ENVIRONMENTAL & GEOTECHNICAL ENGINEERING Ground Investigation Report www.hspconsulting.com T: 0870 600 6090 Bramcote Hills Primary C1869 School Bramcote Hills Primary School Moor Lane Beeston Nottingham NG9 3GE Ground Investigation Report HSP Consulting Engineers Ltd Lawrence House Meadowbank Way Eastwood Nottingham NG16 3SB www.hspconsulting.com Date: 28/02/2014 Quality Assurance *Checked in accordance with HSP’s IMS (BS EN ISO 9001:2008 and BS EN ISO 14001:2004) Author L.E.Jones B.Sc (Hons), FGS Checked A.Copestake B.Sc (Hons) FGS Approved H. Pratt B.Eng (Hons), C.Eng, F.Cons.E, M.I.C.E, MI Mgt. Report Ref No. C1869/GIR Revision - Status FINAL This document is available electronically please contact the author to obtain a copy. 1 Contents 1.0 Executive Summary .................................................................................................... 3 2.0 Introduction ................................................................................................................. 5 3.0 Review of Existing Information .................................................................................... 6 4.0 Overview of British Legislation .................................................................................... 7 5.0 Intrusive Survey Limitations ........................................................................................ 8 6.0 Factual Report ............................................................................................................ 9 6.1 Fieldwork Procedure ................................................................................................ 9 6.2 In-Situ Testing ......................................................................................................... 9 6.3 Laboratory Testing ................................................................................................... 9 6.4 General Geology and Revealed Strata ...................................................................10 6.5 Groundwater ...........................................................................................................11 7.0 Geotechnical Interpretative Report ............................................................................12 7.1 Detailed Ground Model ...........................................................................................12 7.2 Cut and Fill .............................................................................................................12 7.3 Excavations ............................................................................................................13 7.4 Foundations ............................................................................................................13 7.5 Concrete Classification ...........................................................................................14 8.0 Environmental Interpretative Report ..........................................................................15 8.1 Sample Descriptions ...............................................................................................15 8.2 Chemical Investigation ...........................................................................................15 8.3 Metals and Inorganic Chemical Analysis and Asbestos Screen .............................16 8.4 Petroleum Hydrocarbon Analysis ...........................................................................16 8.5 Polycyclic Aromatic Hydrocarbons .........................................................................17 8.6 Water Supply ..........................................................................................................17 8.7 Human Health Mitigation ........................................................................................18 8.8 Ground Gas Risk Assessment................................................................................18 9.0 Engineers Conclusions and Risk Mitigation ...............................................................19 10.0 Appendices .............................................................................................................21 2 1.0 Executive Summary 1.0.1 HSP Consulting was commissioned by GF Tomlinson Ltd on behalf of Nottinghamshire County Council to undertake an intrusive ground investigation upon the area of land currently occupied by the existing Bramcote Hills Primary School, Moor Lane, Beeston, Nottingham, NG9 3GE (approximate National Grid Reference E450640, N338400. 1.0.2 Development plans for the site indicate a single storey system built extension to the existing Foundation Stage building which will include toilets and a kitchen area and a single storey system built unit to the northern section of the school site which will form additional teaching accommodation. 1.0.3 The physical methods of investigation employed were 8 No. Window Sample Boreholes (WS1 to WS8) to a maximum depth of 2.00m below existing ground level (begl) and a Foundation Pit to expose the foundation of the existing structure. 1.0.4 The exploratory holes revealed a downward strata succession comprising topsoil and paving slabs with sub base materials to a maximum depth of 0.25m begl. An area of Made Ground was observed within WS1 and WS2 to a maximum depth of 1.00m begl. Natural granular deposits comprising the weathered Nottingham Castle Sandstone Formation were encountered from a minimum depth of 0.05m begl and graded into competent sandstone from 0.80m begl. 1.0.5 For the proposed single storey extension the Made Ground encountered within WS1 and WS2 is not considered to comprise a suitable founding stratum. Therefore, trench fill foundations with a maximum allowable bearing capacity of 150kN/m2 can be assumed for design calculations where the foundations are being taken down to bear on the natural granular deposits of at least medium dense consistency at approximately 1.20m begl. Due to the nature of the development and ground conditions encountered it would be prudent to adopt a similar foundation solution to that of the existing building to avoid undermining the foundations of the existing structure and long term issues with differential settlement. It is recommended that the foundation and engineered fill perimeter in the footprint of the extension is exposed at the earliest opportunity to establish the existing construction along the elevation and confirm the foundation recommendations above are appropriate. 1.0.6 For the proposed single storey classroom unit trench fill foundations with a maximum allowable bearing capacity of 200kN/m2 can be assumed for design calculations where the foundations are being taken down to bear on the natural granular deposits of at least medium dense consistency at approximately 1.00m begl. This value incorporates a factor of safety of 3 and total settlements calculated are not expected 3 to exceed approximately 25mm, thereby keeping differential settlements within acceptable limits. Should higher loadings be required a member of HSP’s team should be consulted. 1.0.7 Groundwater entries were not encountered within the boreholes during the drilling process. Shallow groundwater entries may be encountered during earthworks operations. However, traditional sump and pump dewatering should be sufficient within all excavations at the site if required. 1.0.8 It is considered appropriate to adopt a basic Design Sulphate Class of DS-1 together with an Aggressive Chemical Environment for Concrete (ACEC) of AC-1 when considering the concrete classification. 1.0.9 Analysis of the chemical testing undertaken on samples retrieved from the site has suggested that remedial measures should not be required. The approval of the Local Environmental Health Officer should be sought with respect to the contaminated land assessment of the site. 1.0.10 Gas and groundwater monitoring has not been commissioned as part of this assessment. At this stage gas monitoring is not considered to be required as we understand that the proposed single storey system built unit(s) are elevated above ground level on brick plinths or legs which leaves a clear void beneath. Confirmation from the Client’s chosen contractor regarding void cladding materials and ventilation is recommended. 1.0.11 Should a traditional structure be proposed at the site it would be prudent to undertake gas monitoring in order to obtain an indication of the ground gas regime at the site and allow recommendations for gas protection measures to be incorporated within any design. 1.0.12 The executive summary contains an overview of key findings and conclusions. However, no reliance should be placed on the executive summary until the whole of the report has been read. Other sections of the report may contain information which puts into context the findings noted within the executive summary. 1.0.13 If development proposals or boundary lines change, the client should contact HSP Consulting Engineers Ltd to ensure that these changes do not present a necessity for further work or further consideration of the findings of this report. 4 2.0 Introduction 2.0.1 HSP Consulting was instructed by GF Tomlinson Ltd on behalf of Nottinghamshire County Council to carry out an intrusive geotechnical and environmental investigation of the site. Development plans for the site indicate a single storey system built extension to the existing Foundation Stage building which will include toilets and a kitchen area and a single storey system built unit to the northern section of the school site which will form additional teaching accommodation. 2.0.2 This