flood risk assessment hawkins lane, burton on trent application/625000/62… · flood risk...

Flood Risk Assessment

Hawkins Lane, Burton on TrentTesco Stores Ltd

14 Nov 2014

carole.booth

Text Box

P_2014_01128 Revised Flood Risk Assessment - Part 1 Received 1.12.14

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Pinnacle Consulting Engineers Limited Flood Risk Assessment Revision D 2 Hawkins Lane, Burton

Executive Summary

This Flood Risk Assessment has been completed to support a planning application for commercial development of a site on Hawkins Lane, Burton-upon-Trent, East Staffordshire

Site specific data was provided by the Environment Agency in October 2014. The site is found to be within Flood Zones 2 and 3 but benefits from existing flood defences providing a 1 in 200 year level of protection.

The previous version of this Flood Risk Assessment (FRA) assessed risk based on the results in the SFRA which used modelling based on 10 breach reservoir units and data supplied by the Environment Agency from 2010. However, the modelling within the SFRA has since been superseded and new breach and overtopping analysis has been undertaken. We have therefore modified the data in the FRA to bring it up to date with the additional EA data provided. Minimum Finished Floor Levels have been established to ensure the store remains dry during extreme events. A Flood Evacuation Plan detailing contingency measures has also been prepared to maximise the safety of staff and customers during a major flood event.

The site is considered to pass the sequential test, with all other sites identified being of inadequate size, increased flood risk, recent occupancy or have active planning applications.

The site was not considered viable for infiltrating source control, as the site is located above minor aquifer and alternative SUDS measures have been considered. Surface water discharge rates will be reduced to Greenfield run off rates, by means of permeable paving and underground storage.


CONTENT

1 INTRODUCTION ............................................................................................................................ 5

2 EXISTING SITE CONDITIONS ...................................................................................................... 6

2.1 Site description..................................................................................................................... 6

2.2 Topography .......................................................................................................................... 7

2.3 Geological ground conditions ............................................................................................... 7

2.4 Source Protection Zones ..................................................................................................... 8

3 PROPOSED DEVELOPMENT ....................................................................................................... 9

4 PROBABILITY OF FLOODING .................................................................................................... 10

4.1 Flooding from rivers (fluvial flooding) & sea (tidal flooding) ............................................... 10

4.2 Flooding from land & sewers ............................................................................................. 12

4.3 Flooding from groundwater ................................................................................................ 13

4.4 Flooding from reservoirs, canals, and other artificial sources ........................................... 13

5 POLICY STATUS FOR PROPOSED DEVELOPMENT .............................................................. 15

5.1 Vulnerability classification .................................................................................................. 15

6 SEQUENTIAL TEST & EXCEPTION TEST ................................................................................. 17

6.1 Methodology ....................................................................................................................... 17

6.2 Test Conclusion ................................................................................................................. 19

7 FLOOD RISK MANAGEMENT STRATEGY ................................................................................ 20

7.1 On-Site flood Risk .............................................................................................................. 20

7.2 Residual Risk & Flood Evacuation Strategy ...................................................................... 20

7.3 Finished Floor Levels ......................................................................................................... 20

7.4 Surface water Drainage Strategy ....................................................................................... 20

7.5 Sustainable Drainage Systems (SUDS) ............................................................................ 21

8 CONCLUSION ............................................................................................................................. 22

APPENDIX A – SITE LOCATION PLAN ................................................................................................ 23

APPENDIX B – EXISTING SITE PLAN .................................................................................................. 24

APPENDIX C – EXISTING & PROPOSED IMPERMEABLE AREAS .................................................... 25

APPENDIX D – TOPOGRAPHIC SURVEY ........................................................................................... 26

APPENDIX E – BGS REPORT .............................................................................................................. 27

APPENDIX F – PROPOSED DEVELOPMENT PLANS ........................................................................ 28

APPENDIX G – ENVIRONMENT AGENCY DATA ................................................................................ 29

APPENDIX H – LEVEL 2 SFRA DEVELOPMENT PLAN MAP ............................................................. 30

APPENDIX I – LDP DEVELOPMENT PLAN MAP WITH ALTERNATIVE SITES ................................. 31

APPENDIX J – EA FLOOD MAP FOR PLANNING (RIVERS AND SEAS) WITH ALTERNATIVE AND PROPOSED SITES OUTLINED IN RED ............................................................................................... 32


APPENDIX K – FLOOD EVACUATION PLAN ....................................................................................... 33

APPENDIX L – SEWER RECORDS ...................................................................................................... 34

APPENDIX M – PROPOSED DRAINAGE STRATEGY ........................................................................ 35

APPENDIX N – DRAINAGE CALCULATIONS ...................................................................................... 36


1 INTRODUCTION

Pinnacle Consulting Engineers Ltd have been commissioned by Tesco Stores Ltd to carry out a Flood Risk Assessment report (FRA) for a proposed development of a site off Hawkins Lane, Burton upon Trent, DE14 1PT.

With reference to the indicative flood maps published by the Environment Agency, the site appears to lie in an area at risk of flooding but protected by flood defences. This FRA report has been prepared in accordance with the requirements contained within National Planning Policy Framework (NNPF, March 2012) and the associated Technical Guidance. The guidance refers to the Environment Agency’s “standing advice” on flood risk. Based on requirements set by the Environment Agency, a Flood Risk assessment is needed to support the planning application.

It is stated in Paragraph 9 of the Technical Guidance to the National Planning Policy Framework that “...local planning authorities should only consider development in flood risk areas appropriate where informed by a site-specific flood risk assessment. This should identify and assess the risks of all forms for flooding to and from the development and demonstrate how theses flood risks will be managed so that the development remains safe throughout its lifetime, taking climate change into account”

This report has been prepared to address the requirements of the NPPF and has derived the following data/information from various sources including:

Information published or explicitly provided by the Environment Agency (EA);

Information published by the Local Planning Authority, including the SFRA;

A site specific topographical survey;

Site specific flood model data provided by the EA; and

Specific design works carried out for this report.

Pinnacle Consulting Engineers Ltd are specialists in flood studies with a track record of several hundred successful FRA reports and assessments.


2 EXISTING SITE CONDITIONS

2.1 Site description

The proposed development is located at National Grid Reference (NGR) 424850, 323850 off Hawkins Lane, Burton-upon-Trent, East Staffordshire DE14 1PT.

The existing site area is approximately 38,009m² is bounded by Network Rail to the north, Hawkins Lane to the south, Horninglow Street to the west and a Business Park to the east (see Appendices A and B for a site location plan and existing site plan). The main access to the site is via Hawkins Lane. The western boundary is partly formed by a multi-span masonry arched bridge which carries Horninglow Street over the railway.

The site has a history of various previous uses, ranging from a work-house in the late 1800s, an ale store and timber yard with associated rail sidings, to a barrel works which operated from the 1970s and has been the most recent use. The barrel works employed processes such as degreasing, acid pickling and alochrome coating in the refurbishment of beer barrels. The site has also recently been used for the manufacture of scaffolding products. These buildings were recently demolished and the site has been derelict since 2009.

Approximately 1,440m² of the existing site is impermeably paved (Appendix C).

The area surrounding the site has a similar industrial heritage. A small number of residential properties are present at the southeast and southwest site boundaries but the majority of the surrounding area is under light industrial or commercial usage.

Figure 2.1 – Aerial View of the existing development site (© Google 2014) (Approximate Site Extents Edged Red)

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The maximum thickness is around 400m in the centre of the Needwood Basin, though the thickness here, at the edge of the feature is likely to be somewhat less. 500m east of the site, the bedrock sequence is faulted.

2.3.1 Table 2.2 – Geological Ground Conditions

2.4 Source Protection Zones

The EA Source Protection Zone map identifies possible aquifers within the site and its vicinity. Figure 2.3 shows that the site is located within the ‘Total Catchment’ of a Groundwater Source Protection Zone. From 1 April 2010 the Environment Agency requires compliance with their Groundwater Protection Policy using aquifer designations that are consistent with the Water Framework Directive. The Aquifer maps for superficial deposits and bedrock and published by the Environment Agency collectively confirm the aquifer sensitivity of the site.

Figure 2.3 - EA Groundwater Source Protection Zone Map


3 PROPOSED DEVELOPMENT

As shown in Appendix E and depicted in Figure 2.3 the proposed redevelopment comprises:

The construction of a Tesco store and associated service yard in the western part of the site

The construction of a non-food retail unit and a hot food restaurant takeaway unit

Car parking to the east of the site

A 6-island Petrol Filling Station unit along the southern boundary of the car park.

Figure 2.3 Proposed Development Layout

The total site area for the proposed redevelopment 38,009m², of which 3,562m² is pervious (approx. 10%) and the remaining 34,447m² is impervious (approx. 90%) (Appendix F). Therefore, the impervious area will increase significantly and would have the potential to increase surface water runoff, if not controlled, compared to existing conditions.


4 PROBABILITY OF FLOODING

The NPPF identifies six potential sources of flooding:-

Flooding from rivers (fluvial flooding);

Flooding from the sea (tidal flooding);

Flooding from land;

Flooding from sewers;

Flooding from groundwater; and

Flooding from reservoirs, canals, and other artificial sources.

These are considered below.

4.1 Flooding from rivers (fluvial flooding) & sea (tidal flooding)

The assessment of flood risk in this report is based on the definitions in Table 1 of the Technical Guidance to the National Planning Policy Framework, which recognises the following Flood Zones:

Flood Zone 1 - little or no risk, with annual probability of flooding from rivers and the sea of

less than 0.1% (1 in 1000-year)

Flood Zone 2 - low to medium risk, with annual probability of flooding between 0.1% and 1.0%

from rivers and between 0.1% and 0.5% from the sea

Flood Zone 3a - high risk of flooding with an annual probability of flooding of 1.0% or greater

from rivers, and 0.5% or greater from the sea.

Flood Zone 3b – the ‘Functional Floodplain’ with an annual probability of flooding of 5% or

greater.

An extract from the Environment Agency’s online flood map published on their website is shown in Figure 4.1 below, with Flood Zone 3a & 3b denoted by dark blue hatch and Flood Zone 2 a light blue. The site is shown to span Flood Zones 2 and 3, with the areas within Flood Zone 3 shown to benefit from flood defences. The main body of water near the site is the River Trent. It rises in the Staffordshire Hills near Stoke-on-Trent and becomes navigable through Burton-upon-Trent.

4.1.1 Historic Floods

Burton has suffered on numerous occasions from fluvial flooding both as a result of rainfall and snowmelt. Due to the location of Burton, moderately high up in the catchment, there is a relatively quick response time between rainfall and the rise in river levels. This makes flood forecasting problematic and reduces the viability of temporary and demountable defences through the town. Following floods in 1947, defences were built through Burton town centre to a 1 in 100 year standard. Figure 4.2 shows the maximum water levels reached during the various historic events at various locations illustrated by a map, both of which were purchased from the Environment Agency. The maximum level reached was 45.35m AOD.

4.1.2 Flood Defence

Burton is protected by flood defences, which have been implemented through a series of alleviation schemes since the 1960s. The initial scheme was developed in response to the 1947 floods. These flood alleviation schemes were observed to operate effectively during the November 2000 flood event, although it was reported that water did seep through weakness in the structures. With the exception of a short stretch adjacent to the Meadowside Centre, the defences throughout Burton have now been brought up to the 1 in 200 year standard and the last major improvement works were carried out in


2006-2007. The Environment Agency has the responsibility for inspection and routine maintenance of the formal defences.

Site specific flood data was provided by the EA in October 2014 and is contained in Appendix G. This information includes the locations of flood defence walls and the water level that may be reached during design events of various return periods. According to the SFRA, the Environment Agency upgraded certain sections of the defences, to provide a 1 in 200 year standard of protection from an existing 1 in 100 year standard.

The data provides predicted flood levels across the site for a breach of the flood defences during 1 in 100 year fluvial event with allowance for climate change and for overtopping of the flood defences during a 1 in 1000 year event. Peak flood levels are shown to be 45.36m AOD under both events.

Figure 4.1 – Environment Agency Online Flood Map Extract (Approximate Site Extents Edged Red)


Figure 4.2 – Historic Flood Levels

4.2 Flooding from land & sewers

The SFRA presents information on the past sewer flooding and areas at potential risk in Burton upon Trent, following consultation with Severn Trent Water based on DG5 records (which captures reported incidents of sewer flooding and reports them to Ofwat). Full information was withheld due to the Data Protection Act but indicative maps were published in the SFRA, showing that the scale of sewer / surface flooding to be localised. No specific information on flood risk from surface water and sewer sources has been identified and therefore it is assumed that these are not significant.

The EA Flood Map for Surface Water is published on their website to identify areas potentially at risk of flooding from surface water. This mapping identifies low-lying areas and routes along which overland flows will pass based on local topography, both of which may be prone to surface water flooding.

An extract from the map is shown in Figure 4.3 below. This identifies a low-lying open area in the centre of the site to be at risk of surface water flooding, however no flow paths into the site from third party land are shown. This suggests that surface water flooding may occur within the existing site due to inadequate local drainage provision. Whist this is a risk the existing site, it can be addressed through provision of suitable drainage as part of the development, and is therefore not considered to pose a risk to the new development.


Figure 4.3 – EA Surface Water

4.3 Flooding from groundwater

The SFRA report includes references to the Environment Agency’s groundwater team but has very few reported incidences of groundwater flooding within East Staffordshire. The only events that have occurred were a result of the cessation of the quarrying of gravel and sand in the area and thus the abstraction of water from the pits. Once the abstraction operations ceased, groundwater levels rose and filled some of the pits, hence the existence of the Branston Water Park on the right banks of the River Trent before entering Burton upon Trent. As a result of this, there has been one report regarding the occurrence of minor cellar flooding.

The site is therefore not considered to be at risk from groundwater flooding.

4.4 Flooding from reservoirs, canals, and other artificial sources

4.4.1 Flood risk posed by the Trent and Mersey Canal

The Trent and Mersey Canal is as a body of water with hydraulic connectivity to the River Trent but will not pose flooding risk to the site of the proposed development. This is because in the vicinity of the site, the canal is on the far side of the adjacent railway embankments. Furthermore, it is effectively a self-regulating system, with water levels controlled through a system of sluices and weirs, aiming to maintain a freeboard of 300mm. In isolation, the canal system operates effectively and is able to accommodate the flows that enter it from feeder streams and its own small catchment areas. The combined operation of the canal and the River Trent is likely to reduce the overall flooding risk, as it provides extra storage capacity.

4.4.2 Flood risk posed by the Blithfield Reservoir dam failure

Blithfield Reservoir, a significant reservoir for which the Reservoir Act 1975 is applicable, is located upstream of Burton upon Trent. A dam failure occurred in the 1930s and resulted in a loss of life. Any


failure would result in the rapid release of a large volume of water down the River Blithe to the River Trent with a possible impact on Burton upon Trent. The SFRA notes that the operation of reservoirs is strictly managed, complying with appropriate legislation (Reservoirs Act 1975) enforced by the Environment Agency. This Act was overhauled in the in Flood and Water Act 2010, putting in place a risk-based approach to reservoir management.

The site is therefore not considered to be at significant risk from artificial sources.


5 POLICY STATUS FOR PROPOSED DEVELOPMENT

5.1 Vulnerability classification

The proposed development complies with the following principles:

The proposed development lies within Flood Zones 2 and 3 (defended);

The proposed development is classified as ‘less vulnerable’ in accordance with Table 2 of the

NPPF (reproduced as Table 5.1 below).

Essential

Infrastructure

Essential transport infrastructure (including mass evacuation routes) which has to cross the area at risk

Essential utility infrastructure which has to be located in a flood risk area for operational reasons, including electricity generating power stations and grid and primary substations; and water treatment works that need to remain operational in times of flood

Wind Turbines

Highly Vulnerable

Police stations, Ambulance stations, Fire stations, Command Centres and telecommunications installations required to be operational during flooding

Emergency dispersal points

Basement dwellings

Caravans, mobile homes and park homes intended for permanent residential use

Installations requiring hazardous substances consent

More Vulnerable

Hospitals

Residential institutions such as residential care homes, children’s homes, social services homes, prisons and hostels

Buildings used for dwelling houses; student halls of residence, drinking establishments, nightclubs and hotels.

Non–residential uses for health services, nurseries and educational establishments

Landfill and sites used for waste management facilities for hazardous waste.

Sites used for holiday or short-let caravans and camping, subject to a specific warning and evacuation plan.

Less Vulnerable

Police, ambulance and fire stations which are not required to be operational during flooding.

Buildings used for shops; financial, professional and other services, restaurants and cafes, hot food takeaways, offices, general industry, storage and distribution, non-residential institutions not included in “more vulnerable”, and assembly and leisure.

Land and buildings used for agriculture and forestry.

Waste treatment (except landfill and hazardous waste facilities).

Minerals working and processing (except for sand and gravel working).

Water treatment plants and sewage treatment plants (if adequate pollution control measures are in place).

Sewage treatment works (if adequate measures to control pollution and manage sewage during flood events are in place).

Water-compatible

Development

Flood control infrastructure.

Water transmission infrastructure, pumping stations.

Sewage transmission infrastructure and pumping stations.

Sand and gravel workings.

Docks, marinas, wharves

Navigation facilities.


MOD defence installations.

Ship building, repairing and dismantling, dockside fish processing and refrigeration and compatible activities requiring a waterside location.

Water-based recreation (excluding sleeping accommodation).

Lifeguard and coastguard stations.

Amenity open space, nature conservation and biodiversity, outdoor sports and recreation and essential facilities such as changing rooms.

Essential ancillary sleeping or residential accommodation for staff required by uses in this category, subject to a specific warning and evacuation plan.

Notes

1 - This classification is based partly on Defra/Environment Agency research on Flood Risks to People (FD2321/TR2)21 and also on the need of some uses to keep functioning during flooding.

2 - Buildings that combine a mixture of uses should be placed into the higher of the relevant classes of flood risk sensitivity. Developments that allow uses to be distributed over the site may fall within several classes of flood risk sensitivity.

3 - The impact of a flood on the particular uses identified within this flood risk vulnerability classification will vary within each vulnerability class. Therefore, the flood risk management infrastructure and other risk mitigation measures needed to ensure the development is safe may differ between uses within a particular vulnerability classification.

Table 5.1 – Flood Risk Vulnerability Classification

Vulnerability Classification

Essential

Infrastructure

Water-compatible

Highly Vulnerable

More Vulnerable

Less Vulnerable

Flo

od Z

one

Zone 1

Zone 2 Exception Test

Zone 3a Exception Test Exception Test

Zone 3b Exception Test

Key

Development is appropriate

Development should not be permitted

Table 5.2 – Flood Risk Vulnerability and Flood Zone ‘Compatibility’

The proposed development is appropriate in accordance with Table 3 of the NPPF, reproduced in Table 5.2 above.


6 SEQUENTIAL TEST & EXCEPTION TEST

The NPPF requires that all development is sequential tested to steer new development to areas at the lowest probability of flooding (Flood Zone 1). The Sequential Test would normally be completed by the Local Planning Authority (LPA) to inform the preparation of the Local Development Framework (LDF), where one exists. However, where this process has not yet been completed the onus for the provision of evidence demonstrating successful application of the Sequential Test falls to the developer, or promoter of the site. The NPPF also requires the layout of a site to be sequentially tested to locate the most vulnerable land uses in the areas at lowest risk of flooding.

The NPPF acknowledges that in some circumstances it may not be possible to locate development in areas of low or appropriate (considering development vulnerability) flood risk or that there may be other valid reasons for a development to take place within the floodplain. In these circumstances, it is necessary to apply the Exception Test to clearly demonstrate that the benefits for development of a site outweigh the flood risks to the development and its occupants. Table 3 of the NPPF (reproduced in Table 5.2 above) indicates when the Exception Test is required.

The East Staffordshire Borough Council Strategic Flood Risk Assessment Level 2 Report (Royal Haskoning, August 2008) (Level 2 SFRA) shows the site as development site No: E47. See Appendix H for the Level 2 SFRA development plan.

However, the site was not included in the adopted LDP, the East Staffordshire Local Plan (ESBC, July 2006), and so a sequential test had not been undertaken. See Appendix I for the LDP development plan map.

A now expired planning permission application no: OU/00229/060/PO had been previously provided for the site in October 2004, for a different development proposal described as ‘Redevelopment of site for B1 (business), B2 (general industrial) and B8 (storage and distribution) use, with trade sales facilities and construction of a new vehicular access’.

The current planning permission application is described as ‘Hybrid application including a full planning application for the erection of a new retail food store, retail unit and petrol filling station with associated servicing and plant, hand car wash area, recycling area, landscaping, access and other associated works, and an outline planning application with all matters reserved for the erection of a restaurant with hot food takeaway with associated car parking and works’. As the planning permissions are not considered a comparable mix and intensity of uses, the principle of development is not valid.

Therefore, as the proposed development is within Flood Zone 2 and Flood Zone 3a, a sequential test is required to be undertaken by the developer. An exception test is not required for the development, as noted in Table 5.2.

6.1 Methodology

6.1.1 Defining the search area

The search area for the test was defined as the area encompassed within the development boundary of the Burton and District area, as provided in the Local Plan and reproduced in Appendix I. This area of search has been defined taking into account the proposed foodstore’s likely catchment area and the stores ability to serve a retail need that exists in the north of the town. The Burton Town Centre area was dismissed at this initial stage as the proposed development area of 3.9 ha was too large for any potential site within the town centre area as has been highlighted within the retail sequential test assessment set out within the submitted Planning and Retail Statement.

The adopted Local Plan allocates a number of larger sites for development for employment (Policy E2) or Retail use (E2). Given this Local Plan allocation these sites have been considered in terms of


suitability and availability to accommodate the proposed development. These alternative areas have been numbered and together with the proposed site are reproduced in Appendix J. These sites are also listed in Table 1 below, together with their approximate area, percentage of site within the Flood Zone (FZ) 2 and FZ 3 for both the Environment Agency (EA) FZ Map version used in the 2006 LDP report, and the latest EA Flood Zone Map (downloaded from EA website, September 2014), and if Flood Zone 3 is defended.

2006 LDP FZ Map version

Latest 2014 FZ Map version

Alternative Site No.

LDP Development Type / SFRA 2 no.

Site Area (ha)

% in FZ 2

% in FZ 3

% in FZ 2

% in FZ 3

FZ 3 Defended?

1 Employment (E2) 8.96 100 0 40 20

N

2 Employment (E2) 14.48 5 25 35 55

N

3 Employment (E2) 0.79 0 0 0 0

n/a

4 Employment (E2) 4.03 0 0 0 0

n/a

5 Employment (E2) 1.31 0 70 75 25

N

6 Employment (E2) 5.27 0 100 85 0

N

7 Employment (E2) 4.60 0 100 50 0

N

8 Retail (R2) 4.26 5 95 5 95

Y

9 Part of SFRA 2 no. E56

4.29 100 0 50 20 N

10 SFRA 2 no. E31 9.4 0 0 0 0

n./a

Proposed n/a 3.81 25 75 40 60

Y

Table 1 – Alternative and proposed size and flood risk characteristics.


6.1.2 Determining whether alternative sites are ‘reasonably available’

The latest government guidance on applying the sequential tests to individual planning applications is found in the following link:

http://planningguidance.planningportal.gov.uk/blog/guidance/flood-risk-and-coastal-change/applying-the-sequential-test-to-individual-planning-applications/

As can be seen from Table 1 above, Site 3 and 5 can be dismissed due insufficient area required based on the proposed site area. In terms of flood risk, all the properties are in Flood Zone 2 and/or Flood Zone 3 apart from Site 4 and 10. Only Site 8 and the proposed site are defended to the 1 in 200 year flood event, however Site 8 has a greater area in FZ 3 (95%) compared to the proposed site (60%).

The following publically available data has been found on the current status of the alternative sites:

Alternative Site No.

Comment

1 Planning permission (St Modwen) exists to redevelop the site for mixed use including residential, industrial, hotel and pub/restaurant, application ref. (P/2011/01130/JN/PO) so the site cannot be considered available.

2 Unsuitable as no road frontage/poor access, and too far out of town centre and so conflicts with other planning policy. Planning permission exists on the site for a B8 use class, application ref. (PA/25617/023/JPM/PO) so the site cannot be considered available

3 To small so not taken forward for comment

4 Developed between 2009 and June 2013 and in use by in use by Unipart Logistics.

5 Too small so not taken forward for comment

6 Class B8 warehouse occupied by Hobbycraft, so the site cannot be considered available

7 Planning permission exists for mixed use development, application ref. (PC/21616/094/PO/JPM) so the site cannot be considered available.

8 Developed between 2009 and June 2013 and in use as a B&Q store.

9 Planning permission (St Modwen) exists to redevelop the site for mixed use including residential, industrial, hotel and pub/restaurant, application ref. (P/2011/01130/JN/PO) so the site cannot be considered available.

10 Developed pre 2009 with mixed use including Stretton Business Park and a food store. Served by poor connections with the town centre and would therefore fail to ensure the delivery of other planning policies (i.e. retail policies).

Table 2 – Current status of the alternative sites.

6.2 Test Conclusion

Based on the analysis in Section 2 above, all the alternative sites within the defined search area could be considered not sequentially preferable due to their inadequate size, increased flood risk, recent occupancy or active planning applications. Therefore the proposed site is considered to pass the Sequential Test.


7 FLOOD RISK MANAGEMENT STRATEGY

7.1 On-Site flood Risk

Having considered the risk of flooding to the site from all sources, it has been concluded that the majority of the site is in an Area Benefitting from Defences, which are built to a design standard of 1:200 years. A small part of the site is located in Flood Risk Zone 2.

7.2 Residual Risk & Flood Evacuation Strategy

Although the site benefits from defence, there remains potential residual risk of flooding from the River Trent due to a failure of the defences. The site is also at risk from flooding from overtopping of the defences under events in exceedance of the 1 in 200 year level of protection. To cope with such possibilities, an Evacuation Plan has been completed for the site and is included in Appendix K.

7.3 Finished Floor Levels

Site specific flood level data has been provided by the EA for the site, as discussed in section 4.1, indicating a flood level of 45.36m AOD for both the breach and overtopping scenario.

In consultation with the EA, it has been recommended that finished floor levels be set with a minimum freeboard of 300mm above this level i.e. a minimum of 45.66m AOD.

7.4 Surface water Drainage Strategy

The existing and proposed impermeable areas have been assessed to determine the extent of any potential increase in surface water runoff. This corresponds to NPPF which states, “Surface water arising from a developed site should, as far as is practicable, be managed in a sustainable manner to mimic the surface water flows arising from the site prior to the proposed development, while reducing the flood risk to the site itself and elsewhere, taking climate change into account. This should be demonstrated as part of the flood risk assessment.”

It can be seen from enclosed drawings (Appendix C) that the existing impervious area of the site and therefore the existing positively drained area is 1,440m². The proposed impervious area is 34,447m² resulting in an increase of 33,007m². It should be noted however, that the site was previously brownfield and therefore surface water runoff would have been significantly greater than the figure provided above. To ensure that betterment is provided, surface water discharge will be reduced to a Greenfield rate of 5l/s/ha. Based on a proposed impermeable area of 34,447m², the discharge rate from the site will be restricted to 18.5l/s. An additional 7.0l/s will be discharged from the two small public car parks south of the site adjacent to Hawkins Lane as part of the pre commencement works agreed with Severn Trent.

Infiltration methods of surface water disposal are not considered feasible due to restrictions relating to the protection of groundwater aquifer resources and a relatively shallow ground water table (section 2.3). It is proposed that a lined permeable paving system be installed to reduce surface water runoff to Greenfield rates from the majority of the site and thus improvement in water quality will be provided. The runoff from roof areas will be directed to an underground attenuation system which will restrict runoff to 5l/s/ha via a suitable flow control device, such as a hydro-brake or orifice plate.

Public sewer records indicate that a surface water sewer is located within the site, as shown in Appendix L. the existing pipe is a 225mm diameter pipe with a gradient of 1 in 470 and has a capacity of approximately 23.5l/s. it is proposed that with the approval of Severn Water, existing outfall routes be reused to convey flows from the permeable pavement system to receiving public sewers. Full details of existing outfalls will be established during the detailed design stage, and approval sought from Severn Trent Water under through a 106 application.


It should be noted that regardless of the methods of attenuation, the proposed drainage system will be designed for the 1:100 year + 20% climate change event with no flooding on site.

Permeable pavement systems will treat receiving runoff from car park areas and where applicable, precautions relating to water quality will be observed by the provision of appropriate petrol interceptors, deep silt trapped gullies and silt boxes to all channel drains.

The proposed drainage strategy is detailed on the plans in Appendix M, with supporting calculations contained in Appendix N.

7.5 Sustainable Drainage Systems (SUDS)

A permeable pavement system will be installed to receive runoff from proposed parking areas. In addition to attenuating runoff to Greenfield rates, this option will provide a notable improvement in water quality when compared to the previous industrial uses at this site.

The use of a green roof has been assessed. The proposed retail store is a relatively lightweight structure and therefore, the effect on the structural design of the building when the roof is holding water would be to increase loads by approximately 71% (from 1.1kN/sqm to 1.86kN/sqm). This impact will increase the size of the rafters, purlins, beams and columns which in turn will increase foundation sizes by approx. 71% with the associated increase in excavation and disposal that would be required. In terms of sustainability, any potential benefits would have to be offset against the required increase in steel production and other natural reserves. There will also be increase disposal of excavated arising to landfill; with the added vehicle movements that this would bring. There would also clearly be a significant increase in the cost of the project and the construction programme would also be lengthened.


8 CONCLUSION

The site is located within Flood Zones 2 and 3, but is protected by existing flood defences

providing a 1 in 200 year level of protection.

The Environment Agency have provided site specific data for the site, indicating flood levels of

45.36m under both a breach of the flood defences and when overtopped under a 1 in 1000

year event.

No significant risks from other flood sources have been identified.

The site is classified as ‘Less Vulnerable’ and the development classified as ‘appropriate’

under requirements of the NPPF.

Although the proposed development is considered appropriate for the risk level, it is still

exposed to a residual risk of flooding and hence a Flood Evacuation Plan has been prepared.

Minimum Finished Floor Levels should be set 300mm above the flood level to ensure the store

remains dry during extreme events.

The proposed development will increase the impervious area and whilst infiltration methods of

surface water disposal are not considered feasible, it is proposed to install a lined permeable

paving system, to provide water quality improvements and reduce surface water discharge to

Greenfield rates.

The site redevelopment will reduce flood risk compared to existing and provide betterment to

the downstream catchment.


Appendix A – Site Location Plan

REV DESCRIPTION BY CHKD DATE

- - - - -50mm ON A3 DWG. 500

Studio Four37 Broadwater RdWelwyn Garden CityHertsAL7 3AX

PHONE01707 385300FAX01707 385321

Grosvenor Court67a Patrick StreetDun LaoghaireCo Dublin

PHONE01 231 1041FAX01 231 1065

Pinnacle House3 Meridian WayNorwichNorfolkNR7 0TA

PHONE01603 702010FAX01603 702015

Suite CAvonbridge House2 Bath RoadChippenhamWilts.SN15 2BB

PHONE01249 454103FAX01249 705989

55 Newton StreetManchesterLancsM1 1ET

PHONE0161 228 6020

CLIENT/PROJECT

STATUS

DRAWING TITLE PROJECT REF. DRG NO. REVISION SCALE

A3SHEET SIZEDATECHECKEDDRAWN BY

INFORMATION

TESCO STORES LTDBurton on Trent

SITE LOCATION PLAN-

100602 006 - NTS

PS GB Dec 10


Appendix B – Existing Site Plan

NORTH

15

Chy

14

EstateIndustrialWindsor

T A Centre

L Twr

Depot

GLENSYL WAY

5

Business ParkEccleshall

4 3

62

7

Middle Yard

98

Works

2

IndustrialAnderstaff

Park

8

3

B1

1

E4

L Twr

EstateManor Trading

Bus ness ParkSovereign

B3

2

E3

B2

4

D4

5

Derwent Pa k

9

9

D2

Weighbridges

Works

171

C1

to C

3

175

33

178

C4

Tank

M dd e Yard

Wor

ks

Business ParkSovere gn

Depot

Wo ks

20

17S G

antry

Wes

t Yar

d

SL

7

2

2

4

L Twr

6

L Twr

L Twr

Gas Gov

5

1a

127

El Sub Sta

126a

126125b

125a125

124b124a

124

118

BRO

OK

STREET

Warehouse

102

112

107L Twr

105FB

82

98

86

FB

4

New Brewery

Gas Gov

LIT

LE B

UR

ON

EAS

T

BridgeBurtonLittle

Silos

Tank

Builder's Yard

Works

LITTLE BURTON W

EST

Works

2726

STREETHO

RNINGLO

W

DERBY TURN12

311

6

L Twr

StaSub

El

5

BURTON

5

141

Silos

142

Garage

MP 10 25

3

3L

TTLE B

UR

TON

EA

ST

Works

3

7

DERBY STREET

LITTLE

135

243

1

152

Ryk

nild

Stre

et

ROMAN

ROAD

2

143

S los

147

46

LB

136

Depot

TCB

46 0m

245

244b243

a

242

134

240

132

135

Works

153

FB

273

DERBY

STR

EET

157

5

126

DALLOW STREET

ROAD

120

9

119

70

267

75

115

114

45 7m

69

79

VICTO

RIA S

TREE

T

MP10 5

SAUNDERS

cNOTES

Date

Title

Scale

CheckedDrawn

Drawing Number Revision

Project

SITE LOCATION PLAN SCALE 1 : 1250

This drawing to be read in accordance with the specification/Bills of Quantities andrelated drawings

No Dimensions to be scaled from this drawing All stated dimensions to be verifiedon site and the Architect notified of any discrepancies

0 100

Scale bar 100mm at 1 1

Saunders PartnershipStudio Four37 Broadwater RoadWelwyn Garden CityHertfordsh re AL7 3AX

T 01707 385300F 0870 6222135www saundersarchitects comoffices at Welwyn Garden City | Bristol | Manchester

Architects

PROPOSED TESCO STOREHAWKINS LANEBURTON UPON TRENT

SITE LOCATION PLAN

1:1250 A1 NOV 10

TN GT

6604_P001 -

@

R D E T INREV DATE NOTE

ISSUED FOR COMMENT/APPROVAL

NOTES

* Landscaping is indicative only and to be agreed by Landscape Arch tectRefer to latest Landscape Architects drawings for accurate detailedLandscape scheme

* Highways arrangement shown on our drawings is indicative only Latesthighways design and deta led highways design is subject to agreementbetween Highways Authority and Highways Consultant

* Existing levels have been taken from Ordanance Survey and TopograhicalSurvey information by others

* Proposed levels to be confirmed by Structural and Civil Engineer and to beagreed with c ient Proposed levels subject to change following anyremediation work carried out to the s te after our drawings have been issued inwhich instance we advise a revised Topographical Survey is carried out

* Tesco Store shown is a modified F80 at grade with cafe and staff onmezzanine due to the site constraints

* Original Store footprint and figures taken from Tesco Standard StoreFootprints UK concept stores, 2010 Q2 Footprints (Sheet 2 of 4) Based oninformation provided by Tesco Stores Ltd

* KPI figures related to the above standard footprints have been provided byTesco Stores Ltd

* Modified Stores vary from standard figures and to obtain accurate figures wewould advise a Retail Layout is commissioned and agreed by Tesco

LEGENDSite Boundary


Appendix C – Existing & Proposed Impermeable Areas


Appendix D – Topographic Survey

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