Drainage Strategy in Support of Commercial Development At

Drainage Strategy In support of Commercial Development at

40 St. Thomas Street OXFORD OX1 1JP

Tony Lee March 2021 Revision [0]

Drainage Strategy 40 St. Thomas Street

Contents Amendments ...... 2 References ...... 2 Introduction ...... 3 Existing Drainage ...... 3 Site Geology ...... 4 Ground Water ...... 4 Topography ...... 4 Design Objective ...... 4 Development Drainage Proposals ...... 5 Surface Water Drainage ...... 5 Infiltration Feasibility ...... 5 Sustainable Drainage Hierarchy ...... 5 Surface Water Drainage Strategy ...... 8 Foul Water Drainage ...... 9 Residual Flood Risk ...... 9 SuDS Maintenance ...... 10 Appendices ...... 11

Drainage Strategy 40 St. Thomas Street

Amendments Revision Date Description 0 19th March 2021 First Issue

References Reference Title

A CIRIA Publication 753 – The SUDS Manual (2015) B Sewers for Adoption 7th Edition (Wrc 2012) C Part H of the Building Regulations (2015) D Flood Risk Assessment (RSPD Ltd March 2021)

Drainage Strategy 40 St. Thomas Street

Introduction

This Drainage Strategy has been developed in support of a proposed planning application for a three storey office development. The site is located at 40 St. Thomas Street, OXFORD OX1 1JP Grid Reference: 450650, 206170

This document is to provide details of the methods of drainage to be used for the Surface and Foul Water Drainage.

The aim of this Drainage Strategy is also to incorporate and adopt Best Management Practices (BMP’s) for Sustainable Urban Drainage Systems (SUD’s) in accordance with Site Specific Technical Reports and Published Documents referenced in Page (ii).

It is proposed to demolish the existing children’s nursery and construct a 3 storey office building with associated paving and soft landscaping. The area of soft landscaping will reduce the impermeable area of the site by over 100m2 (25%).

A Location Plan and layout of the proposed scheme can be found in the appendices of this document.

Existing Drainage

The Thames Water sewer records indicate an adopted foul sewer running within St Nicholas Road at a depth between 1.6 & 2.3m. There is an adopted surface water sewer within Hollybush Row at an approximately depth of 1.6m. There are gullies within St Thomas Street and chambers that are not indicated on Thames Water sewer records. It is presumed that there is a highway drain in St Thomas Street that outfalls to Thames Water Manhole 6103. The surface water runoff from the roof of the existing nursery building and the surrounding play areas drains to the private foul drainage network within the site. It is presumed that this outfalls to the adopted foul sewer in St Thomas Street. A copy of the Thames Water sewer records can be found in the appendices of this document.

Drainage Strategy 40 St. Thomas Street

Site Geology

Review of British Geological Society Borehole records show that a borehole was undertaken approximately 50m to the south east of the site for the Oxford Relief Road Scheme in 1966. This borehole records approximately 1.5m of sandy, silty clay overlying 3m of sands & gravel which are further underlain by Oxford Clay. • Clay – soft yellow brown organic calcareous sandy silty clay. • Sand and Gravel Member – Medium yellow brown clayey sand and fine to medium gravel. • Oxford Clay – stiff becoming hard calcareous clay A plan of the local geological formations can be found in the appendices of this report.

Ground Water

Records of local historical boreholes in the vicinity of this application site were found dating from 1969. Groundwater is not mentioned on the deeper of the three boreholes but the nearest borehole was drilled to 4.27m and water was encountered at 2.28m. All three boreholes were sunk in November 1969. Groundwater flooding is not considered an issue.

Topography

The site is currently a children’s day nursery. The nursery is a two-storey structure located towards the centre of the site. The nursery building is surrounded by impermeable play areas surfaces with either asphalt or rubber safety surfacing. The topography of the overall site is relatively flat with levels set at around the 57.30m AOD level. The site is approximately 430m2 in area and is 100% impermeable.

Design Objective

Sustainable Drainage techniques (SuDS) covers a range of approaches to manage surface water runoff so that- ‘Surface water arising from a developed site should, as far as is practicable, be managed in a sustainable manner to mimic the surface water flows arising from the site prior to the proposed development, while reducing the flood risk to the site itself and elsewhere, taking climate change into account.’

Drainage Strategy 40 St. Thomas Street

Drainage shall also be designed with the appropriate factor of safety, in accordance with the tables set out in CIRIA Publication 753 “The SUDS Manual”.

The proposed sustainable drainage techniques for the development should accommodate the peak rainfall event for a 1 in 100 year storm event with an additional allowance for climate change. Table 5 of NPPG recommends for developments that have a life expectancy beyond 2085 that an additional factor of 40% is applied to the peak volume of runoff.

Development Drainage Proposals Surface Water Drainage The development site area is approximately 430m2, of which 100% is impermeable. The existing runoff rates from the site are indicated below.

Return period Runoff rate l/s 1 in 1 year 4.7 1 in 30 year 6.9 1 in 100 year 15.1

Infiltration Feasibility The thickness of the silty sandy clay underlying the site prevents the use of shallow infiltration techniques such as infiltration permeable paving. Building Regulations requires that any soakaways are position a minimum of 5m away from any structures. The size and shape of the site, and the orientation of the proposed development and the adjacent building means it is not possible to meet this requirement.

Sustainable Drainage Hierarchy A hierarchical approach has been undertaken in consideration of the application of SuDS in relation to the development. This is in order to meet the design philosophy of ensuring that surface water run-off is managed as close to its source as possible and the existing situation is replicated as closely as possible. The following drainage hierarchy has been undertaken with reference to the procedures

Drainage Strategy 40 St. Thomas Street set out in the SuDS Manual (CIRIA C753, 2015) to assess the viability of the application of SuDS techniques to this scheme: 1. store rainwater for later use 2. use infiltration techniques, such as porous surfaces in permeable strata areas 3. Attenuate rainwater in ponds or open water features for gradual release to a watercourse. 4. attenuate rainwater by storing in tanks or sealed water features for gradual release to a watercourse, 5. discharge rainwater direct to a watercourse 6. discharge rainwater to a surface water drain 7. discharge rainwater to the combined sewer. The sustainable drainage hierarchy shown above is intended to ensure that all practical and reasonable measures are taken to manage surface water higher up the hierarchy (1 being the highest) and that the amount of surface water managed at the bottom of the hierarchy is minimised. Sustainable urban drainage systems have been considered for this development unless there are practical reasons for not doing so. Such reasons include the local ground conditions or density of development. The site-specific drainage hierarchy checklist considered for the drainage design for this development is detailed on the next page.

Drainage Strategy 40 St. Thomas Street

SUDS Comments

rate

OPTIONS

flow

final

for

design

reduction

Potential control Volume Maintenance requirement Space requirement Cost Included detailed Rainwater Rainwater from roof runoff L M H L H N harvesting collected for re-use. Cost benefit considerations Water butts Rainwater collection from roof L L L L L N runoff. Included in final design Living roofs Vegetated roofs that reduce M L M L H N runoff volume and rate Bio-retention Shallow vegetated areas to L L M M L N retain and treat runoff. Constructed Waterlogged areas that can support M L H H/M M N wetlands aquatic vegetation. Replicates existing conditions and provides ecological benefit. Swales Shallow grassed drainage H M L M/H L N channels. Replicates existing conditions Soakaways Sub surface structures that H H L L M N dispose of water via infiltration. Permeable Surface that infiltrate through H H M L M Y pavements surface. Retains pollutants. Tanked Oversized pipes or cellular H L L M M/H Y storage storage. systems Infiltration Depressions in the ground to H H H/M H M/L N basins store and release water through infiltration Detention Temporary retention of runoff H L M H M/L N basins with controlled discharge

Table 1 Drainage design hierarchy (SuDS techniques considered for use on this scheme)

Drainage Strategy 40 St. Thomas Street

It should be noted that where the SuDS techniques are noted as feasible or possible it does not necessarily follow that they will all be used. Reference should be made to the drainage strategy drawing in the appendices which indicates the proposed strategy. The consideration of the SuDS hierarchy demonstrates that given the limitations within the site boundary, infiltration techniques can be utilised so that the proposed on-site drainage can incorporate water quality benefits whilst addressing the need for runoff rate and volume reductions. Surface Water Drainage Strategy This drainage strategy is not intended to provide a detailed design for the drainage system to serve the proposed development, but to show that a proposed system is feasible in principle given the storage volume required and land availability. A detailed drainage scheme will be submitted to the Local Planning Authority (LPA) prior to the commencement of development and/or to discharge the appropriate planning condition. The main contributory factor to surface water runoff is usually from hard standing and roof areas. Whilst the existing development is 100% impermeable, the proposed redevelopment will introduce soft landscaping over 30% of the area of the site. This will have a corresponding effect on runoff rates and volumes. The implementation of SuDS techniques for the impermeable areas will further reduce runoff rates. So as not to inhibit access to the foul drains around the building the use of a tanked permeable paving system for the pathways has been discounted. Instead, the roof water will be connected to a piped system which will discharge via a flow control chamber before connecting to the existing public sewer. An off-line geocellular flood storage tank will be built under the paving at the south eastern corner of the building to hold back all storm events up to and including the 1 in 100 year + 40%. Additionally, pre-treatment of the roof run-off will be provided by the inclusion of a catch pit silt traps ahead of the storage tank. It is desirable to aim to reduce post development run off rates to greenfield rates. This is not practicable for this site as the relatively small area leads to value of QBAR of 0.5l/s which would require a flow control with a diameter less than the minimum recommended so a Hydrobrake vortex flow control device has been chosen that will give the maximum possible reduction in flows without increasing the risk of blockage and on-site flooding. The table below compares the run-off rates to existing. Return period Existing l/s Runoff rate l/s Reduction % 1 in 1 year 4.7 1.9 60 1 in 30 year 11.6 1.9 84 1 in 100 year 15.1 2.1 86 Full drainage calculations are contained within the appendices.

Drainage Strategy 40 St. Thomas Street

The approach to the building entrance is to be permeable block paving. As the roof water will be piped there is no need to use an impermeable liner beneath allowing soakage into the formation.

The controlled discharge from the surface water flow control chamber is to be connected to the highway drain in St. Thomas Street.

Foul Water Drainage The Thames Water sewer records show there is a public foul water sewer in St. Thomas Street which is some 1.6m deep. The foul and surface water discharge from the existing buildings is connected to the public foul sewer.

Foul water drainage for the proposed development site will be designed and constructed to accord with the requirements of Building Regulations Approved Document H.

The existing connection to the public foul sewer can be reused if it can be shown to be sound.

Residual Flood Risk

Referring to the FRA by this company. Flood mapping confirms there is a marginal flood risk to the proposed site, as it is situated just within Flood Zone 2. Full details and mapping are provided in the appendices of the FRA in the EA Product 4 information and the SFRA mapping. The Product 4 information confirms that the site sits within an area that has been modelled and provides information for the 1% AEP + 35% Climate Change is 57.29mAOD and the 0.1% AEP predicted flood level is 57.31mAOD. The existing external ground levels surrounding the existing building are at about 57.41mAOD at the proposed site. Finished floor levels in any case should be a minimum 150mm above external levels, therefore It is proposed that the internal levels of the new building are set at 57.56mAOD.

Surface Water Drainage systems will be designed to cater for and up to the 1 in 100 year return period, plus 40% climate change.

Drainage shall also be designed with the appropriate factor of safety, in accordance with the tables set out in CIRIA Publication 753 “The SUDS Manual”.

Drainage Strategy 40 St. Thomas Street

There are no expected issues of surface water or foul water drainage flooding at the application site. Although there are public surface and foul water sewers in the vicinity of the site, the existing and proposed development are well above the level of the highway, therefore any potential surcharge incidents in the public sewer network would not affect the new building.

SuDS Maintenance

The building owner will be responsible for maintaining the private SuDs features and this may be undertaken by a maintenance contractor. An instruction manual detailing the frequency and type of maintenance required for all the SuDs features employed will be provided to the owner prior to occupancy.

Drainage Strategy 40 St. Thomas Street

Appendices

• Site Location Plans • Existing Site Plan • Geology Map • Borehole Records • Flood Maps • Public Sewer Records • Development Site Layout Proposal • Landscape Proposals • Drainage Strategy Drawing • Calculations

Location Plan

0 0.1 0.2

Projection = OSGB36

xmin = 447300 0 0.1 5 0.3 ymin = 204500

xmax = 454000 km ymax = 207900 Map produced by MAGIC on 3 March, 2021. Copyright resides with the data suppliers and the map must not be reproduced without their permission. Some information in MAGIC is a snapshot of the information (c) Crown Copyright and database rights 2021. Ordnance Survey 100022861. that is being maintained or continually updated by the originating organisation. Please refer to the metadata for details as information may be illustrative or representative rather than definitive at this stage. ST THOMAS' ST

Site Location Plan 1:1250

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0 12.5 25 37.5 50 62.5

NOTES Revision PROJECT NAME 40 St Thomas St

PROJECT CODE 40STS

Address TITLE It shall be read in conjunction with all other Site Location Plan associated project information including models, 40 St Thomas' Street speciﬁcations, schedules and related consultants documents. Do not scale from documents. All dimensions to be checked on site. Immediately Oxford report any discrepancies, errors or omissions on this Date 04/01/2020 document to the Originator. If in doubt ASK. OX1 1JL Drawing No P-01

GSPublisherVersion 1392.63.64.100 SCALE BAR

0 1 2 3 4 5

It shall be read in conjunction with all other associated project information including models, speciﬁcations, schedules and related consultants documents. Do not scale from documents. All T1 dimensions to be checked on site. Immediately report any discrepancies, errors or omissions on this document to the Originator. If in doubt ASK.

T2 NORTH

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H NOTES

T4 T4 b

u ADDRESS s 40 St Thomas' Street h Oxford

T4 R OX1 1JL

PROJECT NAME B-002 w CANVAS OVERHEAD SHELTER 40 St Thomas St Commercial Development PROJECT CODE 40STS B-001 T3 EXISTING BUILDING TITLE T2 Existing plan

Existing Site

T3 T7

Revision

St Thomas' street

Date 04/01/2020 Scale 1:200 @ A3

Drawing No

0. Existing Site 1:200 P-03

GSPublisherVersion 1392.63.63.100

Map Key

Bedrock geology 1:50,000 scale

KINGSTON FORMATION - SANDSTONE

LOWER GREENSAND GROUP - SANDSTONE

KIMMERIDGE CLAY FORMATION - SILTSTONE AND SANDSTONE

WHITCHURCH SAND FORMATION - SANDSTONE

STANFORD FORMATION - LIMESTONE

WHEATLEY LIMESTONE MEMBER - LIMESTONE

KELLAWAYS SAND MEMBER - SANDSTONE AND SILTSTONE, INTERBEDDED

ARNGROVE SPICULITE MEMBER - SANDSTONE

WEST WALTON FORMATION - MUDSTONE

AMPTHILL CLAY FORMATION - MUDSTONE

PORTLAND GROUP - LIMESTONE AND CALCAREOUS SANDSTONE

BECKLEY SAND MEMBER - SANDSTONE

KIMMERIDGE CLAY FORMATION - MUDSTONE

WEYMOUTH MEMBER - MUDSTONE

STEWARTBY MEMBER - MUDSTONE

OXFORD CLAY FORMATION AND WEST WALTON FORMATION (UNDIFFERENTIATED) - MUDSTONE

Superficial deposits 1:50,000 scale

NORTHERN DRIFT FORMATION - DIAMICTON

ALLUVIUM - CLAY, SILT, SAND AND GRAVEL

HEAD - CLAY, SILT, SAND AND GRAVEL

NORTHMOOR SAND AND GRAVEL MEMBER - SAND AND GRAVEL

SUMMERTOWN-RADLEY SAND AND GRAVEL MEMBER - SAND AND GRAVEL

PEAT - PEAT

WOLVERCOTE SAND AND GRAVEL MEMBER - SAND AND GRAVEL

HANBOROUGH GRAVEL MEMBER - SAND AND GRAVEL

Flood map for planning Your reference St Thomas Str Location (easting/northing) 450648/206168 Scale 1:2500 Created 11 Jan 2021 19:44

Selected point

Flood zone 3

Flood zone 3: areas benefitting from flood defences

Flood zone 2

Flood zone 1

Flood defence

Main river

Flood storage area

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Page 2 of 2

Asset Location Search Sewer Map - ALS/ALS Standard/2018_3842654 6210 6206 621B 621K 7 721F721A

621J Shelter Royal621F 15 1 Oxford 13 12 1721E 16 14 Hotel 721D 6205 621H621G 7201 7204 7207 7208 7202 420 SheltersFrideswide Square 6202 57.6m 750 x 6201 39Canta 600 x 400 225 7205 36 Shelters 7206 Hous 225 6203 6204 LB 621ITCBs 621E621D King Charles House 22 24 27

7203

The Lamp Building

Vicarage 611F 10 to 12 611A611B 611E PH 14 to 19 12 to 18 611D 611I611H The Old Bakery

Castle Mews 611G 54 to 57 20 to 28 1 to 11 19 to 28 omas'sChurch 1 to 9 C of E) PH 40 525 7104 6103 7103 6102 6101 22 20 28 27 Corner House 710

710 7105 7106 7107 Christ Church 56.7m Old Buildings

Rowland Hill Court 6009

The width of the displayed area is 200 m and the centre of the map is located at OS coordinates 450693,206194 The position of the apparatus shown on this plan is given without obligation and warranty, and the accuracy cannot be guaranteed. Service pipes are not shown but their presence should be anticipated. No liability of any kind whatsoever is accepted by Thames Water for any error or omission. The actual position of mains and services must be verified and established on site before any works are undertaken. Based on the Ordnance Survey Map with the Sanction of the controller of H.M. Stationery Office, License no. 100019345 Crown Copyright Reserved.

Thames Water Utilities Ltd, Property Searches, PO Box 3189, Slough SL1 4W, DX 151280 Slough 13 Page 6 of 12 T 0845 070 9148 E [email protected] I www.thameswater-propertysearches.co.uk

NB. Levels quoted in metres Ordnance Newlyn Datum. The value -9999.00 indicates that no survey information is available

Manhole Reference Manhole Cover Level Manhole Invert Level 721D n/a n/a 721E n/a n/a 721F n/a n/a 721A n/a n/a 721B n/a n/a 6202 57.32 n/a 7206 57.26 56.3 7205 57.27 56.3 7208 57.29 n/a 7202 57.43 53.98 7204 57.34 n/a 7207 57.4 n/a 7201 57.45 54 621H n/a n/a 621G n/a n/a 621F n/a n/a 621J n/a n/a 6206 57.32 55.53 621K n/a n/a 621B n/a n/a 6009 n/a n/a 7105 57.07 55.73 6101 57.06 55.43 6102 57 54.68 6103 57.02 55.38 7103 56.82 54.98 7104 56.88 55.3 611G n/a n/a 611H n/a n/a 611I n/a n/a 611D n/a n/a 611E n/a n/a 611B n/a n/a 611A n/a n/a 611F n/a n/a 7203 57.02 55.52 621E n/a n/a 621D n/a n/a 621I n/a n/a 6204 57.06 55.92 6203 57.36 n/a 6201 57.38 54.08 6210 n/a n/a 6205 57.36 n/a 7107 56.82 55.27 7106 56.86 55.28 7108 56.8 55.25

The position of the apparatus shown on this plan is given without obligation and warranty, and the accuracy cannot be guaranteed. Service pipes are not shown but their presence should be anticipated. No liability of any kind whatsoever is accepted by Thames Water for any error or omission. The actual position of mains and services must be verified and established on site before any works are undertaken.

Thames Water Utilities Ltd, Property Searches, PO Box 3189, Slough SL1 4W, DX 151280 Slough 13 Page 7 of 12 T 0845 070 9148 E [email protected] I www.thameswater-propertysearches.co.uk

Page of 12 8 M www.thameswater-propertysearches.co.uk I , Property, Box4W, Searches, 3189,SloughPODX SL1 Slough 151280 13 [email protected] E 0845070 9148 T ThamesUtilities Water Ltd

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FF terrace 2 FF terrace 1 office 2's terrace 2 office 2's terrace 1

T4 T4 T4 T4 It shall be read in conjunction with all other FF.005 associated project information including models, Office 2 speciﬁcations, schedules and related consultants 3 documents. Do not scale from documents. All e 3 c

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E E

- - 0 FF.004 FF.008 0 2 2 FF.006 Lobby Toilet GF.003 Kitchen Lobby

F DW

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T2 T2 FF.003 Office 1 e

ADDRESS T7 T7 40 St Thomas' Street Oxford

0. GF-Ground Floor 1:100 1. 01-First Floor 1:100 OX1 1JL

PROJECT NAME E-03 E-03 40 St Thomas St Commercial SF terrace 3 SF terrace 2 Development office 4's terrace 2 office 4's terrace 1

PROJECT CODE T4 T4 T4 T4 SF.005 Office 4 40STS 3

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SF.002 SF.007 Lobby Toilet T3 T3

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T2 NORTH

T3 PL-003 SCALE BAR Shrub 0 2 4 6 8

Shared Garden H NOTES with controlled access site boundary o Legend Oce 4 Oce 4 Terrace l Permeable block paving Terrace l Grass/Lawn Areas y Gravel T4 T4 b

u ADDRESS s 40 St Thomas' Street h Oxford

T4 Flat Roof L OX1 1JL

e o

Shared Terrace t o PROJECT NAME n w

EXF-002 e

a Bench v 40 St Thomas St e

e red bike shed n Cove Commercial t Development PROJECT CODE 40STS T3

TITLE T2

r Oce 3 t

n Landscaping plan

E Lawn PL-002 Terrace Shrub Proposed Site PL-001 Tree

Permeable Paving EXF-001 T3 Covered BinT S7torage

EXF-003 Revision Bollard St Thomas' street

Date 04/01/2020 Scale 1:200 @ A3

Drawing No

0. Proposed Site 1:200 P-05 A

GSPublisherVersion 1392.63.64.100 CCTV

h 22m Sycamore T/W KEY: 58.86 SW 57.23 57.24 Wooden T/W 58.80 Shelter Application Site Boundary h 8m Shed Neighbouring Properties

57.24 Public Foul Water Sewer

57.38 Flats and Apartments 57.33 57.29 Public Surface Water Sewer CCTV Plastic Matting Highway Authority Drain

57.28

57.29

PL 70.77 Surface Water Drain

57.38 57.28 Foul Water Drain Sand Surface Water IC Pit h 22m Playground

57.29 BW Neighbouring Garden Sycamore CPS Foul Water IC

T/F 57.23 Foul Water IC with Backdrop

57.28 (Private Property) 59.12 BD PL 70.81 Surface Catch Pit/Manhole

Plastic Matting Foul Water Manhole 57.30 57.25 57.32 57.27 57.200 Spot Levels

C/B 1800h E-03 T/W T/W 57.32 57.30 58.82 58.82 Catchment Area 57.25 RE S1 RE 56.910 Playground CL 57.410 314m² + 57.41 IL 56.810 57.29 + 57.41 58.80 57.24 PL 70.81 57.30 Soft Landscaped Area 57.23 CPS BW Shed 118m² Z T/W 57.26 RE 57.30 57.28 Ø100 + 57.4158.82 57.27 IC FB CL 57.30 Geocellular Tank 57.26 CAB FB TAP EL IL 56.80 Foul 57.27 G 63.59 VP 57.29 CSC 57.28 T/F Vegetation Canopy 57.28 57.29

62.47 57.31 57.31 Neighbouring Properties CPS h 6m C/L 800h Co Permeable Paving

THL 57.24 Sycamore 56.98 Stone Flats and Apartments 56.86 T4 57.28 T4 57.23 Fan 57.47 h 22m 56.98 CPS

Sycamore Fan Asphalt Compost Heaps G 68.17 PL T/W 57.34 57.27 58.55

DP Fan

57.25

GS 57.26 DP GF.004 T/W Grave Fan 57.31 G Meeting room 58.82 57.33Cables 57.30 GS + 57.41 Mesh Gate Grave Mesh Gate 56.67 T4 h 4m FFL: 57.560 T/W CCTV 56.67 57.39 58.89 E-02 68.10

BW Bike Rack Bike CL 57.395T/W PL 68.10 56.96 GF.003 RE T/W

IL 56.08558.90 58.91 62.69 PL Ø100 57.40 BW Lobby Ø100 57.31 Ø100 57.27 RE 56.910 57.29 10 IC 11 12 13

14 15 16 17

Ø100 CL 57.26 57.40 IL 56.66 57.27 DOWN Foul T/F CHM E-04 C/B 65.05 66.48 57.32 57.30

Compost Heaps PL 62.69 57.36 GF.002 + 57.39 57.26

F1 57.31 56.95 EL 61.79 CHM CL 57.403 UP 57.32 CHM 56.96 Stairwell Custom Text 57.25 66.48 IL 56.085 57.29 66.49

8 7 6 5

4 56.72 3

2 Grass Asphalt 1 GS GS F7 Grave Grave CL 57.420 GF.005 GF.006 IL 56.000 57.30 Neighbouring Properties

Toilet Playground RL 64.72

40 St Thomas Street Thomas St 40 RL 64.76 SW Covered With Vegetation With Covered SW Toilet Neighbouring Properties

57.37 65.37 RL

F2 Nursery Day Thomas St.

57.48

57.31 T3 CL 57.400 57.31 h 6m

56.81 800h Barrier Metal IL 56.023 Equipment Play Children's 57.31 57.05 GF.001 56.76 RL 64.80

BW Coffee area and reception 57.33

EL RL 65.04 57.32 61.46 EL 57.31 EL EL 61.43 T2 61.41 61.40 h 6m EL G 61.54 Hawthorn + 57.56 Canvas Overhead Shelter Vent Pipe

DP Entrance DP GS F G S2 EL Grave 57.32 Neighbouring Garden 57.23 62.48 CL 57.390 F Off-Line Geocellular

F FOR

56.89 57.42 IL 56.810 Rubber Landing Surface Tank 4m x 2m x0.8m

DW (Private Property) 56.80 Grave IL OUT 56.150 SLOPE 1/200 GS 57.41 57.30 57.28 PLANNING IC Silted+ Up 57.39 THL 57.31 57.49 EL IL 56.500 IC Impermeable Area 60.82 Block Paving

59.26 63.73 Ø100 56.99 CL 57.33

CL 57.03 Door 57.50 hatched pink JB Co

Metal Steps 59.08 57.11 57.00 Foul EL 57.33 Mat 57.30 57.40 63.72 Fire Escape

57.03 F3 57.43 Up To First Floor S4

BW Public Surface Water Sewer CL 57.385 60.80 CL57.21 57.280 Hydrobrake vortex h 14m SC 57.38 +57.31 57.34 Sycamore Manhole 6103 IL 55.941 57.40 57.38 IL 56.100 flow control on outlet 57.11 B 57.37 IL 56.500 CL57.02 + 57.37 SC BASE 55.600 to restrict flow Church Yard 57.36 F8 F9 IL55.38 (525Ø) from records 57.38 CL 57.200 Asphalt 57.02 Vegetation With Covered SW Asphalt Playground CL 57.13 IL 55.792 57.45 IL 56.100 IL 55.700 TBC Locked I/R Gates SW Covered With Vegetation S3 F5 I/R F4 BW Locked I/R Gate SW CL 57.365 CL 57.355 SP 56.96

57.02 Grass 57.41 57.26 56.91 56.92 CL 57.365CPS Shed IL 56.760 IL 55.837 57.11 57.01 56.99 IL 55.898 57.44 Wooden Gates + 57.11 I/R 56.88 57.40 57.42 56.98 Tac T7 57.07 BW SW 56.99 57.58 57.39 57.00 T/W Asphalt Hollybush Row BW SC 56.93 h 24m 58.45 SW RS BT 56.85 SW Covered With Vegetation 57.06 + 57.06 56.98 SC Fir Asphalt 56.99 56.97 56.97 56.82 56.82 SC RS GV LP 57.09 A GS h 4m Catch Pit 57.00 G Silt Trap 56.88 Asphalt 56.95 57.00 57.07 Flow Control 56.90 57.02 57.02 56.88 IC 57.11 56.92 56.91 CL 56.89

I/R 56.94 UTL IC on Road 57.02 New connection to PO T/W 57.05 57.85 highway drain 57.12 T/F Existing connection to be 57.08 59.02 GV SW 57.07 inspected before reuse.

57.15 57.00 57.07 PO 56.96 Grass 57.09 O/H Telephone Cables Assumed Highway Drain St Thomas Street 57.02 Concrete Path 57.00 Asphalt 57.07 Public Foul Sewer Asphalt 57.04 57.15 I/R Gate FH 57.13 Manhole 6101 57.06 57.12 SC CL57.06 57.09 57.07 AHL 56.98 56.96 IL55.43 from records 57.03

I/R 57.17 T/W 57.05 57.85 G IC OFFICE DEVELOPMENT 57.07 CL 56.94 G 56.82 Grass 56.97 UTL IC on Road 56.80 56.80 56.84

SW EL 56.91 56.80 40 ST. THOMAS STREET, 62.61 56.83 56.94 56.94 Tac 56.85 Asphalt 56.86 56.92 56.89 BT 56.91 56.91 56.96 OXFORD 57.09 EL IC 56.88 56.95

62.60 57.07 CL 57.00 Asphalt Footpath EL DP UTL IC on Road 56.95 56.98 BT 64.68 EL 57.05 56.95 EL 64.69 Asphalt Footpath LP EL EL 63.09 Brick Paving EL 57.06 SP 57.06 56.99 64.72 EL EL 63.12 56.97 64.74 EL EL 65.42 56.85 56.97 57.00 65.41 GV 56.97 57.03 65.42 DRAINAGE STRATEGY 65.40 57.07 EL 56.96 Bay 57.06 BT EL T/W 57.07 Bay EL Asphalt 65.42 I/R Gate 56.98 EL T/W 57.05 65.38 DP SC 57.01 59.47 59.47 57.09 58.01 59.06 EL Window Stone Paving T/W 57.08 EL 65.40 Window 57.06 BW 58.05 57.09 57.08 Asphalt DP Overhead BW I/R 65.46 Overhead 57.08 DP I/R BW Neighbouring Properties I/R PL 66.19 RL 65.98 Gate RL 65.96 PL 63.51 Neighbouring Properties RL 65.93 Outbuilding PL 66.10 5278 RL 67.01 PL 67.58 RL 60.23 Neighbouring Properties 0m 1m 5m RL 67.08 T/W 18/03/2021 67.49 1000 Asphalt Scale: 1:100 @ A1 RL 68.28 1:100 @ A1 EL RL 68.30 63.09 Roads & Sewers For Planning File: St Thomas St-Hydrobrake.pfd Page 1 & Design Network: Storm Network St Thomas Street Tony Lee Oxford 17/3/2021 Tank Opon

Design Sengs

Rainfall Methodology FSR Maximum Time of Concentraon (mins) 30.00 Return Period (years) 2 Maximum Rainfall (mm/hr) 50.0 Addional Flow (%) 0 Minimum Velocity (m/s) 1.00 FSR Region England and Wales Connecon Type Level Sots M5-60 (mm) 20.000 Minimum Backdrop Height (m) 0.200 Rao-R 0.400 Preferred Cover Depth (m) 1.200 CV 0.750 Include Intermediate Ground ✓ Time of Entry (mins) 5.00 Enforce best pracce design rules ✓

Nodes

Name Area T of E Cover Diameter Easng Northing Depth (ha) (mins) Level (mm) (m) (m) (m) (m) S1 0.012 5.00 57.410 450 450651.473 206180.203 0.600 S2 0.013 5.00 57.390 450 450643.205 206160.469 0.580 S3 0.002 5.00 57.365 450 450645.716 206157.604 0.605 S4 0.005 5.00 57.280 1200 450654.449 206158.252 1.880 TANK 5.00 57.350 450655.300 206159.427 1.200 OUTFALL 57.130 450 450656.376 206156.812 1.430

Links

Name US DS Length ks (mm) / US IL DS IL Fall Slope Dia T of C Rain Node Node (m) n (m) (m) (m) (1:X) (mm) (mins) (mm/hr) 1.000 S1 S4 22.152 0.600 56.810 56.500 0.310 71.5 100 5.41 50.0 2.000 S2 S3 3.810 0.600 56.810 56.760 0.050 76.2 100 5.07 50.0 2.001 S3 S4 8.757 0.600 56.760 56.500 0.260 33.7 100 5.18 50.0 3.000 TANK S4 1.451 0.600 56.150 56.100 0.050 29.0 100 5.02 50.0 1.004 S4 OUTFALL 2.406 0.600 55.900 55.700 0.200 12.0 100 5.42 50.0

Name Vel Cap Flow US DS Σ Area Σ Add Pro Pro (m/s) (l/s) (l/s) Depth Depth (ha) Inow Depth Velocity (m) (m) (l/s) (mm) (m/s) 1.000 0.912 7.2 1.6 0.500 0.680 0.012 0.0 32 0.737 2.000 0.882 6.9 1.8 0.480 0.505 0.013 0.0 35 0.741 2.001 1.333 10.5 2.0 0.505 0.680 0.015 0.0 30 1.036 3.000 1.438 11.3 0.0 1.100 1.080 0.000 0.0 0 0.000 1.004 2.240 17.6 4.3 1.280 1.330 0.032 0.0 34 1.861

Pipeline Schedule

Link Length Slope Dia Link US CL US IL US Depth DS CL DS IL DS Depth (m) (1:X) (mm) Type (m) (m) (m) (m) (m) (m) 1.000 22.152 71.5 100 Circular_Default Sewer Type 57.410 56.810 0.500 57.280 56.500 0.680 2.000 3.810 76.2 100 Circular_Default Sewer Type 57.390 56.810 0.480 57.365 56.760 0.505 2.001 8.757 33.7 100 Circular_Default Sewer Type 57.365 56.760 0.505 57.280 56.500 0.680 3.000 1.451 29.0 100 Circular_Default Sewer Type 57.350 56.150 1.100 57.280 56.100 1.080

Link US Dia Node MH DS Dia Node MH Node (mm) Type Type Node (mm) Type Type 1.000 S1 450 Manhole IC-450 DIA S4 1200 Manhole Adoptable 2.000 S2 450 Manhole IC-450 DIA S3 450 Manhole IC-450 DIA 2.001 S3 450 Manhole IC-450 DIA S4 1200 Manhole Adoptable 3.000 TANK Juncon S4 1200 Manhole Adoptable

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Pipeline Schedule

Link Length Slope Dia Link US CL US IL US Depth DS CL DS IL DS Depth (m) (1:X) (mm) Type (m) (m) (m) (m) (m) (m) 1.004 2.406 12.0 100 Circular_Default Sewer Type 57.280 55.900 1.280 57.130 55.700 1.330

Link US Dia Node MH DS Dia Node MH Node (mm) Type Type Node (mm) Type Type 1.004 S4 1200 Manhole Adoptable OUTFALL 450 Manhole IC-450 DIA

Manhole Schedule

Node Easng Northing CL Depth Dia Connecons Link IL Dia (m) (m) (m) (m) (mm) (m) (mm) S1 450651.473 206180.203 57.410 0.600 450

0 0 1.000 56.810 100 S2 450643.205 206160.469 57.390 0.580 450

0 0 2.000 56.810 100

S3 450645.716 206157.604 57.365 0.605 450 1 1 2.000 56.760 100

0 2.001 56.760 100 3 S4 450654.449 206158.252 57.280 1.880 1200 1 1 3.000 56.100 100 2 2.001 56.500 100 2 3 1.000 56.500 100 0 0 1.004 55.900 100 TANK 450655.300 206159.427 57.350 1.200

0 0 3.000 56.150 100 OUTFALL 450656.376 206156.812 57.130 1.430 450 1 1.004 55.700 100 1

Simulaon Sengs

Rainfall Methodology FSR Analysis Speed Normal FSR Region England and Wales Skip Steady State x M5-60 (mm) 20.000 Drain Down Time (mins) 240 Rao-R 0.400 Addional Storage (m³/ha) 20.0 Summer CV 0.750 Check Discharge Rate(s) x Winter CV 0.840 Check Discharge Volume x

Storm Duraons 15 30 60 120 180 240 360 480 600 720 960 1440

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Return Period Climate Change Addional Area Addional Flow (years) (CC %) (A %) (Q %) 1 0 0 0 30 0 0 0 100 0 0 0 100 40 0 0

Node S4 Online Hydro-Brake® Control

Flap Valve x Objecve (HE) Minimise upstream storage Replaces Downstream Link ✓ Sump Available ✓ Invert Level (m) 55.900 Product Number CTL-SHE-0066-2000-1050-2000 Design Depth (m) 1.050 Min Outlet Diameter (m) 0.100 Design Flow (l/s) 2.0 Min Node Diameter (mm) 1200

Node TANK Depth/Area Storage Structure

Base Inf Coecient (m/hr) 0.00000 Safety Factor 2.0 Invert Level (m) 56.150 Side Inf Coecient (m/hr) 0.00000 Porosity 0.95 Time to half empty (mins) 65

Depth Area Inf Area Depth Area Inf Area Depth Area Inf Area (m) (m²) (m²) (m) (m²) (m²) (m) (m²) (m²) 0.000 8.0 0.0 0.800 8.0 0.0 0.801 0.0 0.0

Flow+ v10.1 Copyright © 1988-2021 Causeway Technologies Ltd Roads & Sewers For Planning File: St Thomas St-Hydrobrake.pfd Page 4 & Design Network: Storm Network St Thomas Street Tony Lee Oxford 17/3/2021 Tank Opon

Results for 1 year Crical Storm Duraon. Lowest mass balance: 97.96%

Node Event US Peak Level Depth Inow Node Flood Status Node (mins) (m) (m) (l/s) Vol (m³) (m³) 15 minute winter S1 10 56.843 0.033 1.7 0.0184 0.0000 OK 15 minute winter S2 10 56.847 0.037 1.8 0.0225 0.0000 OK 15 minute winter S3 10 56.791 0.031 2.1 0.0070 0.0000 OK 15 minute winter S4 14 56.209 0.309 4.4 0.3714 0.0000 SURCHARGED 15 minute winter TANK 14 56.209 0.059 2.7 0.4471 0.0000 OK 15 minute summer OUTFALL 1 55.700 0.000 1.9 0.0000 0.0000 OK

Link Event US Link DS Oulow Velocity Flow/Cap Link Discharge (Upstream Depth) Node Node (l/s) (m/s) Vol (m³) Vol (m³) 15 minute winter S1 1.000 S4 1.6 0.736 0.229 0.0493 15 minute winter S2 2.000 S3 1.8 0.755 0.256 0.0090 15 minute winter S3 2.001 S4 2.0 1.014 0.195 0.0177 15 minute winter S4 Hydro-Brake® OUTFALL 1.9 2.1 15 minute winter TANK 3.000 S4 2.9 -0.808 0.254 0.0092

Flow+ v10.1 Copyright © 1988-2021 Causeway Technologies Ltd Roads & Sewers For Planning File: St Thomas St-Hydrobrake.pfd Page 5 & Design Network: Storm Network St Thomas Street Tony Lee Oxford 17/3/2021 Tank Opon

Results for 30 year Crical Storm Duraon. Lowest mass balance: 97.96%

Node Event US Peak Level Depth Inow Node Flood Status Node (mins) (m) (m) (l/s) Vol (m³) (m³) 15 minute winter S1 10 56.865 0.055 4.2 0.0310 0.0000 OK 15 minute winter S2 10 56.874 0.064 4.5 0.0391 0.0000 OK 15 minute winter S3 10 56.812 0.052 5.1 0.0117 0.0000 OK 30 minute winter S4 29 56.551 0.651 8.5 0.7835 0.0000 SURCHARGED 30 minute winter TANK 29 56.551 0.401 5.7 3.0501 0.0000 SURCHARGED 15 minute summer OUTFALL 1 55.700 0.000 1.9 0.0000 0.0000 OK

Link Event US Link DS Oulow Velocity Flow/Cap Link Discharge (Upstream Depth) Node Node (l/s) (m/s) Vol (m³) Vol (m³) 15 minute winter S1 1.000 S4 4.0 0.928 0.565 0.0968 15 minute winter S2 2.000 S3 4.4 0.939 0.641 0.0180 15 minute winter S3 2.001 S4 5.1 1.276 0.485 0.0348 30 minute winter S4 Hydro-Brake® OUTFALL 1.9 6.6 30 minute winter TANK 3.000 S4 -5.7 -0.788 -0.508 0.0114

Flow+ v10.1 Copyright © 1988-2021 Causeway Technologies Ltd Roads & Sewers For Planning File: St Thomas St-Hydrobrake.pfd Page 6 & Design Network: Storm Network St Thomas Street Tony Lee Oxford 17/3/2021 Tank Opon

Results for 100 year Crical Storm Duraon. Lowest mass balance: 97.96%

Node Event US Peak Level Depth Inow Node Flood Status Node (mins) (m) (m) (l/s) Vol (m³) (m³) 15 minute winter S1 10 56.876 0.066 5.4 0.0368 0.0000 OK 15 minute winter S2 10 56.887 0.077 5.8 0.0470 0.0000 OK 15 minute winter S3 10 56.822 0.062 6.6 0.0139 0.0000 OK 30 minute winter S4 30 56.740 0.840 11.1 1.0109 0.0000 SURCHARGED 30 minute winter TANK 30 56.740 0.590 8.2 4.4868 0.0000 SURCHARGED 15 minute summer OUTFALL 1 55.700 0.000 1.9 0.0000 0.0000 OK

Link Event US Link DS Oulow Velocity Flow/Cap Link Discharge (Upstream Depth) Node Node (l/s) (m/s) Vol (m³) Vol (m³) 15 minute winter S1 1.000 S4 5.2 0.982 0.732 0.1282 15 minute winter S2 2.000 S3 5.7 0.988 0.828 0.0220 15 minute winter S3 2.001 S4 6.5 1.349 0.625 0.0490 30 minute winter S4 Hydro-Brake® OUTFALL 1.9 8.7 30 minute winter TANK 3.000 S4 -8.2 -1.044 -0.723 0.0114

Flow+ v10.1 Copyright © 1988-2021 Causeway Technologies Ltd Roads & Sewers For Planning File: St Thomas St-Hydrobrake.pfd Page 7 & Design Network: Storm Network St Thomas Street Tony Lee Oxford 17/3/2021 Tank Opon

Results for 100 year +40% CC Crical Storm Duraon. Lowest mass balance: 97.96%

Node Event US Peak Level Depth Inow Node Flood Status Node (mins) (m) (m) (l/s) Vol (m³) (m³) 60 minute winter S1 49 57.118 0.308 3.9 0.1722 0.0000 FLOOD RISK 60 minute winter S2 50 57.118 0.308 4.2 0.1870 0.0000 FLOOD RISK 60 minute winter S3 50 57.117 0.357 4.8 0.0803 0.0000 FLOOD RISK 60 minute winter S4 50 57.114 1.214 10.3 1.4599 0.0000 FLOOD RISK 60 minute winter TANK 50 57.114 0.964 6.9 6.0838 0.0000 FLOOD RISK 15 minute summer OUTFALL 1 55.700 0.000 1.9 0.0000 0.0000 OK

Link Event US Link DS Oulow Velocity Flow/Cap Link Discharge (Upstream Depth) Node Node (l/s) (m/s) Vol (m³) Vol (m³) 60 minute winter S1 1.000 S4 3.9 0.902 0.545 0.1733 60 minute winter S2 2.000 S3 4.2 0.960 0.606 0.0298 60 minute winter S3 2.001 S4 4.8 1.242 0.458 0.0685 60 minute winter S4 Hydro-Brake® OUTFALL 2.1 15.3 60 minute winter TANK 3.000 S4 -6.9 -0.884 -0.613 0.0114