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SECTION 5 SITE INVESTIGATION SECTION 5 SITE INVESTIGATION 5 SITE INVESTIGATION 5.1 Rationale for Site Investigation and Specific Objectives 5.1.1 The site investigation has been undertaken in accordance with CLR11, Part 2A of the EPA 1990 and associated statutory guidance, incorporating a desk study followed by an intrusive investigation. Further targeted investigation and remedial options appraisal would be dependent on the findings of this site investigation. 5.1.2 The site investigation has been designed to test the validity of the CSM and all the potential pollutant linkages previously identified in Table 4.2. The key drivers for the site being: The risk to human health (dog walkers and other users); The risk to controlled waters beneath the site; and The risk to controlled surface waters surrounding the site. 5.1.3 The investigation will, therefore, focus on collecting data on the following: Quality and nature of Made Ground and landfilled material; Quality of natural ground within the site boundaries; Presence of anthropogenic soil gas; Perched water within / beneath the site; Leachability of contaminants into the underlying hydrogeology; and Quality of groundwater in the Minor Aquifer beneath the site. 5.1.4 Our soil sampling rationale for the site investigation has been developed with reference to the EA guidance ‘Secondary Model Procedure for the Development of Appropriate Soil Sampling Strategies for Land Contamination’ (Technical Report P5066/TR). 5.2 Methods of Site Investigation 5.2.1 The site investigation was undertaken between the 7 July and 25 July 2008, under the full time supervision of a PB Engineer. The scope of the works are detailed within Table 5.1, below; Combined Phase I and Phase II Investigation HPE98123A January 2009 Prepared by PB for Devon County Council Page 40 SECTION 5 SITE INVESTIGATION Table 5.1: Scope of Site Investigation Works Rationale Excavation of 10 No. deep boreholes to a maximum depth 20 mBGL across the site. Due to historic landfill activities known to operate on the site, it is possible that elevated concentrations of contaminants are present within the shallow capped material, within the landfill material and in deep soils beneath the land filled material. Collection and analysis of three soil samples from each borehole. Leachability analysis carried out on landfill material where visual and/or olfactory evidence of contamination was detected. The excavation of deep boreholes to assess potential risks to site users arising from potentially elevated concentrations of contaminants in the soil and determine any potential contamination migration trend. Four of the boreholes located out side of the landfill site in order to determine the nature of the geology and the depth to the solid geology beneath the site. These boreholes also help to determine the depth of groundwater. Shallow surface sample within the Capping Material (<1.0 mBGL) and additional samples taken at depths where there is visual or olfactory evidence of contamination to assess risks arising from all potential exposure scenarios in this environment. The analysis of leachate and eluate to assess if there is a source in unsaturated ground that may pose a risk to groundwater at the site. Excavation of 4 No. window sample boreholes to a maximum depth 5 mBGL under the entrance road to the main part of the landfill site. Collection and analysis of two soil samples from each borehole. The targeted collection of soil samples from under the road to assess any risks posed by material understood to have been disposed of at the site. The analysis of leachate and eluate to assess if there is a source in unsaturated ground that may pose a risk to groundwater at the site. Leachability analysis carried out on landfill material where visual and/or olfactory evidence of contamination was detected. Excavation of 30 No. trial pits to a maximum depth 5 mBGL across the site. Collection and analysis of three soil samples from each trial pit. Leachability analysis carried out on landfill material where visual and/or olfactory evidence of contamination was detected. The excavation of a series of shallow trial pits enable PB to determine the shallow ground conditions at the site including the composition of the fill material, the presence of perched groundwater and the extent of the landfill. The collection of shallow surface soil samples additionally enable PB to assess any risks to future site users arising from potentially elevated concentrations of contaminants within the capping material. The analysis of leachate and eluate to assess if there is a source in unsaturated ground that may pose a risk to groundwater at the site.. Combined Phase I and Phase II Investigation HPE98123A January 2009 Prepared by PB for Devon County Council Page 41 SECTION 5 SITE INVESTIGATION Table 5.1: Scope of Site Investigation Works Rationale 10 No. deep boreholes installed for soil gas, soil vapour and groundwater monitoring. The installation and monitoring of the deep boreholes enable PB to assess any risks to future site users arising from potentially elevated ground gas and vapour concentrations in natural ground at the site. Six rounds of soil gas, soil vapour and four rounds of groundwater monitoring. The influence on controlled waters (Minor Aquifer) of contaminants originating from the site can also be identified through groundwater monitoring. 5.2.2 All site works were undertaken in accordance with BS10175: 2001 (‘Investigation of Potentially Contaminated Sites’). 5.2.3 All works were carried out by experienced personnel under the supervision of a PB Engineer. A minimum of 2 persons were in attendance when an excavation was in progress (e.g. PB Engineer and JCB/drill rig operator). If the PB Engineer was called away from the excavation area, the excavation operative ceased work until the PB Engineer returned. Before excavation commenced, the proximal area was cleared of non-essential personnel. 5.2.4 Suitable personal protective equipment was worn at all times during the works. Eating, drinking or smoking was not permitted on site except in designated messing areas. 5.2.5 Prior to any excavation works, site services were be located using available service plans (Appendix H), a Cable Avoidance Tool (CAT) and a signal generator (where appropriate). As an additional precaution, excavations were hand dug to 1.2 mBGL where possible. 5.2.6 All arisings were placed upon heavy-duty plastic sheeting to avoid surface contamination. Excess soil arisings that required disposal were stored in accordance with best practice. This involved locating an area where a lockable skip was accessible by the site staff for the safe storage of the site soils. At the end of the work, the skip was removed by a licensed contractor for off-site disposal, once the required Waste Management 2 classification had been determined. 5.2.7 Waste water collected during the purging of groundwater from boreholes was stored in bunded drums and removed by a licensed contractor for off site disposal. All such works will comply with PB’s Environmental Monitoring System (ISO 14001 accredited). Boreholes 5.2.8 Deep boreholes were excavated using a Hollow Stem Rotary Drilling Rig. This technique has the advantage of recovering soil cores within a split spoon core, which can easily be washed after each use. The excavation of window sample boreholes was achieved through the use of a smaller drop weight window sampling rig, which recovers cores using disposable semi-rigid polycarbonate plastic liners. These sampling techniques allow for the accurate logging of subsurface ground conditions and negate the risk of cross contaminating the ground surface. In addition, it also provides sufficient material for sampling purposes, which meant that the PB Engineer Combined Phase I and Phase II Investigation HPE98123A January 2009 Prepared by PB for Devon County Council Page 42 SECTION 5 SITE INVESTIGATION was able to sample from discrete depths accurately. These types of drilling techniques are extremely clean and resulted in minimal disruption to the site. 5.2.9 The rigs were securely positioned over borehole locations prior to commencement of sampling. On uneven ground or slopes, the rig was prior to sampling. 5.2.10 When sampling was in progress, an area of approximately 2m around the sampling rig was clearly marked preventing unauthorised access. 5.2.11 Where it was required that drilling equipment (including casing) be washed down after every use. This w carried out into impermeable containers over hardstanding areas (where possible). Spill kits including absorbent pads were held on site. Trial Pits 5.2.12 Trial pits were excavated using a JCB type excavator. Under no circumstances did anyone enter an excavation. All samples were collected from excavation arisings only. 5.2.13 Trial pits were backfilled immediately upon completion, with the arisings placed back in reverse order of excavation. No trial pits were left unsupervised or left open overnight. 5.2.14 ‘Deep Excavation’ warning signs were placed in the proximity of open excavations. Barriers and warning tape were also placed around open excavations preventing unauthorised access to the working area. 5.3 Laboratory Analysis 5.3.1 A total of 115 No. soil samples were collected during site works and submitted for laboratory analysis from 10 No. deep boreholes (maximum depth 16.2 mBGL), 4 No. window sample boreholes (maximum depth 5.0 mBGL) and 30 No. trial pits (maximum depth 4.3 mBGL). The positions of all borehole and trial pit locations are illustrated within Figure 2. The following determinands were scheduled for laboratory analysis: Table 5.2: Basic Suite of Determinands Limit of Detection (mg/kg) UKAS Accreditation Technique 5 Y (MCERTS) ICPMS Cadmium 0.5 Y (MCERTS) ICPMS Chromium 1 Y (ISO17025) ICPMS Lead 1 Y (MCERTS) ICPMS 0.5 Y (MCERTS) ICPMS Nickel 1 Y (MCERTS) ICPMS Selenium 1 Y (ISO17025) ICPMS Determinand Arsenic Mercury Combined Phase I and Phase II Investigation HPE98123A January 2009 Prepared by PB for Devon County Council Page 43 SECTION 5 SITE INVESTIGATION Table 5.2: Basic Suite of Determinands Limit of Detection (mg/kg) UKAS Accreditation Technique Copper 1 Y (MCERTS) ICPMS Zinc 1 Y (MCERTS) ICPMS 0.5 Y (ISO17025) 0.1 units Y (MCERTS) Electrometric 5 - Colourimetry 0.01% Y Ion Chromatography Sulphide (S ) 0.5 - Colourimetry Sulphur (S) (total) 1.0 Y (MCERTS) Colourimetry 1 Y (MCERTS) Colourimetry 0.3 Y HPLC MCERTS Submitted Colourimetry 5 0.5 Y (MCERTS) GCFID Determinand Boron (B) (Water Soluble) pH Value Chromium (VI) Sulphate (SO4 )(total) Cyanide (total, free) Phenols ICPMS Thiocyanate Speciated PAH UKAS - United Kingdom Accreditation Service ICPMS - Inductively Coupled Plasma Mass Spectrometry HPLC - High Performance Liquid Chromatography GCFID - Gas Chromatography Flame Ionization Detection TPH - Total Petroleum Hydrocarbons 5.3.2 Additional determinands were analysed at locations where visual or olfactory evidence of contamination was apparent, and at further locations to provide coverage of the site. Up to 30 No. soil samples were additionally scheduled for the following determinands: Speciated Total Petroleum Hydrocarbons (TPH) using Criteria Working Group Methodology (TPHCWG); Asbestos (screen); and Volatile Organic Contaminants (VOC). 5.3.3 To support the derivation of appropriate tier 1 screening values, a total of 44 No. soil samples were analysed for Total Organic Carbon (TOC). 5.3.4 Groundwater samples were collected from the 9 No. deep boreholes installed during this investigation and 4 boreholes previously installed over four monitoring rounds, totalling 52 No. samples. Samples were stored in cool boxes (<4°C) and couriered to the laboratory no more than 24 hours after sampling. All samples were preserved in accordance with laboratory guidance. 5.3.5 Groundwater samples were collected and analysed for the following determinands: Combined Phase I and Phase II Investigation HPE98123A January 2009 Prepared by PB for Devon County Council Page 44 SECTION 5 SITE INVESTIGATION Table 5.3: Basic Suite of Determinands Determinand Limit of Detection (ug/l) UKAS Accreditation Technique 1 Y ICPMS Cadmium 0.5 Y ICPMS Chromium 1 Y ICPMS Lead 1 Y ICPMS 0.5 Y ICPMS Nickel 1 Y ICPMS Selenium 1 Y ICPMS Copper 1 Y ICPMS Zinc 1 Y ICPMS Boron 20 Y ICPMS 0.1 units Y Electrometric Chromium (VI) 50 - Colourimetry SO4 50 Y Ion Chromatography SO 50 - Colorimetric Cyanide (total, free) 50 - Colorimetric Phenols 300 Y HPLC Thiocyanate 500 - Colorimetric Speciated PAH 0.05 Y GCFID Speciated TPH 0.1 Y GCFID VOC 0.1 Y Chromatographic COD 10000 Y Colorimetric BOD 3000 - Electrometric Hardness 5000 Y Ion Chromatography Chloride 100 Y Ion Chromatography Ammoniacal Nitrogen 10 - Colorimetric OC Pesticides 0.2 - GC-MS OP Pesticides 0.2 - GC-MS ON Pesticides 0.2 - GC-MS Arsenic Mercury pH Value (total) GC-MS - Gas Chromatography-Mass Spectrometry Combined Phase I and Phase II Investigation HPE98123A January 2009 Prepared by PB for Devon County Council Page 45 SECTION 5 SITE INVESTIGATION 5.3.6 Where groundwater was not present and where there was visual and/or olfactory evidence of contamination, leachability testing was undertaken to indicate the potential (worst case) for soil contaminants to leach from soils. Leachability testing was undertaken on 30 No. soil samples. 5.3.7 All soil and water samples were analysed by Chemtest, Newmarket, a UKAS and MCerts accredited laboratory. Full schedules of sample analyses are provided in Appendix F. 5.4 General Ground Conditions 5.4.1 Ground conditions have been logged in accordance with the requirements of BS5930:1999. Detailed logs for the boreholes and trial pits are provided in Appendix E, along with photographs of exploratory locations. 5.4.2 A summary of the ground conditions identified during the investigation is given below. Made Ground 5.4.3 Made Ground was encountered within 1 borehole and 11 trial pit locations (BH110, TP08, TP19, TP20, TP21, TP22, TP23, TP24, TP25, TP26, TP27 and TP28). The average thickness of Made Ground within the trial pits is 1m and 3m within BH110. Generally the Made Ground is sandy CLAY or clayey SAND with sandstone and limestone gravel. It is understood that Made Ground was used as capping material and to generate a mature sand dune appearance in keeping with the surrounding area. Fill Material 5.4.4 Fill material was encountered within all the exploratory locations with the exception of BH101, BH102 and BH103 and TP05, TP06, TP07 and TP30. These locations were specifically located out side the landfill to determine the ground conditions outside the landfill area. 5.4.5 The average thickness of the landfill material identified within the boreholes was 4.6m. The majority of the trial pits did not identify the base of the landfill indicating a greater depth of fill material than 3.5m. Trial Pits TP01 to TP04 and the window sampling locations were located within the entrance road area. The average thickness of fill in these locations was 2.65m. TP16 was located on the western side of the landfill to identify the extent of the landfill in that area and identified a thickness of 1.2m of fill material. 5.4.6 Generally the fill material was a dark grey brown sandy gravely CLAY or clayey gravely SAND with occasional cobbles with a high organic content, consisting of broken down refuse or broken down garden waste. The gravel and cobbles consisted of concrete, brick rubble and sandstone. Also present in abundance is glass, metal, wood (including chipboard) and plastic (including bags and bottles). 5.4.7 The fill material found within the entrance road was a sandy GRAVEL or gravely SAND containing glass, coke, clinker, brick, ceramics, crushed tarmac, sandstone and limestone. At some of the locations bent metal (possibly old drums) was identified with some wood and plastic. Combined Phase I and Phase II Investigation HPE98123A January 2009 Prepared by PB for Devon County Council Page 46 SECTION 5 SITE INVESTIGATION 5.4.8 Additional visual and olfactory indicators that may be of some concern identified during the investigation are described in Table 5.4: Table 5.4: Visual and Olfactory Identification of Potential Contaminants Exploratory Location Visual Evidence Olfactory Evidence - Elevated levels of landfill gas detected during drill area monitoring. BH105 A few spots of a sheen on the water Strong odour of decomposing material. BH107 - Odour of decomposing material BH110 - Elevated levels of landfill gas detected during drill area monitoring. WS1 Occasional Tarmac between 1.5 and 1.8m - WS2 Crushed Tarmac - TP01 Fragments of coke and clinker. - TP02 Fragments of rusted metal scraps (including possible old drums) and coke and clinker. - BH104 TP03 Fragments of rusted metal scraps (including possible old drums) - TP15 - Elevated levels of VOCs recorded on the PID TP18 - Elevated levels of VOCs recorded on the PID TP19 - Elevated levels of VOCs recorded on the PID TP21 - Elevated levels of VOCs recorded on the PID TP29 Occasional ash and clinker - PID - Photo Ionisation Detector Natural Ground 5.4.9 BH101, BH102 and BH103 and TP05, TP06, TP07 and TP30 were specifically located within the natural ground to assess the nature of the natural ground and to determine the extent of the landfill. All the boreholes encountered the natural ground at approximately 4.6 mBGL as did TP16 at 1.2 mBGL. The natural ground was encountered in the trial pits and window sample holes located in the entrance road at a depth of approximately 2.6 mBGL. 5.4.10 Topsoil was identified in all the exploratory location consisting of organic rich sand in the natural ground and increased clay within the landfill area. Below the Topsoil was Combined Phase I and Phase II Investigation HPE98123A January 2009 Prepared by PB for Devon County Council Page 47 SECTION 5 SITE INVESTIGATION generally coarse grained gravely SAND with occasional cobbles. Occasionally the sand was inter-bedded with soft clayey sandy SILT. 5.4.11 Below the sand, between 2-3m below ordnance datum is soft grey clayey sandy SILT approximately 5m thick. Below the silt at approximately 8m below ordnance datum is dark grey well fractured fine grained SANDSTONE with some ironstone staining, inter-bedded with very soft grey sandy very gravely CLAY. The sandstone is thought to be the well weathered start of the Crackington Formation. 5.4.12 There was no visual or olfactory evidence of potential contamination within the natural ground. 5.5 Buried Structures 5.5.1 The locations of buried structures encountered during excavations are provided in Table 5.5. Table 5.5: Locations of buried structures encountered during excavations Exploratory Location Depth (m BGL) BH104A Buried Structure 2.0 Unknown, believed to be concrete 2.0 Hard layer of crushed compacted concrete, very difficult to drill through. 2.5 Hard layer of crushed compacted concrete, very difficult to drill through. 3.6 Hard layer of crushed compacted concrete, very difficult to drill through. TP11 2.0 Large sub-angular boulder of concrete TP16 1.0 Railway sleeper BH107 BH109 BH110 5.6 Groundwater Observations 5.6.1 A total of 9 No. boreholes were excavated and installed during the site works to monitor groundwater quality surrounding and beneath the site and leachate quality within the landfill. Deep boreholes were installed into the sands below the landfill material. 5.6.2 Depths to the groundwater surface within these monitoring wells are given within Table 5.6a. Approximate details of the tide state during each monitoring visit are given in Table 5.6b (Tide data from Proudman Oceanographic Laboratory (Natural Environment research Council) – www.pol.ac.uk). Combined Phase I and Phase II Investigation HPE98123A January 2009 Prepared by PB for Devon County Council Page 48 SECTION 5 SITE INVESTIGATION Table 5.6a: Results of Groundwater Monitoring Visits Groundwater Levels (AOD m) Location 05/08/08 BH 101 13/08/08 22/08/08 29/08/08 05/09/08 12/09/08 Well not installed BH 102 2.399 1.388 2.317 1.436 2.357 1.377 BH 103 2.397 0.695 1.006 1.783 - 1.782 BH 104 2.017 1.223 1.954 1.578 4.752 1.544 BH 105 2.593 0.953 1.599 1.161 1.303 1.401 BH 106 2.139 2.422 3.899 1.083 0.881 1.23 BH 107 2.575 1.985 2.288 1.581 0.928 2.017 BH 108 3.743 2.617 3.998 2.643 3.271 2.695 BH 109 5.181 5.273 3.011 5.261 5.401 5.38 BH 110 1.996 1.836 3.965 1.839 2.031 1.851 Height (m AOD) Tide State Table 5.6b: Tide Data Height (m AOD) Date Tide State 05/08/08 High Tide 08.15 4.4 Low Tide 14.45 -3.55 13/08/08 Low Tide 09.00 -1.55 High Tide 15.50 2.65 22/08/08 High Tide 09.00 3.8 Low Tide 15.00 -3.2 29/08/08 Low Tide 10.30 -3.3 High Tide 17.00 4.2 05/09/08 High Tide 09.00 3.95 Low Tide 14.30 -2.5 12/09/08 Low Tide 09.30 -2.3 High Tide 16.00 3.2 Time Time 5.6.3 Groundwater monitoring visits were undertaken by a PB Engineer on 5, 13, 22 and 29 August 2008 and 5 and 12 September. Water sampling was undertaken on the 22 August and 5 and 12 September. A total of 52 No. groundwater samples were taken from the deep boreholes. All samples were submitted for laboratory analysis. The results of water monitoring are given within Appendix E and the results of water analysis are provided within Appendix F. 5.6.4 Tide data from the nearest tidal monitoring station in Ilfracombe and against weather data from the nearest weather station in Chivenor (Nr. Barnstable) has also been obtained. Combined Phase I and Phase II Investigation HPE98123A January 2009 Prepared by PB for Devon County Council Page 49 SECTION 5 SITE INVESTIGATION 5.7 Surface Water Observations 5.7.1 Northam Burrows is located on a land spit and is surrounded by coastal waters on three sides. Surface water was not sampled as part of this investigation. 5.8 Photo Ionisation Detector (PID) 5.8.1 A PID was used on site during the works to screen samples with visual and/or olfactory evidence of contamination for the presence of volatile organic compounds. Soil samples were bagged, allowed to equilibrate and screened for a minimum period of 60 seconds. 5.8.2 All deep boreholes and window sample boreholes were installed for vapour monitoring. Each borehole was screened with a PID over six monitoring rounds to detect the presence of volatile organic compounds in the soil environment, and to account for any interference this may cause with the ground gas monitoring undertaken. 5.8.3 Screening results are provided within Appendix E. 5.9 Soil Gas Emissions (CH4, CO2 and O2) 5.9.1 9 boreholes were installed for gas monitoring. Each borehole was gas monitored with an infra-red gas analyser (GA2000) over six monitoring rounds to assess any risks to future site users from soil gas. Results of soil gas measurements methane, carbon dioxide and oxygen are given in Appendix E. 5.10 Quality Assurance / Quality Control 5.10.1 The data collection, storage and preparation of this report has been undertaken in accordance with PB’s Integrated Management System which operates within the standards outlined in ISO 9001 (BSI Certificate No. Q06143) and ISO 14001 (BSI Certificate No. A12283). 5.11 Ground Conditions and Hydrogeology 5.11.1 In the absence of ‘as-built’ construction drawings, the following section is based on interpretation of the available site investigation data. 5.11.2 Based on the available information, the following seem likely: 5.11.3 Landfilled material extends into the underlying Natural Ground comprising silts and sands, with no apparent liner system or cover; 5.11.4 The landfill appears higher in elevation than surrounding areas, so some radial runoff may be expected as may some doming of leachate within the landfill; 5.11.5 The general groundwater gradient within the surrounding strata appears to be influenced by both the proximity to the sea and estuary; Combined Phase I and Phase II Investigation HPE98123A January 2009 Prepared by PB for Devon County Council Page 50 SECTION 5 SITE INVESTIGATION 5.11.6 The majority of waste material within the landfill is saturated, and the observed data provide no evidence for the presence of an unsaturated zone within the Natural Ground directly beneath the landfill; 5.11.7 Groundwater and leachate below and within the landfill are tidally influenced and are in hydraulic continuity with sea and estuary; and 5.11.8 The underlying solid geology comprises the Crackington Formation, which is a Minor Aquifer. Combined Phase I and Phase II Investigation HPE98123A January 2009 Prepared by PB for Devon County Council Page 51