New Airfield Neighbourhood WESTON PARK - IEMA · informal grassland management. To the south . page...

WESTONPARKN e w A i r f i e l d N e i g h b o u r h o o d

Prepared by Pegasus Planning Group LLP | Persimmon Homes (Special Projects) Ltd | February 2010 | P.0567_59

N o n - T e c h n i c a l S u m m a r y

Contents

Introduction 2 Proposed Development 4 Planning Policy Context 6

Socio Economic Issues 7

Landscape and Visual Issues 8 Ecology & Nature Conservation 10 Archaeology and Cultural Heritage 12 Traffic and Transport 14

Noise Environment 15 Air Quality 16

Water (Drainage, Flood Risk and Hydrology) 18 Geotechnical Issues and Contaminated Land 21 Conclusion 23

Page No.

Ref: P.0567.59Date: February 2010

COPYRIGHT: The contents of this document must not be copied or reproduced in whole or in part without the written consent of Pegasus Planning Group



2 page



Introduction

and south-east the application site is bordered by agricultural fields predominantly laid to pasture and to the south-west there are industrial and business units utilising buildings associated with the former RAF base.

The northern boundary is clearly defined by the Weston-super-Mare to Bridgwater railway and associated track side vegetation composed of a dense screen of shrubs and trees. Apart from the corridor which extends east to the A371 to cover the alignment of the future Cross Airfield Link (CAL), the eastern boundary is a physically undefined line from the railway line to intersect with the former airfield’s runway and passing to the Great Cross Rhyne.

The southern boundary is similarly physically undefined, running parallel to the industrial units housed in the extant aircraft hangers and ancillary buildings of the former RAF base.

This document summarises the findings of an Environmental Statement (ES) which accompanies an outline planning application submitted by Pegasus Planning Group LLP on behalf of Persimmon Homes Ltd (led by Persimmon Special Projects Western) to North Somerset Council in connection with land at the former Weston Airfield (WAF), Weston-super Mare (WsM) known as Weston Park.

The new application is designed to complement the proposals already considered by North Somerset Council (NSC) for Business, Industry and Infrastructure and other Engineering Operations (NSC Ref 07/P/1950/0). The Council has granted planning permission for the development at WAF for Weston Park Business Quarter, Weston Park Industrial Quarter and Infrastructure and other Engineering Operations.

Site Context and Location

The planning application covers 78.5 hectares in the north and western quadrant of the former Weston Airfield (WAF). The location of the application site is illustrated on and in the ES. The site includes part of the former runway, dispersal roads and hardstandings, buildings and old sidings and platform. There are also open areas of land including scrubland/trees along rhynes and some grass land within the site. The site is previously developed land.

The site is bordered by industrial and commercial uses to the south, west and north-west. To the east the site is bordered by the remaining former operational area of the WAF; now under informal grassland management. To the south



Introduction

Site Location Plan

4 page



Within the dwellings proposed, a range of house types, sizes and tenures are envisaged in order to accommodate a variety of households. The scale of development provides the opportunity to incorporate a mix of housing styles. The proposals will include buildings to form groups that relate with one another using a coordinated range of materials and detailing. As found within traditional townscapes, a hierarchy of dwellings is proposed ranging from large buildings and detached properties through to smaller terraces.

An element of affordable housing will be provided within the development in small clusters and may include social rented, shared ownership and low cost/reduced cost market housing, details will be agreed through consultation with the Planning Authority.

Public open space provided has been designed in order to cater for the recreational needs of the new community at the WAF and a new rhyne and swale network will link new greenspaces and create new wildlife corridors and diverse ecological habitats.

The site is anticipated to provide up to 900 dwellings, together with a local centre and primary school located in a central position within the airfield site to support future residential development within the (WAF). The assessments detailed in the ES are based on the layout and broad features given in the Parameters Assessment Plan on . This locates the position of various proposed land uses within the new development across the study area.

The urban form and structure of the development proposal respond to the historic alignment and new alignment of rhynes and swales that form a connected sustainable drainage system draining to the new wetland area. Three play areas are provided within 240m walking distance of all new dwellings and sports pitches are located within the Linear Landscaped Park and adjoining the proposed primary school. The primary school and local centre are located at a key node on the CAL allowing good accessibility within the new development and the location also ensures benefits for passing trade. A range of density areas will be created in the proposals to ensure areas of different character. The overall average density will be 40dph. Mitigation planting will be provided adjacent to the railway in a landscaped open space buffer. This landscaped buffer connects with the rhyne and swale network to provide wildlife corridors and attractive pedestrian/cyclist routes through the development. An area for temporary earthworks storage will be included within the site as required.

Proposed Development

Key



Proposed Development

Parameters Plan

6 page



Planning Policy Context

have yet to be adopted it can be seen that the proposals are consistent with the emerging policies for the area. It is anticipated that through the development control process suitable mechanisms can be put in place to ensure that housing is delivered in step with jobs to ensure that the proposals positively contribute towards the employment led regeneration and enhanced self containment of WsM.

An assessment of the relevant Planning Policies has been undertaken for the Application Site. It has reviewed relevant National Planning Policy Guidance and considered the policies contained in the Development Plan for the area, which comprises Regional Planning Guidance for the South West (RPG10), The Joint Replacement Structure Plan (JRSP) and the North Somerset Replacement Local Plan (2007). Regard has also been had to the emerging policies and provisions of the Regional Spatial Strategy for the South West and the North Somerset Core Strategy.

National planning guidance and the Development Plan Policies for the area advocate the principles of sustainable development which includes focusing development in and adjacent to major urban areas, particularly where there are opportunities for development on previously developed land and reducing the need to travel. WsM has been identified as a location where development will continue to be focused. Adopted and emerging policies for the town seek to secure employment led development which can assist regeneration at the town and address the imbalance between housing and jobs which gives rise to unsustainable patterns of out commuting.

The application proposals when considered alongside the existing commitments for employment development at WAF which they aim to unlock, accord with the policies for the area. The emerging RSS now establishes the need for additional housing at WsM beyond the plan period of the adopted Local Plan and this is further confirmed by the emerging North Somerset Core Strategy. Whilst these plans



Socio Economic Issues

The development provides for appropriate supporting uses in the form of a primary school, local centre and areas of open space for recreation and amenity to meet the day to day needs of the development. Contributions are likely to be the subject of negotiations to secure other improvements to public transport and community facilities where necessary.

Overall the development would represent a significant step forward in the strategy for employment led regeneration at WsM. The socio economic impact of the development would be positive and would be of significant benefit to WsM and the wider sub region.

Planning permission has recently been granted for 29.5ha of employment development and related infrastructure at WAF which is intended to make an important contribution to the employment led regeneration of WsM. The proposed residential development of 900 dwellings will provide the necessary funding to facilitate the early delivery of the employment development. When taken together these developments would represent the first phase of the planned Weston Urban Extension.

The combined proposals would have a significant and positive impact on the area by redeveloping a largely redundant previously developed site to meet the identified need for jobs and new homes in WSM. The proposals would also fund the Cross Airfield Link Road which is of strategic importance to the transport network (including public transport) of WsM.

The proposals would unlock the potential to create over 2,500 jobs at WAF with further jobs likely to be created with future phases. This would make an important contribution to the supply of jobs in WsM and provides the opportunity to enhance the self containment of the town and reverse unsustainable outward commuting patterns.

8 page



Landscape and Visual Issues

The removal of certain features to be replaced by built form, would affect a minority of landscape resources, which would be compensated by the replacement of landscape features such as tree and hedgerow planting, as part of the development proposals.

Where visual receptors are within a rural context looking north and west towards the study area, the effect of the proposals would be to bring the urban edge closer to the viewer. Sympathetic planting within built areas on streets and in areas of public open space, would help to screen elements of the development. For receptors within an urban fringe context looking south across the study area, their views would not change dramatically as the site is seen in an urban dominated context.

Mitigation Measures

The mitigation of the effects on landscape and the character would aim to re-create the inherent landscape features that contribute to local character and distinctiveness and the development itself would occur in an area where there is evidence that the local character has already become degraded through urban fringe influences. The development therefore has the capacity to improve the immediate landscape character of the site.

Method of Assessment

A comprehensive landscape and visual assessment has been conducted to establish how the visual amenity of the town and surrounding countryside of WsM and its neighbouring settlements would be affected by the proposals and how the landscape infrastructure of the study area would be altered in terms of character and appearance.

Existing Situation

The study area is a landscape which has a transitional character that relates to both the urban fringe of WsM to the north and west, the more open the landscape to the east, and the semi-rural areas to the south beyond the existing employment uses. The northern half of the study area is heavily influenced by urban fringe uses such as the former tip/landfill site, the main line railway, commercial premises, and major roads. The southern part of the study area retains some agricultural use but is still influenced by the large village settlements of Locking and Hutton and the western neighbourhoods of WsM. The majority of views of the study area are limited to medium to close range view points from within the study area.

Potential Effects of Proposed Development

Proposals to extend the urban fringe across the application site would relate well to the pattern of existing development, providing scope for some positive enhancement of the appearance of the urban fringe. The east and south-east of the application site would be retained as wetland and a buffer of open space, which would be seen as a continuation of the Moor landscape.



Mitigation of visual effects would not aim to totally screen the development from views by dense planting, as this would be at variance with the local character of the landscape. Therefore, the mitigation strategy looks to improve the appearance of the urban fringe and with partial screening of the development, thereby providing an attractive setting for those who currently reside in the area.

New Situation

A new high quality mixed use scheme would provide a new attractive urban edge to WsM. Set within a strong landscape framework, the scheme would also provide new facilities for the community, including areas of public open space and extensions to the local footpath network, allowing for greater access to the public open space on the urban fringe. The proposals would be in accordance with planning policy as it relates to landscape issues, safeguarding environmental assets which contribute to the local area and would include for the production of a long term landscape and ecological management plan that would help ensure the Landscape Masterplan optimises its ability for mitigation.

Landscape and Visual Issues

Junction of Canada Coombe and Hutton Hill looking north-west

10 page



Ecology and Nature Conservation

the presence of bats, since these trees would be retained within the development footprint. Overall, the habitats within the application site were considered to be of limited nature conservation value. The Cross Rhyne was found to support a valuable flora and is likely to support important fauna such as invertebrates, fish, water shrew and otters, and as such, was considered to be of some nature conservation importance.

Likely Effects

The majority of the semi-natural habitats, which are considered to be of limited value to nature conservation, within the application site would be lost as a result of the development proposal. In addition, the proposal would lead to the loss of habitat suitable for use by protected species such as reptiles and nesting birds. Despite habitat loss there will be a net gain of hedgerows. New semi-natural habitats would be created as part of the development proposal both within the development footprint and within a proposed wetland area. Once the planting matures, these habitats will compensate for the habitats lost.

The proposal would lead to the loss of small areas of bank habitat on the Cross Rhyne when two outfalls are created. There is also the potential for indirect effects on flora and fauna within the rhyne, if surface water from the construction site enters the rhyne before sediments or other pollutants have been removed (including plant nutrients that naturally occur in the soil) and before water flow rates have been controlled. These effects could lead to a Significant Adverse impact on the flora and fauna within the Cross Rhyne during

Introduction

The potential ecology and nature conservation impacts associated with the proposed development of the application site on habitats and species have been assessed. The results of field surveys and a review of existing information relating to the application site and its surroundings have informed an assessment of baseline conditions for the proposals.

Baseline Conditions

The studies and surveys revealed that there were no designated sites of nature conservation importance within or adjacent to the application site. They also revealed that the application site comprised an area of previously developed land that supported scrub, trees and tall herbs, a series of small fields bounded by tall unmanaged hedgerows associated with ditches (most of which were dry), areas of dense scrub and a part of the airfield grassland. The site was bounded to the north by the mainline railway, to the west by the Winterstoke Road, to the east by the remainder of the airfield and to the south by an industrial estate or the major rhyne (drainage ditch) known as the Cross Rhyne.

The surveys revealed that the grassland and hedgerows were species-poor and supported small numbers of nesting birds. Small numbers of slow-worms and grass snakes were recorded in the field margins, and areas of suitable habitat were recorded throughout the application site. Three of the mature trees within the application site appeared to contain features potentially suitable for use by roosting bats. Further surveys have not been undertaken to confirm



construction, but the flora and fauna would be expected to recover once the source of pollutants has been removed. Once the application site has been developed, the Cross Rhyne would form part of a sustainable drainage system. Thus, the release of surface water into the Cross Rhyne would be controlled and appropriately treated and it is not likely that there would be any further effects on the flora and fauna which this rhyne supports.

Mitigation Measures

Measures will be put in place at an early stage in site clearance to ensure that water quality in the Cross Rhyne is protected throughout the construction phase. The sustainable drainage system that would be created during the construction phase would ensure that water quality within the Cross Rhyne would be protected throughout the life of the development. Pre-construction surveys will be undertaken to ensure that appropriate measures are taken to avoid any impacts on otters in the unlikely event that a resting site is identified.

Mitigation measures have also been proposed to ensure that badgers, reptiles and nesting birds are not adversely affected by the proposals. This includes careful timing of site clearance works and the creation of new habitats or features to replace those lost to development.

The newly created habitats within the residential area will compensate for the habitats lost to development as the plantings mature. The new wetland area represents an opportunity for the development proposals to create habitats of significantly greater value to nature conservation

than those that would be lost as a result of the development. The future management of this area would need to be secured.

Conclusion

The field surveys and desk study revealed that there were no Key Ecological Receptors within the application site. There is one Key Ecological Receptor immediately adjacent to the application site which is the rhyne immediately adjacent to the southern boundary of part of the site. This is known as the Cross Rhyne which is considered to be of ‘District’ importance for nature conservation. Assuming mitigation measures to protect water quality in the Cross Rhyne are successful the development proposal would not have any adverse effects on the Cross Rhyne and its valuable flora and fauna.

There is the potential for the development proposal to be beneficial to nature conservation as the newly created habitats within the development area mature. The habitat creation measures that are included as part of the development proposal will contribute to Biodiversity Action Plan targets for species-rich grasslands and may also contribute to targets for standing water and ‘Coastal and Floodplain Grazing Marsh’. In addition, the new wetland area represents an opportunity to create habitats that are of greater value to wildlife than those that currently exist on the application site, thus there is the potential for the development proposal to be of Significant Benefit to nature conservation.

Ecology and Nature Conservation

12 page



Archaeology and Cultural Heritage

Likely Effects

Without any form of mitigation, the development is anticipated to have a significant adverse effect on the current archaeological resource within the site during the construction phase, as a result of extensive stripping of topsoil and subsoil and groundworks for new foundations, services and landscaping.

Indirect effects on the setting of archaeological sites in the surrounding area, including Scheduled Monuments, are not considered to be significant.

Without any form of mitigation the development is anticipated to have a low to medium adverse impact upon the setting of the locally important Bristol Aircraft ‘Shadow Factory’ and other surviving airfield structures.

The development has been assessed not to have a significant effect on the setting of listed buildings within Hutton or Lodwell Farm; the development will not have a significant effect on the character and appearance of the Hutton Conservation Area

Introduction

The potential impacts of the proposed development on archaeological remains and built heritage resources have been considered. Existing site conditions have been established through review and analysis of currently available information, site walk-over surveys, geophysical survey data, the results of a watching brief on geotechnical works and analysis of LiDAR data. From this the anticipated effects of the development are gauged, taking into account the severity of the anticipated change and importance & sensitivity of the affected resource.

Baseline Conditions

The site does not contain any sites or areas subject to National Heritage designation as a Scheduled Monument, Listed Building, Registered Battlefield, Registered Historic Park/Garden. The site is not within or adjacent to a Conservation Area.

The only known archaeology within the application site relates to the modern use of the site as an airfield and to the Bristol Aircraft ‘Shadow Factory’ mainly to the south of the proposed development area. The site is also known to contain palaeochannels, which are visible on the Environment Agency’s LiDAR data and also on the geophysical survey plots. The date and state of preservation of the material within the palaeochannels is not known, nor is it known if there is any associated earlier prehistoric activity. The site has been assessed has having a low potential for remains of all periods except for the Roman and post-medieval periods, where the potential is medium and for the modern, aviation phase, where the potential is high.



Archaeology and Cultural Heritage

Mitigation

The Archaeological Officer of North Somerset Council, Vince Russett has recommended that the impact of the proposed development upon the site’s archaeological resource can be mitigated by a conditioned scheme for an ‘augmented watching brief’. This would allow all below groundworks within the site to be monitored and would allow for the excavation and recording of all below ground remains and also investigation, as appropriate of the airfield related archaeology.

The indirect impact upon the Bristol Aircraft ‘Shadow Factory’ and other surviving airfield structures can be mitigated by a conditioned scheme of pre-commencement building recording at RCHME level 2, seeking to record not only the interiors and exteriors of the buildings themselves, but also recording them within their broader airfield context.

14 page



Traffic and Transport

In summary, the proposed mitigation measures include:

• The implementation of measures aimed at reducing the impact from construction traffic on the local highway network;

• The establishment of a comprehensive integrated pedestrian and cycleway network connecting to existing networks;

• The promotion in conjunction with bus operators of a high quality bus-based public transport system serving the proposed development and Weston Park, taking full advantage of the new link road (CAL) between Winterstoke Road with the A371 Locking Moor Road providing a sustainable transport corridor;

• A Travel Plan to provide a framework to promote sustainable travel patterns and behaviour; and

• Financial contributions towards existing and/or new bus services.

Overall, the TA has identified and analysed the transport impacts of the proposed development at Weston Park. Pedestrian, cycle and public transport measures are proposed which will achieve the objectives of ensuring the proposed development is sustainable in transport terms. Mitigation measures have been identified that will ensure that the additional travel demands from the proposed development will be satisfactorily accommodated on the local transport networks.

A Transport Assessment (TA) has been produced for the proposed residential development at Weston Park which has considered the demands that the proposed development, comprising the Residential Quarter, a Local Centre and Primary School, will place on the existing transport network.

The TA has examined all modes of travel with the emphasis placed on encouraging sustainable modes of travel. In assessing the transport effects arising from the proposed development, the TA has made use of the G-North Somerset (G-NS) Highway Model.

The TA has reviewed existing traffic conditions on the local highway network, existing public transport services in WsM and existing and proposed pedestrian and cyclist facilities in the vicinity of the application site.

The proposed development will give rise to an increase in travel demand, resulting in an increase in traffic flows on the surrounding highway network; an increase in the demand for public transport and an increase in the demand for pedestrian and cyclist routes.

The focus for mitigation is on the need to reduce travel by private motorcar in favour of more sustainable modes of travel.



Noise Environment

There is no anticipated adverse impact from noise associated with air traffic movements.

The road traffic generated by the development is low in comparison with existing traffic flows. Therefore the increase in road traffic noise will result in an impact of neutral significance and no mitigation is recommended

There are no significant constraints in terms of noise upon the proposed primary school, although noise mitigation measures will need to be considered in the design of this element of the development.

A series of outline noise mitigation measures have been recommended capable of achieving an acceptable noise climate in noise-sensitive areas of the proposed development. Subject to the recommended noise mitigation measures, there will be no unacceptable residual adverse noise impact to proposed residences on the development and there will be no unacceptable residual adverse noise impact from the development to existing nearby residences.

A noise impact assessment has been carried out in connection with the proposed residential development. The assessment has involved measurement of the ambient noise climate at appropriate locations on the application site as well as the use of appropriate predictive techniques.

There is potential for temporary, local, adverse impact from construction noise and appropriate mitigation is recommended.

The boundary of the proposed residential development area of the site with Winterstoke Road to the west, the Cross Airfield Link road to the south and the railway line to the northwest fall into Noise Exposure Category B of Planning Policy Guidance 24 (PPG24). An adverse noise impact of minor significance is therefore anticipated such that some noise mitigation measures will be required for new residences at positions close to these existing noise sources.

There is the potential for an adverse impact of indeterminable significance from the permitted Industrial Quarter to the south of the application site if noise mitigation measures are not applied. It is anticipated that potential noise impact will be controlled by way of appropriate covenants on the use of the Industrial Quarter. Further mitigation measures to new residences at positions close to this potential source will improve control of noise impact and/or increase flexibility of use of the Industrial Quarter.

16 page



Air Quality

An assessment of road traffic emissions on the road network surrounding the site was carried out using the Design Manual for Roads and Bridges (DMRB) screening tool. This assessment did not include traffic generated by the development. The results indicated that road traffic impacts at the existing assessed locations would not result in any of the relevant Air Quality Objectives being breached, and that air quality was suitable for the introduction of potentially sensitive uses at the site.

Likely effects

An assessment of road traffic emissions, including traffic generated by the proposed development, on the road network surrounding the site was carried out using the DMRB screening tool.

The results indicated that levels of NO2 and PM10 were forecast to comply with the relevant Air Quality Objectives at all assessed locations. This confirms that the site is suitable for the introduction of potentially sensitive uses. The predicted increase in vehicle movements was accompanied by a resultant increase in pollutant emissions. The significance of the increase in pollutant levels at all assessed locations was deemed “negligible”.

A qualitative assessment of the potential impact on local air quality associated with the construction/demolition phases of the proposed development shows that although impacts are likely to occur from site activities, these can be reduced through appropriate mitigation measures. The site is designated as “high risk” under best practice guidance. Depending on

Introduction

An air quality assessment has been undertaken to identify whether the proposed site was suitable for potentially sensitive uses with regard to air quality (i.e. introduction of new residential dwellings and school) and whether the proposed development scheme is likely to have an impact on existing levels of air quality.

A qualitative assessment was also made of the potential impacts on local air quality during the demolition and construction phases of the development, with specific focus being on emissions of dust and from site plant.

Baseline conditions

Through reporting carried out under the requirements of the Local Air Quality Management process (Part IV of the Environment Act 1995), North Somerset District Council (NSC) concluded that levels of pollutants were not expected to exceed the relevant Air Quality Objectives at any potentially sensitive locations across the district. However, the assessment was carried out with specific focus on levels of nitrogen dioxide (NO2) and particulate matter (PM10), which are two pollutants commonly associated with road traffic emissions.

Industrial processes regulated by the Environment Agency and NSC under the Environmental Permitting Regulations (EPR) have been identified in the vicinity of the application site. These processes are located a sufficient distance from the site, with existing residential properties in between, and they are unlikely to have a significant impact on air quality at the site.



An assessment of the potential impacts on local air quality of the construction/demolition phase of the development was carried out. Mitigation measures related to emissions of dust and from site plant were recommended. Measures such as these would normally be sufficient to reduce emissions to air from the construction/demolition phase to a minor impact.

It is therefore concluded that the Weston Airfield site is suitable for residential development from an air quality perspective, and will not cause a discernible impact on local air quality as a result.

meteorological conditions, potential air quality impacts may be experienced at nearby residential properties off Winterstock Road to the west, on Hutton Moor Lane to the north, and residential and camping locations off Laneys Drove to the east. Hence some degree of impact is possible if activities are not properly mitigated.

The energy source for the proposed development has not yet been confirmed. As a result, it has not been possible to comment on any potential residual impacts on local air quality from this source.

Mitigation

The predicted impact of road traffic emissions on local air quality, as a result of the proposed development has been classified as “negligible”. On this basis, no further mitigation measures are proposed.

A suite of appropriate mitigation for “high risk” sites set out in best practice guidance has been recommended for use during the construction/demolition phase of the development.

Conclusions

The results of the baseline survey and air quality assessment were in agreement with work carried out by NSC, indicating that levels of air pollutants at the proposed development site, and in the vicinity of the site, comply with the relevant Air Quality Objectives.

The increase in levels of air pollutants as a result of additional vehicle movements on the local road network generated by the proposed development has been classified as “negligible”.

Air Quality

18 page



Water (Drainage, Flood Risk and Hydrology)

The existing water quality of the rhynes within the Site Boundary was tested by sampling both groundwater and rhyne water across the site. There are no rivers in the site to assess by the Environment Agency’s General Quality Assessment (GQA).

Baseline Conditions

Surface water draining the airfield site currently flows into the Cross Rhyne (ditch) along the southern boundary of the airfield. There is little existing site stormwater drainage, with drainage off the site’s impervious areas likely to be directly into the existing rhynes. The flood depth across the site is typically 120mm in the 1 in 100 year event, however much of the western area of the airfield is above the 1 in 100 year level. The site is protected by coastal defences approximately 2km west of the site. There are no aquifers used for public water supply underlying the site and the site is not within a Groundwater Protection Zone (GPZ). Therefore, any impacts on groundwater result from the percolation of surface water. The quality of the water within the on-site rhynes, has been compromised by diffuse pollution arising from industrial use of the Site and agricultural use of the airfield and the catchment upstream.

The impact of the proposals on hydrology, drainage and flood risk have been considered. The hydrology, drainage and flood risk aspects of the Weston airfield area were subject to a detailed appraisal in 2007 in respect of the now Consented Employment Development. The new assessment builds on the 2007 work and is fully consistent with the strategic approach adopted in 2007 (which considered the whole of the airfield and not just the immediate application areas). A separate Flood Risk Assessment (FRA) which includes details of the design requirements and the approach to flood management and drainage has also been produced for the proposed development.

Assessment Approach

A hydrological analysis of the Uphill Great Rhyne catchment has been carried out to enable the 1 in 100 year flows to be assessed for the FRA report. Detailed hydraulic modelling of the system has been undertaken to assess the existing flood levels on the site, with the results being validated against historical flooding reports. Using this hydraulic modelling the existing flood risk at the site has been quantified, to provide baseline conditions for the development design. The potential flood risk of the development design has also been assessed using a modified hydraulic model and based on guidance contained within Planning Policy Statement 25: Development and Flood Risk.




The existing rhynes will need to be realigned and some replaced by alternative arrangements in order to conform to the layout. The nature of site preparation during construction will include significant earth-moving and the use of potentially polluting materials such as concrete, fuels etc. Without mitigation, this would potentially make the site vulnerable to spillages from construction plant, damage soil structure and possibly adversely affect on water quality during periods of rainfall, when material may be washed off into watercourses). During the operational phase of the development, surface water contamination from vehicles (via the general use of car parks and roads) or runoff, is likely

The overall design concept of the proposed development makes a feature of grass swales and rhynes (reflecting their cultural significance in this part of Somerset). The design of the development has considered the need to improve the water environment in terms of chemical, nutrient and aesthetic quality and is also intended to increase the biodiversity of the water environment on-site from the existing low diversity. Therefore, there are extensive mitigation measures that have been proposed.

Key Impacts and Likely Significant Effects

The works primarily involve the raising of the site from approximately 5.0m AOD to 5.4-5.73m and the construction of rhynes and swales to provide effective drainage. As the site is developed a wetland area will be constructed to provide further floodplain storage. The construction process will require the use of large earth moving plant, and the stockpiling of soil. During construction, material will be excavated and stockpiled within the study site and this will alter the flooding profile of the site, however, it is unlikely to alter the overall impact of any flood event that occurs during the construction phase of works.

Rhynes or other flood storage areas may need to be in-filled and replaced by alternative water and/or flood storage structures. During construction this could potentially increase the risk of flooding across the site. Mitigation measures can be put in place to minimise exacerbating the flood risk in the proposed development.

Assessments have shown that there is no significant risk from flooding from the sea. Therefore there are no measurable construction impacts.

20 page



Without mitigation it is likely that the chemical, ecological and aesthetic quality of the rhyne water would fall, particularly during warm weather due to the poor quality of the groundwater on the site and the poor quality of the water in the existing rhynes. This would result in the lowering of dissolved oxygen levels, insect propagation in stagnant water; algal blooms which look unsightly and can be toxic to humans and other animal life; and potential odour problems from black anoxic mud.

Mitigation

To prevent flooding occurring across the site, construction of flood storage areas should be completed before the infilling of the site with appropriate phasing of the works. Best practice construction site preventative will be employed. The Environment Agency Guidelines for Construction Works Near Watercourses will also be used to reduce the risks

Improved water quality will be achieved by refining the design to avoid standing water in the rhynes where this may impact on water quality by utilising an alternative solution such as the use of dry swales which is less vulnerable to the generation of a water quality nuisance. Provision of a constructed wetland will also help to improve the water quality as it leaves the site

During operation the surface water drainage system will be designed to be sufficient to contain and convey the design storm events (1 in 100 year including the considering the impacts of climate change). The proposed future rhyne system, including the location and operation of the storage areas, will be designed to ensure that

flood levels are not increased on the Cross Rhyne, as described in the Flood Risk Assessment. In addition road levels and property floor levels will be raised (with a freeboard allowance) above the 1 in 100 year design levels.

Flows entering the Cross Rhyne will be controlled to match (or be lower than) existing flows (up to and including the 1 in 100 year event), by a combination of the use of Sustainable Drainage Systems and on-site storage areas. Petrol/oil interceptors are proposed together with the inclusion of Sustainable Urban Drainage Systems and the provision of wetland areas.

Conclusions

There are known existing flooding problems and problems with poor water quality on the site and these have been identified by the testing and the flood report. The design of the layout has incorporated measures to deal with these issues and meet the requirements of the statutory agencies, such as the Environment Agency, whilst providing an effective layout. This Flood Risk Assessment which includes details of the design requirements and the approach to flood management and drainage provides further information.

The need to improve the biodiversity of the water environment, in particular, has also affected the development’s design and layout. The inclusion of Sustainable Urban Drainage Systems and the provision of wetland areas will all comply with best practice on sustainable development. There are additional opportunities (such as the proposed provision of water butts to homes) which will also be considered as the development proceeds.




Geotechnical Issues and Contaminated Land

Likely Effects

All the potential environmental impacts from the land and soils conditions at the site have been considered for the construction and operational phases of the development. This has been done by considering all the potential sources of harm, namely the substances and unstable ground present, all the things which could be harmed (known as the receptors) and the route or pathway by which the harm could impact the receptors. These have been assessed and any source-pathway-receptor linkages considered significant are deemed to be impacts. They are said to be unmitigated because they could occur if no mitigation measures were in place to prevent them. The unmitigated potential adverse impacts of minor or greater significant which were identified at the site are:

Construction phase:

• Effects of soil contamination on re-development workers and surface water in certain areas of the site;

• Effects of asbestos fibres on re-development workers and site neighbours in certain areas of the site;

• Spillage of fuel or other substances into the surface water during construction work; and

• Difficulties in working with low strength alluvial soils especially earthworks and traffickability.

Introduction

This assessment addresses the likely effects of the quality of the land on the proposed development and its eventual users, and any effects the development of this land might have on the quality of the land in the surrounding area. This relates to chemical contamination and to the physical nature of the soils and rocks present.

Baseline Conditions

The baseline conditions as of September 2009 have been determined by a series of investigations carried out between October 2004 and September 2009, including desk study and site investigation. The ground conditions comprise a low-lying, level site underlain by a significant thickness of soft, compressible soils that are part of a sequence of alluvial clays and peat deposited on the edge of the Severn Estuary. Mercia Mudstone bedrock occurs some 12-14 m below the ground surface. The ground elevation is approximately 5 mOD and the water table is close to the surface. The area is drained by a series of rhynes (ditches). The application site is a former aircraft factory and airfield, now occupied by a number of small businesses. The various activities of these land uses, plus fly tipping of waste, has resulted in contamination of the soils and the rhynes in certain areas (with metals and organic chemicals including petroleum hydrocarbons and solvents). In addition, there are close landfill sites near to the application site.

22 page



Conclusions

The contamination of soils and groundwater is not problematic and these can be dealt with using standard techniques which include removal of the localised, more highly contaminated areas and the covering of the site with clean soil. An integrated remedial strategy will be developed to ensure the required mitigation measures are put in place and are verified to the satisfaction of the regulatory authorities.

The physical ground conditions of soft compressible soils are not unusual and standard engineering methods will be used to design foundations etc. to prevent problems that could be caused by settlement of buildings, sewers, roads etc. to the satisfaction of the regulatory authorities.

It is important that the ground conditions relating to contamination and soil properties are dealt with in a combined way, for example so that earthworks do not spread contamination across the site.

Operational phase:

• Effects of soil contamination on site users and new planting in certain areas of the site;

• Effects of soil contamination on construction materials in certain areas of the site; and

• Effects on site users, buildings and infrastructure from soft, compressible soils.

Mitigation

Mitigation measures are proposed to address these potential impacts. These are the use of prescribed methods of working in the construction phase, including safe working practices and codes of practice.

Mitigation measures proposed for the potential impacts to operational phase receptors include additional investigation and assessment, especially in petroleum hydrocarbon and VOC contaminated areas within the industrial estate. This may show the need for selected removal of the more highly contaminated material. After this, the pervasive contamination will be dealt with by installing a clean cover, which will serve the dual purpose of raising site levels for flood protection.

Mitigation against operational phase geotechnical effects is essentially to use appropriate design measures for foundations, earthworks, roads, sewers, etc. to ensure settlements are within tolerable limits and that excavations, etc. remain stable and serviceable (such as new rhynes). This is standard engineering practice for alluvial soils.

There are no residual impacts.

Geotechnical Issues and Contaminated Land



Conclusion

The Environmental Statement demonstrates that there are no significant harmful environmental effects resulting from the proposals for the application site at Weston Airfield and there are no overriding environmental constraints or planning policies which would preclude the development of this application site.

All aspects of the design have taken full account of the likely significant environmental issues and, where necessary, mitigation measures form an integral part of the proposals to ensure that the environment is suitably protected. This comprehensive assessment demonstrates how the proposed scheme would bring about significant benefits such as newly created habitats within the development area, positively contributing to Biodiversity Action Plan targets and providing local amenities. The socio economic impact of the development would be positive and would be of significant benefit to WsM and the wider sub region.

web site: www.ppg-llp.co.ukPrepared by Pegasus Planning Group LLP | Planning I Environmental I Urban Design

Pegasus Planning Group LLPPegasus HouseQuerns Business CentreWhitworth RoadCirencesterGloucestershireGL7 1RT

Telephone: (01285) 641717 Facsimile: (01285) 642348

COPYRIGHT The contents of this document must not be copied or reproduced in whole or in part without the written consent of Pegasus Planning Group LLP

Crown copyright. All rights reserved, Licence number 100042093

New Airfield Neighbourhood WESTON PARK - IEMA · informal grassland management. To the south . page...

Documents

Transcript of New Airfield Neighbourhood WESTON PARK - IEMA · informal grassland management. To the south . page...