Conceptual Site Model Report for Stowey Quarry, Bishop Sutton, Near Bristol
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3 Millennium House, Boundary Bank, Kendal, Cumbria, LA9 5RR Telephone 01539 728581 [email protected] Company Reference: 6732792 Conceptual Site Model Report for Stowey Quarry, Bishop Sutton, near Bristol. Prepared by: Rob Harper BSc, MSc, FGS For: Larry Edmunds Document Reference: WEL-P43 Date of Report: 20th April 2011 DOCUMENT INFORMATION AND CONTROL SHEET Document Status and Approval Schedule Report No. Title Conceptual Site Model Report for Stowey Quarry, Bishop Sutton, WEL-P43 Near Bristol. Issue History Issue Status Prepared By: Position Signature Date 1 Final Rob Harper Director 20/04/2011 DISCLAIMER This report was completed by Watermill Environment Limited (WEL) on the basis of a defined programme and scope of works and terms and conditions agreed with the client. This report was compiled with all reasonable skill and care, bearing in mind the project objectives, the agreed scope of works, the prevailing site conditions, the budget, the degree of manpower and resources allocated to the project as agreed. WEL cannot accept responsibility to any parties whatsoever, following the issue of this report, for any matters arising which may be considered outwith the agreed scope of works. This report is issued solely to the client and WEL cannot accept any responsibility to any third parties to whom this report may be circulated, in part or in full, and any such parties rely on the contents at their own risk. Watermill Environment Limited Conceptual Site Model Report for Stowey Quarry CONTENTS 1 INTRODUCTION 1 1.1 Background 1 1.2 Scope of report 1 1.3 Information sources 1 2 SITE SETTING 3 2.1 Site location 3 2.2 Topography of site and local area 3 2.3 Water features 3 2.4 Geology 4 2.5 Hydrogeology 5 2.6 Rainfall 7 3 CONCEPTUAL SITE MODEL 8 3.1 Source 8 3.2 Pathways 9 3.3 Receptors 9 3.4 Qualitative risk assessment 9 4 RECOMMENDATIONS 11 4.1 Future site monitoring 11 4.2 Additional preparation work 11 C:\Users\Rob\Documents\CLIENTS\Oaktree Environmental\Stowey Quarry\Report\Stowey Quarry CSM FINAL (20-04-11).docx i Watermill Environment Limited Conceptual Site Model Report for Stowey Quarry TABLES Table 1 Geology Table 2 Groundwater levels Table 3 Rainfall Table 4 Leachate composition Table 5 CSM summary Table 6 Site monitoring FIGURES Figure 1 Site location Figure 2 Local water features Figure 3 Geological cross-section APPENDICES Appendix A Earth Science Partnership Figure 3: “Geological features” (May 2007) and borehole logs: RO1 and RO2 (April 2007). Appendix B Borehole logs contained in Appendices to M. J. Carter Associates “A Report of a Site Investigation to determine the Depth of Mineral Extraction and the Suitability of Materials for use in the Construction of Low Permeability Seals at Stowey Quarry” (November 1998). Appendix C GroundSure Enviro- and Geo-Insight Reports (ref. HMD-188-1014615 & 1014616). Appendix D Oaktree Environmental Ltd. Drawing No. 2055/126/10: “Cell construction schematic”, (January 2011). C:\Users\Rob\Documents\CLIENTS\Oaktree Environmental\Stowey Quarry\Report\Stowey Quarry CSM FINAL (20-04-11).docx ii Watermill Environment Limited Conceptual Site Model Report for Stowey Quarry 1 INTRODUCTION 1.1 Background 1.1.1 Watermill Environment Ltd. (WEL) was commissioned by Larry Edmunds to develop an initial Conceptual Site Model (CSM) to describe the hydrogeological conditions at Stowey Quarry, Bishop Sutton, near Bristol. 1.1.2 The site is a former limestone quarry and the subject of a planning application to Bath and North East Somerset (BANES) Council (ref.10/05199/MINW) to be redeveloped as a landfill for the disposal of Stable Non-Reactive Hazardous Waste (SNRHW), primarily comprising cement-bonded asbestos, and inert waste. 1.1.3 The concerns raised by Bristol Water in its consultation response to BANES dated 9th March 2011 are outlined as follows (paraphrased): The proximity of the site to Chew Valley Reservoir, some 2 km northwest of the site, which is used as a drinking water supply and is also a Special Protection Area (SPA) and Site of Special Scientific Interest (SSSI). The potential for contamination of springs and streams in the vicinity of the site that drain into the reservoir. Uncertainty over the groundwater regime (flow mechanism and direction) at the site. Uncertainty over landfill engineering, surface water control and pre-disposal waste treatment (sorting). 1.1.4 The purpose of this report is to address the above issues and qualitatively assess the potential risk posed by the proposed landfill to the surrounding water environment. A quantitative assessment of potential risk posed by the landfill to the local water environment will be undertaken as part of the subsequent application to the EA for an Environmental Permit. 1.2 Scope of report 1.2.1 The CSM contained in this report includes the following information: a) Collation of existing information relating to the landfill’s environmental setting, including topography, geology and water environment (surface water and groundwater). b) Development of an outline hydrogeological conceptual site model (CSM) to describe viable source-pathway-receptor linkages at the site. c) Presentation of the CSM, conclusions of the risk assessment and recommendations for future management of the site. 1.3 Information sources 1.3.1 The following information was used in the preparation of this report: C:\Users\Rob\Documents\CLIENTS\Oaktree Environmental\Stowey Quarry\Report\Stowey Quarry CSM FINAL (20-04-11).docx 1 Watermill Environment Limited Conceptual Site Model Report for Stowey Quarry i) M. J. Carter Associates: “A Report of a Site Investigation to determine the Depth of Mineral Extraction and the Suitability of Materials for use in the Construction of Low Permeability Seals at Stowey Quarry” (November 1998). ii) GroundSure Enviro- and Geo-Insight Reports (ref. HMD-188-1014615 & 1014616) iii) Oaktree Environmental Ltd. Drawing No. 2055/126/10: “Cell construction schematic”, (January 2011). iv) Earth Science Partnership (ESP) Figure 3: “Geological features” (May 2007) and borehole logs: RO1 and RO2 (April 2007). v) British Geological Survey (BGS) Map Sheet 280 (Wells), 1:50,000 scale, Solid and Drift. vi) Environment Agency H1 Technical Annex to Annex J: “Hydrogeological Risk Assessments for Landfills and the Derivation of Groundwater Control and Trigger Levels”, (October 2010). vii) www.environment-agency.gov.uk for guidance and local environmental information. viii) www.metoffice.gov.uk for long term rainfall data (1971-2000). ix) www.natureonthemap.org.uk for locations of environmentally sensitive areas in vicinity of the site. C:\Users\Rob\Documents\CLIENTS\Oaktree Environmental\Stowey Quarry\Report\Stowey Quarry CSM FINAL (20-04-11).docx 2 Watermill Environment Limited Conceptual Site Model Report for Stowey Quarry 2 SITE SETTING 2.1 Site location 2.1.1 The site is located some 0.85 km southeast of Bishop Sutton, centres on National Grid Reference (NGR) ST 599 587 and covers an area of approximately 7.9 Ha. 2.1.2 The location of the site is shown in Figure 1. 2.2 Topography of site and local area 2.2.1 The site is situated at the northern edge of Sutton Hill, a broad plateau which extends for some 3 km southeast of Bishop Sutton. 2.2.2 Ground level around the site lies approximately within 155 and 160 metres relative to Ordnance datum (mOD), although spoil mounds within the site reach around 165 mOD in places. 2.2.3 Land to the south, across the top of Sutton Hill, remains above 150 mOD for some 800 m before declining southwards into the valley of the River Cam. 2.2.4 Two gullies exist west and north of the site. To the north of the site, ground drops away into a gully beneath and east of Broad Wood before rising again to some 145 mOD some 400 m from the site. 2.2.5 Ground level declines northwestwards from 155 mOD to below 100 mOD within around 300 m of the site (an approximate gradient of 1:5). Further northwest, ground level continues to decline to around 55 mOD at Chew Valley Lake. 2.3 Water features 2.3.1 Surface water features in the vicinity of the site are shown in Figure 2. 2.3.2 A spring rises some 50 m west of the site at an elevation of some 150 mOD, giving rise to a stream called Barelegs Brake. 2.3.3 A spring rises on Sutton Hill some 80 m southeast of the site at some 162 mOD and flows northwestwards and then northeastwards along Stowey Road towards the eastern corner of the site. It is considered likely that this is the on-site ‘spring’ noted by Carter Associates in 1998. 2.3.4 Other springs occur north and northwest of the site at distances of 500-650 m and elevations of 110-140 mOD. 2.3.5 It is noted that there is no apparent spring line within the gully north of the site. Springs do exist at around 120 mOD some 900 m northeast of the site which may be supported by groundwater within Lias strata (although outside of the immediate catchment area of the site), one of which supports the Cinderlands Brake. 2.3.6 The Barelegs Brake flows generally northwards and is met by streams from the other springs until, some 1.5 km north of the site, it heads west for another 1 km to its entry into Chew C:\Users\Rob\Documents\CLIENTS\Oaktree Environmental\Stowey Quarry\Report\Stowey Quarry CSM FINAL (20-04-11).docx 3 Watermill Environment Limited Conceptual Site Model Report for Stowey Quarry Valley Lake some 2 km northwest of the site. 2.3.7 The northern part of the site contains waterlogged areas as shown in ESP Figure 3 (see Appendix A).