Bradford Road Corsham

Desk Study and Ground Investigation

Draft Report for

23rd August 2016 Hydrock Ref: R/C161464/001

Redcliffe Homes Desk Study and Ground Investigation at Bradford Road, Corsham R/C161464/001

Contents

1.0 INTRODUCTION ...... 1 2.0 PRELIMINARY INVESTIGATION (PHASE 1 STUDY) ...... 3 3.0 PRELIMINARY CONCEPTUAL SITE MODEL ...... 10 4.0 GROUND INVESTIGATION ...... 14 5.0 GROUND INVESTIGATION RECORDS AND DATA ...... 17 6.0 GEO-ENVIRONMENTAL ASSESSMENT...... 23 7.0 GEO-ENVIRONMENTAL CONCLUSIONS AND RECOMMENDATIONS ...... 28 8.0 GEOTECHNICAL ASSESSMENT ...... 30 9.0 UNCERTAINTIES AND LIMITATIONS ...... 36 10.0 RECOMMENDATIONS FOR FURTHER WORK ...... 38 11.0 REFERENCES ...... 39

Appendices Appendix A Drawings Appendix B Site Walkover Photographs Appendix C Historical Ordnance Survey Maps Appendix D Desk Study Research Information Appendix E Ground Investigation Plan, Exploratory Hole Logs and Photographs Appendix F Geotechnical Test Results Appendix G Hydrock Methodology Appendix H Contamination Test Results and Statistical Analysis Appendix I Mining Layout Plans

Hydrock Consultants ii Redcliffe Homes Desk Study and Ground Investigation at Bradford Road, Corsham R/C161464/001

Executive Summary and Conceptual Site Model

SITE INFORMATION AND SETTING

Report Purpose Phase 1 and 2 desk study, ground investigation and risk assessment undertaken at Bradford Road, Corsham.

Client Redcliff Homes Ltd.

Site Name and Land near Bradford Road, Corsham, Wiltshire, SN13 9LA, located at National Grid Reference 385170, Location 169890

Proposed It is understood that the site will comprise 170 residential properties with gardens as shown on SKL-01 Development Architect drawings dated July 2016.

PHASE 1 (DESK STUDY + WALK-OVER)

Current Land Use The site currently forms agricultural fields. and Description

Site History Two small structures and a pond were located on site and are shown to be removed/infilled by 1993. No other features of significance are shown on the site. Shafts associated with stone mining activities are evident off the site.

Unexploded A non-specialist UXO assessment indicates a very low bomb risk. No further consideration of UXO is Ordnance required.

Geology Available geological sources indicate the site to be underlain by the Forest Marble formation of which the upper beds comprise Mudstones and Cornbrash limestone. The southwest – northeast trending Corsham fault is shown over the sites south eastern boundary. Infilled ground is shown to the west of Skynet drive.

Mining or Mineral The Corsham area is known for significant surface and underground stone quarrying/mining. Available Extraction mining plans do not show any below surface quarry features below the site. The active Hartham Quarry complex is located immediately northeast of the site. The entrance to the Hudswell Quarry is located approximately 100m east of the site. This Quarry is reported to be no longer active. It is not known who has rights to quarry stone below the subject site. Two air shafts are shown approximately 70m west and southwest of the site. One air shaft located west of the site is not shown to link to any surveyed below ground quarry features. The air shaft located to the southwest of the site is shown to link to a shallow below surface quarry feature associated with Hudswell quarry.

Hydrogeology The Forest Marble formation is classified by the Environment Agency as unproductive Secondary A aquifer. The site is located on a Zone 2 Outer source protection zone.

Hydrology The nearest surface water feature is located approximately 180m north of the site.

Flood Risk The site is in Flood Zone 1 zone with a low probability of flooding. However, the site is shown on the EA data base to lie within an area which is susceptible to surface water flooding.

PHASE 2 – GROUND INVESTIGATION

Hydrock Site The Hydrock ground investigation comprised: Works  20 trial pits to a maximum depth of 2.40m bgl;  2 hand dug pits to a maximum depth of 0.40m bgl;  3 infiltration tests;  12 DCP – TRL probes;  chemical testing of soils, leachates; and,  geotechnical testing of soils.

Hydrock Consultants iii Redcliffe Homes Desk Study and Ground Investigation at Bradford Road, Corsham R/C161464/001

Ground Conditions Localised Made Ground in one location (TP19) at surface to 0.06m depth comprising black gravely sand Encountered with wooden debris and clinker fragments. Topsoil was encountered to depths of between 0.20 to 0.30m. (All Data) Residually weathered soil – to between 0.20m and greater than 2.30m bgl, generally comprising firm becoming stiff sandy medium to high plasticity CLAY, locally becoming clayey sand. Cornbrash Limestone of the Forest Marble Formation comprising medium strong light grey limestone beds. Possible infilled karstic features were encountered in multiple trial pit locations at depths of between 0.30 to 0.70m below the upper surface of the distinctly weathered Cornbrash formation. The thickness of these features ranged from between 0.15m to greater than 0.80m and generally comprised very soft, occasionally stiff, clays, silts and silty sand. If not karstic infill, this material may represent localised highly weathered horizons in the Cornbrash formation.

Groundwater Encountered No large inflows of groundwater were encountered during the ground investigation. However localised seepages and damp conditions were met upon in some locations below around 1m depth. (All Data)

GEO-ENVIRONMENTAL ASSESSMENT AND CONCLUSIONS

Conclusions of Human health: Contamination  No elevated levels of contaminants were encountered during the ground investigation. Generic Risk Plant growth: Assessment  Minor exceedances of Boron were encountered during the ground investigation. One exceedance of (All Data) Zinc was encountered within the natural soil. Controlled Waters:  Exceedances of Aluminium and Iron, were encountered during the ground investigation. Radon: (Including  The site is not in a Radon Affected Area. Guidance on Gas Construction materials: Protection  Plastic or bituminous products are unlikely to be at risk from contaminants on site. Measures) Water supply pipes:  Greenfield site with no significant contaminants of concern and standard pipework is envisaged. However, confirmation should be sought from the water supply company at the earliest opportunity.

Proposed No remedial measures are considered necessary at the site. Mitigation Measures

GEOTECHNICAL CONCLUSIONS

Obstructions There is a former development on the site comprising two buildings over the north western area of the site. Possible obstructions associated with this, including foundations, floor slabs and services should be anticipated. A possible relict basement feature, associated with the previous structures was observed over the north western area of the site.

Groundworks and Variable depths to rock head and rock horizons interbedded with soft clays were encountered over the Earthworks site. Some excavations into rock, with particular reference to service trenches and foundation excavations are may require the usage of heavy duty plant and breaking equipment to progress excavations.

Mine Workings There is the potential for un-surveyed quarry workings to be present beyond and beneath the western area of the site. Hydrock recommend that further ground investigation works, comprising boreholes and down-the-hole mapping be undertaken to identify whether quarry features are present.

Foundations The presence of soft infilled karstic features below shallow rock beds across the site (and the risk of mine workings) poses a significant risk to foundation design for the site. The below comments regarding foundations are provided as preliminary guidance assuming a favourable outcome of further investigation. However the presence of deeper karstic features/highly weathered horizons and potential underground mine workings underlying proposed development plots needs to be verified by further ground investigation works before final designs are made.

Hydrock Consultants iv Redcliffe Homes Desk Study and Ground Investigation at Bradford Road, Corsham R/C161464/001

On the assumption that the presence of karstic features are disproven below the maximum depths of penetration of this initial investigation strip/trench fill foundations bearing onto sound limestone rock at between 1.1m bgl and 2.50m bgl could potentially be adopted. A net allowable bearing capacity of 250kN/m2 could be achieved for this material. Should karstic features (or indeed shallow mine workings) be found present below these depths then either raft foundations or piled foundations should be considered. Due to the presence of cohesive beds within the limestone heave protection is likely to be required to accommodate tree influence. Further ground investigation works, comprising boreholes into the limestone bedrock are recommended for the site.

Ground Floor Slabs Suspended ground bearing slabs are recommended due to the presence of shallow medium to high volume change potential soils across the site. The potential influence of trees on shrinkable clays will also need to be considered for the design rafts

Road Pavement Based on in-situ TRL DCP testing and the plasticity characteristics of the shallow cohesive strata; an initial Design (CBR) design CBR value of 3% should be applied for natural fine soils. The limestone beds will offer a CBR of 5% when of significant thickness.

Soakaways Soakaway drainage is considered suitable for this site where chambers are sufficiently advanced into the limestone. However, the presence of infilled fine soils within the limestone bedrock is likely to provide less favourable infiltration rates in some areas. Indicative soil infiltration rates range from 3.45 x 10-4 m/s to 1.24 x 10-4 m/s in thick beds of limestone. Negligible where fine soils are prevalent. Further testing is recommended once soakaway locations are established.

Buried Concrete Design Sulfate Class - DS-1 and ACEC Class AC-1.

FUTURE CONSIDERATIONS

Uncertainties and The following uncertainties for the site remain. Limitations  The presence of Bath Stone mined quarries underlying the site; and  The presence of potential infilled karstic feature / softened weathered horizons within the Forest Marble formation.

Further Work The following further works will be required:  further ground investigation works to determine the presence or otherwise of underground quarry features below the site and provide information on the origin and distribution of possible karstic features underlying the site;  further assessment of the deeper geology to establish a final foundation design.  discussions with service providers regarding the materials suitable for pipework;  discussions with regulatory bodies regarding the conclusions of this report;  foundation depth in relation to trees assessment, following a tree survey to BS 5837:2012;  detailed design of foundations  Inspection of foundation excavations by a suitably qualified and experienced Engineer to confirm a suitable founding horizon.

This Executive Summary forms part of Hydrock Consultants Limited report number R/C161464/001 (Issue 1) and should not be used as a separate document.

Hydrock Consultants v Redcliffe Homes Desk Study and Ground Investigation at Bradford Road, Corsham R/C161464/001

1.0 INTRODUCTION

1.1 Terms of Reference

In June 2016, Hydrock Consultants Limited (Hydrock) was commissioned by Redcliffe Homes Ltd to undertake a desk study and initial ground investigation at Bradford Road, Corsham, Wiltshire.

The proposed development is to comprise 170 residential properties with gardens as shown on SKL-01 Architect drawings dated July 2016.

A site location plan (Drawing BDR–HYD–XX–D-001), a site survey plan and a proposed development layout are presented in Appendix A as shown on Drawing BDR–HYD–XX–D-002.

1.2 Objectives

The objectives of this investigation are to assess the ground and groundwater conditions to provide initial geotechnical design recommendations and to carry out a risk assessment of potential chemical contaminants to establish ‘suitability for use’ under the current planning regime.

1.3 Scope

The scope of work for this commission comprises:

 a desk study and site walk-over reconnaissance to determine the nature of the site and its surroundings including current and former land uses, geology, hydrogeology, hydrology and geo- environmental data.  an initial ground investigation including trial pitting, soil infiltration testing, Transport Road and Research Laboratory (TRL) probing, laboratory chemical and geotechnical testing; and  reporting on findings of the desk study, ground investigation, geo-environmental assessment of the site conditions and geotechnical interpretation of the ground and groundwater conditions. See Appendix G for detailed reporting methodology.

1.4 Provided Information

The following has been provided to Hydrock by The Client for use in the preparation of this report:

 SLR mining report (422.01918.00008 rev 1);  Brunel Survey Surveys topographical survey (12731-500-001);  BBA illustrative layout (3657/Oct 2015-08);  BBA location plan (3657/203); and  Land near Bradford Road, Corsham, Wiltshire Sitecheck Landmark report, report ref SAS_42268511_1_1, dated 31st October 2012.

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The Sitecheck report has been passed on to Hydrock by the Client. However, Hydrock have procured an updated Groundsure Geo Insight report for the site, dated 4th July 2016. 1.5 Approach

The work has been carried out in general accordance with recognised best practice as detailed in guidance documents such as the CLR 11 Model Procedures (Environment Agency 2004), the AGS (2006) Good Practice Guidelines for Site Investigations, BS 5930:2015 and BS 10175:2011+A1:2013. The technical details of the approach and the methodologies adopted are given in Appendix G.

A recognised phased approach has been followed, starting with a desk study and walk-over to produce a preliminary assessment of the site conditions and the important factors that require further investigation to reduce uncertainty.

Phase 2 comprises intrusive investigation work and testing. The factual data from Phases 1 and 2 are used to develop a conceptual site model (CSM). This comprises a ground model (of the physical conditions) and an exposure model (of the possible contaminant linkages). The CSM forms the basis for a number of risk assessments in accordance with current guidelines. Professional judgement is then used to evaluate the findings of the risk assessments and to provide recommendations for the project.

By convention, the geo-environmental and the geotechnical aspects are discussed in separate sections, but in instances where interaction is required to produce a holistic design, this is discussed at the end of the geotechnical recommendations section.

Remaining uncertainties and recommendations for further work are listed at the end of the report.

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2.0 PRELIMINARY INVESTIGATION (PHASE 1 STUDY)

A number of desk study sources have been used to assemble the following information, including a proprietary environmental data report which has been obtained for the site, Report Reference GS-3134185, dated 4th July 2016, and is presented in Appendix D.

2.1 Site Referencing

The site is referenced in Table 2.1.

Table 2.1: Site Referencing Information

Item Brief Description

Site name Land near Bradford Road, Corsham

Site location and grid The site is located off the Bradford Road and is located between Rudloe and Corsham in reference Wiltshire. The nearest postcode is SN13 9LA and the approximate National Grid Reference is 385 170E, 169 890N.

A site location plan and a site survey plan are provided in Appendix A as Drawing BDR–HYD–XX– D-001 and Drawings BDR–HYD–XX–D-002 respectively. The original site survey plan was compiled by Brunel Survey.

2.2 Site Description and Walk-Over Survey

A walk-over survey was undertaken on 6th July 2016 and the 27th July 2016 to visually assess potential hazards and receptors. A basic site description is presented in Table 2.2 and selected walk-over photographs are presented in Appendix B.

Table 2.2: Site Description

Item Brief Description

Site access Via the B3109 to the north west of the site.

Site area Approximately 9.36 ha and irregular in shape.

Elevation, topography Site slopes very gently toward the southwest. and any geomorphic features

Present land use Site land use comprises agricultural grassed fields. A southeast to northwest trending wall is shown to cross the central area of the site. This feature is understood to form a flight line reference for bats. A slight depression and service pit, See Figure 3 Appendix B, was located is the southern area of the site. Currently this feature is open and is a significant risk to site users and local fauna, suitable fall protection or capping/backfilling should be undertaken to mitigate this risk.

Vegetation One mature tree adjacent to the southern site boundary with sporadic mature trees along the north, south, east and west site boundaries.

General site sensitivity The Cotswolds Area of Outstanding Natural Beauty is located approximately 400m west of the site. Hedgerows are located along all site boundaries.

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Item Brief Description

Site boundaries and All site boundaries are marked by a mature hedge line. The B3109, Skynet Drive and Park surrounding land Lane roads are located beyond the hedge line on the northern, western and southern site boundaries. The compound and entrance to Hartham Park Underground Quarry is located to the east of the site boundary.

Evidence of quarrying No evidence at the surface of below ground quarry workings were observed on site. works However, a capped mine shaft was located approximately 70m west of the site. The desk study investigation identified a second air shaft feature approximately 70m southwest of the site, however it was not possible to locate this feature during the walkover survey. This feature was believed to be amongst densely vegetated shrubs.

2.3 Site History

A study of historical Ordnance Survey maps (Appendix C) has been undertaken to identify any former land uses at the site and surrounding areas which may have geotechnical or geo- environmental implications for the proposed development and is summarised in Table 2.3.

The site is not recorded as having any association with the Ministry of Defence (MoD), however it is bounded by land belonging to the MoD. Note that it is common for military sites not to be shown on Ordnance Survey maps. Sites of military or security significance may therefore not be picked up on in this review.

Table 2.3: Key Features from Historical Mapping

Map Edition Key Features on Site Key Features off Site and Scale

1886: Two buildings shown adjacent to the north Hudswell Quarry, railway and shafts shown 1:2,500 eastern site boundary. approximately 100m southeast of the site.

1901 No change Additional shafts and trial shafts located 1:10,560 approximately 60m northeast, 70m southwest and 100m south of the site.

1921: Small area of woodland shown over far south Hartham Underground Quarry complex 1:2,500 eastern area of the site. (including a slope shaft railway track) are shown adjacent to eastern site boundary. Air shaft shown beyond western site boundary. Development of residential houses surrounding the site.

1959: One building replaced by a pond feature. Further development of houses surrounding the 1:2,500 site. Above ground storage tank shown 140m northeast of the site.

1969: No change Hudswell Quarry no longer shown to be 1:2,500 present.

1988 – 1993: Remaining house feature and pond no longer Removal of above ground storage tank shown 1:2,500 shown. approximately 140m northeast of the site. Feature has been replaced by an electricity sub- station.

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2.4 Unexploded Ordnance/Bombs

In general accordance with CIRIA Report C681 (Stone et al 2009) non-specialist UXO screening exercise has been carried out for the site. The site shows no evidence of being used by the Ministry of Defence (MoD), however Royal Air Force (RAF) Rudloe Manor is located approximately 700m south west of the site. RAF Rudloe formed an Operations Block for western Great Britain during World War II. A review of the Unexploded Ordnance Survey (UXO) (Defence Equipment and Support (DE) Rudloe Phase I Explosive Ordnance Risk Assessments, ESG (Report reference 10/026 Dated March 2016) undertaken at Rudloe states that only a single German Air raid was carried out to the south west of Rudloe Manor during 1940. Additionally, a review of the Zetica regional bomb risk map for Avon shows the site to lie within a very low bomb risk area, therefore no further assessment of the site is required.

2.5 Geology

The general geology of the site area is shown on the 1:50,000 geological map of Bath (Sheet 265) and is summarised in Table 2.4.

Table 2.4: Geology

Location Age Stratigraphic Name Description On Site. Jurassic. Forest Marble Silicate-mudstone, greenish grey, variably calcareous and formation in the south notably sandy, with lenticular typically cross- bedded limestone units that form banks and channel-fills. A variety of limestone types occur, of which grey, weathering brown and flaggy, variably sandy medium to coarsely bioclastic grainstone or less commonly packstone predominates, especially at the base, which is increasingly ooidal north from Bath (Online BGS Geoindex). East of the site Jurassic. Cornbrash Formation Limestone, medium to fine grained, predominantly (forming the upper beds bioclastic wackestone and packstone with sporadic peloids; of the Forest Marble) generally and characteristically intensely bioturbated and consequently poorly bedded. Arenaceous units occur in places, particularly in the upper part. Generally bluish grey when fresh, but weathers to olive or yellowish brown. Thin argillaceous partings or interbeds of calcareous mudstone may occur.

The southwest – northeast trending Corsham fault is shown to traverse along the eastern site boundary. This fault forms a normal fault and the downthrown is shown to the southeast of the fault line.

The geological survey sheet for Bath shows the surrounding geology for the region to dip slightly towards the southeast.

No superficial deposits or areas of Made Ground are shown over or within the vicinity of the site.

2.6 Mining or Mineral Extraction

Land to the southwest of Corsham is known to be underlain by an extensive network of Bath Stone Quarries. Underground mining of Bath Stone commenced in 1844 and still occurs at the

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present day to a lesser extent. Part of the mines were converted to MoD facilities during and after World War II.

A Mining Risk Assessment of the site has been carried out by SLR, Report Ref 422.01918.00008 rev 1. The report identifies two mine air shafts located approximately 71m and 73m southwest of the site. An area of recorded shallow underground workings is shown to run parallel to Park Lane and is located immediately adjacent to the southern corner of the site. The SLR report indicates that this shallow mining feature is likely to be in the order of 20m below ground level.

An underground quarry plan for the area, shown on Drawing 17800, Basil Hill & Rudloe Sites, issued 16th October 2002, shows the southernmost air shaft to link to a complex of underground quarries to the south of the site. A copy of Drawing 17800 is presented in Appendix I. The Site Check Landmark Report, report number SAS_42268511_1_1 shows this air shaft to be associated with Hudswell Quarry.

The central shaft is shown to form an ‘air shaft’ and would therefore be expected to provide an air supply to underground mine working. A review of available information for the area does not show underground quarry workings to be present, however the Site Check Landmark Report No SAS_42268511_1_1 shows this air shaft to be associated with the Hudswell Quarry. It may be possible that un-surveyed underground quarries may be present in this location and potentially beneath the development site.

A site walkover, undertaken by Hydrock on 27th July 2016, identified central shaft features, See Figures 4 to 8 in Appendix B. The feature was shown to be capped with a concrete slab.

2.7 Ground Stability

The Groundsure Report No GS-3134185 highlights that ground stability hazards relating to compressible deposits, natural cavities, landslides, shrink / swell clays, collapsible soils and running sands are of low to negligible risk.

The SLR Mining Risk Assessment, Report No 422.01918.00008 re1, shows shallow underground quarrying features over the far southeast corner of the site. The report advises that no development work should take place over this corner of the site.

The Site Check Landmark Report No SAS_42268511_1_1 shows a backfilled pit / quarry approximately 70m southwest of the site.

2.8 Hydrogeology

The aquifer designations given in Table 2.5 are based on the Environment Agency interactive aquifer designation map.

Table 2.5: Hydraulic Characteristics of Strata

Stratum Aquifer Designation Hydraulic Characteristics

Forest Marble formation Secondary A aquifer Variable calcareous silicate Mudstone and limestone with fine grained lenticular cross beds and channel infills.

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Stratum Aquifer Designation Hydraulic Characteristics

Material weathered to an over-consolidated Clay with traces of silt and sand deposits Stratum is likely to be dominated by low permeability clay which is interbedded with limestone and moderate permeability layers of clayey sand. Overall, this unit is likely to be anisotropic in nature with horizontal permeability greater than vertical permeability.

Groundwater is anticipated to flow from northeast towards the southwest in line with the sites natural gradient. The Forest Marble formation is anticipated to form an aquiclude with poor permeability characteristics. Localised clayey sand lenses and limestone beds may form moderate permeability pathways for localised groundwater to migrate across the site. Reference to the Environment Agency web site shows the following groundwater bodies beneath the site and the current chemical status (Table 2.6).

The site is within a Zone 2 (Outer) groundwater Source Protection Zone (SPZ). There are no licensed groundwater or surface water abstractions within 1,000m of the site, however one water well is shown approximately 500m south of the site boundary on the BGS survey sheet for the area. Table 2.6: Groundwater Body

Category Label or Status

Waterbody ID GB49092G804800.

Waterbody name Bristol Triassic.

River basin district Severn.

Current quantitative quality Good.

Current chemical quality Poor.

Upward chemical trend Yes.

2015 predicted quantitative quality Good.

2015 predicted chemical quality Poor.

Overall risk At risk

Protected area Yes.

2.9 Hydrology and Flooding

The surface water features in the vicinity of the site are listed in Table 2.7 and, where appropriate, are marked on the Site Zonation Plan in Appendix A.

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Table 2.7: Surface Water Features

Feature Location Relative to Site

Unclassified waterbody 160m northeast of the site.

There are no licensed surface water abstractions within 1km of the site.

The desk study information indicates the proposed development is in Flood Zone 1 (with a low probability of flooding) and the area is greater than 1 ha so consultation with the Environment Agency is required with a Flood Risk Assessment (FRA).

A review of surface water flooding records from the Environment Agency website shows the northern area of the site to lie within a moderate and high flood risk area.

No further consideration of flood risk is undertaken in this report. Specialist flood risk advice should be sought with regards to drainage and flooding.

2.10 Waste Management and Hazardous Substances

The compound and entrance to Hartham Park Quarry is located immediately northeast of the site boundary. Industrial operating processes are anticipated to have taken place over this area.

The Site Check Landmark Report No SAS_42268511_1_1 shows no waste management sites recorded within 250m of the site.

There are no records relating to the storage of radioactive materials within 1km of the site.

There are no records of prosecutions relating to authorised processes in the vicinity of the site.

There is no Local Authority Pollution Prevention and Controls, COMAH sites, NIHHS sites, or Planning Hazardous Substance consents or enforcements within 500m of the site.

2.11 Natural Soil Chemistry

Information contained within the environmental data report (Appendix D) gives indicative natural concentration values (estimated) for the natural soils at the site for a selection of Contaminants of Potential Concern (CoPC). These have been reproduced in Table 2.8.

Table 2.8: Natural Soil Chemistry (mg/kg)

Element Arsenic Cadmium Chromium Lead Nickel

Concentration (mg/kg) 15 - 25 <1.8 90-120 <100 30-45

2.12 Radon

The radon risk has been assessed in the environmental data report which indicates that the site is not in a Radon Affected Area and no radon protection measures are required.

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2.13 BGS Borehole Archive

One borehole record is shown on the online BGS data resource and is located approximately 290m north of the site. The borehole record shows the following.

 ST8756/8a, drilled to a depth of 3.10m using a shell and auger drilling rig and shows Made ground from ground level to 1.30m underlain by the Forest Marble formation which comprises interbedded limestone and stiff sandy clays. No groundwater was encountered.

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3.0 PRELIMINARY CONCEPTUAL SITE MODEL

3.1 Physical Setting

The preliminary ground model of the site is the basis of the understanding of the ground conditions that will inform the geo-environmental exposure model and the geotechnical hazard assessment.

3.1.1 Location and Site History

The site is approximately 9.36ha in size and is located between Rudloe and Corsham in Wiltshire at approximate national grid reference 385 353, 170 047.

The earliest historical plans show the site to have formed an agricultural field from 1883 to the present day. Two buildings are shown over the north eastern area of the site from 1883 to 1988. A pond feature was shown on site from 1959 to 1988. A small area of woodland comprising mature trees and a pond is shown over the far south eastern corner of the site.

Surrounding features associated with the site include Hartham Underground Quarry entrance to the northeast of the site. Two air shaft features associated with Hudswell Quarry are shown approximately 70m west and southwest of the site.

Shallow (stone) mine workings are shown adjacent to the south eastern site boundary.

The site is predominately overlain by crops. A southeast to northwest orientated stone wall is located over the central area of the site and is understood to form a reference point for migrating bats.

A site walkover and review of a Groundsure Geo Insight and Landmark Site Check reports show no significantly potentially contaminated land uses within 250m of the site boundary.

3.1.2 Landscape and Topography

The site is shown to slope gently from the northeast towards the southwest

3.1.3 Geology

The model applying to the site generally is of a thin layer of Topsoil over residual soils to likely depths of less than 3.0m depth. This stratum is anticipated to be underlain by limestone or mudstone from the Forest Marble Formation.

Bedding of the structural geology is anticipated to be horizontal / sub – horizontal. A variation of ground conditions and reduction of the rock mass quality may be present in the area of the Corsham fault running parallel to the eastern site boundary. This faulted area is shown to traverse through the shallow underground quarry shown to underlie the far south eastern area of the site. There is the potential for the rock mass quality overlying the quarry roof to be poor.

Made Ground deposits are anticipated in the locality of the historic buildings and pond feature over the north eastern area of the site.

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3.1.4 Hydrology and Drainage

The site walkover did not identify any clear drainage features associated with the site. Pavement surface water drainage features are likely to be located on the roads adjacent to the northern, western and southern site boundary. Excess surface run off from the site is anticipated to primarily flow into these drainage features.

The Environment Agency online resource shows part of the northern area of the site to lie within a medium to high surface water flood risk area.

The nearest surface water feature to the site refers to an unclassified watercourse 180m northeast of the site. Surface water run-off is not anticipated to be able to migrate to this water course given the distance from site and the regional southwest sloping topography.

3.1.5 Hydrogeology

The Forest Marble formation is classified as a Secondary A Aquifer. Horizons of limestone within the formation are anticipated to have relatively high fracture flow permeability characteristics, whereas mudstone horizons are likely to form an aquiclude of low permeability. The solid geology adjacent to the Corsham Fault is likely to form an area of higher permeability based on the anticipated fractured nature of the bedrock in this area of the site. Perched groundwater may be present over mudstone beds and would be expected to either migrate towards the southwest in line with the sites natural gradient, or towards the southeast in line with the regional shallow dipping geology. Previous works undertaken by Hydrock in the local area have concluded that the main groundwater table below this area is likely to be located between 40m to 90m below ground level (bgl).

3.2 Geo-environmental Exposure Model

The preliminary exposure model is used for geo-environmental hazard identification and establishing potential contaminant linkages based on the contaminant-pathway-receptor approach.

3.2.1 Potential Contaminants

For the purpose of this assessment the potential contaminants have been separated according to whether they are likely to have originated from on-site or off-site sources.

Potential On-Site Sources of Contamination

 Pesticides and herbicides associated with previous agricultural land use;  Backfilled Pond feature where possible contaminants include elevated levels of metals and organics; and  Made Ground associated with historical buildings on site. Possible contaminates may include elevated levels of metals and organics.

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Potential Off-Site Sources of Contamination

With the exception of Hartham Park quarry, off-site sources of contamination listed in Table 2.3 have been reviewed and are not considered to pose a significant risk to the site. Hudswell quarry is not considered to pose a significant risk to the site given its distance and gradient from the site. It is not likely that contaminants from the above ground storage tank and electricity sub- station will migrate to site given their distance.

 Hartham Park quarry located to the northeast of the site. Contaminates associated with industrial land uses and may include metals, organics(polycyclic aromatic hydrocarbons [PAH] and petroleum hydrocarbons. However considering the depth to groundwater (the likely transport medium for contaminants onto the site) the risk from contaminants from Harthan Park Quarry is low. 3.2.2 Potential Receptors

The following potential receptors have been identified.

 Humans (neighbours, site end users).  Development end use (buildings, utilities and landscaping).  Existing and proposed flora.  Groundwater: Secondary A aquifer status of the Forest Marble formation.  Surface water drainage associated with roads adjacent to site. It should be noted that health and safety risks to site contractors and maintenance workers have not been assessed during these works and will need to be considered separately.

3.2.3 Potential Pathways

The following potential pathways have been identified.

 Humans: ingestion, skin contact, inhalation of dust and outdoor air.  Buildings: direct contact with substances deleterious to building materials.  Plant life: root uptake.  Underlying groundwater: migration of contaminant via leachate dispersion through the unsaturated zone in the Forest Marble formation Secondary A Aquifer.  Surface water: overland flow.  Surface water: base flow from groundwater. 3.3 Geotechnical Hazard Identification

Potential geotechnical hazards based on the expected ground conditions are listed below.

 Localised Uncontrolled Made Ground over the area of the historical buildings and reinstated ponds on site – excessive settlement or differential settlement of foundations and roads,  Low strength, compressible ground – excessive settlement of foundations and roads.

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 Attack of buried concrete by aggressive ground conditions – the development site may contain unknown Made Ground and potentially sulfate bearing soils.  Shrinkage/swelling of clay – settlement/heave of foundations when located within the influence of trees and vegetation.  Shallow underground quarry working in the far south eastern area of the site.  Unknown extent of underground quarry network associated with the central air shaft approximately 70m west of the site. 3.4 Unresolved Issues and Uncertainties

The Phase 1 investigation has highlighted a number of issues that require intrusive investigation and assessment to inform the design of the proposed development.

The extent of underground quarry workings associated with the central air shaft shown approximately 70m west of the site is not fully understood. This feature is identified as being associated with Hudswell Quarry to the southeast of the site. It is plausable that any below ground quarry workings associated with the shaft may traverse from the air shaft towards Hudswell quarry and not below the site, however it cannot be ruled out that the below surface quarry working may extend eastwards towards the site.

The main details of the site and potential hazards are summarised on Drawing HYD – XX – XX- D – G001 in (Appendix A).

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4.0 GROUND INVESTIGATION

4.1 Investigation Rationale

The ground investigation rationale based on the findings of the preliminary risk assessment is summarised in Table 4.1.

Table 4.1: Investigation Rationale

Exploratory Holes Purpose

TP01 – TP20 To provide an initial assessment of shallow ground conditions and collection of samples for geotechnical and geo-environmental characterisation. Square grid with100m spacing.

HP01 – HP02 To assess shallow ground conditions in areas with access constraints for plant including the small area of woodland in the southeast corner of the site and land in the vicinity of the historical buildings and pond feature in the north eastern area of the site. Positions were required to allow collection of geo-environmental samples.

TP01, TP12 and TP13 Trial pit locations undertaken to allow soil infiltration testing to be carried out to assess shallow ground conditions suitability for soakaway design.

DCP01 – DCP12 DCP – TRL probes undertaken to inform California Bearing Ratio (CBR) values for shallow soils across the site.

4.2 Site Works

The fieldwork took place between 6th July and 7th July 2016 and is summarised in Table 4.2. The position of site investigation locations (positioned using a hand-held GPS) are shown on the Ground Investigation Plan in Appendix E.

The logs, including details of ground conditions, soil sampling, in situ testing and any installations, are presented in Appendix E.

The weather conditions during the fieldwork and for the previous week were dry.

Table 4.2: Summary of Site Works

Max. or Activity Method No. Range In Situ Tests Notes (e.g. Installations) Depth (m)

Drilling, Pitting and Probing

Trial pits Machine (JCB 3X) 20 1.05 - 2.30 HSV Trial pits backfilled using arisings

Trial pits Hand-dug 2 0.40 Hand Pits backfilled using arisings

Probes TRL dynamic cone 11 0.80 CBR Derived values penetrometer

Other In Situ Testing or Monitoring

Infiltration Hydrock in-house 3 1.50 – 1.95 Soakaway testing In TP01, TP12 and TP13

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4.3 Geo-Environmental Testing

4.3.1 Sampling Strategy and Protocols

Investigatory hole locations were determined by reference to the conditions identified in the preliminary risk assessment. Certain specific features such as the historical buildings and pond feature were targeted for specific investigation. An approximate 100m grid methodology was used for the remainder of the site.

Samples were taken stored and transported in general accordance with BS 10175:2011+A1:2013.

4.3.2 Geo-environmental Laboratory Analyses

Wherever possible, UKAS accredited procedures have been used and the chemical test certificates are provided in Appendix H. The geo-environmental analyses undertaken on soils are summarised in Table 4.3.

Table 4.3: Summary of Sample Numbers for Geo-environmental Analyses of Soils or Other Solids

Weathered Determinand Suite Tospoil Forest Marble formation

Hydrock default suite of determinands for solids 7 1

Pesticides and Herbicide screening 3

The geo-environmental analyses undertaken on waters, leachates (eluates) or other liquids are summarised in Table 4.4.

Table 4.4: Summary of Sample Numbers for Geo-environmental Analyses of Waters, Soil Leachates or Other Liquids

Topsoil Soil Determinand Suite Leachates

Hydrock default suite of determinands for waters 3

4.4 Geotechnical Testing

4.4.1 Geotechnical Laboratory Testing

Wherever possible, UKAS accredited procedures have been used and the geotechnical test certificates are provided in Appendix F. The tests undertaken are summarised in Table 4.4.

Table 4.4: Summary of Sample Numbers for Geotechnical Tests

Weathered Test Forest Marble formation

Natural moisture content 6

Atterberg limit determination 6

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Weathered Test Forest Marble formation

Particle size distribution (sedimentation) 2

Sulfate and aggressive chemical environment classification for buried concrete classification (full 14 BRE SD1 suite)

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5.0 GROUND INVESTIGATION RECORDS AND DATA

5.1 Physical Ground Conditions

5.1.1 Summary of Strata Encountered

The following presents a summary of the properties of the ground and groundwater conditions encountered, based on field observations, interpretation of the field data and laboratory test results, taking into account excavation and sampling methods, transport, handling and specimen preparation.

All relevant data from the Hydrock investigation detailed in Section 4.0 GROUND INVESTIGATION are used from this point forward. Derived1 geotechnical parameters are also presented.

For the purposes of property designation, soils are divided into fine soils (clays and silts) and coarse soils (sands, gravels, cobbles and boulders) in accordance with BS 5930.

Soil plasticity class for fine soils is based on the classification system of BS 5930, adopting modified plasticity index values (based on percentage passing 425 μm sieve). Volume change potential of fine soils on change of moisture content has been assessed using guidance provided in NHBC Standards.

Equivalent approximate undrained shear strengths (cu) have been determined from in-situ shear vane testing which are supported by engineering descriptions of the materials encountered.

The ground conditions proven during the current investigation are in general accordance with the published geological literature and expectations from the desk study and previous investigation works. The upper Cornbrash beds of the Forest Marble Formation were however found to be more extensive than expected.

Details are provided in the logs in Appendix E, a summary is presented in Table 5.1 and the individual strata are described in the sections below.

Table 5.1: Strata Encountered

Depth to Top Depth to Base Thickness Stratum Brief Description (m bgl) (m bgl) (m)

Slightly gravelly, silty fine TOPSOIL. Topsoil Gravel is angular to sub-angular, fine to Ground level 0.20 – 0.30 0.20 – 0.30 medium limestone.

Black, slightly silty, gravelly SAND with Made Ground (trial pit traces of burn wood, clinker and Ground level 0.06 0.06 TP19) limestone.

1 Derived values of geotechnical parameters and/or coefficients are obtained from test results, by theory, correlation or empiricism in line with BS EN 1997-2:2007, Section 1.6.

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Depth to Top Depth to Base Thickness Stratum Brief Description (m bgl) (m bgl) (m)

Residually weathered Stratum comprises predominately clay Forest Marble (upper with interbedded sand, locally gravel Cornbrash bed) with horizons of destructured limestone, all of which are described as follows:

Firm to stiff, light orange brown, sandy, 0.85 – 1.80 fissured CLAY; 1.10 – 2.10 0.20 – 0.30 Locally locally >2.30m* Light orange brown, clayey, fine SAND; >2.30m*

Light cream, mottled brown, angular to sub-angular, fine to coarse very clayey, sandy GRAVEL.

Medium strong, light grey fractured Distinctly weathered 0.85 – 1.80 LIMESTONE with open and clay infilled Forest Marble (upper Locally Not proven Not proven discontinuities and possible karst Cornbrash bed) infilled features. >2.30m *

*Trial Pits 6 and 11 did not prove base of residual soils. Hard clay met at 2.3m in TP6, sands at 2.4m in TP11.

5.1.2 Topsoil

For the purposes of this report, topsoil is defined as the upper layer of an in situ soil profile, usually darker in colour and more fertile than the layer below (subsoil), and which is a product of natural chemical, physical, biological and environmental processes, but does not imply compliance with BS 3882:2015.

Topsoil was encountered across the entire site.

5.1.3 Made Ground

Made Ground was only encountered in TP19 and comprised of a black SAND with traces of burnt wood, clinker and limestone clasts from ground level to 0.06m bgl.

5.1.4 Residually weathered Forest Marble formation (upper Cornbrash beds)

Residually weathered soils were encountered beneath topsoil and mainly comprising firm and stiff, medium to high strength sandy clays with interbedded horizons of destructured limestone, sand and gravel. This variable interbedding was encountered in the majority of exploratory hole locations. The exceptions being trial pits TP13 and TP18 in the north eastern area of the site where limestone beds were encountered throughout.

In-situ hand vane testing of cohesive residually weathered materials measured undrained shear strength values of between 70kPa to 140kPa for the stratum which equated to a material of medium and high strength locally. Possible dissolution features were recorded in trial pits TP07,

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TP11, TP12, TP19 and TP20. These features generally comprised very soft, occasionally stiff, silt, clay or sand materials which were encountered below a layer of highly weathered limestone which varied in thickness from 0.10m to 0.40m. The very soft material underlying the layer of limestone was frequently observed to be too soft to undertake shear vane testing on. The thickness of the very soft material ranged from between 0.15m to greater than 0.80m.

Less weathered limestone material was encountered at the base of the very soft material in all trial pit locations listed above with the exception trial pit TP11. These softened features may form localised karsts which were formed by dissolution erosion of the limestone material via groundwater migration through fissures within the rock. These features have then subsequently been infilled with clays, silts and sand grains over time. These features were not encountered along the northern area of the site, however their distribution across the site appears to be random.

The majority of Atterberg tests undertaken show the plasticity index value for the material to range between 26% and 29%, which corresponds to a material of intermediate plasticity. One sample does show a higher plasticity index value of 43%, which corresponds to a material of high plasticity. A typical modified plasticity value of 23%, which equates to a medium volume change potential, can be determined for the material in line with guidance from NHCB 2014. A higher modified plasticity value of 43% can be determined for one sample which equates to a material of high volume change potential for the material.

Based on a plasticity index value of 29% for the stratum, an effective friction angle of 240 can be applied to the cohesive residually weathered soil in accordance with guidance provided in BS:8002: 2015. A summary plasticity characteristics of the residually weathered soils is presented in Table 5.2.

Table 5.2: Atterberg limits testing summary

Faction Modified Moisture Liquid Limit Plastic Limit Plasticity Volume change >0.425m plasticity index content (%) (%) (%) index (%) potential m (%)

17 – 31 31 – 61 12 - 26 19 - 43 81 - 100 23 - 43 Medium - high

The thickness of the weathering horizon typically varies from 0.20m to greater than 2.30m across the site. The weathering horizon was observed to be thickest in Trial Pit TP06 and TP11 towards the far western end of the site. The base of the weathered horizon was not proven in TP06 which was extended to 2.30m bgl. The weathering horizon was not shown to extend to beyond 2.1m bgl for the rest of the site.

5.1.5 Less Weathered Forest Marble Formation (Cornbrash Beds)

The recorded depth to less weathered rock varies from 0.80m to 1.85m over the majority of the site and locally to greater than 2.30m over central south western areas of the site.

Only the topmost horizon of this less weathered layer of the Cornbrash could be penetrated by the excavator but it can be generally described as Medium strong light grey LIMESTONE with both clay infill and open fractures

recovered as slightly clayey gravel and cobble (Class B partially weathered).

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Index strength testing of limestone arisings show the rock material to be of medium strong rock strength (25 – 50 MPa). It should be noted that the strength of the shallow rock mass is governed by any weaker layers that may lie beneath. Due to the nature of the investigation the presence or otherwise of deeper softened layers (such as those encountered above) could not be determined.

5.1.6 California Bearing Ratio (CBR)

The CBR results derived from insitu TRL DCP probing are summarised in Table 5.3 including recommended values that can be assumed for preliminary design purposes within the scope of this report.

Table 5.3: CBR Results and Derived Values

Stratum Method No. Tests CBR (%) (Range)

Residual weathered Forest In situ DCP probe 11 5 - 56 Marble

Residual weathered Forest From Plasticity relationship 6 2.5 – 3 Marble

5.1.7 Sulfate Content

In accordance with BRE (Special Digest 1), the Design Sulfate (DS) classification and the Aggressive Chemical Environment for Concrete (ACEC) classification are presented in Table 5.4. The assessment summary sheet is presented in Appendix F.

Table 5.4: Aggressive Chemical Environment Concrete Classification

Stratum No. Tests DS ACEC

Residually weathered soil and the distinctly weathered Forest 14 DS-1 AC-1 Marble

5.2 Groundwater

5.2.1 Groundwater Levels

No large inflows of groundwater were encountered during the ground investigation. However localised seepages and damp conditions were met upon in some locations below around 1m depth.

5.2.2 Infiltration Tests

The results of the infiltration testing undertaken are summarised in Table 5.5. The results sheets are presented in Appendix F. All testing was carried out in accordance with Hydrock’s 1-day assessment methodology. This is in general accordance with BRE Digest 365 (BRE 2007) where infiltration rates allow three test runs during a working day (or where there is no infiltration), but where low infiltration rates were encountered the available time may not have been sufficient to fully comply with the BRE test method.

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Where less than three tests were possible in a particular location the results provided should be considered indicative only and should not be used for design purposes. Further discussion concerning the suitability of infiltration testing at the site is provided in Section 8.8.

Table 5.5: Infiltration Test Results

Infiltration Rate (m/s) Stratum Trial Pit no. Depth Test 1 Test 2 Test 3

Residually and Insufficient Insufficient Insufficient partially weathered TP01 1.50 infiltration infiltration infiltration Forest Marble rate rate rate formation

Residually and partially weathered TP12 2.10 3.45 x 10-4 1.85 x 10-4 1.24 x 10-4 Forest Marble formation

Residually and Insufficient Insufficient Insufficient partially weathered TP14 1.55 infiltration infiltration infiltration Forest Marble rate rate rate formation

5.3 Geo-Environmental Results

The chemical test results for soil and leachates are given in Appendix H, which also includes summary tables of the data.

Concentrations of the following determinands were not reported above the laboratory limit of detection.

 Soils – Cyanide, Phenols, PAH.  Leachates – Cadmium, Cobalt, Chromium (VI), Antimony, selenium, tin, cyanide, bromate, chloride, Anthracene, Benzo(a)pyrene, Fluoranthene and Naphthalene. 5.4 Updated Ground Model

The preliminary conceptual site model initially developed from the desk study and walk-over survey has been updated using the findings of the ground investigation. The main features of the site are summarised on the Site Zonation Plan (Appendix A).

A seemingly localised area of the Made Ground was encountered in one trial pit location in the south eastern corner of the site and is considered to pose not significant risk to the site.

There is the potential for un-surveyed underground quarries to exists west of the site. It is not known whether any below ground quarries extend below the site. The presence of a capped air shaft, located approximately 70m west of the site, was verified during a Hydrock site walkover undertaken on the 27th July 2016.

The thickness of the weathering profile is shown to be variable across the site.

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Sub-surface possible karstic features, infilled with very soft clays, silts and sands were sporadically encountered across the site. No clear patterns in their distribution across the site are shown.

Evidence of clinker was observed in Trial Pit TP19.

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6.0 GEO-ENVIRONMENTAL ASSESSMENT

6.1 Approach

A number of generic risk assessments are undertaken in accordance with the principles of CLR 11 (Environment Agency 2004) using the CSM that has been updated following the ground investigation. Firstly, the risks associated with the identified potential contaminant linkages are estimated using standardised methods (typically involving comparison of site data with published ‘screening values’. Secondly, where screening values are exceeded, the risks are evaluated in an authoritative review of the findings with other pertinent information to determine if exceedance may be acceptable in the particular circumstances. For details please refer to Appendix H.

The data sets used comprise the appropriate analytical results obtained by Hydrock and listed in Section 4.3.

6.2 Updated Exposure Model

Following the site investigation, the plausible contaminant sources, receptors and pathways identified in Section 3.0 have been updated or confirmed as follows.

6.2.1 Sources

The following potential sources have been removed from the exposure model.

 Pesticides and herbicides associated with previous agricultural land use;  Backfilled Pond feature where possible contaminants include elevated levels of metals and organics; and  Made Ground associated with historical buildings on site. Possible contaminates may include elevated levels of metals and organics. 6.2.2 Receptors

No potential receptors have been removed from, or added to, the exposure model.

6.2.3 Pathways

The following pathways have been added to, the exposure model.

 Sub-surface infilled karstic features identified within the Forest Marble formation.

With reference to the updated ground model and updated exposure model reported above, generic risk assessment is undertaken in Section 6.0. Geotechnical recommendations made in Section 8.0.

6.3 Human Health Risk Assessment

This is a Tier 2 assessment using soil screening values for the CLEA land use scenarios for residential properties with plant uptake.

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The soil screening values used are generic assessment criteria (GAC) and results are given in Appendix H. Note that the Category 4 Screening Levels (C4SL) for lead have been used as there are no recognised GACs and the use of the term ‘GAC’ in this report includes these.

Statistical testing is used where data sets are suitable. For data sets with low sample numbers and/or a non-random spatial distribution (e.g. where sampling is targeted at specific areas) individual sample test results are compared directly with the screening values.

It should be noted that the phrase ‘further assessment required’ is used to denote soil concentrations that are equal to, or exceed, a GAC. This does not necessarily mean that the soil is ‘contaminated’ or not fit for use.

6.3.1 Risk Estimation (Without Statistical Testing)

Hydrock Default List of Determinands

The individual analytical results have been compared with the relevant GACs in the summary table in Appendix H. No substances exceed the GAC.

Asbestos

No traces of asbestos were encountered during the ground investigation.

Petroleum Hydrocarbons (PHC)

Analytical testing results show petroleum hydrocarbon concentrations to be below their detection limits.

6.3.2 Risk Evaluation

Soil contaminants are not considered to pose a significant risk to human health on site as no substances were recorded at concentrations above their GACs and no further assessment is therefore required as part of this report.

6.4 Plant Life Risk Assessment

6.4.1 Risk Estimation

Priority phytotoxic chemical concentrations have been screened against published values to determine the likely risk to plant growth and the findings presented in Appendix H. As with human health, statistical testing is used where data sets are suitable, otherwise individual sample test results are compared directly with the screening values.

Based on a US95 exceedance of the GAC, the pervasive chemicals of potential concern which require further assessment are summarised in Table 6.3.

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Table 6.3: Pervasive Chemicals of Potential Concern for Which Further Assessment is Required (Risk to Plants)

No. Generic Basis for Samples Chemical of No. Min. Max. US95 Criterion Generic Exceeding Potential Concern Samples (mg/kg) (mg/kg) (mg/kg) (mg/kg) Criterion Generic Criterion

Boron 3 8 1.4 5.9 4.93 2

Zinc 200 8 43 1300 894.84 1

6.4.2 Risk Evaluation

Within the topsoil, boron is slightly elevated when compared to the GAC. Detriment to plant life is hard to quantify and many of the GACs are based on agricultural crop yields rather than serious harm of death of a species. As the exceedance is slight and the vegetation on site did not show any signs of physical distress, Hydrock does not believe any additional consideration is required with regards to boron risks to plant life.

Hand pit location HP01, undertaken within the vicinity of the historical building and backfilled pond feature, identified a significantly elevated concentration of zinc when compared the to GAC for plant life health. Whilst detriment to plant life is hard to quantify as many of the GACs are based on agricultural crop yields rather than serious harm of death of a species, the significant exceedance of the GAC indicates that mitigation may be required and the recommended course of action is to obtain further advice from a landscape architect or to import a clean growing medium.

6.5 Pollution of Controlled Waters Risk Assessment

6.5.1 Risk Estimation

The risks to groundwater and surface water from contaminants on site have been assessed according to the Environment Agency (2006) Remedial Targets Methodology (RTM).

Under the European Water Framework Directive (2000/60/EC) pollutants from contaminated land sites are considered as passive inputs. Inputs to surface waters and inputs of non- hazardous pollutants to groundwater and are regulated under the Agency’s ‘limit’ pollution objective. As such, site contaminant loadings are compared with relevant threshold values (Water Quality Targets) which are linked to the conceptual site model. Acceptable WQT are defined for protection of human health (based on Drinking Water Standards (DWS)) and for protection of aquatic ecosystems (Environmental Quality Standards (EQS)).

For the purposes of this report, the site data are compared with the various targets as set out according to the Hydrock scenario in Table 6.4 (see Appendix H for details), on the basis of the following:

 there is the potential for leachates to migrate into the Forest Marble formation via fracture flow groundwater migration;  there is a low risk of leachate entering surface water drainage features located along the roads bounding the northern, western and southern site boundary via surface run-off;

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Table 6.4: Summary of Water Quality Risk Assessment Protocol

RTM Level Water Water Body Secondary Example Contaminant Linkages and Data Quality Receptors Receptors

Used Targets

Hydrock Hydrock Scenario

Contaminants from site leach or Human health seep into groundwater body and Groundwater. (abstraction). DWS this feeds surface water by base RTM Level 1 - D EQS flow. The surface water may be Soil leachate. Surface water. Aquatic (inland) used for human consumption and ecosystem. is an aquatic ecosystem.

Notes: Some EQS are water hardness dependent. This is measured either in the receiving water or in groundwater (if it is part of the pathway), or is estimated from national maps. Inland waters EQS applicable to freshwater, other waters EQS applicable to marine or transitional waters. Where both DWS and EQS are applicable, it is assumed that the EQS is for inland waters. This table and the results of the assessment are considered as a first screening for potential risks of pollution of Controlled Waters. More specific requirements may be stipulated by the relevant Agency.

The results of the Remedial Targets Methodology assessment are presented in Appendix and are summarised in Table 6.5.

There are no WQT’s for petroleum hydrocarbons in water. Consequently, Hydrock has calculated risk-based guidelines for drinking water based on a methodology proposed by the WHO and using the tolerable daily intakes for the various TPH fractions as used in the derivation of the soil GACs. No TPH or BTEX concentrations were detected in groundwater samples

It should be noted that in some instances the reporting limit (or detection limit) quoted by the laboratory may be greater than the WQT that it is being assessed against. As the current exercise is an initial screening assessment, further assessment of these elements has not been undertaken.

Table 6.5: Chemicals of Potential Concern for Which Further Assessment is Required (Controlled Waters)

Water No. Samples Chemical of Potential Quality Basis for Water No. Min. Max. Exceeding Concern Target Quality Target Samples (ug/l) (ug/l) Target (ug/l)

Soil Leachate

Aluminium 200 DWS 3 440 950 3

Iron 200 DWS 3 520 770 3

Ammonium 500 DWS 3 510 710 3

Note: the maximum recorded value is compared with the water quality target. * The Water Supply Regulations 1989 and the Private Water Supply Regulations 1991 both contained a prescribed concentration of 10 µg/l for “dissolved or emulsified hydrocarbons (after extraction with petroleum ether); mineral oils”. This was removed when these Regulations were updated in 2000 (consolidated 2007) and 2009, respectively. However 10 µg/l is used in this report as an initial screening assessment as it is frequently the preferred approach of the Environment Agency.

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6.5.2 Risk Evaluation

Whilst there are exceedances of the water quality targets, these are not considered to represent a significant risk of pollution of Controlled Waters as there is no evidence of artificial accumulations of these substances on the site and it is considered that they originate from the natural geology.

Furthermore, the inland waters EQSs for Leads and Zinc are based on the bioavailable fraction and because bioavailability has not been calculated for these metals the assessment is conservative as it is based on the assumption of 100% bioavailability.

Additionally, no groundwater was encountered during the ground investigation and ground investigations undertaken by Hydrock on adjacent sites indicate that the groundwater level for the general region is likely to be located between 40m to 90m bgl.

Soil infiltration testing undertaken within the cohesive material shows the material to have poor infiltration rates, suggesting that any contaminants are unlikely to be able to migrate into to the underlying groundwater.

6.6 Construction Materials Risk Assessment

6.6.1 Water Pipelines

The current guidance on selection of materials for potable water supply pipes to be laid in contaminated land is contained in a document published jointly by Water UK and the Home Builders Federation (Water UK HBF (2014)). The protocols in that document are for guidance and are not subject to enforcement by Water UK or any agency, but have been adopted by Water UK and by HBF as best practice for their members.

A formal water pipe risk assessment is beyond the scope of this report, however, the findings of this investigation have been compared to the threshold values in Water UK Table 1 as far as is practicable to give an indication of the possible restrictions to the use of plastic pipes for water supply to the site.

The site is greenfield and the investigation and assessment has indicated no exceedance of the threshold values. It is envisaged that standard pipework will be suitable for the site. However, this investigation was not designed specifically for water pipe runs and confirmation should be sought from the water supply company at the earliest opportunity.

6.6.2 Other Construction Materials

The implications for buried concrete are discussed in Section 8.9.

6.7 Findings of the Generic Risk Assessments

Analytical testing undertaken on soils during the ground investigation did not show contaminants to exceed their GACs for human health or plant life and no further assessment is therefore required.

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7.0 GEO-ENVIRONMENTAL CONCLUSIONS AND RECOMMENDATIONS

7.1 Key Risk Drivers

7.1.1 Human Health

Analytical testing undertaken on soils during the ground investigation did not show contaminants to exceed their GACs for human health and no further assessment is therefore required.

7.1.2 Plant Life

With the exception of Zinc, analytical testing undertaken on soils during the ground investigation did not show contaminants to significantly exceed their GACs for plant life. Detriment to plant life is hard to quantify and many of the GACs are based on agricultural crop yields rather than serious harm of death of a species. As the exceedance is slight and the vegetation on site did not show any signs of physical distress, Hydrock does not believe any additional consideration is required with regards to risks to plant life.

7.1.3 Controlled Waters

Leachate samples from three natural soil locations did not report concentrations of contaminants above the relevant GACs. Additionally, low infiltration rates and the absence of receptors within 500m of the site suggest the site is a low risk to controlled waters.

7.2 Mitigation Measures

No remedial measures are considered necessary at the site. 7.3 Waste Management

Any material excavated on site may be classified as waste and it is the responsibility of the holder of a material to form their own view on whether or not it is waste. This includes determining when waste that has been treated in some way can cease to be classed as waste for a particular purpose.

If material is to be removed from the site (e.g. foundation arisings) the laboratory test results in, Appendix H should be presented to the proposed receiving landfill site (to aid Waste Characterisation), prior to export, to confirm that it is suitably licensed to accept them. Some additional testing may be necessary at the time of disposal for the receiving landfill to confirm the Waste Acceptance Criteria (WAC) are acceptable for it to receive the waste.

Based on the results of the testing it is anticipated that the natural excavated soils will be classified as inert for off-site disposal purposes. However, this will depend on the results of the WAC testing. If the soils are not proven to be inert, they may be classified as non-hazardous.

Non-hazardous soils require pre-treatment prior to disposal. Effective pre-treatment, involving separation, sorting and screening can offer cost reductions through reducing the hazardous nature and volume of soil waste. Costs for disposal of non-hazardous/hazardous soils are significant compared to disposal of inert material.

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7.3.1 Waste Recommendations

Prior to disposal, the characteristics of any excavated soils will need classification in consultation with landfill sites and waste disposal contractors. Testing and analysis will be required to be carried out on the actual soil arisings which will constitute the waste.

7.3.2 Materials Management

Any material excavated on site may be classified as waste and it is the responsibility of the holder of a material to form their own view on whether or not it is waste. This includes determining when waste that has been treated in some way can cease to be classed as waste for a particular purpose.

If site-won material is to be re-used on site, a Materials Management Plan will be required, signed off by a Qualified Person as defined in the ‘Development Industry Code of Practice’ (CL:AIRE, March 2011).

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8.0 GEOTECHNICAL ASSESSMENT

8.1 Geotechnical Categorization of the Proposed Development

Eurocode 7, Section 2 advocates the use of geotechnical categorization of the proposed structures to establish the design requirements. For the purposes of this investigation, the proposed structures have been classed as Geotechnical Category 1.

The Geotechnical Category should be re-assessed at the design stage and a specific Geotechnical Design Report is required for Category 2 or 3 structures.

8.2 Groundwork

8.2.1 Site Preparation

The removal of Topsoil and localised Made Ground deposits within the footprint of buildings and pavements is recommended.

No buried man made obstructions were encountered during the ground investigation; however undetected buried foundations may be present within the area of the two historical buildings over the north eastern area of the site. Additionally, an open chamber with disused services at its base, See Figure 3, Appendix B was identified in the south eastern area of the site. It is recommended that this feature is excavated out and reinstated using a compacted granular fill.

All shallow horizons of limestone rock within the upper highly weathered zone were able to be excavated out using conventional plant. This was aided by the fact that these were often underlain by softer/looser material. The lower bed of less weathered limestone however, is likely to require the use of pneumatic breakers and/or excavator buckets equipped with rock ripping teeth to gain penetration.

8.2.2 Groundworks

Rock head levels are shown to vary across the site and difficult excavation conditions are likely to be encountered during excavations for foundations and service trenches. Therefore, an allowance for heavy plant and specialist breaking out equipment is recommended for the site.

The presence of soft infilled sub-surface karstic features may be present below the limestone bedrock. If encountered during groundworks then it is advised that these features are excavated out until competent limestone is proven. Although not found to be present during this investigation there is a possibility that some karstic features may not be naturally infilled. Should any voids be encountered these will need to be grouted up.

Instability of excavation faces was generally not observed during trial pitting. However random and sudden falls should be expected from the faces of near vertically sided excavations undertaken on site, particularly where water bearing sand deposits are encountered towards the south eastern area (TP20).

Temporary trench support, or battering of excavation sides, is likely to be required for all excavations that are to be left open for any length of time, and will definitely be required to

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permit man entry. Particular attention should be paid to excavation at, or close to, site boundaries/adjoining existing roads where collapse of excavation faces could have a disproportionate effect.

A risk assessment of the stability of any open excavation should be undertaken by a competent person and appropriate measures adopted to ensure safe working practise in and around open excavations. Further guidance on responsibilities and requirements for working near, and in, excavations can be obtained from the Construction Design and Management Regulations (2015).

Localised areas of perched groundwater over relatively impermeable horizons of clay may be present on site.

Any water pumped from excavations is likely to need to be passed via settlement tanks before being discharged to the sewer; discharge consents will also be required.

8.2.3 Earthworks/Reuse of Site-Won Materials

Spoil resulting from excavations within the natural soils should be suitable for re-use as general fill subject to further testing and specification.

An initial assessment has been completed on the potential to re-use site-won materials as an engineered fill material, which indicates the soils which are likely to be re-used can be classified as follows:

 Residually weathered soil - Class 2 cohesive (more than 15% passing the 63µm sieve) or Class 2 granular (less than 15% passing the 63µm sieve) - General Fill.  Distinctly weathered limestone – After processing: Class 2 granular (less than 15% passing the 63µm sieve) - General Fill. Where it is proposed to re-use site won materials as an engineered fill, it will be necessary to develop an appropriate Site Specific Earthworks Specification which can be adopted as part of the contract documentation. The basis for the Specification should be BS 6031:2009 and the latest version of the SHW, Series 600 Earthworks.

8.3 Mineworkings

8.3.1 Abandoned Mine workings and mine shafts

Findings from the investigation identified an air shaft feature to the west of the site which is not shown to link to previously surveyed quarry mine workings in the area. It is therefore considered possible that un-surveyed quarry mine workings may exist in the area and may potentially underlie the site. Further ground investigation works including open hole and rotary coring of the bedrock below the site is recommended in order to assess the potential for mining related subsidence to impact the site.

Finding from the SLR mining Risk Assessment Report Ref 422.019180.008 Rev1 shows quarry mine workings adjacent to the south eastern site boundary. The report suggests that working may be in the order of 20m bgl. A review of the BGS 1:50,000 scale plan shows the Corsham

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fault to pass through the working. Hydrock would recommend that the rock mass quality is investigated by drilling boreholes over this part of the site.

8.4 Possible karst features

Possible karstic features have been identified underlying the upper surface of limestone rock head. The presence of soft infill features underlying the upper horizon of limestone rock may cause the potential for excessive settlement or failure of the ground under load.

The presence of the soft fine grained infill features is likely to cause variable infiltration rates for the design of soakaways across the site.

It is recommended that further ground investigation works are undertaken to further determine the extent and nature of the infilled features across the site, particularly below the lower bedrock layer encountered.

8.5 Foundations

The presence of potential soft infilled karstic voids (and mines) below rock head across the site poses a significant risk to foundation design for the site and further investigation is recommended to this regard. The comments below regarding foundation design are provided as preliminary guidance based on a favourable outcome from further investigations. The recommendations in this report follow NHBC Standards Chapter 4.2 (2014).

The proposed site layout is understood to comprise 170, 2 to 3 storey residential properties across the site. Hydrock have not been provided with any information regarding anticipated line loads for the proposed structures.

Residually weathered soils are shown to be of a medium to high volume change potential.

Two areas of mature trees are noted in the southern area of the site. Sporadic tree cover is also noted along the northern, western, southern and eastern site boundaries. The trees are of an unknown size, species or maturity. Plots constructed within influencing distance of these trees (whether on- or off-site and whether to remain or be removed), should be constructed in accordance with NHBC Standards.

If trees are to be removed, the roots should be grubbed out and foundations extended to below the zone of disturbance created by this activity.

Due to the presence of softened ground below upper limestone beds, it is recommended that foundation excavations are advanced through the upper highly weathered zone and found on the top of the deeper less weathered limestone rock head. Where the lower rock-head lies deeper than 2.3m (TP6, TP11 &TP17) foundations may bear onto stiff clays provided it is proven that weaker materials do not lie below this depth.

The drilling of pilot holes below development plot footprints should be undertaken to identify the presence or otherwise of very soft material underlying the limestone. If identified within manageable depths, soft materials are to be excavated out and reinstated using compacted granular material or a concrete lean mix. Shallow foundations could be founded on limestone

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rock head if soft zones are not identified within a depth equivalent to 2.5 times the foundation footings width.

The allowable bearing pressure for foundations takes into consideration the risk of shear failure of the ground (ultimate limit state) and acceptable limits of settlement (serviceability limit state).

Foundations which span founding materials of different stiffness should have mesh reinforcement placed at the top and bottom.

The depth of foundations should be designed, and the formations inspected by an Engineer. Any sub-formation materials deemed as unsuitable such as soft or loose zones should be excavated and replaced with well compacted suitable granular fill or lean mix concrete.

Foundation excavations should be protected from water and inclement weather including frost and any water should be removed by pumping from a sump in the base of the excavation.

If further investigations prove unfavourable conditions below the lower limestone layer then either piled or raft foundations should be considered.

8.5.1 Strip or Trench Fill Foundations

Provided further investigation proves favourable conditions below the lower limestone layer; traditional strip or trench fill foundations are considered suitable for the proposed development. Hydrock recommend that the presence of shallow potential soft infilled features be determined for each residential plot prior to foundation construction.

Based on the rock characteristics discussed in earlier sections of this report, as a guide, an allowable net bearing capacity of 250kN/m2 should be available for trench fill foundation bearing at a minimum depth of 1.1m onto the rock. The use of light reinforcement mesh is recommended for all foundations.

The limestone rock is considered to be non-shrinkable, however a thick weathered horizon of medium volume change potential soils overlies the deeper rock layer in many instances across the site. Due regard should therefore be given to the guidance given in NHBC 2014 Chapter 4.2 on building near trees.

8.5.2 Heave Protection

Deepening of foundations in accordance with NHBC Standards in areas where rockhead lies beyond 2.3m depth will potentially be required where foundations are within the zone of influence of existing, removed or proposed trees and proposed shrub planting. For existing (and any known removed) trees this will require a tree survey to be undertaken by an arboriculturist in accordance with BS:5873:2012 which must include off-site trees that could have an effect on foundation design, in addition to trees on site. Where foundations are within the influence of trees and are deeper than 1.5m bgl, a suitable compressible material or void former will be required.

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Where foundations require deepening to greater than 2.5m below ground level, it is recommended that they be designed by an engineer, as specified in NHBC Technical Requirement R5.

Should piled foundations be required due to the presence of deep soft karstic features and/or mining influence; the upper section of the pile should be sleeved or overbored (to the recommended minimum founding depth) to allow for clay volume change if within the influence of trees.

8.6 Ground Floor Slabs

As clay soils are of medium to high volume change potential at the site, it is recommended that suspended floor slabs should be adopted, in accordance with NHBC Standards.

8.7 Roads and Pavements

Based on the test results, it is considered likely an equilibrium CBR of 3% will be achievable for the shallow fine soils and 5% for shallow limestone beds over the site and can be used for preliminary design, subject to in situ testing during construction.

Proof rolling of the formation level will be required and any loose or soft spots should be removed and replaced with an engineered fill, in accordance with a suitable Specification. The formation level will also need to be protected during inclement weather from deterioration; all slopes should be trimmed to falls to shed rain water and the surface sealed to limit infiltration.

Prior to the placement of the founding materials and the construction of the road pavement, the sub-formation and formation will need to be inspected and checked in accordance with a suitable specification to ensure the ground conditions are as expected. All testing should be carried out in accordance with British Standards to confirm that the ground conditions at time of construction are consistent with the previous design parameters.

8.8 Soakaways and Drainage

Indicative infiltration rates for the ground investigation are presented in Appendix F and are summarised in Table 8.2.

Table 8.2: Infiltration Testing Data

Recorded Indicative Infiltration Rate Stratum Comments Range (m/s) Average (m/s)

Soakaways were only observed to be BRE 365 Residually and compliant within the distinctly weathered 3.45 x 10-4 – 1.24 x 10-4 2.18 x 10-4 distinctly weathered Forest Marble limestone bands where formation fracture flow groundwater migration is dominant.

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Soakaway drainage is considered suitable for this site where chambers are sufficiently advanced into the limestone. However, the presence of infilled fine soils within the limestone bedrock is likely to provide less favourable infiltration rates in some areas.

Further testing is recommended once initial soakaway locations are established.

8.9 Buried Concrete

Based on guidelines provided in BRE Special Digest 1 (BRE 2005), the soils can be classified as Design Sulfate Class DS-1 and ACEC Class AC-1 (see Section 5.1.7.).

8.10 Interaction Between Geotechnical and Geo-Environmental Recommendations

Hydrock have not identified any geo-environmental constraints for the development site.

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9.0 UNCERTAINTIES AND LIMITATIONS

9.1 Site-Specific Comments

The extent of potential underground bath stone quarries to the west of the development site are not fully understood at this point of time. A site walkover undertaken on the 27th July identified a capped air shaft, located approximately 70m west of the site. However, a review of available surveyed underground quarries for the area does not show any features to be present.

It was not possible to identify a second air shaft, located approximately 70m southwest of the site, during the site walkover inspection. This was due to the likelihood that the second air shaft was located within an area of dense overgrown vegetation. This airshaft is shown to service an underground shallow quarry feature which is located within the vicinity of the sites far south western boundary. This feature has been surveyed in but is in close proximity to the site boundary.

Hydrock would recommend a down the hole survey of the shaft and potentially borehole investigations over the western area of the site to ensure that no below ground quarry features are present below the development site.

The presence of the possible infilled karstic features (or a possible weak weathered horizon within the limestone rock mass) is not fully understood at this time. These features pose a significant risk to the design of a shallow foundation solution for the site and for soakaway drainage.

Further ground investigation works are recommended to determine the nature and distribution of these features across the site. Borehole drilling in conjunction with a geo-physical investigation is recommended.

9.2 General Comments

Hydrock Consultants Limited (Hydrock) has prepared this report in accordance with the instructions of Redcliffe Homes Ltd (the Client), by email dated 17th May 2016 under the terms of appointment for Hydrock. Hydrock shall not be responsible for any use of the report or its contents for any purpose other than that for which it was prepared and provided. Should the Client require to pass copies of the report to other parties for information, the whole of the report should be so copied, but no professional liability or warranty shall be extended to other parties by Hydrock in this connection without the explicit written agreement thereto by Hydrock. The report may be assigned by the Client by way of absolute legal agreement to a purchaser of all or part of the site to which the report refers (“The Site”) without the consent of Hydrock being required and such assignment shall be effective upon written notice thereof being given to Hydrock. No further assignments shall be permitted, unless expressly agreed in writing by Hydrock. In the event of the Client entering into a legal joint venture to develop The Site, the report can be regarded as having been issued by Hydrock jointly in favour of the Client and the joint venture partner, and in respect of the report Hydrock would owe the joint venture partner the same duty of care that Hydrock owed to the Client when Hydrock was instructed to prepare the report subject to all the matters contained or referred to in the report.

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This report details the findings of work carried out in July 2016. The report has been prepared by Hydrock on the basis of available information obtained during the study period. Although every reasonable effort has been made to gather all relevant information, all potential environmental constraints or liabilities associated with the site may not have been revealed.

Hydrock has used reasonable skill, care and diligence in the design of the investigation of the site. The inherent variation of ground conditions allows only definition of the actual conditions at the locations and depths of trial pits and boreholes at the time of the investigation. At intermediate locations, conditions can only be inferred.

Groundwater findings described are only representative of the dates on which they were made and levels may vary.

Unless otherwise stated, the recommendations in this report assume that ground levels will remain as existing. If there is to be any re-profiling (e.g. to create development platforms or for flood alleviation) then the recommendations may not apply.

Information provided by third parties has been used in good faith and is taken at face value; however, Hydrock cannot guarantee its accuracy or completeness. It is assumed that previous reports provided have been assigned to the Client and can be relied upon. Should this not be the case Hydrock should be informed immediately as additional work may be required.

The work has been carried out in general accordance with recognised best practice. The various methodologies used are explained in Appendix G. Unless otherwise stated, no assessment has been made for the presence of radioactive substances or unexploded ordnance. Where the phrase ‘suitable for use’ is used in this report, it is in keeping with the terminology used in planning control and does not imply any specific warranty or guarantee offered by Hydrock.

The chemical analyses reported were scheduled for the purposes of risk assessment with respect to human health, plant life and controlled waters as discussed in the report. Whilst the results may be useful in applying the Hazardous Waste Assessment Methodology given in Environment Agency Technical Guidance WM3, they are not primarily intended for that purpose and additional analysis may be required should waste classification be required for consideration of off-site disposal of contaminated soils. Separate analyses will be required to meet the Waste Acceptance Criteria for specific landfill sites.

Unless otherwise stated, the chemical testing carried out for this report was not scoped to comply with the requirements of the water supply company and further work may be required.

The preliminary risk assessment process may identify potential risks to site demolition and redevelopment workers. However, consideration of occupational health and safety issues is beyond the scope of this report.

Please note that notwithstanding any site observations concerning the presence or otherwise of archaeological sites, asbestos-containing materials or invasive weeds such as Japanese knotweed, this report does not constitute a formal survey of these potential hazards.

Any site boundary line depicted on plans does not imply legal ownership of land.

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10.0 RECOMMENDATIONS FOR FURTHER WORK

The following further works will be required:

 further ground investigation works to determine the presence or otherwise of underground quarry features below the site and provide information on the origin and distribution of possible karstic features underlying the site;  discussions with service providers regarding the materials suitable for pipework etc.;  discussions with regulatory bodies regarding the conclusions of this report;  foundation depth in relation to trees assessment, following a tree survey to BS 5837:2012;  detailed design of foundations; and  inspection of foundations by a suitably qualified and experienced engineer prior to casting foundations.

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11.0 REFERENCES

ALLEN, D. L., BREWERTON, L. J., COLEBY, L. M., GIBBS, B. R., LEWIS, M. A., MACDONALD, A. M., WAGSTAFF, S. J. and WILLIAMS, A.T. 1997. The physical properties of major aquifers in England and Wales. British Geological Survey Technical Report WD/97/34. 312pp. Environment Agency R&D Publication 8.

ASSOCIATION OF GROUND INVESTIGATION SPECIALISTS. 2006. Guidelines for Good Practice in Site Investigation. Issue 2. AGS, Beckenham.

BRE. 1999. The influence of trees on house foundations in clay soils. BRE Digest 298. Building Research Establishment, Garston, 8pp.

BRE. 1991. Soakaways. BRE Digest 365. BRE, Garston.

BRE. 2005. Concrete in aggressive ground. BRE Special Digest 1, 3rd Edition. BRE, Garston.

BRITISH STANDARDS INSTITUTION. 1986. British Standard Code of practice for Foundations. BS 8004. BSI, London.

BRITISH STANDARDS INSTITUTION. 2003. Geotechnical investigation and testing - Identification and classification of rock - Part 1: Identification and description. BS EN ISO 14689-1 Incorporating Corrigendum No.1. BSI, London

BRITISH STANDARDS INSTITUTION. 2004. Eurocode 7 – Geotechnical design - Part 1: General rules. BS EN 1997-1. Incorporating Corrigendum No.1. BSI, London.

BRITISH STANDARDS INSTITUTION. 2007. Eurocode 7 – Geotechnical design - Part 2: Geotechnical investigation and testing. BS EN 1997-2. BSI, London.

BRITISH STANDARDS INSTITUTION. 2009. Code of practice for earthworks. BS 6031 Incorporating Corrigendum No.1:2010. BSI, London.

BRITISH STANDARDS INSTITUTION. 2011. Code of Practice for Investigation of Potentially Contaminated sites. BS 10175 Incorporating Amendment No.1:2013. BSI, London.

BRITISH STANDARDS INSTITUTION. 2012. Trees in relation to design, demolition and construction – Recommendations. BS 5837. BSI, London.

BRITISH STANDARDS INSTITUTION. 2015. Code of practice for ground investigations. BS 5930. BSI, London.

BRITISH STANDARDS INSTITUTION. 2015. Code of practice for earth retaining structures. BS 8002. BSI, London.

CIEH and CL:AIRE. May 2008. Guidance on comparing soil contamination data with a critical concentration. Chartered Institute of Environmental Health and Contaminated Land: Applications in Real Environments, London, 66pp.

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CONCRETE SOCIETY, THE. 2013. Concrete industrial ground floors. A guide to design and construction. Technical Report 34 (4th Ed.). The Concrete Society, Camberley. 88pp.

DEFRA. March 2014. SP1010: Development of Category 4 Screening Levels for Assessment of Land Affected by Contamination – Policy Companion Document. Defra, London.

ENVIRONMENT AGENCY. 2004. Model procedures for the management of land contamination. Contaminated Land Report 11. The Environment Agency.

ENVIRONMENT AGENCY. 2015. Waste classification. Guidance on the classification and assessment of waste (1st Ed.) Technical Guidance WM3. The Environment Agency.

HEALY, P.R. & HEAD, J.M. 1984. Construction over abandoned mine workings. CIRIA Special Publication SP32. CIRIA, London.

HIGHWAYS AGENCY. 2009. Design Guidance for Road Pavement Foundations (Draft HD25). Interim Advice Note 73/06. Rev 1. Highway Agency, London.

JONES, H. K., MORRIS, B. L., CHENEY, C. S., BREWERTON, L. J., MERRIN, P. D., LEWIS, M. A., MACDONALD, A. M., COLEBY, L. M., TALBOT, J. C., MCKENZIE, A. A., BIRD, M. J., CUNNINGHAM, J. and ROBINSON, V. K. 2000. The physical properties of minor aquifers in England and Wales. British Geological Survey Technical Report WD/00/04. 234pp. Environment Agency R&D Publication 68.

MILES, J. C. H., APPLETON, J. D., REES, D. M., GREEN, B. M. R., ADLAM. K. A. M. and MYRES. A. H. 2007. Indicative Atlas of Radon in England and Wales. Health Protection Agency and British Geological Survey. Report HPA-RPD-033.

NHBC. 2014. NHBC Standards, Part 1 Introduction and Technical Requirements. NHBC, Milton Keynes.

NHBC. 2014. NHBC Standards, Part 4 Foundations. NHBC, Milton Keynes.

STONE, K., MURRAY, A., COOKE, S., FORAN, J. and GOODERHAM, L. 2009. Unexploded ordnance (UXO), a guide to the construction industry. CIRIA Report C681. CIRIA, London. 141 pp.

WATER UK HBF. January 2014. Contaminated Land Assessment Guidance. Water UK and the Home Builders Federation. 12pp.

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