Site Investigation 53 Duncan Terrace Islington, London
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SITE INVESTIGATION 53 DUNCAN TERRACE ISLINGTON, LONDON Prepared for: Olivier and Neary Pollak ASL Report No. 346-15-088-09 March 2016 ASL Holly Farm Business Park Honiley Warwickshire CV8 1NP T: +44(0)1926485508 F: +44(0)1926485507 E: [email protected] W: www.aslenvironmental.co.uk SITE INVESTIGATION 53 DUNCAN TERRACE ISLINGTON, LONDON 1 INTRODUCTION ............................................................................................. 4 2 THE SITE........................................................................................................ 5 3 GEOLOGY ....................................................................................................... 6 4 HYDROGEOLOGY ............................................................................................ 6 5 HYDROLOGY .................................................................................................. 7 6 SITE HISTORY ............................................................................................... 8 7 ENVIRONMENTAL DATABASE SEARCH ......................................................... 10 7.1 Database Search Results .............................................................................. 10 7.2 Environmental Database Search Results ......................................................... 10 7.3 Geological Hazards ...................................................................................... 10 7.4 Contemporary Trade References ................................................................... 11 8 ASSESSMENT OF POTENTIAL CONTAMINATION RISKS ................................ 12 8.1 General ...................................................................................................... 12 8.2 On-Site Sources of Contamination ................................................................. 12 8.3 Off-Site Sources of Contamination ................................................................. 12 8.4 Receptors ................................................................................................... 12 8.5 Pathways ................................................................................................... 13 8.6 Conceptual Site Model ................................................................................. 13 8.7 Summary ................................................................................................... 14 9 GROUND INVESTIGATION AND TESTING ..................................................... 15 9.1 Ground Investigation ................................................................................... 15 9.2 Gas and Groundwater Monitoring Programme ................................................. 15 9.3 Laboratory Testing ...................................................................................... 15 9.4 Geotechnical Laboratory Testing ................................................................... 16 10 GROUND, GROUNDWATER AND GAS CONDITIONS ................................... 17 10.1 Materials Encountered ................................................................................. 17 10.2 Groundwater .............................................................................................. 18 10.3 Gas ........................................................................................................... 18 11 GEOTECHNICAL ASSESSMENT .................................................................. 19 11.1 General ...................................................................................................... 19 11.2 Basement Construction ................................................................................ 19 11.3 Floor Slabs ................................................................................................. 20 11.4 Excavations ................................................................................................ 20 11.5 Dewatering ................................................................................................. 20 11.6 Buried Concrete Classification ....................................................................... 21 11.7 Gas Protection Measures .............................................................................. 21 11.8 Existing Foundations .................................................................................... 21 12 CONTAMINATION ASSESSMENT – HUMAN HEALTH .................................. 22 12.1 Introduction ............................................................................................... 22 ASL Report No. 054-15-055-09 Page 2 of 32 March 2016 12.2 Chemical Test Results - Soils ........................................................................ 22 12.3 Discussion .................................................................................................. 23 13 CONTAMINATION ASSESSMENT – CONTROLLED WATERS ........................ 25 13.1 Introduction ............................................................................................... 25 13.2 Summary of Results - Soils .......................................................................... 25 13.3 Discussion .................................................................................................. 25 14 WASTE DISPOSAL .................................................................................... 27 15 DISCOVERY STRATEGY ............................................................................. 28 16 CONCLUSIONS AND RECOMMENDATIONS ................................................ 29 REFERENCES ...................................................................................................... 31 GENERAL NOTES ................................................................................................. 32 TABLES 1 Summary of Site History 2 Summary of Pollutant Linkages 3 Summary of Strata Encountered 4 Summary of Data with Respect to Human Health (Tier 1) 5 Summary of Soils Data with Respect to Controlled Waters (Tier 1) FIGURES 1 Site Location Plan 2 Site Layout Plan 3 Conceptual Model APPENDICES I Proposed Development Plan II Environmental Database Search Results III Historical Map Extracts IV Field Records V Chemical Laboratory Test Results VI Geotechnical Laboratory Test Data VII Qualitative Risk Assessment ASL Report No. 054-15-055-09 Page 3 of 32 March 2016 SITE INVESTIGATION 53 DUNCAN TERRACE ISLINGTON, LONDON 1 INTRODUCTION In January 2016, ASL were instructed by Engineers HRW Limited on the behalf of the clients Olivier and Neary Pollak to undertake the necessary site investigation and consultancy services associated with the site known as 53 Duncan Terrace, Islington, London. A site investigation is required in order to determine the ground conditions at the site ahead of its proposed development. It is understood that the proposed development comprises the construction of a new basement within the rear garden of the existing residential dwelling. A proposed development layout is presented as Appendix I. The scope of works for this project was set out in ASL’s proposal references 346-15- 088.elo.1692 dated 22nd December 2015. The proposal was formerly accepted by Engineers HRW Limited acting on the behalf of the clients Olivier and Neary Pollak their email dated 27th January 2016. This report presents a desk study, the development of a conceptual site model, the factual results from an intrusive investigation and subsequent laboratory analyses and interpretative comment in terms of the geotechnical properties of the ground conditions encountered at the site in relation to the proposed development together with an assessment of the contaminative status of the site. This report has been prepared for the sole benefit of the Clients, Olivier and Neary Pollak and their representatives and agents. The report has been written based on the results of data searches and ground conditions encountered at the time of the investigation and the results of subsequent analyses. Future changes in legislation and advances in current best practises or provision of more detailed design proposals will result in this report requiring review and possible further assessment after the date of issue. The general notes section within this report should be noted in relation to the limitations of this investigation and assessment. ASL Report No. 054-15-055-09 Page 4 of 32 March 2016 2 THE SITE The site is located to the north-west of Duncan Terrace and Colebrooke Row roadway and the north-east of Charlton Place roadway approximately 3.5km north-east of London city centre and can be located approximately by National Grid Reference TQ 317 834 shown on Figure 1. The site comprises an approximately rectangular shaped piece of land with the long axis aligned approximately north-west to south-east with maximum dimensions of approximately 22m by 6m. The site is occupied by the residential property 53 Duncan Terrace, a four and half story brick built residential dwelling with a sloping tiled roof. The site fronts on to Duncan Terrace. The frontage of the site comprises paving slabs with an area of managed soft landscaping and three mature trees beyond. A managed garden area is located to the rear of the property and comprises a lawned area centrally, raised flower beds in the north-west and a patio comprising paving slabs in the south-east. The garden area is bound to the south-west, north-west and north-east by a brick walls approximately 2m in height. The patio area is topographically lower than the lawn area with a change in elevation of