Flood Risk Assessment

FLOOD RISK ASSESSMENT

on:

Land off Holt Road, Horsford

for:

Carl Palmer

Land off Holt Road, Horsford Flood Risk Assessment 206164

Contents Amendment Record This report has been issued and amended as follows:

Rev Description Prepared Reviewed Checked Date

P1 Preliminary Issue MJWH MEH AM 08.06.2018

Canham Consulting Ltd The Old School School Lane Thorpe St. Andrew Norwich NR7 0EP

T: 01603 430650 F: 01603 430672 [email protected] www.canhamconsulting.co.uk

Flood Risk Assessment – Land off Holt Road, Horsford June 2018 Issue P1 206164

CONTENTS 1 INTRODUCTION ...... 3 2 DEVELOPMENT DESCRIPTION & LOCATION ...... 4 2.1 TYPE OF DEVELOPMENT WITH LOCATION ...... 4 2.2 VULNERABILITY CLASSIFICATION ...... 5 2.3 SEQUENTIAL TEST ...... 5 3 SOURCES OF FLOODING ...... 6 3.1 FLOODING FROM RIVERS ...... 6 3.2 FLOODING FROM THE SEA ...... 6 3.3 FLOODING FROM THE LAND...... 7 3.4 FLOODING FROM THE GROUND ...... 8 3.5 FLOODING FROM ARTIFICIAL SOURCES ...... 8 4 CLIMATE CHANGE ...... 10 5 DETAILED DEVELOPMENT PROPOSAL ...... 11 6 FLOOD RISK MANAGEMENT MEASURES...... 12 6.1 LEVEL STRATEGY ...... 12 6.2 FOUL STRATEGY ...... 12 6.3 SURFACE WATER DRAINAGE (SUDS) ...... 12 6.3.1 OUTFALL AND WATER VOLUME ...... 12 6.3.2 SUDS OPTIONS ...... 14 6.3.3 SUDS DESIGN ...... 16 6.3.4 MAINTENANCE ...... 20 7 RESIDUAL RISKS ...... 21 7.1 LACK OF MAINTENANCE ...... 21 8 OFF SITE IMPACTS ...... 22 8.1 IMPACT OF SURFACE WATER DRAINAGE ...... 22 8.2 IMPACT OF DEVELOPMENT ON HYDROLOGICAL MORPHOLOGY ...... 22 9 SUMMARY ...... 23

Flood Risk Assessment – Land off Holt Road, Horsford June 2018 Issue P1 206164

Appendix List

Appendix A Masterplan

Appendix B Site Plan with Topographic Information

Appendix C Anglian Water Sewer Records

Appendix D Exceedance Flow Plan

Appendix E Infiltration Test Results

Appendix F MicroDrainage Calculations

Appendix G Maintenance Strategy

Figure List

Figure 1.1 Site Location Plan

Figure 3.1 Surface Water Flood Map

Figure 6.1 Infiltration test locations (indicated by the blue rectangles)

Table List

Table 2.1 Sequential Test

Table 6.1 Site Infiltration Rates

Table 6.2 SuDS Component Assessment

Table 6.3 Pollution Hazard Indices

Table 6.4 Indices Suitability Comparison

Table 6.5 Infiltration Basin Sizing Calculations

Table 6.6 Infiltration Basing Sizing Calculations [Lower Infiltration Rate]

Table 6.7 Infiltration Basin Sizing Calculations [Lower Infiltration Rate & 1-in-30 year storm event]

Table 6.8 Attenuation Basin Sizing Calculations

Table 6.9 Attenuation Crate Sizing Calculations

Flood Risk Assessment – Land off Holt Road, Horsford June 2018 Issue P1 206164

1 INTRODUCTION

Canham Consulting Ltd have been commissioned by Carl Palmer to produce a Flood Risk Assessment in support of an outline planning application for a mixed density residential development off Holt Road, Horsford. The proposed development consists of approximately 60-65 residential units. A masterplan of the development can be found in Appendix A.

The purpose of this report is to provide information on the flood risks associated with the proposed development, identify mitigation measures for the site, meet the relevant design criteria and to enable the development to proceed.

This is to be achieved by ensuring that the development is safe from flooding to the recognised standards and does not increase the risk of flooding to the development or to third parties.

This report follows the guidance set out in the National Planning Policy Framework (NPPF), the National Planning Policy Guidance (NPPG), alongside other relevant Local Authority policies and guidance notes from relevant bodies such as the Environment Agency (EA), Anglian Water, CIRIA, The SuDS Manual (C753) and Norfolk County Council’s Guidance on SuDS Design.

The following data was collected as part of this assessment:

 Anglian Water Sewer Records  Infiltration Rates

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2 DEVELOPMENT DESCRIPTION & LOCATION

2.1 Type of Development with Location

The proposed development consists of low and medium density residential development, open space and associated roads. The location of the site is shown on Figure 1.1.

Most of the site is greenfield. There is a private swimming pool and garage within the site. The site location is centred on Grid Reference TG196152.

Site Location

Figure 1.1: Site Location Plan

North of the site there are existing residential dwellings, beyond this is Church Street, further residences and Horsford All Saints Church. East of the site there are several large agricultural fields. Adjacent to the south-east of the site there is a farm. South of the site there is agricultural land, and beyond this is the Northern Distribution Road (NDR). South- west of the site there are agricultural buildings. Adjacent to the west of the site is the B1149 Holt Road and a roundabout which links to the NDR via the realigned Drayton Lane. There is agricultural land to the west of Holt Road.

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The site area is approximately 3.4ha. Most of the site is currently considered as

permeable.

2.2 Vulnerability Classification

The various types of built development are classified by national planning policy with regard to vulnerability to flood risk. NPPG Table 2 provides a detailed list of which types of development fall into the five flood risk vulnerability classifications. This list is recognised as not being exclusive, but it provides guidance on the various uses and their associated Flood Risk Vulnerability Classification.

The proposed development is residential. Residential use falls into the ‘More Vulnerable’ classification.

2.3 Sequential Test

The online flood maps indicate that the site is located within Flood Zone 1. Table 3 of the Technical Guidance to the NPPF identifies which types of development are appropriate for the various Flood Zones as shown below in Table 2.1.

Flood Risk Essential Water Highly More Less Vulnerability Infrastructure Compatible Vulnerable Vulnerable Vulnerable Classification

Zone 1     

Exception test Zone 2     required

Exception test Exception test Zone 3a    required required

Exception test

Flood Zone Classification Zone 3b     required

 Suitable for Development  Not Suitable for Development Table 2.1: Sequential Test

As the proposed site is within Flood Zone 1, the ‘More Vulnerable’ usage is considered suitable from the Sequential Test viewpoint. It is considered that the site is in a suitable location from a flood risk perspective.

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3 SOURCES OF FLOODING

As the site is shown within Flood Zone 1 on the online flood maps, the most significant source of flooding is deemed to be from surface water. However, for completeness, an analysis of all flood sources has been undertaken to fully consider the flood risk to the development and the surrounding area.

3.1 Flooding from Rivers

Fluvial flooding is caused by rivers and occurs when the river channel capacity is exceeded by the flow. Most rivers have a natural floodplain which, in built up areas, is sometimes encroached upon by development.

The online flood plain maps indicate that the site is within Flood Zone 1 and therefore at a low risk of flooding from rivers. The nearest watercourse is a stream approximately 500m north of the site.

From the information above, the risk of flooding from rivers is considered as Low.

3.2 Flooding from the Sea

Tidal flooding from the sea occurs when high tides and storm surges raise the level of tidal waters above the level of the shore or river bank. These can be sudden and severe but are dependent upon several factors. There are two ways in which the sea could potentially flood the site:

a) Open Coast – risk from the sea

The proposed development is significantly far inland, therefore, flooding from the open coast can be considered as Low.

b) Tidal Influence of Rivers

The stream outlined above is not considered to be tidally influenced at the point closest to the site’s location. The risk of river flooding from tidal influence is considered as Low.

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3.3 Flooding from the Land

Within urban areas where there are large areas of impermeable surfacing e.g. roofs, car parking and roads, it is possible for high intensity rainfall storms to not soak into the ground or enter the manmade drainage system at a quick enough rate to cope with the volume of water. Where this occurs, the excess water can flow across land and potentially cause flooding.

On a macro scale, the OS Explorer series map contours indicate the site falls roughly two meters from north-east to south-west. A 30m contour line runs across the northern edge of the site. There is a 35m contour along the southern edge of the site.

A Site Plan with topographic information (Appendix B) shows the site falls from south to north by approximately 6m. The topographic survey shows the highest point at the site is along the southern border at approximately 35.92m, and the lowest point at the site is along the northern border of the site at approximately 29.39m.

Therefore, the risk from overland flow is considered as Low to moderate.

Figure 3.1 below is taken from the gov.uk website for Long Term Flood Risk for surface water. Figure 3.1 shows the site is at a very low risk of surface water flooding for its entire area.

Figure 3.1: Surface Water Flood Map

Therefore, the risk from the land is considered as Low.

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3.4 Flooding from the Ground

In areas where the level of groundwater is high, rainfall that soaks into the ground can raise groundwater to a level where structures within the ground are at risk of flooding. Structures such as basements or detention ponds can be at risk, although this is dependent upon the ground conditions of the site.

The ground conditions from the BGS maps indicate that the site has bedrock of Wroxham Crag Formation – Sand and Gravel over superficial deposits of Sheringham Cliffs Formation – Sand and Gravel. BGS Borehole Records ref:TG11NE190 taken just west of the site went down to 2.8m and did not find ground water. A borehole just north of the site ref:TG11NE52 taken in 1942 struck water at around 12m, 49m and 70m below ground level (bgl). Borehole ref:TG11NE52 was taken approximately 70 years ago, therefore, the level of water bgl could have potentially altered significantly since the borehole was completed.

The online DEFRA Magic Maps show the site is located on a Major Aquifer (high) and a principle aquifer. The EA online maps show the site is within a Nitrate Vulnerable Zone (NVZ) Eutrophic Waters (2017 Pre-Appeals).

Therefore, the flood risk from groundwater is considered to be low.

3.5 Flooding from Artificial Sources

Infrastructure failure flooding includes that from sewers and also risks from reservoirs and canals. Sewer flooding occurs when the quantity of water flowing into the sewers exceeds the capacity of the sewer and backs up to an extent where it floods out of manholes or gullies. Alternatively and more commonly, sewers flood when a blockage occurs in a pipe. This is more likely in private sewers, but is usually less severe than flooding from larger public sewers which can cause extensive flooding due to the greater quantity of surface area which they drain.

Adopted drains; The Anglian Water sewer records included within Appendix C show there is no adopted drainage within the site. There are no surface water sewers in the vicinity of

Flood Risk Assessment – Land off Holt Road, Horsford June 2018 Issue P1 206164

the site. There is a foul public sewer to the north that runs east along Church Street. Flooding from adopted sewers is considered as Low.

Private Drainage; The site is largely undeveloped besides the few buildings onsite to the north east. These buildings are under the same ownership as Calpile (existing residential dwelling to the north) on site meaning there will be limited existing private drainage on- site. Therefore, the risk from private apparatus is considered as Low.

Flooding from Canals; There are no canals near the site. The risk is of flooding from canals is considered as Low.

Flooding from Reservoirs; There are no reservoirs near the site. The risk of flooding from reservoirs is considered as Low.

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4 CLIMATE CHANGE

Due to the location of the site, the factors for climate change, as defined by NPPF Technical Guidance, should be applied to the peak rainfall intensity. A 100-year lifespan for the development has been considered as the proposed development is residential in nature.

Climate change allowances from the National Guidance on Flood Risk Assessments has been considered for the site. It can be seen from Table 2 of the national climate change guidance that in small and urban catchments, a central level of 20% and upper end of 40% peak rainfall intensity allowance should be used to assess the range of impact. The guidance only covers up to 2115, so it has been assumed the same level of intensity increase will apply for 2118.

For the purposes of this report it is proposed that a conservative approach is considered and that a climate change factor of +40% is utilised on all drainage calculations.

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5 DETAILED DEVELOPMENT PROPOSAL

In the north of the site it is proposed that there is low density residential development. Across the middle of the site it is proposed there is medium density residential development, there is also an area of open space. In the south of the site low density residential development is proposed. In the north-west of the site there is an area set aside for surface water attenuation. All these areas are outlined on a plan in Appendix A titled ‘Potential Development Areas Plan’. The total site area is approximately 3.4ha, however, after tree protection areas, open space and potential attenuation areas are considered, the remaining developable area is approximately 2.5ha.

There is a need for low density development in some areas of the site due to the surrounding properties. At the site it is proposed there will be roughly 20-25 units per hectare, across the entire site area this works out to approximately 60-65 residential units.

There are some existing structures on the site including a small domestic swimming pool and a home gym. It is proposed these structures will remain as they are under same ownership as a property to the north and the current ownership of the proposed site area.

The Highway Authority (HA) was contacted to comment on the proposed development. The HA provided informal comment and suggested that the site should have two points of access, one of the accesses can accommodate the fourth arm of the newly constructed roundabout next to the site (as shown in Appendix A). It was also suggested that the 30mph speed limit that currently stops south of the roundabout be extended along the whole site frontage. The HA also commented that pedestrian access will need to be facilitated between the site and the existing footway at the B1149/Church Street junction. Additionally, a footway/cycleway should be provided along the whole site frontage and up to Church Street. The HA also commented that links should be provided to the Horsford RB7. The proposed development will seek to satisfy the suggestions from the HA.

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6 FLOOD RISK MANAGEMENT MEASURES

Due to the construction of additional impermeable areas, mitigation measures will be required which relate to drainage which also ties in with current requirements relating to Sustainable Drainage Systems (SuDS). It is therefore proposed that the following flood risk management measures will be undertaken as part of the design of the proposed scheme.

6.1 Level Strategy

In order to mitigate the flood risk from any overland flow, the external levels will fall away from the entrances to the buildings. This will ensure that should any drainage systems become blocked, that the flood flow paths flow away from the buildings. This is a function of the detailed design, but generally floor levels of residential buildings should be constructed 150mm above the surrounding topography. An exceedance flow plan can be seen in Appendix D.

6.2 Foul Strategy

The Anglian Water Sewer Records found within Appendix C show that an existing foul water sewer runs along Church Street, north of the site.

It is understood that a pump station will be constructed on-site. This pump station will pump foul water into the existing Anglian Water sewer, via a gravity connection to the existing sewer on Church Street.

6.3 Surface Water Drainage (SuDS)

6.3.1 Outfall and Water Volume

In identifying SuDS options it is important to understand the constraints that any site has against the preferred surface water drainage criteria of:

i) Infiltration

ii) Disposal to a watercourse

iii) Disposal to a public sewer

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Infiltration testing was undertaken, and the results can be seen in Appendix E. The coefficient of permeability at the site ranges between 1.9E-07m/s (0.000684m/h) and 4.4E- 05m/s (0.1584m/h). Figure 6.1 shows the location the infiltration tests were conducted, and Table 6.1 shows the infiltration rates that were found at these locations.

30 29

Figure 6.1: Infiltration test locations (indicated by the blue rectangles)

Infiltration Rate Pit Number Meters Per Second (m/s) Meters Per Hour (m/h) 26 1.9E-07 0.000684 27 5.1E-06 0.018 28 4.4E-05 0.1584 29 1.3E-05 0.0468 30 1.3E-06 0.00468 Table 6.1: Site Infiltration Rates

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As can be seen in Table 6.1 the infiltration rates are generally poor on site. The poor permeability appears to extend across the site.

There are no watercourses within the vicinity of the site. There are no surface water sewers within the vicinity of the site.

6.3.2 SuDS Options

The poor infiltration rates (shown in Table 6.1) will impact the suitability of certain SuDS systems on-site. From those SuDS detailed within Table 7.1 of the SuDS Manual, the following shown in Table 6.2 are considered suitable.

Design Criteria

Water Quantity Runoff Volume

Component Type Water Quality Amenity Biodiversity Suitable Reason CollectionMechanism RunPeak Rateoff Small Events Large Events Rainwater Harvesting Systems P ● ● ● Y Green Roofs S ○ ● ● ● ● N Financial constraints on the development Infiltration Systems P ● ● ● ● ● ● Y Limited suitability due to poor on-site infiltration Proprietary Treatment P ● Y Systems Filter Strips L ● ● ○ ○ Y Limited suitability due to poor on-site infiltration Filter Drains L ● ● ○ ○ Y Limited suitability due to poor on-site infiltration Swales L ● ● ● ● ● ● Y Limited suitability due to poor on-site infiltration Bio-retention Systems P ● ● ● ● ● ● Y Trees P ● ● ● ● ● Y Pervious Pavements S ● ● ● ● ○ ○ Y Attenuation Storage P ● Y Tanks Detention Basins P ● ● ● ● ● Y Ponds and Wetlands P ● ● ● ● Y

Key: P = Point, L=Lateral, S=Surface, ●=Likely Valuable Contribution, ○=Some potential contribution

Table 6.2: SuDS Component Assessment

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As infiltration has limited on-site suitability, it is possible an attenuation solution (with a restricted outfall) may be required. Infiltration will however be considered as a first preference. Further site investigation will be required to establish the extent of the area with suitable infiltration rates.

It is necessary to protect any groundwater source protection zones which may exist at or near to the site. The EA Groundwater Source Protection Zones Maps indicate that the site is not within a groundwater protection zone.

The EA maps of the area indicate that the site is located within a Principle Aquifer.

Table 26.1 of the SuDS Manual (C753) indicates that a simple index approach is suitable for assessing the risk to ground water. Table 26.2 indicates the pollution indices for types of development which are considered as residential. Table 6.3 below summarises the pollution indices for the site.

Land Use Pollution Total Metals Hydro- Hazard Suspended carbons Level Solids Residential roofs Very low 0.2 0.2 0.05 Individual property driveways, Low 0.5 0.4 0.4 residential car parks, low traffic roads (e.g. cul de sacs, homezones and general access roads) and non- residential car parking with infrequent change (e.g. schools, offices) i.e. <300 traffic movements/day Table 6.3: Pollution Hazard Indices

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Table 6.4 shows the pollution hazards at the site versus the potential treatment methods at the site.

Total Suspended Solids Metals Hydro-carbons Roof Area 0.2 0.2 0.2 Infiltration Basin 0.4 0.4 0.4 Attenuation Basin 0.5 0.5 0.6 Attenuation Crates 0.0 0.0 0.0 Filter Drain 0.6 0.7 0.8 Suitable Level of Treatment Yes Yes Yes Private Drive 0.5 0.4 0.4 Permeable Paving 0.7 0.6 0.7 Infiltration Basin 0.4 0.4 0.4 Attenuation Basin 0.5 0.5 0.6 Suitable Level of Treatment Yes Yes Yes Adoptable Road 0.5 0.4 0.4 Gully 1.0 1.0 1.0 Infiltration Basin 0.4 0.4 0.4 Attenuation Basin 0.5 0.5 0.6 Suitable Level of Treatment Yes Yes Yes Table 6.4: Indices Suitability Comparison

From the information presented above it can be seen that a range of SuDS may be incorporated in the development. There will be a number of treatments where necessary to ensure sufficient treatment of the surface water. The precise treatment and SuDS components will form part of the detailed drainage design.

6.3.3 SuDS Design

Whilst the site has poor infiltration on the most part, Pit 28 (as shown on Figure 6.1) has revealed a suitable infiltration rate. An infiltration basin has been considered for the site at the location with the highest infiltration rate and at the location set aside for surface water attenuation (poorer infiltration rate) (Appendix A). As the suitable infiltration area is not accurately known, an attenuation basin system and an attenuation crate system have also been considered for the proposed development as fall-back options.

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Tables 6.5, 6.6, 6.7 and 6.8 show summaries of the MicroDrainage calculations shown in Appendix F. These calculations are based on the areas at the site shown in Appendix A. An assumption of one third greenspace, one third roof area and one third highway has been used for the areas proposed for residential development (excluding green space area and infiltration basin area), with the roof area and highway area being used in the MicroDrainage calculations. Therefore, the impermeable area used in the MicroDrainage calculations is two thirds of the site area proposed for residential development (approximately 18,000m2). All calculations account for the 1-in-100 year flood event and include 40% climate change allowance. All MicroDrainage calculations for the site can be found in Appendix F.

Table 6.5 shows a summary of the calculations for sizing an infiltration basin on site. The infiltration rate is based on the highest infiltration rate recorded at the site. This infiltration rate can be seen in Table 6.1 as pit number 28 (0.1584m/h). Where the basin is deeper than 0.6m it will either be stepped or fenced for safety purposes. There were no issues with half-drain times for the Infiltration Basin calculations.

Infiltration Basin - Highest Infiltration Rate Basin Size Slope Depth of Basin Safety Factor Infiltration Rate 2,085.8 m2 1:3m 0.5m 5 0.1584m/h 1,784.4 m2 1:3m 0.6m 5 0.1584m/h 892.2 m2 1:3m 2.0m 5 0.1584m/h Table 6.5: Infiltration Basin Sizing Calculations

Table 6.6 shows a summary of the calculations for sizing an infiltration basin on-site using the rate for the area set aside for surface water attenuation. This infiltration rate can be seen in Table 6.1 as pit number 29. Where the basin is deeper than 0.6m it will either be stepped or fenced for safety purposes. Table 6.6 includes details of the half drain time for the Infiltration Basin with the surface water attenuation area rate calculations. For an infiltration basin in the area of the lower infiltration rate to have an appropriate half-drain time it will need to be shallow. A shallow basin takes up a lot of space on-site which reduces its suitability.

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Infiltration Basin – Lower Infiltration Rate Depth of Safety Half Drain Basin Size Slope Infiltration Rate Basin Factor Time (mins) 2,641.2 m2 1:3m 0.5m 5 0.0468m/h 1,437 2,295.5 m2 1:3m 0.6m 5 0.0468m/h 1,690 1,059.1 m2 1:3m 2.0m 5 0.0468m/h 3,425 Table 6.6: Infiltration Basin Sizing Calculations [Lower Infiltration Rate]

Table 6.7 shows a summary of the calculations for sizing an infiltration basin under the same situation as Table 6.6 during a 1-in-30 storm instead of a 1-in-100 year storm event. The 1-in-30 year storm event has been calculated under the assumption that some surface water will be stored elsewhere (subject to the detailed design) such as on the road surface. Table 6.7 includes details of the half drain time for the Infiltration Basin with the surface water attenuation area rate in a 1-in-30 year event calculations. It can be seen that for an infiltration basin of this size to have an appropriate half-drain time it will need to be shallow. A shallow basin takes up a lot of space on-site which reduces its suitability.

Infiltration Basin – Lower Infiltration Rate – 1-in-30 Year Event Depth of Safety Half Drain Basin Size Slope Infiltration Rate Basin Factor Time (mins) 2,059.2 m2 1:3m 0.5m 5 0.0468m/h 1,424 1,811.4 m2 1:3m 0.6m 5 0.0468m/h 1,651 861.0 m2 1:3m 2.0m 5 0.0468m/h 3,218 Table 6.7: Infiltration Basin Sizing Calculations [Lower Infiltration Rate & 1-in-30 year storm event]

Table 6.8 shows a summary of the calculations for sizing an attenuation basin on site. The greenfield runoff rate was calculated using to be 7.3l/s which has been used as the outfall rate for the MicroDrainage calculations (Appendix F). The greenfield runoff rate was derived using the IH24 method and is based on the QBAR. Where the basin is deeper than 0.6m, it will either be stepped or fenced for safety purposes. There were no issues with half-drain times for the Attenuation Basin calculations.

Attenuation Basin Basin Size Slope Depth of Basin Outfall Restricted to 2,772.9m2 1:3m 0.5m 7.3l/s 2,306.3m2 1:3m 0.6m 7.3l/s 938.5m2 1:3m 2.0m 7.3l/s Table 6.8: Attenuation Basin Sizing Calculations

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Table 6.9 shows a summary of the calculations for sizing an attenuation crate system on- site. The greenfield runoff rate (7.3l/s) has been used as the outfall rate for the calculations. If attenuation crates were used on-site the surface water would be treated prior to attenuation. This would likely be via a filter drain. Table 6.9 includes details of the half drain time for the attenuation crate calculations. These have been included because the half drain times exceed a 24-hour period. At the depths of 0.4m, 0.8m and 1.2m this 24- hour period is only just exceeded.

Attenuation Crates Half Drain Time Crate Area Depth of Crate Outfall Restricted to (mins) 3,600 m2 0.4m 7.3l/s 1,553 1,720 m2 0.8m 7.3l/s 1,492 1,160 m2 1.2m 7.3l/s 1,638 900 m2 1.6m 7.3l/s 1,877 Table 6.9: Attenuation Crate Sizing Calculations

The tables above demonstrate there are several options available to deal with the surface water at the site. Each method of surface water management has had calculations conducted for different depths to provide a range of options and comparisons for the site. An area has been set aside on the proposed development areas plan in Appendix A (approximately 1,526m2) to provide space for surface water attenuation. The calculations have demonstrated that each of the three options can be housed within this dedicated area. This includes the infiltration basin, despite the infiltration rate being relatively low at this location. It should be noted that the basins would likely have to be fenced off for safety reasons as only the deeper basins can fit within this dedicated surface water attenuation area. It may be possible to allocate more area for surface water attenuation to accommodate a larger basin.

As infiltration systems have been shown to be suitable at the site these will be considered as a first preference. Further site investigation will be required for the detailed design which will establish the extent of the suitable infiltration areas. In the case that infiltration is found not to be suitable on site, attenuation will be used as a fall-back option. Whilst attenuation storage systems can also be suitably located on-site, the lack of a nearby surface water sewer or watercourse means further work would need to be considered to locate an outfall prior to the implementation of an attenuation strategy. It is also considered that any issues with half-drain time for the attenuation crates could rule out this as a suitable option.

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6.3.4 Maintenance

SuDS schemes require much more maintenance than traditional drainage piped systems and as such it is imperative that a suitable maintenance regime is established to ensure that the features are maintained and function in the way they are designed to.

The exact maintenance requirements of the SuDS will depend upon the product or SuDS provided as a function of detailed design. A maintenance strategy has been completed for the site and can be seen in Appendix G.

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7 RESIDUAL RISKS

The residual risks to the development are considered as:

 Lack of maintenance

7.1 Lack of Maintenance

As discussed above, SuDS drainage systems are more susceptible to failure due to lack of maintenance. To mitigate this, the proposed SuDS methods will be maintained by the site owner or a maintenance company on their behalf.

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8 OFF SITE IMPACTS

8.1 Impact of Surface Water Drainage

The proposed surface water design optimises SuDS through the designated number of treatment trains. The introduction of a strategy to cope with the 1-in-100 year event and climate change offers an improvement to the existing scenario. Therefore, the impact of the Surface Water Drainage System is considered as positive.

8.2 Impact of Development on Hydrological Morphology

The proposed system will not impinge on the hydrological morphology of the area and therefore the site is considered as neutral.

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9 SUMMARY

The proposed development is for a mixed density residential scheme which includes areas of open space, location for surface water attenuation and an associated road network. The proposed development consists of up to 65 residential dwellings.

The proposed development is within flood zone 1 and it is considered the site is suitable for development from a flood risk perspective. The site is at a very low risk of surface water flooding.

The site will look to infiltrate its surface water using an infiltration basin. However, as most of the site is shown to have poor infiltration rates, further site investigation will be required to establish whether an infiltration system for the site is suitable. It may be that parts of the site are suitable for individual soakaways for roof water. If it is found from further testing that infiltration isn’t feasible, two attenuation methods have been demonstrated to be suitable for the site and can be considered as potential fall-back options should infiltration be found unsuitable. It should be noted that there is no nearby watercourse or surface water sewer for the site to discharge to if attenuation was used. Therefore, further consideration will need to be given to location of offsite outfall should an attenuation option be required.

Overall, it has been demonstrated that the site is not at a significant risk of flooding and that measures are available for the proposed development to manage its surface water without increasing flood risk to the surrounding area.

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APPENDIX A

Masterplan

Land Required for adopted Footpath Assumed Highway verge

Potential area for surface water attenuation

G03

H03 O/S1 T13 T11 T12 Low density Residential G04 development T08

Medium density Residential Potential Site Medium density T14 T06 development Entrance Residential Point 01 T36 Off development Roundabout Open space/ T15 T03 Amenity area T16

T34 T35 T17

G02 Medium density T32 Residential development Open space/ T31 Amenity area

T18

Potential Site Entrance There are a substantial amount of Point 02 T27 H04 trees on the site of various species, of varying sizes and in varying conditions, the T19 Arboricultural survey has been T30 incorporated into this plan and the T29 trees of low value have been removed, these will be replaced within the final development N

Notes: 1. Extent of proposed site - 2. Extent of land ownership - T28

3. Green Trees-in very good condition H06 Low density T20 4. Blue trees-in good condition Residential development 5. Orange trees in poor condition T24 Rev Description Dated

------

T23 T22 Wellington H05 Construction Ltd Wolseley House,1 Quay View Business Park Barnard Road, Lowestoft, Suffolk, NR32 2HD Tel: (01502) 587024 Fax: (01502) 589829

Client Carl Palmer

Project Title Holt Road, Horsford, Potential Residential Development

Drawing Title Potential Development Areas Plan

Drawn by Project Reference CWP N/A Approved by N/A

Scale Drawing Number Revision As Shown @A1

Date POSSIBLE DEVELOPMENT AREAS PLAN 04.03.17 SK002 N/A

10m 0 10 20 Stage Scale - 1:500@A1 Preliminary Information For Approval Tender Construction As-Built

This drawing is the copyright of Wellington Ltd and should not be Reproduced without Prior Consent Do Not Scale: All figured dimensions to be checked on site and Wellington notified of any variation.

Flood Risk Assessment – Land off Holt Road, Horsford June 2018 Issue P1 206164

APPENDIX B Site Plan with Topographic Information

Flood Risk Assessment – Land off Holt Road, Horsford June 2018 Issue P1 206164

APPENDIX C Anglian Water Sewer Records

(c) Crown copyright and database rights 2015 Ordnance Survey 100022432 Date: 29/10/15 Scale: 1:1250 Map Centre: 619679,315209 Data updated: 05/10/15 Our Ref: 162135 - 1 Wastewater Plan A2

This plan is provided by Anglian Water pursuant its obligations under the Water Industry Act 1991 sections 198 or 199. It must be used in conjunction with any Foul Sewer [email protected] Outfall search results attached. The information on this plan is based on data currently recorded but position must be regarded as approximate. Service pipes, private Surface Sewer sewers and drains are generally not shown. Users of this map are strongly advised to commission their own survey of the area shown on the plan before (Colour denotes effluent type) Land at Holt Road carrying out any works. The actual position of all apparatus MUST be established by trial holes. No liability whatsoever, including liability for negligence, is Combined Sewer accepted by Anglian Water for any error or inaccuracy or omission, including the failure to accurately record, or record at all, the location of any water main, Inlet discharge pipe, sewer or disposal main or any item of apparatus. This information is valid for the date printed. This plan is produced by Anglian Water Services Final Effluent (Colour denotes effluent type) Limited (c) Crown copyright and database rights 2015 Ordnance Survey 100022432.This map is to be used for the purposes of viewing the location of Anglian Rising Main Manhole Water plant only. Any other uses of the map data or further copies is not permitted. This notice is not intended to exclude or restrict liability for death or (Colour denotes effluent type) (Colour denotes effluent type) personal injury resulting from negligence. Private Sewer Sewage Treatment Works (Colour denotes effluent type) Decommissioned Sewer Pumping Station (Colour denotes effluent type) Manhole Reference Liquid Type Cover Level Invert Level Depth to Invert Manhole Reference Liquid Type Cover Level Invert Level Depth to Invert Manhole Reference Liquid Type Cover Level Invert Level Depth to Invert Manhole Reference Liquid Type Cover Level Invert Level Depth to Invert

5301 F - - - 5302 F 34.364 31.824 2.54 6301 F 30.017 27.987 2.03 6302 F 30.992 29.212 1.78 7301 F 27.464 24.814 2.65 7302 F 28.646 26.816 1.83 8301 F 26.934 25.384 1.55

Our Ref: 162135 - 1

Flood Risk Assessment – Land off Holt Road, Horsford June 2018 Issue P1 206164

APPENDIX D Exceedance Flow Plan

GENERAL DRAINAGE NOTES:

1. THE TOPOGRAPHICAL INFORMATION REPRODUCED ON THIS DRAWING IS SHOWN FOR CO-ORDINATION AND DESIGN PURPOSES ONLY AND TAKEN FROM THE WELLINGTON CONSTRUCTION LTD DRAWING SK001, DATED 04.03.17. LIABILITY FOR THIS INFORMATION REMAINS WITH WELLINGTON CONSTRUCTION LTD: CANHAM CONSULTING LTD CANNOT ACCEPT ANY LIABILITY FOR THE CONTENT AND ACCURACY OF THE TOPOGRAPHIC SURVEY.

2. CANHAM CONSULTING LTD MUST BE INFORMED IMMEDIATELY OF ANY ALTERATIONS / DEVIATIONS IDENTIFIED ON SITE FROM THE INFORMATION SHOWN ON THIS DRAWING.

3. IN ORDER TO MITIGATE THE FLOOD RISK FROM ANY OVERLAND FLOW, THE EXTERNAL LEVELS WILL FALL AWAY FROM THE ENTRANCES TO BUILDINGS. THIS WILL ENSURE THAT SHOULD ANY DRAINAGE SYSTEMS BECOME BLOCKED, THAT THE FLOOD FLOW PATHS FLOW AWAY FROM THE BUILDING.

LEGEND

EXCEEDANCE FLOW DIRECTION

SCALE 1:1000m 0m 10m 20m 30m 40m 50m 60m 70m 80m 90m 100m

P1 30.05.18 PRELIMINARY ISSUE MJWH MEH

rev date details by check

client project CARL PALMER LAND OFF HOLT ROAD, HORSFORD

architect title EXCEEDANCE FLOW PLAN

PRELIMINARY DRAWING: THIS DRAWING IS FOR PRELIMINARY PURPOSES ONLY AND MUST NOT BE READ AS A CCL A3 1213: CAD DRAWING NOT TO BE HAND MODIFIED OR SCALED IF IN DOUBT ASK CONSTRUCTION ISSUE. Canham Consulting Ltd The Old School School Lane Norwich drawn design checked scales date drawing number IT INDICATES DESIGN INTENT ONLY AND IS Norfolk NR7 0EP Tel: +44 (0)1603 430650 Fax: +44 (0)1603 430651 SUBJECT TO AMENDMENT DURING FINAL DESIGN Email: [email protected] www.canhamconsulting.co.uk DEVELOPMENT. MJWH MJWH MEH 1:1000@A3 30.05.18 206164-300-P1 This drawing is copyright and is not to be reproduced © without the written permission of Canham Consulting Ltd

THIS DESIGN IS PRODUCED IN ACCORDANCE WITH THE CONSTRUCTION (DESIGN AND MANAGEMENT) REGULATIONS 2015 INCORPORATING THE APPROVED CODE OF PRACTICE, REGULATIONS 2, 9 AND 11. THOSE ALTERING THE DESIGN WITHOUT THE AUTHORITY OF CANHAM CONSULTING LTD SHOULD BE AWARE THEY MAY ALSO ASSUME RESPONSIBILITY FOR THOSE DUTIES.

Flood Risk Assessment – Land off Holt Road, Horsford June 2018 Issue P1 206164

APPENDIX E Infiltration Test Results

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!""#$ %&'(') (&)&&)$0)'123"3 Results from Site Observation Run 1 Scheme: Horsford Time of Emptying of Soakaway Gravel fill Yes Project No WELC0142 (Values to be checked on chart) Voids % 44.2 Trial Pit No. 26 Depth of Trial Pit (m)= 3.05 % Full 25% Empty 50% Empty 75% Empty Length of Trial Pit (m)= 1.70 Depth of Water (m) 1.9475 1.2984 0.6492 Infiltration Rate Breadth of Trial Pit (m)= 0.50 Time (mins) 105 2052 6689 1.9E-07 m/sec No of runs 1 Pipe upstand (m) 0.000

Minutes Depth of Water (m) Depth Below E.G.L.(m) Depth to water (m) 0.0 2.60 0.45 0.453 Permeability Test Results 1.0 2.55 0.50 0.496 2.0 2.51 0.54 0.536 3.00 3.0 2.48 0.57 0.570 4.0 2.45 0.60 0.598 5.0 2.43 0.62 0.620 6.0 2.41 0.64 0.642 7.0 2.39 0.66 0.659 2.50 8.0 2.38 0.67 0.674 9.0 2.36 0.69 0.690 10.0 2.35 0.70 0.705 15.0 2.28 0.77 0.765 20.0 2.24 0.81 0.812 2.00 25.0 2.20 0.85 0.850 30.0 2.17 0.88 0.880 40.0 2.12 0.93 0.932 50.0 2.08 0.97 0.973 1.50 60.0 2.04 1.01 1.006 75.0 2.01 1.04 1.044 90.0 1.97 1.08 1.075 Depthof water (m) 105.0 1.95 1.10 1.103 120.0 1.92 1.13 1.132 1.00 180.0 1.83 1.22 1.225 240.0 1.76 1.29 1.293 300.0 1.71 1.34 1.342 360.0 1.66 1.39 1.387 480.0 1.59 1.46 1.461 0.50 600.0 1.55 1.50 1.505 720.0 1.51 1.54 1.540 900.0 1.47 1.58 1.581 1080.0 1.44 1.61 1.612 0.00 1260.0 1.41 1.64 1.641 0.0 200.0 400.0 600.0 800.0 1000.0 1200.0 1400.0 1600.0 1440.0 1.38 1.67 1.666 Time (mins)

Page 1 Results from Site Observation Run 1 Scheme: Horsford Time of Emptying of Soakaway Gravel fill Yes Project No WELC0142 (Values to be checked on chart) Voids % 44.2 Trial Pit No. 27 Depth of Trial Pit (m)= 2.50 % Full 25% Empty 50% Empty 75% Empty Length of Trial Pit (m)= 1.60 Depth of Water (m) 1.4282 0.9522 0.4761 Infiltration Rate Breadth of Trial Pit (m)= 0.50 Time (mins) 34 110 230 6.0E-06 m/sec No of runs 3 Pipe upstand (m) 0.000

Minutes Depth of Water (m) Depth Below E.G.L.(m) Depth to water (m) 0.0 1.90 0.60 0.596 Permeability Test Results 1.0 1.88 0.62 0.619 2.0 1.86 0.64 0.642 2.00 3.0 1.84 0.66 0.664 4.0 1.81 0.69 0.685 5.0 1.79 0.71 0.706 1.80 6.0 1.77 0.73 0.726 7.0 1.75 0.75 0.745 8.0 1.74 0.76 0.764 1.60 9.0 1.72 0.78 0.782 10.0 1.70 0.80 0.799 15.0 1.63 0.87 0.873 1.40 20.0 1.56 0.94 0.936 25.0 1.51 0.99 0.988 1.20 30.0 1.46 1.04 1.035 40.0 1.38 1.12 1.119 50.0 1.31 1.19 1.194 1.00 60.0 1.24 1.26 1.262 75.0 1.14 1.36 1.361 Depthof water (m) 90.0 1.05 1.45 1.447 0.80 105.0 0.98 1.52 1.525 120.0 0.90 1.60 1.599 180.0 0.65 1.85 1.852 0.60 240.0 0.44 2.06 2.059

0.40

0.20

0.00 0.0 50.0 100.0 150.0 200.0 250.0 300.0 Time (mins)

Page 1 Results from Site Observation Run 2 Scheme: Horsford Time of Emptying of Soakaway Gravel fill Yes Project WELC0142 (Values to be checked on chart) Voids % 44.2 Trial Pit No. 27 Depth of Trial Pit (m)= 2.50 % Full 25% Empty 50% Empty 75% Empty Length of Trial Pit (m)= 1.60 Depth of Water (m) 1.4499 0.9666 0.4833 Infiltration Rate Breadth of Trial Pit (m)= 0.50 Time (mins) 52 147 270 5.4E-06 m/sec No of runs 3 Pipe upstand (m) 0.000

Minutes Depth of Water (m) Depth Below E.G.L.(m) Depth to water (m) 0.0 1.93 0.57 0.567 Permeability Test Results 1.0 1.90 0.60 0.596 2.0 1.88 0.62 0.618 2.50 3.0 1.87 0.63 0.633 4.0 1.85 0.65 0.647 5.0 1.84 0.66 0.661 6.0 1.83 0.67 0.673 7.0 1.82 0.68 0.685 2.00 8.0 1.80 0.70 0.696 9.0 1.79 0.71 0.708 10.0 1.78 0.72 0.720 15.0 1.72 0.78 0.776 20.0 1.68 0.82 0.822 25.0 1.63 0.87 0.865 1.50 30.0 1.59 0.91 0.907 40.0 1.52 0.98 0.978 50.0 1.46 1.04 1.041 60.0 1.40 1.10 1.099

75.0 1.32 1.18 1.183 Depth of water(m) 90.0 1.24 1.26 1.264 1.00 105.0 1.16 1.34 1.344 120.0 1.08 1.42 1.417 180.0 0.83 1.67 1.674 240.0 0.60 1.90 1.899 300.0 0.37 2.13 2.134 360.0 0.18 2.32 2.323 0.50

0.00 0.0 50.0 100.0 150.0 200.0 250.0 300.0 350.0 400.0 Time (mins)

Page 2 Results from Site Observation Run 3 Scheme: Horsford Time of Emptying of Soakaway Gravel fill Yes Project WELC0142 (Values to be checked on chart) Voids % 44.2 Trial Pit No. 27 Depth of Trial Pit (m)= 2.50 % Full 25% Empty 50% Empty 75% Empty Length of Trial Pit (m)= 1.60 Depth of Water (m) 1.4014 0.9343 0.4671 Infiltration Rate Mean Breadth of Trial Pit (m)= 0.50 Time (mins) 69 183 297 5.1E-06 5.5E-06 m/sec No of runs 3 Pipe upstand (m) 0.000

Minutes Depth of Water (m) Depth Below E.G.L.(m) Depth to water (m) 0.0 1.87 0.63 0.632 Permeability Test Results 1.0 1.85 0.65 0.648 2.0 1.84 0.66 0.662 2.00 3.0 1.82 0.68 0.677 4.0 1.81 0.69 0.687 1.80 5.0 1.80 0.70 0.697 6.0 1.79 0.71 0.707

7.0 1.78 0.72 0.717 1.60 8.0 1.77 0.73 0.726 9.0 1.76 0.74 0.735 10.0 1.76 0.74 0.744 1.40 15.0 1.72 0.78 0.784 20.0 1.68 0.82 0.819 25.0 1.65 0.85 0.852 1.20 30.0 1.62 0.88 0.884 40.0 1.55 0.95 0.945 50.0 1.50 1.00 1.003 1.00 60.0 1.44 1.06 1.056

75.0 1.37 1.13 1.129 Depth of water(m) 90.0 1.30 1.20 1.197 0.80 105.0 1.24 1.26 1.264 120.0 1.18 1.32 1.325 0.60 180.0 0.95 1.55 1.552 240.0 0.72 1.78 1.784 300.0 0.45 2.05 2.048 0.40

0.20

0.00 0.0 50.0 100.0 150.0 200.0 250.0 300.0 350.0 Time (mins)

Page 3 Results from Site Observation Run 1 Scheme: Horsford Time of Emptying of Soakaway Gravel fill Yes Project No WELC0142 (Values to be checked on chart) Voids % 44.2 Trial Pit No. 28 Depth of Trial Pit (m)= 2.10 % Full 25% Empty 50% Empty 75% Empty Length of Trial Pit (m)= 1.60 Depth of Water (m) 1.0925 0.7283 0.3642 Infiltration Rate Breadth of Trial Pit (m)= 0.50 Time (mins) 2 6 14 9.3E-05 m/sec No of runs 3 Pipe upstand (m) 0.000

Minutes Depth of Water (m) Depth Below E.G.L.(m) Depth to water (m) 0.0 1.46 0.64 0.643 Permeability Test Results 1.0 1.27 0.83 0.827 2.0 1.11 0.99 0.992 1.60 3.0 0.99 1.11 1.110 4.0 0.89 1.21 1.206 5.0 0.82 1.28 1.283 6.0 0.74 1.36 1.356 1.40 7.0 0.68 1.42 1.415 8.0 0.62 1.48 1.480 9.0 0.57 1.53 1.527 1.20 10.0 0.53 1.57 1.573 15.0 0.33 1.77 1.774 20.0 0.15 1.95 1.946 25.0 0.03 2.07 2.073 1.00

0.80

Depthof water (m) 0.60

0.40

0.20

0.00 0.0 5.0 10.0 15.0 20.0 25.0 30.0 Time (mins)

Page 1 Results from Site Observation Run 2 Scheme: Horsford Time of Emptying of Soakaway Gravel fill Yes Project WELC0142 (Values to be checked on chart) Voids % 44.2 Trial Pit No. 28 Depth of Trial Pit (m)= 2.10 % Full 25% Empty 50% Empty 75% Empty Length of Trial Pit (m)= 1.60 Depth of Water (m) 1.0985 0.7324 0.3662 Infiltration Rate Breadth of Trial Pit (m)= 0.50 Time (mins) 3 9 22 5.7E-05 m/sec No of runs 3 Pipe upstand (m) 0.000

Minutes Depth of Water (m) Depth Below E.G.L.(m) Depth to water (m) 0.0 1.46 0.64 0.635 Permeability Test Results 1.0 1.28 0.82 0.816 2.0 1.17 0.93 0.930 1.60 3.0 1.08 1.02 1.021 4.0 1.01 1.09 1.093 5.0 0.95 1.15 1.152 1.40 6.0 0.89 1.21 1.207 7.0 0.84 1.26 1.259 8.0 0.79 1.31 1.307 9.0 0.75 1.35 1.351 1.20 10.0 0.71 1.39 1.391 15.0 0.54 1.56 1.565 20.0 0.41 1.69 1.688 1.00 25.0 0.31 1.79 1.793 30.0 0.20 1.90 1.899 40.0 0.03 2.07 2.072 0.80

Depth of water(m)

0.60

0.40

0.20

0.00 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 Time (mins)

Page 2 Results from Site Observation Run 3 Scheme: Horsford Time of Emptying of Soakaway Gravel fill Yes Project WELC0142 (Values to be checked on chart) Voids % 44.2 Trial Pit No. 28 Depth of Trial Pit (m)= 2.10 % Full 25% Empty 50% Empty 75% Empty Length of Trial Pit (m)= 1.60 Depth of Water (m) 0.8486 0.5658 0.2829 Infiltration Rate Mean Breadth of Trial Pit (m)= 0.50 Time (mins) 4 13 28 4.4E-05 5.9E-05 m/sec No of runs 3 Pipe upstand (m) 0.000

Minutes Depth of Water (m) Depth Below E.G.L.(m) Depth to water (m) 0.0 1.13 0.97 0.969 Permeability Test Results 1.0 1.05 1.05 1.055 2.0 0.97 1.13 1.126 1.20 3.0 0.91 1.19 1.186 4.0 0.86 1.24 1.238 5.0 0.81 1.29 1.286 6.0 0.77 1.33 1.327 1.00 7.0 0.73 1.37 1.365 8.0 0.70 1.40 1.401 9.0 0.67 1.43 1.433 10.0 0.64 1.46 1.463 15.0 0.51 1.59 1.592 0.80 20.0 0.41 1.69 1.689 25.0 0.33 1.77 1.772 30.0 0.25 1.85 1.846 40.0 0.12 1.98 1.978 50.0 0.01 2.09 2.091 0.60

Depth of water(m)

0.40

0.20

0.00 0.0 10.0 20.0 30.0 40.0 50.0 60.0 Time (mins)

Page 3 Results from Site Observation Run 1 Scheme: Horsford Time of Emptying of Soakaway Gravel fill Yes Project No WELC0142 (Values to be checked on chart) Voids % 44.2 Trial Pit No. 29 Depth of Trial Pit (m)= 2.00 % Full 25% Empty 50% Empty 75% Empty Length of Trial Pit (m)= 1.80 Depth of Water (m) 0.8654 0.5769 0.2885 Infiltration Rate Breadth of Trial Pit (m)= 0.50 Time (mins) 7 33 82 1.4E-05 m/sec No of runs 3 Pipe upstand (m) 0.000

Minutes Depth of Water (m) Depth Below E.G.L.(m) Depth to water (m) 0.0 1.15 0.85 0.846 Permeability Test Results 1.0 1.09 0.91 0.905 2.0 1.04 0.96 0.956 1.40 3.0 1.00 1.00 1.003 4.0 0.96 1.04 1.042 5.0 0.92 1.08 1.076 6.0 0.90 1.10 1.102 1.20 7.0 0.87 1.13 1.125 8.0 0.85 1.15 1.151 9.0 0.83 1.17 1.167 10.0 0.82 1.18 1.183 1.00 15.0 0.75 1.25 1.254 20.0 0.69 1.31 1.307 25.0 0.64 1.36 1.355 30.0 0.60 1.40 1.401 0.80 40.0 0.52 1.48 1.479 50.0 0.45 1.55 1.545 60.0 0.40 1.60 1.603 75.0 0.32 1.68 1.678 0.60 90.0 0.25 1.75 1.745 Depthof water (m) 105.0 0.21 1.79 1.792 120.0 0.16 1.84 1.843 0.40

0.20

0.00 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 Time (mins)

Page 1 Results from Site Observation Run 2 Scheme: Horsford Time of Emptying of Soakaway Gravel fill Yes Project WELC0142 (Values to be checked on chart) Voids % 44.2 Trial Pit No. 29 Depth of Trial Pit (m)= 2.00 % Full 25% Empty 50% Empty 75% Empty Length of Trial Pit (m)= 1.80 Depth of Water (m) 0.8206 0.5471 0.2735 Infiltration Rate Breadth of Trial Pit (m)= 0.50 Time (mins) 12 41 84 1.5E-05 m/sec No of runs 3 Pipe upstand (m) 0.000

Minutes Depth of Water (m) Depth Below E.G.L.(m) Depth to water (m) 0.0 1.09 0.91 0.906 Permeability Test Results 1.0 1.06 0.94 0.941 2.0 1.03 0.97 0.972 1.20 3.0 1.00 1.00 1.000 4.0 0.98 1.02 1.024 5.0 0.95 1.05 1.048 6.0 0.93 1.07 1.070 1.00 7.0 0.90 1.10 1.099 8.0 0.88 1.12 1.115 9.0 0.87 1.13 1.132 10.0 0.85 1.15 1.148 15.0 0.78 1.22 1.218 0.80 20.0 0.73 1.27 1.269 25.0 0.68 1.32 1.318 30.0 0.64 1.36 1.365 40.0 0.55 1.45 1.446 50.0 0.48 1.52 1.524 0.60 60.0 0.41 1.59 1.592

75.0 0.32 1.68 1.682 Depth of water(m) 90.0 0.25 1.75 1.754 105.0 0.18 1.82 1.821 120.0 0.12 1.88 1.879 0.40

0.20

0.00 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 Time (mins)

Page 2 Results from Site Observation Run 3 Scheme: Horsford Time of Emptying of Soakaway Gravel fill Yes Project WELC0142 (Values to be checked on chart) Voids % 44.2 Trial Pit No. 29 Depth of Trial Pit (m)= 2.00 % Full 25% Empty 50% Empty 75% Empty Length of Trial Pit (m)= 1.80 Depth of Water (m) 0.8237 0.5492 0.2746 Infiltration Rate Mean Breadth of Trial Pit (m)= 0.50 Time (mins) 15 46 96 1.3E-05 1.4E-05 m/sec No of runs 3 Pipe upstand (m) 0.000

Minutes Depth of Water (m) Depth Below E.G.L.(m) Depth to water (m) 0.0 1.10 0.90 0.902 Permeability Test Results 1.0 1.07 0.93 0.933 2.0 1.04 0.96 0.958 1.20 3.0 1.02 0.98 0.980 4.0 1.00 1.00 1.000 5.0 0.98 1.02 1.020 6.0 0.96 1.04 1.039 1.00 7.0 0.94 1.06 1.059 8.0 0.92 1.08 1.078 9.0 0.91 1.09 1.095 10.0 0.88 1.12 1.119 15.0 0.82 1.18 1.182 0.80 20.0 0.77 1.23 1.235 25.0 0.72 1.28 1.280 30.0 0.68 1.32 1.322 40.0 0.59 1.41 1.406 50.0 0.52 1.48 1.476 0.60 60.0 0.46 1.54 1.545

75.0 0.37 1.63 1.628 Depth of water(m) 90.0 0.30 1.70 1.703 105.0 0.24 1.76 1.765 0.40 120.0 0.18 1.83 1.825

0.20

0.00 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 Time (mins)

Page 3 Results from Site Observation Run 1 Scheme: Horsford Time of Emptying of Soakaway Gravel fill Yes Project No WELC0142 (Values to be checked on chart) Voids % 44.2 Trial Pit No. 30 Depth of Trial Pit (m)= 3.20 % Full 25% Empty 50% Empty 75% Empty Length of Trial Pit (m)= 1.70 Depth of Water (m) 2.0498 1.3666 0.6833 Infiltration Rate Breadth of Trial Pit (m)= 0.50 Time (mins) 150 438 919 1.6E-06 m/sec No of runs 3 Pipe upstand (m) 0.000

Minutes Depth of Water (m) Depth Below E.G.L.(m) Depth to water (m) 0.0 2.73 0.47 0.467 Permeability Test Results 1.0 2.73 0.47 0.474 2.0 2.72 0.48 0.480 3.00 3.0 2.72 0.48 0.485 4.0 2.71 0.49 0.491 5.0 2.70 0.50 0.496 6.0 2.70 0.50 0.501 7.0 2.69 0.51 0.506 2.50 8.0 2.69 0.51 0.514 9.0 2.68 0.52 0.520 10.0 2.68 0.52 0.525 15.0 2.64 0.56 0.558 20.0 2.61 0.59 0.590 2.00 25.0 2.58 0.62 0.622 30.0 2.55 0.65 0.653 40.0 2.49 0.71 0.709 50.0 2.45 0.75 0.745 1.50 60.0 2.41 0.79 0.793 75.0 2.33 0.87 0.869 90.0 2.27 0.93 0.933 Depthof water (m) 105.0 2.21 0.99 0.992 120.0 2.15 1.05 1.049 1.00 180.0 1.95 1.25 1.250 240.0 1.78 1.42 1.421 300.0 1.64 1.56 1.562 360.0 1.51 1.69 1.690 480.0 1.29 1.91 1.911 0.50 600.0 1.10 2.10 2.097 720.0 0.94 2.26 2.262 900.0 0.71 2.49 2.494 1080.0 0.49 2.71 2.705 0.00 0.0 200.0 400.0 600.0 800.0 1000.0 1200.0 Time (mins)

Page 1 Results from Site Observation Run 2 Scheme: Horsford Time of Emptying of Soakaway Gravel fill Yes Project WELC0142 (Values to be checked on chart) Voids % 44.2 Trial Pit No. 30 Depth of Trial Pit (m)= 3.20 % Full 25% Empty 50% Empty 75% Empty Length of Trial Pit (m)= 1.70 Depth of Water (m) 2.0489 1.3660 0.6830 Infiltration Rate Breadth of Trial Pit (m)= 0.50 Time (mins) 178 541 1124 1.3E-06 m/sec No of runs 3 Pipe upstand (m) 0.000

Minutes Depth of Water (m) Depth Below E.G.L.(m) Depth to water (m) 0.0 2.73 0.47 0.468 Permeability Test Results 1.0 2.72 0.48 0.475 2.0 2.72 0.48 0.483 3.00 3.0 2.71 0.49 0.490 4.0 2.70 0.50 0.496 5.0 2.70 0.50 0.502 6.0 2.69 0.51 0.509 2.50 7.0 2.69 0.51 0.514 8.0 2.68 0.52 0.520 9.0 2.67 0.53 0.525 10.0 2.67 0.53 0.531 15.0 2.63 0.57 0.572 2.00 20.0 2.60 0.60 0.603 25.0 2.57 0.63 0.631 30.0 2.54 0.66 0.657 40.0 2.50 0.70 0.704 50.0 2.45 0.75 0.745 1.50 60.0 2.42 0.78 0.785

75.0 2.36 0.84 0.842 Depth of water(m) 90.0 2.30 0.90 0.895 105.0 2.26 0.94 0.945 120.0 2.21 0.99 0.991 1.00 180.0 2.04 1.16 1.158 240.0 1.90 1.30 1.302 300.0 1.77 1.43 1.430 360.0 1.65 1.55 1.546 0.50 480.0 1.45 1.75 1.746 600.0 1.28 1.92 1.918 720.0 1.13 2.07 2.072 900.0 0.92 2.28 2.277 1080.0 0.73 2.47 2.472 0.00 1260.0 0.54 2.66 2.657 0.0 200.0 400.0 600.0 800.0 1000.0 1200.0 1400.0 Time (mins)

Page 2 Results from Site Observation Run 3 Scheme: Horsford Time of Emptying of Soakaway Gravel fill Yes Project WELC0142 (Values to be checked on chart) Voids % 44.2 Trial Pit No. 30 Depth of Trial Pit (m)= 3.20 % Full 25% Empty 50% Empty 75% Empty Length of Trial Pit (m)= 1.70 Depth of Water (m) 2.0102 1.3401 0.6701 Infiltration Rate Mean Breadth of Trial Pit (m)= 0.50 Time (mins) 170 514 1051 1.4E-06 1.4E-06 m/sec No of runs 3 Pipe upstand (m) 0.000

Minutes Depth of Water (m) Depth Below E.G.L.(m) Depth to water (m) 0.0 2.68 0.52 0.520 Permeability Test Results 1.0 2.67 0.53 0.530 2.0 2.66 0.54 0.541 3.00 3.0 2.65 0.55 0.550 4.0 2.64 0.56 0.560 5.0 2.63 0.57 0.570 6.0 2.62 0.58 0.578 2.50 7.0 2.61 0.59 0.587 8.0 2.61 0.59 0.595 9.0 2.60 0.60 0.603 10.0 2.59 0.61 0.610 15.0 2.56 0.64 0.642 2.00 20.0 2.53 0.67 0.671 25.0 2.50 0.70 0.697 30.0 2.48 0.72 0.722 40.0 2.43 0.77 0.769 50.0 2.39 0.81 0.811 1.50 60.0 2.35 0.85 0.851

75.0 2.29 0.91 0.907 Depth of water(m) 90.0 2.24 0.96 0.959 105.0 2.19 1.01 1.007 1.00 120.0 2.15 1.05 1.053 180.0 1.98 1.22 1.216 240.0 1.84 1.36 1.359 300.0 1.71 1.49 1.487 360.0 1.60 1.60 1.603 0.50 480.0 1.39 1.81 1.810 600.0 1.22 1.98 1.984 720.0 1.06 2.14 2.141 900.0 0.84 2.36 2.359 1080.0 0.64 2.56 2.563 0.00 1260.0 0.46 2.74 2.741 0.0 200.0 400.0 600.0 800.0 1000.0 1200.0 1400.0 1600.0 1440.0 0.32 2.89 2.885 Time (mins)

Page 3

Flood Risk Assessment – Land off Holt Road, Horsford June 2018 Issue P1 206164

APPENDIX F MicroDrainage Calculations

Canham Consulting Ltd Page 1 The Old School Thorpe St Andrew Norwich NR7 0EP Date 05/06/2018 11:25 AM Designed by morganharris File Attenuation Basin Sizin... Checked by XP Solutions Source Control 2016.1.1

IH 124 Mean Annual Flood

Input

Return Period (years) 100 Soil 0.450 Area (ha) 50.000 Urban 0.000 SAAR (mm) 650 Region Number Region 5

Results l/s

QBAR Rural 201.4 QBAR Urban 201.4

Q100 years 717.0

Q1 year 175.2 Q2 years 180.0 Q5 years 259.8 Q10 years 333.3 Q20 years 421.1 Q25 years 455.6 Q30 years 483.9 Q50 years 572.4 Q100 years 717.0 Q200 years 843.9 Q250 years 884.2 Q1000 years 1160.1

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Basin Norwich NR7 0EP 0.5m Deep Date 08/06/2018 09:26 AM Designed by MJWH File Attenuation Basin Sizing Checked by XP0.5 Solutionsm ... Source Control 2016.1.1

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

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

15 min Summer 9.676 0.176 7.3 449.2 O K 30 min Summer 9.729 0.229 7.3 587.5 Flood Risk 60 min Summer 9.783 0.283 7.3 729.4 Flood Risk 120 min Summer 9.836 0.336 7.3 869.7 Flood Risk 180 min Summer 9.864 0.364 7.3 946.6 Flood Risk 240 min Summer 9.883 0.383 7.3 996.3 Flood Risk 360 min Summer 9.905 0.405 7.3 1058.0 Flood Risk 480 min Summer 9.920 0.420 7.3 1096.5 Flood Risk 600 min Summer 9.928 0.428 7.3 1120.2 Flood Risk 720 min Summer 9.933 0.433 7.3 1134.4 Flood Risk 960 min Summer 9.937 0.437 7.3 1144.7 Flood Risk 1440 min Summer 9.932 0.432 7.3 1130.5 Flood Risk 2160 min Summer 9.920 0.420 7.3 1098.0 Flood Risk 2880 min Summer 9.906 0.406 7.3 1058.9 Flood Risk 4320 min Summer 9.871 0.371 7.3 964.8 Flood Risk 5760 min Summer 9.835 0.335 7.3 867.3 Flood Risk 7200 min Summer 9.801 0.301 7.3 776.8 Flood Risk 8640 min Summer 9.770 0.270 7.3 694.5 Flood Risk 10080 min Summer 9.742 0.242 7.3 621.8 Flood Risk 15 min Winter 9.697 0.197 7.3 503.4 O K 30 min Winter 9.756 0.256 7.3 658.6 Flood Risk 60 min Winter 9.817 0.317 7.3 818.2 Flood Risk 120 min Winter 9.876 0.376 7.3 977.3 Flood Risk 180 min Winter 9.908 0.408 7.3 1065.1 Flood Risk 240 min Winter 9.929 0.429 7.3 1121.3 Flood Risk

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

15 min Summer 134.372 0.0 339.5 19 30 min Summer 88.266 0.0 451.3 34 60 min Summer 55.250 0.0 670.0 64 120 min Summer 33.426 0.0 810.4 124 180 min Summer 24.587 0.0 889.5 184 240 min Summer 19.657 0.0 941.7 242 360 min Summer 14.271 0.0 1009.0 362 480 min Summer 11.374 0.0 1051.7 482 600 min Summer 9.532 0.0 1076.6 602 720 min Summer 8.247 0.0 1087.7 722 960 min Summer 6.558 0.0 1077.5 960 1440 min Summer 4.740 0.0 1010.6 1256 2160 min Summer 3.420 0.0 1586.7 1624 2880 min Summer 2.711 0.0 1661.3 2020 4320 min Summer 1.951 0.0 1736.0 2848 5760 min Summer 1.543 0.0 1972.9 3632 7200 min Summer 1.286 0.0 2051.4 4392 8640 min Summer 1.107 0.0 2111.9 5104 10080 min Summer 0.976 0.0 2153.1 5848 15 min Winter 134.372 0.0 384.0 19 30 min Winter 88.266 0.0 501.8 33 60 min Winter 55.250 0.0 751.6 64 120 min Winter 33.426 0.0 903.5 122 180 min Winter 24.587 0.0 985.5 180 240 min Winter 19.657 0.0 1037.7 240

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Basin Norwich NR7 0EP 0.5m Deep Date 08/06/2018 09:26 AM Designed by MJWH File Attenuation Basin Sizing Checked by XP0.5 Solutionsm ... Source Control 2016.1.1

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

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

360 min Winter 9.954 0.454 7.3 1191.3 Flood Risk 480 min Winter 9.971 0.471 7.3 1236.2 Flood Risk 600 min Winter 9.981 0.481 7.3 1265.0 Flood Risk 720 min Winter 9.988 0.488 7.3 1283.3 Flood Risk 960 min Winter 9.994 0.494 7.3 1300.2 Flood Risk 1440 min Winter 9.990 0.490 7.3 1290.8 Flood Risk 2160 min Winter 9.972 0.472 7.3 1241.1 Flood Risk 2880 min Winter 9.953 0.453 7.3 1188.4 Flood Risk 4320 min Winter 9.907 0.407 7.3 1061.6 Flood Risk 5760 min Winter 9.852 0.352 7.3 912.7 Flood Risk 7200 min Winter 9.799 0.299 7.3 772.7 Flood Risk 8640 min Winter 9.753 0.253 7.3 650.2 Flood Risk 10080 min Winter 9.714 0.214 7.3 546.5 Flood Risk

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

360 min Winter 14.271 0.0 1098.9 358 480 min Winter 11.374 0.0 1127.9 474 600 min Winter 9.532 0.0 1133.5 590 720 min Winter 8.247 0.0 1123.9 704 960 min Winter 6.558 0.0 1095.5 932 1440 min Winter 4.740 0.0 1037.4 1358 2160 min Winter 3.420 0.0 1771.2 1708 2880 min Winter 2.711 0.0 1847.7 2164 4320 min Winter 1.951 0.0 1879.0 3108 5760 min Winter 1.543 0.0 2211.1 3928 7200 min Winter 1.286 0.0 2300.3 4688 8640 min Winter 1.107 0.0 2370.0 5440 10080 min Winter 0.976 0.0 2419.3 6144

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Basin Norwich NR7 0EP 0.5m Deep Date 08/06/2018 09:26 AM Designed by MJWH File Attenuation Basin Sizing Checked by XP0.5 Solutionsm ... Source Control 2016.1.1

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) 19.500 Shortest Storm (mins) 15 Ratio R 0.400 Longest Storm (mins) 10080 Summer Storms Yes Climate Change % +40

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Basin Norwich NR7 0EP 0.5m Deep Date 08/06/2018 09:26 AM Designed by MJWH File Attenuation Basin Sizing Checked by XP0.5 Solutionsm ... Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Tank or Pond Structure

Invert Level (m) 9.500

Depth (m) Area (m²) Depth (m) Area (m²)

0.000 2500.0 0.500 2772.9

Hydro-Brake® Optimum Outflow Control

Unit Reference MD-SHE-0133-7300-0500-7300 Design Head (m) 0.500 Design Flow (l/s) 7.3 Flush-Flo™ Calculated Objective Minimise upstream storage Application Surface Sump Available Yes Diameter (mm) 133 Invert Level (m) 9.500 Minimum Outlet Pipe Diameter (mm) 150 Suggested Manhole Diameter (mm) 1200

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

Design Point (Calculated) 0.500 7.3 Kick-Flo® 0.384 6.5 Flush-Flo™ 0.202 7.3 Mean Flow over Head Range - 5.9

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) Depth (m) Flow (l/s)

0.100 4.8 0.800 9.1 2.000 14.0 4.000 19.5 7.000 25.6 0.200 7.3 1.000 10.1 2.200 14.7 4.500 20.7 7.500 26.5 0.300 7.1 1.200 11.0 2.400 15.3 5.000 21.8 8.000 27.4 0.400 6.6 1.400 11.8 2.600 15.9 5.500 22.7 8.500 28.3 0.500 7.3 1.600 12.6 3.000 17.0 6.000 23.7 9.000 29.1 0.600 7.9 1.800 13.3 3.500 18.3 6.500 24.7 9.500 29.9

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Basin Norwich NR7 0EP 0.6m Deep Date 08/06/2018 09:37 AM Designed by MJWH File Attenuation Basin Sizing Checked by XP0.6 Solutionsm ... Source Control 2016.1.1

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

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

15 min Summer 9.618 0.218 7.3 448.9 O K 30 min Summer 9.683 0.283 7.3 587.1 O K 60 min Summer 9.748 0.348 7.3 728.8 Flood Risk 120 min Summer 9.812 0.412 7.3 868.6 Flood Risk 180 min Summer 9.846 0.446 7.3 945.3 Flood Risk 240 min Summer 9.868 0.468 7.3 994.2 Flood Risk 360 min Summer 9.895 0.495 7.3 1053.8 Flood Risk 480 min Summer 9.911 0.511 7.3 1090.4 Flood Risk 600 min Summer 9.921 0.521 7.3 1112.4 Flood Risk 720 min Summer 9.926 0.526 7.3 1125.0 Flood Risk 960 min Summer 9.929 0.529 7.3 1132.3 Flood Risk 1440 min Summer 9.921 0.521 7.3 1113.2 Flood Risk 2160 min Summer 9.904 0.504 7.3 1074.8 Flood Risk 2880 min Summer 9.885 0.485 7.3 1031.3 Flood Risk 4320 min Summer 9.841 0.441 7.3 933.5 Flood Risk 5760 min Summer 9.794 0.394 7.3 829.5 Flood Risk 7200 min Summer 9.751 0.351 7.3 735.7 Flood Risk 8640 min Summer 9.712 0.312 7.3 651.0 Flood Risk 10080 min Summer 9.677 0.277 7.3 576.1 O K 15 min Winter 9.643 0.243 7.3 503.1 O K 30 min Winter 9.716 0.316 7.3 658.3 Flood Risk 60 min Winter 9.789 0.389 7.3 817.6 Flood Risk 120 min Winter 9.860 0.460 7.3 976.4 Flood Risk 180 min Winter 9.899 0.499 7.3 1063.1 Flood Risk 240 min Winter 9.923 0.523 7.3 1118.5 Flood Risk

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

15 min Summer 134.372 0.0 366.7 19 30 min Summer 88.266 0.0 480.0 34 60 min Summer 55.250 0.0 691.3 64 120 min Summer 33.426 0.0 834.2 124 180 min Summer 24.587 0.0 914.5 184 240 min Summer 19.657 0.0 967.7 242 360 min Summer 14.271 0.0 1036.2 362 480 min Summer 11.374 0.0 1078.0 482 600 min Summer 9.532 0.0 1099.5 602 720 min Summer 8.247 0.0 1104.6 722 960 min Summer 6.558 0.0 1082.0 960 1440 min Summer 4.740 0.0 1019.2 1256 2160 min Summer 3.420 0.0 1608.9 1624 2880 min Summer 2.711 0.0 1687.8 2020 4320 min Summer 1.951 0.0 1769.9 2852 5760 min Summer 1.543 0.0 1982.0 3632 7200 min Summer 1.286 0.0 2062.0 4392 8640 min Summer 1.107 0.0 2125.1 5112 10080 min Summer 0.976 0.0 2170.7 5848 15 min Winter 134.372 0.0 412.0 19 30 min Winter 88.266 0.0 529.8 33 60 min Winter 55.250 0.0 774.2 64 120 min Winter 33.426 0.0 928.4 122 180 min Winter 24.587 0.0 1012.1 180 240 min Winter 19.657 0.0 1064.5 240

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Basin Norwich NR7 0EP 0.6m Deep Date 08/06/2018 09:37 AM Designed by MJWH File Attenuation Basin Sizing Checked by XP0.6 Solutionsm ... Source Control 2016.1.1

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

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

360 min Winter 9.953 0.553 7.3 1186.9 Flood Risk 480 min Winter 9.972 0.572 7.3 1230.3 Flood Risk 600 min Winter 9.984 0.584 7.3 1257.7 Flood Risk 720 min Winter 9.992 0.592 7.3 1274.6 Flood Risk 960 min Winter 9.998 0.598 7.3 1289.0 Flood Risk 1440 min Winter 9.992 0.592 7.3 1275.0 Flood Risk 2160 min Winter 9.968 0.568 7.3 1219.7 Flood Risk 2880 min Winter 9.943 0.543 7.3 1162.3 Flood Risk 4320 min Winter 9.884 0.484 7.3 1029.4 Flood Risk 5760 min Winter 9.815 0.415 7.3 875.8 Flood Risk 7200 min Winter 9.749 0.349 7.3 729.9 Flood Risk 8640 min Winter 9.690 0.290 7.3 603.3 O K 10080 min Winter 9.640 0.240 7.3 495.9 O K

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

360 min Winter 14.271 0.0 1122.3 356 480 min Winter 11.374 0.0 1142.4 474 600 min Winter 9.532 0.0 1137.0 590 720 min Winter 8.247 0.0 1124.4 704 960 min Winter 6.558 0.0 1098.1 932 1440 min Winter 4.740 0.0 1046.5 1358 2160 min Winter 3.420 0.0 1796.4 1708 2880 min Winter 2.711 0.0 1878.2 2164 4320 min Winter 1.951 0.0 1911.0 3108 5760 min Winter 1.543 0.0 2220.7 3968 7200 min Winter 1.286 0.0 2311.3 4688 8640 min Winter 1.107 0.0 2383.5 5448 10080 min Winter 0.976 0.0 2437.3 6144

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Basin Norwich NR7 0EP 0.6m Deep Date 08/06/2018 09:37 AM Designed by MJWH File Attenuation Basin Sizing Checked by XP0.6 Solutionsm ... Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Basin Norwich NR7 0EP 0.6m Deep Date 08/06/2018 09:37 AM Designed by MJWH File Attenuation Basin Sizing Checked by XP0.6 Solutionsm ... Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Tank or Pond Structure

Invert Level (m) 9.400

Depth (m) Area (m²) Depth (m) Area (m²)

0.000 2010.0 0.600 2306.3

Hydro-Brake® Optimum Outflow Control

Unit Reference MD-SHE-0132-7300-0600-7300 Design Head (m) 0.600 Design Flow (l/s) 7.3 Flush-Flo™ Calculated Objective Minimise upstream storage Application Surface Sump Available Yes Diameter (mm) 132 Invert Level (m) 9.400 Minimum Outlet Pipe Diameter (mm) 150 Suggested Manhole Diameter (mm) 1200

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

Design Point (Calculated) 0.600 7.3 Kick-Flo® 0.443 6.3 Flush-Flo™ 0.213 7.3 Mean Flow over Head Range - 6.1

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 4.7 0.800 8.3 2.000 12.9 4.000 17.9 7.000 23.4 0.200 7.3 1.000 9.3 2.200 13.5 4.500 19.0 7.500 24.2 0.300 7.2 1.200 10.1 2.400 14.0 5.000 19.9 8.000 25.0 0.400 6.8 1.400 10.9 2.600 14.6 5.500 20.9 8.500 25.8 0.500 6.7 1.600 11.6 3.000 15.6 6.000 21.8 9.000 26.6 0.600 7.3 1.800 12.2 3.500 16.8 6.500 22.5 9.500 27.3

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Basin Norwich NR7 0EP 2.0m Deep Date 08/06/2018 09:37 AM Designed by MJWH File Attenuation Basin Sizing 2m Checked by XPDe. Solutions.. Source Control 2016.1.1

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

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

15 min Summer 8.892 0.892 6.6 448.2 O K 30 min Summer 9.108 1.108 6.6 586.3 O K 60 min Summer 9.308 1.308 6.6 726.6 O K 120 min Summer 9.489 1.489 6.6 862.7 O K 180 min Summer 9.580 1.580 6.6 935.0 O K 240 min Summer 9.635 1.635 6.6 979.6 O K 360 min Summer 9.698 1.698 6.8 1031.8 O K 480 min Summer 9.733 1.733 6.8 1061.7 Flood Risk 600 min Summer 9.752 1.752 6.9 1077.5 Flood Risk 720 min Summer 9.759 1.759 6.9 1084.3 Flood Risk 960 min Summer 9.756 1.756 6.9 1081.0 Flood Risk 1440 min Summer 9.712 1.712 6.8 1043.8 Flood Risk 2160 min Summer 9.644 1.644 6.7 986.6 O K 2880 min Summer 9.581 1.581 6.6 935.1 O K 4320 min Summer 9.464 1.464 6.6 843.5 O K 5760 min Summer 9.354 1.354 6.6 760.0 O K 7200 min Summer 9.245 1.245 6.6 681.0 O K 8640 min Summer 9.135 1.135 6.6 604.6 O K 10080 min Summer 9.014 1.014 6.6 524.7 O K 15 min Winter 8.980 0.980 6.6 502.7 O K 30 min Winter 9.212 1.212 6.6 657.5 O K 60 min Winter 9.428 1.428 6.6 815.6 O K 120 min Winter 9.624 1.624 6.6 970.7 O K 180 min Winter 9.724 1.724 6.8 1054.1 Flood Risk 240 min Winter 9.785 1.785 6.9 1106.7 Flood Risk

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

15 min Summer 134.372 0.0 442.0 19 30 min Summer 88.266 0.0 525.5 34 60 min Summer 55.250 0.0 741.2 64 120 min Summer 33.426 0.0 894.0 124 180 min Summer 24.587 0.0 980.6 184 240 min Summer 19.657 0.0 1031.4 242 360 min Summer 14.271 0.0 1053.3 362 480 min Summer 11.374 0.0 1051.5 482 600 min Summer 9.532 0.0 1046.9 602 720 min Summer 8.247 0.0 1042.1 722 960 min Summer 6.558 0.0 1033.1 960 1440 min Summer 4.740 0.0 1021.1 1256 2160 min Summer 3.420 0.0 1658.5 1640 2880 min Summer 2.711 0.0 1750.6 2020 4320 min Summer 1.951 0.0 1809.0 2856 5760 min Summer 1.543 0.0 1998.9 3688 7200 min Summer 1.286 0.0 2081.9 4536 8640 min Summer 1.107 0.0 2151.3 5352 10080 min Summer 0.976 0.0 2210.2 6152 15 min Winter 134.372 0.0 489.6 19 30 min Winter 88.266 0.0 519.8 34 60 min Winter 55.250 0.0 829.1 64 120 min Winter 33.426 0.0 994.1 122 180 min Winter 24.587 0.0 1056.1 180 240 min Winter 19.657 0.0 1063.6 240

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Basin Norwich NR7 0EP 2.0m Deep Date 08/06/2018 09:37 AM Designed by MJWH File Attenuation Basin Sizing 2m Checked by XPDe. Solutions.. Source Control 2016.1.1

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

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

360 min Winter 9.857 1.857 7.0 1169.9 Flood Risk 480 min Winter 9.900 1.900 7.1 1208.4 Flood Risk 600 min Winter 9.925 1.925 7.2 1231.3 Flood Risk 720 min Winter 9.939 1.939 7.2 1244.0 Flood Risk 960 min Winter 9.946 1.946 7.2 1250.4 Flood Risk 1440 min Winter 9.915 1.915 7.1 1222.3 Flood Risk 2160 min Winter 9.834 1.834 7.0 1149.1 Flood Risk 2880 min Winter 9.757 1.757 6.9 1082.5 Flood Risk 4320 min Winter 9.602 1.602 6.6 952.3 O K 5760 min Winter 9.445 1.445 6.6 828.5 O K 7200 min Winter 9.286 1.286 6.6 710.4 O K 8640 min Winter 9.117 1.117 6.6 592.8 O K 10080 min Winter 8.885 0.885 6.6 443.7 O K

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

360 min Winter 14.271 0.0 1063.3 356 480 min Winter 11.374 0.0 1062.0 474 600 min Winter 9.532 0.0 1061.5 590 720 min Winter 8.247 0.0 1062.3 704 960 min Winter 6.558 0.0 1068.2 932 1440 min Winter 4.740 0.0 1070.4 1368 2160 min Winter 3.420 0.0 1855.8 1728 2880 min Winter 2.711 0.0 1954.1 2188 4320 min Winter 1.951 0.0 1885.1 3108 5760 min Winter 1.543 0.0 2238.8 3984 7200 min Winter 1.286 0.0 2331.8 4896 8640 min Winter 1.107 0.0 2409.6 5784 10080 min Winter 0.976 0.0 2476.0 6456

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Basin Norwich NR7 0EP 2.0m Deep Date 08/06/2018 09:37 AM Designed by MJWH File Attenuation Basin Sizing 2m Checked by XPDe. Solutions.. Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Basin Norwich NR7 0EP 2.0m Deep Date 08/06/2018 09:37 AM Designed by MJWH File Attenuation Basin Sizing 2m Checked by XPDe. Solutions.. Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Tank or Pond Structure

Invert Level (m) 8.000

Depth (m) Area (m²) Depth (m) Area (m²)

0.000 400.0 2.000 938.5

Hydro-Brake® Optimum Outflow Control

Unit Reference MD-SHE-0111-7300-2000-7300 Design Head (m) 2.000 Design Flow (l/s) 7.3 Flush-Flo™ Calculated Objective Minimise upstream storage Application Surface Sump Available Yes Diameter (mm) 111 Invert Level (m) 8.000 Minimum Outlet Pipe Diameter (mm) 150 Suggested Manhole Diameter (mm) 1200

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

Design Point (Calculated) 2.000 7.3 Kick-Flo® 0.996 5.3 Flush-Flo™ 0.486 6.6 Mean Flow over Head Range - 6.0

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 3.9 0.800 6.2 2.000 7.3 4.000 10.1 7.000 13.2 0.200 5.8 1.000 5.3 2.200 7.6 4.500 10.7 7.500 13.6 0.300 6.4 1.200 5.7 2.400 7.9 5.000 11.2 8.000 14.1 0.400 6.6 1.400 6.2 2.600 8.3 5.500 11.8 8.500 14.5 0.500 6.6 1.600 6.6 3.000 8.8 6.000 12.3 9.000 14.9 0.600 6.6 1.800 6.9 3.500 9.5 6.500 12.7 9.500 15.3

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 0.4m Deep Date 06/06/2018 09:39 AM Designed by MJWH File Attenuation Crate Sizing Checked by 0.4mXP Solutions ... Source Control 2016.1.1

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

Half Drain Time : 1553 minutes.

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

15 min Summer 8.982 0.132 0.0 6.0 6.0 450.4 O K 30 min Summer 9.022 0.172 0.0 6.7 6.7 588.8 O K 60 min Summer 9.064 0.214 0.0 7.0 7.0 731.4 O K 120 min Summer 9.105 0.255 0.0 7.2 7.2 872.4 O K 180 min Summer 9.128 0.278 0.0 7.2 7.2 949.7 O K 240 min Summer 9.142 0.292 0.0 7.2 7.2 999.4 O K 360 min Summer 9.160 0.310 0.0 7.3 7.3 1061.2 O K 480 min Summer 9.172 0.322 0.0 7.3 7.3 1100.6 O K 600 min Summer 9.179 0.329 0.0 7.3 7.3 1125.6 O K 720 min Summer 9.184 0.334 0.0 7.3 7.3 1141.2 O K 960 min Summer 9.187 0.337 0.0 7.3 7.3 1154.1 O K 1440 min Summer 9.186 0.336 0.0 7.3 7.3 1148.9 O K 2160 min Summer 9.180 0.330 0.0 7.3 7.3 1129.4 O K 2880 min Summer 9.172 0.322 0.0 7.3 7.3 1101.0 O K 4320 min Summer 9.151 0.301 0.0 7.2 7.2 1029.3 O K 5760 min Summer 9.129 0.279 0.0 7.2 7.2 952.5 O K 7200 min Summer 9.107 0.257 0.0 7.2 7.2 878.1 O K 8640 min Summer 9.087 0.237 0.0 7.1 7.1 808.9 O K 10080 min Summer 9.068 0.218 0.0 7.0 7.0 746.3 O K 15 min Winter 8.997 0.147 0.0 6.5 6.5 504.4 O K 30 min Winter 9.043 0.193 0.0 6.9 6.9 659.9 O K 60 min Winter 9.090 0.240 0.0 7.1 7.1 820.0 O K 120 min Winter 9.136 0.286 0.0 7.2 7.2 979.5 O K 180 min Winter 9.162 0.312 0.0 7.3 7.3 1067.4 O K

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

15 min Summer 134.372 0.0 280.2 19 30 min Summer 88.266 0.0 384.1 34 60 min Summer 55.250 0.0 618.1 64 120 min Summer 33.426 0.0 752.3 124 180 min Summer 24.587 0.0 827.9 184 240 min Summer 19.657 0.0 878.1 242 360 min Summer 14.271 0.0 944.0 362 480 min Summer 11.374 0.0 987.4 482 600 min Summer 9.532 0.0 1015.5 602 720 min Summer 8.247 0.0 1032.9 722 960 min Summer 6.558 0.0 1043.6 960 1440 min Summer 4.740 0.0 1007.1 1224 2160 min Summer 3.420 0.0 1535.5 1580 2880 min Summer 2.711 0.0 1602.2 1988 4320 min Summer 1.951 0.0 1651.3 2772 5760 min Summer 1.543 0.0 1948.2 3584 7200 min Summer 1.286 0.0 2022.5 4392 8640 min Summer 1.107 0.0 2077.3 5112 10080 min Summer 0.976 0.0 2109.3 5856 15 min Winter 134.372 0.0 321.5 19 30 min Winter 88.266 0.0 432.0 33 60 min Winter 55.250 0.0 696.5 64 120 min Winter 33.426 0.0 842.3 122 180 min Winter 24.587 0.0 922.4 180

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 0.4m Deep Date 06/06/2018 09:39 AM Designed by MJWH File Attenuation Crate Sizing Checked by 0.4mXP Solutions ... Source Control 2016.1.1

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

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

240 min Winter 9.179 0.329 0.0 7.3 7.3 1124.2 O K 360 min Winter 9.200 0.350 0.0 7.3 7.3 1196.1 O K 480 min Winter 9.214 0.364 0.0 7.3 7.3 1243.2 O K 600 min Winter 9.223 0.373 0.0 7.3 7.3 1274.4 O K 720 min Winter 9.229 0.379 0.0 7.3 7.3 1295.2 O K 960 min Winter 9.235 0.385 0.0 7.3 7.3 1316.9 O K 1440 min Winter 9.235 0.385 0.0 7.3 7.3 1315.6 O K 2160 min Winter 9.223 0.373 0.0 7.3 7.3 1276.0 O K 2880 min Winter 9.210 0.360 0.0 7.3 7.3 1231.5 O K 4320 min Winter 9.177 0.327 0.0 7.3 7.3 1119.8 O K 5760 min Winter 9.143 0.293 0.0 7.2 7.2 1002.0 O K 7200 min Winter 9.110 0.260 0.0 7.2 7.2 890.4 O K 8640 min Winter 9.081 0.231 0.0 7.1 7.1 789.7 O K 10080 min Winter 9.055 0.205 0.0 7.0 7.0 701.5 O K

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

240 min Winter 19.657 0.0 974.1 240 360 min Winter 14.271 0.0 1037.9 356 480 min Winter 11.374 0.0 1075.0 474 600 min Winter 9.532 0.0 1094.0 590 720 min Winter 8.247 0.0 1100.7 704 960 min Winter 6.558 0.0 1090.2 932 1440 min Winter 4.740 0.0 1039.2 1358 2160 min Winter 3.420 0.0 1713.3 1708 2880 min Winter 2.711 0.0 1781.0 2160 4320 min Winter 1.951 0.0 1807.2 3028 5760 min Winter 1.543 0.0 2185.1 3872 7200 min Winter 1.286 0.0 2269.5 4688 8640 min Winter 1.107 0.0 2333.2 5448 10080 min Winter 0.976 0.0 2372.9 6160

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 0.4m Deep Date 06/06/2018 09:39 AM Designed by MJWH File Attenuation Crate Sizing Checked by 0.4mXP Solutions ... Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 0.4m Deep Date 06/06/2018 09:39 AM Designed by MJWH File Attenuation Crate Sizing Checked by 0.4mXP Solutions ... Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Cellular Storage Structure

Invert Level (m) 8.850 Safety Factor 5.0 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) Depth (m) Area (m²) Inf. Area (m²)

0.000 3600.0 3600.0 0.400 3600.0 3696.0 0.500 0.0 3696.0

Hydro-Brake® Optimum Outflow Control

Unit Reference MD-SHE-0124-7300-1150-7300 Design Head (m) 1.150 Design Flow (l/s) 7.3 Flush-Flo™ Calculated Objective Minimise upstream storage Application Surface Sump Available Yes Diameter (mm) 124 Invert Level (m) 8.850 Minimum Outlet Pipe Diameter (mm) 150 Suggested Manhole Diameter (mm) 1200

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

Design Point (Calculated) 1.150 7.3 Kick-Flo® 0.732 5.9 Flush-Flo™ 0.341 7.3 Mean Flow over Head Range - 6.3

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 4.4 0.800 6.2 2.000 9.5 4.000 13.1 7.000 17.2 0.200 6.9 1.000 6.8 2.200 9.9 4.500 13.9 7.500 17.8 0.300 7.2 1.200 7.4 2.400 10.3 5.000 14.6 8.000 18.3 0.400 7.2 1.400 8.0 2.600 10.7 5.500 15.3 8.500 18.9 0.500 7.1 1.600 8.5 3.000 11.5 6.000 16.0 9.000 19.4 0.600 6.8 1.800 9.0 3.500 12.3 6.500 16.6 9.500 19.9

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 0.8m Deep Date 06/06/2018 09:39 AM Designed by MJWH File Attenuation Crate Sizing Checked by 0.8mXP Solutions ... Source Control 2016.1.1

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

Half Drain Time : 1492 minutes.

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

15 min Summer 8.725 0.275 0.0 7.0 7.0 449.0 O K 30 min Summer 8.809 0.359 0.0 7.2 7.2 587.0 O K 60 min Summer 8.896 0.446 0.0 7.3 7.3 728.2 O K 120 min Summer 8.980 0.530 0.0 7.3 7.3 866.6 O K 180 min Summer 9.026 0.576 0.0 7.3 7.3 941.4 O K 240 min Summer 9.055 0.605 0.0 7.3 7.3 988.6 O K 360 min Summer 9.090 0.640 0.0 7.3 7.3 1045.8 O K 480 min Summer 9.111 0.661 0.0 7.3 7.3 1080.8 O K 600 min Summer 9.124 0.674 0.0 7.3 7.3 1101.5 O K 720 min Summer 9.131 0.681 0.0 7.3 7.3 1112.9 O K 960 min Summer 9.134 0.684 0.0 7.3 7.3 1117.8 O K 1440 min Summer 9.120 0.670 0.0 7.3 7.3 1095.1 O K 2160 min Summer 9.094 0.644 0.0 7.3 7.3 1052.3 O K 2880 min Summer 9.065 0.615 0.0 7.3 7.3 1005.1 O K 4320 min Summer 9.005 0.555 0.0 7.3 7.3 906.5 O K 5760 min Summer 8.947 0.497 0.0 7.3 7.3 812.6 O K 7200 min Summer 8.895 0.445 0.0 7.3 7.3 726.7 O K 8640 min Summer 8.848 0.398 0.0 7.3 7.3 650.1 O K 10080 min Summer 8.806 0.356 0.0 7.2 7.2 582.3 O K 15 min Winter 8.758 0.308 0.0 7.1 7.1 503.2 O K 30 min Winter 8.853 0.403 0.0 7.3 7.3 658.1 O K 60 min Winter 8.950 0.500 0.0 7.3 7.3 816.9 O K 120 min Winter 9.046 0.596 0.0 7.3 7.3 974.0 O K 180 min Winter 9.099 0.649 0.0 7.3 7.3 1059.7 O K

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

15 min Summer 134.372 0.0 378.8 19 30 min Summer 88.266 0.0 488.4 34 60 min Summer 55.250 0.0 702.5 64 120 min Summer 33.426 0.0 847.3 124 180 min Summer 24.587 0.0 929.6 184 240 min Summer 19.657 0.0 984.5 242 360 min Summer 14.271 0.0 1055.4 362 480 min Summer 11.374 0.0 1098.4 482 600 min Summer 9.532 0.0 1120.2 602 720 min Summer 8.247 0.0 1126.8 722 960 min Summer 6.558 0.0 1116.3 960 1440 min Summer 4.740 0.0 1072.2 1240 2160 min Summer 3.420 0.0 1623.3 1600 2880 min Summer 2.711 0.0 1706.6 1988 4320 min Summer 1.951 0.0 1798.4 2808 5760 min Summer 1.543 0.0 1987.0 3576 7200 min Summer 1.286 0.0 2067.8 4392 8640 min Summer 1.107 0.0 2132.5 5104 10080 min Summer 0.976 0.0 2181.1 5848 15 min Winter 134.372 0.0 423.2 19 30 min Winter 88.266 0.0 534.1 33 60 min Winter 55.250 0.0 786.3 64 120 min Winter 33.426 0.0 943.9 122 180 min Winter 24.587 0.0 1029.9 180

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 0.8m Deep Date 06/06/2018 09:39 AM Designed by MJWH File Attenuation Crate Sizing Checked by 0.8mXP Solutions ... Source Control 2016.1.1

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

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

240 min Winter 9.132 0.682 0.0 7.3 7.3 1114.6 O K 360 min Winter 9.174 0.724 0.0 7.3 7.3 1182.6 O K 480 min Winter 9.200 0.750 0.0 7.3 7.3 1226.2 O K 600 min Winter 9.217 0.767 0.0 7.3 7.3 1254.1 O K 720 min Winter 9.228 0.778 0.0 7.3 7.3 1271.7 O K 960 min Winter 9.238 0.788 0.0 7.3 7.3 1287.1 O K 1440 min Winter 9.229 0.779 0.0 7.3 7.3 1273.0 O K 2160 min Winter 9.189 0.739 0.0 7.3 7.3 1207.6 O K 2880 min Winter 9.149 0.699 0.0 7.3 7.3 1142.7 O K 4320 min Winter 9.061 0.611 0.0 7.3 7.3 998.4 O K 5760 min Winter 8.974 0.524 0.0 7.3 7.3 856.9 O K 7200 min Winter 8.896 0.446 0.0 7.3 7.3 729.1 O K 8640 min Winter 8.828 0.378 0.0 7.2 7.2 617.9 O K 10080 min Winter 8.771 0.321 0.0 7.1 7.1 524.1 O K

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

240 min Winter 19.657 0.0 1083.5 240 360 min Winter 14.271 0.0 1140.2 358 480 min Winter 11.374 0.0 1157.9 474 600 min Winter 9.532 0.0 1156.0 590 720 min Winter 8.247 0.0 1148.7 706 960 min Winter 6.558 0.0 1127.2 932 1440 min Winter 4.740 0.0 1077.1 1370 2160 min Winter 3.420 0.0 1811.6 1728 2880 min Winter 2.711 0.0 1898.8 2164 4320 min Winter 1.951 0.0 1960.2 3064 5760 min Winter 1.543 0.0 2226.2 3872 7200 min Winter 1.286 0.0 2317.1 4680 8640 min Winter 1.107 0.0 2390.9 5440 10080 min Winter 0.976 0.0 2447.7 6152

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 0.8m Deep Date 06/06/2018 09:39 AM Designed by MJWH File Attenuation Crate Sizing Checked by 0.8mXP Solutions ... Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 0.8m Deep Date 06/06/2018 09:39 AM Designed by MJWH File Attenuation Crate Sizing Checked by 0.8mXP Solutions ... Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Cellular Storage Structure

Invert Level (m) 8.450 Safety Factor 5.0 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) Depth (m) Area (m²) Inf. Area (m²)

0.000 1720.0 1720.0 0.800 1720.0 1852.8 0.900 0.0 1852.8

Hydro-Brake® Optimum Outflow Control

Unit Reference MD-SHE-0118-7300-1550-7300 Design Head (m) 1.550 Design Flow (l/s) 7.3 Flush-Flo™ Calculated Objective Minimise upstream storage Application Surface Sump Available Yes Diameter (mm) 118 Invert Level (m) 8.450 Minimum Outlet Pipe Diameter (mm) 150 Suggested Manhole Diameter (mm) 1200

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

Design Point (Calculated) 1.550 7.3 Kick-Flo® 0.945 5.8 Flush-Flo™ 0.455 7.3 Mean Flow over Head Range - 6.4

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 4.2 0.800 6.7 2.000 8.2 4.000 11.4 7.000 14.9 0.200 6.5 1.000 5.9 2.200 8.6 4.500 12.1 7.500 15.4 0.300 7.1 1.200 6.5 2.400 9.0 5.000 12.7 8.000 15.9 0.400 7.3 1.400 7.0 2.600 9.3 5.500 13.3 8.500 16.4 0.500 7.3 1.600 7.4 3.000 10.0 6.000 13.8 9.000 16.8 0.600 7.2 1.800 7.8 3.500 10.7 6.500 14.4 9.500 17.3

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 1.2m Deep Date 06/06/2018 09:31 AM Designed by MJWH File Attenuation Crate Sizing Checked by 1.2mXP Solutions ... Source Control 2016.1.1

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

Half Drain Time : 1638 minutes.

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

15 min Summer 8.457 0.407 0.0 6.7 6.7 448.8 O K 30 min Summer 8.583 0.533 0.0 6.7 6.7 586.9 O K 60 min Summer 8.711 0.661 0.0 6.7 6.7 728.1 O K 120 min Summer 8.837 0.787 0.0 6.7 6.7 867.0 O K 180 min Summer 8.905 0.855 0.0 6.7 6.7 942.6 O K 240 min Summer 8.949 0.899 0.0 6.7 6.7 990.9 O K 360 min Summer 9.004 0.954 0.0 6.7 6.7 1051.1 O K 480 min Summer 9.039 0.989 0.0 6.7 6.7 1090.0 O K 600 min Summer 9.062 1.012 0.0 6.7 6.7 1115.1 O K 720 min Summer 9.076 1.026 0.0 6.7 6.7 1130.7 O K 960 min Summer 9.088 1.038 0.0 6.7 6.7 1143.4 O K 1440 min Summer 9.074 1.024 0.0 6.7 6.7 1128.2 O K 2160 min Summer 9.019 0.969 0.0 6.7 6.7 1067.9 O K 2880 min Summer 8.966 0.916 0.0 6.7 6.7 1009.6 O K 4320 min Summer 8.869 0.819 0.0 6.7 6.7 902.9 O K 5760 min Summer 8.781 0.731 0.0 6.7 6.7 805.9 O K 7200 min Summer 8.701 0.651 0.0 6.7 6.7 717.5 O K 8640 min Summer 8.629 0.579 0.0 6.7 6.7 638.0 O K 10080 min Summer 8.564 0.514 0.0 6.7 6.7 566.3 O K 15 min Winter 8.507 0.457 0.0 6.7 6.7 503.1 O K 30 min Winter 8.647 0.597 0.0 6.7 6.7 658.0 O K 60 min Winter 8.791 0.741 0.0 6.7 6.7 817.1 O K 120 min Winter 8.935 0.885 0.0 6.7 6.7 975.2 O K 180 min Winter 9.014 0.964 0.0 6.7 6.7 1062.6 O K

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

15 min Summer 134.372 0.0 404.6 19 30 min Summer 88.266 0.0 509.4 34 60 min Summer 55.250 0.0 720.9 64 120 min Summer 33.426 0.0 867.1 124 180 min Summer 24.587 0.0 948.4 184 240 min Summer 19.657 0.0 999.5 242 360 min Summer 14.271 0.0 1049.6 362 480 min Summer 11.374 0.0 1054.3 482 600 min Summer 9.532 0.0 1043.6 602 720 min Summer 8.247 0.0 1029.8 722 960 min Summer 6.558 0.0 1000.6 962 1440 min Summer 4.740 0.0 945.3 1440 2160 min Summer 3.420 0.0 1636.1 1772 2880 min Summer 2.711 0.0 1720.4 2100 4320 min Summer 1.951 0.0 1794.8 2856 5760 min Summer 1.543 0.0 1993.5 3640 7200 min Summer 1.286 0.0 2075.5 4400 8640 min Summer 1.107 0.0 2142.7 5184 10080 min Summer 0.976 0.0 2196.1 5944 15 min Winter 134.372 0.0 448.9 19 30 min Winter 88.266 0.0 542.7 33 60 min Winter 55.250 0.0 805.6 64 120 min Winter 33.426 0.0 961.8 122 180 min Winter 24.587 0.0 1035.9 182

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 1.2m Deep Date 06/06/2018 09:31 AM Designed by MJWH File Attenuation Crate Sizing Checked by 1.2mXP Solutions ... Source Control 2016.1.1

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

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

240 min Winter 9.066 1.016 0.0 6.7 6.7 1119.7 O K 360 min Winter 9.131 1.081 0.0 6.7 6.7 1191.3 O K 480 min Winter 9.173 1.123 0.0 6.7 6.7 1237.6 O K 600 min Winter 9.201 1.151 0.0 6.7 6.7 1267.9 O K 720 min Winter 9.219 1.169 0.0 6.7 6.7 1287.8 O K 960 min Winter 9.237 1.187 0.0 6.7 6.7 1307.6 O K 1440 min Winter 9.233 1.183 0.0 6.7 6.7 1303.6 O K 2160 min Winter 9.183 1.133 0.0 6.7 6.7 1248.2 O K 2880 min Winter 9.119 1.069 0.0 6.7 6.7 1178.0 O K 4320 min Winter 8.979 0.929 0.0 6.7 6.7 1024.2 O K 5760 min Winter 8.840 0.790 0.0 6.7 6.7 871.1 O K 7200 min Winter 8.717 0.667 0.0 6.7 6.7 735.0 O K 8640 min Winter 8.609 0.559 0.0 6.7 6.7 615.8 O K 10080 min Winter 8.516 0.466 0.0 6.7 6.7 513.8 O K

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

240 min Winter 19.657 0.0 1061.0 240 360 min Winter 14.271 0.0 1055.0 358 480 min Winter 11.374 0.0 1039.2 476 600 min Winter 9.532 0.0 1022.7 592 720 min Winter 8.247 0.0 1007.0 708 960 min Winter 6.558 0.0 978.8 936 1440 min Winter 4.740 0.0 931.2 1384 2160 min Winter 3.420 0.0 1817.8 2016 2880 min Winter 2.711 0.0 1881.4 2304 4320 min Winter 1.951 0.0 1851.5 3156 5760 min Winter 1.543 0.0 2232.9 3984 7200 min Winter 1.286 0.0 2324.9 4760 8640 min Winter 1.107 0.0 2401.0 5528 10080 min Winter 0.976 0.0 2462.5 6248

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 1.2m Deep Date 06/06/2018 09:31 AM Designed by MJWH File Attenuation Crate Sizing Checked by 1.2mXP Solutions ... Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 1.2m Deep Date 06/06/2018 09:31 AM Designed by MJWH File Attenuation Crate Sizing Checked by 1.2mXP Solutions ... Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Cellular Storage Structure

Invert Level (m) 8.050 Safety Factor 5.0 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) Depth (m) Area (m²) Inf. Area (m²)

0.000 1160.0 1160.0 1.200 1160.0 1325.6 1.300 0.0 1325.6

Hydro-Brake® Optimum Outflow Control

Unit Reference MD-SHE-0112-7300-1950-7300 Design Head (m) 1.950 Design Flow (l/s) 7.3 Flush-Flo™ Calculated Objective Minimise upstream storage Application Surface Sump Available Yes Diameter (mm) 112 Invert Level (m) 8.050 Minimum Outlet Pipe Diameter (mm) 150 Suggested Manhole Diameter (mm) 1200

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

Design Point (Calculated) 1.950 7.3 Kick-Flo® 1.000 5.3 Flush-Flo™ 0.487 6.7 Mean Flow over Head Range - 6.1

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 3.9 0.800 6.3 2.000 7.4 4.000 10.2 7.000 13.4 0.200 5.9 1.000 5.4 2.200 7.7 4.500 10.8 7.500 13.8 0.300 6.5 1.200 5.8 2.400 8.0 5.000 11.4 8.000 14.2 0.400 6.7 1.400 6.2 2.600 8.4 5.500 11.9 8.500 14.7 0.500 6.7 1.600 6.7 3.000 8.9 6.000 12.4 9.000 15.1 0.600 6.7 1.800 7.0 3.500 9.6 6.500 12.9 9.500 15.5

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 1.6m Deep Date 06/06/2018 09:37 AM Designed by MJWH File Attenuation Crate Sizing Checked by 1.6mXP Solutions ... Source Control 2016.1.1

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

Half Drain Time : 1877 minutes.

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

15 min Summer 8.175 0.525 0.0 6.0 6.0 449.1 O K 30 min Summer 8.337 0.687 0.0 6.0 6.0 587.4 O K 60 min Summer 8.503 0.853 0.0 6.0 6.0 729.6 O K 120 min Summer 8.669 1.019 0.0 6.0 6.0 871.3 O K 180 min Summer 8.760 1.110 0.0 6.0 6.0 948.7 O K 240 min Summer 8.817 1.167 0.0 6.0 6.0 998.0 O K 360 min Summer 8.889 1.239 0.0 6.0 6.0 1059.1 O K 480 min Summer 8.934 1.284 0.0 6.0 6.0 1097.9 O K 600 min Summer 8.963 1.313 0.0 6.0 6.0 1122.3 O K 720 min Summer 8.980 1.330 0.0 6.0 6.0 1137.5 O K 960 min Summer 8.995 1.345 0.0 6.0 6.0 1150.1 O K 1440 min Summer 8.979 1.329 0.0 6.0 6.0 1136.5 O K 2160 min Summer 8.925 1.275 0.0 6.0 6.0 1089.8 O K 2880 min Summer 8.871 1.221 0.0 6.0 6.0 1044.0 O K 4320 min Summer 8.769 1.119 0.0 6.0 6.0 956.9 O K 5760 min Summer 8.670 1.020 0.0 6.0 6.0 872.4 O K 7200 min Summer 8.561 0.911 0.0 6.0 6.0 779.1 O K 8640 min Summer 8.457 0.807 0.0 6.0 6.0 689.8 O K 10080 min Summer 8.366 0.716 0.0 6.0 6.0 612.5 O K 15 min Winter 8.239 0.589 0.0 6.0 6.0 503.3 O K 30 min Winter 8.420 0.770 0.0 6.0 6.0 658.7 O K 60 min Winter 8.608 0.958 0.0 6.0 6.0 819.3 O K 120 min Winter 8.795 1.145 0.0 6.0 6.0 979.0 O K 180 min Winter 8.898 1.248 0.0 6.0 6.0 1066.8 O K

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

15 min Summer 134.372 0.0 411.9 19 30 min Summer 88.266 0.0 492.6 34 60 min Summer 55.250 0.0 726.0 64 120 min Summer 33.426 0.0 864.6 124 180 min Summer 24.587 0.0 923.8 184 240 min Summer 19.657 0.0 936.7 244 360 min Summer 14.271 0.0 931.6 362 480 min Summer 11.374 0.0 920.7 482 600 min Summer 9.532 0.0 909.6 602 720 min Summer 8.247 0.0 899.2 722 960 min Summer 6.558 0.0 880.2 962 1440 min Summer 4.740 0.0 847.9 1440 2160 min Summer 3.420 0.0 1633.7 1792 2880 min Summer 2.711 0.0 1693.1 2164 4320 min Summer 1.951 0.0 1577.0 2980 5760 min Summer 1.543 0.0 1995.2 3808 7200 min Summer 1.286 0.0 2077.6 4608 8640 min Summer 1.107 0.0 2146.1 5352 10080 min Summer 0.976 0.0 2201.8 6056 15 min Winter 134.372 0.0 452.2 19 30 min Winter 88.266 0.0 502.6 34 60 min Winter 55.250 0.0 808.2 64 120 min Winter 33.426 0.0 931.9 122 180 min Winter 24.587 0.0 943.3 182

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 1.6m Deep Date 06/06/2018 09:37 AM Designed by MJWH File Attenuation Crate Sizing Checked by 1.6mXP Solutions ... Source Control 2016.1.1

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

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

240 min Winter 8.964 1.314 0.0 6.0 6.0 1123.5 O K 360 min Winter 9.048 1.398 0.0 6.0 6.0 1195.0 O K 480 min Winter 9.102 1.452 0.0 6.0 6.0 1241.4 O K 600 min Winter 9.138 1.488 0.0 6.0 6.0 1272.0 O K 720 min Winter 9.161 1.511 0.0 6.0 6.0 1292.3 O K 960 min Winter 9.186 1.536 0.0 6.0 6.0 1313.1 O K 1440 min Winter 9.184 1.534 0.0 6.0 6.0 1311.3 O K 2160 min Winter 9.125 1.475 0.0 6.0 6.0 1260.8 O K 2880 min Winter 9.056 1.406 0.0 6.0 6.0 1202.2 O K 4320 min Winter 8.922 1.272 0.0 6.0 6.0 1087.8 O K 5760 min Winter 8.784 1.134 0.0 6.0 6.0 970.0 O K 7200 min Winter 8.640 0.990 0.0 6.0 6.0 846.2 O K 8640 min Winter 8.468 0.818 0.0 6.0 6.0 699.2 O K 10080 min Winter 8.329 0.679 0.0 6.0 6.0 580.8 O K

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

240 min Winter 19.657 0.0 939.1 240 360 min Winter 14.271 0.0 927.5 358 480 min Winter 11.374 0.0 917.5 476 600 min Winter 9.532 0.0 909.5 592 720 min Winter 8.247 0.0 902.9 708 960 min Winter 6.558 0.0 892.9 936 1440 min Winter 4.740 0.0 884.4 1384 2160 min Winter 3.420 0.0 1792.8 2008 2880 min Winter 2.711 0.0 1770.3 2276 4320 min Winter 1.951 0.0 1629.7 3200 5760 min Winter 1.543 0.0 2234.5 4144 7200 min Winter 1.286 0.0 2326.6 5048 8640 min Winter 1.107 0.0 2403.7 5784 10080 min Winter 0.976 0.0 2467.9 6456

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 1.6m Deep Date 06/06/2018 09:37 AM Designed by MJWH File Attenuation Crate Sizing Checked by 1.6mXP Solutions ... Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Attenuation Crates Norwich NR7 0EP 1.6m Deep Date 06/06/2018 09:37 AM Designed by MJWH File Attenuation Crate Sizing Checked by 1.6mXP Solutions ... Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Cellular Storage Structure

Invert Level (m) 7.650 Safety Factor 5.0 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) Depth (m) Area (m²) Inf. Area (m²)

0.000 900.0 900.0 1.600 900.0 1108.0 1.700 0.0 1108.0

Hydro-Brake® Optimum Outflow Control

Unit Reference MD-SHE-0107-7300-2350-7300 Design Head (m) 2.350 Design Flow (l/s) 7.3 Flush-Flo™ Calculated Objective Minimise upstream storage Application Surface Sump Available Yes Diameter (mm) 107 Invert Level (m) 7.650 Minimum Outlet Pipe Diameter (mm) 150 Suggested Manhole Diameter (mm) 1200

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

Design Point (Calculated) 2.350 7.3 Kick-Flo® 0.954 4.8 Flush-Flo™ 0.466 6.0 Mean Flow over Head Range - 5.8

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 3.6 0.800 5.6 2.000 6.8 4.000 9.4 7.000 12.2 0.200 5.4 1.000 4.9 2.200 7.1 4.500 9.9 7.500 12.6 0.300 5.8 1.200 5.3 2.400 7.4 5.000 10.4 8.000 13.0 0.400 6.0 1.400 5.7 2.600 7.6 5.500 10.9 8.500 13.4 0.500 6.0 1.600 6.1 3.000 8.2 6.000 11.4 9.000 13.8 0.600 5.9 1.800 6.4 3.500 8.8 6.500 11.8 9.500 14.1

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin Norwich NR7 0EP 0.5m Deep Date 06/06/2018 10:03 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.5m...XP Solutions Source Control 2016.1.1

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

Half Drain Time : 430 minutes.

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

15 min Summer 9.731 0.231 18.2 438.9 Flood Risk 30 min Summer 9.796 0.296 18.8 567.9 Flood Risk 60 min Summer 9.857 0.357 19.3 689.6 Flood Risk 120 min Summer 9.906 0.406 19.7 789.1 Flood Risk 180 min Summer 9.923 0.423 19.9 824.6 Flood Risk 240 min Summer 9.927 0.427 19.9 833.1 Flood Risk 360 min Summer 9.920 0.420 19.8 817.8 Flood Risk 480 min Summer 9.911 0.411 19.8 798.7 Flood Risk 600 min Summer 9.900 0.400 19.7 777.9 Flood Risk 720 min Summer 9.890 0.390 19.6 756.6 Flood Risk 960 min Summer 9.869 0.369 19.4 714.1 Flood Risk 1440 min Summer 9.829 0.329 19.1 632.8 Flood Risk 2160 min Summer 9.773 0.273 18.6 522.5 Flood Risk 2880 min Summer 9.724 0.224 18.2 426.1 Flood Risk 4320 min Summer 9.646 0.146 17.5 274.1 O K 5760 min Summer 9.591 0.091 17.0 171.2 O K 7200 min Summer 9.559 0.059 16.8 110.8 O K 8640 min Summer 9.548 0.048 15.9 88.7 O K 10080 min Summer 9.542 0.042 14.1 78.8 O K 15 min Winter 9.758 0.258 18.5 493.0 Flood Risk 30 min Winter 9.832 0.332 19.1 639.1 Flood Risk 60 min Winter 9.901 0.401 19.7 778.8 Flood Risk 120 min Winter 9.958 0.458 20.2 896.6 Flood Risk 180 min Winter 9.981 0.481 20.4 943.0 Flood Risk

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

15 min Summer 134.372 0.0 19 30 min Summer 88.266 0.0 33 60 min Summer 55.250 0.0 62 120 min Summer 33.426 0.0 122 180 min Summer 24.587 0.0 182 240 min Summer 19.657 0.0 240 360 min Summer 14.271 0.0 324 480 min Summer 11.374 0.0 382 600 min Summer 9.532 0.0 446 720 min Summer 8.247 0.0 512 960 min Summer 6.558 0.0 646 1440 min Summer 4.740 0.0 922 2160 min Summer 3.420 0.0 1320 2880 min Summer 2.711 0.0 1700 4320 min Summer 1.951 0.0 2420 5760 min Summer 1.543 0.0 3112 7200 min Summer 1.286 0.0 3744 8640 min Summer 1.107 0.0 4408 10080 min Summer 0.976 0.0 5144 15 min Winter 134.372 0.0 18 30 min Winter 88.266 0.0 33 60 min Winter 55.250 0.0 62 120 min Winter 33.426 0.0 120 180 min Winter 24.587 0.0 178

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin Norwich NR7 0EP 0.5m Deep Date 06/06/2018 10:03 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.5m...XP Solutions Source Control 2016.1.1

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)

240 min Winter 9.988 0.488 20.4 959.1 Flood Risk 360 min Winter 9.985 0.485 20.4 952.7 Flood Risk 480 min Winter 9.973 0.473 20.3 926.8 Flood Risk 600 min Winter 9.960 0.460 20.2 900.0 Flood Risk 720 min Winter 9.947 0.447 20.1 872.8 Flood Risk 960 min Winter 9.918 0.418 19.8 813.7 Flood Risk 1440 min Winter 9.859 0.359 19.3 693.7 Flood Risk 2160 min Winter 9.776 0.276 18.6 528.8 Flood Risk 2880 min Winter 9.704 0.204 18.0 387.8 Flood Risk 4320 min Winter 9.596 0.096 17.1 180.1 O K 5760 min Winter 9.549 0.049 16.3 90.3 O K 7200 min Winter 9.541 0.041 13.6 75.5 O K 8640 min Winter 9.535 0.035 11.7 65.2 O K 10080 min Winter 9.531 0.031 10.4 57.6 O K

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

240 min Winter 19.657 0.0 234 360 min Winter 14.271 0.0 344 480 min Winter 11.374 0.0 442 600 min Winter 9.532 0.0 474 720 min Winter 8.247 0.0 550 960 min Winter 6.558 0.0 704 1440 min Winter 4.740 0.0 996 2160 min Winter 3.420 0.0 1408 2880 min Winter 2.711 0.0 1792 4320 min Winter 1.951 0.0 2468 5760 min Winter 1.543 0.0 2944 7200 min Winter 1.286 0.0 3672 8640 min Winter 1.107 0.0 4408 10080 min Winter 0.976 0.0 5112

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin Norwich NR7 0EP 0.5m Deep Date 06/06/2018 10:03 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.5m...XP Solutions Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin Norwich NR7 0EP 0.5m Deep Date 06/06/2018 10:03 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.5m...XP Solutions Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Infiltration Basin Structure

Invert Level (m) 9.500 Safety Factor 5.0 Infiltration Coefficient Base (m/hr) 0.15840 Porosity 1.00 Infiltration Coefficient Side (m/hr) 0.15840

Depth (m) Area (m²) Depth (m) Area (m²)

0.000 1850.0 0.500 2085.8

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_1-in-30 Norwich NR7 0EP 0.5m Deep Date 06/06/2018 10:21 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.5m...XP Solutions Source Control 2016.1.1

Summary of Results for 30 year Return Period (+40%)

Half Drain Time : 1424 minutes.

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

15 min Summer 9.685 0.185 5.2 345.7 O K 30 min Summer 9.738 0.238 5.3 447.8 Flood Risk 60 min Summer 9.792 0.292 5.5 551.9 Flood Risk 120 min Summer 9.844 0.344 5.6 654.6 Flood Risk 180 min Summer 9.872 0.372 5.7 710.9 Flood Risk 240 min Summer 9.890 0.390 5.7 747.3 Flood Risk 360 min Summer 9.912 0.412 5.8 791.4 Flood Risk 480 min Summer 9.925 0.425 5.8 817.1 Flood Risk 600 min Summer 9.932 0.432 5.8 831.5 Flood Risk 720 min Summer 9.935 0.435 5.8 838.6 Flood Risk 960 min Summer 9.936 0.436 5.8 839.0 Flood Risk 1440 min Summer 9.926 0.426 5.8 819.1 Flood Risk 2160 min Summer 9.909 0.409 5.8 784.5 Flood Risk 2880 min Summer 9.891 0.391 5.7 748.9 Flood Risk 4320 min Summer 9.856 0.356 5.6 678.7 Flood Risk 5760 min Summer 9.823 0.323 5.5 612.8 Flood Risk 7200 min Summer 9.791 0.291 5.5 550.9 Flood Risk 8640 min Summer 9.762 0.262 5.4 493.6 Flood Risk 10080 min Summer 9.734 0.234 5.3 440.3 Flood Risk 15 min Winter 9.707 0.207 5.3 387.6 Flood Risk 30 min Winter 9.766 0.266 5.4 502.2 Flood Risk 60 min Winter 9.826 0.326 5.6 619.5 Flood Risk 120 min Winter 9.885 0.385 5.7 736.6 Flood Risk 180 min Winter 9.917 0.417 5.8 801.7 Flood Risk

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

15 min Summer 103.633 0.0 19 30 min Summer 67.486 0.0 34 60 min Summer 42.036 0.0 64 120 min Summer 25.426 0.0 124 180 min Summer 18.752 0.0 182 240 min Summer 15.046 0.0 242 360 min Summer 10.991 0.0 362 480 min Summer 8.795 0.0 482 600 min Summer 7.394 0.0 602 720 min Summer 6.414 0.0 720 960 min Summer 5.123 0.0 960 1440 min Summer 3.728 0.0 1212 2160 min Summer 2.709 0.0 1580 2880 min Summer 2.159 0.0 1988 4320 min Summer 1.566 0.0 2808 5760 min Summer 1.247 0.0 3632 7200 min Summer 1.044 0.0 4400 8640 min Summer 0.903 0.0 5192 10080 min Summer 0.798 0.0 5952 15 min Winter 103.633 0.0 19 30 min Winter 67.486 0.0 33 60 min Winter 42.036 0.0 64 120 min Winter 25.426 0.0 122 180 min Winter 18.752 0.0 180

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_1-in-30 Norwich NR7 0EP 0.5m Deep Date 06/06/2018 10:21 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.5m...XP Solutions Source Control 2016.1.1

Summary of Results for 30 year Return Period (+40%)

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

240 min Winter 9.938 0.438 5.8 844.1 Flood Risk 360 min Winter 9.964 0.464 5.9 897.2 Flood Risk 480 min Winter 9.980 0.480 5.9 929.8 Flood Risk 600 min Winter 9.990 0.490 6.0 949.9 Flood Risk 720 min Winter 9.996 0.496 6.0 961.8 Flood Risk 960 min Winter 10.000 0.500 6.0 970.3 Flood Risk 1440 min Winter 9.992 0.492 6.0 953.9 Flood Risk 2160 min Winter 9.969 0.469 5.9 907.7 Flood Risk 2880 min Winter 9.946 0.446 5.9 859.9 Flood Risk 4320 min Winter 9.895 0.395 5.7 757.7 Flood Risk 5760 min Winter 9.846 0.346 5.6 658.3 Flood Risk 7200 min Winter 9.799 0.299 5.5 565.5 Flood Risk 8640 min Winter 9.755 0.255 5.4 480.1 Flood Risk 10080 min Winter 9.715 0.215 5.3 402.2 Flood Risk

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

240 min Winter 15.046 0.0 240 360 min Winter 10.991 0.0 356 480 min Winter 8.795 0.0 472 600 min Winter 7.394 0.0 588 720 min Winter 6.414 0.0 702 960 min Winter 5.123 0.0 926 1440 min Winter 3.728 0.0 1356 2160 min Winter 2.709 0.0 1688 2880 min Winter 2.159 0.0 2160 4320 min Winter 1.566 0.0 3068 5760 min Winter 1.247 0.0 3920 7200 min Winter 1.044 0.0 4752 8640 min Winter 0.903 0.0 5536 10080 min Winter 0.798 0.0 6344

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_1-in-30 Norwich NR7 0EP 0.5m Deep Date 06/06/2018 10:21 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.5m...XP Solutions Source Control 2016.1.1

Rainfall Details

Rainfall Model FSR Winter Storms Yes Return Period (years) 30 Cv (Summer) 0.750 Region England and Wales Cv (Winter) 0.840 M5-60 (mm) 19.500 Shortest Storm (mins) 15 Ratio R 0.400 Longest Storm (mins) 10080 Summer Storms Yes Climate Change % +40

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_1-in-30 Norwich NR7 0EP 0.5m Deep Date 06/06/2018 10:21 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.5m...XP Solutions Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Infiltration Basin Structure

Invert Level (m) 9.500 Safety Factor 5.0 Infiltration Coefficient Base (m/hr) 0.04680 Porosity 1.00 Infiltration Coefficient Side (m/hr) 0.04680

Depth (m) Area (m²) Depth (m) Area (m²)

0.000 1825.0 0.500 2059.2

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_Lower Rate Norwich NR7 0EP 0.5m Deep Date 06/06/2018 10:13 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.5m...XP Solutions Source Control 2016.1.1

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

Half Drain Time : 1437 minutes.

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

15 min Summer 9.685 0.185 6.7 448.3 O K 30 min Summer 9.740 0.240 6.9 585.8 Flood Risk 60 min Summer 9.796 0.296 7.0 725.7 Flood Risk 120 min Summer 9.849 0.349 7.2 861.4 Flood Risk 180 min Summer 9.877 0.377 7.2 933.3 Flood Risk 240 min Summer 9.894 0.394 7.3 977.7 Flood Risk 360 min Summer 9.914 0.414 7.4 1029.2 Flood Risk 480 min Summer 9.926 0.426 7.4 1058.5 Flood Risk 600 min Summer 9.931 0.431 7.4 1073.7 Flood Risk 720 min Summer 9.934 0.434 7.4 1079.8 Flood Risk 960 min Summer 9.932 0.432 7.4 1074.9 Flood Risk 1440 min Summer 9.919 0.419 7.4 1040.2 Flood Risk 2160 min Summer 9.898 0.398 7.3 986.3 Flood Risk 2880 min Summer 9.877 0.377 7.2 933.6 Flood Risk 4320 min Summer 9.838 0.338 7.1 833.6 Flood Risk 5760 min Summer 9.802 0.302 7.0 741.8 Flood Risk 7200 min Summer 9.769 0.269 6.9 657.5 Flood Risk 8640 min Summer 9.738 0.238 6.8 580.2 Flood Risk 10080 min Summer 9.710 0.210 6.8 509.4 Flood Risk 15 min Winter 9.707 0.207 6.8 502.5 Flood Risk 30 min Winter 9.769 0.269 6.9 657.0 Flood Risk 60 min Winter 9.831 0.331 7.1 814.7 Flood Risk 120 min Winter 9.891 0.391 7.3 969.3 Flood Risk 180 min Winter 9.923 0.423 7.4 1052.3 Flood Risk

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

15 min Summer 134.372 0.0 19 30 min Summer 88.266 0.0 34 60 min Summer 55.250 0.0 64 120 min Summer 33.426 0.0 124 180 min Summer 24.587 0.0 184 240 min Summer 19.657 0.0 242 360 min Summer 14.271 0.0 362 480 min Summer 11.374 0.0 482 600 min Summer 9.532 0.0 602 720 min Summer 8.247 0.0 722 960 min Summer 6.558 0.0 960 1440 min Summer 4.740 0.0 1212 2160 min Summer 3.420 0.0 1580 2880 min Summer 2.711 0.0 1988 4320 min Summer 1.951 0.0 2808 5760 min Summer 1.543 0.0 3624 7200 min Summer 1.286 0.0 4400 8640 min Summer 1.107 0.0 5184 10080 min Summer 0.976 0.0 5944 15 min Winter 134.372 0.0 19 30 min Winter 88.266 0.0 33 60 min Winter 55.250 0.0 64 120 min Winter 33.426 0.0 122 180 min Winter 24.587 0.0 180

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_Lower Rate Norwich NR7 0EP 0.5m Deep Date 06/06/2018 10:13 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.5m...XP Solutions Source Control 2016.1.1

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)

240 min Winter 9.943 0.443 7.4 1104.3 Flood Risk 360 min Winter 9.967 0.467 7.5 1166.7 Flood Risk 480 min Winter 9.981 0.481 7.5 1204.4 Flood Risk 600 min Winter 9.990 0.490 7.6 1226.5 Flood Risk 720 min Winter 9.994 0.494 7.6 1238.4 Flood Risk 960 min Winter 9.996 0.496 7.6 1243.3 Flood Risk 1440 min Winter 9.984 0.484 7.6 1212.3 Flood Risk 2160 min Winter 9.957 0.457 7.5 1141.4 Flood Risk 2880 min Winter 9.931 0.431 7.4 1071.5 Flood Risk 4320 min Winter 9.875 0.375 7.2 927.7 Flood Risk 5760 min Winter 9.822 0.322 7.1 791.5 Flood Risk 7200 min Winter 9.772 0.272 6.9 666.1 Flood Risk 8640 min Winter 9.727 0.227 6.8 552.7 Flood Risk 10080 min Winter 9.686 0.186 6.7 451.1 O K

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

240 min Winter 19.657 0.0 240 360 min Winter 14.271 0.0 356 480 min Winter 11.374 0.0 472 600 min Winter 9.532 0.0 588 720 min Winter 8.247 0.0 702 960 min Winter 6.558 0.0 926 1440 min Winter 4.740 0.0 1356 2160 min Winter 3.420 0.0 1688 2880 min Winter 2.711 0.0 2136 4320 min Winter 1.951 0.0 3028 5760 min Winter 1.543 0.0 3920 7200 min Winter 1.286 0.0 4752 8640 min Winter 1.107 0.0 5528 10080 min Winter 0.976 0.0 6256

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_Lower Rate Norwich NR7 0EP 0.5m Deep Date 06/06/2018 10:13 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.5m...XP Solutions Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_Lower Rate Norwich NR7 0EP 0.5m Deep Date 06/06/2018 10:13 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.5m...XP Solutions Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Infiltration Basin Structure

Invert Level (m) 9.500 Safety Factor 5.0 Infiltration Coefficient Base (m/hr) 0.04680 Porosity 1.00 Infiltration Coefficient Side (m/hr) 0.04680

Depth (m) Area (m²) Depth (m) Area (m²)

0.000 2375.0 0.500 2641.2

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin Norwich NR7 0EP 0.6m Deep Date 06/06/2018 10:06 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.6m...XP Solutions Source Control 2016.1.1

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

Half Drain Time : 488 minutes.

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

15 min Summer 9.678 0.278 15.6 440.8 O K 30 min Summer 9.757 0.357 16.2 571.4 Flood Risk 60 min Summer 9.831 0.431 16.8 696.4 Flood Risk 120 min Summer 9.893 0.493 17.3 802.8 Flood Risk 180 min Summer 9.917 0.517 17.4 845.1 Flood Risk 240 min Summer 9.925 0.525 17.5 859.9 Flood Risk 360 min Summer 9.922 0.522 17.5 854.3 Flood Risk 480 min Summer 9.913 0.513 17.4 837.4 Flood Risk 600 min Summer 9.902 0.502 17.3 819.2 Flood Risk 720 min Summer 9.891 0.491 17.2 800.2 Flood Risk 960 min Summer 9.869 0.469 17.1 762.5 Flood Risk 1440 min Summer 9.827 0.427 16.7 690.4 Flood Risk 2160 min Summer 9.769 0.369 16.3 591.6 Flood Risk 2880 min Summer 9.716 0.316 15.9 503.1 Flood Risk 4320 min Summer 9.626 0.226 15.2 354.9 O K 5760 min Summer 9.556 0.156 14.6 242.8 O K 7200 min Summer 9.505 0.105 14.2 161.9 O K 8640 min Summer 9.470 0.070 14.0 108.3 O K 10080 min Summer 9.452 0.052 13.8 79.6 O K 15 min Winter 9.711 0.311 15.8 494.9 Flood Risk 30 min Winter 9.799 0.399 16.5 642.7 Flood Risk 60 min Winter 9.883 0.483 17.2 785.8 Flood Risk 120 min Winter 9.954 0.554 17.7 910.4 Flood Risk 180 min Winter 9.984 0.584 18.0 963.6 Flood Risk

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

15 min Summer 134.372 0.0 19 30 min Summer 88.266 0.0 33 60 min Summer 55.250 0.0 64 120 min Summer 33.426 0.0 122 180 min Summer 24.587 0.0 182 240 min Summer 19.657 0.0 242 360 min Summer 14.271 0.0 358 480 min Summer 11.374 0.0 408 600 min Summer 9.532 0.0 470 720 min Summer 8.247 0.0 532 960 min Summer 6.558 0.0 664 1440 min Summer 4.740 0.0 938 2160 min Summer 3.420 0.0 1344 2880 min Summer 2.711 0.0 1732 4320 min Summer 1.951 0.0 2504 5760 min Summer 1.543 0.0 3176 7200 min Summer 1.286 0.0 3888 8640 min Summer 1.107 0.0 4504 10080 min Summer 0.976 0.0 5144 15 min Winter 134.372 0.0 19 30 min Winter 88.266 0.0 33 60 min Winter 55.250 0.0 62 120 min Winter 33.426 0.0 120 180 min Winter 24.587 0.0 178

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin Norwich NR7 0EP 0.6m Deep Date 06/06/2018 10:06 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.6m...XP Solutions Source Control 2016.1.1

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)

240 min Winter 9.997 0.597 18.1 986.1 Flood Risk 360 min Winter 10.000 0.600 18.1 991.6 Flood Risk 480 min Winter 9.991 0.591 18.0 975.7 Flood Risk 600 min Winter 9.976 0.576 17.9 949.3 Flood Risk 720 min Winter 9.964 0.564 17.8 927.0 Flood Risk 960 min Winter 9.936 0.536 17.6 877.7 Flood Risk 1440 min Winter 9.876 0.476 17.1 774.1 Flood Risk 2160 min Winter 9.790 0.390 16.4 627.1 Flood Risk 2880 min Winter 9.712 0.312 15.8 496.5 Flood Risk 4320 min Winter 9.583 0.183 14.8 286.4 O K 5760 min Winter 9.492 0.092 14.1 141.4 O K 7200 min Winter 9.449 0.049 13.6 75.4 O K 8640 min Winter 9.443 0.043 11.8 65.2 O K 10080 min Winter 9.438 0.038 10.4 57.5 O K

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

240 min Winter 19.657 0.0 236 360 min Winter 14.271 0.0 348 480 min Winter 11.374 0.0 454 600 min Winter 9.532 0.0 502 720 min Winter 8.247 0.0 566 960 min Winter 6.558 0.0 720 1440 min Winter 4.740 0.0 1024 2160 min Winter 3.420 0.0 1452 2880 min Winter 2.711 0.0 1848 4320 min Winter 1.951 0.0 2596 5760 min Winter 1.543 0.0 3232 7200 min Winter 1.286 0.0 3672 8640 min Winter 1.107 0.0 4392 10080 min Winter 0.976 0.0 5136

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin Norwich NR7 0EP 0.6m Deep Date 06/06/2018 10:06 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.6m...XP Solutions Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin Norwich NR7 0EP 0.6m Deep Date 06/06/2018 10:06 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.6m...XP Solutions Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Infiltration Basin Structure

Invert Level (m) 9.400 Safety Factor 5.0 Infiltration Coefficient Base (m/hr) 0.15840 Porosity 1.00 Infiltration Coefficient Side (m/hr) 0.15840

Depth (m) Area (m²) Depth (m) Area (m²)

0.000 1525.0 0.600 1784.4

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164-Horsford Thorpe St Andrew Infiltration Basin_1-in-30 Norwich NR7 0EP 0.6m Deep Date 06/06/2018 10:24 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.6m...XP Solutions Source Control 2016.1.1

Summary of Results for 30 year Return Period (+40%)

Half Drain Time : 1651 minutes.

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

15 min Summer 9.617 0.217 4.5 346.2 O K 30 min Summer 9.679 0.279 4.7 448.6 O K 60 min Summer 9.741 0.341 4.8 553.5 Flood Risk 120 min Summer 9.802 0.402 5.0 658.0 Flood Risk 180 min Summer 9.836 0.436 5.0 716.1 Flood Risk 240 min Summer 9.858 0.458 5.1 754.1 Flood Risk 360 min Summer 9.885 0.485 5.2 801.7 Flood Risk 480 min Summer 9.901 0.501 5.2 830.8 Flood Risk 600 min Summer 9.911 0.511 5.2 848.6 Flood Risk 720 min Summer 9.917 0.517 5.2 859.0 Flood Risk 960 min Summer 9.921 0.521 5.2 865.8 Flood Risk 1440 min Summer 9.913 0.513 5.2 850.9 Flood Risk 2160 min Summer 9.895 0.495 5.2 820.3 Flood Risk 2880 min Summer 9.877 0.477 5.1 788.2 Flood Risk 4320 min Summer 9.841 0.441 5.1 725.3 Flood Risk 5760 min Summer 9.807 0.407 5.0 666.0 Flood Risk 7200 min Summer 9.774 0.374 4.9 609.8 Flood Risk 8640 min Summer 9.743 0.343 4.8 557.1 Flood Risk 10080 min Summer 9.714 0.314 4.8 507.5 Flood Risk 15 min Winter 9.642 0.242 4.6 388.0 O K 30 min Winter 9.711 0.311 4.7 503.1 Flood Risk 60 min Winter 9.781 0.381 4.9 621.3 Flood Risk 120 min Winter 9.850 0.450 5.1 740.1 Flood Risk 180 min Winter 9.888 0.488 5.2 806.8 Flood Risk

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

15 min Summer 103.633 0.0 19 30 min Summer 67.486 0.0 34 60 min Summer 42.036 0.0 64 120 min Summer 25.426 0.0 124 180 min Summer 18.752 0.0 184 240 min Summer 15.046 0.0 242 360 min Summer 10.991 0.0 362 480 min Summer 8.795 0.0 482 600 min Summer 7.394 0.0 602 720 min Summer 6.414 0.0 722 960 min Summer 5.123 0.0 960 1440 min Summer 3.728 0.0 1284 2160 min Summer 2.709 0.0 1660 2880 min Summer 2.159 0.0 2044 4320 min Summer 1.566 0.0 2856 5760 min Summer 1.247 0.0 3688 7200 min Summer 1.044 0.0 4472 8640 min Summer 0.903 0.0 5272 10080 min Summer 0.798 0.0 6056 15 min Winter 103.633 0.0 19 30 min Winter 67.486 0.0 34 60 min Winter 42.036 0.0 64 120 min Winter 25.426 0.0 122 180 min Winter 18.752 0.0 180

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164-Horsford Thorpe St Andrew Infiltration Basin_1-in-30 Norwich NR7 0EP 0.6m Deep Date 06/06/2018 10:24 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.6m...XP Solutions Source Control 2016.1.1

Summary of Results for 30 year Return Period (+40%)

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

240 min Winter 9.913 0.513 5.2 851.0 Flood Risk 360 min Winter 9.945 0.545 5.3 907.6 Flood Risk 480 min Winter 9.965 0.565 5.3 943.6 Flood Risk 600 min Winter 9.978 0.578 5.4 967.1 Flood Risk 720 min Winter 9.986 0.586 5.4 982.2 Flood Risk 960 min Winter 9.994 0.594 5.4 997.0 Flood Risk 1440 min Winter 9.991 0.591 5.4 991.8 Flood Risk 2160 min Winter 9.969 0.569 5.4 950.8 Flood Risk 2880 min Winter 9.946 0.546 5.3 910.7 Flood Risk 4320 min Winter 9.896 0.496 5.2 821.9 Flood Risk 5760 min Winter 9.846 0.446 5.1 733.2 Flood Risk 7200 min Winter 9.797 0.397 4.9 649.0 Flood Risk 8640 min Winter 9.751 0.351 4.8 570.1 Flood Risk 10080 min Winter 9.708 0.308 4.7 496.9 Flood Risk

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

240 min Winter 15.046 0.0 240 360 min Winter 10.991 0.0 358 480 min Winter 8.795 0.0 474 600 min Winter 7.394 0.0 590 720 min Winter 6.414 0.0 706 960 min Winter 5.123 0.0 932 1440 min Winter 3.728 0.0 1370 2160 min Winter 2.709 0.0 1748 2880 min Winter 2.159 0.0 2192 4320 min Winter 1.566 0.0 3112 5760 min Winter 1.247 0.0 3984 7200 min Winter 1.044 0.0 4832 8640 min Winter 0.903 0.0 5704 10080 min Winter 0.798 0.0 6456

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164-Horsford Thorpe St Andrew Infiltration Basin_1-in-30 Norwich NR7 0EP 0.6m Deep Date 06/06/2018 10:24 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.6m...XP Solutions Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164-Horsford Thorpe St Andrew Infiltration Basin_1-in-30 Norwich NR7 0EP 0.6m Deep Date 06/06/2018 10:24 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.6m...XP Solutions Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Infiltration Basin Structure

Invert Level (m) 9.400 Safety Factor 5.0 Infiltration Coefficient Base (m/hr) 0.04680 Porosity 1.00 Infiltration Coefficient Side (m/hr) 0.04680

Depth (m) Area (m²) Depth (m) Area (m²)

0.000 1550.0 0.600 1811.4

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_Lower Rate Norwich NR7 0EP 0.6m Deep Date 06/06/2018 10:15 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.6m...XP Solutions Source Control 2016.1.1

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

Half Drain Time : 1690 minutes.

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

15 min Summer 9.619 0.219 5.8 448.9 O K 30 min Summer 9.684 0.284 5.9 586.9 O K 60 min Summer 9.749 0.349 6.1 728.0 Flood Risk 120 min Summer 9.812 0.412 6.3 866.1 Flood Risk 180 min Summer 9.846 0.446 6.4 940.4 Flood Risk 240 min Summer 9.867 0.467 6.4 987.1 Flood Risk 360 min Summer 9.892 0.492 6.5 1043.4 Flood Risk 480 min Summer 9.907 0.507 6.5 1077.4 Flood Risk 600 min Summer 9.916 0.516 6.6 1097.2 Flood Risk 720 min Summer 9.921 0.521 6.6 1107.9 Flood Risk 960 min Summer 9.923 0.523 6.6 1111.8 Flood Risk 1440 min Summer 9.911 0.511 6.5 1084.3 Flood Risk 2160 min Summer 9.889 0.489 6.5 1035.3 Flood Risk 2880 min Summer 9.867 0.467 6.4 987.2 Flood Risk 4320 min Summer 9.826 0.426 6.3 896.9 Flood Risk 5760 min Summer 9.789 0.389 6.2 813.8 Flood Risk 7200 min Summer 9.753 0.353 6.1 736.8 Flood Risk 8640 min Summer 9.720 0.320 6.0 665.2 Flood Risk 10080 min Summer 9.689 0.289 6.0 598.6 O K 15 min Winter 9.644 0.244 5.8 503.2 O K 30 min Winter 9.717 0.317 6.0 658.2 Flood Risk 60 min Winter 9.790 0.390 6.2 817.1 Flood Risk 120 min Winter 9.861 0.461 6.4 974.1 Flood Risk 180 min Winter 9.899 0.499 6.5 1059.5 Flood Risk

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

15 min Summer 134.372 0.0 19 30 min Summer 88.266 0.0 34 60 min Summer 55.250 0.0 64 120 min Summer 33.426 0.0 124 180 min Summer 24.587 0.0 184 240 min Summer 19.657 0.0 242 360 min Summer 14.271 0.0 362 480 min Summer 11.374 0.0 482 600 min Summer 9.532 0.0 602 720 min Summer 8.247 0.0 722 960 min Summer 6.558 0.0 960 1440 min Summer 4.740 0.0 1312 2160 min Summer 3.420 0.0 1664 2880 min Summer 2.711 0.0 2044 4320 min Summer 1.951 0.0 2856 5760 min Summer 1.543 0.0 3688 7200 min Summer 1.286 0.0 4472 8640 min Summer 1.107 0.0 5272 10080 min Summer 0.976 0.0 6048 15 min Winter 134.372 0.0 19 30 min Winter 88.266 0.0 34 60 min Winter 55.250 0.0 64 120 min Winter 33.426 0.0 122 180 min Winter 24.587 0.0 180

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_Lower Rate Norwich NR7 0EP 0.6m Deep Date 06/06/2018 10:15 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.6m...XP Solutions Source Control 2016.1.1

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)

240 min Winter 9.924 0.524 6.6 1113.9 Flood Risk 360 min Winter 9.953 0.553 6.7 1181.1 Flood Risk 480 min Winter 9.972 0.572 6.7 1223.5 Flood Risk 600 min Winter 9.984 0.584 6.7 1250.2 Flood Risk 720 min Winter 9.991 0.591 6.8 1266.7 Flood Risk 960 min Winter 9.997 0.597 6.8 1280.2 Flood Risk 1440 min Winter 9.990 0.590 6.8 1264.7 Flood Risk 2160 min Winter 9.962 0.562 6.7 1200.8 Flood Risk 2880 min Winter 9.936 0.536 6.6 1141.3 Flood Risk 4320 min Winter 9.880 0.480 6.5 1015.6 Flood Risk 5760 min Winter 9.825 0.425 6.3 893.7 Flood Risk 7200 min Winter 9.773 0.373 6.2 779.4 Flood Risk 8640 min Winter 9.724 0.324 6.0 673.6 Flood Risk 10080 min Winter 9.679 0.279 5.9 576.6 O K

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

240 min Winter 19.657 0.0 240 360 min Winter 14.271 0.0 358 480 min Winter 11.374 0.0 474 600 min Winter 9.532 0.0 590 720 min Winter 8.247 0.0 706 960 min Winter 6.558 0.0 932 1440 min Winter 4.740 0.0 1370 2160 min Winter 3.420 0.0 1752 2880 min Winter 2.711 0.0 2192 4320 min Winter 1.951 0.0 3112 5760 min Winter 1.543 0.0 3984 7200 min Winter 1.286 0.0 4832 8640 min Winter 1.107 0.0 5624 10080 min Winter 0.976 0.0 6456

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_Lower Rate Norwich NR7 0EP 0.6m Deep Date 06/06/2018 10:15 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.6m...XP Solutions Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_Lower Rate Norwich NR7 0EP 0.6m Deep Date 06/06/2018 10:15 AM Designed by MJWH File Infiltration Basin Sizing Checked by 0.6m...XP Solutions Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Infiltration Basin Structure

Invert Level (m) 9.400 Safety Factor 5.0 Infiltration Coefficient Base (m/hr) 0.04680 Porosity 1.00 Infiltration Coefficient Side (m/hr) 0.04680

Depth (m) Area (m²) Depth (m) Area (m²)

0.000 2000.0 0.600 2295.5

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin Norwich NR7 0EP 2.0m Deep Date 06/06/2018 10:09 AM Designed by MJWH File Infiltration Basin Sizing 2m Checked by D...XP Solutions Source Control 2016.1.1

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

Half Drain Time : 947 minutes.

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

15 min Summer 8.943 0.943 7.4 447.8 O K 30 min Summer 9.164 1.164 8.5 584.2 O K 60 min Summer 9.368 1.368 9.5 721.6 O K 120 min Summer 9.546 1.546 10.4 851.3 O K 180 min Summer 9.632 1.632 10.8 916.9 O K 240 min Summer 9.679 1.679 11.0 954.6 O K 360 min Summer 9.726 1.726 11.3 992.1 Flood Risk 480 min Summer 9.745 1.745 11.4 1007.5 Flood Risk 600 min Summer 9.747 1.747 11.4 1009.2 Flood Risk 720 min Summer 9.742 1.742 11.4 1004.9 Flood Risk 960 min Summer 9.730 1.730 11.3 994.7 Flood Risk 1440 min Summer 9.694 1.694 11.1 966.1 O K 2160 min Summer 9.626 1.626 10.8 912.9 O K 2880 min Summer 9.554 1.554 10.4 857.5 O K 4320 min Summer 9.421 1.421 9.7 759.5 O K 5760 min Summer 9.307 1.307 9.2 679.3 O K 7200 min Summer 9.205 1.205 8.7 610.8 O K 8640 min Summer 9.113 1.113 8.3 551.6 O K 10080 min Summer 9.030 1.030 7.9 499.8 O K 15 min Winter 9.033 1.033 7.9 502.0 O K 30 min Winter 9.272 1.272 9.0 655.3 O K 60 min Winter 9.491 1.491 10.1 810.2 O K 120 min Winter 9.684 1.684 11.1 958.0 O K 180 min Winter 9.778 1.778 11.5 1033.8 Flood Risk

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

15 min Summer 134.372 0.0 19 30 min Summer 88.266 0.0 34 60 min Summer 55.250 0.0 64 120 min Summer 33.426 0.0 122 180 min Summer 24.587 0.0 182 240 min Summer 19.657 0.0 242 360 min Summer 14.271 0.0 362 480 min Summer 11.374 0.0 480 600 min Summer 9.532 0.0 600 720 min Summer 8.247 0.0 656 960 min Summer 6.558 0.0 768 1440 min Summer 4.740 0.0 1024 2160 min Summer 3.420 0.0 1444 2880 min Summer 2.711 0.0 1848 4320 min Summer 1.951 0.0 2680 5760 min Summer 1.543 0.0 3464 7200 min Summer 1.286 0.0 4248 8640 min Summer 1.107 0.0 5016 10080 min Summer 0.976 0.0 5752 15 min Winter 134.372 0.0 19 30 min Winter 88.266 0.0 33 60 min Winter 55.250 0.0 62 120 min Winter 33.426 0.0 122 180 min Winter 24.587 0.0 180

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin Norwich NR7 0EP 2.0m Deep Date 06/06/2018 10:09 AM Designed by MJWH File Infiltration Basin Sizing 2m Checked by D...XP Solutions Source Control 2016.1.1

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)

240 min Winter 9.831 1.831 11.8 1078.3 Flood Risk 360 min Winter 9.887 1.887 12.1 1125.4 Flood Risk 480 min Winter 9.913 1.913 12.2 1148.0 Flood Risk 600 min Winter 9.922 1.922 12.3 1155.7 Flood Risk 720 min Winter 9.920 1.920 12.3 1154.1 Flood Risk 960 min Winter 9.899 1.899 12.2 1136.0 Flood Risk 1440 min Winter 9.858 1.858 12.0 1100.9 Flood Risk 2160 min Winter 9.772 1.772 11.5 1029.6 Flood Risk 2880 min Winter 9.678 1.678 11.0 953.6 O K 4320 min Winter 9.495 1.495 10.1 813.3 O K 5760 min Winter 9.337 1.337 9.3 700.4 O K 7200 min Winter 9.199 1.199 8.7 607.2 O K 8640 min Winter 9.077 1.077 8.1 528.8 O K 10080 min Winter 8.967 0.967 7.6 462.2 O K

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

240 min Winter 19.657 0.0 238 360 min Winter 14.271 0.0 354 480 min Winter 11.374 0.0 466 600 min Winter 9.532 0.0 578 720 min Winter 8.247 0.0 684 960 min Winter 6.558 0.0 866 1440 min Winter 4.740 0.0 1094 2160 min Winter 3.420 0.0 1556 2880 min Winter 2.711 0.0 1992 4320 min Winter 1.951 0.0 2856 5760 min Winter 1.543 0.0 3688 7200 min Winter 1.286 0.0 4472 8640 min Winter 1.107 0.0 5272 10080 min Winter 0.976 0.0 6048

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin Norwich NR7 0EP 2.0m Deep Date 06/06/2018 10:09 AM Designed by MJWH File Infiltration Basin Sizing 2m Checked by D...XP Solutions Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin Norwich NR7 0EP 2.0m Deep Date 06/06/2018 10:09 AM Designed by MJWH File Infiltration Basin Sizing 2m Checked by D...XP Solutions Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Infiltration Basin Structure

Invert Level (m) 8.000 Safety Factor 5.0 Infiltration Coefficient Base (m/hr) 0.15840 Porosity 1.00 Infiltration Coefficient Side (m/hr) 0.15840

Depth (m) Area (m²) Depth (m) Area (m²)

0.000 370.0 2.000 892.2

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_1-in-30 Norwich NR7 0EP 2.0m Deep Date 06/06/2018 10:26 AM Designed by MJWH File Infiltration Basin Sizing 2m Checked by D...XP Solutions Source Control 2016.1.1

Summary of Results for 30 year Return Period (+40%)

Half Drain Time : 3218 minutes.

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

15 min Summer 8.800 0.800 1.9 348.3 O K 30 min Summer 8.989 0.989 2.2 452.5 O K 60 min Summer 9.171 1.171 2.4 561.2 O K 120 min Summer 9.344 1.344 2.7 673.2 O K 180 min Summer 9.441 1.441 2.8 738.8 O K 240 min Summer 9.505 1.505 2.9 784.2 O K 360 min Summer 9.591 1.591 3.0 846.4 O K 480 min Summer 9.649 1.649 3.1 890.0 O K 600 min Summer 9.691 1.691 3.2 922.1 O K 720 min Summer 9.723 1.723 3.2 946.6 Flood Risk 960 min Summer 9.767 1.767 3.3 980.7 Flood Risk 1440 min Summer 9.809 1.809 3.4 1014.6 Flood Risk 2160 min Summer 9.819 1.819 3.4 1022.9 Flood Risk 2880 min Summer 9.813 1.813 3.4 1017.4 Flood Risk 4320 min Summer 9.790 1.790 3.3 999.2 Flood Risk 5760 min Summer 9.758 1.758 3.3 974.3 Flood Risk 7200 min Summer 9.722 1.722 3.2 945.5 Flood Risk 8640 min Summer 9.682 1.682 3.2 915.2 O K 10080 min Summer 9.643 1.643 3.1 885.1 O K 15 min Winter 8.878 0.878 2.0 390.2 O K 30 min Winter 9.082 1.082 2.3 507.1 O K 60 min Winter 9.277 1.277 2.6 629.0 O K 120 min Winter 9.464 1.464 2.8 755.1 O K 180 min Winter 9.567 1.567 3.0 829.2 O K

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

15 min Summer 103.633 0.0 19 30 min Summer 67.486 0.0 34 60 min Summer 42.036 0.0 64 120 min Summer 25.426 0.0 124 180 min Summer 18.752 0.0 184 240 min Summer 15.046 0.0 244 360 min Summer 10.991 0.0 364 480 min Summer 8.795 0.0 482 600 min Summer 7.394 0.0 602 720 min Summer 6.414 0.0 722 960 min Summer 5.123 0.0 962 1440 min Summer 3.728 0.0 1442 2160 min Summer 2.709 0.0 2100 2880 min Summer 2.159 0.0 2420 4320 min Summer 1.566 0.0 3156 5760 min Summer 1.247 0.0 3976 7200 min Summer 1.044 0.0 4824 8640 min Summer 0.903 0.0 5624 10080 min Summer 0.798 0.0 6456 15 min Winter 103.633 0.0 19 30 min Winter 67.486 0.0 34 60 min Winter 42.036 0.0 64 120 min Winter 25.426 0.0 122 180 min Winter 18.752 0.0 182

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_1-in-30 Norwich NR7 0EP 2.0m Deep Date 06/06/2018 10:26 AM Designed by MJWH File Infiltration Basin Sizing 2m Checked by D...XP Solutions Source Control 2016.1.1

Summary of Results for 30 year Return Period (+40%)

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

240 min Winter 9.637 1.637 3.1 880.6 O K 360 min Winter 9.729 1.729 3.2 951.6 Flood Risk 480 min Winter 9.793 1.793 3.3 1001.6 Flood Risk 600 min Winter 9.839 1.839 3.4 1038.9 Flood Risk 720 min Winter 9.874 1.874 3.4 1067.6 Flood Risk 960 min Winter 9.924 1.924 3.5 1108.7 Flood Risk 1440 min Winter 9.976 1.976 3.6 1152.8 Flood Risk 2160 min Winter 9.999 1.999 3.6 1172.3 Flood Risk 2880 min Winter 9.991 1.991 3.6 1165.7 Flood Risk 4320 min Winter 9.960 1.960 3.6 1139.3 Flood Risk 5760 min Winter 9.920 1.920 3.5 1105.8 Flood Risk 7200 min Winter 9.872 1.872 3.4 1066.0 Flood Risk 8640 min Winter 9.821 1.821 3.4 1023.9 Flood Risk 10080 min Winter 9.768 1.768 3.3 981.7 Flood Risk

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

240 min Winter 15.046 0.0 240 360 min Winter 10.991 0.0 358 480 min Winter 8.795 0.0 476 600 min Winter 7.394 0.0 594 720 min Winter 6.414 0.0 712 960 min Winter 5.123 0.0 944 1440 min Winter 3.728 0.0 1400 2160 min Winter 2.709 0.0 2072 2880 min Winter 2.159 0.0 2680 4320 min Winter 1.566 0.0 3332 5760 min Winter 1.247 0.0 4264 7200 min Winter 1.044 0.0 5184 8640 min Winter 0.903 0.0 6056 10080 min Winter 0.798 0.0 6960

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_1-in-30 Norwich NR7 0EP 2.0m Deep Date 06/06/2018 10:26 AM Designed by MJWH File Infiltration Basin Sizing 2m Checked by D...XP Solutions Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_1-in-30 Norwich NR7 0EP 2.0m Deep Date 06/06/2018 10:26 AM Designed by MJWH File Infiltration Basin Sizing 2m Checked by D...XP Solutions Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Infiltration Basin Structure

Invert Level (m) 8.000 Safety Factor 5.0 Infiltration Coefficient Base (m/hr) 0.04680 Porosity 1.00 Infiltration Coefficient Side (m/hr) 0.04680

Depth (m) Area (m²) Depth (m) Area (m²)

0.000 350.0 2.000 861.0

©1982-2016 XP Solutions Canham Consulting Ltd Page 1 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_Lower Rate Norwich NR7 0EP 2.0m Deep Date 06/06/2018 10:18 AM Designed by MJWH File Infiltration Basin Sizing 2m Checked by D...XP Solutions Source Control 2016.1.1

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

Half Drain Time : 3425 minutes.

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

15 min Summer 8.783 0.783 2.4 451.6 O K 30 min Summer 8.981 0.981 2.7 592.0 O K 60 min Summer 9.172 1.172 3.0 738.0 O K 120 min Summer 9.353 1.353 3.3 885.9 O K 180 min Summer 9.450 1.450 3.4 970.0 O K 240 min Summer 9.514 1.514 3.5 1026.4 O K 360 min Summer 9.597 1.597 3.7 1101.7 O K 480 min Summer 9.653 1.653 3.8 1154.7 O K 600 min Summer 9.694 1.694 3.8 1193.3 O K 720 min Summer 9.724 1.724 3.9 1222.5 Flood Risk 960 min Summer 9.766 1.766 3.9 1262.5 Flood Risk 1440 min Summer 9.804 1.804 4.0 1300.4 Flood Risk 2160 min Summer 9.809 1.809 4.0 1305.4 Flood Risk 2880 min Summer 9.793 1.793 4.0 1289.5 Flood Risk 4320 min Summer 9.757 1.757 3.9 1253.9 Flood Risk 5760 min Summer 9.715 1.715 3.9 1213.5 Flood Risk 7200 min Summer 9.670 1.670 3.8 1170.2 O K 8640 min Summer 9.623 1.623 3.7 1126.4 O K 10080 min Summer 9.577 1.577 3.6 1083.8 O K 15 min Winter 8.861 0.861 2.5 506.0 O K 30 min Winter 9.076 1.076 2.8 663.4 O K 60 min Winter 9.283 1.283 3.2 827.2 O K 120 min Winter 9.477 1.477 3.5 993.6 O K 180 min Winter 9.582 1.582 3.6 1088.6 O K

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

15 min Summer 134.372 0.0 19 30 min Summer 88.266 0.0 34 60 min Summer 55.250 0.0 64 120 min Summer 33.426 0.0 124 180 min Summer 24.587 0.0 184 240 min Summer 19.657 0.0 244 360 min Summer 14.271 0.0 364 480 min Summer 11.374 0.0 482 600 min Summer 9.532 0.0 602 720 min Summer 8.247 0.0 722 960 min Summer 6.558 0.0 962 1440 min Summer 4.740 0.0 1442 2160 min Summer 3.420 0.0 2160 2880 min Summer 2.711 0.0 2480 4320 min Summer 1.951 0.0 3240 5760 min Summer 1.543 0.0 4032 7200 min Summer 1.286 0.0 4832 8640 min Summer 1.107 0.0 5704 10080 min Summer 0.976 0.0 6464 15 min Winter 134.372 0.0 19 30 min Winter 88.266 0.0 34 60 min Winter 55.250 0.0 64 120 min Winter 33.426 0.0 122 180 min Winter 24.587 0.0 182

©1982-2016 XP Solutions Canham Consulting Ltd Page 2 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_Lower Rate Norwich NR7 0EP 2.0m Deep Date 06/06/2018 10:18 AM Designed by MJWH File Infiltration Basin Sizing 2m Checked by D...XP Solutions Source Control 2016.1.1

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)

240 min Winter 9.651 1.651 3.8 1152.6 O K 360 min Winter 9.741 1.741 3.9 1238.6 Flood Risk 480 min Winter 9.803 1.803 4.0 1299.5 Flood Risk 600 min Winter 9.848 1.848 4.1 1344.5 Flood Risk 720 min Winter 9.882 1.882 4.1 1378.8 Flood Risk 960 min Winter 9.929 1.929 4.2 1427.1 Flood Risk 1440 min Winter 9.977 1.977 4.3 1477.1 Flood Risk 2160 min Winter 9.994 1.994 4.3 1495.3 Flood Risk 2880 min Winter 9.981 1.981 4.3 1481.8 Flood Risk 4320 min Winter 9.935 1.935 4.2 1433.7 Flood Risk 5760 min Winter 9.887 1.887 4.1 1383.5 Flood Risk 7200 min Winter 9.831 1.831 4.1 1327.1 Flood Risk 8640 min Winter 9.772 1.772 4.0 1269.1 Flood Risk 10080 min Winter 9.713 1.713 3.9 1211.4 Flood Risk

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

240 min Winter 19.657 0.0 240 360 min Winter 14.271 0.0 360 480 min Winter 11.374 0.0 478 600 min Winter 9.532 0.0 596 720 min Winter 8.247 0.0 712 960 min Winter 6.558 0.0 944 1440 min Winter 4.740 0.0 1400 2160 min Winter 3.420 0.0 2076 2880 min Winter 2.711 0.0 2708 4320 min Winter 1.951 0.0 3372 5760 min Winter 1.543 0.0 4320 7200 min Winter 1.286 0.0 5256 8640 min Winter 1.107 0.0 6136 10080 min Winter 0.976 0.0 7056

©1982-2016 XP Solutions Canham Consulting Ltd Page 3 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_Lower Rate Norwich NR7 0EP 2.0m Deep Date 06/06/2018 10:18 AM Designed by MJWH File Infiltration Basin Sizing 2m Checked by D...XP Solutions Source Control 2016.1.1

Rainfall Details

Time Area Diagram

Total Area (ha) 1.800

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

0 4 1.800

©1982-2016 XP Solutions Canham Consulting Ltd Page 4 The Old School 206164 - Horsford Thorpe St Andrew Infiltration Basin_Lower Rate Norwich NR7 0EP 2.0m Deep Date 06/06/2018 10:18 AM Designed by MJWH File Infiltration Basin Sizing 2m Checked by D...XP Solutions Source Control 2016.1.1

Model Details

Storage is Online Cover Level (m) 10.000

Infiltration Basin Structure

Invert Level (m) 8.000 Safety Factor 5.0 Infiltration Coefficient Base (m/hr) 0.04680 Porosity 1.00 Infiltration Coefficient Side (m/hr) 0.04680

Depth (m) Area (m²) Depth (m) Area (m²)

0.000 480.0 2.000 1059.1

Flood Risk Assessment – Land off Holt Road, Horsford June 2018 Issue P1 206164

APPENDIX G Maintenance Strategy

Maintenance Strategy

on:

Land off Holt Road, Horsford

for:

Carl Palmer

Land off Hold Road, Horsford Maintenance Strategy 206164

Contents Amendment Record This report has been issued and amended as follows:

Rev Description Prepared Reviewed Date P1 First Issue MJWH MEH 05/06/2018

Canham Consulting Ltd The Old School School Lane Thorpe St. Andrew Norwich NR7 0EP

T: 01603 430650 F: 01603 430672 [email protected] www.canhamconsulting.co.uk

SuDS Maintenance Strategy – Land off Holt Road, Horsford 206164 Issue P1 June 2018

CONTENTS

1 INTRODUCTION ...... 1 2 SUDS COMPONENTS ON THE SITE ...... 1 3 SUMMARY OF DESIGN INTENT...... 2 4 INSPECTIONS ...... 3 5 OPERATION AND MAINTENANCE REQUIREMENTS FOR INFILTRATION BASIN ...... 4 6 OPERATION AND MAINTENANCE REQUIREMENTS FOR ATTENUATION TANKS ...... 5 7 OPERATION AND MAINTENANCE REQUIREMENTS FOR AN ATTENUATION BASIN ..... 6 8 OPERATION AND MAINTENANCE REQUIREMENTS FOR PERMEABLE PAVING ...... 7 9 OPERATION AND MAINTENANCE REQUIRED FOR FILTER DRAINS ...... 8 10 OPERATION AND MAINTENANCE REQUIRED FOR GULLIES AND CHANNEL DRAINS .. 9 11 EMERGENCY ACTION IN CASE OF SPILLAGES ...... 10

Appendices

Appendix A - SuDS Maintenance Inspection Checklist

SuDS Maintenance Strategy – Land off Holt Road, Horsford 206164 Issue P1 June 2018

1 INTRODUCTION

This SuDS Operation and Maintenance Strategy has been produced in line with the recommendations of the CIRIA SuDS Manual (C753) and includes a number of extracts from that document.

For further information please refer to the full document, which can be downloaded free of charge at: http://www.ciria.org/Resources/Free_publications/SuDS_manual_C753.aspx

In addition to the recommendations in this manual, please also refer to the specific maintenance guidelines provided by the manufacturers of any proprietary products that have been used in the construction of the SuDS.

2 SUDS COMPONENTS ON THE SITE

The site contains a number of SuDS components that will require on-going inspection and maintenance. The primary components are as follows:

 Infiltration Basin (a dry basin designed to promote infiltration of surface water to the ground)

 Attenuation Tank (a purpose-built system, designed to store rainwater during high intensity storms);

 Attenuation Basin (a purpose-built basin, designed to store rainwater in high intensity storms);

 Permeable paving (infiltration and/or treatment only) (a surface suitable for pedestrian and/or vehicular traffic, that provides a treatment medium and allows rainwater to be temporarily stored);

 Filter Drain (a linear drain consisting of a trench filled with a permeable material, often with a perforated pipe in the base of the trench to assist drainage. For treatment of surface water)

 Gullies & channel drains (grated openings in the road surface to collect rainwater)

SuDS Maintenance Strategy – Land off Holt Road, Horsford 206164 Issue P1 June 2018

3 SUMMARY OF DESIGN INTENT

SuDS will be utilised across the site to manage all surface water. A site inspection found infiltration rates at the site limited the viability of infiltration-based SuDS. However, it has been demonstrated that infiltration systems can manage the sites surface water during a 1 in 100 year storm event with 40% climate change.

Two attenuation options were also considered alongside the infiltration basin as fall-back options in case further site investigation proved infiltration systems were not suitable. If an attenuation option was required, further work still needs to be given to the outfall point for the site as there is neither a surface water sewer or watercourse nearby.

SuDS Maintenance Strategy – Land off Holt Road, Horsford 206164 Issue P1 June 2018

4 INSPECTIONS

As part of the on-going management of most SuDS components there is a need for regular inspections to ensure that blockages, silt and excess litter are not adversely affecting the component or scheme. It is important that this is carried out and time is allowed for corrective action to be taken.

Routine inspections should be carried out once a month for most components, particularly for the first year after installation. This frequency can then be reviewed (and if appropriate reduced). Site managers and/or maintenance company personnel should be used for inspecting SuDS. The advantage being that they have intimate knowledge of the development and visit the site on a frequent basis.

Recurring attendance by the same person ensures monitoring of the drainage system, a rapid response to problems and “ownership” of the SuDS components. The inspections should be recorded on a maintenance record.

SuDS Maintenance Strategy – Land off Holt Road, Horsford 206164 Issue P1 June 2018

5 OPERATION AND MAINTENANCE REQUIREMENTS FOR INFILTRATION BASIN Maintenance Required Action Frequency Schedule

Remove little and debris Monthly

Cut Grass – for spillways and access Monthly (during growing routes season), or as required Half yearly (Spring Cut Grass – meadow grass in and around before nesting seasons basin and autumn) Manage other vegetation and remove Monthly at start, then as nuisance plants required Regular Inspect inlet/outlet for blockages, and clear Monthly Maintenance if required Inspect banksides, structures, pipework Monthly etc. for evidence of physical damage Inspect inlet and facility surface for silt Monthly (for first year), accumulation, establish appropriate silt then annually as removal frequencies required Tidy all dead growth before the start of the Annually growing season Remove sediment from inlet/outlet Annually (or as required) Reseed areas of poor vegetation growth As required Prune and trim any trees and remove Occasional As required cuttings Maintenance Remove sediment from inlet/outlet and Every five years, or as main basin when required required Repair erosion or other damage by As required reseeding or re-turfing Repair/rehabilitation of inlet/outlet As required Remedial Rehabilitation of infiltration surface using Actions scarifying and spiking techniques if As required performance deteriorates Relevel uneven surfaces and reinstate As required design levels Inspect inlets, outlets ad overflows for Monthly blockages, and clear if required. Inspect banksides, structures, pipework Monthly etc for evidence of physical damage. Monitoring Inspect inlets and pre-treatment systems for silt accumulation. Establish appropriate Half yearly silt removal frequencies. Inspect infiltration surfaces for compaction Monthly and ponding.

SuDS Maintenance Strategy – Land off Holt Road, Horsford 206164 Issue P1 June 2018

6 OPERATION AND MAINTENANCE REQUIREMENTS FOR ATTENUATION TANKS Maintenance Required action Typical frequency schedule Inspect and identify any areas that are not Monthly for 3 months, operating correctly. If required, take remedial then annually action Regular Remove debris from the catchment surface maintenance Monthly (where it may cause risks to performance) Remove sediment from pre-treatment Annually (or as structures required) Repair/rehabilitation of inlets, outlets, Remedial Actions As required overflows and vents Inspect/check all inlets, outlets, vents and Monitoring overflows to ensure that they are in good Annually condition and operating as designed

SuDS Maintenance Strategy – Land off Holt Road, Horsford 206164 Issue P1 June 2018

7 OPERATION AND MAINTENANCE REQUIREMENTS FOR AN ATTENUATION BASIN

Maintenance Required Action Frequency Schedule

Remove litter and debris Monthly

Cut Grass – for spillways and access Monthly (during growing routes season), or as required

Manage other vegetation and remove Monthly nuisance plants

Inspect inlet/outlet for blockages, and clear Monthly if required Regular Maintenance Inspect banksides, structures, pipework Monthly etc. for evidence of physical damage

Inspect inlet and facility surface for silt Monthly (for first year), accumulation, establish appropriate silt then annually as required. removal frequencies

Tidy all dead growth before the start of the Annually growing season

Remove sediment from inlet/outlet Annually (or as required)

Reseed areas of poor vegetation growth As required

Prune and trim any trees and remove Every two years, or as Occasional cuttings required Maintenance Remove sediment from inlet/outlet and Every five years, or as main basin when required required

Repair erosion or other damage by As required reseeding or re-turfing

Remedial Actions Repair/rehabilitation of inlet/outlet As required

Relevel uneven surfaces and reinstate As required design levels

SuDS Maintenance Strategy – Land off Holt Road, Horsford 206164 Issue P1 June 2018

8 OPERATION AND MAINTENANCE REQUIREMENTS FOR PERMEABLE PAVING

Maintenance Required action Typical frequency schedule Three times per year at end of winter, mid-summer, after autumn leaf fall, or as required based on site-specific observations of clogging or manufacturers’ Regular Brushing and vacuuming (standard recommendations. Pay particular maintenance cosmetic sweep over whole surface) attention to areas where water runs onto pervious surface from adjacent impermeable areas as this area is most likely to collect the most sediment Stabilise and mow contributing and As required adjacent areas Occasional Removal of weeds or management maintenance using glyphosate applied directly into As required – once per year on the weeds by an applicator rather less frequently used pavements than spraying Remediate any landscaping which, through vegetation maintenance or As required soil slip, has been raised to within 50 mm of the level of the paving Remedial work to any depressions, rutting and cracked or broken blocks Remedial considered detrimental to the As required Actions structural performance or a hazard to users, and replace lost jointing material Every 10 to 15 years or as Rehabilitation of surface and upper required (if infiltration substructure by remedial sweeping performance is reduced due to significant clogging) Monthly for three months after Initial inspection installation Inspect for evidence of poor Three-monthly, 48 h after large operation and/or weed growth – if storms in first six months Monitoring required, take remedial action Inspect silt accumulation rates and establish appropriate brushing Annually frequencies Monitor inspection chambers Annually

SuDS Maintenance Strategy – Land off Holt Road, Horsford 206164 Issue P1 June 2018

9 OPERATION AND MAINTENANCE REQUIRED FOR FILTER DRAINS

Maintenance Required Action Frequency Schedule Litter and debris removal from trench surface, access chambers Monthly (or as required). and pre-treatment devices. Annual (bi-annual the first year) Removal and washing of exposed or when silt is evident on the Regular stones on the trench surface. Maintenance surface. Trimming of any roots that may be Annual (semi-annual the first causing blockages. year). Remove weeds on the trench Monthly (at start, then as surface. required). Removal of sediment from pre- Six monthly. treatment devices. Remove tree roots or trees that As required. Occasional grow close to the trench. Maintenance At locations with high pollution loads, remove surface geotextile Five yearly. and replace, and wash or replace filter media. Clear perforated pipework of As required blockages. Rehabilitate infiltration or filtration As required surfaces. Excavate trench walls to expose clean soils if infiltration Remedial Actions As required performance reduces to unacceptable levels. Inspect inlets, outlets and inspection points for blockages, Monthly clogging, standing water and structural damage. Inspect pre-treatment systems, inlets, trench surfaces and perforated pipework for silt Monitoring Half Yearly accumulation. Establish appropriate silt removal frequencies.

SuDS Maintenance Strategy – Land off Holt Road, Horsford 206164 Issue P1 June 2018

10 OPERATION AND MAINTENANCE REQUIRED FOR GULLIES AND CHANNEL DRAINS

Maintenance Required action Typical frequency schedule Regular Removal of litter and debris. 6 monthly. Maintenance

Change of filter media. As required. Occasional Removal of sediment, oil, grease Maintenance As required. and floatables.

Clear perforated pipework Remedial Actions As required. blockages.

Inspect for evidence of poor Six monthly. operation. Inspect filter media and establish appropriate replacement Six monthly. Monitoring frequencies. Inspect sediment accumulation Monthly during first half year of rates and establish appropriate operation, then every six months. replacement frequencies.

SuDS Maintenance Strategy – Land off Holt Road, Horsford 206164 Issue P1 June 2018

11 EMERGENCY ACTION IN CASE OF SPILLAGES

Most spillages on development sites are of compounds that do not pose a serious risk to the environment if they enter the drainage in a slow and controlled manner with time available for natural breakdown in a treatment system. Therefore, small spillages of substances that are known to be harmful to the environment should be removed where possible using soak mats as recommended by the Environment Agency, with residual spillage allowed to bioremediate in the drainage system.

In the event of a serious spillage, either by volume or of unknown or toxic compounds, then isolate the spillage with soil, turf or fabric and block outlet pipes from chamber(s) downstream of the spillage with a bung(s). (A bung for blocking pipes may be made by wrapping soil or turf in a plastic sheet or closely woven fabric.)

Contact the Environment Agency immediately on the following number.

24-hour incident hotline – 0800 80 70 60

Or if less urgent contact the regional office:

Iceni House, Cobham Road, Ipswich, Suffolk, IP3 9JD. Tel. 03708506506

Queries regarding a design feature – In the event of a concern or failure of a SuDS design feature contact:

Canham Consulting The Old School, School Lane, Thorpe St Andrew, Norwich, NR7 0EP T: (01603) 430650 E: [email protected] W: www.canhamconsulting.co.uk

SuDS Maintenance Strategy – Land off Holt Road, Horsford 206164 Issue P1 June 2018

APPENDIX A

SuDS MAINTENANCE INSPECTION CHECKLIST