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WARWICKSHIRE COUNTY COUNCIL A46 LINK ROAD (PHASE 1 STONELEIGH) FINHAM BROOK / WESTLEY BRIDGE GROUND INVESTIGATION REPORT Contract: 21662 Date: March 2017 Ian Farmer Associates (1998) Limited 1 Fairfield Court Seven Stars Industrial Estate Wheler Road, Coventry CV3 4LJ Tel: 024 7630 3422 A46 Link Road (Phase 1 Stoneleigh), Finham Brook / Westley Bridge GROUND INVESTIGATION REPORT Carried out at A46 LINK ROAD (PHASE 1 STONELEIGH) FINHAM BROOK / WESTLEY BRIDGE Prepared for WARWICKSHIRE COUNTY COUNCIL Shire Hall Market Place Warwick CV34 4RL Contract No: 21662 Date: March 2017 Issue Date Description / Revision Details Prepared Approved Distribution 01 31/03/17 First Issue PC PB PDF to WWC Ian Farmer Associates (1998) Limited 1 Fairfield Court, Seven Stars Industrial Estate Wheler Road, Coventry, CV3 4LJ Tel: 024 7630 3422 www.ianfarmer.co.uk A46 Link Road (Phase 1 Stoneleigh), Finham Brook / Westley Bridge EXECUTIVE SUMMARY On the instructions of Warwickshire County Council, an investigation was undertaken to determine ground conditions to enable foundation and road/hard standing design to be carried out, together with a geoenvironmental risk assessment. It is understood that the proposed development comprises the construction of a new retaining wall and abutments for the new bridge over the Finham Brook. The site is situated beside the Finham Brook where the Stoneleigh Road crosses it over the existing Westley Bridge, approximately 3.5km to the north-east of Kenilworth town centre and may be located by Landranger Grid Map Reference SP318737. Published geology indicates the site to be covered by superficial deposits of Alluvium, with First River Terrace Deposits also marked as present, underlain by the Kenilworth Sandstone Formation. Site work comprised the sinking of four cable percussive boreholes, one of which was extended by rotary coring, and one window sample borehole. Standpipes were installed in four of the boreholes and monitored for groundwater levels on return visits. Selected sampled were subjected to geotechnical laboratory analysis. Allowable bearing pressures have been assessed for shallow spread foundations, with 75kPa available in the Alluvium and 175kPa available in the River Terrace Deposits. The ground level drops by 2.0m between the northern and southern banks of the brook which is evident by the absence of alluvial deposits in BH3 and BH4 and therefore any shallow bridge foundation can be installed below the Made Ground and within the River Terrace Deposits at a minimum depth of 1.4mbgl, where an allowable bearing pressure of 50kPa can be assumed. Foundations greater than 2.0mbgl can be designed to a greater allowable bearing pressure of 165kPa. Deeper foundations would require a piled foundation which would gain support in end bearing from the sandstone with side adhesion from both the River Terrace Deposits and the underlying residual sands of the weathered Kenilworth Sandstone Formation. A Design Sulphate Class for the soils / rock may be taken as DS-1, with site conditions suggesting an ACEC class for the site of AC-1 would be appropriate None of the samples analysed exhibited contaminant concentrations which would be considered to represent any significant risk to human health or controlled waters and there was no significant evidence of contamination within the soils observed. The material represented by the samples tested would be classified as non-hazardous waste, should disposal of material to landfill be required. However, the material is fit for purpose for reuse on the site and this should be considered where possible prior to any offsite disposal. Contract No. 21662 A46 Link Road (Phase 1 Stoneleigh), Finham Brook / Westley Bridge CONTENTS EXECUTIVE SUMMARY 1.0 INTRODUCTION 3 2.0 SITE SETTING 4 2.1 Site Location 4 2.2 Site Description 4 2.3 Geological Setting 4 3.0 SITE WORK 6 4.0 LABORATORY TESTS 7 4.1 Geotechnical Testing 7 4.2 Chemical Testing 7 5.0 GROUND CONDITIONS ENCOUNTERED 8 5.1 Sequence 8 5.2 Made Ground 8 5.3 Alluvial Deposits 8 5.4 River Terrace Deposits 8 5.5 Kenilworth Formation 9 5.6 Groundwater 9 6.0 GEOTECHNICAL ASSESSMENT 10 6.1 Introduction 10 6.2 Assessment of Soil Condition 10 6.3 Made Ground 10 6.4 Alluvial Deposits 11 6.5 River Terrace Deposits 11 6.6 Kenilworth Sandstone Formation – Residual Deposits 12 6.7 Kenilworth Sandstone Formation – Rock 13 6.8 Proposed Scheme 14 6.9 Foundation Recommendations 14 6.10 Excavations 16 6.11 Chemical Attack on Buried Concrete 16 7.0 GEOENVIRONMENTAL RISK ASSESSMENT 18 7.1 Contaminated Land 18 7.2 Site History 18 7.3 Risk Assessment – Human Health 18 7.4 Risk Assessment - Controlled Waters 18 7.5 Risk Evaluation 19 7.6 Waste 19 8.0 MANAGEMENT OF CONTAMINATION 20 8.1 Remediation and Verification 20 8.2 Management of Unidentified Sources of Contamination 20 Contract No. 21662 Page 1 of 25 A46 Link Road (Phase 1 Stoneleigh), Finham Brook / Westley Bridge 8.3 Risk Management During Site Works 20 9.0 REFERENCES 22 APPENDIX 1 - DRAWINGS Figure A1.1 - Site Location Plan Figure A1.2 - Exploratory Hole Location Plan APPENDIX 2 - SITE WORK General Notes on Site Work ii/i-ii/iv - SPT Calibration Certificate - Cable Percussive & Rotary Borehole Records - Window Sample Borehole Records - Groundwater Monitoring APPENDIX 3 - GEOTECHNICAL TESTS General Notes on Geotechnical Tests iii/i-iii/i Test Report 21662/1 - Results of Geotechnical Tests – Soils Test Report 21662A/1 - Results of Geotechnical Tests – Rock Test Report 17-38977 - Results of Chemical Geotechnical Tests – Soils Test Report 17-41315 - Results of Chemical Geotechnical Tests – Rock APPENDIX 4 - GEOENVIRONMENTAL TESTS General Notes on Geoenvironmental Tests iv/i-iv/i Test Report 17-38938 - Results of Contamination Tests – Soils Waste Report 21662 - HazWasteOnlinetm Records APPENDIX 5 - DESIGN CONSIDERATIONS Geotechnical Design Considerations v/i-v/iii APPENDIX 6 - GEOENVIRONMENTAL ASSESSMENT General Notes on Chemical Contamination vi/i-vi/vi Contract No. 21662 Page 2 of 25 A46 Link Road (Phase 1 Stoneleigh), Finham Brook / Westley Bridge 1.0 INTRODUCTION 1.1 On the instructions of Warwickshire County Council, an investigation was undertaken to determine ground conditions to enable foundation and road/hard standing design to be carried out, together with a geoenvironmental risk assessment. 1.2 It is understood that the proposed development comprises the construction of a new retaining wall and abutments for the new bridge over the Finham Brook. 1.3 A preliminary investigation report (PIR) has not been commissioned as part of the scope of works, therefore the comments within this report are based solely on this intrusive phase of investigation. 1.4 It is recommended that a copy of this report be submitted to the relevant authorities to enable them to carry out their own site assessments and provide any comments. 1.5 This report has been prepared for the sole use of the Client for the purpose described and no extended duty of care to any third party is implied or offered. Third parties using any information contained within this report do so at their own risk. 1.6 The comments given in this report and the opinions expressed herein are based on the information received, the conditions encountered during site works, and on the results of tests made in the field and laboratory. However, there may be conditions prevailing at the site which have not been disclosed by the investigation and which have not been taken into account in the report. 1.7 The comments on groundwater conditions are based on observations made at the time the site work was carried out. It should be noted that groundwater levels vary owing to seasonal or other effects. Contract No. 21662 Page 3 of 25 A46 Link Road (Phase 1 Stoneleigh), Finham Brook / Westley Bridge 2.0 SITE SETTING 2.1 Site Location 2.1.1 The site is situated beside the Finham Brook where the Stoneleigh Road crosses it over the existing Westley Bridge, approximately 3.5km to the north-east of Kenilworth town centre and may be located by Landranger Grid Map Reference SP318737. 2.1.2 A site location plan is included in Appendix 1, Figure A1.1. 2.2 Site Description 2.2.1 The site is split over both sides of the Stoneleigh Road. 2.2.2 The area to the north-east of the Stoneleigh Road comprises land immediately adjacent to an approximately 75m long stretch of the NE-SW flowing Finham Brook. 2.2.3 The brook is immediately bounded by sparse woodland, with an arable field to the south-east and pasture to the north-west. 2.2.4 The site area sloped very gently south-west and also relatively sharply by a couple of metres to the brook, with the fields lying at an approximate elevation of 65m to 63mAOD. 2.2.5 The area to the south-west of the Stoneleigh Road comprises a single exploratory hole point lying within an enclosed paddock / yard. 2.2.6 The paddock / yard consists of an area of gravelled hardstanding along its northern edge, with a number of beehives towards the rear (W) of the site. The southern part of the site is a little higher in elevation and comprises a grassed paddock. A number of mature trees separate the two. 2.2.7 This site area was relatively flat and lay at an approximate elevation of 65mAOD. 2.2.8 An exploratory hole location plan is given in Appendix 1, Figure A1.2. 2.3 Geological Setting 2.3.1 Details of the geology underlying the site have been obtained from BGS Sheet 184, ref. 9.2. 2.3.2 The geological map indicates the site area adjacent to Finham Brook to be covered by superficial deposits of Alluvium, comprising ‘clay, silt and gravel’, with First River Terrace Deposits also marked as present, described as ‘sand and gravel’.