DESK STUDY GROUND INVESTIGATION & BASEMENT IMPACT ASSESSMENT REPORT FOR 19 CATHCART HILL ISLINGTON LONDON N19 5QW Report Title: Geotechnical Desk Study, Ground Investigation & Basement Impact Assessment for 19 Cathcart Hill, Islington, London, N19 5QW Report Status: Final v1.0 Job No: P1287J1275 Date: 23 February 2018 Quality Control: Previous Release Version Date Issued By Prepared by: JOMAS ASSOCIATES LTD For V DEMOSTHENOUS Prepared by Should you have any queries relating to this report, please contact Jomas Associates Ltd www.jomasassociates.com 0843 289 2187 [email protected] 19 Cathcart Hill, Islington, London, N19 5QW Geotechnical Desk Study, GIR and BIA Prepared by Jomas Associates Ltd P1287J1275 – February 2018 i On behalf of V Demosthenous CONTENTS Page EXECUTIVE SUMMARY .................................................................................................................. VI 1 INTRODUCTION ........................................................................................................................ 1 1.1 Terms of Reference .............................................................................................................................. 1 1.2 Proposed Development ........................................................................................................................ 1 1.3 Objectives ............................................................................................................................................ 1 1.4 Scope of Works .................................................................................................................................... 1 1.5 Scope of Basement Impact Assessment ................................................................................................ 2 1.6 Limitations ........................................................................................................................................... 2 2 SITE SETTING & HISTORICAL INFORMATION ................................................................ 4 2.1 Site Information ................................................................................................................................... 4 2.2 Walkover Survey ................................................................................................................................... 4 2.3 Historical Mapping Information ........................................................................................................... 5 2.4 Historical Industrial Sites ...................................................................................................................... 7 2.5 Previous Site Investigations .................................................................................................................. 7 2.6 Unexploded Ordnance.......................................................................................................................... 8 3 ENVIRONMENTAL SETTING .................................................................................................. 9 3.2 Solid and Drift Geology ......................................................................................................................... 9 3.3 British Geological Survey (BGS) Borehole Data ..................................................................................... 9 3.4 Hydrogeology & Hydrology .................................................................................................................. 9 3.5 Detailed River Network ...................................................................................................................... 11 3.6 Radon ................................................................................................................................................. 11 4 GEOLOGICAL HAZARDS ........................................................................................................ 13 5 HYDROLOGY AND FLOOD RISK ......................................................................................... 15 19 Cathcart Hill, Islington, London, N19 5QW Geotechnical Desk Study, GIR and BIA Prepared by Jomas Associates Ltd P1287J1275 – February 2018 i On behalf of V Demosthenous 5.1 Hydrology and Flood Risk ................................................................................................................... 15 5.2 Surface Water Flood Risk .................................................................................................................... 16 5.3 No Significant Increase in Impermeable Areas ................................................................................... 16 5.4 Hydrogeology ..................................................................................................................................... 16 5.5 Sequential and Exception Tests .......................................................................................................... 16 5.6 Flood Resilience ................................................................................................................................. 16 6 LAND CONTAMINATION ASSESSMENT ........................................................................... 18 6.1 Industrial and Statutory Consents ...................................................................................................... 18 6.2 Landfill and Made Ground .................................................................................................................. 18 6.3 Environmental Risk - Legislative Framework ...................................................................................... 19 6.4 Conceptual Site Model ....................................................................................................................... 20 6.5 Qualitative Risk Estimation ................................................................................................................ 20 6.6 Outcome of Risk Assessment .............................................................................................................. 23 6.7 List of Key Contaminants .................................................................................................................... 23 7 SCREENING AND SCOPING ASSESSMENT ........................................................................ 24 7.1 Screening Assessment ........................................................................................................................ 24 7.2 Scoping ............................................................................................................................................... 27 8 GROUND INVESTIGATION ................................................................................................... 28 8.1 Rationale for Ground Investigation .................................................................................................... 28 8.2 Scope of Ground Investigation ........................................................................................................... 28 8.3 Trial Pits to Expose Foundations ......................................................................................................... 29 8.4 Sampling Rationale............................................................................................................................. 29 8.5 Sampling Limitations .......................................................................................................................... 30 8.6 In-situ Geotechnical Testing ............................................................................................................... 30 8.7 Laboratory Analysis ............................................................................................................................ 30 19 Cathcart Hill, Islington, London, N19 5QW Geotechnical Desk Study, GIR and BIA Prepared by Jomas Associates Ltd P1287J1275 – February 2018 ii On behalf of V Demosthenous 9 GROUND CONDITIONS .......................................................................................................... 33 9.1 Soil ..................................................................................................................................................... 33 9.2 Hydrogeology ..................................................................................................................................... 33 9.3 Physical and Olfactory Evidence of Contamination ............................................................................. 33 10 RISK ASSESSMENT – ANALYTICAL FRAMEWORK .................................................... 34 10.1 Context and Objectives ...................................................................................................................... 34 10.2 Analytical Framework – Soils .............................................................................................................. 34 10.3 BRE ..................................................................................................................................................... 35 10.4 Site Specific Criteria ............................................................................................................................ 35 11 GENERIC QUANTITATIVE RISK ASSESSMENT ........................................................... 37 11.1 Screening of Soil Chemical Analysis Results – Human Health Risk Assessment ................................... 37 11.2 Asbestos in Soil .................................................................................................................................