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LAND SOUTH OF THE LEISURE CENTRE, BASINGSTOKE ENGINEERING OPTIONS AND APPRAISAL REPORT for Basingstoke and Deane Borough Council May 2012 Report Ref: 049.1080/RW/EF/95206 Rev C Upton M c Gougan Limited Partnership House Moorside Road Winchester Hampshire SO23 7RX T: 01962 834400 F: 01962 834411 E: [email protected] W: www.uptonmcgougan.com

Basingstoke and Deane Borough Council - Montagu Evans · Basingstoke and Deane Borough Council ... therefore the Environment Agency will require a flood defence ... Thornycroft Industrial

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LAND SOUTH OF THE LEISURE CENTRE, BASINGSTOKE

ENGINEERING OPTIONS AND APPRAISAL REPORT

for

Basingstoke and Deane Borough Council

May 2012

Report Ref: 049.1080/RW/EF/95206 Rev C

Upton McGougan Limited

Partnership House Moorside Road

Winchester Hampshire SO23 7RX

T: 01962 834400 F: 01962 834411

E: [email protected] W: www.uptonmcgougan.com

Land South of the Leisure Centre Upton McGougan Ltd

Engineering Options and Appraisal Report

049.1080/RW/EF/95206 Rev C

May 2012 Page ii

CONTENTS

INTRODUCTION ............................................................................................................. 1 1.0

THE SITE ........................................................................................................................ 2 2.0

HIGHWAY ACCESS CONSIDERATIONS ...................................................................... 4 3.0

FLOOD RISK & DRAINAGE ........................................................................................... 6 4.0

SERVICES .................................................................................................................... 12 5.0

WATER MAIN RELOCATION ....................................................................................... 14 6.0

POTENTIAL SITE USES............................................................................................... 16 7.0

POTENTIAL SITE CONSTRAINTS ............................................................................... 17 8.0

FURTHER INVESTIGATIONS ...................................................................................... 18 9.0

SUMMARY AND CONCLUSION .................................................................................. 19 10.0

Figures Figure 1: Site Location Plan .................................................................................................. 1

Figure 2: Basingstoke Leisure Centre Flood Map .................................................................. 6

Figure 3: PPS25 Table D1 - Zone 3a High Probability ........................................................... 7

Figure 4: Table D2 - Flood Risk Vulnerability Classification (Part 1) ...................................... 8

Figure 5: Table D2 - Flood Risk Vulnerability Classification (Part 2) ...................................... 9

Appendices Appendix A : Topographical survey

Appendix B : Borehole Record and Location Plan

Appendix C : Envirocheck Report Appendix D : Flood Screening Study

Appendix E : Thames Water Sewer Records

Appendix F : SSE Mapping Records

Appendix G : Gas Mapping Records

Appendix H : Telecoms Mapping Records

Appendix I : South East Water Mapping Records

Appendix J : Probable Route of any Water Mains Diversion

Appendix K : Site Constraints

Appendix L : Timings for ecological surveys

Appendix M : Approximate Area Of The Site Suitable For Development

Land South of the Leisure Centre Upton McGougan Ltd

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INTRODUCTION 1.0

1.1 Appointment

Upton McGougan Limited (UML) has been commissioned by Basingstoke and 1.1.1Deane Borough Council (BDBC) to produce an engineering options and appraisal report for a land parcel to the south of the Basingstoke Leisure Park.

The site under consideration lies to the west of Ringway West and south of 1.1.2

Churchill Way West dual carriageways. The site location is shown in Figure 1.

Figure 1: Site Location Plan

1.2 Basingstoke Leisure Park

As part of the options report, there is also a requirement to undertake an evaluation 1.2.1

and provide an estimate of the cost to relocate the existing surface water attenuation basin from the Basingstoke Leisure Park to the study site. This may deliver more value by allowing the development aspirations for the already established Park to be brought forward.

There is also a requirement as part of the same exercise for a costed engineering 1.2.2analysis to move the existing water main to the southern boundary of the Park. This frees land to the south of the existing museum for potential development.

1.3 Report Scope

This report discusses the site, highway access, flood risk and drainage, services 1.3.1

and potential diversionary works, potential site uses and constraints, and further investigations required.

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THE SITE 2.0 2.1 River Loddon

The River Loddon runs through the site and the source of the River Loddon lies just 2.1.1to the west of the site. At the east of the site the watercourse becomes culverted and runs under Ringway West. The River Loddon is classified as a main river, therefore the Environment Agency will require a flood defence consent for any works within 8m. The location of the River Loddon (shown on the topographical survey) will affect the layout of any future use of the site.

2.2 Topography

A topographical survey of the site is provided in Appendix A. The survey shows the 2.2.1location of the River Loddon and various vegetation throughout the site. There are steep banks along some of the site boundaries, particularly in the north and east. Excluding the banks, the majority of the levels on site lie between 86m AOD and 84m AOD, with the site falling from west to east. As would be expected the site also falls towards the centre, towards the watercourse. Due to the topography re-grading of the site may be required.

The topographical survey also highlights the location of an electricity substation 2.2.2

along the southern boundary of the site, adjacent Thornycroft Lane. A foul sewer is shown on the surface running in a north south direction across the site. This is understood to be in use. The location of these will affect the layout of any proposed development, and the sewer may require diversionary works.

2.3 Geology

Whilst a site investigation was not available at the time of writing, the British 2.3.1Geological Survey online boreholes records have been consulted. A borehole was located at the eastern end of the site and the borehole log, together with a location plan is included as Appendix B. This shows the underlying geology to comprise chalk. It is understood the chalk is of poor quality and due to high groundwater levels piled foundations are likely to be required. It is recommended a site investigation is carried out in order to influence the foundation design.

2.4 Contamination

A BP filling station is located to the west of the site, and a Morrisons filling station is 2.4.1located to the east of the site. Therefore the risk of contamination associated with any potential leaking from the associated tanks should be considered. It is understood that hydrocarbon contamination has been encountered in the Thornycroft Industrial Estate to the east of the site. Anecdotal evidence indicates that contamination was encountered on the site of the old swimming pool to the east of the site. In addition due to historic industrial land uses in the area, the site may be at risk of contamination. Therefore it is recommended that the risk of contamination to the site should be considered and further investigated.

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2.5 Envirocheck Report

An Envirocheck report has been purchased and is available in Appendix C. This 2.5.1report includes environmental data, Ordnance Survey mapping and Ordnance Survey historical mapping. This provides an overview of the historical land use in the area and therefore gives an indication of the potential risks associated with the historical land use. The maps show no historic use of the site, except being associated with West Ham Farm. Water abstraction licenses and discharge consents are located in the area. An old motor works was located to the east of the site – this is likely to be the source of the hydrocarbon contamination found on the Thornycroft Industrial Estate. The site may also be affected by contamination from the motor works. Chalk pits have been located in the area historically, in particular one was located to the north of the site, on the north side of the railway. The findings in the Envirocheck report support the recommendation that further investigation is required into the risk of contaminated land.

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HIGHWAY ACCESS CONSIDERATIONS 3.0 3.1 Strategic Location

As previously mentioned the site under consideration is located to the west of 3.1.1Ringway West and south of Churchill Way West, as shown in Figure 1. The Ringway forms an orbital strategic route around the town centre and links directly with Junction 6 of the M3 motorway, as well as a number of radial routes providing access to Hook, Reading, Tadley, Newbury, Overton/Whitchurch and Alton.

The A30 Winchester Road links with the Ringway south of the site and provides a 3.1.2

link to the west to Junction 7 of the M3 motorway and onto Winchester/Southampton and Andover, via the A303.

The site is well placed to take advantage of the excellent strategic connections. It 3.1.3

also offers opportunities to differentiate links for sustainable modes. 3.2 Local Connections

Currently local connections to the site are very limited. This is primarily due to the site’s lack of use, which has meant that no real vehicular access has needed to be achieved. Apart from the Ringway West and Churchill Way West aspects on the eastern and northern frontages respectively, the western boundary abuts a vehicle sales dealership, accessed via a slip road, off Churchill Way West. The southern boundary abuts Thornycroft Lane, a shared cycle/foot way that forms part of a pedestrian and cycle link between the West Ham area of Basingstoke towards the town centre, through Morrisons. Thornycroft Lane is also defined as a Road Users Public Path (RUPP) meaning vehicular access is permitted for the length of Thornycroft Lane. The only necessary vehicular use of Thornycroft Lane by the public is to access the businesses along Thornycroft Lane. Whilst the site could be served by an access of Thornycroft Lane, the volume of vehicles associated with any proposed development is likely to exceed the capacity of this single lane access.

Grafton Way, which is the main distributor road for the West Ham Industrial Estate, 3.2.1

offers the closest potential vehicular access from the south (subject to land ownerships). Depending on the potential use of the site, it is unlikely that, except for a particularly low traffic generating use, an access at this location would even be considered. However, it should be considered that there are significant level differences between Grafton Way and Thornycroft Lane, therefore if the site were to be accessed from Grafton Way a bridge may be required. Based on the topographical survey it would appear the level difference is in the order of 3.3m, suggesting that there is likely to be sufficient head room for cyclists on Thornycroft Lane if an access bridge were to be provided from Grafton Way.

Worting Road provides the primary link to this location via the Worting Road/Sandys 3.2.2

Road roundabout and also offers a connection to A340 Ringway West, via south facing slip-roads. Any intensification of this limited-movements junction is unlikely to be viewed favourably by the highway authority, particularly given the current level of congestion experienced at peak travel times. There is a significant potential for an increase in rat-running traffic if access to this side of the site were chosen.

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3.3 Site Access

The recommended location for the primary site access would be off Churchill Way 3.3.1West, as a left in/left out arrangement, similar to that used for the fast-food restaurants and the Milestones Museum on the opposite side of the link. This would inevitably increase the u-turning vehicles at both the West Ham and Thornycroft roundabouts at the western and eastern ends of the links respectively. Some re-grading will be required to facilitate the construction of the access.

Whilst it has already been suggested that the other links to the south would not be 3.3.2

suitable for a significant volume of private vehicles, it may form part of a strategy to promote public transport, via a bus gate. The walk/cycle trips would still be catered for via Thornycroft Lane and a direct access from the site to Thornycroft Lane is recommended for pedestrians and cyclists.

An alternative to developing some of the land south of Churchill Way West would be 3.3.3

to relocate the existing surface water attenuation basin from the area immediately to the north of Churchill Way West (on the Leisure Park site) to this site. This would then allow further development on the leisure park site. This option would utilise the existing access to the leisure centre, with minor modifications, in the form of a spur, from the link road to the museum.

Should the option to utilise this site for stormwater attenuation be taken up, this 3.3.4

could be combined with a water based leisure activity. If this option were to be pursued then a new formal access to the site to the South of Churchill Way West could be constructed off the westbound carriageway of Churchill Way West (similar to that currently utilised for the eastbound access and egress for the leisure park.). If, however, access is only required for maintenance of the facilities then it would be possible to utilise the existing access to the South along Thornycroft Lane.

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FLOOD RISK & DRAINAGE 4.0

From examination of the Environment Agency’s (EA) Indicative Floodplain Map 4.1.1(IFM), provided in Figure 2, it is evident that much of the land has been classified as being primarily Flood Zone 3a. This is land that has a 1% annual chance of flooding.

Figure 2: Basingstoke Leisure Centre Flood Map

Planning Policy Statement 25, Development and Flood Risk classifies Flood Zone 4.1.2

3a as high risk, defined in Figure 3.

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Figure 3: PPS25 Table D1 - Zone 3a High Probability

It can be seen that the water compatible and less vulnerable uses of land are 4.1.3

appropriate in this zone, the more vulnerable uses will only be permitted subject to a detailed flood risk assessment (FRA) that demonstrates that the PPS25 Exception Test can be passed and concludes that any new development will not be at risk of flooding, or increase flood risk elsewhere. However, it should be considered that due to the size of the site, an FRA will be required regardless of the vulnerability of the proposed use of the site. The PPS25 vulnerability classes are given in Figure 4 and Figure 5.

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Figure 4: Table D2 - Flood Risk Vulnerability Classification (Part 1)

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Figure 5: Table D2 - Flood Risk Vulnerability Classification (Part 2)

It can be seen from the EA’s IFM that much of the site has been shown as being at 4.1.4

risk of flooding. From a walk over survey it is evident that the source of this flooding is surface water runoff which is entering the site via ditches and piped surface water drains to the north and south, there is a drainage channel/ditch (the River Loddon) running through the centre of the site which flows west to east. This ditch passes under the A340 Ringway West via a large concrete culvert.

The EA IFM is indicative only and it is therefore not possible to determine the true 4.1.5

extent of flooding without deriving flood levels. It should be noted that, based on the EA mapping, the site would not be suitable for development, except for water compatible usage, due to the level of flood protection required that would result in a loss of floodplain and therefore contravene EA policy.

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A Flood Screening Study has been obtained from Envirocheck and this can be 4.1.6found in Appendix D, the report not only provides information relating to the flood zones it also gives details of flooding from other sources. It can be seen that the site is also at risk from flooding from ground water and surface water runoff.

A Sequential Test will be required that demonstrates that there are no reasonably 4.1.7

available sites in areas with a lower probability of flooding that would be appropriate for the type of development or land use proposed. This test would need to be agreed and approved with the Planners before the EA will consider any proposals for the site.

The river map contained in the Flood Screening Report identifies the ditch as the 4.1.8

head of the River Loddon, part of which is classified as primary river and therefore any works in close proximity to it will require formal EA consent.

Subject to the site passing the Sequential Test it is recommended that a detailed 4.1.9

FRA is undertaken that will determine the quality of existing information available and its suitability for use in the FRA, of primary importance would be flood levels, flows and volumes etc. Should the information not be available it would be necessary to undertake hydrological and hydraulic modelling in order to determine flood levels and therefore plot the extent of the floodplain with more accuracy. It should be noted that the flood modelling will be a very involved process with no guarantee that the extent of flooding will be less than shown on the EA’s map.

It has been indicated that it may be desirable to develop the greenfield areas on the 4.1.10

Leisure Park site, just south of Milestones. There is a surface water attenuation basin present which is adjacent to the highway, it may be possible to relocate the attenuation basin onto the subject site thus freeing up development land on the Leisure Park site.

This proposal would require laying a large new surface water culvert under Churchill 4.1.11

Way West that will discharge into the subject site. The system will require hydraulic modelling to ensure that existing flows, and subsequent flood risk, is not increased downstream. It is likely that further control features, such as weirs etc., will be required in order to restrict flow rates etc.

Subject to sufficient cover being available to lay the new culvert under Churchill 4.1.12

Way West, it is estimated that based on experience from similar projects in the past, the cost of the work could be in the region of £70,000, however detailed design would need to be undertaken to confirm this.

The sewer records have been obtained from Thames Water and these can be 4.1.13

found in Appendix E. It can be seen that there is a 300mm/375mm diameter foul sewer running from Milestones and crossing the site. This sewer is above ground it is therefore assumed that any downstream chamber is very shallow thus making the diversion of the sewer very difficult.

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The downstream manhole is shown on the sewer records as being present on the 4.1.14

site however it is shown as abandoned and has not been found on the topographical survey. The top of the pipe levels are shown on the survey and from these it has been calculated that the sewer has a gradient of 1/160, the next adjacent manhole has been located on the topographic survey, however the surveyor was unable to lift the cover and the sewer records do not contain the level information. Further investigation of the sewer records indicates a manhole further downstream towards the Ringway West with an invert level of 84.00 AOD

Preliminary calculations suggest that the sewer could be diverted, however due to 4.1.15

the existing gradients the pipe sizes may need to be increased. Further investigation into the levels of the existing foul manholes 1002 and 2001 will be required to inform any detailed design. Based on the sketch scheme shown in Appendix M using our experience from previous schemes we would estimate the cost of the diversion would be in the region of £85,000 (Depending on the outcome of the further investigations.)

The subject site has been examined from the point of view of flood risk in order to 4.1.16

estimate the amount of the site that may be suitable for development. The watercourse, floodplain area and the area at the eastern end of the site have been considered unsuitable for development. Based on this it is estimated approximately 30% of the site (approximately 1ha) of the site may be suitable for development, however this could be considered further during the course of a detailed FRA. This area of the site lies around the perimeter of the western end in order to avoid the central floodplain and watercourse so will restrict any potential site layout. The approximate area of site that may be suitable for development is shown in Appendix M.

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SERVICES 5.0 5.1 Electricity

Mapping records from Scottish and Southern Energy Limited are contained in 5.1.1Appendix F. The records confirm that with the exception of the previously discussed substation, the site is not currently served by electricity infrastructure. This also holds true for the potential alternative site north of Churchill Way West. The records also show substations on Thornycroft Lane and adjacent the Milestones museum.

New infrastructure would therefore be required to serve any new development, on 5.1.2

either site. The type and scale of infrastructure would be partially dependant on the type of development proposed, however it is probable that any proposed development could be served by the existing substation on site.

5.2 Drainage

Drainage services have been discussed previously in Section 4.0. 5.2.1

5.3 Water

A water main relocation will be required, if the site to the north of Churchill Way 5.3.1West is developed, and this is discussed further in the subsequent Section 6.0. No major diversionary works associated with water mains are envisaged relating to the site south of Churchill Way West.

5.4 Gas

Gas mapping records are included as Appendix G. This shows no existing gas 5.4.1infrastructure on the site, which is supported by the topographical survey. However, the existing premises on Thornycroft Lane and Grafton Way, as well as the Milestones Museum are served by the existing low pressure infrastructure. It is likely that any proposed development could be served by a new connection from the existing infrastructure however capacity checks would be required to determine if sufficient capacity exists in the existing network.

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5.5 Telecoms

Telecoms mapping records are included as Appendix H. These records show 5.5.1existing underground plant serving Thornycroft Lane, Grafton Way and the leisure park. It is likely that this could be extended to serve the respective sites.

5.6 Summary

Based on a preliminary services audit it would appear that all main utilities are 5.6.1available within the area. A water main diversion will be required in order to develop the site north of Churchill Way West, and a foul water sewer runs through the site south of Churchill Way West, above the surface. It is recommended that the contractor satisfy themselves prior to commencing work that there are no utilities likely to cause conflict with the works.

New connections will be required for all services, subject to capacity checks, 5.6.2

however there is the possibility that works may be required to upgrade some of the existing infrastructure to serve the site. Capacity checks are not feasible at this stage prior to the determination of the type and scale of development.

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WATER MAIN RELOCATION 6.0

This section considers the water main relocation that would be required to develop 6.1.1the alternative site, north of Churchill Way West and incorporates the results of a desktop review of information gathered from South East Water.

With regards to potential diversion works, South East Water has been contacted for 6.1.2

their input. They have advised that they would not be able to provide any information within the timeframe of producing this report. However, an assessment has been made based on the records available and historic data for similar works on water mains.

The mapping records received from South East Water are contained within 6.1.3

Appendix I. Generally, these show water mains running below ground alongside Euskirchen Way and the cycle track within the Basingstoke Leisure Park.

The South East Water plan has been annotated with the pipework sizes, advising 6.1.4

the 2no.mains as being 22” UPVC and 16” UPVC.

It is believed that the origin of one of these mains is a borehole to the north of the 6.1.5site. The main is routed from the north on to the site, closely following the route of a cycle path. There is a branch in the margin between the cycle track and the car park serving the Milestones Museum.

From this junction both mains run in a westerly direction, with a divergence as the 6.1.6

16” service continues to follow the cycle track to the south-west before turning to closely follow Churchill Way West. In the opposite direction the two mains are routed approximately south-east across the entrance to the Milestones car park before turning to run in an easterly direction, close to, and parallel to, Churchill Way West.

In order to facilitate future development it would be desirable to ‘sterilise’ the area of 6.1.7

any major services infrastructure; this includes the two major water mains.

It has been assumed that the road network and cycle track may be subject to 6.1.8remodelling as part of any development of the identified site between the Leisure Park and Churchill Way West. Therefore, diversion of the water mains to the southern edge of the site has been considered the most appropriate option.

However, there are a number of factors to be considered. The first of these is that 6.1.9

the 2no. water mains are not simply distributing to/from an east – west direction, one also originates from the north. This means that, although the mains can be re-routed to the southern boundary of the site, the water supply from the north must still cross the site and the branch serving east and west re-established.

The result is a possible compromise in that the main from the north would be 6.1.10

extended southwards to the diverted service close to Churchill Way.

The second issue is the existence of drainage ditches running parallel to Churchill 6.1.11Way West. The retention of these would push the water mains further on to the site.

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Additionally, the highway boundary is marked by landscaping including a band of 6.1.12trees and shrubs. Therefore the probable route of any mains diversion would not be tight to the boundary and would follow the line of the trees and drainage ditch parallel to Churchill Way West, turning north to follow the line of the exit road from the Leisure Park. Appendix J shows the diversion route.

In addition the mapping records show the water main running along the southern 6.1.13

and eastern sides of the site. A diversion route for this section is also available in Appendix J.

As outlined earlier South East Water has not advised any detailed or budget costs 6.1.14

for any diversion works at this stage. However, using data from other projects it is estimated that the cost of the diversion works would be in the region of £250,000. This would include the excavation of trenches in soft landscape and reinstatement, but would exclude any subsequent planting or enhancement of landscaping.

This figure is an approximate order of cost only and assumes that South East Water 6.1.15

would agree to undertake the diversion works on these two major mains; a detailed quotation should be sought from South East Water should the option be considered further.

It should be noted that a long lead-in time is anticipated on works of this nature, 6.1.16

possibly in excess of six months from acceptance of a quotation.

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POTENTIAL SITE USES 7.0

Based on the information available at the time of writing this chapter considers the 7.1.1potential site uses.

The following land uses are considered appropriate for the site based on the site 7.1.2

location and the flood risk vulnerability. These land uses will require the FRA due to the size of the site, but the FRA will not need to be as detailed as the FRA required for the more vulnerable uses.

• Police ambulance and fire stations (not required to be operational during flooding)

• Shops, financial, professional and other services

• Restaurants, cafes and hot food takeaways

• Offices

• General industry

• Storage and distribution

• Assembly and leisure

The following land uses are considered appropriate for the site based on the site 7.1.3location and the flood risk vulnerability. These land uses will require the FRA due to the size of the site, but the FRA will need to be more detailed as the land use is classified as more vulnerable.

• hospital

• residential development, including care homes, prisons and hostels

• health services, nurseries and educational establishments

Based on the information available at present, it is considered unlikely that the site 7.1.4would be used as residential, given the land uses of the surrounding area. A care home may be an option, however it is considered more likely the site would be used for industrial or mixed use, which is more akin to the land uses in the surrounding area. A care home would require a more detailed FRA due to the increased vulnerability over industrial or mixed use, however the remaining further investigations relating to the different options will be the same. Further investigations recommended are discussed later in this report, in Section 9.0.

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POTENTIAL SITE CONSTRAINTS 8.0

8.1 Site south of Churchill Way West

Based on the findings of this report, the following lists the potential site constraints: 8.1.1

• Likely access point off Churchill Way West

• Level difference between Thornycroft Lane and Grafton Way if an access is considered from Grafton Way

• Potential (although low probability) of contaminated land, associated with the nearby filling station and historic uses of nearby land

• Main river running through site – works within 8m of this will require EA flood defence consent

• A Sequential Test will be required to demonstrate that there are no reasonably available sites at a lower risk of flooding that would be appropriate for the type of development or land use.

• An FRA will be required due to the size of the site, but may also be required to justify the flood risk to more vulnerable uses, depending on classification of proposed use

• Detailed hydrological and hydraulic modelling may be required

• Steep banks along boundaries may restrict area that can be developed and some re-grading of the site may be required

• An electricity substation is located on the site – this would need to be considered in the site layout, however it may be possible to relocate it within the site if required

• A foul sewer appears to run across the site in a north south direction, which is above ground. This will affect the site layout, or require diversion works.

A plan of the site constraints is shown in Appendix K. 8.1.2

8.2 Site north of Churchill Way West

Based on the findings of this report, the following lists the potential site constraints 8.2.1should this alternative option be taken forward:

• Likely access point off Churchill Way West

• Major water main relocation would be required, estimated cost is approximately £250,000

• A surface water attenuation basin would have to be relocated to the site south of Churchill Way West. This would require hydraulic modelling.

• An FRA will be required due to the size of the site, however the site lies outside the floodplain therefore all potential uses of the site would be appropriate from the point of view of flood risk

• Re-grading of the site may be required

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FURTHER INVESTIGATIONS 9.0

Due to the proximity of the filling stations to the site there is a low possibility of 9.1.1contaminated land. It is understood that hydrocarbon contamination has been encountered the Thornycroft Industrial Estate. In addition there may be contamination present on site due to historic land uses in the area. It is therefore recommended that a contaminated land desk study is carried out.

Piled foundations are likely to be required, however a site investigation will be 9.1.2

required in order to accurately determine the underlying geology and its influence on the foundations and building structure of any proposed development.

A Sequential Test will be required in accordance with PPS25, in order to show that 9.1.3

there are no alternative, available sites with lower flood risk that are appropriate for the proposed development. Following this, a detailed Flood Risk Assessment will be required to show that the residual flood risk is acceptable. As part of the Flood Risk Assessment detailed hydrological and hydraulic modelling may be required.

Discussions with South East Water are required to obtain a more accurate 9.1.4

indication of the costs of diversion and in order to establish South East Water support for the proposed diversion.

Discussions with the relevant utility companies are recommended to determine the 9.1.5

cost of new connections to serve the site and whether sufficient capacity exists within the existing infrastructure to accommodate any proposed development.

Works within 500m of a pond will require ecological surveys to establish whether 9.1.6

Great Crested Newts are present. Therefore, should the attenuation basin be relocated, newt surveys will be required. In addition other ecological surveys may be required, such as bat surveys, reptile surveys and dormouse surveys, however it is recommended an ecologist is consulted regarding any potential ecological requirements. A phase 1 ecology survey, comprising a walkover and report detailing any further recommended actions is likely to be required. The constraints associated with the timings of ecological surveys are set out in Appendix L.

The estimated costs associated with further investigations are set out as follows: 9.1.7

• Contaminated land desk study £2,000

• Site Investigation £3,000-£3,500

• Phase 1 Ecology survey £1,000

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SUMMARY AND CONCLUSION 10.0

Upton McGougan Limited (UML) has been commissioned by Basingstoke and 10.1.1Deane Borough Council (BDBC) to produce an engineering options and appraisal report for a land parcel to the south of the Basingstoke Leisure Park.

The River Loddon, which runs through the site, is classified as a main river, 10.1.2

therefore the Environment Agency will require a flood defence consent for any works within 8m.

The topography of the site may mean that re-grading is required. 10.1.3

Further investigation is required to influence the design however it is likely that piled 10.1.4

foundations will be required.

The risk of contamination should be considered. 10.1.5

It is proposed that the site be accessed off Churchill Way West, by a left in/left out 10.1.6access arrangement.

A Sequential Test will be required, and a Flood Risk Assessment, will also be 10.1.7

required, which may include hydrological and hydraulic modelling.

Based on the flood risk it is considered that approximately 30% of the site 10.1.8(approximately 1ha) may be suitable for development however this should be considered further through a detailed Flood Risk Assessment. Plans included in Appendix M indicate the current indicative flood plain, together with a possible option of development within the flood plain coupled with the provision of compensatory flood storage towards the southern edge of the site.

The drawings mentioned in 10.18 above do not increase the amount of potentially 10.1.9

developable area, however, they do bring the area into one useable block rather than two disparate sections.

The works involved in carrying out the proposals in 10.1.8 above would essentially 10.1.10be the regarding of the ground levels to relocate the potential flood plain from the centre of the site to the southern end of the site. The work would entail raising the ground level of the area shaded grey by approximately 1.2m and the subsequent reduction in the level of the brown hatched area by approximately 700mm (subject to detailed design) This earthmoving exercise is likely to cost in the region of £150,000 based on similar projects.

In addition to the earthworks described above, it would be necessary to carry out an 10.1.11ecology survey and determine if any mitigation measures are necessary, in order to preserve or enhance the biodiversity of the aquatic and surrounding wetland habitat.

A recent visit to the site towards the end of April 2012 it was found that there was 10.1.12minimal water in the watercourse and the remaining areas of the site were dry. It should be noted for the record that April 2012 was recorded as being the wettest April on record since 1920.

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A foul water sewer crosses the site, above the surface, which may affect the site 10.1.13layout, or require diversion. Budget costing’s of £85,000 have been included.

New connections will be required for all services, subject to sufficient capacity 10.1.14existing within the networks. A major water main diversion will be required to develop the site north of Churchill Way West, the cost of which is estimated at £250,000.

Based on the available options, it is considered the site is most appropriate for 10.1.15industrial or mixed use development.

This report also sets out site constraints for both potential sites, as well as 10.1.16recommended further investigations.

Land South of the Leisure Centre Upton McGougan Ltd

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May 2012

Appendix A : Topographical survey

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Appendix B : Borehole Record and Location Plan

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Appendix C : Envirocheck Report

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Appendix D : Flood Screening Study

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Appendix E : Thames Water Sewer Records

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Appendix F : SSE Mapping Records

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Appendix G : Gas Mapping Records

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Appendix H : Telecoms Mapping Records

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Appendix I : South East Water Mapping Records

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Appendix J : Probable Route of any Water Mains Diversion

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Appendix K : Site Constraints

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Appendix L : Timings for ecological surveys

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Appendix M : Approximate Area Of The Site Suitable For Development