Drainage Condition Discharge

Drainage Condition Discharge 18/01756/OUT

Bourton, Marshmouth Lane

28 June 2021

Prepared for:

Orwell Real Estate

Pinnacle Consulting Engineers Limited Draiange Discharge Disharge BOURTON, Marshmouth Lane Version No. 1.1 1 C210608-PIN-XX-XX-RP-C-01

CONTACT DETAILS

Name Position Email Telephone Mobile

Richard Pearson Civil Engineer [email protected] 01707 527638 -

Jawsy Jabbar Associate [email protected] 01707 527636 07920 721332

Elizabeth Orchard

Associate Director

[email protected] - 07471 456037

APPROVALS Name Position Date

Prepared by Richard Pearson Civil Engineer 28.06.2021

Reviewed by Jawsy Jabbar Associate 28.06.2021

Approved by Elizabeth Orchard Associate Director 28.06.2021

VERSIONS

This document has been prepared by Pinnacle Consulting Engineers Ltd. for the titled project and should not be relied upon or used for any other project. Pinnacle Consulting Engineers Ltd accepts no responsibility or liability for the consequences of this document being used for any purpose other than the purpose for which it was commissioned. Any person using or relying on the document for such other purpose agrees, and will by such use or reliance be taken to confirm his agreement to indemnify Pinnacle Consulting Engineers Ltd for all loss or resultant damage. Pinnacle Consulting Engineers Ltd accepts no responsibility or liability for this document to any party other than the person by whom it was commissioned.

Number By Date Context

1.0 Richard Pearson 28.06.2021 For Client Comment

1.1 Richard Pearson 09.07.2021 Updated following comments


CONTENT

1 INTRODUCTION ............................................................................................................................3

2 DETAILED DRAINAGE SCHEME .................................................................................................4

3 MAINTENANCE REQUIREMENTS ...............................................................................................5

APPENDIX A – DRAINAGE SCHEME DRAWING ..................................................................................0

APPENDIX B – BRE365 INFILTRATION TEST.......................................................................................1

APPENDIX C – MICRODRAINAGE CALCULATIONS ............................................................................2


1 INTRODUCTION Pinnacle Consulting Engineers Ltd have been commissioned by Orwell Real Estate to carry out a full surface water drainage scheme to discharge planning condition 8 for application Ref:18/01756/OUT.

The condition as noted in the decision letter dated for decision on 13th March 2019 is:

“8. Prior to the commencement of development, a full surface water drainage scheme shall be submitted to and approved in writing by the Local Planning Authority. The scheme shall include details of the size, position and construction of the drainage scheme. The details shall include a management plan setting out the maintenance of the drainage asset. The development shall be carried out in accordance with the approved details prior to the first occupation of the development hereby approved and shall be maintained in accordance with the management plan thereafter. Reason: To ensure the proper provision for surface water drainage and/ or to ensure flooding is not exacerbated in the locality (The Cotswold Strategic Flood Risk Assessment, National Planning Policy Framework and Planning Practice Guidance).”

This document will provide information of the detailed draiange model undertaken for this site along with a maintenance plan in accordance with the “The SuDS manual”.


2 DETAILED DRAINAGE SCHEME Since the issuing of the drainage strategy report (by RPS) in May 2018, BRE 365 soakaway testing has been undertaken at two locations of the site. Both soakage tests were failed due to the poor infiltration media. See Appenix B for the test locations and the results. Based on the test results, it is evident that the infiltaration discharge is not viable in this site location.

According to the Building Regulations discharge hierarchy, the next method of discharge would be to connect the surface water network to the existing watercourse, the River Windrush.

A drainage system has been proposed, designed and modelled using Microdrainage software and the results can be found in Appendix C. The drainage model used an outfall level above a 1 in 100 year flood level of 127.400m into the river Windrush adjacent to the site.

Greenfield discharge rate for the site has been calculated as 0.2l/s. Due to the risk of blockage and maintenance require for a Hydro-Brake flow control device a minimum flow rate of 2l/s has been selected as the discharge rate into the river Windrush. Attenuation requirement based on this discharge rate for the site is 8m3 (2No. 4x3.5x0.3m) which will be provided in underground cellular attenuation tanks.

The access roads will be of permeable paving construction and will discharge to the ditch adjacent Marshmouth Lane, as discharge to the river Windrush will not be possible under gravity due the flat nature of the site and the water level of the river Windrush. The permeable paving will provide two levels of treatment for the access road runoff before discharging into the adjacent ditch.

The full drainage calculations can be found in Appendix C.


3 MAINTENANCE REQUIREMENTS It is anticipated that a private management company will be employed to maintain the completed drainage network for the development incorporating the following activities and frequency for each SUDS component.

3.1.1 Gullies/Channels/Pipes/Manholes

All components are to be periodically cleaned of foreign particles and silt accumulation, on a quarterly basis. Components located in unadopted areas will be maintained by the landowner. Those located in adopted areas will be maintained by the adopting authority.

3.1.2 Cellular Attenuation Tank

The proposed attenuation tank includes a perforated/ slotted distribution pipe surrounded by granular material providing filtration and treatment for surface water flows. This in conjunction with the proposed catch pit manhole (silt trap) is considered appropriate for the scale and nature of the development.

3.1.3 Pervious pavements

Many of the specific maintenance activities for pervious pavements can be undertaken as part of a general site cleaning contract. Guidance on the type of operational and maintenance requirements is detailed below in table 20.15 from the CIRIA SuDS manual.


3.1.4 Proprietary Systems

Proprietary systems will require routine maintenance by the owner to ensure continuing operation to design performance standards. A typical maintenance schedule is detailed below in table 14.2 from the CIRIA SuDS manual.

Pinnacle Consulting Engineers Limited Drainage Strategy Report ENFIELD, Progress Way, Commercial Park Version No. 3.0 C200805-PIN-XX-XX-RP-C-02

Appendix A – Drainage Scheme Drawing

LEGEND

PROPOSED SURFACE WATER SEWER

PROPOSED SURFACE WATER MANHOLE

PROPOSED HYDROBRAKE CHAMBER

PROPOSED SURFACE WATER STORAGE TANK

PROPOSED PERMEABLE PAVING

SITE BOUNDARY

HB

CL 127.80BH

CL 128.01BH

127.64

127.64

127.65

127.

67

127.49

127.62

127.64 127.70

127.

49

127.58

127.63

127.80

127.66

127.64

127.61

127.29

GATE

GATE

GATE

G

INVERT

PIPE

127.63

127.61

127.68

127.67

127.63

127.61127.61

127.55

127.55

127.46

127.49

127.57

127.59

127.57

127.59127.49

127.50

127.47

127.47

127.75

127.71

127.68

127.

57

TMH

TP

TP

127.66

127.67

127.

52

WL 127.34

127.47

127.79

127.81

127.75

127.77

127.7

0

127.

75

127.

66127.68

127.64

127.68

127.57

127.55

127.53

127.45

127.57127.69

127.61

126.

72

126.

65

126.

86

126.

7312

6.74

126.

86

126.

85

126.

86

126.

78

127.

38

127.

41

127.

53

127.

5312

7.52

127.

53

127.

50

127.

41

127.81

127.76

127.70

127.73

127.70

127.69

127.69

127.60

127.48

127.55

127.62

127.54

127.59

127.66

127.55

127.61

127.63127.62

127.54

127.47

127.59

127.86

127.75

127.81

127.93128.02

128.0

5

128.1

5

128.1

8

127.3

2

127.2

4

127.70

127.79

127.75

127.71

127.81

127.68

127.65

127.63

127.54

127.67

127.88

127.77

127.92

127.80

128.10

128.12

128.01

128.07

128.48

128.05

127.91

127.92

127.99

127.78

127.84

127.92

127.82

127.94

128.05

127.98

127.96

128.13

128.09

128.04

128.01

127.

09

127.

05

127.58

127.61

127.61

127.61

127.60

127.83

127.85

127.68

127.70

127.63

127.64

127.66

127.75

RIDGE 134.09

RIDGE 135.50

RIDGE 137.06

RIDGE 136.94

RIDGE 133.30

RIDGE 134.06

RIDGE 136.21

RIDGE 130.52

RIDGE 132.17

EAVES 132.17

EAVES 132.80

EAVES 130.32

EAVES 132.89

EAVES 130.53

127.45

127.35

127.33

127.32

127.29

127.30

FE,CBF 1.6m

FE,CBF 1.

6m

FE,CBF 1.6m

FE,CBF 1.6m

BRICK FOOTINGS

CONCRETE

TARMAC

TARMAC

GRAVELPARKING AREA

127.40

STREAM

STREAM

STREAM

RIVER

FE,P

RF 1

.2m

S3.0

S1.0

S2.0

S2.1

S1.1

S1.2CATCHPIT0.3m SUMP

HYDROBRAKE2.0 L/S DISCHARGEMD-SHE-0073-2000-0580-2000

OUTFALL127.400

S3.1

S3.2CATCHPIT0.3m SUMP

S4.0

S4.1

TANK 2CL 128.100IL 127.4804m3 STORAGE(95% VOID RATIO)4.0m x 3.5m x 0.3m

TANK 1CL 128.100IL 127.5004m3 STORAGE(95% VOID RATIO)4m x 3.5m x 0.3m

HBS1.3

150Ø 1:15

0

150Ø 1:150

150Ø 1:150

150Ø 1:150

150Ø 1:150

150Ø

1:150

150Ø

1:150

150Ø 1

:150

SURFACE WATER MANHOLE SCHEDULE

MANHOLETYPE

Approx.Cover Level

Invert Level ofoutlet pipe

Approx.Depth

Internalmanholesize (mm)

CoverType

ManholeRef

PPIC C250128.100 127.650 0.450S1.0 450Ø

C250S1.1

S1.2

C250S2.0

C250S2.1

C250S3.0

C250S3.2

PPIC

PPIC

PPIC

PPIC

PPIC

PPIC

C250S3.1 PPIC

C250PPIC

C250

128.100 127.560 0.540 450Ø

128.100 127.515 0.585 450Ø

128.100 127.650 0.450

128.100 127.575 0.525

128.100 127.650 0.450

128.100 127.560 0.540

128.100 127.495 0.605

128.100 127.650 0.450

S1.3 PPIC C250128.100 127.430 0.670

Remarks

C250PPIC 128.100 127.575 0.525

1200Ø

450Ø

450Ø

450Ø

450Ø

450Ø

450Ø

450Ø

S4.0

S4.1

Hydrobrake chamber

Catchpit chamber 0.3m sump depth

Catchpit chamber 0.3m sump depth

P01 PRELIMINARY ISSUE TWR 28.06.21JJ

ORWELL REAL ESTATE

N

GENERAL NOTES1. DO NOT SCALE THIS DRAWING. WORK ONLY TO

FIGURED DIMENSIONS.

2. FOR ALL RELEVANT NOTES, REFER TOSTRUCTURAL AND CIVIL ENGINEERINGPERFORMANCE SPECIFICATION.

3. ANY DISCREPANCIES ARE TO BE REPORTED TOPINNACLE CONSULTING ENGINEERS IMMEDIATELY.

4. THIS DRAWING IS TO BE READ IN CONJUNCTIONWITH ALL OTHER RELEVANT ENGINEERS,ARCHITECTS AND SUB-CONTRACTORS DRAWINGSAND DETAILS.

REVISIONDRG NO.

SCALE @ A1 DATE DRAWN BY CHECKED

REV DESCRIPTION BY CHK DATE

COPYRIGHT PINNACLE

PROJECT

DRAWING TITLE

REF:

DRAWING STATUS

CLIENT

ALCHEMY,BESSEMER ROAD,WELWYN GARDEN CITY,HERTS,AL7 1HE. TELEPHONE: 01707 527 630NORWICH LONDON DUBLIN THE HAGUE

C210

608

MARSHMOUTH LANERESIDENTIAL BOURTON ON THAMES

PROPOSED DRAINAGESCHEME

C210608-PIN-XX-XX-DR-C-0205 P01

FOR APPROVAL

1:200 JULY 21 TWR JJ

50mm ON A1 DWG.0 50

NOTES

A. COVER LEVELS ARE TO BE CONFIRMED FOLLOWINGRECEIPT OF LEVELS DESIGN.

B. ALL PROPOSED DRAINAGE PIPE WORK TO BE PVC.


Appendix B – BRE365 Infiltration test

Tweedie Evans Consulting Limited trading as TEC Registered Office: One New Street, Wells, BA5 2LA Company Registration No. 5186011

Our Ref: 2011011.002.01 Your Ref:

09 April 2021 Neil Strelitz Orwell Real Estate Ltd. Level 5 27‐32 Old Jewry London EC2R 8JL

Dear Neil

LAND OFF MARSHMOUTH LANE, BOURTON‐ON‐THE‐WATER – SOAKAGE TESTING

Tweedie Evans Consulting Ltd (TEC) has been appointed by Orwell Real Estate to undertake soakage testing at the above site. Works have been undertaken in accordance with our proposal email dated 16th February 2021 titled “Marshmouth Lane ‐ Surface Water Disposal” and subsequent email of 22nd March 2021.

Background

The site is located off Marshmouth Lane, at the southern boundary of Bourton‐on‐the‐Water (Figure 1). The site covers an area of approximately 0.42 hectares, with the centre of the site situated at approximate National Grid Reference 417144, 220128. The nearest postcode is GL54 2DT.

Soakage testing, in general accordance with the methodology outlined in BRE365, was requested to determine the drainage properties of the underlying materials in relation to the proposed development of the site.

The published geology records the site to consist of alluvial deposits, comprising of clay, silt, sand and gravel, presumably associated with the nearby River Windrush. Directly beneath the Alluvial Deposits the Charmouth Mudstone Formation is recorded.

A previous exploratory investigation undertaken by TEC in 2020 recorded made ground to depths between 0.9m and 1.6m, followed by Alluvium, recorded as medium dense grey‐brown silty sandy gravel of fine to coarse angular to rounded limestone, to approximately 3.7mbgl with underlying Charmouth Mudstone Formation to the final depth of 5.0mbgl. The solid geology was generally described as a firm to stiff grey slightly sandy silty clay.

Groundwater strikes were recorded within the superficial deposits at approximate depths between 1.34m and 2.0m with resting water levels recorded at depths of between 1.34m and 1.6m.

Further, groundwater monitoring standpipes, installed as part of the previous investigation works, recorded standing water levels as follows:

Borehole December 2020 April 2021

WS01 1.60m 1.61m

WS02 1.37m 1.43m

Methodology

Two soakage tests were carried out on 1st April 2021 in general accordance with the methodology outlined in BRE365:2016 at agreed locations on the site. Full test results are enclosed, and the location of trial pit / soakage test is shown on the enclosed Figure 2.

The Old Chapel35a Southover Wells Somerset BA5 1UH t: 01749 677760 w: www.tecon.co.uk

09 April 2021

Tweedie Evans Consulting Limited trading as TEC Registered Office: One New Street, Wells, BA5 2LA Company Registration No. 5186011

Page 2

Encountered Ground Conditions

A summary of the encountered ground conditions is presented below, with detailed descriptions presented on the enclosed exploratory hole logs.

Ground conditions were recorded to comprise made ground material at depths of between 0.9m and 1.47mbgl, recorded as a brown slightly gravelly sandy silty clay with high cobble and boulder content, followed by a dark brown slightly black and orangish brown slightly sandy gravelly clayey silt with orangish brown staining. The gravel was recorded as brick, limestone, flint, metal, tarmac, rope, plastic, porcelain fragments and wood. The cobbles and boulders comprised limestone concrete. The natural ground encountered comprised brown slightly sandy silty clay with rare gravel. The gravel was recorded as fine to medium subangular mudstone and limestone which extended up to depths of between 0.5m and 0.6mbgl. Within trail pit SA03, grey mottled yellowish‐brown silty clay was encountered to 0.9mbgl. Further within all trial pit locations grey mottled yellowish‐brown and white, slightly gravelly calcareous silty clay was encountered. The gravel was recorded as white fine subangular to subrounded carbonate concretions to depths between 1.05m to 1.25mbgl.

The natural ground encountered within SA01 comprised a greyish brown and yellowish‐brown sandy gravel to a final depth of 2.00mbgl. Within SA02, the natural material comprised of a dark brown and grey slightly gravelly slightly sandy organic clay to approximately 1.15mbgl, followed by a very soft greenish grey and brownish grey mottled orangish brown organic clay to approximately 1.47mbgl, followed by greenish grey and grey sandy gravel to the final depth of 1.6mbgl.

Groundwater was encountered within both trial pits: within SA01, groundwater ingress was recorded at 2.0mbgl, with a standing water level of 1.86m some 30minutes after finishing the excavation while at SA02 the recorded groundwater ingress was at 1.6m with a standing water level of 1.53m after 15minutes.

Soakage Test Results

Soakage testing was undertaken at SA01 & SA02 in general accordance with the methodology outlined in BRE Digest 365 (2016). The tests failed to drain the required three times at both locations. However, at SA01 only a single fill was achieved with the test draining once during the available time (~4 hours). At SA02, the tested drained a total of 6mm in the available time (~4 hours).

Given this an initial infiltration rate of 2.0 x 10‐5m/s has been estimated in accordance with BRE365 for the test undertaken at SA01 within the sandy gravel recorded the groundwater, i.e., between 1.47m and 1.77mbgl.

Based on these initial findings, the ground materials within the area of the test may potentially provide a suitable drainage medium for the site and the use of soakaways within the proposed development may be feasible. However, it would be recommended that a drainage engineer is consulted with regards to the required attenuation for the scheme, given the findings of these initial works. In addition, it should be noted that while initial data suggests groundwater levels to be relatively static, with similar levels recorded in December 2020 and April 2021, it may be necessary to establish maximum winter groundwater levels and additional monitoring over the winter period may be required to establish the feasibility of using soakaways at the site.

Closure

We hope you find the above to your satisfaction, but should you have queries please do not hesitate to contact us.

Yours sincerely

Reinier van der Kuip Richard Evans

Engineering Geologist Director

TEC encs

Figure 1 – Site Location Plan

Figure 2 – Exploratory Hole Location Plan

Exploratory Hole Logs


Photographs

FIGURES AND DRAWINGS

Client Name: Project No: Date: Figure No:

Scale:

Approximate Site Location:Ordnance Survey © Crown Copyright [2021] All rights reserved.License number 100043301

Extract of RPS Group drawing 9435-0012-0006 dated April 2018.

WS01

WS02

WS03

DCP1

DCP2

DCP3

*All locations are approximate

Previous TEC Dynamic Cone Penetrometer (2020)

Trial Pit/Soakage Test Location (2021)

Previous TEC Borehole Location, with Installation (2020)

Previous TEC Borehole Location (2020)

SA02

SA01

Exploratory Hole Logs

Trial Pit LogTrialpit NoSA01

Sheet 1 of 1Project Name:

Marshmouth Lane, Bourton-on-the-Water

Project No.2011011.002

Co-ords:Level:

417162.00 - 220139.00mbgl

Date01/04/2021

Location:

Client:

Bourton-on-the-Water

Orwell Real Estate Ltd.

Dimensions:Inclination: °Orientation: °Depth: 2.0m

0.53

m

2.35m Scale1:15

LoggedRK

Remarks:

Stability:

Groundwater ingress at 2.00mbgl. Standing groundwater level at 1.86mbgl 30min after excavation.

Stable.

Wat

erSt

rike Samples and In Situ Testing

Depth Type Results InformationDepth

(m)

0.25

0.35

1.47

2.00

Level(m) Legend Stratum Description

MADE GROUND: Brown slightly gravelly sandy silty clay with high cobble and boulder content. Gravel is brick, limestone, tarmacadam, rope, plastic and wood. Cobbles and boulders are limestone and concrete.

Frequent rootlets to 0.20mMADE GROUND: Light brown sandy gravel with low cobble content. Gravel is limestone. Cobbles are limestone and concrete.MADE GROUND: Dark brown slightly black and orangish brown slightly sandy gravelly clayey silt with orangish brown staining. Gravel is flint, metal, porcelain fragments, plastic and frequent wood.

Slight organic odour from 0.35m to 1.47m

Greyish brown and yellowish brown sandy GRAVEL. Sand is fine to coarse grained. Gravel is fine to coarse subangular to subrounded limestone.

End of pit at 2.0 m

1

2

3

Trial Pit LogTrialpit NoSA02

Sheet 1 of 1Project Name:

Marshmouth Lane, Bourton-on-the-Water

Project No.2011011.002

Co-ords:Level:

417139.00 - 220118.00mbgl

Date01/04/2021

Location:

Client:

Bourton-on-the-Water

Orwell Real Estate Ltd.

Dimensions:Inclination: °Orientation: °Depth: 1.6m

0.50

m

2.15m Scale1:15

LoggedRK

Remarks:

Stability:

Groundwater ingress at 1.60mbgl. Standing groundwater level at 1.53mbgl 15min after excavation.

Stable.

Wat

erSt

rike Samples and In Situ Testing

Depth Type Results InformationDepth

(m)

0.15

0.27

0.90

1.15

1.47

1.60

Level(m) Legend Stratum Description

MADE GROUND: Brown slightly gravelly clayey, sandy silt. Gravel is limestone, brick, flint and wood.MADE GROUND: Light brown sandy gravel. Gravel is limestone and concrete.

Frequent rootlets to 0.18mMADE GROUND: Brown and yellowish brown gravelly sandy clay with low cobble content. Gravel is limestone and wood. Cobbles are limestone.

Soft dark brown and grey slightly gravelly slightly sandy organic CLAY. Sand is fine to coarse grained. Gravel is angular to subrounded limestone.

Very soft greenish grey and brownish grey mottled orangish brown organic CLAY.

Frequent roots from 1.15m to 1.40m

PP at 1.30m = >0.5kg/cm2

Greenish grey and grey sandy GRAVEL. Sand is fine to coarse grained. Gravel is fine to medium subangular to subrounded limestone.

End of pit at 1.6 m

1

2

3


Trial Pit Soakage Test Summary Sheet

BRE Digest 365 (2016) Soakaway Design

Test 1 Test 2 Test 3

Time (m) Depth (mm bgl) Time (m) Depth (mm bgl) Time (m) Depth (mm bgl)

0.00 1460

1.00 1470

2.00 1480

3.00 1490

10.00 1530

12.00 1535

20.00 1575

22.00 1580

34.00 1610

41.00 1620

50.0 1640

68.0 1670

83.0 1690

100.0 1700

122.0 1710 Pit reference SA01

146.0 1720 Pit depth (m) 2.00

173.00 1730 Pit width (m) 0.53

194.00 1732 Pit length (m) 2.35

205.00 1735 Depth to standing water (m) 1.86

225.00 1740 Granular Fill used to stabilise the pit? N

250.00 1745


Max. depth (mm bgl) 1860 -

Effective depth (mm bgl) 1460

Effective drop (mm) 400

25% effective depth (mm bgl) 1560



t25 (min) -

t75 (min) -

Vp75-25 (m3) -

ap50 (m2) -

tp75-25 (min) -

Soil Infiltration Rate (m/sec)

Soil Infiltration Rate (mm/hr)

Extrapolated Data?

Infiltration calculated to method in BRE Digest 365 (2016) Soakaway Design

Project: Marshmouth Lane, Bourton-on-the-Water

Project Number: 2011011.002Test Pit Reference: SA01

Ground Conditions / Comments

Note: Where granular fill used to stabilise the test pit, assume there to be 30% free volume.

No Infiltration Rate Calculated

No

Client: Orwell Real Estate

Operator: RK

Test Date: 01/04/2020

1200

1300

1400

1500

1600

1700

1800

1900

2000

0 30 60 90 120 150 180 210 240 270

Dep

th (

mm

bgl

)

Time (mins)

Test 1

TWEEDIE EVANS CONSULTING Form TEC SF001 (RevA)

Trial Pit Soakage Test Summary Sheet

BRE Digest 365 (2016) Soakaway Design


Time (m) Depth (mm bgl) Time (m) Depth (mm bgl) Time (m) Depth (mm bgl)

0.00 1001

1.00 1002

2.00 1002

5.00 1002

7.00 1002

14.00 1002

18.00 1002

25.00 1002

36.00 1003

46.00 1003

63.0 1003

78.0 1004

95.0 1004

118.0 1005

141.0 1005 Pit reference SA02

171.0 1006 Pit depth (m) 1.60

200.00 1006 Pit width (m) 0.50

245.00 1007 Pit length (m) 2.15

Depth to standing water (m) 1.53

Granular Fill used to stabilise the pit? N


Max. depth (mm bgl) 1530 -

Effective depth (mm bgl) 1001

Effective drop (mm) 529




t25 (min) -

t75 (min) -

Vp75-25 (m3) -

ap50 (m2) -

tp75-25 (min) -

Soil Infiltration Rate (m/sec)

Soil Infiltration Rate (mm/hr)

Extrapolated Data?

Infiltration calculated to method in BRE Digest 365 (2016) Soakaway Design

No Infiltration Rate Calculated

No

Project: Marshmouth Lane, Bourton-on-the-Water

Project Number: 2011011.002Test Pit Reference: SA02

Ground Conditions / Comments

Note: Where granular fill used to stabilise the test pit, assume there to be 30% free volume.

Client: Orwell Real Estate

Operator: RK

Test Date: 01/04/2020

600

700

800

900

1000

1100

1200

1300

1400

1500

1600

0 30 60 90 120 150 180 210 240 270

Dep

th (

mm

bgl

)

Time (mins)

Test 1

TWEEDIE EVANS CONSULTING Form TEC SF001 (RevA)

Site Photographs

Land Off Marshmouth Lane, Bourton‐on‐the‐Water

Orwell Real Estate 2011011.002 Prepared by TEC

Photograph 1: View across proposed development area, facing north.

Photograph 2: View across proposed development area, facing south.



Photograph 3: View across proposed development site, facing east.

Photograph 4: View facing west towards River Windrush.



Photograph 5: Arisings encountered at SA01.

Photograph 6: View of trial pit SA01.



Photograph 7: Arisings encountered at SA02.

Photograph 8: View of trial pit SA02.


Appendix C – Microdrainage Calculations

Pinnacle Consulting Engineers Limited Page 1Pinnacle House Bourton3 Meridian WayNorwich NR7 0TADate 09/07/2021 09:37 Designed by Richard PearsonFile SW DRAIANGE.MDX Checked by Jawsy JabbarXP Solutions Network 2019.1

STORM SEWER DESIGN by the Modified Rational Method

Design Criteria for Storm

©1982-2019 Innovyze

Pipe Sizes STANDARD Manhole Sizes STANDARD

FEH Rainfall ModelReturn Period (years) 1FEH Rainfall Version 1999

Site Location GB 417150 220100 SP 17150 20100C (1km) -0.023D1 (1km) 0.368D2 (1km) 0.328D3 (1km) 0.271E (1km) 0.290F (1km) 2.450

Maximum Rainfall (mm/hr) 50Maximum Time of Concentration (mins) 30

Foul Sewage (l/s/ha) 0.000Volumetric Runoff Coeff. 0.750

PIMP (%) 100Add Flow / Climate Change (%) 0Minimum Backdrop Height (m) 0.200Maximum Backdrop Height (m) 1.500

Min Design Depth for Optimisation (m) 1.200Min Vel for Auto Design only (m/s) 1.00Min Slope for Optimisation (1:X) 500

Designed with Level Soffits

Network Design Table for Storm

PN Length(m)

Fall(m)

Slope(1:X)

I.Area(ha)

T.E.(mins)

BaseFlow (l/s)

k(mm)

HYDSECT

DIA(mm)

Section Type AutoDesign

1.000 13.949 0.090 155.0 0.004 5.00 0.0 0.600 o 150 Pipe/Conduit1.001 6.542 0.045 145.4 0.006 0.00 0.0 0.600 o 150 Pipe/Conduit


Network Results Table

PN Rain(mm/hr)

T.C.(mins)

US/IL(m)

Σ I.Area(ha)

Σ BaseFlow (l/s)

Foul(l/s)

Add Flow(l/s)

Vel(m/s)

Cap(l/s)

Flow(l/s)

1.000 50.00 5.29 127.650 0.004 0.0 0.0 0.0 0.80 14.2 0.51.001 50.00 5.42 127.560 0.010 0.0 0.0 0.0 0.83 14.7 1.4

2.000 50.00 5.25 127.650 0.003 0.0 0.0 0.0 0.80 14.1 0.42.001 50.00 5.42 127.575 0.006 0.0 0.0 0.0 0.84 14.9 0.9


Network Design Table for Storm


PN Length(m)

Fall(m)

Slope(1:X)

I.Area(ha)

T.E.(mins)

BaseFlow (l/s)

k(mm)

HYDSECT

DIA(mm)

Section Type AutoDesign





1.004 4.270 0.030 142.3 0.000 0.00 0.0 0.600 o 150 Pipe/Conduit

Network Results Table

PN Rain(mm/hr)

T.C.(mins)

US/IL(m)

Σ I.Area(ha)

Σ BaseFlow (l/s)

Foul(l/s)

Add Flow(l/s)

Vel(m/s)

Cap(l/s)

Flow(l/s)

1.002 50.00 5.51 127.515 0.019 0.0 0.0 0.0 0.64 11.3 2.61.003 50.00 5.71 127.500 0.019 0.0 0.0 0.0 0.81 14.2 2.6

3.000 50.00 5.28 127.650 0.004 0.0 0.0 0.0 0.82 14.4 0.53.001 50.00 5.48 127.560 0.010 0.0 0.0 0.0 0.82 14.4 1.4

4.000 50.00 5.25 127.650 0.003 0.0 0.0 0.0 0.80 14.1 0.54.001 50.00 5.37 127.575 0.007 0.0 0.0 0.0 0.82 14.5 0.9

3.002 50.00 5.56 127.495 0.019 0.0 0.0 0.0 0.68 12.0 2.63.003 50.00 5.72 127.480 0.019 0.0 0.0 0.0 0.80 14.1 2.6

1.004 50.00 5.81 127.430 0.038 0.0 0.0 0.0 0.84 14.8 5.2


Manhole Schedules for Storm


MHName

MHCL (m)

MHDepth(m)

MHConnection

MHDiam.,L*W

(mm)PN

Pipe OutInvert

Level (m)Diameter(mm)

PNPipes InInvert

Level (m)Diameter(mm)

Backdrop(mm)

1.0 128.100 0.450 Open Manhole 600 1.000 127.650 150

1.1 128.100 0.540 Open Manhole 600 1.001 127.560 150 1.000 127.560 150

2.0 128.100 0.450 Open Manhole 600 2.000 127.650 150

2.1 128.100 0.525 Open Manhole 600 2.001 127.575 150 2.000 127.575 150

1.2 128.100 0.585 Open Manhole 600 1.002 127.515 150 1.001 127.515 150

2.001 127.515 150

Tank 1 128.100 0.600 Open Manhole 600 1.003 127.500 150 1.002 127.500 150

3.0 128.100 0.450 Open Manhole 600 3.000 127.650 150

3.1 128.100 0.540 Open Manhole 600 3.001 127.560 150 3.000 127.560 150

4.0 128.100 0.450 Open Manhole 600 4.000 127.650 150

4.1 128.100 0.525 Open Manhole 600 4.001 127.575 150 4.000 127.575 150

3.2 128.100 0.605 Open Manhole 600 3.002 127.495 150 3.001 127.495 150

4.001 127.535 150 40

Tank 2 128.100 0.620 Open Manhole 600 3.003 127.480 150 3.002 127.480 150

1.3 128.100 0.670 Open Manhole 1200 1.004 127.430 150 1.003 127.440 150 10

3.003 127.430 150

127.800 0.400 Open Manhole 0 OUTFALL 1.004 127.400 150

MHName

ManholeEasting(m)

ManholeNorthing

(m)

IntersectionEasting(m)

IntersectionNorthing

(m)

ManholeAccess

Layout(North)

1.0 417143.984 220125.772 417143.984 220125.772 Required

1.1 417131.417 220119.719 417131.417 220119.719 Required

2.0 417133.147 220138.719 417133.147 220138.719 Required

2.1 417123.209 220132.334 417123.209 220132.334 Required

1.2 417127.794 220125.166 417127.794 220125.166 Required

Tank 1 417126.249 220121.872 417126.249 220121.872 Required


Manhole Schedules for Storm


3.0 417153.556 220108.113 417153.556 220108.113 Required

3.1 417141.052 220102.794 417141.052 220102.794 Required

4.0 417142.182 220122.416 417142.182 220122.416 Required

4.1 417132.373 220115.918 417132.373 220115.918 Required

3.2 417135.660 220110.947 417135.660 220110.947 Required

Tank 2 417132.397 220110.925 417132.397 220110.925 Required

1.3 417124.705 220112.717 417124.705 220112.717 Required

417120.767 220111.066 No Entry

MHName

ManholeEasting(m)

ManholeNorthing

(m)

IntersectionEasting(m)

IntersectionNorthing

(m)

ManholeAccess

Layout(North)


PIPELINE SCHEDULES for Storm

Upstream Manhole


PN HydSect

Diam(mm)

MHName

C.Level(m)

I.Level(m)

D.Depth(m)

MHConnection

MH DIAM., L*W(mm)

1.000 o 150 1.0 128.100 127.650 0.300 Open Manhole 6001.001 o 150 1.1 128.100 127.560 0.390 Open Manhole 600


1.002 o 150 1.2 128.100 127.515 0.435 Open Manhole 6001.003 o 150 Tank 1 128.100 127.500 0.450 Open Manhole 600



3.002 o 150 3.2 128.100 127.495 0.455 Open Manhole 6003.003 o 150 Tank 2 128.100 127.480 0.470 Open Manhole 600

1.004 o 150 1.3 128.100 127.430 0.520 Open Manhole 1200

Downstream Manhole

PN Length(m)

Slope(1:X)

MHName

C.Level(m)

I.Level(m)

D.Depth(m)

MHConnection

MH DIAM., L*W(mm)

1.000 13.949 155.0 1.1 128.100 127.560 0.390 Open Manhole 6001.001 6.542 145.4 1.2 128.100 127.515 0.435 Open Manhole 600


1.002 3.638 242.5 Tank 1 128.100 127.500 0.450 Open Manhole 6001.003 9.284 154.7 1.3 128.100 127.440 0.510 Open Manhole 1200



3.002 3.263 217.5 Tank 2 128.100 127.480 0.470 Open Manhole 6003.003 7.898 158.0 1.3 128.100 127.430 0.520 Open Manhole 1200

1.004 4.270 142.3 127.800 127.400 0.250 Open Manhole 0


Free Flowing Outfall Details for Storm


OutfallPipe Number

OutfallName

C. Level(m)

I. Level(m)

MinI. Level

(m)

D,L(mm)

W(mm)

1.004 127.800 127.400 0.000 0 0

Simulation Criteria for Storm

Volumetric Runoff Coeff 0.750 Additional Flow - % of Total Flow 0.000Areal Reduction Factor 1.000 MADD Factor * 10m³/ha Storage 2.000

Hot Start (mins) 0 Inlet Coeffiecient 0.800Hot Start Level (mm) 0 Flow per Person per Day (l/per/day) 0.000

Manhole Headloss Coeff (Global) 0.500 Run Time (mins) 60Foul Sewage per hectare (l/s) 0.000 Output Interval (mins) 1

Number of Input Hydrographs 0 Number of Offline Controls 0 Number of Time/Area Diagrams 0Number of Online Controls 1 Number of Storage Structures 2 Number of Real Time Controls 0

Synthetic Rainfall Details

Rainfall Model FEH E (1km) 0.290Return Period (years) 1 F (1km) 2.450FEH Rainfall Version 1999 Summer Storms Yes

Site Location GB 417150 220100 SP 17150 20100 Winter Storms YesC (1km) -0.023 Cv (Summer) 0.750D1 (1km) 0.368 Cv (Winter) 0.840D2 (1km) 0.328 Storm Duration (mins) 30D3 (1km) 0.271


Online Controls for Storm


Hydro-Brake® Optimum Manhole: 1.3, DS/PN: 1.004, Volume (m³): 1.0

Unit Reference MD-SHE-0073-2000-0580-2000Design Head (m) 0.580

Design Flow (l/s) 2.0Flush-Flo™ CalculatedObjective Minimise upstream storage

Application SurfaceSump Available YesDiameter (mm) 73

Invert Level (m) 127.430Minimum Outlet Pipe Diameter (mm) 100Suggested Manhole Diameter (mm) 1200

Control Points Head (m) Flow (l/s) Control Points Head (m) Flow (l/s)

Design Point (Calculated) 0.580 2.0 Kick-Flo® 0.385 1.7Flush-Flo™ 0.170 2.0 Mean Flow over Head Range - 1.7

The hydrological calculations have been based on the Head/Discharge relationship for the Hydro-Brake® Optimum asspecified. Should another type of control device other than a Hydro-Brake Optimum® be utilised then thesestorage routing calculations will be invalidated

Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s)

0.100 1.9 0.800 2.3 2.000 3.5 4.000 4.9 7.000 6.40.200 2.0 1.000 2.6 2.200 3.7 4.500 5.1 7.500 6.60.300 1.9 1.200 2.8 2.400 3.8 5.000 5.4 8.000 6.80.400 1.7 1.400 3.0 2.600 4.0 5.500 5.7 8.500 7.00.500 1.9 1.600 3.2 3.000 4.3 6.000 5.9 9.000 7.20.600 2.0 1.800 3.4 3.500 4.6 6.500 6.1 9.500 7.4


Storage Structures for Storm


Cellular Storage Manhole: Tank 1, DS/PN: 1.003

Invert Level (m) 127.540 Safety Factor 2.0Infiltration Coefficient Base (m/hr) 0.00000 Porosity 0.95Infiltration Coefficient Side (m/hr) 0.00000

Depth (m) Area (m²) Inf. Area (m²) Depth (m) Area (m²) Inf. Area (m²) Depth (m) Area (m²) Inf. Area (m²)

0.000 14.0 14.0 0.300 14.0 18.5 0.301 0.0 18.5

Cellular Storage Manhole: Tank 2, DS/PN: 3.003

Invert Level (m) 127.545 Safety Factor 2.0Infiltration Coefficient Base (m/hr) 0.00000 Porosity 0.95Infiltration Coefficient Side (m/hr) 0.00000

Depth (m) Area (m²) Inf. Area (m²) Depth (m) Area (m²) Inf. Area (m²) Depth (m) Area (m²) Inf. Area (m²)

0.000 14.0 14.0 0.300 14.0 18.5 0.301 0.0 18.5


Summary of Critical Results by Maximum Level (Rank 1) for Storm


Simulation CriteriaAreal Reduction Factor 1.000 Additional Flow - % of Total Flow 0.000

Hot Start (mins) 0 MADD Factor * 10m³/ha Storage 2.000Hot Start Level (mm) 0 Inlet Coeffiecient 0.800

Manhole Headloss Coeff (Global) 0.500 Flow per Person per Day (l/per/day) 0.000Foul Sewage per hectare (l/s) 0.000

Number of Input Hydrographs 0 Number of Offline Controls 0 Number of Time/Area Diagrams 0Number of Online Controls 1 Number of Storage Structures 2 Number of Real Time Controls 0

Synthetic Rainfall DetailsRainfall Model FEH D3 (1km) 0.271

FEH Rainfall Version 1999 E (1km) 0.290Site Location GB 417150 220100 SP 17150 20100 F (1km) 2.450

C (1km) -0.023 Cv (Summer) 0.750D1 (1km) 0.368 Cv (Winter) 0.840D2 (1km) 0.328

Margin for Flood Risk Warning (mm) 300.0Analysis Timestep 2.5 Second Increment (Extended)

DTS Status ONDVD Status OFF

Inertia Status OFF

Profile(s) Summer and WinterDuration(s) (mins) 15, 30, 60, 120, 180, 240, 360, 480, 600, 720, 960, 1440

Return Period(s) (years) 1, 30, 100Climate Change (%) 0, 0, 40

PNUS/MHName Storm

ReturnPeriod

ClimateChange

First (X)Surcharge

First (Y)Flood

First (Z)Overflow

OverflowAct.

Water Level(m)

SurchargedDepth(m)

FloodedVolume(m³)

1.000 1.0 30 Winter 100 +40% 100/15 Summer 128.098 0.298 0.0001.001 1.1 30 Winter 100 +40% 100/15 Summer 128.097 0.387 0.0002.000 2.0 30 Winter 100 +40% 100/15 Summer 128.096 0.296 0.0002.001 2.1 60 Winter 100 +40% 100/15 Summer 128.095 0.370 0.0001.002 1.2 60 Winter 100 +40% 30/15 Winter 128.095 0.430 0.0001.003 Tank 1 60 Winter 100 +40% 30/15 Winter 128.099 0.449 0.0003.000 3.0 30 Winter 100 +40% 100/15 Summer 128.099 0.299 0.0003.001 3.1 60 Winter 100 +40% 100/15 Summer 128.098 0.388 0.0004.000 4.0 30 Winter 100 +40% 100/15 Summer 128.096 0.296 0.0004.001 4.1 60 Winter 100 +40% 100/15 Summer 128.095 0.370 0.0003.002 3.2 60 Winter 100 +40% 30/15 Summer 128.095 0.450 0.0003.003 Tank 2 60 Winter 100 +40% 30/15 Summer 128.099 0.469 0.0001.004 1.3 60 Winter 100 +40% 30/15 Summer 128.099 0.519 0.000


Summary of Critical Results by Maximum Level (Rank 1) for Storm


PNUS/MHName

Flow /Cap.

Overflow(l/s)

PipeFlow(l/s) Status

LevelExceeded

1.000 1.0 0.14 1.9 FLOOD RISK1.001 1.1 0.36 4.5 FLOOD RISK2.000 2.0 0.13 1.6 FLOOD RISK2.001 2.1 0.13 1.7 FLOOD RISK1.002 1.2 0.51 5.1 FLOOD RISK1.003 Tank 1 0.15 1.9 FLOOD RISK3.000 3.0 0.14 1.9 FLOOD RISK3.001 3.1 0.22 2.9 FLOOD RISK4.000 4.0 0.13 1.6 FLOOD RISK4.001 4.1 0.15 1.8 FLOOD RISK3.002 3.2 0.51 5.3 FLOOD RISK3.003 Tank 2 0.11 1.3 FLOOD RISK1.004 1.3 0.19 2.0 FLOOD RISK

Documents

Drainage Condition Discharge