in this area, the preferred option was toinstall six additional gully points in the A406 underpass to improvedrainage through the underpass. The proposed measures estimated
was: Additional Gully Point which had an estimated cost of under£25k.
The proposed measures will help to reduce localised surface water
ponding on the A406 North Circular. This option will not completely
eliminate the risk posed to property but it should mitigate the risks
and help reduce the deeper areas of ponding. A full assessment of
the current drainage and pumping capacity of the system throughthe underpass by TfL would be beneficial as this is such a key
transport route within the Borough.

Hammers
mith &
FulhamWard Area
1

College Park and
Old Oak

There is a tendency for surface water to flow off the higher groundof Wormwood Scrubs in College Park and Old Oak. Therefore, an
option would be to intercept these flows and so prevent the runoff ofsurface water to the more vulnerable residential and commercial
areas to the south. This could be accomplished through the creationof a detention basin or flood storage bunds along the southern
extent of Wormwood Scrubs and Old Oak Common. These would
act to intercept the main flow paths runoff off the park area to thenorth of the Linford Christie Stadium, HM Wormwood Scrubs Prison
and to the north of Braybrook Street.
Three flood storage bunds were modelled within the Wormwood
Scrubs area. During the 5% AEP modelled rainfall event, these 3
storage areas have been modelled to collectively retain

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Old Oak Common and Park Royal

Borough

CDA

APPENDIX C: Strategic Level Flood Risk Assessment

Location

Preferred Option
approximately 5,800m3 of surface water runoff that has beenintercepted from the Wormwood Scrubs area. This has a significant
effect on the flood depths downstream, with the most notablebenefit of a 0.1-0.15m reduction in flood depths within the area ofthe Hammersmith Hospital. Further to the west, the flood storagebund shows a reduction in flood depths of up to 0.15m along
Wulfstan Street for the same return period event. The flood storage
bunds have been modelled to effectively retain surface water runoff
for all of the modelled return period events. The greatest flood depth
reduction can be seen for the 1% and 0.5% AEP events, during
which the greatest volumes of surface water are retained.
Indicative costs for the construction of these flood storage areas
have been undertaken utilising cost estimates provided in theSpons: Civil Engineering and Highways (2013).Wormwood Scrubs
and Old Oak Common: The construction of the three flood storage
bunds would cost in the region of £51k to £100k.

Wormwood Scrubs Surface Water Management Scheme

The LBHF undertook a study in 2012 to assess the feasibility of, and the costs and benefits associated with ascheme to attenuate surface water run-off and improve the quality of the open space and biodiversity of
Wormwood Scrubs8.
The study involved the following key tasks:
A hydrological assessment to calculate the storage volumes required to attenuate surface run-off,Calculation of the design, construction and maintenance costs of the scheme,
Economic appraisal of the scheme,
Assessment of the contaminated land on-site,
Cultural heritage appraisal.
An Outline Design for the wetland area was completed based on the wetland storage volumes calculated by thehydrological assessment. The proposals include an interlinked system of attenuation ponds, wetlands and wet
swales, which focuses on maximising benefits for surface water management, biodiversity and amenity.
The design, construction and maintenance costs of the wetland scheme were calculated assuming a 1:30 year
and 1:100 year design horizon. Detailed design costs were estimated as £130,000, and construction costs were
estimated to be £1.73 million (for a 1:30 year design) and £2.18 million (for a 1:100 year design). Ongoing
maintenance costs were been calculated as £4,000 per year and the design life of the wetland is estimated to be
75 years.
The cost-benefit analysis identified the reduction in flood damages to Wormwood Scrubs prison, Linford Christie
stadium and Hammersmith Hospital and indicated that the benefit-cost ratios would be 14.32 and 13.33 for a 1:30
year and 1:100 year design horizon, respectively. However, the outcomes from the Defra Partnership Funding
Calculator indicated that external funding contributions or a reduction in scheme cost would be required to makethe scheme eligible for Flood Defence Grant in Aid funding.
Proposals for managing surface water runoff from the development within the Study area could potentially be
combined with a wider scheme to benefit property and areas at risk of flooding to the south of Wormwood Scrubs.

8

Halcrow, 27 July 2012, London Borough of Hammersmith & Fulham - Wormwood Scrubs Surface Water Management Scheme –Feasibility Study

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Old Oak Common and Park RoyalAPPENDIX C: Strategic Level Flood Risk Assessment

Potential Opportunities and Recommendations
A drainage study is being carried out by Thames Water in order to establish the flow characteristics andcapacity in the River Brent and associated drainage system. On completion of this study, this will provide
detail information on areas affected by flooding and solutions. The study is being carried out on behalf ofNorth Brent and Harrow Flood Stakeholders Group. This group comprises of representatives from Brent,
Harrow, Thames Water and Environment Agency; this study may identify capacity for discharge ofattenuated surface water from Park Royal to the River Brent.
In managing residual risk from canal breach flooding, it is recommended that development in Old Oak
Common is set back from the canal. This is in keeping with the current masterplan proposals to create agreen corridor along the canal;
Development in the north west of Park Royal should be set back from the River Brent edges to enable arange of additional flood risk management options for the wider Brent corridor;
Areas of green space proposed within the early Old Oak Common masterplan could be re-configured tocoincide with areas of existing ponding to act as areas of dispersed attenuation storage.
LBHF has considered the feasibility of providing storm water attenuation within Wormwood Scrubs to
reduce the risk of flooding to property and infrastructure to the south of the Scrubs within the Borough.
This could be combined with storm water attenuation from the Opportunity Area to provide benefit both to
the Opportunity Area and the wider drainage catchment to the south.
Thorough retrofit of the Park Royal section of the site, there are opportunities for Blue Corridors (viaraised kerbs) particularly around the high risk areas and associated roads identified to the south of thecanal within the current industrial areas.

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Old Oak Common and Park Royal

Integrated W ater Management Strategy

APPENDIX D
Plot Grouping Figures

.

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522000

523000´

183000Service Layer Credits: Source: Esri, DigitalGlobe,
GeoEye, Earthstar Geographics, CNES/Airbus DS,
USDA, USGS, AEX, Getmapping, Aerogrid, IGN,
IGP, swisstopo, and the GIS User Community

Plot Area Original Area ofReference Area (ha) Space (ha)
1
5.78
2.41
2
4.39
1.69
3
27.50
13.76
4
6.51
3.31
5
7.60
3.03
6
31.36
14.64
7
26.18
15.50
8
6.71
3.49

1
2

V

9
7
10

6
8

3

11

41
M

12

42 L

19

15

28
U 20

16

13

17

42

T

K

54

89
91

55

6

49

Q
93

182000

94

97
98

7

103

100

65
102

N

108
B

109

40

77

78

79

81

82

83

84

4

80
85

88
86

5

87

D
70

113
113

C

39

71

105

110

38

72

64

63

106
107

66

33

74

67

R

37

36

76

73

101

25

75

59

58

35

62

61

95
99

104

57

56

23

32

46

50

60

92

45

E

31
34

J

F
53

2

29

24

48
52

22

21

30

S

G

51

27
H

14

44

P

26

18

5

47

96

3

4

43

90

1

113
113
113

109

69
115

68

114
116
117

119
111

124
123

118
122

120
112

A
121

125
128

8

127
126
129

130

Contains OS data © Crown copyright [and database right] (2015)
Last saved by: maceyg
Last plotted:02/09/2015
Coordinate System: British National Grid (OSGB 1936)
Filename: P:\UKCDF1-IE\Projects\!GIS Management\Gerwyn Projects\Projects\2015\Old Oak Common\G2.ArcGIS\ArcMap\Figure 1 - Old Oak Plots_v3.mxd

0

200

400

m

This drawing has been prepared for the use of AECOM's client. It may not be used, modified, reproduced or relied upon by third parties, except as agreed by AECOM or as required by law. AECOM accepts no responsibility, and denies any liability whatsoever, to any party that uses or relies on this drawing without AECOM's express written consent. Do not scale this document. All measurements must be obtained from the stated dimensions.

521000PROJECTOLD OAK COMMON
AND ROYAL PARKDEVELOPMENTCLIENT

OLD OAK COMMON
DEVELOPMENTCORPORATIONCONSULTANT
AECOM Limited
1 Callaghan Square
Cardiff, CF10 5BT+44 (0)29 2067 4600 tel
www.aecom.com
LEGEND

Plot Boundaries

Old Oak Common Plots
Development
complete

New London
Overground Station –no over station
development
Green Space
Open Space

ISSUE/REVISION

A

I/R

02/09/2015
DATE

ISSUED FOR INFORMATIONDESCRIPTION

KEY PLANCONTRACT NUMBERXXXXXXXXXXSHEET TITLE

FIGURE 1
Old Oak Common - Plot Locations
Scale at A3: 1:7,898.35
SHEET NUMBER
Figure 1 - Old Oak Plots_v3

v1

520000

521000522000523000´

184000Service Layer Credits: Source: Esri, DigitalGlobe,
GeoEye, Earthstar Geographics, CNES/Airbus DS,
USDA, USGS, AEX, Getmapping, Aerogrid, IGN,
IGP, swisstopo, and the GIS User Community

2

1830001

3
5
4

Old Oak Common

1810001820006

Contains OS data © Crown copyright [and database right] (2015)
Last saved by: davidac
Last plotted:11/09/2015
Coordinate System: British National Grid (OSGB 1936)
Filename: F:\Library\GIS_DATA\Projects\Counters_Creek\Maps\150911_ParkRoyalSubCatchments.mxd

0

230

460
m

This drawing has been prepared for the use of AECOM's client. It may not be used, modified, reproduced or relied upon by third parties, except as agreed by AECOM or as required by law. AECOM accepts no responsibility, and denies any liability whatsoever, to any party that uses or relies on this drawing without AECOM's express written consent. Do not scale this document. All measurements must be obtained from the stated dim ensions.

519000PROJECTOLD OAK COMMON
AND ROYAL PARKDEVELOPMENTCLIENT

OLD OAK COMMON
DEVELOPMENTCORPORATIONCONSULTANT
AECOM Limited
1 Callaghan Square
Cardiff, CF10 5BT+44 (0)29 2067 4600 tel
www.aecom.com
LEGEND

Catchment
Green Space
WaterbodyRail Track
Residential
Proposed Residential

ISSUE/REVISION

A

11/09/2015

I/R

DATE

ISSUED FOR INFORMATIONDESCRIPTION

KEY PLANCONTRACT NUMBERXXXXXXXXXXSHEET TITLE

Figure 4 - Park Royal
Sub-Catchments
Scale at A3: 1:13,500
SHEET NUMBER
150911_ParkRoyalSubCatchments

v1

Old Oak Common and Park Royal

Integrated W ater Management Strategy

APPENDIX E
Rainfall Runoff Calculations

.

AECOM

83

Starting Information

HS2 and New Rail station to be constructed next to Old Oak Common.
High density housing proposed beside common and in surrounding area.
Area split into different plots.
Climate change factor (+30%)- residential area (+30%), commerical area (+20%)
Greenfield run off rates - Not impermeable
Microdrainage used to calculate the permitted outflow.
- ihs 124 methodology- 50 hec or more catachment (l/s/hec)
M5-60 - M= how many years, 5= no. of years, 60= 60 min duration
All coordinates obatined from www.streetmaps.co.uk

AECOM Ltd
Aecom House
63-77 Victoria Street
St Albans Herts AL1...
Date 26.10.2015
File Greenfield Run-o...
XP Solutions

Page 1
Old Oak Common andPark Royal
Greenfield Run-off
Designed by JHC
Checked by MD
Source Control 2013.1.1
IH 124 Mean Annual Flood
Input

Return Period (years)
100
Soil
0.450
Area (ha) 50.000
Urban
0.000
SAAR (mm)633 Region Number Region 6
Resultsl/s

QBAR Rural
QBAR Urban

195.3
195.3

Q100 years

622.9

Q1 year 166.0
Q2 years 172.0
Q5 years 249.9
Q10 years 316.3
Q20 years 391.2
Q25 years 419.4
Q30 years 442.5
Q50 years 511.6
Q100 years 622.9
Q200 years 732.2
Q250 years 767.4
Q1000 years 1007.6©1982-2013 Micro Drainage Ltd

Sections
Old Oak - Future

Total Area (ha)
1
2
3
4
5
6
7
8

Old Oak - Existing

5.78
4.39
27.5
6.51
7.6
31.36
26.18
6.71

Total Area (ha)
1
2
3
4
5
6
7
8

5.78
4.39
27.5
6.51
7.6
31.36
26.18
6.71

Total Area (m²)
Area of Open Space (ha)Area of Open Space (m²)
Impermeable (ha)Impermeable (m²)
Easting/Northing
57800
2.41
24100
3.37
33700 522240, 183165
4390
1.69
16900
2.7
27000 522450, 182534
27500
13.76
13760013.74137400 521950, 182559
6510
3.31
33100
3.2
32000 522660, 182364
7600
3.03
30300
4.57
45700 521975, 182054
31360
14.64
14640016.72
167200 521495, 182234
26180
15.5
15500010.68106800 521072, 182049
6710
3.49
34900
3.22
32200 521299, 181609

Total Area (m²)
Area of Open Space (ha)Area of Open Space (m²)
Impermeable (ha)57800
0.911039936
9110
43900
0.248477545
2485
2750002.186055697
21861
65100
0.28682015
2868
76000
0.477190111
4772
3136001.881702719
18817
2618001.69456418
16946
67100
0.034813364
348

Impermeable (m²)
5
4
27
6
7
31
26
7

53275
41453
26810962831
72438
30552226123368682

Lat/Lon51.534,-0.239
51.528449,-0.236198
51.528782,-0.243394
51.526876,-0.233232
51.524238,-0.243208
51.525959,-0.250061
51.524387,-0.256219
51.520384,-0.253100

CALCULATION SHEET
Project:

60439696

Ref:
Section:Made by:Checked by:

Date:

Lilian Gowans
Jon Curry

21 October 2015

Date:

Approved By:

Date:

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 1.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M20

M30

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Extract of Wallingford Procedure Volume 1

RAINFALL DETAILS
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowance

M5-D

Z2

(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

5

CALCULATION SHEET
Project:

60439696

Ref:
Section:Made by:Date:

Checked by:

Date:

Lilian Gowans
Jon Curry
Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

21 October 2015
2

33700 m
Lake
100 %
N/A m
N/A m
N/A m
1
1
3
N/A m
12.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m3)

(m )

3

(m )

5
10
15
30
60
120
240
360
600
1440
2880

651
940
1137
1475
1864
2217
2544
2702
3010
3588
4058

13
25
38
76
152
303
607
910
1517
3640
7279

638
915
1099
1399
1712
1914
1937
1792
1493
0
0

Maximum Storage required

3

1937 m3\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

6

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Lilian Gowans
Jon Curry

Checked by:Date:

21 October 2015
26 October 2015

Date:

Approved By:

Date:

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 2.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M20

M30

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Extract of Wallingford Procedure Volume 1

RAINFALL DETAILS
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

M5-D

Z2

(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)
From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowance

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

7

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Date:

Checked by:

Date:

Lilian Gowans
Jon Curry
Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

21 October 2015
26 October 2015
2

27000 m
Lake
100 %
N/A m
N/A m
N/A m
1
1
3
N/A m
12.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m )

3

(m )

3

(m )

5
10
15
30
60
120
240
360
600
1440
2880

521
753
911
1182
1493
1776
2038
2165
2411
2875
3251

10
20
30
61
122
243
486
729
1215
2916
5832

511
733
881
1121
1372
1533
1552
1436
1196
0
0

Maximum Storage required

31552 m3\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

8

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Lilian Gowans
Jon Curry

Checked by:Date:

21 October 2015
26 October 2015

Date:

Approved By:

Date:

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 3.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M20

M30

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Extract of Wallingford Procedure Volume 1

RAINFALL DETAILS
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

M5-D

Z2

(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)
From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowance

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

9

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Date:

Checked by:

Date:

Lilian Gowans
Jon Curry
Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

21 October 2015
26 October 2015
2137400 m
Lake
100 %
N/A m
N/A m
N/A m
1
1
3
N/A m
12.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m )

3

(m )

3

(m )

5
10
15
30
60
120
240
360
600
1440
2880

2653
3833
4636
6015
7600
9040
10371
11017
12271
14629
16543

52
103
155
309
618
1237
2473
3710
6183
14839
29678

2602
3730
4481
5706
6981
7804
7897
7307
6088
0
0

Maximum Storage required

37897 m3\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

10

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Lilian Gowans
Jon Curry

Checked by:Date:

21 October 2015
26 October 2015

Date:

Approved By:

Date:

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 4.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M20

M30

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Extract of Wallingford Procedure Volume 1

RAINFALL DETAILS
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

M5-D

Z2

(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)
From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowance

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

11

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Date:

Checked by:

Date:

Lilian Gowans
Jon Curry
Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

21 October 2015
26 October 2015
2

32000 m
Lake
100 %
N/A m
N/A m
N/A m
1
1
3
N/A m
12.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m )

3

(m )

3

(m )

5
10
15
30
60
120
240
360
600
1440
2880

618
893
1080
1401
1770
2105
2415
2566
2858
3407
3853

12
24
36
72
144
288
576
864
1440
3456
6912

606
869
1044
1329
1626
1817
1839
1702
1418
0
0

Maximum Storage required3

1839 m3\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

12

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Lilian Gowans
Jon Curry

Checked by:Date:

21 October 2015
26 October 2015

Date:

Approved By:

Date:

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 5.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M20

M30

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Extract of Wallingford Procedure Volume 1

RAINFALL DETAILS
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

M5-D

Z2

(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)
From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowance

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

13

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Date:

Checked by:

Date:

Lilian Gowans
Jon Curry
Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

21 October 2015
26 October 2015
245700 m
Lake
100 %
N/A m
N/A m
N/A m
1
1
3
N/A m
12.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m )

3

(m )

3

(m )

5
10
15
30
60
120
240
360
600
1440
2880

883
1275
1542
2001
2528
3007
3449
3664
4082
4866
5502

17
34
51
103
206
411
823
1234
2057
4936
9871

865
1241
1490
1898
2322
2596
2627
2430
2025
0
0

Maximum Storage required

3

2627 m3\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

14

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Lilian Gowans
Jon Curry

Checked by:Date:

21 October 2015
26 October 2015

Date:

Approved By:

Date:

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 6.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M20

M30

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Extract of Wallingford Procedure Volume 1

RAINFALL DETAILS
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

M5-D

Z2

(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)
From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowance

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

15

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Date:

Checked by:

Date:

Lilian Gowans
Jon Curry
Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

21 October 2015
26 October 2015
2167200 m
Lake
100 %
N/A m
N/A m
N/A m
1
1
3
N/A m
12.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m )

3

(m )

3

(m )

5
10
15
30
60
120
240
360
600
1440
2880

3229
4664
5641
7319
9248
11001
12620
13406
14933
17802
20131

63
125
188
376
752
1505
3010
4514
7524
18058
36115

3166
4539
5453
6943
8495
9496
9610
8892
7409
0
0

Maximum Storage required

39610 m3\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

16

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Lilian Gowans
Jon Curry

Checked by:Date:

21 October 2015
26 October 2015

Date:

Approved By:

Date:

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 7.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M20

M30

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Extract of Wallingford Procedure Volume 1

RAINFALL DETAILS
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

M5-D

Z2

(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)
From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowance

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

17

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Date:

Checked by:

Date:

Lilian Gowans
Jon Curry
Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

21 October 2015
26 October 20152106800 m
Lake
100 %
N/A m
N/A m
N/A m
1
1
3
N/A m
12.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m )

3

(m )

3

(m )

5
10
15
30
60
120
240
360
600
1440
2880

2062
2979
3603
4675
5907
7027
8061
8563
9538
11371
12859

40
80
120
240
481
961
1922
2884
4806
11534
23069

2022
2899
3483
4435
5426
6066
6139
5680
4732
0
0

Maximum Storage required

36139 m3\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

18

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Lilian Gowans
Jon Curry

Checked by:Date:

21 October 2015
26 October 2015

Date:

Approved By:

Date:

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 8.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M20

M30

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Extract of Wallingford Procedure Volume 1

RAINFALL DETAILS
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

M5-D

Z2

(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)
From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowance

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

19

CALCULATION SHEET
Project:

60439696

Ref:
Section:1

Made by:Date:

Checked by:

Date:

Lilian Gowans
Jon Curry
Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

21 October 2015
26 October 2015
232200 m
Lake
100 %
N/A m
N/A m
N/A m
1
1
3
N/A m
12.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m )

3

(m )

3

(m )

5
10
15
30
60
120
240
360
600
1440
2880

622
898
1086
1410
1781
2119
2430
2582
2876
3428
3877

12
24
36
72
145
290
580
869
1449
3478
6955

610
874
1050
1337
1636
1829
1851
1712
1427
0
0

Maximum Storage required3

1851 m3\\Ukcrd1fp004\ukcrd1fp004-v1ie\projects\Water Resources - OPDC IWMS\WiP\Report\V2 appendices\Appendix E_runoff calcs\OOC&PR storage V2.xls

20

Total Storage Needed for Old Oak
Plot
1
2
3
4
5
6
7
8
Total

Maximum Storage Required (m³)
1937
1552
7897
1839
2627
9610
6139
1851
33452

SectionsRoyal Parks
1
2
3
4
5
6

Plots (m²)
Easting/Northing
75,143.28 519194, 183419
986,702.09 519489, 183674
274,061.19 521434, 182969
115,942.43 521284, 182669
1,967,278.15 520834, 182887
703,181.41 520306, 182047

Lat/Lon51.537099,-0.282813
51.539328,-0.278475
51.532578,-0.250687
51.529914,-0.252952
51.531969,-0.259361
51.524533,-0.267256

Project:60439696

Ref:
Section:1

Made by:Lilian Gowans

Date:

Checked by: Jon Curry

Date:

Approved By:

Date:

21 October 2015
26 October 2015

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 1.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M30

M20

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

Extract of Wallingford Procedure Volume 1

RAINFALL DETAILS
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)
From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowance

M5-D

Z2

(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

275,143 m
Lake
100 %
N/A m
N/A m
N/A m
1
1
3
N/A m
12.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m 3)

(m 3)

(m 3)

5
10
15
30
60
120
240
360
600
1440
2880

1451
2096
2535
3289
4156
4944
5672
6025
6711
8001
9047

28
56
85
169
338
676
1353
2029
3381
8115
16231

1423
2040
2451
3120
3818
4268
4319
3996
3330
0
0

Maximum Storage required

4319 m3

Project:60439696

Ref:
Section:1

Made by:Lilian Gowans
Jon Curry

Checked by:Date:

21 October 2015
26 October 2015

Date:

Approved By:

Date:

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 1.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M20

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

Extract of Wallingford Procedure Volume 1

v
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

M5-D

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)
From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowanceZ2(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

M30

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

986,702 m 2
Lake
100 %
N/A m
N/A m
N/A m
1
1
N/A m 312.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m3)

(m3)

(m3)

5
10
15
30
60
120
240
360
600
1440
2880

19055
27526
33290
43194
54574
64920
74473
79114
88124
105057118801

370
740
1110
2220
4440
8880
17761
26641
44402
106564213128

18685
26786
32180
40974
50134
56040
56713
52473
43722
0
0

Maximum Storage required

56713 m3

Project:60439696

Ref:
Section:1

Made by:Lilian Gowans
Jon Curry

Checked by:Date:

21 October 2015
26 October 2015

Date:

Approved By:

Date:

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 1.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M20

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

Extract of Wallingford Procedure Volume 1

RAINFALL DETAILS
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)
From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowance

M5-D

Z2

(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

M30

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

274,061 m 2
Lake
100 %
N/A m
N/A m
N/A m
1
1
N/A m312.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m3)

(m3)

(m3)

5
10
15
30
60
120
240
360
600
1440
2880

5293
7646
9247
11997
15158
18032
20685
21974
24477
29180
32998

103
206
308
617
1233
2467
4933
7400
12333
29599
59197

5190
7440
8938
11381
13925
15565
15752
14575
12144
0
0

Maximum Storage required

15752 m3

Project:60439696

Ref:
Section:1

Made by:Date:

Lilian Gowans

Checked by: Jon Curry

Date:

Approved By:

Date:

21 October 2015
26 October 2015

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 1.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M20

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

Extract of Wallingford Procedure Volume 1

RAINFALL DETAILS
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)
From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowance

M5-D

Z2

(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

M30

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

2

115,942 m
Lake
100 %
N/A m
N/A m
N/A m
1
1
3
N/A m
12.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m 3)

(m 3)

(m 3)

5
10
15
30
60
120
240
360
600
1440
2880

2239
3234
3912
5076
6413
7628
8751
9296
10355
12345
13960

43
87
130
261
522
1043
2087
3130
5217
12522
25044

2196
3148
3781
4815
5891
6585
6664
6166
5138
0
0

Maximum Storage required

6664 m3

Project:60439696

Ref:
Section:1

Made by:Lilian Gowans
Jon Curry

Checked by:Date:

21 October 2015
26 October 2015

Date:

Approved By:

Date:

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 1.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M20

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

Extract of Wallingford Procedure Volume 1

RAINFALL DETAILS
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)
From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowance

M5-D

Z2

(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

M30

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

1,967,278 m 2
Lake
100 %
N/A m
N/A m
N/A m
1
1
N/A m 312.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m3)

(m3)

(m3)

5
10
15
30
60
120
240
360
600
1440
2880

37991
54882
66374
86120
108810129437148484
157737175700209463236865

738
1475
2213
4426
8853
17706
35411
53117
88528
212466424932

37253
53406
64161
81693
99957
11173211307310462087173
00Maximum Storage required

113073 m3

Project:60439696

Ref:
Section:1

Made by:Lilian Gowans
Jon Curry

Checked by:Date:

21 October 2015
26 October 2015

Date:

Approved By:

Date:

DESIGN OF STORMWATER STORAGE FACILITY
Design of stormwater storage facility for section 1.

RAINFALL DETAILS
Wallingford Procedure
Table 6.2
Ratio Z2 (Relationship between rainfall of return period T (MT) and M5 - England and Wales)
M5 Rainfall
(mm)

M1

5
10
15
20
25
30
40
50
75
100
150
200

0.62
0.61
0.62
0.64
0.66
0.68
0.70
0.72
0.76
0.78
0.78
0.78

M2

M3

M4

M5

M10

M20

0.79
0.79
0.80
0.81
0.82
0.83
0.84
0.85
0.87
0.88
0.88
0.88

0.89
0.90
0.90
0.90
0.91
0.91
0.92
0.93
0.93
0.94
0.94
0.94

0.97
0.97
0.97
0.97
0.97
0.97
0.97
0.98
0.98
0.98
0.98
0.98

1.02
1.03
1.03
1.03
1.03
1.03
1.02
1.02
1.02
1.02
1.01
1.01

1.19
1.22
1.24
1.24
1.24
1.22
1.19
1.17
1.14
1.13
1.12
1.11

1.36
1.41
1.44
1.45
1.44
1.42
1.38
1.34
1.28
1.25
1.21
1.19

Extract of Wallingford Procedure Volume 1

RAINFALL DETAILS
M5-60
r
CC
DURATION

21 mm
0.43
30%
Z1

From Wallingford Procedure, Volume 3; Maps. Rainfall depth (M5-60 minutes)
From Wallingford Procedure, Volume 3; Maps. Ratio of M5-60 minutes to M5-two day rainfall
Climate change allowance

M5-D

Z2

(M5-60 x Z1)(mm)(minutes)

5
10
15
30
60
120
240
360
600
1440
2880

M30

M50

M100

1.56
1.65
1.70
1.73
1.72
1.70
1.64
1.58
1.47
1.40
1.33
1.30

1.79
1.91
1.99
2.03
2.01
1.97
1.89
1.81
1.64
1.54
1.45
1.40

(interpolated)

0.38
0.53
0.63
0.80
1.00
1.20
1.40
1.50
1.70
2.10
2.45

7.98
11.13
13.23
16.80
21.00
25.20
29.40
31.50
35.70
44.10
51.45

M100-D(M5-D x Z2)
(mm)

1.86
1.93
1.96
2.00
2.03
2.01
1.97
1.96
1.92
1.86
1.80

14.9
21.5
26.0
33.7
42.5
50.6
58.1
61.7
68.7
81.9
92.6

M100-D plus CCR(M5-D x Z2)
(mm)

19.3
27.9
33.7
43.8
55.3
65.8
75.5
80.2
89.3
106.5
120.4

I-O=S
I = inflow
O = outflow
S = storage
I=AxR
A = impermeable contributing area
R = total rainfall
O = as50 x f x D
as50 = internal surface area of soakaway to 50% depth (excluding base)f = soil infiltration rate
D = storm duration

1.46
1.53
1.57
1.59
1.58
1.56
1.51
1.46
1.38
1.33
1.27
1.25

Contributing Area
Type of Storage
Void Ratio
LengthWidth
Depth
Number of
Safety Factor
Free Volume (Available Storage)
Permitted outflow

703,181 m 2
Lake
95 %
N/A m
N/A m
N/A m
1
1
N/A m 312.5 l/s/ha

DURATION

INFLOW(A x R)

OUTFLOW(as50 x f x D)

REQUIRED STORAGE(I - O)(minutes)

(m3)

(m3)

(m3)

5
10
15
30
60
120
240
360
600
1440
2880

13579
19617
23725
30783
38893
46266
53074
56381
62802
74870
84665

264
527
791
1582
3164
6329
12657
18986
31643
75944
151887

13316
19090
22934
29200
35729
39937
40417
37395
31159
0
0

Maximum Storage required

40417 m3

Total Storage Needed for Old Oak
Plot

Maximum Storage Required (m³)
1
2
3
4
5
6

Total

4319
56713
15752
6664
11307340417
236937

Old Oak Common and Park Royal

Integrated W ater Management Strategy.

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