Billing Brook Road, Northampton Geo-Environmental Assessment May 2019 Waterman Infrastructure & Environment Limited 5th Floor, One Cornwall Street, Birmingham, B3 2DX www.watermangroup.com Client Name: Northampton Partnership Homes Document Reference: WIE15311-100-R-4-1-3-GeoEnv Project Number: WIE15311 Quality Assurance – Approval Status This document has been prepared and checked in accordance with Waterman Group’s IMS (BS EN ISO 9001: 2015, BS EN ISO 14001: 2015 and BS OHSAS 18001:2007) Issue Date Prepared by Checked by Approved by A02 May 2019 Ryan Panter Phil Edge Phil Edge Graduate Engineer Associate Director Associate Director Comments Comments Disclaimer This report has been prepared by Waterman Infrastructure & Environment Limited, with all reasonable skill, care and diligence within the terms of the Contract with the client, incorporation of our General Terms and Condition of Business and taking account of the resources devoted to us by agreement with the client. We disclaim any responsibility to the client and others in respect of any matters outside the scope of the above. This report is confidential to the client and we accept no responsibility of whatsoever nature to third parties to whom this report, or any part thereof, is made known. Any such party relies on the report at its own risk. Contents Executive Summary 1. Introduction ................................................................................................................................. 1 1.1 Objectives and Brief ......................................................................................................... 1 1.2 The Proposed Development ............................................................................................ 1 1.3 Site Location .................................................................................................................... 2 1.4 Site Description ................................................................................................................ 2 1.5 Limitations ........................................................................................................................ 2 2. Preliminary Environmental Risk Assessment ......................................................................... 3 2.1 Methodology ..................................................................................................................... 3 2.2 Site Reconnaissance ....................................................................................................... 3 2.3 Site History ....................................................................................................................... 4 2.4 Geology ............................................................................................................................ 4 2.5 Controlled Waters ............................................................................................................ 5 2.5.1 Surface Waters ................................................................................................................ 5 2.5.2 Flood Risk ........................................................................................................................ 6 2.5.3 Groundwater .................................................................................................................... 6 2.6 Ecological Systems .......................................................................................................... 6 2.7 Planning Applications ....................................................................................................... 6 2.8 Hazard Assessment and Preliminary Conceptual Model................................................. 6 3. Methodology ............................................................................................................................. 13 3.1 Design of Investigation ................................................................................................... 13 3.2 Quality Control ............................................................................................................... 13 3.3 Health and Safety........................................................................................................... 14 4. Fieldwork ................................................................................................................................... 15 4.1 Ground Investigation ...................................................................................................... 15 4.2 Soil Sampling ................................................................................................................. 15 4.3 Monitoring Wells ............................................................................................................. 15 4.4 Groundwater and Ground Gas Monitoring ..................................................................... 15 5. Results ....................................................................................................................................... 16 5.1 Ground Conditions ......................................................................................................... 16 5.2 Potential Sources of Contamination ............................................................................... 16 5.3 Chemical Analysis .......................................................................................................... 16 5.4 Groundwater Levels ....................................................................................................... 17 5.5 Permeability Testing....................................................................................................... 17 5.6 Ground Gas .................................................................................................................... 17 6. Geotechnical Testing ............................................................................................................... 18 Billing Brook Road, Northampton Contents WIE15311-100-R-4-1-3-GeoEnv 6.1 In-Situ Testing ................................................................................................................ 18 6.2 Permeability Testing....................................................................................................... 18 6.3 Laboratory Testing ......................................................................................................... 18 6.3.1 Natural Moisture Content and Plasticity Index ...............................................................18 6.3.2 pH Value and Water Soluble Sulphate (SD1 Suite) .......................................................19 6.4 Excavations, Trench Shoring & Dewatering .................................................................. 19 7. Quantitative Environmental Risk Assessment ...................................................................... 20 7.1 Regulatory Context ........................................................................................................ 20 7.2 Risk to Human Health .................................................................................................... 21 7.3 Risk to Controlled Waters .............................................................................................. 21 7.4 Risk to Water Supply Pipes ........................................................................................... 22 7.5 Risk to Construction Workers ........................................................................................ 22 7.6 Ground Gas .................................................................................................................... 22 8. Proposed Remedial Strategy ................................................................................................... 23 9. Geotechnical Assessment ....................................................................................................... 24 9.1 Proposed Development ................................................................................................. 24 9.2 Characteristic Values and Design Bearing Resistance ................................................. 24 9.2.1 Shallow Foundations ......................................................................................................25 9.2.2 Shrinkability / Volume Change Potential ........................................................................25 9.2.3 Design Class for Concrete .............................................................................................25 9.2.4 Pavement Design ...........................................................................................................25 9.2.5 Floor Slabs .....................................................................................................................26 9.2.6 Groundwater / Stability of Excavations ..........................................................................26 9.2.7 Infiltration Drainage ........................................................................................................26 9.2.8 General ..........................................................................................................................26 10. Conclusions .............................................................................................................................. 27 10.1 Environmental Assessment ........................................................................................... 27 10.2 Ground Gas ...................................................................................................................