Proposed Residential Development on Land Off Boscoppa Road, St Austell, Cornwall

PROPOSED RESIDENTIAL DEVELOPMENT ON LAND OFF BOSCOPPA ROAD, ST AUSTELL, CORNWALL

FLOOD RISK ASSESSMENT & SURFACE WATER DRAINAGE STRATEGY J-1803-Rev.01

www.eadsolutions.co.uk

PROPOSED RESIDENTIAL DEVELOPMENT ON LAND OFF BOSCOPPA ROAD, ST AUSTELL, CORNWALL

FLOOD RISK ASSESSMENT & SURFACE WATER DRAINAGE STRATEGY

Report No. Issue Detail Originator Date Checked by Date

J-1803 01 JM 16/04/2021 JC 16/04/2021

For: Ms Ruth Allen Job No: J-1803 No 2. Boscoppa Farm Date: April 2021 Boscoppa Road Edition: 04 St Austell PL25 3TE

www.eadsolutions.co.uk

CONTENTS

Item Content Page No.

1.0 Introduction 1

2.0 Site Location & Description 3

3.0 Assessment of Flood Risks 4

4.0 Design Standards 6

5.0 Proposed Sustainable Drainage System (SuDS) 7

6.0 Summary and Conclusions 11

APPENDICES

Appendix A Topographic Survey and Proposed Site Drainage Plan

Appendix B Calculations

www.eadsolutions.co.uk ______

J-1803 Flood Risk Assessment – Residential Development at Boscoppa Road, St Austell ______

1.0 INTRODUCTION

Ms Ruth Allen is proposing to develop land off Boscoppa Road, St Austell, PL25-3DQ in order to provide 61 residential units, associated access and drives. The site is proposed to have a new access off Aspen Drive, which is located to the northern boundary of the site. The site location and wider geographical area are shown in Figures 1 and 2 below.

Site Location

Figure 1 Geographical Area & Location

Site Boundary

Figure 2 Geographical Area & Location (aerial photo view)

Engineering and Development Solutions Ltd Registered Office: Engineering and Development Solutions, Unit 10 Penstraze Business Centre, Truro, Cornwall, TR4 8PN Registered in England and Wales No. 10467487 Phone 01872 306311 Mobile 07973816457 1 ______

J-1803 Flood Risk Assessment – Residential Development at Boscoppa Road, St Austell ______

During the planning process, it has become apparent that the site lies within the St Austell Critical Drainage Area and that the proposal is for over 10 units and would class as a major development as such the development will require a Flood Risk Assessment (FRA) in accordance with the National Planning Policy Framework (NPPF) on Planning and Flood Risk.

As the site is within Flood Zone 1 (Low Probability), the primary aim of the FRA will be to ensure that the development does not increase flood risk elsewhere. This can be achieved by providing a suitable sustainable drainage scheme (SuDS) that manages surface water runoff from the development.

To address this requirement, Engineering & Development Solutions (EDS) have been commissioned to prepare an FRA including a surface water drainage strategy for the proposed development, in accordance with the best practice principles of SuDS, the National Planning Policy Framework (NPPF), Drainage Guidance for Cornwall (DGfC) and Planning Practice Guidance (PPG). This report details the findings of the study.

J-1803 Flood Risk Assessment – Residential Development at Boscoppa Road, St Austell ______

2.0 SITE LOCATION & DESCRIPTION

Site Location

The proposed development site is located in Boscoppa which is an amalgamation of the town St Austell. The site covers an area of around 2.2ha. The approximate Ordnance Survey Grid Reference for the site is SX 03619 53573.

The site is positioned on the western side of the A391, with residential dwellings to the north, west and south. Agricultural land and a handful of residential properties are situated to the east of the A391.

In terms of existing site topography, the site falls radially from a highpoint in the north-western boundary at an elevation of 99.20m AOD to a low point at a level of 87m AOD on the south- eastern boundary. Existing site levels are shown on the proposed site plan in Appendix A.

In a wider context, the site lies approximately 1.38km south of the local high point, which has an elevation of approximately 206m AOD. The land south of the site slopes gently down towards St Austell bay, which is located approximately 1.9km south.

Existing Usage

The site currently comprises agricultural land on the eastern edge of St Austell.

Proposed Usage

The development proposal is for 61 residential units with associated parking, access road and infrastructure. The proposed layout is shown in Appendix A.

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3.0 ASSESSMENT OF FLOOD RISKS

Fluvial and Tidal Flooding

The site is located approximately 750m west of the Tregrehan Stream, a tributary of the Tregrehan stream is culverted underneath the south portion of the site. The Environment Agency indicative flood map for planning (Figure 3, below) shows that the entire site is in Flood Zone 1 (less than 1 in 1,000 annual probability of river or sea flooding) and is therefore not at risk from either fluvial or tidal flooding.

Site Location

Figure 3 Environment Agency Flood Map for Planning (Rivers & Sea) Extract

Groundwater

Groundwater flooding is linked to the ability of the ground to hold water. The Cornwall Council Strategic Flood Risk Assessment (SFRA) highlights that the geology of Cornwall has only minor aquifers and generally does not experience much groundwater flooding.

In addition, trial pits opened on site for percolation testing to a maximum depth of 2m showed no evidence of any groundwater. As such, groundwater flooding is not considered any further in this report.

Overland Flow

The site is located towards the upper boundary of an urban catchment with residential buildings located upslope with existing highway drainage in place. It is anticipated that rainfall generated upslope of the site during low to medium order rainfall events would be channelled around the north easter corner of the site.

The potential for flooding from overland sheet flow is therefore considered to be low.

The EA map extract, Figure 4 below, shows the risk of flooding from surface water for the site. It indicates that the site is at very low risk of flooding from surface water with the exception of the north east corner being at a low risk. During extreme rainfall events, the road network is likely act as a surface conveyance feature for overland flow and would act to carry flows past

J-1803 Flood Risk Assessment – Residential Development at Boscoppa Road, St Austell ______

the site in an eastly direction. As such, it is considered that the site is not at significant risk of surface water flooding.

Site Location

Figure 4 EA Flood Risk from Surface Water Map Extract

Flooding from Reservoirs, Canals and Other Artificial Sources

With reference to 1:25,000 Ordnance Survey mapping and aerial imagery, there appear to be no impounded waterbodies within the vicinity of the site, therefore flooding of the site from these sources can be discounted.

Flooding as a Result of Development

The development of the site will alter the nature of the surface permeability throughout the site. The development will create impermeable areas through the implementation of residential units and paved areas where there are currently greenfield permeable areas. Thus, the rate at which water runs off these areas could increase. Consequently, it is important that surface water runoff from the development is understood and managed by means of a sustainable surface water drainage system, to prevent an increase in the risk of flooding to areas downstream of the site.

By designing the site’s surface water drainage infrastructure in accordance with the advice reproduced in Section 4, the proposed development will not increase flood risk to third parties downslope. In consideration of the above, the proposed sustainable drainage system to be installed within the development is described in more detail in Section 5 of this report.

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4.0 DESIGN STANDARDS

Design of the site drainage infrastructure and Sustainable Drainage System (SuDs) is to be carried out in line with best practice, and to industry standard design procedures. Several publications, including design guidance and best practice guidance will be applied to different components of the final SuDs infrastructure. The sections below provide an overview of the design standards to be used on this project for various aspects of the SuDs infrastructure design.

The CIRIA SuDS Manual (C753)

This document is a comprehensive publication covering design, construction, operation and maintenance of SuDs. The advice and best practice outlined in this document has been utilised in the design of the site SuDs features which have been detailed in this report.

Building Regulations Part H

Building Regulations Part H ‘Drainage and Waste Disposal’ covers the design and installation of surface water and foul water systems. All private drainage including pipes, manholes, down pipes, and other drainage infrastructure on the site should be designed and installed in accordance with this document.

The Wallingford Procedure

Developed by HR Wallingford, this publication covers the design of urban drainage systems. In addition, the document includes regional rainfall data for use in design for varying return period events. Basic sizing calculations for the proposed SuDS system and the estimation of the runoff volumes have been made using this method.

National Planning Policy Framework

The National Planning Policy Framework (NPPF) contains the policy relating to the appropriate assessment of flood risk within the UK. The associated technical guidance provides further details on the definitions, classifications and constraints used to apply national policy to new developments.

It contains details on flood zone definition, site specific FRA’s, vulnerability classifications, appropriate development, climate change allowances, residual risk management, flood resilience, the sequential test and the exception test.

Minimum Drainage Standards Required

All new developments will have to play their part in reducing current rainfall runoff rates. This requirement also applies to brownfield sites that will have to match the same standards. The surface water drainage hierarchy should be followed by using infiltration as far as is practicable. Further guidance on such systems can be found in the CIRIA SuDS Manual and in Lead Local Flood Authority guidance.

All off-site surface water discharges from developments should mimic greenfield performance up to a maximum 1 in 10-year discharge rate. On site all surface water should be safely managed up to the 1 in 100 plus climate change conditions. This will require additional water storage areas to be created thereby contributing to a reduction in flooding downstream.

With regards to the guidance above, a drainage design has been proposed below.

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5.0 PROPOSED SUSTAINABLE DRAINAGE SYSTEM (SUDS)

The preferable drainage solution for the site would be to drain all surface water runoff from the development using infiltration, in line with best practice guidance to deal with runoff as close to source as possible.

Site investigation work was undertaken in line with BRE 365/CIRIA 156 on 23/03/2021. Percolation tests were carried out in four trial pits across the site; the results are summarised below and included in Appendix B. The pits showed there is a variability across the site.

Trial Pit Infiltration Rate (m/s) Infiltration Rate (m/hr) TP1 2.64 x 10-4 0.150 TP2 Fail Fail TP3 7.52 x 10-4 2.707 TP4 Fail Fail

As such a soakaway-based drainage system for the site has been outlined in areas of good infiltration. The infiltration rates used for each of the soakaways in the SuDS scheme has been calculated by using the infiltration rate observed in the nearest percolation test pit to the proposed position of the soakaway. Areas that have no percolation will therefore have to be attenuated to a suitable receptor.

Drainage Design – Infiltration System

As per the guidance outlined in Section 4 above, as per the guidance outlined above, the preferable drainage solution for the site would be to drain all surface water runoff from the development to ground soakaways designed to a minimum 100-year return period storm with a 40% climate change allowance.

Residential Units

The Building Regulations Part H places several restrictions on the siting of soakaways which should be complied with. This includes that soakaways should not be sited within 5m of any building or road. They should also be sufficiently far from other soakaways and drainage fields so that the overall soakage capacity of the ground is not exceeded or the effectiveness of the units impaired.

The proposed development layout (Drawing 3001 Option) included in Annex A shows the layout of the soakaways on site. A system of downpipes and gullies would convey surface water from the impermeable areas of the new development into the soakaways. A total of 17 soakaways have been sized in accordance with the guidance found in CIRIA 156; calculations are included in Appendix B. The soakaway sizes are based on how much impermeable area serves each soakaway.

Access Road

The main access roads serving the site will remain private. Ideally, the soakaways would be situated in an area of public open space which can be readily accessed for maintenance. The proposed drainage layout (Drawing 3001) included in Appendix A shows the indicative layout of the soakaways on the site.

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Drainage Design – Attenuation System

Where infiltration-based drainage methods are not feasible on site. The surface water run-off from these areas will need to be attenuated on site and discharged to a suitable receptor at an appropriate rate in line with the requirements of the CDA standing advice.

Site Location

SWW Surface Water Sewer

SWW Foul Sewer

Figure 5 SWWIM Extract

A review of The South West Water Interactive Mapping system (SWWIM) (Figure 5) shows the nearest SWW surface water sewer runs though the prosed development area. Therefore, it is proposed to discharge the surface water into the surface water on site. This will require a section 106 to allow any connection to the sewer.

The greenfield runoff rate for the remining development has been calculated, using the ICP SUDS method, to be about 2 l/s based on a return period of 100 years. As such this flow rate has been used to size a storage device.

Surface water originating from the impermeable areas of the development (roofs) and parking area would drain via a positively piped drainage system towards a flow control device. MicroDrainage software has been used to size the storage required to facilitate a discharge limited to change to 10 years 2 l/s for an impermeable area of 3,660m2.

These Calculations indicate a minimum tank size of 307.4m3, to accommodate the worst-case design storm (100-year) with rainfall intensities increased by 40% to allow for the effects of climate change as required by the standing advice. The minimum tank size could be achieved by using a tank with the dimensions of 4.5m (w) x 45m (l) x 1.6m (d). Outflow from the tank

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would be controlled by means of a flow control device within a manhole. If the upstream flow rate exceeds 2 l/s, flows will back up into the proposed attenuation tank.

The proposed drainage layout (Drawing 3001A) included in Annex A shows the proposed layout of the surface water attenuation system at the site. Calculations for the conceptual surface water drainage option are presented in Annex B.

Exceedance Events

In the unlikely event of a storm in excess of the 1 in 100 year return period rainfall event (including climate change allowance) or if the proposed drainage system were to become blocked, water may surcharge from the system. In this case it is considered that the overflowing water would run over ground towards the south of the site, as per the pre-developed scenario.

Due to the storage provided in the proposed infiltration/Attenuation systems, and design standards used (1 in 100-year storm with an additional 40% allowance for the effects of climate change), any exceedance flows would be lower than would flow off the site in the pre- development scenario for a similar storm event.

Maintenance

Management and maintenance responsibility for the individual soakaways serving each house will fall to the householder. Maintenance will include regular inspection of the upstream silt traps serving the soakaway with removal and disposal of any silt or debris (e.g. leaves) that has accumulated in an appropriate manner.

Maintenance of the highway soakaways will be undertaken by a management company set up for the site and responsible for the public open spaces and the private access road. Maintenance will comprise regular (recommended to be at 6 monthly intervals) inspection of the upstream catch pit serving the soakaway with removal and disposal of any silt or debris (e.g. leaves) that has accumulated in an appropriate manner.

SOAKAWAYS Inspect for sediment and debris in Annually upstream silt traps and floor of inspection tube or chamber Regular maintenance Cleaning of gutters and any filters on Annually (or as required downpipes based on inspections) Trimming any roots that may be Annually (or as required) causing blockages Remove sediment and debris from As required, based on Occasional maintenance upstream silt traps and floor of inspections inspection tube or chamber Reconstruct soakaway and/or replace As required or clean units if performance deteriorates or failure occurs Remedial actions Replacement of clogged geotextile As required (will required reconstruction of soakaway) Inspect silt traps and note rate of Monthly in the first year sediment accumulation then annually Monitoring Check soakaway to ensure emptying Annually is occurring

J-1803 Flood Risk Assessment – Residential Development at Boscoppa Road, St Austell ______

Maintenance of the attenuation tank will be undertaken by a management company set up for the site. Maintenance activities will broadly comprise regular maintenance, occasional tasks and remedial work where necessary, as per the guidance in the CIRIA SuDS Manual (C753) 2015

ATTENUATION TANK Required Action Typical Frequency Inspect and identify any areas that are not Monthly for 3 months, operating correctly. If required, take then annually remedial action Remove debris form the catchment surface Monthly (where it may cause risks to performance) For systems where rainfall infiltrates into the Annually Regular maintenance tank form above, check surface of filter for blockage by sediment, algae or other matter; remove and replace surface infiltration medium as necessary Remove sediment from pre-treatment Annually, or as required structures and/or internal forebays Repair/rehabilitate inlets, outlet, overflows As required Remedial actions and vents Inspect/check all inlets, outlets, vents and Annually overflows to ensure they are in good Monitoring condition and operating as designed Survey inside of tank for sediment build-up Every 5 years or as and remove if necessary required

Residual Risks After Development

Rainfall over and above the design event could cause the sustainable drainage system to surcharge, however, any exceedance flows would be dealt with as outlined above.

The sustainable surface water drainage system proposed in this report has been designed for the volume of surface runoff resulting from the proposed development, thus any unauthorised future connections into the soakaway network could potentially overload the system. Any future development on the site, beyond the current proposal, should be suitably planned and considered.

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6.0 SUMMARY AND CONCLUSIONS

This study has investigated mechanisms of flooding and the potential for Sustainable Drainage (SuDS) to be installed as part of the development on land off Boscoppa Road, St Austell.

Environment Agency (EA) indicative flood mapping shows that the development site is located entirely within Flood Zone 1; at little or no risk from tidal or fluvial flooding and is therefore suitable for all types of development. The development proposal is for over ten residential units, within a critical drainage area and therefore further consideration of surface water drainage has been undertaken.

The study has investigated alternative mechanisms for flooding at the site and has concluded that the site is not at risk of flooding and will not cause any increase in flood risk elsewhere once the proposed sustainable drainage system is operational. Indeed the use of infiltration drainage will reduce the level of runoff from the site when compared to the pre-development scenario.

Infiltration testing undertaken on the site shows a variability across the site. As such a soakaway-based drainage system for the site has been outlined in areas of good infiltration and this has been designed to the 100-year standard with a 40% allowance for climate change. Where infiltration is not feasible, surface water will be discharged to the SWW surface water on site at the 10yr greenfield run off flow rate of 2l/s.

It is recommended to conduct more percolation tests on the site to achieve a greater understanding of the rates of infiltration across the whole of the site. The final design of the surface water drainage system should be reviewed on the basis of further percolation testing.

Provided the recommendations outlined in this report are adopted in the development proposal then there is the capacity to manage the surface water runoff from the development onsite. Regarding the criteria outlined in the NPPF, PPG and the CDA, the development is appropriate on this site from a flood risk perspective.

APPENDIX A TOPOGRAPHIC SURVEY AND PROPOSED SITE DRAINAGE PLAN

ASPEN DRIVE

TIMBER FENCE ACCESS Cornish Hedge

EX. MH A1 CL:95.10 FFL:94.70

EX. MH Existing natural area provding buffer to A391 Cornish Hedge B/S P1 TIMBER FENCE P1 A2 FFL:94.30

Cornish Hedge C61 P61 FFL:97.00

B/S

P60 B/S B/S P60 P2 P2 C3 B4 FFL:93.90 B60 FFL:95.10 FFL:97.30 B5 FFL:93.90 B59 P59 B/S FFL:97.30 P59

B/S B/S P58 TIMBER FENCE

P58 B/S P4 Cornish Hedge P3 A58 B/S D6 FFL:97.70 P4 FFL:93.80

B/S P5 D7 P6 FFL:93.50 P5 P11 A57 P6 D8 FFL:93.20 FFL:98.00 P11 Existing natural P12 B/S area provding P12 B/S E11 P7 buffer to A391 B/S P57 FFL:96.00 Cornish Hedge E56 P13 P7 B9 FFL:92.90 FFL:98.20 P57 B/S P13 E12 FFL:96.30 P14 P8 E55 P56 B/S FFL:98.20 P8 P9 P14 B/S B10 TIMBER FENCE B/S P56 E13 FFL:96.60 FFL:92.90 P55 P9 E54 P15 play FFL:98.20 P55 E14 P15 FFL:96.90 area B/S P54 B/S P54 B/S C23 Cornish Hedge B15 P10 FFL:92.70 B/S FFL:96.90 P53 P10 P53 B16 B24 FFL:96.90 E22 FFL:91.80 B53 E21 FFL:94.00 B/S FFL:98.00 E20 FFL:94.30 B/S E19 FFL:94.60 B/S B17 FFL:94.90 P52 FFL:95.70 B18 P24 B25 P16 B/S P23 B52 FFL:95.70 FFL:91.80 FFL:98.00 P17 Cornish Hedge P52 P51 TIMBER FENCE P16 P24 B/S P51 P17 B/S B/S P22 B/S B/S P22 B/S P21 P18 P21 F26 P20 P25 P20 FFL:91.00 P50 P19 P19 P50 P18 P25 F51 P49 FFL:97.50 F27 P49 B/S FFL:90.60 P38 P26 P40 P39 F50 B/S P26 Cornish Hedge FFL:97.10 P27 Existing natural B/S P38 F28 P48 P41 P40 area provding P41 P39 B/S FFL:90.20 P42 buffer to A391 P48 P42 B/S TIMBER FENCE P43 P43 P27 P44 F49 P44 B/S P47 P45 P28 FFL:96.40 P45 P37 B/S P28 Cornish Hedge P47 P46 P36 B/S P37 B/S B/S B/S G29- P36 B/S F48 34 FFL:96.00 P46 B38 B/S FFL:89.20 FFL:92.35 B37 B/S Cornish Hedge D39 FFL:92.35 D40 FFL:93.50 E42 D41 FFL:93.80 E43 FFL:94.30 FFL:94.10 E44 FFL:94.60 E45 FFL:94.90 A36 B/S Flood Risk Assessment Highway Design B47 FFL:95.20 FFL:91.50 · · FFL:95.50 B46 · SuDS and Surface Water · Civil Engineering FFL:95.50 P35 B/S A35 P29 · Foul and Sewage Treatment · Statutory Approvals FFL:91.00 Cornish Hedge P35 Cornish Hedge P30 Cornish Hedge EDS, Unit 10, Penstraze Business Centre, Truro, Cornwall TR4 8PN Cornish Hedge P31 TIMBER FENCE EX. IC (01872) 306311 (Mob) 07973816457 CL:89.71 Cornish Hedge Email: [email protected] EX. IC www.eadsolutions.co.uk CL:89.59 P32 P33 Cornish Hedgefootpath P34

Cornish Hedge

Cornish Hedge footpath

APPENDIX B CALCULATIONS

Job No. Job Name Prepared Date Unit 10 Penstraze Business Centre, Truro, J-1803 Boscoppa Farm EDS 09/04/2021 Cornwall, TR4 8PN Tel 07973816457

Pit Dimensions Depth (m) Length (m) Width (m) Test Date: 24/03/2021 2.00 2.00 0.60 Trial Pit No.: TP1 Test No.: 1 Soakaway test - tabulated data Time Depth to Elapsed Water Volume % Effective % Effective Vol (m3) T (sec) (hh:mm) Water (m) Time (sec) Depth (m) (m3) 11:12 1.25 0 0.75 100% 0.90 80% 0.72 300 11:17 1.40 300 0.60 80% 0.72 67% 0.60 600 11:22 1.50 600 0.50 67% 0.60 75% 0.68 413 11:27 1.58 900 0.42 56% 0.50 25% 0.23 2700 11:32 1.62 1200 0.38 51% 0.46 23% 0.21 3000 11:37 1.68 1500 0.32 43% 0.38 25% 0.23 2750 11:42 1.71 1800 0.29 39% 0.35 75%-25% 0.45 2337 11:47 1.74 2100 0.27 35% 0.32 11:52 1.77 2400 0.23 31% 0.28 Effective Values Summary 11:57 1.81 2700 0.19 25% 0.23 Datum (0,0) is ground level at pit 12:02 1.83 3000 0.18 23% 0.21 Initial Depth 1.25 m (below datum) 12:07 1.87 3300 0.13 17% 0.16 Final Depth 2.00 m (below datum) 12:12 1.90 3600 0.10 13% 0.12 Storage Depth 0.75 m (effective depth) 2 12:17 1.95 3900 0.05 7% 0.06 ap50% 3.15 m 12:22 2.00 4200 0.00 0% 0.00 FALSE FALSE FALSE FALSE FALSE FALSE

FALSE q = Vp75-25

ap50 x tp75-25 Where: ap50%: Internal surface area of pite up to 50% effective depth, including base area tp75-25: Time for water to dall from 75% to 25% effective depth q= 6.11E-05 m/sec

Vp75-25: Effective storage volume between 75% & 25% effective depth 0.220 m/hr 0.80

0.70

0.60 75%

0.50

0.40

0.30 Water Depth (m) 25% 0.20

0.10

0.00 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Time (seconds) Job No. Job Name Prepared Date Unit 10 Penstraze Business Centre, Truro, J-1803 Boscoppa Farm EDS 09/04/2021 Cornwall, TR4 8PN Tel 07973816457

Pit Dimensions Depth (m) Length (m) Width (m) Test Date: 24/03/2021 2.00 2.00 0.60 Trial Pit No.: TP1 Test No.: 2 Soakaway test - tabulated data Time Depth to Elapsed Water Volume % Effective % Effective Vol (m3) T (sec) (hh:mm) Water (m) Time (sec) Depth (m) (m3) 12:47 1.25 0 0.75 100% 0.90 100% 0.90 0 13:00 1.55 780 0.45 60% 0.54 60% 0.54 780 13:15 1.62 1680 0.38 51% 0.46 75% 0.68 487 13:30 1.70 2580 0.30 40% 0.36 34% 0.31 3060 13:38 1.75 3060 0.26 34% 0.31 20% 0.18 4380 14:00 1.85 4380 0.15 20% 0.18 25% 0.23 3909 14:20 2.00 5580 0.00 0% 0.00 75%-25% 0.45 3421 FALSE FALSE Effective Values Summary FALSE Datum (0,0) is ground level at pit FALSE Initial Depth 1.25 m (below datum) FALSE Final Depth 2.00 m (below datum) FALSE Storage Depth 0.75 m (effective depth) 2 FALSE ap50% 3.15 m FALSE FALSE FALSE FALSE FALSE FALSE FALSE

FALSE q = Vp75-25

ap50 x tp75-25 Where: ap50%: Internal surface area of pite up to 50% effective depth, including base area tp75-25: Time for water to dall from 75% to 25% effective depth q= 4.18E-05 m/sec

Vp75-25: Effective storage volume between 75% & 25% effective depth 0.150 m/hr 0.80

0.70

0.60 75%

0.50

0.40

0.30 Water Depth (m) 25% 0.20

0.10

0.00 0 1000 2000 3000 4000 5000 6000 Time (seconds) Job No. Job Name Prepared Date Unit 10 Penstraze Business Centre, Truro, J-1803 Boscoppa Farm EDS 09/04/2021 Cornwall, TR4 8PN Tel 07973816457

Pit Dimensions Depth (m) Length (m) Width (m) Test Date: 24/03/2021 2.00 2.00 0.60 Trial Pit No.: TP1 Test No.: 3 Soakaway test - tabulated data Time Depth to Elapsed Water Volume % Effective % Effective Vol (m3) T (sec) (hh:mm) Water (m) Time (sec) Depth (m) (m3) 14:32 1.25 0 0.75 100% 0.90 100% 0.90 0 14:45 1.52 780 0.48 64% 0.58 64% 0.58 780 15:00 1.64 1680 0.36 48% 0.43 75% 0.68 542 15:15 1.74 2580 0.26 35% 0.31 28% 0.25 3480 15:30 1.79 3480 0.21 28% 0.25 20% 0.18 4380 15:45 1.85 4380 0.15 20% 0.18 25% 0.23 3818 16:00 1.95 5280 0.05 7% 0.06 75%-25% 0.45 3276 16:10 2.00 5880 0.00 0% 0.00 FALSE Effective Values Summary FALSE Datum (0,0) is ground level at pit FALSE Initial Depth 1.25 m (below datum) FALSE Final Depth 2.00 m (below datum) FALSE Storage Depth 0.75 m (effective depth) 2 FALSE ap50% 3.15 m FALSE FALSE FALSE FALSE FALSE FALSE FALSE

FALSE q = Vp75-25

ap50 x tp75-25 Where: ap50%: Internal surface area of pite up to 50% effective depth, including base area tp75-25: Time for water to dall from 75% to 25% effective depth q= 4.36E-05 m/sec

Vp75-25: Effective storage volume between 75% & 25% effective depth 0.157 m/hr 0.80

0.70

0.60 75%

0.50

0.40

0.30 Water Depth (m) 25% 0.20

0.10

0.00 0 1000 2000 3000 4000 5000 6000 7000 Time (seconds) Job No. Job Name Prepared Date Unit 10 Penstraze Business Centre, Truro, J-1803 Boscoppa Farm EDS 09/04/2021 Cornwall, TR4 8PN Tel 07973816457

Pit Dimensions Depth (m) Length (m) Width (m) Test Date: 24/03/2021 2.00 2.00 0.60 Trial Pit No.: TP3 Test No.: 1 Soakaway test - tabulated data Time Depth to Elapsed Water Volume % Effective % Effective Vol (m3) T (sec) (hh:mm) Water (m) Time (sec) Depth (m) (m3) 12:05 1.00 0 1.00 100% 1.20 100% 1.20 0 12:10 2.00 300 0.00 0% 0.00 0% 0.00 300 FALSE 75% 0.90 75 FALSE 100% 1.20 0 FALSE 0% 0.00 300 FALSE 25% 0.30 225 FALSE 75%-25% 0.60 150 FALSE FALSE Effective Values Summary FALSE Datum (0,0) is ground level at pit FALSE Initial Depth 1.00 m (below datum) FALSE Final Depth 2.00 m (below datum) FALSE Storage Depth 1.00 m (effective depth) 2 FALSE ap50% 3.80 m FALSE FALSE FALSE FALSE FALSE FALSE FALSE

FALSE q = Vp75-25

ap50 x tp75-25 Where: ap50%: Internal surface area of pite up to 50% effective depth, including base area tp75-25: Time for water to dall from 75% to 25% effective depth q= 1.05E-03 m/sec

Vp75-25: Effective storage volume between 75% & 25% effective depth 3.789 m/hr 1.20

1.00

0.80 75%

0.60

Water Depth (m) 0.40 25%

0.20

0.00 0 50 100 150 200 250 300 350 Time (seconds) Job No. Job Name Prepared Date Unit 10 Penstraze Business Centre, Truro, J-1803 Boscoppa Farm EDS 09/04/2021 Cornwall, TR4 8PN Tel 07973816457

Pit Dimensions Depth (m) Length (m) Width (m) Test Date: 24/03/2021 2.00 2.00 0.60 Trial Pit No.: TP3 Test No.: 2 Soakaway test - tabulated data Time Depth to Elapsed Water Volume % Effective % Effective Vol (m3) T (sec) (hh:mm) Water (m) Time (sec) Depth (m) (m3) 15:32 1.00 0 1.00 100% 1.20 100% 1.20 0 15:35 1.50 180 0.50 50% 0.60 50% 0.60 180 15:39 2.00 420 0.00 0% 0.00 75% 0.90 90 FALSE 50% 0.60 180 FALSE 0% 0.00 420 FALSE 25% 0.30 300 FALSE 75%-25% 0.60 210 FALSE FALSE Effective Values Summary FALSE Datum (0,0) is ground level at pit FALSE Initial Depth 1.00 m (below datum) FALSE Final Depth 2.00 m (below datum) FALSE Storage Depth 1.00 m (effective depth) 2 FALSE ap50% 3.80 m FALSE FALSE FALSE FALSE FALSE FALSE FALSE

FALSE q = Vp75-25

ap50 x tp75-25 Where: ap50%: Internal surface area of pite up to 50% effective depth, including base area tp75-25: Time for water to dall from 75% to 25% effective depth q= 7.52E-04 m/sec

Vp75-25: Effective storage volume between 75% & 25% effective depth 2.707 m/hr 1.20

1.00

0.80 75%

0.60

Water Depth (m) 0.40 25%

0.20

0.00 0 50 100 150 200 250 300 350 400 450 Time (seconds) Infiltration Testing in accordance with CIRIA 156 'Infiltration drainage - Manual of good practice'

Summary of Infiltration Testing

ADAS Appendix 5 Permeability Descriptions (for average 2m x .6m x 2m dp pit) Permeability low high low high low high Description (m/day) (m/day) (m/hr) (m/hr) (m/s) (m/s) Very Slow 0.01 0.10 0.000 0.004 1.2E-07 1.2E-06 Slow-moderate 0.1 0.30 0.004 0.013 1.2E-06 3.5E-06 Moderate 0.3 1.00 0.013 0.042 3.5E-06 1.2E-05 Mod-rapid 1.0 10.0 0.042 0.417 1.2E-05 1.2E-04 Very rapid 10 0.417 1.2E-04

Table 1.0 Summary of results Trial Pit Infiltration Q, m/sec Q, m/s m/hr m/day Description Test 1 Test 2 Test 3 (min) TP1 6.11E-05 4.18E-05 4.36E-05 4.18E-05 0.15 3.61 Mod-rapid TP2 1.05E-03 7.52E-04 7.52E-04 2.71 64.96 Very rapid TP3 TP4 EDS Ltd Page 1 Unit 10, Penstraze Business ... J-1803 Truro Attenuation Calcs Cornwall Boscappa Road, St Austel Date 12/04/2021 Designed by Joshua Munyard File J-1803 Attenuation Calc... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Half Drain Time : 1489 minutes.

Storm Max Max Max Max Max Max Max Status Event Level Depth Infiltration Control Overflow Σ Outflow Volume (m) (m) (l/s) (l/s) (l/s) (l/s) (m³)

15 min Summer 98.172 0.372 0.0 1.5 0.0 1.5 71.6 O K 30 min Summer 98.325 0.525 0.0 1.5 0.0 1.5 101.1 O K 60 min Summer 98.506 0.706 0.0 1.5 0.0 1.5 135.8 O K 120 min Summer 98.705 0.905 0.0 1.5 0.0 1.5 174.1 O K 180 min Summer 98.819 1.019 0.0 1.6 0.0 1.6 196.0 O K 240 min Summer 98.893 1.093 0.0 1.7 0.0 1.7 210.2 O K 360 min Summer 98.997 1.197 0.0 1.7 0.0 1.7 230.2 O K 480 min Summer 99.063 1.263 0.0 1.8 0.0 1.8 243.0 O K 600 min Summer 99.107 1.307 0.0 1.8 0.0 1.8 251.4 O K 720 min Summer 99.136 1.336 0.0 1.8 0.0 1.8 257.1 O K 960 min Summer 99.166 1.366 0.0 1.9 0.0 1.9 262.7 O K 1440 min Summer 99.176 1.376 0.0 1.9 0.0 1.9 264.7 O K 2160 min Summer 99.160 1.360 0.0 1.9 0.0 1.9 261.6 O K 2880 min Summer 99.130 1.330 0.0 1.8 0.0 1.8 255.8 O K 4320 min Summer 99.066 1.266 0.0 1.8 0.0 1.8 243.5 O K 5760 min Summer 99.000 1.200 0.0 1.8 0.0 1.8 230.9 O K 7200 min Summer 98.935 1.135 0.0 1.7 0.0 1.7 218.4 O K 8640 min Summer 98.872 1.072 0.0 1.7 0.0 1.7 206.3 O K 10080 min Summer 98.813 1.013 0.0 1.6 0.0 1.6 194.8 O K 15 min Winter 98.218 0.418 0.0 1.5 0.0 1.5 80.4 O K

Storm Rain Flooded Discharge Overflow Time-Peak Event (mm/hr) Volume Volume Volume (mins) (m³) (m³) (m³)

15 min Summer 106.750 0.0 71.4 0.0 26 30 min Summer 75.427 0.0 100.0 0.0 41 60 min Summer 51.110 0.0 139.2 0.0 70 120 min Summer 33.394 0.0 181.7 0.0 130 180 min Summer 25.539 0.0 207.8 0.0 188 240 min Summer 20.912 0.0 225.8 0.0 248 360 min Summer 15.794 0.0 248.3 0.0 366 480 min Summer 12.912 0.0 253.5 0.0 486 600 min Summer 11.031 0.0 255.2 0.0 604 720 min Summer 9.691 0.0 256.3 0.0 722 960 min Summer 7.889 0.0 258.3 0.0 960 1440 min Summer 5.886 0.0 263.4 0.0 1216 2160 min Summer 4.376 0.0 431.0 0.0 1600 2880 min Summer 3.539 0.0 463.3 0.0 2016 4320 min Summer 2.628 0.0 462.6 0.0 2852 5760 min Summer 2.130 0.0 560.9 0.0 3688 7200 min Summer 1.810 0.0 595.9 0.0 4480 8640 min Summer 1.587 0.0 626.6 0.0 5288 10080 min Summer 1.420 0.0 654.0 0.0 6152 15 min Winter 106.750 0.0 79.9 0.0 26

©1982-2020 Innovyze EDS Ltd Page 2 Unit 10, Penstraze Business ... J-1803 Truro Attenuation Calcs Cornwall Boscappa Road, St Austel Date 12/04/2021 Designed by Joshua Munyard File J-1803 Attenuation Calc... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Storm Max Max Max Max Max Max Max Status Event Level Depth Infiltration Control Overflow Σ Outflow Volume (m) (m) (l/s) (l/s) (l/s) (l/s) (m³)

30 min Winter 98.390 0.590 0.0 1.5 0.0 1.5 113.5 O K 60 min Winter 98.593 0.793 0.0 1.5 0.0 1.5 152.5 O K 120 min Winter 98.818 1.018 0.0 1.6 0.0 1.6 195.9 O K 180 min Winter 98.949 1.149 0.0 1.7 0.0 1.7 221.1 O K 240 min Winter 99.035 1.235 0.0 1.8 0.0 1.8 237.5 O K 360 min Winter 99.157 1.357 0.0 1.9 0.0 1.9 261.1 O K 480 min Winter 99.237 1.437 0.0 1.9 0.0 1.9 276.5 O K 600 min Winter 99.293 1.493 0.0 1.9 0.0 1.9 287.2 O K 720 min Winter 99.332 1.532 0.0 2.0 0.0 2.0 294.7 O K 960 min Winter 99.378 1.578 0.0 2.0 0.0 2.0 303.5 O K 1440 min Winter 99.398 1.598 0.0 2.0 0.0 2.0 307.4 O K 2160 min Winter 99.375 1.575 0.0 2.0 0.0 2.0 303.0 O K 2880 min Winter 99.333 1.533 0.0 2.0 0.0 2.0 294.9 O K 4320 min Winter 99.231 1.431 0.0 1.9 0.0 1.9 275.3 O K 5760 min Winter 99.125 1.325 0.0 1.8 0.0 1.8 254.8 O K 7200 min Winter 99.021 1.221 0.0 1.8 0.0 1.8 234.9 O K 8640 min Winter 98.923 1.123 0.0 1.7 0.0 1.7 216.0 O K 10080 min Winter 98.831 1.031 0.0 1.6 0.0 1.6 198.3 O K

Storm Rain Flooded Discharge Overflow Time-Peak Event (mm/hr) Volume Volume Volume (mins) (m³) (m³) (m³)

30 min Winter 75.427 0.0 110.3 0.0 41 60 min Winter 51.110 0.0 155.9 0.0 70 120 min Winter 33.394 0.0 203.1 0.0 128 180 min Winter 25.539 0.0 231.3 0.0 186 240 min Winter 20.912 0.0 248.0 0.0 244 360 min Winter 15.794 0.0 257.7 0.0 360 480 min Winter 12.912 0.0 261.1 0.0 476 600 min Winter 11.031 0.0 264.0 0.0 590 720 min Winter 9.691 0.0 267.0 0.0 704 960 min Winter 7.889 0.0 273.9 0.0 928 1440 min Winter 5.886 0.0 279.8 0.0 1348 2160 min Winter 4.376 0.0 482.0 0.0 1688 2880 min Winter 3.539 0.0 512.5 0.0 2160 4320 min Winter 2.628 0.0 491.0 0.0 3072 5760 min Winter 2.130 0.0 628.2 0.0 3976 7200 min Winter 1.810 0.0 667.4 0.0 4832 8640 min Winter 1.587 0.0 701.7 0.0 5704 10080 min Winter 1.420 0.0 732.3 0.0 6560

©1982-2020 Innovyze EDS Ltd Page 3 Unit 10, Penstraze Business ... J-1803 Truro Attenuation Calcs Cornwall Boscappa Road, St Austel Date 12/04/2021 Designed by Joshua Munyard File J-1803 Attenuation Calc... Checked by Innovyze Source Control 2020.1

Rainfall Details

Rainfall Model FSR Winter Storms Yes Return Period (years) 100 Cv (Summer) 0.750 Region England and Wales Cv (Winter) 0.840 M5-60 (mm) 18.100 Shortest Storm (mins) 15 Ratio R 0.262 Longest Storm (mins) 10080 Summer Storms Yes Climate Change % +40

Time Area Diagram

Total Area (ha) 0.366

Time (mins) Area Time (mins) Area Time (mins) Area From: To: (ha) From: To: (ha) From: To: (ha)

0 4 0.122 4 8 0.122 8 12 0.122

©1982-2020 Innovyze EDS Ltd Page 4 Unit 10, Penstraze Business ... J-1803 Truro Attenuation Calcs Cornwall Boscappa Road, St Austel Date 12/04/2021 Designed by Joshua Munyard File J-1803 Attenuation Calc... Checked by Innovyze Source Control 2020.1

Model Details

Storage is Online Cover Level (m) 100.000

Cellular Storage Structure

Invert Level (m) 97.800 Safety Factor 2.0 Infiltration Coefficient Base (m/hr) 0.00000 Porosity 0.95 Infiltration Coefficient Side (m/hr) 0.00000

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

0.000 202.5 202.5 1.601 0.0 360.9 1.600 202.5 360.9

Hydro-Brake® Optimum Outflow Control

Unit Reference MD-SHE-0060-2000-1600-2000 Design Head (m) 1.600 Design Flow (l/s) 2.0 Flush-Flo™ Calculated Objective Minimise upstream storage Application Surface Sump Available Yes Diameter (mm) 60 Invert Level (m) 97.800 Minimum Outlet Pipe Diameter (mm) 75 Suggested Manhole Diameter (mm) 1200

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

Design Point (Calculated) 1.600 2.0 Flush-Flo™ 0.263 1.5 Kick-Flo® 0.536 1.2 Mean Flow over Head Range - 1.5

The hydrological calculations have been based on the Head/Discharge relationship for the Hydro-Brake® Optimum as specified. Should another type of control device other than a Hydro-Brake Optimum® be utilised then these storage 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)

0.100 1.3 1.200 1.8 3.000 2.7 7.000 4.0 0.200 1.5 1.400 1.9 3.500 2.9 7.500 4.1 0.300 1.5 1.600 2.0 4.000 3.0 8.000 4.2 0.400 1.5 1.800 2.1 4.500 3.2 8.500 4.3 0.500 1.3 2.000 2.2 5.000 3.4 9.000 4.4 0.600 1.3 2.200 2.3 5.500 3.5 9.500 4.6 0.800 1.5 2.400 2.4 6.000 3.7 1.000 1.6 2.600 2.5 6.500 3.8

©1982-2020 Innovyze EDS Ltd Page 5 Unit 10, Penstraze Business ... J-1803 Truro Attenuation Calcs Cornwall Boscappa Road, St Austel Date 12/04/2021 Designed by Joshua Munyard File J-1803 Attenuation Calc... Checked by Innovyze Source Control 2020.1

Pipe Overflow Control

Diameter (m) 0.225 Entry Loss Coefficient 0.500 Slope (1:X) 10.0 Coefficient of Contraction 0.600 Length (m) 10.000 Upstream Invert Level (m) 99.400 Roughness k (mm) 0.600

©1982-2020 Innovyze EDS Ltd Page 1 Unit 10, Penstraze Business ... J-1803 Truro 0.15 m/h, 130m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Half Drain Time : 272 minutes.

Storm Max Max Max Max Status Event Level Depth Infiltration Volume (m) (m) (l/s) (m³)

15 min Summer 98.348 0.348 0.2 2.5 O K 30 min Summer 98.482 0.482 0.2 3.4 O K 60 min Summer 98.626 0.626 0.2 4.5 O K 120 min Summer 98.756 0.756 0.2 5.4 O K 180 min Summer 98.804 0.804 0.2 5.7 O K 240 min Summer 98.822 0.822 0.2 5.9 O K 360 min Summer 98.841 0.841 0.2 6.0 O K 480 min Summer 98.843 0.843 0.2 6.0 O K 600 min Summer 98.836 0.836 0.2 6.0 O K 720 min Summer 98.824 0.824 0.2 5.9 O K 960 min Summer 98.796 0.796 0.2 5.7 O K 1440 min Summer 98.734 0.734 0.2 5.2 O K 2160 min Summer 98.643 0.643 0.2 4.6 O K 2880 min Summer 98.561 0.561 0.2 4.0 O K 4320 min Summer 98.430 0.430 0.2 3.1 O K 5760 min Summer 98.330 0.330 0.2 2.4 O K 7200 min Summer 98.253 0.253 0.1 1.8 O K 8640 min Summer 98.192 0.192 0.1 1.4 O K 10080 min Summer 98.143 0.143 0.1 1.0 O K 15 min Winter 98.392 0.392 0.2 2.8 O K

Storm Rain Flooded Time-Peak Event (mm/hr) Volume (mins) (m³)

15 min Summer 106.750 0.0 18 30 min Summer 75.427 0.0 33 60 min Summer 51.110 0.0 62 120 min Summer 33.394 0.0 122 180 min Summer 25.539 0.0 180 240 min Summer 20.912 0.0 206 360 min Summer 15.794 0.0 270 480 min Summer 12.912 0.0 338 600 min Summer 11.031 0.0 408 720 min Summer 9.691 0.0 478 960 min Summer 7.889 0.0 616 1440 min Summer 5.886 0.0 892 2160 min Summer 4.376 0.0 1280 2880 min Summer 3.539 0.0 1672 4320 min Summer 2.628 0.0 2420 5760 min Summer 2.130 0.0 3168 7200 min Summer 1.810 0.0 3888 8640 min Summer 1.587 0.0 4584 10080 min Summer 1.420 0.0 5336 15 min Winter 106.750 0.0 18

©1982-2020 Innovyze EDS Ltd Page 2 Unit 10, Penstraze Business ... J-1803 Truro 0.15 m/h, 130m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Storm Max Max Max Max Status Event Level Depth Infiltration Volume (m) (m) (l/s) (m³)

30 min Winter 98.543 0.543 0.2 3.9 O K 60 min Winter 98.707 0.707 0.2 5.0 O K 120 min Winter 98.861 0.861 0.2 6.1 O K 180 min Winter 98.924 0.924 0.2 6.6 O K 240 min Winter 98.945 0.945 0.2 6.7 O K 360 min Winter 98.963 0.963 0.3 6.9 O K 480 min Winter 98.962 0.962 0.3 6.9 O K 600 min Winter 98.949 0.949 0.2 6.8 O K 720 min Winter 98.929 0.929 0.2 6.6 O K 960 min Winter 98.881 0.881 0.2 6.3 O K 1440 min Winter 98.781 0.781 0.2 5.6 O K 2160 min Winter 98.644 0.644 0.2 4.6 O K 2880 min Winter 98.529 0.529 0.2 3.8 O K 4320 min Winter 98.354 0.354 0.2 2.5 O K 5760 min Winter 98.230 0.230 0.1 1.6 O K 7200 min Winter 98.140 0.140 0.1 1.0 O K 8640 min Winter 98.076 0.076 0.1 0.5 O K 10080 min Winter 98.049 0.049 0.1 0.3 O K

Storm Rain Flooded Time-Peak Event (mm/hr) Volume (mins) (m³)

30 min Winter 75.427 0.0 32 60 min Winter 51.110 0.0 62 120 min Winter 33.394 0.0 118 180 min Winter 25.539 0.0 174 240 min Winter 20.912 0.0 226 360 min Winter 15.794 0.0 282 480 min Winter 12.912 0.0 360 600 min Winter 11.031 0.0 438 720 min Winter 9.691 0.0 514 960 min Winter 7.889 0.0 664 1440 min Winter 5.886 0.0 952 2160 min Winter 4.376 0.0 1364 2880 min Winter 3.539 0.0 1760 4320 min Winter 2.628 0.0 2512 5760 min Winter 2.130 0.0 3280 7200 min Winter 1.810 0.0 3960 8640 min Winter 1.587 0.0 4584 10080 min Winter 1.420 0.0 5072

©1982-2020 Innovyze EDS Ltd Page 3 Unit 10, Penstraze Business ... J-1803 Truro 0.15 m/h, 130m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Rainfall Details

Time Area Diagram

Total Area (ha) 0.013

Time (mins) Area From: To: (ha)

0 4 0.013

©1982-2020 Innovyze EDS Ltd Page 4 Unit 10, Penstraze Business ... J-1803 Truro 0.15 m/h, 130m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Model Details

Storage is Online Cover Level (m) 100.000

Cellular Storage Structure

Invert Level (m) 98.000 Safety Factor 3.0 Infiltration Coefficient Base (m/hr) 0.15000 Porosity 0.95 Infiltration Coefficient Side (m/hr) 0.15000

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

0.000 7.5 7.5 1.201 0.0 20.7 1.200 7.5 20.7

©1982-2020 Innovyze EDS Ltd Page 1 Unit 10, Penstraze Business ... J-1803 Truro 0.15 m/h, 200m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Half Drain Time : 320 minutes.

Storm Max Max Max Max Status Event Level Depth Infiltration Volume (m) (m) (l/s) (m³)

15 min Summer 98.385 0.385 0.2 3.8 O K 30 min Summer 98.533 0.533 0.2 5.3 O K 60 min Summer 98.696 0.696 0.3 6.9 O K 120 min Summer 98.849 0.849 0.3 8.5 O K 180 min Summer 98.911 0.911 0.3 9.1 O K 240 min Summer 98.934 0.934 0.3 9.3 O K 360 min Summer 98.959 0.959 0.3 9.6 O K 480 min Summer 98.966 0.966 0.3 9.6 O K 600 min Summer 98.963 0.963 0.3 9.6 O K 720 min Summer 98.953 0.953 0.3 9.5 O K 960 min Summer 98.927 0.927 0.3 9.2 O K 1440 min Summer 98.866 0.866 0.3 8.6 O K 2160 min Summer 98.773 0.773 0.3 7.7 O K 2880 min Summer 98.686 0.686 0.3 6.8 O K 4320 min Summer 98.543 0.543 0.2 5.4 O K 5760 min Summer 98.430 0.430 0.2 4.3 O K 7200 min Summer 98.341 0.341 0.2 3.4 O K 8640 min Summer 98.269 0.269 0.2 2.7 O K 10080 min Summer 98.211 0.211 0.2 2.1 O K 15 min Winter 98.432 0.432 0.2 4.3 O K

Storm Rain Flooded Time-Peak Event (mm/hr) Volume (mins) (m³)

15 min Summer 106.750 0.0 18 30 min Summer 75.427 0.0 33 60 min Summer 51.110 0.0 62 120 min Summer 33.394 0.0 122 180 min Summer 25.539 0.0 180 240 min Summer 20.912 0.0 222 360 min Summer 15.794 0.0 282 480 min Summer 12.912 0.0 348 600 min Summer 11.031 0.0 416 720 min Summer 9.691 0.0 486 960 min Summer 7.889 0.0 626 1440 min Summer 5.886 0.0 898 2160 min Summer 4.376 0.0 1300 2880 min Summer 3.539 0.0 1700 4320 min Summer 2.628 0.0 2464 5760 min Summer 2.130 0.0 3176 7200 min Summer 1.810 0.0 3896 8640 min Summer 1.587 0.0 4664 10080 min Summer 1.420 0.0 5352 15 min Winter 106.750 0.0 18

©1982-2020 Innovyze EDS Ltd Page 2 Unit 10, Penstraze Business ... J-1803 Truro 0.15 m/h, 200m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Storm Max Max Max Max Status Event Level Depth Infiltration Volume (m) (m) (l/s) (m³)

30 min Winter 98.600 0.600 0.3 6.0 O K 60 min Winter 98.786 0.786 0.3 7.8 O K 120 min Winter 98.965 0.965 0.3 9.6 O K 180 min Winter 99.044 1.044 0.3 10.4 O K 240 min Winter 99.076 1.076 0.3 10.7 O K 360 min Winter 99.100 1.100 0.3 11.0 O K 480 min Winter 99.107 1.107 0.3 11.0 O K 600 min Winter 99.100 1.100 0.3 11.0 O K 720 min Winter 99.084 1.084 0.3 10.8 O K 960 min Winter 99.038 1.038 0.3 10.4 O K 1440 min Winter 98.938 0.938 0.3 9.4 O K 2160 min Winter 98.795 0.795 0.3 7.9 O K 2880 min Winter 98.669 0.669 0.3 6.7 O K 4320 min Winter 98.473 0.473 0.2 4.7 O K 5760 min Winter 98.329 0.329 0.2 3.3 O K 7200 min Winter 98.221 0.221 0.2 2.2 O K 8640 min Winter 98.138 0.138 0.2 1.4 O K 10080 min Winter 98.078 0.078 0.2 0.8 O K

Storm Rain Flooded Time-Peak Event (mm/hr) Volume (mins) (m³)

30 min Winter 75.427 0.0 33 60 min Winter 51.110 0.0 62 120 min Winter 33.394 0.0 118 180 min Winter 25.539 0.0 176 240 min Winter 20.912 0.0 230 360 min Winter 15.794 0.0 294 480 min Winter 12.912 0.0 368 600 min Winter 11.031 0.0 446 720 min Winter 9.691 0.0 524 960 min Winter 7.889 0.0 674 1440 min Winter 5.886 0.0 968 2160 min Winter 4.376 0.0 1384 2880 min Winter 3.539 0.0 1788 4320 min Winter 2.628 0.0 2556 5760 min Winter 2.130 0.0 3336 7200 min Winter 1.810 0.0 4040 8640 min Winter 1.587 0.0 4752 10080 min Winter 1.420 0.0 5344

©1982-2020 Innovyze EDS Ltd Page 3 Unit 10, Penstraze Business ... J-1803 Truro 0.15 m/h, 200m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Rainfall Details

Time Area Diagram

Total Area (ha) 0.020

Time (mins) Area From: To: (ha)

0 4 0.020

©1982-2020 Innovyze EDS Ltd Page 4 Unit 10, Penstraze Business ... J-1803 Truro 0.15 m/h, 200m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Model Details

Storage is Online Cover Level (m) 100.000

Cellular Storage Structure

Invert Level (m) 98.000 Safety Factor 3.0 Infiltration Coefficient Base (m/hr) 0.15000 Porosity 0.95 Infiltration Coefficient Side (m/hr) 0.15000

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

0.000 10.5 10.5 1.201 0.0 26.1 1.200 10.5 26.1

©1982-2020 Innovyze EDS Ltd Page 1 Unit 10, Penstraze Business ... J-1803 Truro 0.15 m/h, 600m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Half Drain Time : 448 minutes.

Storm Max Max Max Max Status Event Level Depth Infiltration Volume (m) (m) (l/s) (m³)

15 min Summer 98.067 0.467 0.5 11.5 O K 30 min Summer 98.252 0.652 0.6 16.1 O K 60 min Summer 98.460 0.860 0.6 21.2 O K 120 min Summer 98.668 1.068 0.7 26.4 O K 180 min Summer 98.768 1.168 0.7 28.8 O K 240 min Summer 98.816 1.216 0.7 30.0 O K 360 min Summer 98.860 1.260 0.7 31.1 O K 480 min Summer 98.879 1.279 0.7 31.6 O K 600 min Summer 98.885 1.285 0.7 31.7 O K 720 min Summer 98.883 1.283 0.7 31.7 O K 960 min Summer 98.865 1.265 0.7 31.3 O K 1440 min Summer 98.809 1.209 0.7 29.9 O K 2160 min Summer 98.717 1.117 0.7 27.6 O K 2880 min Summer 98.625 1.025 0.7 25.3 O K 4320 min Summer 98.462 0.862 0.6 21.3 O K 5760 min Summer 98.325 0.725 0.6 17.9 O K 7200 min Summer 98.209 0.609 0.5 15.0 O K 8640 min Summer 98.111 0.511 0.5 12.6 O K 10080 min Summer 98.027 0.427 0.5 10.5 O K 15 min Winter 98.125 0.525 0.5 13.0 O K

Storm Rain Flooded Time-Peak Event (mm/hr) Volume (mins) (m³)

15 min Summer 106.750 0.0 22 30 min Summer 75.427 0.0 37 60 min Summer 51.110 0.0 66 120 min Summer 33.394 0.0 124 180 min Summer 25.539 0.0 182 240 min Summer 20.912 0.0 242 360 min Summer 15.794 0.0 328 480 min Summer 12.912 0.0 388 600 min Summer 11.031 0.0 452 720 min Summer 9.691 0.0 520 960 min Summer 7.889 0.0 658 1440 min Summer 5.886 0.0 938 2160 min Summer 4.376 0.0 1348 2880 min Summer 3.539 0.0 1756 4320 min Summer 2.628 0.0 2548 5760 min Summer 2.130 0.0 3288 7200 min Summer 1.810 0.0 4040 8640 min Summer 1.587 0.0 4760 10080 min Summer 1.420 0.0 5544 15 min Winter 106.750 0.0 22

©1982-2020 Innovyze EDS Ltd Page 2 Unit 10, Penstraze Business ... J-1803 Truro 0.15 m/h, 600m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Storm Max Max Max Max Status Event Level Depth Infiltration Volume (m) (m) (l/s) (m³)

30 min Winter 98.334 0.734 0.6 18.1 O K 60 min Winter 98.570 0.970 0.6 24.0 O K 120 min Winter 98.812 1.212 0.7 29.9 O K 180 min Winter 98.931 1.331 0.7 32.9 O K 240 min Winter 98.993 1.393 0.8 34.4 O K 360 min Winter 99.056 1.456 0.8 36.0 O K 480 min Winter 99.073 1.473 0.8 36.4 O K 600 min Winter 99.080 1.480 0.8 36.6 O K 720 min Winter 99.077 1.477 0.8 36.5 O K 960 min Winter 99.049 1.449 0.8 35.8 O K 1440 min Winter 98.955 1.355 0.8 33.5 O K 2160 min Winter 98.808 1.208 0.7 29.8 O K 2880 min Winter 98.667 1.067 0.7 26.3 O K 4320 min Winter 98.429 0.829 0.6 20.5 O K 5760 min Winter 98.239 0.639 0.5 15.8 O K 7200 min Winter 98.086 0.486 0.5 12.0 O K 8640 min Winter 97.962 0.362 0.5 8.9 O K 10080 min Winter 97.860 0.260 0.4 6.4 O K

Storm Rain Flooded Time-Peak Event (mm/hr) Volume (mins) (m³)

30 min Winter 75.427 0.0 36 60 min Winter 51.110 0.0 64 120 min Winter 33.394 0.0 122 180 min Winter 25.539 0.0 180 240 min Winter 20.912 0.0 236 360 min Winter 15.794 0.0 344 480 min Winter 12.912 0.0 438 600 min Winter 11.031 0.0 474 720 min Winter 9.691 0.0 552 960 min Winter 7.889 0.0 708 1440 min Winter 5.886 0.0 1012 2160 min Winter 4.376 0.0 1452 2880 min Winter 3.539 0.0 1876 4320 min Winter 2.628 0.0 2680 5760 min Winter 2.130 0.0 3456 7200 min Winter 1.810 0.0 4184 8640 min Winter 1.587 0.0 4928 10080 min Winter 1.420 0.0 5648

©1982-2020 Innovyze EDS Ltd Page 3 Unit 10, Penstraze Business ... J-1803 Truro 0.15 m/h, 600m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Rainfall Details

Time Area Diagram

Total Area (ha) 0.060

Time (mins) Area Time (mins) Area From: To: (ha) From: To: (ha)

0 4 0.030 4 8 0.030

©1982-2020 Innovyze EDS Ltd Page 4 Unit 10, Penstraze Business ... J-1803 Truro 0.15 m/h, 600m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Model Details

Storage is Online Cover Level (m) 100.000

Cellular Storage Structure

Invert Level (m) 97.600 Safety Factor 3.0 Infiltration Coefficient Base (m/hr) 0.15000 Porosity 0.95 Infiltration Coefficient Side (m/hr) 0.15000

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

0.000 26.0 26.0 1.601 0.0 59.6 1.600 26.0 59.6

©1982-2020 Innovyze EDS Ltd Page 1 Unit 10, Penstraze Business ... J-1803 Truro 2.707 m/h, 120m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Half Drain Time : 11 minutes.

Storm Max Max Max Max Status Event Level Depth Infiltration Volume (m) (m) (l/s) (m³)

15 min Summer 98.791 0.791 1.7 1.5 O K 30 min Summer 98.920 0.920 1.9 1.7 O K 60 min Summer 98.941 0.941 1.9 1.8 O K 120 min Summer 98.838 0.838 1.8 1.6 O K 180 min Summer 98.722 0.722 1.6 1.4 O K 240 min Summer 98.619 0.619 1.4 1.2 O K 360 min Summer 98.472 0.472 1.2 0.9 O K 480 min Summer 98.368 0.368 1.1 0.7 O K 600 min Summer 98.291 0.291 0.9 0.6 O K 720 min Summer 98.231 0.231 0.8 0.4 O K 960 min Summer 98.145 0.145 0.7 0.3 O K 1440 min Summer 98.050 0.050 0.6 0.1 O K 2160 min Summer 98.037 0.037 0.4 0.1 O K 2880 min Summer 98.030 0.030 0.3 0.1 O K 4320 min Summer 98.023 0.023 0.3 0.0 O K 5760 min Summer 98.018 0.018 0.2 0.0 O K 7200 min Summer 98.016 0.016 0.2 0.0 O K 8640 min Summer 98.014 0.014 0.2 0.0 O K 10080 min Summer 98.012 0.012 0.1 0.0 O K 15 min Winter 98.894 0.894 1.8 1.7 O K

Storm Rain Flooded Time-Peak Event (mm/hr) Volume (mins) (m³)

15 min Summer 106.750 0.0 13 30 min Summer 75.427 0.0 22 60 min Summer 51.110 0.0 38 120 min Summer 33.394 0.0 70 180 min Summer 25.539 0.0 102 240 min Summer 20.912 0.0 132 360 min Summer 15.794 0.0 194 480 min Summer 12.912 0.0 254 600 min Summer 11.031 0.0 314 720 min Summer 9.691 0.0 376 960 min Summer 7.889 0.0 494 1440 min Summer 5.886 0.0 720 2160 min Summer 4.376 0.0 1096 2880 min Summer 3.539 0.0 1428 4320 min Summer 2.628 0.0 2156 5760 min Summer 2.130 0.0 2912 7200 min Summer 1.810 0.0 3632 8640 min Summer 1.587 0.0 4376 10080 min Summer 1.420 0.0 5008 15 min Winter 106.750 0.0 14

©1982-2020 Innovyze EDS Ltd Page 2 Unit 10, Penstraze Business ... J-1803 Truro 2.707 m/h, 120m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Storm Max Max Max Max Status Event Level Depth Infiltration Volume (m) (m) (l/s) (m³)

30 min Winter 99.018 1.018 2.0 1.9 O K 60 min Winter 98.988 0.988 2.0 1.9 O K 120 min Winter 98.805 0.805 1.7 1.5 O K 180 min Winter 98.643 0.643 1.5 1.2 O K 240 min Winter 98.516 0.516 1.3 1.0 O K 360 min Winter 98.349 0.349 1.0 0.7 O K 480 min Winter 98.241 0.241 0.9 0.5 O K 600 min Winter 98.166 0.166 0.8 0.3 O K 720 min Winter 98.111 0.111 0.7 0.2 O K 960 min Winter 98.049 0.049 0.6 0.1 O K 1440 min Winter 98.036 0.036 0.4 0.1 O K 2160 min Winter 98.027 0.027 0.3 0.1 O K 2880 min Winter 98.022 0.022 0.3 0.0 O K 4320 min Winter 98.016 0.016 0.2 0.0 O K 5760 min Winter 98.013 0.013 0.2 0.0 O K 7200 min Winter 98.011 0.011 0.1 0.0 O K 8640 min Winter 98.010 0.010 0.1 0.0 O K 10080 min Winter 98.009 0.009 0.1 0.0 O K

Storm Rain Flooded Time-Peak Event (mm/hr) Volume (mins) (m³)

30 min Winter 75.427 0.0 23 60 min Winter 51.110 0.0 40 120 min Winter 33.394 0.0 74 180 min Winter 25.539 0.0 106 240 min Winter 20.912 0.0 136 360 min Winter 15.794 0.0 198 480 min Winter 12.912 0.0 258 600 min Winter 11.031 0.0 318 720 min Winter 9.691 0.0 378 960 min Winter 7.889 0.0 488 1440 min Winter 5.886 0.0 734 2160 min Winter 4.376 0.0 1092 2880 min Winter 3.539 0.0 1444 4320 min Winter 2.628 0.0 2148 5760 min Winter 2.130 0.0 2944 7200 min Winter 1.810 0.0 3568 8640 min Winter 1.587 0.0 4432 10080 min Winter 1.420 0.0 5112

©1982-2020 Innovyze EDS Ltd Page 3 Unit 10, Penstraze Business ... J-1803 Truro 2.707 m/h, 120m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Rainfall Details

Time Area Diagram

Total Area (ha) 0.012

Time (mins) Area From: To: (ha)

0 4 0.012

©1982-2020 Innovyze EDS Ltd Page 4 Unit 10, Penstraze Business ... J-1803 Truro 2.707 m/h, 120m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Model Details

Storage is Online Cover Level (m) 100.000

Cellular Storage Structure

Invert Level (m) 98.000 Safety Factor 3.0 Infiltration Coefficient Base (m/hr) 2.70700 Porosity 0.95 Infiltration Coefficient Side (m/hr) 2.70700

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

0.000 2.0 2.0 1.201 0.0 9.2 1.200 2.0 9.2

©1982-2020 Innovyze EDS Ltd Page 1 Unit 10, Penstraze Business ... J-1803 Truro 2.707 m/h, 240m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Half Drain Time : 16 minutes.

Storm Max Max Max Max Status Event Level Depth Infiltration Volume (m) (m) (l/s) (m³)

15 min Summer 98.847 0.847 2.7 3.2 O K 30 min Summer 99.006 1.006 3.0 3.8 O K 60 min Summer 99.065 1.065 3.1 4.0 O K 120 min Summer 98.989 0.989 3.0 3.8 O K 180 min Summer 98.874 0.874 2.8 3.3 O K 240 min Summer 98.766 0.766 2.5 2.9 O K 360 min Summer 98.598 0.598 2.2 2.3 O K 480 min Summer 98.473 0.473 2.0 1.8 O K 600 min Summer 98.377 0.377 1.8 1.4 O K 720 min Summer 98.301 0.301 1.6 1.1 O K 960 min Summer 98.190 0.190 1.4 0.7 O K 1440 min Summer 98.064 0.064 1.1 0.2 O K 2160 min Summer 98.039 0.039 0.9 0.1 O K 2880 min Summer 98.032 0.032 0.7 0.1 O K 4320 min Summer 98.024 0.024 0.5 0.1 O K 5760 min Summer 98.019 0.019 0.4 0.1 O K 7200 min Summer 98.016 0.016 0.4 0.1 O K 8640 min Summer 98.014 0.014 0.3 0.1 O K 10080 min Summer 98.013 0.013 0.3 0.1 O K 15 min Winter 98.965 0.965 2.9 3.7 O K

Storm Rain Flooded Time-Peak Event (mm/hr) Volume (mins) (m³)

15 min Summer 106.750 0.0 14 30 min Summer 75.427 0.0 23 60 min Summer 51.110 0.0 40 120 min Summer 33.394 0.0 72 180 min Summer 25.539 0.0 104 240 min Summer 20.912 0.0 136 360 min Summer 15.794 0.0 198 480 min Summer 12.912 0.0 258 600 min Summer 11.031 0.0 320 720 min Summer 9.691 0.0 378 960 min Summer 7.889 0.0 500 1440 min Summer 5.886 0.0 736 2160 min Summer 4.376 0.0 1088 2880 min Summer 3.539 0.0 1432 4320 min Summer 2.628 0.0 2196 5760 min Summer 2.130 0.0 2928 7200 min Summer 1.810 0.0 3544 8640 min Summer 1.587 0.0 4320 10080 min Summer 1.420 0.0 5040 15 min Winter 106.750 0.0 15

©1982-2020 Innovyze EDS Ltd Page 2 Unit 10, Penstraze Business ... J-1803 Truro 2.707 m/h, 240m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Storm Max Max Max Max Status Event Level Depth Infiltration Volume (m) (m) (l/s) (m³)

30 min Winter 99.134 1.134 3.3 4.3 O K 60 min Winter 99.156 1.156 3.3 4.4 O K 120 min Winter 98.995 0.995 3.0 3.8 O K 180 min Winter 98.824 0.824 2.7 3.1 O K 240 min Winter 98.677 0.677 2.4 2.6 O K 360 min Winter 98.471 0.471 1.9 1.8 O K 480 min Winter 98.330 0.330 1.7 1.3 O K 600 min Winter 98.229 0.229 1.5 0.9 O K 720 min Winter 98.153 0.153 1.3 0.6 O K 960 min Winter 98.053 0.053 1.1 0.2 O K 1440 min Winter 98.038 0.038 0.8 0.1 O K 2160 min Winter 98.028 0.028 0.6 0.1 O K 2880 min Winter 98.023 0.023 0.5 0.1 O K 4320 min Winter 98.017 0.017 0.4 0.1 O K 5760 min Winter 98.014 0.014 0.3 0.1 O K 7200 min Winter 98.012 0.012 0.3 0.0 O K 8640 min Winter 98.010 0.010 0.2 0.0 O K 10080 min Winter 98.009 0.009 0.2 0.0 O K

Storm Rain Flooded Time-Peak Event (mm/hr) Volume (mins) (m³)

30 min Winter 75.427 0.0 24 60 min Winter 51.110 0.0 42 120 min Winter 33.394 0.0 76 180 min Winter 25.539 0.0 110 240 min Winter 20.912 0.0 142 360 min Winter 15.794 0.0 204 480 min Winter 12.912 0.0 264 600 min Winter 11.031 0.0 326 720 min Winter 9.691 0.0 384 960 min Winter 7.889 0.0 492 1440 min Winter 5.886 0.0 734 2160 min Winter 4.376 0.0 1080 2880 min Winter 3.539 0.0 1420 4320 min Winter 2.628 0.0 2188 5760 min Winter 2.130 0.0 2872 7200 min Winter 1.810 0.0 3568 8640 min Winter 1.587 0.0 4392 10080 min Winter 1.420 0.0 4992

©1982-2020 Innovyze EDS Ltd Page 3 Unit 10, Penstraze Business ... J-1803 Truro 2.707 m/h, 240m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Rainfall Details

Time Area Diagram

Total Area (ha) 0.024

Time (mins) Area From: To: (ha)

0 4 0.024

©1982-2020 Innovyze EDS Ltd Page 4 Unit 10, Penstraze Business ... J-1803 Truro 2.707 m/h, 240m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Model Details

Storage is Online Cover Level (m) 100.000

Cellular Storage Structure

Invert Level (m) 98.000 Safety Factor 3.0 Infiltration Coefficient Base (m/hr) 2.70700 Porosity 0.95 Infiltration Coefficient Side (m/hr) 2.70700

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

0.000 4.0 4.0 1.201 0.0 13.6 1.200 4.0 13.6

©1982-2020 Innovyze EDS Ltd Page 1 Unit 10, Penstraze Business ... J-1803 Truro 2.707 m/h, 3270m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Half Drain Time : 57 minutes.

Storm Max Max Max Max Status Event Level Depth Infiltration Volume (m) (m) (l/s) (m³)

15 min Summer 98.396 0.796 15.1 54.4 O K 30 min Summer 98.687 1.087 16.7 74.4 O K 60 min Summer 98.902 1.302 17.9 89.1 O K 120 min Summer 98.987 1.387 18.3 94.9 O K 180 min Summer 98.967 1.367 18.2 93.5 O K 240 min Summer 98.913 1.313 17.9 89.8 O K 360 min Summer 98.795 1.195 17.3 81.7 O K 480 min Summer 98.673 1.073 16.6 73.4 O K 600 min Summer 98.556 0.956 16.0 65.4 O K 720 min Summer 98.447 0.847 15.4 58.0 O K 960 min Summer 98.258 0.658 14.4 45.0 O K 1440 min Summer 97.973 0.373 12.8 25.5 O K 2160 min Summer 97.722 0.122 11.5 8.4 O K 2880 min Summer 97.647 0.047 10.5 3.2 O K 4320 min Summer 97.635 0.035 7.8 2.4 O K 5760 min Summer 97.628 0.028 6.3 1.9 O K 7200 min Summer 97.624 0.024 5.4 1.7 O K 8640 min Summer 97.621 0.021 4.7 1.5 O K 10080 min Summer 97.619 0.019 4.3 1.3 O K 15 min Winter 98.509 0.909 15.8 62.2 O K

Storm Rain Flooded Time-Peak Event (mm/hr) Volume (mins) (m³)

15 min Summer 106.750 0.0 25 30 min Summer 75.427 0.0 36 60 min Summer 51.110 0.0 58 120 min Summer 33.394 0.0 92 180 min Summer 25.539 0.0 126 240 min Summer 20.912 0.0 160 360 min Summer 15.794 0.0 228 480 min Summer 12.912 0.0 294 600 min Summer 11.031 0.0 358 720 min Summer 9.691 0.0 420 960 min Summer 7.889 0.0 544 1440 min Summer 5.886 0.0 784 2160 min Summer 4.376 0.0 1128 2880 min Summer 3.539 0.0 1460 4320 min Summer 2.628 0.0 2172 5760 min Summer 2.130 0.0 2896 7200 min Summer 1.810 0.0 3600 8640 min Summer 1.587 0.0 4296 10080 min Summer 1.420 0.0 5072 15 min Winter 106.750 0.0 26

©1982-2020 Innovyze EDS Ltd Page 2 Unit 10, Penstraze Business ... J-1803 Truro 2.707 m/h, 3270m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Summary of Results for 100 year Return Period (+40%)

Storm Max Max Max Max Status Event Level Depth Infiltration Volume (m) (m) (l/s) (m³)

30 min Winter 98.845 1.245 17.6 85.2 O K 60 min Winter 99.110 1.510 19.0 103.3 O K 120 min Winter 99.197 1.597 19.5 109.2 O K 180 min Winter 99.140 1.540 19.2 105.3 O K 240 min Winter 99.043 1.443 18.6 98.7 O K 360 min Winter 98.846 1.246 17.6 85.2 O K 480 min Winter 98.656 1.056 16.5 72.3 O K 600 min Winter 98.485 0.885 15.6 60.5 O K 720 min Winter 98.332 0.732 14.8 50.1 O K 960 min Winter 98.078 0.478 13.4 32.7 O K 1440 min Winter 97.736 0.136 11.6 9.3 O K 2160 min Winter 97.642 0.042 9.4 2.9 O K 2880 min Winter 97.634 0.034 7.6 2.3 O K 4320 min Winter 97.625 0.025 5.6 1.7 O K 5760 min Winter 97.621 0.021 4.6 1.4 O K 7200 min Winter 97.618 0.018 3.9 1.2 O K 8640 min Winter 97.615 0.015 3.4 1.1 O K 10080 min Winter 97.614 0.014 3.1 0.9 O K

Storm Rain Flooded Time-Peak Event (mm/hr) Volume (mins) (m³)

30 min Winter 75.427 0.0 37 60 min Winter 51.110 0.0 60 120 min Winter 33.394 0.0 98 180 min Winter 25.539 0.0 136 240 min Winter 20.912 0.0 172 360 min Winter 15.794 0.0 242 480 min Winter 12.912 0.0 310 600 min Winter 11.031 0.0 376 720 min Winter 9.691 0.0 440 960 min Winter 7.889 0.0 564 1440 min Winter 5.886 0.0 788 2160 min Winter 4.376 0.0 1100 2880 min Winter 3.539 0.0 1448 4320 min Winter 2.628 0.0 2192 5760 min Winter 2.130 0.0 2856 7200 min Winter 1.810 0.0 3632 8640 min Winter 1.587 0.0 4296 10080 min Winter 1.420 0.0 5048

©1982-2020 Innovyze EDS Ltd Page 3 Unit 10, Penstraze Business ... J-1803 Truro 2.707 m/h, 3270m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Rainfall Details

Time Area Diagram

Total Area (ha) 0.360

Time (mins) Area Time (mins) Area Time (mins) Area Time (mins) Area From: To: (ha) From: To: (ha) From: To: (ha) From: To: (ha)

0 4 0.090 4 8 0.090 8 12 0.090 12 16 0.090

©1982-2020 Innovyze EDS Ltd Page 4 Unit 10, Penstraze Business ... J-1803 Truro 2.707 m/h, 3270m2 Cornwall Boscoppa Road, St Austell Date 12/04/2021 Designed by Joshua Munyard File J-1803 Soakaway Calcs, ... Checked by Innovyze Source Control 2020.1

Model Details

Storage is Online Cover Level (m) 100.000

Cellular Storage Structure

Invert Level (m) 97.600 Safety Factor 5.0 Infiltration Coefficient Base (m/hr) 2.70700 Porosity 0.95 Infiltration Coefficient Side (m/hr) 2.70700

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

0.000 72.0 72.0 1.601 0.0 129.6 1.600 72.0 129.6

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