Geoenvironmental Appraisal
Land at Preston Road, Hull For Keepmoat Homes Yorkshire East & Strata Homes
Report no: 3039/1 Date: January 2019
Tel: 01937 545330 • [email protected] • www.lithos.co.uk
SUMMARY OF GEOENVIRONMENTAL ISSUES
Job No. 3039 Site area/ha 16 hectares Client: Keepmoat Homes Yorkshire East & Strata Homes NGR: TA 135 302 Site: Preston Road, Hull Nearest postcode: HU9 5UN
The site is located approximately 4km east of Hull city centre comprises part of the Preston Road Housing Estate. Prior to the ongoing demolition programme there were about 500 houses (256 pairs of semi-detached, 2-storey properties); about 50% of buildings across the site had been demolished; about 50% were vacant but remained standing; and about 1% remained occupied. Existing (and recently demolished) houses built in the 1930s were constructed on shallow (c. 0.5m deep) strip footings, and no obvious signs of structural distress were noted during the walkover. Lithos were commissioned to provide a geoenvironmental appraisal of the site, which it is understood is to be redeveloped with residential dwellings. Lithos’ investigation included a review of the site's history and environmental setting, and a ground investigation comprising 79 trial pits, 10 deep cable percussion boreholes and 40 road cores with dynamic sample follow-on. A summary of salient geoenvironmental issues is provided in the table below.
Issue Remarks The site can be divided into three areas based on ground conditions – Area A (housing recently Areas cleared), Area B (houses remain) and Area C (existing estate roads). A veneer of Demolition Arisings or Made Ground Topsoil to depths of up to 1.1m, but typically c. 0.7m Made ground across areas of demolished land & in the gardens of the remaining houses. Comprises Tidal Flat Deposits which are typically of medium to high strength to depths of c. 1m becoming low to extremely low strength with depth. Natural ground High strength Cohesive Glacial Deposits (Till) are present from c. 7m and extend to depths in excess of 20m. Made Ground across the majority of Areas A and & B is considered suitable to remain in gardens beneath a nominal clean cover of 300mm. Cohesive Made Ground was only encountered 3 of the 89 exploratory holes excavated across the entire site, and significant contamination was only reported in one of these - TP45 (Area A). Cohesive Contamination Made Ground in the vicinity of TP45 is considered contaminated and should be isolated beneath hardstand/floor slabs/highways, or beneath a clean cover of 1,000mm. Ash and & Clinker from beneath Area C (existing roads) should be suitable for isolation beneath hardstand/floor slabs/highways. Mining & The site lies beyond the CA defined coalfields. quarrying No known quarrying has occurred within 250m of the site’s boundary. No significant sources of hazardous gas have been identified and the site lies in an area where less than 1% of properties are above the radon action level. Hazardous gas However, thin beds (maximum thickness of 200mm) of pseudo-fibrous Peat were encountered in 2 of the 10 boreholes at the base of the Tidal Flat Deposits (around 6.5m). Consequently, whilst risks are considered very low, gas monitoring is now being undertaken. Preparatory Demolition of the remaining houses (ongoing) & grubbing up of roads (where they are not being works retained). Lithos have given ‘high level’ consideration to the possibility of a shallow founding solution, but the presence of made ground, high shrinkability clays, (felled) trees, and current-day building regulation / warranty requirements would all require a minimum founding depth of at least 1.0m, and this results in Foundations founding towards (in some places, likely below) the base of the desiccated (high strength) layer. Assuming a founding depth of 1.0m, preliminary calculations suggest that line loads would need to be less than about 20kN/m run. Consequently, at this stage a shallow founding solution is considered unlikely to be viable here and piles will almost certainly be required. Groundwater Excavations should remain dry & stable in the short term; although some relatively minor seepages & excavations might be encountered in shallow soils. Flooding & Soakaways will not provide a suitable means of surface water disposal. drainage The site lies in a Flood Zone 3, but benefits from flood defences. Existing highways typically comprise a 40mm surface course, over a base course 150mm, over Sub-Base Highways (comprising chalk and/or brick), over Ash & Clinker. The total road construction varies from c. 300mm to 600mm depth.
Significant developer abnormals relating to geoenvironmental issues at the site are: • Piled foundations • Likely need for surface water balancing
This brief summary should not be assumed to represent a complete account of all the potential geo-environmental issues that may exist at the site. As such it is strongly recommended that the report be read in its entirety.
CONTENTS 1 INTRODUCTION ...... 1 1.1 THE COMMISSION AND BRIEF...... 1 1.2 THE PROPOSED DEVELOPMENT ...... 1 1.3 REPORT FORMAT AND LIMITATIONS ...... 1 2 SITE DESCRIPTION ...... 2 2.1 GENERAL ...... 2 2.2 SITE FEATURES ...... 2 2.3 SITE OPERATIONS ...... 3 3 SITE HISTORY ...... 4 4 ENVIRONMENTAL SETTING ...... 6 4.1 GENERAL ...... 6 4.2 GROUND STABILITY ...... 7 4.3 UXO ...... 7 5 GROUND INVESTIGATION DESIGN ...... 8 5.1 ANTICIPATED GROUND CONDITIONS & POTENTIAL ISSUES ...... 8 5.2 PRELIMINARY CONCEPTUAL SITE MODEL...... 8 5.3 GROUND INVESTIGATION DESIGN & STRATEGY ...... 9 6 FIELDWORK ...... 10 6.1 OBJECTIVES ...... 10 6.2 EXPLORATORY HOLE LOCATION CONSTRAINTS ...... 10 6.3 SCOPE OF WORKS...... 10 7 GROUND CONDITIONS ...... 11 7.1 GENERAL ...... 11 7.2 MADE GROUND ...... 11 7.3 OBSTRUCTIONS ...... 13 7.4 ROADS (AREA C) ...... 14 7.5 NATURAL GROUND ...... 15 7.6 VISUAL & OLFACTORY EVIDENCE OF ORGANIC CONTAMINATION ...... 16 7.7 GROUNDWATER ...... 16 7.8 STABILITY ...... 17 7.9 REVISED CONCEPTUAL GROUND MODEL (GROUND CONDITIONS) ...... 17 8 CONTAMINATION (ANALYSIS) ...... 18 8.1 GENERAL ...... 18 8.2 TESTING SCHEDULED ...... 18 8.3 SOIL CONTAMINATION RESULTS ...... 19 9 CONTAMINATION (QUALITATIVE RISK ASSESSMENT & REMEDIATION) ...... 24 9.1 SUMMARY OF SIGNIFICANT CONTAMINATION ...... 24 9.2 REVISED CONCEPTUAL GROUND MODEL (CONTAMINATION) ...... 24 9.3 ENVIRONMENTAL SETTING & END USE ...... 24 9.4 POLLUTANT LINKAGES ...... 25 9.5 POTENTIAL REMEDIATION OPTIONS ...... 25 9.6 SUMMARY OF POTENTIAL POLLUTANT LINKAGES & MITIGATION ...... 28 9.7 WASTE CLASSIFICATION ...... 28 10 HAZARDOUS GAS ...... 30 10.1 METHANE & CARBON DIOXIDE ...... 30 10.2 RADON ...... 30
11 GEOTECHNICAL TESTING ...... 31 11.1 GENERAL ...... 31 11.2 ATTERBERG LIMITS ...... 31 11.3 SOLUBLE SULPHATE AND PH ...... 31 11.4 ONE DIMENSIONAL CONSOLIDATION TESTS ...... 32 11.5 UNDRAINED SHEAR STRENGTH TESTING ...... 33 11.6 STANDARD PENETRATION TEST (SPT) ...... 34 11.7 DISCUSSION OF GEOTECHNICAL LABORATORY RESULTS ...... 34 12 GEOTECHNICAL ISSUES ...... 34 12.1 CONCEPTUAL SITE MODEL ...... 34 12.2 MINING & QUARRYING ...... 35 12.3 SITE REGRADE AND/OR GROUND IMPROVEMENT ...... 35 12.4 FOUNDATION RECOMMENDATIONS ...... 35 12.5 FLOOR SLABS ...... 37 12.6 DESIGNATED CONCRETE MIXES ...... 37 12.7 EXCAVATIONS ...... 37 12.8 DRAINAGE ...... 38 12.9 HIGHWAYS ...... 38 12.10 EXTERNAL WORKS ...... 38 13 REDEVELOPMENT ISSUES ...... 39 13.1 GENERAL ...... 39 13.2 REMEDIATION STRATEGY ...... 39 13.3 CONTROL OF EXCAVATION ARISINGS ...... 39 13.4 GOOD PRACTICE GUIDANCE ...... 40 13.5 NEW UTILITIES ...... 40 13.6 HEALTH & SAFETY ISSUES - CONSTRUCTION WORKERS ...... 41 13.7 POTENTIAL DEVELOPMENT CONSTRAINTS ...... 41 14 SUMMARY OF CONCLUSIONS AND RECOMMENDATIONS ...... 42 14.1 GENERAL ...... 42 14.2 MINING ...... 42 14.3 HAZARDOUS GAS ...... 42 14.4 CONTAMINATION & REMEDIATION ...... 43 14.5 FOUNDATIONS ...... 43 14.6 FLOODING ...... 43 14.7 DRAINAGE ...... 43 14.8 HIGHWAYS ...... 43 14.9 FURTHER WORK ...... 44
ANNEXES ANNEX I – GROUND INVESTIGATION DATA Table 1 Summary of ground conditions
ANNEX II – SUMMARY CONTAMINATION DATA (SOILS) Table 1 Summary of contamination results (inorganics) Table 2 Summary of contamination results (leachability) Table 3 Summary of contamination results (organics)
ANNEX III – SUMMARY TABLES OF GEOTECHNICAL TESTING Table 1 Summary of contamination results (inorganics) Table 2 Summary of contamination results (leachability) Table 3 Summary of contamination results (organics)
APPENDICES Appendix A - General notes 01 Environmental setting 02 Ground investigation fieldwork 03 Geotechnical testing 04 Contamination laboratory analysis & interpretation
Appendix B - Drawings Drawing Revision Title 3039/1 - Site location plan 3039/3 - Site features 3039/4 - Site photographs 3039/5 - Preliminary conceptual site model 3039/6 - Exploratory hole locations & Site Areas 3039/7 - Revised conceptual site model
Appendix C - Commission Appendix D - Historical OS plans Appendix E - Search responses From Date Content Landmark 04/10/2018 Environmental search data 04/10/2018 Natural ground stability report British Geological Society 04/10/2018 Geological logs
Appendix F to H - Exploratory records Appendix F TP01 to TP79 Appendix G BH01 to BH10 Appendix H WS01 to 40 Appendix I - Chemical test results Appendix J - Geotechnical test results Appendix K - Water monitoring results
FOREWORD (geoenvironmental appraisal report)
This report has been prepared for the sole internal use and reliance of the Client named on page 1. This report shall not be relied upon or transferred to any other parties without the express written authorisation of Lithos Consulting Limited (Lithos); such authorisation not to be unreasonably withheld. If any unauthorised third party comes into possession of this report, they rely on it at their peril and the authors owe them no duty of care and skill.
This report has been reviewed by a Competent Person, as defined in the National Planning Policy Framework. We ensure that all projects are managed by individuals with necessary experience, relevant qualifications, and current membership of a relevant professional organisation. Records of engineers, project managers and reviewers involved in this project are maintained by us. Lithos QA/QC procedures for all our work forms an integral part of our ISO9001 accreditation and as such is regularly audited.
The report presents observations and factual data obtained during our site investigation and provides an assessment of geoenvironmental issues with respect to information provided by the Client regarding the proposed development. Further advice should be sought from Lithos prior to significant revision of the development proposals.
The report should be read in its entirety, including all associated drawings and appendices. Lithos cannot be held responsible for any misinterpretations arising from the use of extracts that are taken out of context. However, it should be noted that in order to keep the number of sheets of paper in the hard copy to a minimum, some information (e.g. full copy of the Landmark/Groundsure Report) is not included in the pdf, by request, it can be provided on a CD.
The findings and opinions conveyed in this report (including review of any third-party reports) are based on information obtained from a variety of sources as detailed within this report, and which Lithos believes are reliable. All reasonable care and skill has been applied in examining the information obtained. Nevertheless, Lithos cannot and does not guarantee the authenticity or reliability of the information it has relied upon.
The report represents the findings and opinions of experienced geoenvironmental consultants. Lithos does not provide legal advice and the advice of lawyers may also be required.
Intrusive investigation can only investigate shallow ground beneath a small proportion of the total site area. It is possible therefore that the intrusive investigation undertaken by Lithos, whilst fully appropriate, may not have encountered all significant subsurface conditions. Consequently, no liability can be accepted for conditions not revealed by the exploratory holes. Any opinion expressed as to the possible configuration of strata between or below exploratory holes is for guidance only and no responsibility is accepted as to its accuracy
It should be borne in mind that the timescale over which the investigation was undertaken may not allow the establishment of equilibrium groundwater levels. Particularly relevant in this context is that groundwater levels are susceptible to seasonal and other variations and may be higher during wetter periods than those encountered during this commission.
Where the report refers to the potential presence of invasive weeds such as Japanese Knotweed, or the presence of asbestos containing materials, it should be noted that the observations are for information only and should be verified by a suitably qualified expert.
This report assumes that ground levels will not change significantly from those existing at present and that houses will be of two storey construction. If this is not to be the case, then some modification to this report may be required.
Lithos cannot be responsible for the consequences of changing practices, revisions to waste management legislation etc that may affect the viability of proposed remediation options.
Lithos reserve the right to amend their conclusions and recommendations in the light of further information that may become available.
GEOENVIRONMENTAL APPRAISAL of land at PRESTON ROAD, HULL
1 INTRODUCTION
1.1 The commission and brief
1.1.1 Lithos Consulting Limited were commissioned by Keepmoat Homes Yorkshire East & Strata Homes to carry out a geoenvironmental appraisal of land off Preston Road, Hull.
1.1.2 Correspondence regarding Lithos’ appointment, including the brief for this investigation, is included in Appendix C. The agreed scope of works included:
• A site walkover and inspection • An assessment of the land use history • Determination of the site's environmental setting • An intrusive ground investigation comprising 79 trial pits, 10 deep cable percussion boreholes, and 40 road cores with dynamic sample follow-on • Assessment of the geotechnical properties of the near surface deposits to enable provision of foundation and highway recommendations • A qualitative assessment of contamination risks • Recommendations for the necessary site preparatory and remediation works
1.1.3 Primary aims of this investigation were to identify salient geoenvironmental issues affecting the site to support the submission of a planning application, and also to enable Keepmoat & Strata to obtain budget costs for: foundations; gas protection measures; and site preparatory and remediation works.
1.2 The proposed development
1.2.1 It is understood that consideration is being given to redevelopment of the site with ‘traditional’ two storey residential dwellings with associated gardens, POS and adoptable roads and sewers. No site layout has been provided at this stage.
1.2.2 It is understood that Holmpton Grove & St. Johns Grove may be retained, but other roads which cross the site are likely to be removed.
1.3 Report format and limitations
1.3.1 All standard definitions, procedures and guidance are contained within Appendix A, which includes background, generic information on:
• Assessment of the site's environmental setting • Ground investigation fieldwork • Geotechnical testing • Contamination testing
1.3.2 General notes and limitations relevant to all Lithos geoenvironmental investigations are described in the Foreword and should be read in conjunction with this report. The text of the report draws specific attention to any modification to these procedures and to any other special techniques employed.
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2 SITE DESCRIPTION
2.1 General
2.1.1 The site’s location is shown on Drawing 3039/1 presented in Appendix B to this report. Site details are summarised in the table below.
Detail Remarks Location 4km east of Hull city centre NGR TA 135 302 Approximate area 16 hectares (39.5 acres) Underground gas, water, sewers & electric run beneath existing roads & footpaths. Known services However, all utilities are understood to have been cut off in footpaths where houses have been demolished.
2.2 Site features
2.2.1 Lithos completed a walkover survey of the site on the 8th October 2018.
2.2.2 Existing salient features, at the time of the walkover are presented on Drawing 3039/3 in Appendix B to this report and summarised in the table below.
Feature Remarks Current Access Off Preston Road. Topography Relatively smooth & flat across entire site. 1,500m2 buildings Approximate areas 3,500m2 tarmac hardstand 155,000m2 garden/overgrown areas North & east – Preston Road & Marfleet Road (respectively). Nature of boundaries South – 8ft steel palisade fencing. West – no physical boundary. North – Preston Road, with a6th form academy beyond (with associated parking, playing fields etc & community buildings). South – Primary school with associated playing field & residential dwellings. Surrounding land uses East – residential dwellings, allotments & school with associated playing field & parking. West – Holderness Drain, with residential dwellings beyond.
2.2.3 A selection of site photographs is included on Drawing 3039/4.
2.2.4 The site can be accessed from Preston Road along the northern boundary; from St. Johns Grove in the south western corner; or, off Marfleet Lane along the eastern boundary.
2.2.5 A total of 9 roads cross the site; Flinton Grove, Foston Grove, Hilston Grove and Holmpton Grove all run roughly north to south; Brigham Grove, Wansford Grove, Cranswick Grove and St. Johns Grove all run east to west.
2.2.6 It is understood from discussions with Hull City Council that existing roads are likely to be constructed on a sub-base of Ash & Clinker and crushed brick (c. 500mm thick), topped-off with a macadam surface course.
2.2.7 Much of the north east of the site has undergone demolition; land here is relatively smooth and flat. Where demolition has occurred recently there is little/no growth of vegetation, whilst where demolition has occurred a while ago the ground is overgrown with brambles and weeds.
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2.2.8 Much of the south west of the site has been cleared of residents and is awaiting demolition. Empty houses remain which are of two storey semi-detached construction. The houses have been secured with metal shutters over the doors and windows. Around the empty houses there is much evidence of vandalism including graffiti, and evidence of bonfires; at least 3 of the empty houses had clear signs of fire damage.
2.2.9 Each empty house has an associated concrete drive, a small front garden and a larger rear garden. The empty garden spaces are all overgrown but have a range of features which include areas of: concrete, block paving, paving slab & macadam hardstand, semi-mature & mature trees, wooden sheds, brick-built outbuildings and a variety of wooden, concrete and metal boundary fences.
2.2.10 At the time of writing several (understood to be 4) houses remained occupied by residents who were in the process of arranging alternative accommodation. During Lithos’ intrusive investigation (see Section 6) one of the residents was in the process of ‘moving out’ from a dwelling at the site.
2.2.11 Within the south west, pairs of semi-detached dwellings had been demolished leaving ‘gaps’ in the general pattern of houses. In the north east, occasional pairs of semi-detached houses with their associated gardens and boundary fences remained standing.
2.2.12 A former pair of houses located at the junction of St. Johns Grove and Hilston Grove had been demolished but floor slabs etc still remained. It is understood that these properties had undergone an ‘emergency demolition’; presumably due to being fire damaged etc; but grubbing up of floor slabs etc had yet to be undertaken.
2.2.13 The locations of demolished and existing plots are shown on Drawing 3039/3 in Appendix B.
2.2.14 Houses in the centre east of the site which face onto Wansford Grove had been graffitied by an impromptu group calling themselves Bankside Gallery. The open-air legal art gallery was set up, with Council approval, following a visit to the city by the infamous international street artist Banksy in January 2017; Banksy’s work of art on Scott Street bridge had quickly become Hull’s unlikeliest tourist attraction.
2.2.15 An area of about 6,000m2 in the centre-east, cordoned off with Heras fencing, was occupied by two 360o excavators, skips and a welfare cabin. This compound was being used by demolition workers at the time of Lithos’ walkover.
2.3 Site operations
2.3.1 Prior to the ongoing demolition programme there were about 500 houses (256 pairs of semi- detached, 2-storey properties); see photographs included on Drawing 3039/4. At the time of writing the site was undergoing demolition; about 50% of buildings across the site had been wholly demolished, about 50% remained in-situ but were empty and boarded up, and 1% were still inhabited.
2.3.2 It is understood that the demolition specification (a copy of which has not been made available to Lithos) requires removal of floor slabs and foundations, with turnover of ground to a depth of 1.0m within plot footprints and 0.5m in gardens (to remove any obstructions).
2.3.3 The specification also requires disconnection of all services within the existing footpaths.
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3 SITE HISTORY
3.1 Site centred extracts from Ordnance Survey (OS) plans dating back to 1855 have been examined. Some of these plans are presented in Appendix D to this report.
3.2 The table below provides a summary of the salient points relating to the history of the site. It is not the intention of this report to describe in detail all the changes that have occurred on or adjacent to the site. Significant former uses/operations are highlighted in bold text for ease of reference.
Date Site Surrounding land
Site comprises green fields Marfleet (village) from 100m to the south east. divided up by drainage Surrounding land predominantly comprises arable farmland. 1855 channels & fences/hedgerows. River Humber flows east c. 700m to the south. Footpath crosses the western Holderness Drain (presumably flows south) immediately side of the site. beyond eastern boundary within a cut channel. Marfleet Drain flows west then Marfleet Lane runs north – south immediately beyond western south through south eastern boundary. 1890 -94 corner. Development of Alexandra docks, prison & timber yard c. 1km Ponds shown in centre-south & to the south west. north east. Development of Marfleet to the south east & Alexandra Dock 1910 -11 to the south west.
No significant changes. Development of predominantly housing immediately beyond Holderness Drain to the west. Area named Sculcoates. 1928 -29 Further development of docks with extensive railway sidings & associated warehouses etc to the south. School with associated playing fields built immediately beyond 1938 -46 Entire site developed with semi- south western boundary. (aerial detached housing, gardens & photo) linear roads. Further housing developed immediately beyond south eastern boundary & to the east Further development of the surrounding area predominantly 1950 -51 with semi-detached housing. 1971 -77 School constructed to the east. 1984 No significant changes. 192 -93 Alexandra docks now disused. No significant changes. 1999 (aerial photo No significant changes. 2006 2018
3.3 The site lies within; a historical village which initially lay outside Hull. Historically Marfleet (meaning Pool/stream) comprised low lying farmland which frequently flooded. Several drains, including the Holderness Drain, were excavated and maintained in order to drain the land and improve farming yield.
3.4 Throughout the late 19th and early 20th century development of industry, specifically new docks along the Humber estuary (to the south), and the demand for labour led to a need for more housing.
3.5 Semi-detached and terraced housing across the site, and the surrounding area was constructed as part of the Preston Road (or East Hull) housing estate to house the citiy’s expanding population.
3.6 Construction was undertaken from the 1920s to the late 1940s by Hull City Council (then named the Hull Corporation).
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3.7 Hull, including Marfleet; and presumably this site, was the most severely damaged British city during the Second World War. About 90% of houses in the city were damaged or destroyed with only 6,000 of 91,000 remaining unscathed. Hull was the target of the first daylight aerial bombardment and the last piloted air raid on Britain.
3.8 Further details regarding the risk of unexploded ordnance are given in Section 4.3.
3.9 Whilst not shown on historical mapping approximately half of the site has been cleared of housing throughout 2018 as part of widespread regeneration in the surrounding area.
3.10 Throughout the post-war years and up until the modern day the Preston Road estate, including this site, fell into disrepute due to social issues. It is understood that social issues, rather than structural problems associated with the existing and recently demolished buildings, have led to the currently proposed redevelopment.
3.11 In July 2018 an art outreach project was undertaken by the Bankside Gallery to decorate several disused buildings with contemporary street art.
3.12 Historical maps show ditches crossing the site. These were likely excavated and maintained to drain the land and alleviate flooding; but filled-in and diverted during construction of the housing estate. The line of historical ditches is shown on Drawing 3039/3.
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4 ENVIRONMENTAL SETTING
4.1 General
4.1.1 Notes describing how the site’s environmental setting has been assessed are included in Appendix A to this report. Extracts from the response received from Landmark, and responses from the BGS are presented in Appendix E. These responses are summarised below, together with the findings of our own “desk study” investigation.
Issue Data reviewed Summary 1:50,000 BGS map (Sheet 81) Drift – Marine & Estuarine Alluvium (soft clay & silt) anticipated to c. 6m depth, over Glacial Till (stiff gravelly clay) BGS Memoir/Technical Report Solid – Flamborough Chalk Formation anticipated at >30m depth. Geology WA/VG/83/007 Strata dip – Gentle (<5°) to the east. BGS BHs TA13SW 484 to 486 No faults mapped beneath the site. Mining Coal Authority This site is located beyond the Coal Authority’s defined coalfields. Quarrying Historical OS plans No known quarries within 250m of the site’s boundary. Landfills No known landfills within 250m. The site lies in an area where less than 1% of homes are estimated to be above the action level. Therefore no radon Radon measures are required. Groundwater Source Protection Zone? An SPZ 3 is located immediately beyond the western boundary. Aquifer Unproductive strata (Drift); Principal Aquifer (Solid). Hydrogeology Envirocheck Report Groundwater abstractions? None within 1km of site. Public Health England Soil leaching potential – Non-aquifer – negligibly permeable. Environment Agency Nearest watercourse(s) – Holderness Drain 30m west. Flows south into River Humber (Humber Estuary) c. 1.4km to the south. Pollution incidents? 40m south west; Cat. 3 incident comprising suspended inert soils being discharged into Holderness Hydrology Drain. 1992. Several further incidents (discharge of effluent etc) have occurred in Holderness drain historically. Abstractions? None within 1km of site. Discharge consents? None of significance to site. The centre of the site lies in an area considered to be at low risk from surface water flooding. The entire site lies in an area at risk from flooding by rivers of sea (zone 3) but lies in an area benefitting from flood defences. Flood risk Environment Agency In accordance with Chapter 10 of the National Planning Policy Framework, a site-specific flood risk assessment is required for proposals of 1 hectare or greater in Flood Zone 1 and new development in Flood Zones 2 and 3.
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4.2 Ground Stability
4.2.1 Given that the site is underlain by chalk bedrock (of the Flamborough Chalk Formation), it was considered prudent to obtain a natural ground stability report from the BGS in order to check whether or not the chalk bedrock is considered prone to dissolution resulting in underground cavities that could lead to surface collapses and hollows.
4.2.2 The BGS report (copy included in Appendix E) provides an indication of the potential for natural ground instability to occur within, and within 50m, of a site. It is auto-generated from BGS’s GeoSure dataset. The Report assigns hazard levels for shrink-swell (clays), landslides (slope instability), soluble rocks (dissolution), compressible ground, collapsible deposits and running sand, but it does not include mining related subsidence. Hazards are graded on a scale from A to E (low to high), but Levels A & B are considered insignificant.
4.2.3 The BGS report for this site suggests potential hazards are:
• Clays that can swell when wet and shrink when dry causing the ground to rise and fall (Level C) • Very soft ground that might compress and progressively sink under the weight of a building (Level D) • Sand that can wash away or flow into holes or fissures due to the presence of water (Level D)
4.2.4 The potential for dissolution within the chalk bedrock is considered negligible. However, the BGS report does highlight the potential for instability which is likely caused by the presence of cohesive soft alluvium across the entire site.
4.2.5 The impact of running sands is discussed further in Section 7.8 (excavation stability); the impact of shrinkage and swell is discussed further in Sections 11.2 (geotechnical testing) and 13 (foundation recommendations).
4.3 UXO
4.3.1 As discussed in Section 3, the city of Hull was targeted and heavily bombed during the Second World War (1938 to 1945). The volume of explosives dropped across the area, including this site, along with the absence of development post-1945 increases the potential risk of unexploded ordnance and bombs being present beneath this site.
4.3.2 Therefore it was considered prudent to obtain an UXO/UXB desktop risk assessment from Planit International Ltd. The risk assessment is a separate document to this report and should be read in its entirety prior to development; recommendations within the risk assessment are likely to have a significant effect upon the design and construction methodology of the proposed development.
4.3.3 However, a brief summary of the findings of Planit’s risk assessment, which focuses on issues affecting Lithos’ intrusive investigation as well as implications for the proposed development, is included below:
• The Humber (c. 700m south) was lined with a variety of industries, and the docks were capable of taking freighters and merchant ships. Therefore, Kingston upon Hull Docks were a major target due to their importance in importing supplies for Britain’s war effort. • There is very good evidence that the site was directly and indirectly affected by large air-dropped bombs during WW2. • In total, the bombing campaign in Hull, including this site, resulted in 121 deaths. • There are no recorded abandoned bombs or unexploded bombs recorded which would affect the site.
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• Bomb census maps are comprehensive and show that the site was affected by large air-dropped high explosive bombs and that significant bomb damage was caused at several locations across the site • If a UXO related threat exists it would likely comprise either air-dropped German high explosive bombs or British anti-aircraft projectiles
4.3.4 A threat management strategy will be required prior to any intrusive engineering works. Lithos intrusive works were carried out under the supervision of a UXO specialist and all exploratory holes were scanned with a magnetometer for potential UXO prior to excavation/drilling.
5 GROUND INVESTIGATION DESIGN
5.1 Anticipated ground conditions & potential issues
5.1.1 Based on the data reviewed in Section 4 (Environmental Setting), anticipated ground conditions are expected to comprise:
Anticipated Remarks condition Veneer of made ground where plots/gardens have been demolished & turned over. Made ground Likely to be highly variable. Roads are understood to be constructed with a 500mm Sub-Base course of Ash & Clinker. Natural soils c. 6m of Estuarine Alluvial Deposits (soft silt & clay), over Glacial Till (gravelly clay). Bedrock Flamborough Chalk Formation at >30m depth. Possible perched groundwater in sand lenses within drift deposits. Groundwater Groundwater anticipated at depth within bedrock.
5.1.2 Based on the data above and that in Sections 2 (Site Description) and 3 (History), potential ground-related issues associated with this site are likely to include:
Type of issue Specific issue Remarks Potential on-site 1. Made ground/gardens 1. inorganic/organic contaminants contamination sources 2. Existing & former buildings 2. asbestos Potential off-site 1. - 1. - contamination sources 1. Result in over break/difficulty during 1. Relict buried obstructions excavations. Possible ‘hard spots’ resulting in Potential geotechnical 2. Soft/compressible ground differential settlement hazards 3. Running sands 2. Soft ground may require piled foundations 3. Instability of excavations during construction Other potential 1. - 1. - constraints
5.2 Preliminary conceptual site model
5.2.1 A preliminary conceptual site model, presented as Drawing 3039/5 in Appendix B, has been prepared after consideration of all the data presented in Sections 2 to 5.1 inclusive of this report.
5.2.2 An assessment of potential contaminants associated with the former uses has been undertaken with reference to CLR8.
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5.2.3 The site was a housing estate from c. 1930 until 2018. The nature of a housing estate (many small ‘parcels’ of land owned/occupied by many different individuals) means that a whole multitude of processes might have occurred in isolated spots across the site, i.e. vehicle maintenance with resultant oil spills etc may have taken place in one house; an asbestos shed may have been constructed and subsequently demolished and buried in a garden; a wooden fence may have been liberally painted with preservatives in another garden. Consequently, there is potential for localised areas of contamination.
5.2.4 A common source of contamination associated with early 20th century housing was the practice or mixing ash with garden soils; the majority of houses were constructed with wood/coal burning fires which produced a steady supply of ash. It was common practice to spread ash across garden areas as a soil improver; ash typically contains a number of PAHs leading to an elevation of PAH concentrations in otherwise essentially ‘clean’ soils.
5.2.5 Assessment of contaminants will be undertaken on a reasonable spread of indicator contaminants including:
• Asbestos • Inorganics (metals) • Organics (TPH & PAH)
5.2.6 Potential pollutant linkages are shown on the preliminary conceptual site model.
5.3 Ground investigation design & strategy
5.3.1 The preliminary conceptual site model was used as a basis for design of an appropriate ground investigation, the scope of which is summarised below:
5.3.2 As part of the investigation brief Lithos were required to determine the construction of existing roads across the site, i.e. the thickness of macadam surfacing and the thickness / make-up of sub-base materials.
Exploratory holes Purpose To determine the general nature of soils underlying the site, including the: • Nature, distribution and thickness of made ground About 80 trial pits • Nature, degree and extent of contamination • Proportion of undesirable elements e.g. biodegradable matter, foundations etc • Suitability of the ground for founding structures and highways Including trial pits To examine and describe foundations beneath existing buildings. To retrieve geotechnical data and samples from depth and; 10 cable percussion boreholes to install monitoring wells across the site in order to determine groundwater levels and assess flow direction About 40 dynamic With coring through existing roads in order to determine the construction of roads and sample boreholes their suitability for adoption.
5.3.3 Proposed exploratory hole locations were selected to provide a representative view of the strata beneath the site. Additional exploratory locations might be scheduled by the site engineer in light of the ground conditions actually encountered.
5.3.4 The number of representative samples taken will be reflective of the geological complexity actually encountered. However, in general about 3 samples will be taken from most trial pits.
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6 FIELDWORK
6.1 Objectives
6.1.1 The original investigation strategy is outlined in Section 5.3 above.
6.2 Exploratory hole location constraints
6.2.1 Seven trial pits were not advanced in the centre-west of the site due to ongoing demolition activities.
6.2.2 Dynamic sampling was the only practical means of investigation within the existing roads. It should be noted that dynamic sampling allows only a limited inspection of the ground (especially made ground with a significant proportion of coarse material). Furthermore, assessment of the strength of cohesive soils, via hand vane tests, is difficult due to disturbance caused by drilling.
6.3 Scope of works
6.3.1 Lithos’ ground investigation works were carried out under the supervision of a UXO specialist and all exploratory holes were scanned with a magnetometer for potential UXO prior to excavation/drilling.
6.3.2 Fieldwork was supervised by Lithos between the 25th October and the 14th November 2018 and comprised the exploratory holes listed below:
Technique Exploratory holes Final depth(s) Remarks 2.7m to 4.5m Trial pitting (machine dug) TPs 01 to 79 Vane tests in cohesive soils. (ave. 3.7m) Road cores with dynamic Road cores reinstated in accordance WSs 01 to 40 0.45m to 1.0m sample follow-on with Hull CC Spec. Cable percussive SPTs typically at 1.0m centres. BHs 01 to 10 20.1m to 25.1m boreholes Monitoring wells installed in all BHS.
6.3.3 Notes describing ground investigation techniques, in-situ testing and sampling are included in Appendix A to this report.
6.3.4 Exploratory hole logs are presented in Appendices F to H to this Report. These logs include details of the:
• Samples taken • Descriptions of the solid strata, and any groundwater encountered. • Results of the in-situ testing • The monitoring wells installed
6.3.5 Exploratory hole locations are shown on Drawing 3039/6 presented in Appendix B.
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7 GROUND CONDITIONS
7.1 General
7.1.1 A complete record of strata encountered beneath the proposed development site is given on the various exploratory hole records, presented in Appendices F to H.
7.1.2 The site can be divided into three areas based on ground conditions. These areas are shown on Drawing 3039/6 and are summarised below:
Site area General location Exploratory Holes (total) Area A Predominantly to the BHs 01 to 09 & TP’s 01, 03, 04, 17 to 34, 45, 47 to 73,000m2 (housing cleared) north east 52, 54, 57, 63, 65 to 73, 75 to 77 & 79 (62) B Predominantly to the BH01 & TP’s 2, 5 to 16, 44, 46, 53, 55, 56, 58 to 51,000m2 (houses remain) south west 62, 64. 74 & 78 (27) C (roads) In a ‘grid’ across the site WS’s 01 to 40 (40) 36,000m2
7.1.3 Area A comprises parts of the site where complete demolition of houses (including removal of floor slabs/foundations, turnover of made ground etc) had taken place.
7.1.4 Area B comprises parts of the site where demolition has yet to be completed; gardens and former residential dwellings still remain.
7.1.5 Area C comprises existing estate roads.
7.1.6 Typical ground conditions encountered at the site are described below in Sections 7.2 (made ground) and 7.5 (natural ground), with a summary provided in the table in Annex I.
7.2 Made ground
7.2.1 Made ground in Area C is discussed in Section 7.4 – Roads.
Area A (housing cleared)
7.2.2 The made ground on site is a heterogeneous mixture of materials and it is unlikely, even with a huge amount of sampling, that it could be accurately characterised. Made Ground within Area A can typically be categorized as one of two types:
• Made Ground Topsoil: Encountered within 18 of 62 exploratory holes to between 0.2m (TPs 28 & 30) and 0.45m (TP01) depth, average 0.3m, and comprising sandy CLAY/SILT with occasional gravel of brick, concrete and occasional pottery and mixed lithologies. Occasionally with fragments of plastic and wood/roots. Occasionally encountered as clayey slightly gravelly SAND. • Demolition Arisings: Encountered within 43 of 62 exploratory holes to between 0.15m (TP03) and 1.1m (TP 22) depth, average 0.5m, and comprising a heterogeneous mix of clayey, sandy GRAVEL of brick, concrete, mixed lithologies and occasional glass and pottery. Generally, with occasional fragments of plastic, metal and plant fragments. Occasionally encountered as clayey gravelly SAND or sandy gravelly CLAY.
7.2.3 In addition, TP03 encountered a thin bed of Sub-Base comprising buff, sandy gravel of limestone from 0.15m to 0.2m depth. The Sub-Base lay immediately under Demolition Arisings and immediately over Tidal Flat Deposits.
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7.2.4 TP45 encountered Cohesive Made Ground to a depth of 1.1m comprising CLAY, with gravel of predominantly brick and concrete and a low brick and concrete cobble content. TP45 was excavated across the footprint of a former drainage ditch (see Section 3), and it is tentatively inferred that this made ground was placed prior to/during construction of the Preston Road housing estate to fill in the drainage ditches. It might be that further ditches have been infilled with similar materials across the wider site.
7.2.5 It is apparent from the exploratory holes excavated in Area A that Demolition Arisings are present in, and close to, the footprints of former houses, whilst Made Ground Topsoil is present in the footprints of former gardens.
7.2.6 In total, Made Ground across Area A extends to an average depth of about 0.5m, with a maximum depth of 1.1m (TP22) and a minimum depth of 0.2m (TPs 28 & 30). Made Ground in Area A typically appears thicker beneath the footprints of former buildings and shallower in more distal garden areas.
Area B (houses remain)
7.2.7 Made ground within Area B can be classified as one of 4 main ‘types’ which are summarised below:
• Sub-Base: Encountered within BH10 & TPs 10, 11, 13, 16 & 60 to between 0.15m (TP11) & 0.8m (TP13) depth, average 0.4m, beneath hardstanding and comprising SAND or sandy GRAVEL of limestone. • Made Ground Topsoil: Encountered within 19 of 27 exploratory holes to between 0.2m (TPs 53, 55 & 56) and 0.45m (BH10) depth, average 0.3m, and comprising clayey SAND or sandy SILT/CLAY, with gravel of mixed lithologies and occasional pottery, brick and concrete and occasional fragments of plastic, glass and wood. • Cohesive Made Ground: Only encountered within 3 of the 89 exploratory holes excavated across the entire site (including two within Area B - TPs 5 & 8), comprising clay with occasional gravel of concrete and occasional fragments of plastic. • Granular Made Ground: Encountered within TPs 11, 44, 55 & 27 to between 0.35m (TP11) & 0.17 (TP55) depth, average 0.45m, and comprising clayey SAND, with gravel of brick and pottery.
7.2.8 Within TP55 Granular Made Ground comprised a very coarse soil - COBBLES of brick and concrete, with much sand and gravel of brick, concrete, limestone and sandstone and with fragments of metal, plastic and carpet.
7.2.9 It is apparent from excavations in Area B that the nature and distribution of made ground is more variable than in Area A (as demolition and turnover has not homogenised the ground yet), but the dominant type is Made Ground Topsoil. All together the maximum thickness of Made Ground in Area B ranges from 0.2m to 1.0m (TP05), with an average depth of 0.35m.
7.2.10 Whilst not encountered during this investigation, the possibility of asbestos sheeting (used as shuttering), and/or fragments of asbestos sheeting within the hardcore beneath hardstand slabs cannot be entirely discounted.
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7.3 Obstructions
Area A (housing cleared)
7.3.1 It is apparent from the historical plans that semi-detached residential dwellings were located across Area A. In addition, many buildings would have had associated areas of hardstand (patios, drives etc) and outbuildings (sheds etc); all of which would be expected to result in the presence of obstructions (relict floor slabs, foundations etc).
7.3.2 It is understood that the demolition specification (a copy of which has not been made available to Lithos) required removal of floor slabs and foundations, with turnover of ground to a depth of 1.0m within plot footprints and 0.5m in gardens in order to discover and remove any obstructions.
7.3.3 Several trial pits were excavated across the footprint of former buildings in order to search for any relict foundations/floor slabs associated with demolished buildings. Of the 62 exploratory holes advanced in Area A, only two encountered obstructions:
• TP36: Several cobble sized fragments of concrete from 0.0m to 0.2m depth in eastern end of the trial pit, comprising a relict and broken up floor slab. • TP54: A single sub-angular boulder (c. 0.4m diameter) excavated from 0.3m depth in Demolition Arisings comprising a large fragment of former foundation.
7.3.4 Given the above it is apparent that where former buildings have been demolished the significant obstructions appear to have been grubbed up and removed. However the possibility of more substantial obstructions cannot be entirely discounted.
Area B (houses remain)
7.3.5 Residential Dwellings remain across Area B. In addition, garden areas often include outbuildings and areas of hardstanding.
7.3.6 Three inspection Pits (IPs 01 to 03) were excavated in order to inspect foundations associated with the buildings. A photographic record and illustrative log is included on the inspection pit logs in Appendix F; but a brief summary is also included below:
7.3.7 All three inspection pits uncovered foundations associated with existing residential dwellings. The foundations extended to depths of between 500mm and 650mm, lying within the “desiccated crust” of firm to stiff Tidal Flat Deposits. The shear strength of natural soils at the base of the foundations was found to range from 78kPa to 88kPa.
7.3.8 The following exploratory holes encountered further obstructions:
Hole ID Depth (mbgl) Nature of obstruction TP08 0.0m to 0.1m Strong concrete hardstand within rear garden. TP13 0.0m to 0.14m Strong concrete hardstand within rear garden. TP14 0.0m to 0.28m Strong concrete relict foundation associated with brick built outbuilding. TP60 0.0m to 0.4m Medium strong concrete paving slabs over weak buff concrete. TP74 0.1m to 0.3m Strong grey concrete associated with relict floor slab/foundation.
7.3.9 Given the above it is apparent that some obstructions are present across Area B associated with the residential dwellings, outbuildings and areas of hardstanding. However it should be noted that the ongoing demolition works are grubbing up and removing any obstructions which are encountered.
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7.4 Roads (Area C)
7.4.1 A total of 9 roads cross the site; Flinton Grove, Foston Grove, Hilston Grove and Holmpton Grove all run roughly north to south; Brigham Grove, Wansford Grove, Cranswick Grove and St. Johns Grove all run east to west.
7.4.2 It is understood that Holmpton Grove & St. Johns Grove may be retained, but other roads which cross the site are likely to be removed.
7.4.3 A total of 40 exploratory holes were advanced through roads across the site. Exploratory holes were spaced at 40m intervals on roads which are being retained and on 80m intervals on roads which are to be removed. Exploratory holes, roads are summarised in the table below:
Road Name Exploratory holes Intended future of road Brigham Grove WSs 28, 29, 32 & 33 Wansford Grove WSs 18, 36 & 37 Grubbed up & removed Cranswick Grove WS 40 St. Johns Grove WSs 05 to 14 Retained Foston Grove WSs 15 to 17, 19 & 20 Harpham Grove WSs 23 to 27 Grubbed up & removed Hilston Grove WSs 01 to 04 Holmpton Grove WSs 30, 31, 34, 35, 38 & 39 Retained Concrete paths (unnamed) WSs 21 & 22 Grubbed up & removed
7.4.4 Road cores typically encountered the following succession:
• Surface Course: Encountered in all WSs except WSs 21 & 22; typically 40mm thick comprising black Macadam. • Base Course: Encountered in all WSs except WSs 21 & 22, typically to 150mm depth (max 180mm WSs 04 & 27; min 120mm WS15), and comprising weak black Macadam which typically breaks up when excavated. • Sub-Base: Encountered in all WSs except WSs 21 & 22, typically to 330mm depth (max 450mm WS02; min 250mm), and comprising both/either: o Sub-Base – Brick: sandy gravel of predominantly brick and/or o Sub-Base – Chalk: clayey gravel of predominantly chalk • Ash & Clinker: Encountered sporadically within 27 of the 40 WSs to depths of between 30mm (WSs 21 & 22) and 60mm (WS02), and comprising ashy sand with gravel of clinker, occasional pottery and rare glass.
7.4.5 The Sub-Base beneath roads comprises crushed brick or crushed chalk. Generally, the crushed brick overlays the crushed chalk. However, in some holes this is reversed, or one of the Sub-Base types is absent.
7.4.6 Road construction consistently overlies the “desiccated crust” of firm natural clays (Tidal Flat Deposits).
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7.5 Natural ground
7.5.1 Natural ground was encountered in the majority of the exploratory holes; in Areas A, B and C; and typically comprised the following succession:
• Tidal Flat Deposits: Encountered in all exploratory holes, except WS01, immediately beneath made ground, and comprising brown clays and occasionally silts/sandy clays. The composition of the Tidal Flat Deposits is described further below. • Cohesive Glacial Deposits (Till): Encountered within all 10 cable percussion boreholes from depths of between 6.1m (Bs 6 & 7) and 7.6m (BH01), average 6.7m; typically comprising clay with gravel of predominantly chalk and flint. • Granular Glacial Deposits: Encountered within all 10 cable percussion boreholes from between 6.3m (BH07) and 23.0m (BH04) depth; comprising fine to medium sand which is occasionally clayey.
7.5.2 The Granular Glacial Deposits encountered at shallow depths typically occurred in thin beds (generally c. 200mm). Whilst deeper Granular Glacial Deposits are present in thicker beds.
7.5.3 Thin beds of pseudo-fibrous Peat were encountered in BHs 04 & 06 at 6.7m and 6.1m depth respectively; maximum thickness of 200mm (BH04). Peat was encountered at the boundary between Tidal Flat Deposits (above) and Cohesive Glacial Deposits (below).
7.5.4 The Tidal Flat Deposits can be split into three ‘sub-groups’ based on physical properties (consistency, triaxial test results, hand vane test results & SPTs). These sub groups have been referenced on the various exploratory hole logs, summary tables and relevant sections of this report and are expanded on below:
• Desiccated Layer: Generally encountered beneath made ground to depths of between 1.0m (TP08) & 1.7m (TPs 5, 13, 15 & 66), average 1.3m, although occasionally absent. This layer is very stiff to stiff consistency (occasionally firm), of high strength, and generally has closely spaced fissures. • Partially Desiccated Layer: Generally encountered from the base of the Desiccated Layer (although occasionally from the base of made ground) to depths of between 1.3m (TP51) and 3.0m (TP11); average 2.3m. This layer is of firm consistency and medium strength; the consistency tends to reduce to soft and strength reduces to low towards the base of this bed. • Lower Saturated Layer: encountered from the base of the Partially Desiccated Layer and extending down to the underlying Cohesive Glacial Deposits. This bed is of soft to very soft consistency and very low to extremely low strength. This layer is typically dark grey in colour with occasional gravel sized fragments of shell.
7.5.5 Generally it is expected that soils become stronger with depth beneath a site. However, Tidal Flat Deposits beneath this area of Hull display the opposite trend with a reduction in consistency/strength with depth.
7.5.6 The shallower Tidal Flat Deposits are desiccated, and reduction in water content has increased the in-situ strength of the soil. However, with increased depth the action of evaporation and/or plant and tree roots reduces; the soil has remained ‘wet’ and the in- situ strength remains very low.
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7.6 Visual & olfactory evidence of organic contamination
7.6.1 Exploratory locations where evidence of significant organic contamination was noted are summarised below:
Site area Hole ID Material Depth (m) Observation B TP59 Made Ground Topsoil 0.0m to 0.3m Fragments of possible ACM cement sheeting A TP69 Demolition Arisings 0.0m to 0.3m Fragments of unknown blue material
7.6.2 Selected samples of potentially contaminated materials were scheduled for chemical testing to determine the nature and extent of any contamination; see Section 0.
7.7 Groundwater
7.7.1 During the intrusive investigation the following groundwater inflows were encountered:
Hole ID Strata Depth (mbgl) Nature of groundwater IP03 Concrete foundation 0.3m Seepage of groundwater from concrete foundation. TP37 1.3m Seepage of groundwater from trial pit walls. Tidal Flat Deposits TP38 1.2m Seepage of groundwater from trial pit walls. TP44 Granular Made Ground 0.35m Seepage of groundwater from base of made ground. TP47 Tidal Flat Deposits 1.0m Seepage of groundwater from trial pit walls. TP50 Granular Made Ground 0.30m Seepage of groundwater from base of made ground. TP70 Tidal Flat Deposits 1.20m Seepage of groundwater from trial pit walls. TP75 Demolition Arisings 0.7m Seepage of groundwater from base of made ground. BH01 20.5m Water strike. Rose to 9.1m in 20 minutes BH02 18.9m Water strike. Rose to 11.5m in 20 minutes. BH03 18.5m Water strike. Rose to 9.0m in 20 minutes. 18.0m Water strike. Rose to 12.0m in 20 minutes. BH04 20.0m Water Strike. Rose to 8.0m in 60 minutes. BH05 Granular Glacial Deposits 18.0m Water strike. Rose to 11.0m in 20 minutes. BH06 20.0m Water strike. Rose to 13.7m in 20 minutes. BH07 20.2m Water strike. Rose to 9.1m in 20 minutes. BH08 18.5m Water strike. Rose to 17.0m in 20 minutes. BH09 19.2m Water strike. Rose to 12.2m in 20 minutes. BH10 19.6m Water strike. Rose to 14.5m in 20 minutes.
7.7.2 It is apparent from the observations above that groundwater encountered within shallow excavations (trial pits up to c. 4m deep) generally comprises relatively minor seepages. More significant groundwater strikes were only encountered within deeper boreholes where granular glacial deposits were encountered.
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7.7.3 To date groundwater levels within the monitoring wells have only been recorded once (30th November 2018); monitoring results are presented in the table below:
Hole ID Response zone (depth range & strata) Groundwater body Water level m bgl BH01 3.23 BH02 2.0 to 6.0m (Tidal Flat Deposits) 2.73 BH03 1.05 BH04 2.0 to 7.0m (Tidal Flat Deposits and Peat) 0.34 BH05 2.0 to 6.0m (Tidal Flat Deposits) 2.47 Perched shallow BH06 2.0 to 6.5m (Tidal Flat Deposits and Peat) 0.84 BH07 1.19 BH08 0.75 2.0 to 6.0m (Tidal Flat Deposits) BH09 0.69 BH10 3.23
7.8 Stability
7.8.1 Stability of excavations within both made and natural ground was generally good.
7.9 Revised conceptual ground model (ground conditions)
7.9.1 The Preliminary Conceptual Site Model has been revised in light of data obtained during the ground investigation, most notably with respect to:
• The nature and distribution of made ground, including the presence of significant buried obstructions • The strength, nature and depth of underlying natural strata • The nature and distribution of contamination (based on visual/olfactory evidence only)
7.9.2 The revised Conceptual Site Model is presented in Appendix B, as Drawing 3039/7.
7.9.3 Further refinement of the Conceptual Site Model is presented in Section 9.2, where the results of laboratory testing for contaminants have been considered.
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8 CONTAMINATION (ANALYSIS)
8.1 General
8.1.1 The site has been formerly been a housing estate; with semi-detached residential dwellings and associated gardens, roads and POS.
8.1.2 The site’s former usage is considered unlikely to have given rise to any significant ground contamination. However, a multitude of processes might have occurred in isolated spots across the site (e.g. vehicle maintenance with resultant oil spills etc, demolition of an asbestos shed with subsequent burial, application of preservatives to wooden fences etc). Consequently, there is potential for localised areas of contamination.
8.1.3 Furthermore, made ground and Made Ground Topsoil have been encountered around remaining houses and Demolition Arisings are present around the footprints of demolished plots. Samples of made ground have been recovered to determine the presence of any contamination.
8.1.4 An assessment of potential contaminants associated with the former uses has been undertaken; see Section 5.2.
8.1.5 In the context of risks to human health associated with residential redevelopment, the Tier 1 Soil Screening Values referenced in this report have been derived via the CLEA default conceptual site model (CSM) used for generating SGVs, but amended, where appropriate, to be more specific to redevelopment within the planning process.
8.1.6 Where available, Category 4 Screening Levels (C4SL) have also been referenced.
8.1.7 Generic Note 04 in Appendix A provides further details with respect to current guidance and the interpretation of analytical data.
8.2 Testing scheduled
8.2.1 Based on the above assessment, Lithos submitted a test schedule (summarised in the table below) to a UKAS accredited laboratory. Account has also been taken of visual and olfactory evidence recorded during the ground investigation.
No. of Type of sample Determinands samples
Made ground: pH, water soluble boron, and total metals (arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium and zinc) & • Demolition Arisings Asbestos ID • Cohesive Made Ground 21 TOC, Speciated Polycyclic Aromatic Hydrocarbons (PAH), Banded • Granular Made Ground Total Petroleum Hydrocarbons (TPH) • Sub-Base Water soluble sulphate, chloride, nitrate and magnesium pH, water soluble boron, and total metals (arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium and zinc) & Made Ground Topsoil 9 Asbestos ID TOC, Speciated Polycyclic Aromatic Hydrocarbons (PAH), Banded Total Petroleum Hydrocarbons (TPH) pH, water soluble boron, and total metals (arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium and zinc) & Road materials: Asbestos ID 10 • Ash & Clinker Calorific Value (CV) TOC, Speciated Polycyclic Aromatic Hydrocarbons (PAH), Banded Total Petroleum Hydrocarbons (TPH)
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8.3 Soil contamination results
8.3.1 The soil contamination test results are summarised in the tables in Annex II, and test certificates as received from the laboratory are presented in Appendix I.
Inorganic determinands (general)
8.3.2 Of the 40 samples of made ground analysed for inorganic parameters, 19 can be classified as uncontaminated and 21 could be classified as contaminated.
8.3.3 These samples have been classified by comparison with Tier 1 Soil Screening Values for an end use including domestic gardens and any area where plants are to be grown (the most sensitive of the proposed end-uses).
8.3.4 The most common contaminants are arsenic, copper, lead and zinc.
Inorganic determinands (Demolition Arisings & Made Ground Topsoil)
8.3.5 12 samples which could be classified as contaminated have been taken from Demolition Arisings (5) and Made Ground Topsoil (7); all from Areas A & B.
8.3.6 Statistical analysis of 21 results has been carried out in general accordance with the methods outlined in “Guidance on Comparing Soil Contamination Data with a Critical Concentration”, CIEH/CL:AIRE (2008) (see comments in Appendix A, Contamination Testing) and the results are summarised below:
US95 values for contaminants that have yielded one or more Tier 1 No. of exceedances for a given made ground type Stratum samples Arsenic Lead Zinc (37) (200) (200) Demolition Arisings 12 22 177 127 (excluding 2 outliers) Made Ground Topsoil 9 29 (excluding 1 170 (excluding 1 167 (excluding 1 outlier) outliers) outlier)
8.3.7 Where there is 95% confidence or greater that the true mean concentration of a given contaminant within a particular soil type is less than the Tier 1 value, it can be concluded that the contaminant does not pose a significant risk to human health.
8.3.8 Two samples of the Demolition Arisings failed the outlier test for Zinc (samples TP21 at 0.1m & TP51 at 0.3m). Excluding the two outliers the remaining samples of Demolition Arisings give a mean value which falls below Lithos’ Tier 1 screening value of 200mg/kg.
8.3.9 Two Made Ground Topsoil samples failed the outlier test (TP30 at 0.1m for Arsenic, with a value of 80mg/kg; and TP09 at 0.2m for lead, with a value of 540mg/kg and zinc, with a value of 790mg/kg). Excluding the outliers the Made Ground Topsoil is not considered to be contaminated with inorganic contaminants.
8.3.10 Made Ground Topsoil and Demolition Arisings are highly heterogeneous and are likely to contain a very wide range of fragments, i.e. fragments of metal, plastic and possibly fine fragments of paint etc. The occasional outliers encountered (4 of 21 samples analysed) are most likely to be related to the presence of small, isolated fragments of inorganic material.
8.3.11 Lithos’ Tier 1 values have been derived assuming that no clean cover will be placed in areas of gardens and POS; in fact, a nominal 300mm of clean cover is anticipated over Demolition Arisings which will act to reduce the pathway between sources and receptors.
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Inorganic determinands (Other Made Ground)
8.3.12 Seven samples of Ash & Clinker (taken from Area C, below roads), and two samples of Cohesive Made Ground (from Area A) could be considered to be contaminated.
8.3.13 The Ash & Clinker has yielded consistently elevated concentrations of arsenic, copper, lead and zinc. Whilst the Cohesive Made Ground has yielded concentrations of arsenic, copper, zinc and levels of lead in excess of 5x Lithos’ Tier 1 value.
8.3.14 Given the consistently elevated concentrations of inorganic contaminants in the Ash & Clinker, statistical analysis would not demonstrate that as a whole the material fell beneath Lithos’ Tier 1 values; and, given the low number of samples of Cohesive Made Ground statistical analysis is not possible on this made ground type.
8.3.15 Consequently, both the Cohesive Made Ground and Ash & Clinker made ground types should considered contaminated.
Calorific value
8.3.16 The calorific value of 10 samples of Ash & Clinker (from beneath roads) have yielded an average CV of 2.8 MJ/kg (maximum 6.4 in WS38 at 0.4m). Materials whose CVs exceed 10MJ/kg are almost certainly combustible, while those with values below 2MJ/kg are unlikely to burn. Therefore the Ash & Clinker is considered to be at the ‘lower end’ of combustibility.
Asbestos
8.3.17 A single sample of Made ground Topsoil (TP59 at 0.1m in Area B) returned a positive Asbestos ID screen. None of the other 39 samples screened returned a positive asbestos ID.
8.3.18 Further analysis of the Made Ground Topsoil from TP59 was instructed and returned a value of 4.9% chrysotile fibres by mass of soil sample.
8.3.19 As discussed in Section 7.6, the Made Ground Topsoil in TP59 included a fragment of cement sheeting.
8.3.20 Lithos requested further details with regards to the results of asbestos testing on the sample; the lab noted that: “there were no fibres detected within the soil matrix only a large piece of cement which was found during the visual inspection”.
8.3.21 Testing and correspondence with the laboratory has confirmed that the fragments of cement sheeting recorded in TP59 do indeed contain asbestos. However, the soil matrix does not contain fibres of bundles of loose asbestos.
Organic determinands
8.3.22 This site is brownfield, but no visual or olfactory evidence of organic contamination has been encountered during Lithos’ investigation and no clear sources of organic contaminants have been identified on the CSM. Therefore the Tier 1 values used in this report assume a residential with gardens end-use with no clean soil cover being placed in gardens/landscaped areas (Lithos Scenario A); although in fact a nominal 300mm of topsoil is anticipated.
8.3.23 Lithos have used the CLEA model to derive risk-based screening values for hydrocarbons, in accordance with the methodology detailed by the TPHCWG, and reviewed by a UK workshop of experts with respect to UK adoption of the method.
8.3.24 However, these screening values assume a Soil Organic Matter (SOM) of 6% (equivalent to a TOC of 3.5%). Many organic contaminants are more mobile when the SOM is lower, and consequently comparison of soil results with lower screening values may be required.
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8.3.25 In order to check the validity of Lithos’ Tier 1 Soil Screening Values, the average TOC for each common fill type (beyond any areas of obvious hydrocarbon impact) have been determined.
Typical Soil type Comparison of soil results with revised screening value necessary? TOC (%) Ash & Clinker 14% No. Cohesive Made Ground 15% No. Demolition Arisings 3% Yes; revised screening values adopted. Granular Made Ground 2% Yes; revised screening values adopted. Made Ground Topsoil 4.5% No. Sub-Base 1% Yes; revised screening values adopted.
Hydrocarbons (TPH & PAH)
8.3.26 Given the absence of visual/olfactory evidence of any hydrocarbon contamination, only a simple banded TPH (cf full speciation) was initially scheduled on 40 samples.
Areas A & B
8.3.27 Examination of the results (see table in Annex II) shows that soils across Areas A & B consistently yield slightly elevated concentrations of gasoline range (light) TPHs.
8.3.28 Given the relatively minor results received and the consistency of the results it is unlikely that there is actually a hydrocarbon spill present as:
• A spill would be expected to result in a ‘hot-spot’; a relatively localised area of high TPH results. • A hydrocarbon spill would likely result in visual and olfactory evidence which would have been recorded during Lithos’ investigation.
8.3.29 TPH can be associated with a variety of sources and elevated TPH concentrations do not automatically infer a petroleum product is present; indeed the absence of petroleum products on this site is reflected in the preliminary conceptual model. TPH analysis will detect most hydrocarbons and is not restricted to those detailed within the TPHCWG reports.
8.3.30 Lithos’ experience on similar sites has shown that the TPH screen scheduled uses a very powerful solvent which extracts hydrocarbons from plastics, coal, macadam, organic materials and ash/clinker as well as from hydrocarbon sources.
8.3.31 Examination of desk study portion of this report and the exploratory hole logs suggests that the following ‘alternative’ sources of hydrocarbons are also present across this site:
• Made Ground Topsoil, Cohesive Made Ground, Granular Made Ground and the Demolition arisings contain: o Plastics; o Organic matter (plants, wood, roots etc); o Occasional coal and clinker; all of which contain hydrocarbons which the TPH screen could detect. • The underlying natural soils at this site comprise Tidal Flat Deposits; soils rich in organic matter, which could contain hydrocarbons that the TPH screen could detect. • Historically fire-ash has been used as a soil improver in residential gardens; in the 1930s/40s every house would have been heated by a coal fire and ash from the fire was often spread across gardens; fire-ash contains hydrocarbons which might be detected by the TPH screen.
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8.3.32 In order to further reduce uncertainty, Lithos made an enquiries of the chemical laboratory who suggested that “the elevated results you are observing are most likely due to the presence of naturally occurring compounds and clinker/ash/coal. From the chromatograms reviewed the hydrocarbons within the early elevated concentrations in the VPH (GRO) range do not illustrate a pattern which is consistent with a petrogenic contaminant”. The laboratory also noted that many samples contained roots and plastic; potential hydrocarbon sources detected during the TPH screen.
8.3.33 The response from the laboratory is included in Appendix I.
8.3.34 Whilst not necessarily associated with a petroleum product, the significance of these hydrocarbons, with respect to health, should still be assessed. Providing no other sources are present on site (solvents, degreasers etc), it can be assumed that the most problematic compounds detected within the banded TPH screen are polycyclic aromatic hydrocarbons (PAHs).
8.3.35 The significance of PAHs can be determined by considering indicator compounds. In most cases, benzo(a)pyrene (B(a)P) is adopted as an indicator (due to the wealth of toxicological data available) and has been used by various authoritative bodies to assess the carcinogenic risk of PAHs in food.
8.3.36 Whilst classed as a PAH, naphthalene is more volatile and mobile in the environment than other PAHs. As such the significance of naphthalene cannot be considered within the surrogate marker approach. Consequently, naphthalene has been considered individually against Lithos’ Tier 1 Value.
8.3.37 None of the samples tested exceeded the Tier 1 value for naphthalene.
8.3.38 The sample profiles here are sufficiently similar to the toxicity study adopted for the C4SL assessment, but B(a)P concentrations exceed Lithos’ Tier 1 Value.
8.3.39 Of the 32 samples of Made Ground in Areas A & B tested for organic contaminants, 6 returned values of B(a)P in excess of Lithos’ Tier 1 screening value.
8.3.40 Statistical analysis of exceedances of B(a)P is presented in the table below:
US95 values for contaminants that have yielded one or No. of Area Stratum more Tier 1 exceedances for a given made ground type samples Benzo(a)Pyrene A & B Demolition Arisings 12 2.9 (outlier present) A & B Made Ground Topsoil 9 2.5 (outlier present) B Sub-Base 8 1.6
8.3.41 Where there is 95% confidence or greater that the true mean concentration of a given contaminant within a particular soil type is less than the Tier 1 value, it can be concluded that the contaminant does not pose a significant risk to human health. This is the case for the Benzo(a)Pyrene within Sub-Base at this site.
8.3.42 A single sample failed the outlier test for B(a)P in the Demolition Arisings (TP51 at 0.3m) and a separate sample failed the outlier test for B(a)P in the Made Ground Topsoil (TP05 at 0.3m). Disregarding these outliers the mean concentration of B(a)P in both Demolition Arisings and Made Ground Topsoil fall beneath the respective Tier 1 values and these made ground types are not considered to be contaminated.
8.3.43 Given the limited number of samples (two) it was not possible to carry out meaningful statistical analysis of the B(a)P exceedance in the Cohesive Made Ground (typically a minimum of 6 samples are required).
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8.3.44 Given the lines of evidence discussed earlier in this Section, it is unlikely that the B(a)P outliers are the result of hydrocarbon contamination. Examination of the exploratory hole logs shows that TP45 (Demolition Arisings) contained occasional fragments of coal and TP51 (Made Ground Topsoil) contained occasional fragments of coal and clinker.
8.3.45 Both coal and ash and/or clinker are commonly associated with high PAHs which are a result of the chemical make-up of coal / the result of a residual product of combustion respectively. Given the inclusion of coal and clinker in these samples it is considered that the lines of evidence point to a source of PAHs which is not associated with organic hydrocarbon spill contamination. On the balance of likelihood, the same lines of evidence can be applied to Made Ground Topsoil encountered in TP05 at 0.3m depth.
8.3.46 PAHs associated with the above sources are immobile; therefore the presence of B(a)P outliers in the Cohesive Made Ground, Made Ground Topsoil and Demolition Arisings are not considered a significant risk to the key receptors (site workers and end-users).
Area C (Roads)
8.3.47 A total of 7 samples of Ash & Clinker from beneath existing roads were tested for TOC and PAHs. The typical TOC of Ash & Clinker was 12% so revision to Lithos’ Tier 1 values is not required (see Section 8.3.25).
8.3.48 The B(a)P results returned varied from 0.8mg/kg to 310 mg/kg with an average of result of 92mg/kg. A single sample (WS34 at 0.35m) returned a result for naphthalene in excess of Lithos’ Tier 1 screening value.
8.3.49 As with the made ground in Areas A & B, no clear hydrocarbon source has been identified in the CSM, and no visual or olfactory evidence of contamination was noted during the investigation. Furthermore, the Ash & Clinker is isolated beneath impermeable macadam surfaces, and any hydrocarbon spills on road surfaces would not be expected to permeate through madacam courses into the underlying Ash & Clinker.
8.3.50 However, Ash & Clinker is frequently associated with high PAH concentrations due to the presence of residual products of combustion. In addition, it is possible that some macadam might have been incorporated into the samples which have been tested (introduced whilst drilling through the road). Macadam partially comprises complex hydrocarbons, including PAHs.
8.3.51 These residual compounds, and hydrocarbons bound up within the macadam, are immobile and therefore breakage of the pollutant linkage be placement of a suitable cover is considered appropriate.
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9 CONTAMINATION (QUALITATIVE RISK ASSESSMENT & REMEDIATION)
9.1 Summary of significant contamination
9.1.1 Made ground across the site contains a number of materials which are considered undesirable as near-surface materials such as plastic, glass, metal and pottery.
Area A (housing cleared)
9.1.2 A veneer of made ground comprising Demolition Arisings and Made Ground Topsoil is present across Area A. The Made Ground in Area A has been found not to contain contamination at levels which are considered a significant hazard to the key receptors (end users).
9.1.3 Cohesive Made Ground (only encountered in TP45) contains a number of inorganic compounds in excess of Lithos’ Tier 1 values and is considered to be contaminated.
Area B (houses remain)
9.1.4 A veneer of made ground is present across Area B which comprises Made Ground Topsoil with some Hardstand, Sub-Base, Cohesive Made Ground and Granular Made Ground located in garden areas.
9.1.5 A single sample of Made Ground Topsoil contains fragments of asbestos cement sheeting, although the soil matrix has been found to not contain fibres/bundles.
Area C (Roads)
9.1.6 Ash & Clinker beneath the existing roads is contaminated with a number of inorganic contaminants and generally high PAHs.
9.2 Revised conceptual ground model (contamination)
9.2.1 The Preliminary Conceptual Site Model has been amended in light of data obtained during the ground investigation, most notably with respect to the distribution of made ground and contaminants.
9.2.2 A revised Conceptual Site Model is presented as Drawing 3039/7 in Appendix B. The Model includes the contaminants described in Section 9.1 above, and potential pollutant linkages (summarised below in Section 9.3) to receptors.
9.3 Environmental setting & end use
9.3.1 It is apparent from Section 9.1 above, that only limited contamination has been identified to date in the soils beneath this site. In order to assess the significance of this contamination, consideration must be given to the site’s environmental setting and the proposed end use.
9.3.2 The underlying Flamborough Chalk bedrock is classified as a Principal aquifer; however the chalk is isolated beneath about 30m of cohesive soils which are classed as an unproductive aquifer. The nearest surface watercourse is the Holderness Drain which flows south just beyond the western boundary. Therefore, the site’s environmental setting is considered to be moderate sensitivity.
9.3.3 With respect to human health, the proposed end use (residential) is considered sensitive.
9.3.4 Transient risks to construction workers can be addressed by the adoption of appropriate health and safety measures, see Section 13.6.
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9.4 Pollutant linkages
9.4.1 In terms of a proposed redevelopment of this site, plausible pollutant linkages can be summarised as follows.
Contaminants
9.4.2 Contaminants have been summarised in Section 9.1 above.
Pathways
9.4.3 Potential contaminant pathways include:
• Ingestion • Dermal contact • Inhalation of contaminated particulates
Receptors
9.4.4 Potential contaminant receptors include:
• End users of the site (residents)
9.4.5 It can be concluded that there are plausible pathways between the soil contaminants summarised in Section 9.1 above and potential receptors i.e. end users. Consequently, some remediation will be required; either treatment/removal of the contaminant, or “breakage” of the pathway.
9.5 Potential remediation options
General
9.5.1 Given the constraints discussed in Section 6.2 (remaining houses in Area B), a simple post- demolition trial pit investigation will be required before definitive recommendations are provided. However, at this stage it is considered unlikely that anything more than placement of soil cover in garden areas will be required.
9.5.2 Approval of the recommendations given below should be sought from the appropriate regulatory authorities prior to commencement of site redevelopment.
Combustibility
9.5.3 The Ash & Clinker beneath existing highways (Area C) yielded an average CV of 3.9MJ/kg. This is at the lower end of the range where the potential for combustion exists and it is not considered a significant hazard, especially since beds of Ash & Clinker are typically less than 300mm thick.
9.5.4 The Ash & Clinker is considered suitable to remain beneath existing roads (where roads are being retained) of redistributed beneath proposed roads and areas of hardstand during construction (Local Authority Building Control and Warranty Provider approval should be sought).
9.5.5 Services: utility trenches (especially those carrying potential heat sources e.g. electric cables) should be cut oversize and backfilled with clean, inert material. This applies to any utility trenches that run beneath estate roads or extend under houses. It is strongly recommended that further advice be sought from all statutory service bodies with respect to the ground conditions within which they will lay services.
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9.5.6 Highways/hardstand/floor slabs should provide suitable insulation from heat sources to prevent combustion of the Ash & Clinker. In addition, this will remove the pathway between key receptors and inorganic contaminants within the Ash & Clinker.
9.5.7 As further mitigation against the risk of spontaneous combustion, the Ash & Clinker could be excavated, replaced in approximate 300mm thick layers, wetted and subjected to nominal compaction, comprising at least 2 passes with a towed vibratory roller of at least 2,900 kg per metre width. Compaction will help to prevent the material drying out and reduce the ingress of oxygen.
Asbestos
9.5.8 CL:AIRE has published a Joint Industry Working Group (JIWG) guidance1 document with the support of the Health & Safety Executive which provides an explanation of how legal requirements of the Control of Asbestos Regulations 2012 have been interpreted to be more directly applicable to the risks associated with asbestos contaminated soil and construction & demolition materials.
9.5.9 A single sample of Made Ground Topsoil has been found to contain fragments of asbestos cement sheeting. However the soil matrix does not contain fibres or bundles.
9.5.10 Samples of soil and/or construction & demolition material recovered from brownfield sites may exhibit a wide range of concentrations of asbestos contamination. Due consideration should therefore be given to the interpretation of any ‘trace’ concentrations in the wider context of the site. Guidance prepared by the JIWG asbestos suggests that judgements on the nature, degree and significance of contamination present should not be made on the basis of individual samples alone.
9.5.11 Any fragments of asbestos cement sheeting encountered during the excavation works, should be gathered by hand and placed in double sealed bags. Personnel involved in this activity must be equipped with an appropriate respirator (i.e. a FFP3 or better), in addition to their “standard” PPE. The bags of asbestos waste should be placed in a sealed skip for off-site disposal at a suitably licensed landfill site; such material will be classified as hazardous waste.
9.5.12 If asbestos cement sheeting is picked from the Made Ground Topsoil, then the soil could be considered to be free of asbestos. In addition the anticipated nominal 300mm of clean topsoil cover will afford additional protection to end-users.
9.5.13 Provided soils are kept damp the risk of airborne fibre release, even during disturbance associated with excavation, should be negligible, and certainly below the control limit (as set by the Control of Asbestos Regulations 2012) of 0.1 f/cm3 airborne fibres averaged over a 4-hour period.
9.5.14 In our experience, damp soils do not allow the release of asbestos fibres, even from soils that contain concentrations in excess of the hazardous waste threshold (0.1%).
9.5.15 There may be transient risks during the excavation of made ground soils. Exposure to asbestos of personnel involved in these excavation works is considered likely to be sporadic and of low intensity (provided soils are kept damp). Therefore in accordance with Regulation 3(2) of the Control of Asbestos Regulations (2012), exemption from Regulations: 9 (notification of work with asbestos); 18(1)(a) (asbestos areas); and 22 (health records and medical surveillance) should apply, provided it is ‘clear from a suitable and sufficient risk assessment that the control limit of 0.1 f/cm3 airborne fibres averaged over a 4-hour period will not be exceeded’.
1 Control of Asbestos Regulations 2012: Interpretation for Managing and Working with Asbestos in Soil and Construction & Demolition materials: Industry Guidance
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9.5.16 Nonetheless, risks must be mitigated by appropriate measures (principally damping down), working procedures, and PPE. Method Statements and Risk Assessments should be prepared by the Contractor, and then be reviewed by the Client and Lithos.
9.5.17 It should be noted that ACMs were commonly used as shuttering beneath concrete slabs, and to form ducts, and it is important that this is kept in mind when breaking through concrete slabs.
9.5.18 See also comments in the ‘Waste Classification’ Section below.
Inorganic contamination (Made Ground Topsoil, Demolition Arisings, Granular Made Ground & Sub-Base)
9.5.19 The made ground has been found to be essentially “clean” (i.e. it has not yielded elevated concentrations of any contaminants) but does include “unsuitable” materials (e.g. they contain a significant proportion e.g. demolition rubble, brick and locally tin, rope, timber and plastic etc.).
9.5.20 Therefore, where residual made ground remains beneath garden and landscaped areas (i.e. not beneath hardstanding) a 300mm thick surface cover of “clean” soil is recommended. This thickness is in accordance with NHBC Standards, Chapter 9.2.
Inorganic Contamination (Cohesive Made Ground & Ash & Clinker)
9.5.21 Ash & Clinker is present beneath existing roads across the site (Area C). Cohesive Made ground was only encountered 3 of the 89 exploratory holes excavated across the entire site, and significant contamination was only reported in one of these - TP45 (Area A).
9.5.22 Both the Cohesive Made Ground and the Ash & Clinker have yielded elevated concentrations of a number of metals. Therefore, where Cohesive Made Ground/Ash & Clinker remains beneath garden and landscaped areas (i.e. not beneath hardstanding) a 600mm thick surface cover of “clean” soil comprising 500mm subsoil and 100mm topsoil is recommended. This cover will break potential pollutant linkages between the contaminated made ground and future end-users.
9.5.23 Alternatively, these made ground types are considered suitable for redistribution beneath concrete oversite or areas of hardstanding, where they would be satisfactorily isolated from end users.
Organic contamination
9.5.24 No areas of gross organic contamination were encountered during the site works. However, localised areas of more onerous contamination than that identified to date may be present on site.
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9.6 Summary of potential pollutant linkages & mitigation
9.6.1 In terms of the proposed redevelopment plausible pollutant linkages, and feasible remediation options, can be summarised as follows:
Plausible pollutant linkage? Receptors Pathways Contaminants (and remediation options where required) Consumption of Isolation beneath 600mm Metals (zinc) contaminated vegetables clean cover or redistribution beneath Ingestion Metals (lead, arsenic) hardstand/highways/floor Human health Dermal contact Metals (lead) slabs (Future residents) ◊ BTEX, hydrocarbons Treatment or removal of (especially halogenated hydrocarbons Infiltration of water supply hydrocarbons), phenol, CN, pipes Water company may still sulphate, sulphide & chloride insist of “protectaline” in the made ground pipework ◊ transient risks to construction workers will be addressed by the adoption of appropriate health and safety measures in accordance with the Health and Safety at Work Act 1974 and regulations made under the Act including for example the COSHH Regulations.
9.7 Waste classification
9.7.1 Disposal of the made ground off site is generally not considered appropriate, economically viable, nor in line with current Government philosophy regarding sustainable development. However, some excess arisings may be generated by excavations for foundations, sewers etc. Disposal to landfill (or an appropriate soil / aggregate transfer station) may be the most practical solution, if redistribution and retention on site is not feasible.
9.7.2 Following excavation and stockpiling, sampling will be required prior to disposal.
9.7.3 As there is no WRAP protocol for soils, the characterisation, sampling and classification of soils arising from brownfield sites has been incorporated within the Environment Agency’s Technical Guidance WM32. Classification of soils as inert, non-hazardous or hazardous in accordance with WM3 is quite a complex process.
9.7.4 If waste soil is classed as hazardous following classification under WM3, and destined for landfill, waste acceptance criteria (WAC) leachate testing will need to be undertaken. However, non-hazardous soil waste can go to a non-hazardous landfill facility; no further testing (e.g. WAC) is required.
9.7.5 WAC analysis is different to the ‘routine’ laboratory testing (such as that included earlier in this Section) undertaken in order to determine hazardous properties. Lithos typically only include WAC analysis if significant off-site disposal (of soil classified as hazardous waste) is anticipated.
9.7.6 It is critical if material is to be exported from site that this is allocated an appropriate waste code, following the steps within WM3. Waste carriers transporting, and sites accepting, this material should have a corresponding code within their permits. It is the responsibility of those generating the waste (i.e. the site), to ensure that the waste is handled and disposed of appropriately.
2 Technical Guidance WM3 – Guidance on the classification and assessment of waste. Environment Agency 2015
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9.7.7 Soil treatment facilities (STFs) provide an alternative to landfill. STFs are regulated by the Environment Agency and allow soils to be treated and screened (effectively recycled to be used at other sites). Export to an STF does not require WAC testing and suitability of various soil types will be dependent on material waste codes, which may be allocated after consideration of the data in Section 0 but will often need supplementing with further testing after soils have been stockpiled (see also advice in Section 13.3).
9.7.8 Most STFs are permitted to accept soils with waste code 17 05 04 (i.e. soils which do not exhibit hazardous properties). Lithos has a list of permitted STFs and can help identify one local to this development site.
9.7.9 With respect to asbestos, waste soils will be classed hazardous if the soil mass contains more than 0.1% asbestos fibres that are free and dispersed. However, WM3 states that where the waste contains identifiable pieces of asbestos (i.e. any particle of a size that can be identified as potentially being asbestos by a competent person if examined by the naked eye), then the waste is hazardous if the concentration of asbestos in the pieces alone is 0.1%. If a stockpile of soil contained rare fragments of broken asbestos-cement sheeting, the whole stockpile would be classed as hazardous unless all the fragments could be picked- out (even though the concentration of asbestos in the soil mass might be orders of magnitude less than 0.1%).
9.7.10 As discussed in Section 7.4, tarmac hardstand is present across roads which are expected to be removed as part of the development.
9.7.11 This tarmac could be recycled and crushed to yield a 6F3 selected granular material, provided the recovered bitumen content is less than 10% (determined in accordance with BS598-102:2003). Crushed tarmac could also be blended with crushed concrete etc to generate 6F2 graded material. 6F2 can contain up to 50% recycled tarmac/asphalt (provided it does not pose a contamination risk to controlled waters and, if the proportion of asphalt is greater than 20%, the recovered bitumen content is less than 2%).
9.7.12 However, if off-site disposal is anticipated, tarmac assessment is based on the amount of coal tar present, this will vary depending on the age of the tarmac. The assessment is based on the amount of benzo(a)pyrene and has a concentration limit of 50mg/kg.
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10 HAZARDOUS GAS
10.1 Methane & carbon dioxide
10.1.1 The site is not affected by the following potential sources of hazardous gas:
• Not located within 250m of a known former or current landfill site or backfilled feature (e.g. quarry, pond, canal etc) • Neither underlain by shallow mineworkings nor located in an area considered susceptible to mines gas emissions • Not underlain by a significant thickness of made ground • Not underlain shallow chalk deposits
10.1.2 However, thin beds (maximum thickness of 200mm) of pseudo-fibrous Peat were encountered in 2 of the 10 boreholes at the base of the Tidal Flat Deposits (around 6.5m). Consequently, whilst risks are considered very low, in addition to the programmed groundwater dips, some gas monitoring will now be undertaken.
10.2 Radon
10.2.1 Requirements with respect radon measures are set out in Building Regulations Approved Document C. Probability bandings (based on the proportion of properties in a given area that exceed the Action Level; currently 200 Bq.m-3) are used to determine whether a property requires no, basic or full measures.
10.2.2 At present Approved Document C advocates basic measures for the probability banding 3% to 10% (full measures if >10%). However, Public Health England would like to see all new build include basic measures.
10.2.3 Information from Landmark suggests that radon protection measures are not required. This is confirmed by the Public Health England UK radon map which indicates that the site lies in an area where less than 1% of homes are estimated to be above the action level.
10.2.4 As such, no special precautions against radon are required on this site.
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11 GEOTECHNICAL TESTING
11.1 General
11.1.1 A total of 68 samples of natural soil were delivered to a suitably accredited laboratory with a schedule of geotechnical testing drawn up by Lithos.
11.1.2 The geotechnical laboratory test results are presented in Appendix J to this report.
11.2 Atterberg limits
11.2.1 The plasticity indices of 39 samples of cohesive soil have been determined; results are summarised below.
No. Moisture content Range of Plasticity Soil type samples range Shrinkability Indices* (average) tested (average) Tidal Flat Deposits – 14 23 – 33 (27) 23 – 46 (35) High Desiccated layer Tidal Flat Deposits – Partially 12 24 – 57 (37) 27 – 52 (35) High desiccated layer Tidal Flat Deposits – Lower 7 25 – 45 (35) 21 – 47 (34) High saturated layer Cohesive Glacial Deposits 6 19 – 30 (25) 24 – 40 (33) Medium * Modified where appropriate in accordance with Chapter 4.2 of the NHBC Standards. Note. The term Shrinkability is equivalent to the term Volume Change Potential used in Chapter 4.2.
11.2.2 A total of 6 samples of the 33 samples of Tidal Flat Deposits tested (c. 1 in 5) returned a modified plasticity index of 40% or greater.
11.2.3 For the purposes of foundation design, it is recommended that all cohesive soils be regarded as being of high shrinkability.
11.2.4 It is noted that the desiccated ‘upper’ layer of the Tidal Flat Deposits has a lower range, and average, moisture content than the lower layers of Tidal Flat Deposits. This supports the interpretation discussed in Section 7.5 that the uppermost cohesive soils comprise a stiffer desiccated crust across this site.
11.3 Soluble sulphate and pH
11.3.1 In accordance with BRE Special Digest 1:2005, this site has been classified as brownfield with a mobile groundwater regime.
11.3.2 It is envisaged foundations will extend to depths of about 16m through made ground and natural strata and samples taken from this depth range have been submitted for pH and water-soluble sulphate (2:1 soil/water extract).
11.3.3 The concentrations of sulphate in the aqueous natural soil extracts of 39 samples were determined. In addition, 30 samples of made ground were tested as part of the contamination suite. The pH value of each sample has also been determined.
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11.3.4 The highest water-soluble sulphate concentration and the lowest pH value for each soil type analysed are shown in the table below.
No. samples Lowest pH Conservative typical soluble Soil type tested values sulphate concentration (mg/l) Sub-Base (inc. ash & chalk) 15 7.4 800 Cohesive Made Ground 3 8.0 220 Granular Made Ground 1 10.2 330 Demolition Arisings 11 7.8 1,100 Tidal Flat Deposits 33 7.5 200 Cohesive Glacial Deposits 6 8.1 180
11.3.5 pH values were all above 5.5, therefore concentrations of chloride and nitrate are considered insignificant.
11.3.6 In accordance with Table C2 of SD1, sub-surface concrete which is in contact with Made Ground (crucially Demolition Arisings and Sub-Base materials sourced from beneath the existing roads), should be Design Sulphate Class DS-2 with the site allocated an ACEC Classification of AC-2.
11.3.7 Concrete in contact with natural soils (the Tidal Flat Deposits) could be DS-1, with an ACEC Classification of AC-1. However, given the proposed works which are ongoing at this site (demolition of buildings and turnover of made ground) it is unlikely that foundations will not at least ‘pass through’ Made Ground and it would be prudent to assume DS-2 / AC-2 for all concrete at this site.
11.4 One dimensional consolidation tests
11.4.1 To assess the settlement characteristics of the natural cohesive strata, one-dimensional consolidation tests were carried out on 11 samples of Tidal Flat Deposits and 2 samples of Cohesive Glacial Deposits. Four loading pressures and one unloading pressure were specified in accordance with BS1377:Part 5:1990.
11.4.2 Laboratory certificates are included in Appendix J. The results are provided as plots of voids ratio and coefficient of consolidation against applied pressure. The coefficient of volume compressibility (mv) has been derived for each test in accordance with BS1377 at a pressure range starting close to overburden (p0). Tests are summarised in the table below.
2 Hole ID Depth (m) Material mv (m /MN)* Compressibility BH02 1.2 1.00 High BH04 1.0 1.10 High BH03 2.0 0.88 High BH09 2.5 0.76 High BH10 0.7 1.39 High BH10 1.4 Tidal Flat Deposits 1.00 High BH02 3.5 0.65 High BH04 3.0 0.70 High BH05 4.5 0.56 High BH06 4.0 0.60 High BH10 4.0 0.60 High BH06 7.5 0.20 Medium Cohesive Glacial Till BH08 8.0 0.19 Medium
* Design mv value calculated for a stress increment starting at the approximate overburden pressure.
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11.5 Undrained shear strength testing
Undrained triaxial compression tests
11.5.1 Unconsolidated undrained triaxial compression tests were carried out at a single cell pressure, roughly equal to the overburden pressure, on 10 undisturbed (UT) samples of Tidal Flat Deposits and on 15 samples of Cohesive Glacial Deposits. specimens. Unconsolidated tests are carried out without prior compression, i.e. they are tested ‘as received’.
11.5.2 Fully saturated conditions were assumed and the apparent undrained cohesion Su, was taken as half the deviator stress at failure. Results are summarised in the table overleaf:
Depth Field consistency Laboratory Shear Hole ID Material Strength term (m) description strength/kPa BH03 2.0 Soft 28 Low Strength Tidal Flat Deposits BH06 2.0 (Partially Desiccated Soft 41 Medium Strength Layer) BH10 1.4 Soft 18 Very Low Strength BH02 3.5 Soft 35 Low Strength BH04 3.0 Soft 13 Very Low Strength Tidal Flat Deposits BH05 2.5 (Lower Saturated Soft 14 Very Low Strength Layer) BH06 4.0 Soft 8 Extremely Low Strength BH09 2.5 Soft 19 Very Low Strength BH01 10.5 107 High Strength Stiff BH01 14.0 76 High Strength BH02 8.0 Stiff 131 High Strength BH02 14.0 76 High Strength Stiff BH02 17.0 93 High Strength BH03 8.0 42 Medium Strength Stiff BH03 17.0 100 High Strength
BH04 8.0 Cohesive Glacial Stiff 93 High Strength BH05 7.5 Deposits Stiff 227 Very High Strength BH05 13.5 Stiff 55 Medium Strength BH05 16.5 Stiff 79 High Strength BH06 7.5 Stiff 160 High Strength BH07 9.0 Stiff 67 Medium Strength BH08 8.0 Stiff 59 Medium Strength BH08 17 Stiff 85 Medium Strength BH10 11.5 Stiff 41 Medium Strength
11.5.3 Triaxial testing shows a general trend of very poor strength within the Tidal Flat Deposits and high strength within the Cohesive Glacial Deposits.
11.5.4 The results of triaxial testing shown vs. depth are presented on graph plot 1 in Annex III.
Hand shear vane testing
11.5.5 Hand shear vane testing was undertaken within trial pits in-situ to around 1.2m depth and from larger blocks of excavated clay below that depth. Hand vane tests were also undertaken in the cable percussion boreholes where sample recovery allowed.
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11.5.6 The results are summarised within graph plot 2 in Annex III and illustrate a decrease in shear strength with depth in the Tidal Flat Deposits and a moderately wide spread of shear strength within the Cohesive Glacial Deposits (the likely reason for the wide ‘spread’ of data is due to disturbance during drilling).
11.5.7 Below 1.0m the shear strength is typically around 50kPa; below 2.0m shear strength has reduced to around 15kPa.
11.6 Standard penetration test (SPT)
11.6.1 The in-situ strength of soils beneath the site was determined during drilling using SPT testing; typically at 1.0m intervals.
11.6.2 The results of SPT tests are presented on graph plot 3 in Annex III and generally show very poor strength soils at shallow depth and then an increase in strength from c.7m depth (about the depth where Cohesive Glacial Deposits are encountered.
11.7 Discussion of geotechnical laboratory results
11.7.1 The in-situ shear strength of cohesive soils are presented on the graphs in Annex III at the end of this document.
11.7.2 In-situ and laboratory testing has shown that soils beneath this site decrease in strength with depth from surface down to c. 7m depth (within the Tidal Flat Deposits). Beyond c.7m Cohesive Glacial Deposits are consistently of medium to high strength.
11.7.3 Cohesive Soils beneath this site should be assumed to be of high shrinkability.
11.7.4 The Tidal Flat Deposits are considered to be of high compressibility; the Cohesive Glacial Deposits are considered to be of medium compressibility.
12 GEOTECHNICAL ISSUES
12.1 Conceptual site model
12.1.1 The conceptual site model has been revised in light of the findings and interpretation of geotechnical test data.
12.1.2 The site can be divided into three areas based on ground conditions (see Drawing 3039/6) – Area A (housing recently cleared), Area B (houses remain) and Area C (existing estate roads).
12.1.3 Made ground in Area A extends to an average depth of about 0.5m (maximum recorded of 1.1m); made ground is typically thicker beneath the footprints of former buildings and shallower in more distal garden areas. Made Ground in Area B extends to an average depth of about 0.35m (maximum recorded of 1.0m).
12.1.4 Natural ground typically comprises Tidal Flat Deposits to depths of around 7m, over Cohesive & Granular Glacial Deposits (Till) to depths in excess of 20m.
12.1.5 The shallower Tidal Flat Deposits are desiccated, and this has increased their in-situ strength (typically stiff, high strength) to a depth of around 1.3m. However, with depth the strength of these Deposits reduces dramatically - initially to firm (medium strength) to around 2.3m and then to soft / very soft (very low to extremely low strength).
12.1.6 Thin beds (maximum thickness of 200mm) of pseudo-fibrous Peat were encountered in 2 of the 10 boreholes at the base of the Tidal Flat Deposits (around 6.5m).
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12.1.7 Groundwater encountered within shallow excavations generally comprises relatively minor seepages. More significant groundwater strikes were only encountered within deeper boreholes where granular glacial deposits were encountered.
12.2 Mining & quarrying
12.2.1 This site is located beyond the CA’s defined coalfields.
12.2.2 There are no known quarries on, or within 50m of the site.
12.2.3 Therefore the proposed development is not considered to be at risk from mining related issues.
12.3 Site regrade and/or ground improvement
12.3.1 As part of the ongoing demolition works it is understood that ground beneath the footprints of plots (Area B) will be turned over to a depth of 1.0m, whilst ground beneath existing gardens (Area B) will be turned over to a depth of 0.5m.
12.3.2 Where made ground has already been turned over (Area A) it does not generally contain a significant proportion of oversized materials (bricks, boulders etc) and it is generally considered to not be significantly contaminated
12.4 Foundation recommendations
General
12.4.1 Redevelopment with ‘traditional’ two storey domestic dwellings is proposed, although no site layout has been provided to date.
12.4.2 Mature and semi-mature trees are present across much of Area B; presumably many mature trees were present across Area A but have been removed during demolition works. No tree survey information has been made available to Lithos.
12.4.3 We have assumed that final development levels will not differ significantly from ground levels existing at the time of investigation. Any digital terrain modelling undertaken, or commissioned by, Keepmoat & Strata should consider implications for the foundation recommendations outlined below.
12.4.4 Made ground is not considered a suitable founding material and foundations should therefore be taken through these materials into underlying natural strata of adequate bearing capacity.
12.4.5 Sub-surface concrete in contact with the made ground should be Design Sulphate Class DS-2 with the site allocated an ACEC Classification of AC-2. Concrete in contact with natural ground should be DS-1 and AC-1.
Brief appraisal of foundation options
12.4.6 A nearby Keepmoat development off Southcoates Lane (about 800m to the west) required plots to be founded on piles driven to depths of around 16m. However, existing (and recently demolished) houses built in the 1930s were constructed on shallow (500mm to 600mm deep) strip footings, and no obvious signs of structural distress were noted during the walkover.
12.4.7 Keepmoat have expressed interest in a low load (timber frame) construction if new dwellings could also be built on strips.
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12.4.8 Lithos have given ‘high level’ consideration to the possibility of a shallow founding solution here, but the presence of made ground, high shrinkability clays, (felled) trees, and current- day building regulation / warranty requirements would all require a minimum founding depth of at least 1.0m, and this results in founding towards (in some places, likely below) the base of the desiccated (high strength) layer.
12.4.9 Assuming a founding depth of 1.0m, preliminary calculations suggest that line loads would need to be less than about 20kN/m run. Consequently, at this stage a shallow founding solution is considered unlikely to be viable here and piles will almost certainly be required.
Piled foundations
12.4.10 Foundation recommendations assume that development will be two or three storey construction and that line loads will not exceed 90kN/m run. If this is not the case significant alteration to these recommendations will be required.
12.4.11 Piled foundations are likely to be the only viable option for dwellings constructed at this site due to the presence of low strength soils to depths of c.7m. The following general comments relating to piling are provided for guidance, and further advice should be sought from a specialist-piling contractor.
12.4.12 Piled foundations should extend into the underlying higher strength Cohesive Glacial Deposits. The safe working load that may be supported on a pile is dependent on the pile diameter, its founding depth and the method of installation.
12.4.13 Boreholes indicate that the Cohesive Glacial Deposits are present from depths of between 6m and 8m, below current ground levels.
12.4.14 Piles are expected to predominantly rely on skin friction from the Glacial Deposits, although there will also be some end-bearing resistance at the base of each pile.
12.4.15 Given the presence of the very soft and compressible Tidal Flat Deposits, it is essential that pile design allows for downdrag (negative skin friction).
12.4.16 It is recommended that flexible service connections are used on this site, especially where they enter the buildings, in order to avoid any possible damage due to self-settlement of the weak strata once the site is developed.
12.4.17 Driven piles may lessen the volume of soils requiring off-site disposal (cf arisings associated with say trench fill). However, driving can induce some ground vibration. Assessment of any vibration risk to adjacent structures and/or existing site features should be undertaken by pile designer.
12.4.18 Should any impenetrable shallow obstructions be encountered, i.e. old foundation, they should either be grubbed-up, or alternatively the piling layout could be re-designed (although might also require design of foundations able to span and/or cantilever as necessary).
12.4.19 New houses can be built off ring beams designed to span the piles. In order to bond them to the piles, the tops of the piles must be broken out to expose the reinforcement, which can then be tied to that of the beams.
12.4.20 For piled foundations suspended floor slabs should be utilised. A pre-cast ‘Beam and Block’ concrete ground floor construction suspended across the ring beams could be utilised.
12.4.21 A proprietary driven piling system, incorporating ring beams and pre-cast concrete ground floor construction could be considered for this development.
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12.4.22 Ground conditions at this site are considered likely to require provision of a piling mat (working platform) and further advice should be sought from the appointed specialist-piling contractor regarding the proposed plant loadings and resulting pressures. This data, together with a knowledge of the strength and variability of the near-surface ground conditions is required in order that design of a mat can be undertaken in accordance with guidance provided in the 2004 BRE document, “BR 470: Working platforms for tracked plant”.
12.4.23 The design of working platforms for tracked plant is a geotechnical design process and should be carried out by a competent person. The following parties should have input into the design:
• Permanent works designer, to consider additional uses for platform material as part of the overall development • Principal contractor, to define any other purposes for which the platform might be used • Contractor or subcontractor, to specify requirements for the platform, including gradients, ramps and edges
12.4.24 Piles can provide an enhanced pathway for the vertical migration of mobile contaminants. The Environment Agency may therefore object to the adoption of piles as a foundation solution. However, objection is considered unlikely given the nature of the contamination encountered, and the fact that the underlying chalk bedrock is located at depths of greater than 30m depth beneath relatively impermeable cohesive soils.
12.5 Floor slabs
12.5.1 Floors for low rise housing (2-3 storeys) constructed on piled foundations typically utilise reinforced concrete ground beams which rest on pre-cast or in-situ pile caps. A suspended ‘Beam and Block’ ground floor is then usually constructed using concrete or polystyrene blocks placed between further concrete beams suspended across the ring beams.
12.5.2 In accordance with NHBC Standards Chapter 4.2, a minimum void height of 300mm should be adopted for a precast block and beam (or suspended timber) floor; this includes a 150mm ventilation allowance. If a suspended, cast in-situ slab (on a void former) is proposed, a minimum clear void height of 150mm should be adopted; of course, the actual thickness of the void former will be significantly greater.
12.6 Designated concrete mixes
12.6.1 Designated mixes are considered in BRE Special Digest SD1 and BS 8500 -1:2015+A1:2016. However, in addition to soil chemistry (sulphate class), there are a number of other considerations relating to structural design that need to be taken into account when determining an appropriate concrete mix.
12.6.2 Consequently, Keepmoat & Strata should seek advice from their appointed Structural Engineer.
12.7 Excavations
12.7.1 Groundwater should be controlled in accordance with CIRIA report 113 “Control of Groundwater for Temporary Works”.
12.7.2 Based on the results of the investigation it is considered unlikely that major groundwater flows will be encountered in shallow excavations.
12.7.3 Excavations should remain stable in the short term but if left open for any significant period of time may require shoring most notably in granular soils and made ground.
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12.8 Drainage
12.8.1 Based on observations made during the investigation, soakaways will not provide a suitable drainage solution for surface water run-off at the site. Consequently, it will be necessary to consider alternative sustainable drainage systems (SUDS), and there may be a need for surface water balancing.
12.8.2 Alternative SUDS options (see CIRIA C753:2015 for further details) include:
• Swales – linear grassed features in which surface water can be stored or conveyed. Where suitable, swales can be designed to allow infiltration. • Ponds – designed to have permanent pool of water, but with capacity to provide temporary storage-controlled discharge.
12.8.3 Yorkshire Water have published a guide3 for developers and designers outlining their design requirements for surface water attenuation assets.
12.8.4 The guide also discusses required access to flow control chambers, large diameter (i.e. >900mm) surface water storage pipes, and surface water storage tanks.
12.9 Highways
12.9.1 The construction of existing roads across the site has been discussed in Section 7.4.
12.9.2 It is understood that Holmpton Grove and St. Johns Grove may be retained during the development, but other roads which cross the site are likely to be removed.
12.9.3 Made ground is present across the site and consultation with the adopting authority, regarding the specification of the highways, is strongly recommended.
12.9.4 Consequently, where made ground topsoil is present its full thickness should be excavated and replaced with suitable aggregate in accordance with Series 600 (Earthworks) of The Highways Agency (HA) “Specification for Highway Works” 1998.
12.9.5 Any residual made ground materials in the base of the excavation should be inspected and (where necessary) any soft spots removed and replaced with suitable engineered fill.
12.9.6 Where the made ground is re-engineered it is considered that a CBR value of at least 3% should be achievable. However, this should be verified by field trials.
12.9.7 Crushing of demolition/hardstand/foundation arisings will generate aggregate, which (subject to confirmatory testing) should be suitable for use as unbound pavement materials within the highways. Concrete (present in floor slabs/foundations should provide a suitable aggregate for highways construction following crushing & screening.
12.10 External works
12.10.1 Any digital terrain modelling undertaken or commissioned by Keepmoat & Strata should be made available to their Engineering Designer prior to issue of an External Works Drawing.
3 Design Requirements for Surface Water Attenuation Assets, February 2017.
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13 REDEVELOPMENT ISSUES
13.1 General
13.1.1 This report has presented options with respect to foundation solutions, treatment of contamination etc that are considered technically feasible and in line with current good practice. Consequently, we would expect to obtain regulatory approval for whichever option is adopted, although this cannot be guaranteed. Copies of this report should be forwarded to the relevant regulatory authorities (Warranty Provider & Local Authority) for their comment/approval.
13.1.2 Even after an appropriate preliminary investigation and ground investigation, with exploratory holes on a closely spaced grid (say trial pits at 30m centres), a geoenvironmental appraisal is typically based on inspection of the ground underlying less than 0.5% of the total site area (and much less at depths in excess of about 3.5m). Consequently, there is always a possibility that unanticipated ground conditions will be encountered during the site preparatory works.
13.1.3 If unanticipated ground is encountered during the site preparatory works, the Contractor should immediately seek further advice from the Engineer.
13.2 Remediation strategy
13.2.1 Given the absence of any significant contamination, a remediation strategy is not considered necessary. Nonetheless, some preparatory works will be required, most notably:
• Demolition of the remaining buildings • General site clearance of surface materials and vegetation • Break-up of floor slabs, foundations and highways • Excavation of the Ash & Clinker and Cohesive Made Ground, or isolation beneath appropriate cover • Provision of 300mm thickness of topsoil in all garden and landscaped areas
13.2.2 No areas of gross contamination were encountered during the site investigation. However, if any buried drums, “oily”, odorous, brightly coloured etc. materials are encountered, further advice should be sought from Lithos.
13.3 Control of excavation arisings
13.3.1 The groundworker should carefully segregate (and stockpile separately) made ground arisings from arisings of “clean” natural soils, in order that an excessive volume of unsuitable material is not generated.
13.3.2 It should be ensured that the groundworker understands the need for good materials management. Most notably the importance of not mixing different materials within a given stockpile; i.e. there should be separate stockpiles of: grubbed-up concrete hardstand; tarmac; Ash & Clinker; fuel-contaminated soil; excess clean, natural soil arisings; general construction waste etc.
13.3.3 Further characterisation of stockpiled materials is likely to be required if off-site disposal is proposed. See also comments in Section 9.7 regarding asbestos.
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13.3.4 Made ground arisings could be:
• Placed in area deliberately left low on completion of the remediation works in order to accommodate construction arisings • redistributed beneath concrete oversite, or areas of hardstanding, where they would be satisfactorily isolated from end users; • Isolated beneath the 300mm thick cover layer in garden or landscaped areas • Exported from site to a suitably licensed landfill facility
13.3.5 Natural ground arisings should be suitable for use as subsoil in the proposed soil cover.
13.4 Good practice guidance
13.4.1 The construction phase groundworker should follow good environmental practice to minimise the risks of spillage, leakage etc with reference, but not limited, to the following documents:
• CIRIA C502 ‘Environmental Good Practice on Site’ • EA Pollution Prevention Guidelines4: o PPG6 - Working at construction and demolition sites o PPG2 - Above ground oil storage tank o PPG7 – The safe operation of refuelling facilities. o PPG21 – Incident Response Planning
13.4.2 Site preparatory works associated with this project are likely to involve the re-use of both natural and made ground soils on site. Therefore, the Contractor should prepare a Materials Management Plan (MMP) in accordance with the CL:AIRE Code of Practice (v2, March 2011).
13.4.3 The MMP will document how all of the materials to be excavated during the proposed site preparatory and remediation earthworks are to be dealt with.
13.5 New utilities
13.5.1 It is strongly recommended that all statutory service bodies are consulted at an early stage with respect to the ground conditions within which they will lay services in order to enable them to assess at an early stage any potential abnormal costs.
13.5.2 It is recommended that trenches for services including site drainage and water supply are cut over size in order to isolate pipe materials from potential contaminants and to enable maintenance to be conducted in "clean" material.
13.5.3 Water Companies have a statutory duty to supply wholesome water, which could be compromised by the selection of an inappropriate pipe material. For example, compounds such as petroleum hydrocarbons and solvents can permeate commonly used plastics pipes, and/or corrosive chemicals can reduce the service life of metallic pipes. Guidance has been developed for the selection of pipes in brownfield sites and is contained in a UKWIR Report5.
13.5.4 This site is brownfield, and therefore consideration of soil contaminant concentrations is required. Samples taken must be representative of the soil conditions in which the water pipes are proposed to be laid; normally water pipes are laid 0.7m to 1.3m below finished ground level.
4 Whilst this has formally been withdrawn it can still be accessed via the EA archives and provides useful information on managing risks. 5 UKWIR Report 10/WM/03/21 – ‘Guidance for the Selection of Water Supply Pipes to be used in Brownfield Sites’.
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13.5.5 At the time of writing, the proposed route(s), and total length, of pipeline were unknown. Consequently, to date laboratory testing of soil samples in line with UKWIR guidance has not been undertaken.
13.5.6 However, given the site’s history and the relatively consistent ground conditions reported, the use of ‘standard’ polyethylene water supply pipes should be acceptable, although Keepmoat & Strata should consult Yorkshire Water at the earliest opportunity to confirm this.
13.6 Health & safety issues - construction workers
13.6.1 Access into excavations etc. must be controlled and undertaken in accordance with the CDM Regulations 2015, most notably Regulation 22, to mitigate risk of collapse or asphyxiation.
13.6.2 Before site operations are started, the necessary COSHH statements and Health & Safety Plan should be drafted in accordance with the CDM regulations.
13.6.3 The bulk of the made ground will be retained on site. This made ground contains some contaminants at concentrations above the guidance threshold values for an end use that includes domestic gardens. Workers involved in excavations for foundations, drainage, utilities etc are likely to come into direct contact with the made ground.
13.6.4 Although workers will only be exposed to the contaminated soil for a relatively short time, the contaminants represent a risk, and simple precautionary measures are required, i.e. good personal hygiene and basic personnel protective equipment. See also comments in Section 9.7 regarding asbestos.
13.6.5 Consequently, during the remediation and construction phases of the site development it will be necessary to protect the health and safety of site personnel. General guidance on these matters is given in the Health and Safety Executive (HSE) document “Protection of Workers and the General Public during the Redevelopment of Contaminated Land”.
13.7 Potential development constraints
13.7.1 Some deterioration of the surface is likely to be caused by trafficking, especially after topsoil has been stripped and during/after periods of significant rainfall. Consequently, it would be prudent to consider placement of a minimum 200mm thickness of suitable granular fill (i.e. a “blanket” of 6F2) along the line of proposed highways and any temporary haul roads to protect formation during the construction phase.
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14 SUMMARY OF CONCLUSIONS AND RECOMMENDATIONS
14.1 General
14.1.1 The site is located approximately 4km east of Hull city centre and comprises part of the Preston Road Housing Estate.
14.1.2 Prior to the ongoing demolition programme there were about 500 houses (256 pairs of semi- detached, 2-storey properties). At the time of writing the site was undergoing demolition; about 50% of buildings across the site had been wholly demolished, about 50% remained in- situ but were empty and boarded up, and 1% were still inhabited.
14.1.3 It is understood that consideration is being given to redevelopment of the site with ‘traditional’ two storey residential dwellings with associated gardens, POS and adoptable roads and sewers. No site layout has been provided at this stage.
14.1.4 The site can be divided into three areas based on ground conditions (see Drawing 3039/6) – Area A (housing recently cleared), Area B (houses remain) and Area C (existing estate roads).
14.1.5 Made ground in Area A extends to an average depth of about 0.5m (maximum recorded of 1.1m); made ground is typically thicker beneath the footprints of former buildings and shallower in more distal garden areas. Made Ground in Area B extends to an average depth of about 0.35m (maximum recorded of 1.0m).
14.1.6 Natural ground typically comprises Tidal Flat Deposits to depths of around 7m, over Cohesive & Granular Glacial Deposits (Till) to depths in excess of 20m.
14.1.7 The shallower Tidal Flat Deposits are desiccated, and this has increased their in-situ strength (typically stiff, high strength) to a depth of around 1.3m. However, with depth the strength of these Deposits reduces dramatically - initially to firm (medium strength) to around 2.3m and then to soft / very soft (very low to extremely low strength).
14.1.8 Thin beds (maximum thickness of 200mm) of pseudo-fibrous Peat were encountered in 2 of the 10 boreholes at the base of the Tidal Flat Deposits (around 6.5m).
14.1.9 Groundwater encountered within shallow excavations generally comprises relatively minor seepages. More significant groundwater strikes were only encountered within deeper boreholes where granular glacial deposits were encountered.
14.1.10 Existing buildings are founded upon strip footings at a depth of 500mm to 600mm.
14.2 Mining
14.2.1 This site is located beyond the CA’s defined coalfields.
14.3 Hazardous gas
14.3.1 The site is in an area where less than 1% of homes are estimated to be above the radon action level.
14.3.2 There are no known or suspected areas of landfilling within 250m, and the site is not in area considered susceptible to mines gas, nor is it underlain by shallow mineworkings.
14.3.3 However, thin beds (maximum thickness of 200mm) of pseudo-fibrous Peat were encountered in 2 of the 10 boreholes at the base of the Tidal Flat Deposits (around 6.5m). Consequently, whilst risks are considered very low, gas monitoring is now being undertaken.
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14.4 Contamination & remediation
14.4.1 Made Ground across the majority of Areas A & B is considered suitable to remain in gardens beneath a nominal clean cover of 300mm.
14.4.2 Cohesive Made Ground was only encountered 3 of the 89 exploratory holes excavated across the entire site, and significant contamination was only reported in one of these - TP45 (Area A). Cohesive Made Ground in the vicinity of TP45 is considered contaminated and should be isolated beneath hardstand/floor slabs/highways, or beneath a clean cover of 1,000mm.
14.4.3 Ash & Clinker from beneath Area C (existing roads) should be suitable for isolation beneath hardstand/floor slabs/highways.
14.5 Foundations
14.5.1 A nearby Keepmoat development off Southcoates Lane (about 800m to the west) required plots to be founded on piles driven to depths of around 16m. However, existing (and recently demolished) houses built in the 1930s were constructed on shallow (500mm to 600mm deep) strip footings, and no obvious signs of structural distress were noted during the walkover.
14.5.2 Lithos have given ‘high level’ consideration to the possibility of a shallow founding solution here, but the presence of made ground, high shrinkability clays, (felled) trees, and current- day building regulation / warranty requirements would all require a minimum founding depth of at least 1.0m, and this results in founding towards (in some places, likely below) the base of the desiccated (high strength) layer.
14.5.3 Assuming a founding depth of 1.0m, preliminary calculations suggest that line loads would need to be less than about 20kN/m run. Consequently, at this stage a shallow founding solution is considered unlikely to be viable here and piles will almost certainly be required.
14.6 Flooding
14.6.1 The EA indicate that the site is located within a Flood Zone 3 but benefits from flood defence.
14.7 Drainage
14.7.1 Based on observations made during the fieldwork soakaways into natural shallow soils will not provide a suitable means of surface water disposal. Consequently, it will be necessary to consider alternative sustainable drainage systems (SUDS), and there may be a need for surface water balancing.
14.8 Highways
14.8.1 A total of 9 roads cross the site; Flinton Grove, Foston Grove, Hilston Grove and Holmpton Grove all run roughly north to south; Brigham Grove, Wansford Grove, Cranswick Grove and St. Johns Grove all run east to west. It is understood that Holmpton Grove & St. Johns Grove may be retained, but other roads which cross the site are likely to be removed.
14.8.2 Made ground is present across the of the site, typically to depths of around 0.5m, and consultation with the adopting authority, regarding the specification of the highways, is strongly recommended.
14.8.3 Where made ground topsoil is present it should be excavated and either replaced with suitable aggregate. Where made ground is re-engineered it is considered that a CBR value of at least 3% should be achievable. However, this should be verified by field trials.
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14.9 Further Work
14.9.1 Due to issues with the SI licence and ongoing demolition activities, 7 trial pits were not advanced in the centre-west (Phase 5) of the site. A days’ post-demolition trial pitting would be prudent.
14.9.2 Additional monitoring visits (increase from the initially anticipated 3 for groundwater dips, to 6) and a gas risk assessment are also recommended.
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ANNEX I
Summary Tables of Ground Conditions (TPs & BHS)
Depth to Base (mbgl) Final Site Hole Total Made Cohesive Granular Tidal Flat Tidal Flat Tidal Flat Cohesive Granular Depth Hard- Sub- Demo’ Area ID Made Ground Made Made Deposits - Deposits - Deposits Peat Glacial Glacial (mbgl) stand Base Arisings Desiccated Partially - Lower Saturated ground Topsoil Ground Ground Deposits Deposits Layer Desiccated Layer Layer A BH01 20.7 0.5 - - - 0.5 - - 1.8 - 7.6 - 20.2 9.7 & 20.7 A BH02 20.5 0.7 - - - 0.7 - - 1.4 - 6.7 - 20.5 19.1 A BH03 20.1 0.3 - - - 0.3 - - - 2.4 6.7 - 20.1 18.7 A BH04 25.1 0.6 - - - 0.6 - - 1.6 - 6.7 6.9 23.0 18.3 & 25.1 A BH05 20.1 0.55 - - - 0.55 - - 1.6 - 6.3 - 20.1 19.1 A BH06 21.2 0.3 - - - 0.3 - - 1.6 2.4 6.1 6.3 20.0 20.2 A BH07 21.0 0.4 - - - 0.4 - - 0.0 2.3 6.1 - 20.2 6.3 &21.0 A BH08 20.2 0.45 - - - 0.45 - - 1.3 2.1 6.7 - 20.2 18.8 A BH09 20.1 0.45 - - - 0.45 - - 0.0 2.0 8.1 - 20.1 19.7 B BH10 20.1 0.45 - - 0.45 - - - 1.4 2.8 6.4 - 19.6 20.1 A TP01 3.5 0.45 - - 0.45 - - - 1.3 2.0 3.5 - - - B TP02 4.4 0.3 - - 0.3 - - - 1.4 2.0 4.4 - - - A TP03 3.5 0.2 - 0.2 - 0.15 - - 1.6 2.4 3.5 - - - A TP04 4.4 0.3 - - 0.3 - - - 1.0 2.2 4.4 - - - B TP05 4.0 0.4 - - 0.4 - 1.0 - 1.7 2.6 4.0 - - - B TP06 3.5 0.3 - - 0.3 - - - 1.2 2.2 3.5 - - - B TP07 3.5 0.3 - - 0.3 - - - 1.3 2.5 3.5 - - - B TP08 3.3 0.35 0.1 - - - 0.35 - 1.0 2.0 3.3 - - - B TP09 3.6 0.5 0.05 - 0.5 - - - 1.5 2.4 3.6 - - - B TP10 4.0 0.2 0.05 0.2 - - - - 0.9 2.4 4.0 - - - B TP11 4.5 0.15 - 0.15 - - - 0.35 1.3 3.0 4.5 - - - B TP12 3.1 0.35 - - 0.35 - - - 1.5 2.2 3.1 - - - B TP13 3.5 0.8 0.14 0.8 - - - - 1.7 2.7 3.5 - - -
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Depth to Base (mbgl) Final Site Hole Total Made Cohesive Granular Tidal Flat Tidal Flat Tidal Flat Cohesive Granular Depth Hard- Sub- Demo’ Area ID Made Ground Made Made Deposits - Deposits - Deposits Peat Glacial Glacial (mbgl) stand Base Arisings Desiccated Partially - Lower Saturated ground Topsoil Ground Ground Deposits Deposits Layer Desiccated Layer Layer B TP14 3.5 0.25 - - 0.25 - - - 1.8 2.7 3.5 - - - B TP15 3.0 0.4 - - 0.4 - - - 1.7 2.5 3.0 - - - B TP16 3.8 0.4 0.04 0.4 - - - - 0.9 2.4 3.8 - - - A TP17 2.9 0.7 - - - 0.7 - - 1.3 2.1 2.9 - - - A TP18 3.5 0.6 - - - 0.6 - - 1.5 2.5 3.5 - - - A TP19 3.6 0.25 - - 0.25 - - - 1.0 2.5 3.6 - - - A TP20 3.5 0.6 - - - 0.6 - - 1.5 2.1 2.9 - - - A TP21 3.9 0.3 - - - 0.3 - - 1.2 2.1 3.9 - - - A TP22 3.9 1.1 - - - 1.1 - - 1.6 2.4 3.9 - - - A TP23 4.3 0.6 - - - 0.6 - - 1.5 2.3 4.3 - - - A TP24 4.5 0.3 - - - 0.3 - - 1.6 2.4 4.5 - - - A TP25 4.0 0.5 - - - 0.5 - - 1.2 1.9 4.0 - - - A TP26 3.7 0.3 - - - 0.3 - - 1.0 1.5 3.7 - - - A TP27 3.3 0.4 - - - 0.4 - - 1.4 1.6 3.3 - - - A TP28 3.2 0.2 - - 0.2 - - - 1.4 1.8 3.2 - - - A TP29 3.7 0.25 - - 0.25 - - - 1.3 2.5 3.7 - - - A TP30 3.7 0.2 - - 0.2 - - - 1.1 2.0 3.7 - - - A TP31 3.6 0.9 - - - 0.9 - - 1.4 2.2 3.6 - - - A TP32 3.8 0.3 - - - 0.3 - - 1.2 1.8 3.8 - - - A TP33 3.5 0.5 - - - 0.5 - - 1.1 1.5 3.5 - - - A TP34 3.6 0.4 - - 0.4 - - - 1.1 1.6 3.6 - - - A TP35 4.2 0.5 - - 0.5 - - - 1.3 2.0 4.2 - - - A TP36 3.8 0.3 - - 0.3 - - - 1.2 2.2 3.8 - - - A TP37 3.8 0.3 - - 0.3 - - - 1.1 2.4 3.8 - - - A TP38 3.5 0.7 - - - 0.7 - - 1.2 1.7 3.5 - - - A TP39 3.5 0.6 - - - 0.6 - - 1.4 2.3 3.5 - - - A TP40 3.3 0.8 - - - 0.8 - - 1.2 2.0 3.0 - - -
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Depth to Base (mbgl) Final Site Hole Total Made Cohesive Granular Tidal Flat Tidal Flat Tidal Flat Cohesive Granular Depth Hard- Sub- Demo’ Area ID Made Ground Made Made Deposits - Deposits - Deposits Peat Glacial Glacial (mbgl) stand Base Arisings Desiccated Partially - Lower Saturated ground Topsoil Ground Ground Deposits Deposits Layer Desiccated Layer Layer A TP41 3.7 0.2 - - 0.2 - - - 1.2 2.2 3.7 - - - A TP42 3.3 0.5 - - - 0.5 - - 1.3 2.4 3.3 - - - A TP43 4.4 0.2 - - - 0.2 - - 1.1 2.3 4.4 - - - B TP44 3.7 0.4 - - 0.4 - - - 1.5 2.3 3.7 - - - A TP45 3.0 0.2 - - 0.2 - 1.0 - - 2.2 3.0 - - - B TP46 4.0 0.35 - - 0.35 - - - 1.1 2.4 4.0 - - - A TP47 4.0 0.2 - - - 0.2 - - 1.3 2.3 2.3 - - - A TP48 3.5 0.5 - - - 0.5 - - 1.5 2.5 3.5 - - - A TP49 3.6 0.5 - - - 0.5 - - 1.0 2.3 3.6 - - - A TP50 3.4 0.35 - - 0.35 - - - 1.3 2.0 3.4 - - - A TP51 4.1 0.7 - - - 0.7 - - 1.1 1.3 4.1 - - - A TP52 3.9 0.4 - - - 0.4 - - 1.3 2.6 3.9 - - - B TP53 3.9 0.2 - - 0.2 - - - 1.4 2.4 3.9 - - - A TP54 3.4 0.6 - - - 0.6 - - 1.4 2.3 3.4 - - - B TP55 3.7 0.2 - - 0.2 - - 0.7 1.5 2.4 3.7 - - - B TP56 3.8 0.2 - - 0.2 - - - 1.3 2.9 3.8 - - - A TP57 3.7 0.5 - - - 0.5 - - 1.3 2.3 3.7 - - - B TP58 4.2 0.4 - - 0.4 - - - 1.6 2.3 4.2 - - - B TP59 3.8 0.3 - - 0.3 - - - 1.5 2.6 3.8 - - - B TP60 3.8 0.55 0.4 0.55 - - - - 1.5 2.5 3.8 - - - B TP61 3.5 0.3 - - 0.3 - - - 1.3 - 3.5 - - - B TP62 4.0 0.3 - - 0.3 - - - 1.6 2.3 4.0 - - - B TP63 3.7 0.35 - - - 0.35 - - 1.4 2.5 3.7 - - - B TP64 3.5 0.3 - - 0.3 - - - 1.3 2.6 3.5 - - - A TP65 3.3 0.7 - - - 0.7 - - 1.3 2.7 3.3 - - - A TP66 4.0 0.8 - - - 0.8 - - 1.7 2.6 4.0 - - - A TP67 4.1 0.3 - - 0.3 - - - 1.4 2.6 4.1 - - -
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Depth to Base (mbgl) Final Site Hole Total Made Cohesive Granular Tidal Flat Tidal Flat Tidal Flat Cohesive Granular Depth Hard- Sub- Demo’ Area ID Made Ground Made Made Deposits - Deposits - Deposits Peat Glacial Glacial (mbgl) stand Base Arisings Desiccated Partially - Lower Saturated ground Topsoil Ground Ground Deposits Deposits Layer Desiccated Layer Layer A TP68 3.7 0.3 - - 0.3 - - - 1.3 2.2 3.7 - - - A TP69 4.2 0.3 - - - 0.3 - - 1.4 2.3 4.2 - - - A TP70 4.5 0.25 - - 0.25 - - - 1.3 2.4 4.5 - - - A TP71 3.8 0.4 - - - 0.4 - - 0.6 2.5 3.8 - - - A TP72 3.5 0.3 - - 0.3 - - - 1.2 2.1 3.5 - - - A TP73 3.7 0.8 - - - 0.8 - - 1.4 2.3 3.7 - - - B TP74 3.9 0.4 - - - - - 0.4 - 2.5 3.9 - - - A TP75 3.7 0.8 - - - 0.8 - - - 2.4 3.7 - - - A TP76 4.3 0.5 - - - 0.5 - - 1.4 2.8 4.3 - - - A TP77 3.6 0.25 - - 0.25 - - - 1.5 2.2 3.6 - - - B TP78 4.0 0.3 - - 0.3 - - - 1.3 2.4 4.0 - - - A TP79 3.9 0.7 - - - 0.7 - - 1.3 2.4 3.9 - - -
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Summary Tables of Ground Conditions (WSs through roads)
Depth to Base (mbgl) Intention for Hole Final Depth Road Name Total Made Surface Ash & Tidal Flat Deposits - Road ID (mbgl) Hard- stand Base Course Sub- Base Ground Course Clinker Desiccated Layer Hilston Grove removal WS01 0.45 0.45 - 0.04 0.15 0.35 0.45 - Hilston Grove removal WS02 1.0 0.6 - 0.04 0.18 0.45 0.6 >1.0 Hilston Grove removal WS03 1.0 0.5 - 0.04 0.14 0.35 0.5 >1.0 Hilston Grove removal WS04 1.0 0.5 - 0.04 0.18 0.4 0.5 >1.0 St Johns Grove retained WS05 1.0 0.4 - 0.04 0.12 0.26 0.4 >1.0 St Johns Grove retained WS06 1.0 0.4 - 0.04 0.16 0.3 0.4 >1.0 St Johns Grove retained WS07 1.0 0.25 - 0.03 0.14 0.25 - >1.0 St Johns Grove retained WS08 1.0 0.5 - 0.04 0.16 0.5 - >1.0 St Johns Grove retained WS09 1.0 0.4 - 0.04 0.14 0.4 - >1.0 St Johns Grove retained WS10 1.0 0.4 - 0.03 0.16 0.23 0.4 >1.0 St Johns Grove retained WS11 1.0 0.4 - 0.04 0.14 0.25 0.4 >1.0 St Johns Grove retained WS12 1.0 0.4 - 0.04 0.13 0.25 0.4 >1.0 St Johns Grove retained WS13 1.0 0.4 - 0.05 0.15 0.25 0.4 >1.0 St Johns Grove retained WS14 1.0 0.4 - 0.05 0.16 0.25 0.4 >1.0 Foston Grove removal WS15 1.0 0.35 - 0.04 0.12 0.35 - >0.8 Foston Grove removal WS16 1.0 0.3 - 0.04 0.16 0.3 - >1.0 Wansford Grove removal WS17 1.0 0.4 - 0.04 0.15 0.4 - >1.0 Wansford Grove removal WS18 1.0 0.35 - 0.04 0.16 0.35 - >1.0 Foston Grove removal WS19 1.0 0.35 - 0.05 0.18 0.35 - >1.0 Foston Grove removal WS20 0.75 0.4 - 0.04 0.14 0.4 - >0.75 - removal WS21 1.0 0.3 0.2 - - - 0.3 >1.0 - removal WS22 1.0 0.3 0.2 - - - 0.3 >1.0 Hapham Grove removal WS23 1.0 0.35 - 0.04 0.14 0.35 - >1.0 Hapham Grove removal WS24 1.0 0.35 - 0.04 0.16 0.35 - >1.0 Hapham Grove removal WS25 1.0 0.35 - 0.03 0.15 0.25 0.35 >1.0 Hapham Grove removal WS26 1.0 0.4 - 0.04 0.16 0.4 - >1.0
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Depth to Base (mbgl) Intention for Hole Final Depth Road Name Total Made Surface Ash & Tidal Flat Deposits - Road ID (mbgl) Hard- stand Base Course Sub- Base Ground Course Clinker Desiccated Layer Hapham Grove removal WS27 1.0 0.35 - 0.04 0.18 0.35 - >1.0 Brigham Grove removal WS28 1.0 0.5 - 0.03 0.18 0.4 0.5 >1.0 Brigham Grove removal WS29 1.0 0.5 - 0.04 0.16 0.35 0.5 >1.0 Holmpton Grove retained WS30 1.0 0.5 - 0.04 0.14 0.35 0.5 >1.0 Holmpton Grove retained WS31 1.0 0.5 - 0.04 0.16 0.4 0.5 >1.0 Brigham Grove removal WS32 1.0 0.55 - 0.05 0.18 0.35 0.55 >1.0 Brigham Grove removal WS33 1.0 0.4 - 0.04 0.15 0.35 0.4 >1.0 Holmpton Grove retained WS34 0.8 0.5 - 0.04 0.18 0.35 0.5 >0.8 Holmpton Grove retained WS35 1.0 0.55 - 0.04 0.2 0.4 0.55 >1.0 Wansford Grove removal WS36 1.0 0.5 - 0.03 0.17 0.45 0.5 >1.0 Wansford Grove removal WS37 1.0 0.5 - 0.04 0.18 0.3 0.5 >1.0 Holmpton Grove retained WS38 1.0 0.6 - 0.04 0.2 0.4 0.6 >1.0 Holmpton Grove retained WS39 1.0 0.5 - 0.05 0.18 0.4 0.5 >1.0 Cranswick Grove removal WS40 1.0 0.5 - 0.03 0.18 0.4 0.5 >1.0
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ANNEX II
Summary of degree of soils contamination (inorganics)
Concentrations in mg/kg unless otherwise stated. Results are quoted to 1 decimal place if <10, and whole numbers if >10. Site Expl Depth Trigger Level Concentrations are shown in BLUE and assume a residential with gardens end-use. Material Area Hole (m) As ∞ B~ Cd ∞ Cr x Cu♣$ Pb ∞ Hg* Ni Se Zn$ CV pH Asbestos 37 5 26 3000 200 200 169 127 350 200 2 A TP45 0.4 Cohesive Made Ground 8.4 85 2.7 1.10 48 200 1300 0.54 63 1.40 830 - N.D. A TP45 0.8 Cohesive Made Ground 9.0 67 3.8 0.93 38 110 1100 0.46 49 1.10 560 - N.D. A TP17 0.3 Demolition Arisings 8.2 17 1.1 0.31 28 33 140 0.26 26 0.46 140 - N.D. A TP21 0.1 Demolition Arisings 7.8 28 1.3 3.3 43 80 370 0.42 43 0.65 560 - N.D. A TP25 0.1 Demolition Arisings 8.0 15 4.3 0.29 30 23 100 0.10 34 0.49 130 - N.D. A TP31 0.5 Demolition Arisings 8.0 15 1.1 0.23 29 33 85 0.10 31 0.44 120 - N.D. A TP32 0.2 Demolition Arisings 8.0 22 1.4 0.41 30 40 130 0.13 36 0.61 190 - N.D. A TP42 0.2 Demolition Arisings 9.7 17 1.1 0.36 28 42 180 0.26 29 0.29 160 - N.D. A TP51 0.3 Demolition Arisings 8.8 18 2.0 0.48 23 43 120 0.35 19 0.21 640 - N.D. A TP54 0.3 Demolition Arisings 8.9 17 2.1 0.27 19 26 83 0.41 17 0.20 94 - N.D. A TP69 0.2 Demolition Arisings 9.3 38 2.4 0.79 32 82 230 0.33 45 0.43 310 - N.D. A TP79 0.3 Demolition Arisings 8.7 33 2.3 0.20 27 66 480 0.10 43 0.20 150 - N.D. A TP01 0.2 Made Ground Topsoil 10.0 12 0.5 0.82 21 43 100 0.20 19 0.20 140 - N.D. A TP30 0.1 Made Ground Topsoil 7.4 80 0.5 0.35 34 73 160 0.13 52 0.63 170 - N.D. A TP37 0.1 Made Ground Topsoil 8.4 19 1.4 0.59 27 35 110 0.28 22 0.20 120 - N.D. A TP68 0.2 Made Ground Topsoil 8.1 25 1.7 0.42 27 49 130 0.17 38 0.28 170 - N.D. B TP05 0.6 Cohesive Made Ground 8.0 18 2 0.22 35 24 81 0.55 38 0.42 150 - N.D. B TP44 0.3 Demolition Arisings 9.4 15 1.2 0.29 20 23 73 0.24 27 0.20 96 - N.D. B TP64 0.1 Demolition Arisings 7.7 29 1.4 0.45 35 200 130 0.16 40 0.70 250 - N.D. B TP55 0.4 Granular Made Ground 10.2 15 0.8 0.29 19 27 65 0.13 21 0.29 84 - N.D. B TP05 0.3 Made Ground Topsoil 10.4 15 1.2 0.38 24 130 100 0.36 23 0.20 130 - N.D. B TP09 0.2 Made Ground Topsoil 7.5 30 1.0 1.60 40 120 540 0.27 44 0.72 790 - N.D. B TP53 0.1 Made Ground Topsoil 7.8 33 2.1 0.42 31 62 180 0.65 38 0.80 260 - N.D. B TP59 0.1 Made Ground Topsoil 9.8 18 1.1 0.58 24 25 62 0.46 25 0.20 150 - Chrysotile B TP61 0.9 Made Ground Topsoil 7.9 32 1.8 0.64 40 55 120 0.15 44 0.70 200 - N.D. B TP10 0.1 Sub-Base 9.7 10 0.4 0.24 9.8 12 39 0.10 12 0.20 82 - N.D.
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Concentrations in mg/kg unless otherwise stated. Results are quoted to 1 decimal place if <10, and whole numbers if >10. Site Expl Depth Trigger Level Concentrations are shown in BLUE and assume a residential with gardens end-use. Material Area Hole (m) As ∞ B~ Cd ∞ Cr x Cu♣$ Pb ∞ Hg* Ni Se Zn$ CV pH Asbestos 37 5 26 3000 200 200 169 127 350 200 2 B TP11 0.1 Sub-Base 8.6 9.9 1.4 0.24 11 16 55 0.10 13 0.26 81 - N.D. B TP13 0.4 Sub-Base 8.4 14 0.45 < 0.10 5.7 3.9 10 0.10 7.8 0.20 20 - N.D. B TP16 0.2 Sub-Base 10.2 17 0.54 0.27 17 27 140 0.40 16 0.20 89 - N.D. B TP60 0.5 Sub-Base 9.1 17 1.1 1.2 23 42 120 0.21 31 0.22 170 - N.D. C WS05 0.2 Ash & Clinker 8.0 34 2.2 < 0.10 27 80 1500 0.28 45 0.32 140 1.3 N.D. C WS10 0.23 Ash & Clinker 8.6 25 3.4 0.11 17 51 130 0.11 23 0.20 72 0.1 N.D. C WS21 0.2 Ash & Clinker 8.2 22 1.2 < 0.10 17 73 42 0.10 47 0.45 51 3.7 N.D. C WS28 0.4 Ash & Clinker 7.9 60 1.5 0.48 26 220 210 0.21 44 0.76 300 5.3 N.D. C WS29 0.35 Ash & Clinker 8.0 45 1.6 < 0.10 24 150 450 0.14 42 0.20 110 0.1 N.D. C WS34 0.35 Ash & Clinker 7.6 61 1.8 0.24 39 210 410 1.10 41 0.55 210 0.2 N.D. C WS35 0.4 Ash & Clinker 7.8 48 3.2 16 25 74 980 2.80 49 0.50 2100 5.1 N.D. C WS38 0.4 Ash & Clinker 7.4 74 3.2 1.4 34 140 720 0.80 63 0.84 2300 6.4 N.D. C WS08 0.3 Chalk Sub-Base 9.4 24 2.3 0.12 18 50 130 0.11 22 0.29 72 3.2 N.D. C WS08 0.3 Chalk Sub-Base 9.4 24 2.3 0.12 18 50 130 0.11 22 0.29 72 3.2 N.D.
Key Source of guidance trigger level 60 Parameter tested for and in excess of Tier 1 concentration. ∞ Category 4 Screening Level – SP1010, December 2013 (CL:AIRE/Defra). Parameter tested for but not in excess of Tier 1 0.3 ~ Assumes all GRO is aromatic fraction C7 to C8. concentration. - Contaminant not tested for. ◊ Assumes all DRO is aliphatic fraction C10 to C12. All Soil Screening Values in brackets above have been derived using CLEA v1.06. Values assume contaminants located in a sandy loam, with 6% soil organic matter (SOM).
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Summary of organic contamination
Concentrations in mg/kg. Results are quoted to 1 decimal place if <10, and whole numbers if >10. Trigger Level Concentrations are shown in BLUE and assume a residential with gardens (and no cover) end use Site Expl Depth Material PAH TPH - C6 to C40 Area Hole (m) % TOC B(a)P ∞ Naphthalene GRO~ C6 to C10 DRO◊ C10 to C21 LRO C21 to C40 5 8 30 151 1000 A TP45 0.4 Cohesive Made Ground 19.0 0.4 7.2 51 59 70 A TP45 0.8 Cohesive Made Ground 11.0 31 0.8 55 97 220 A TP17 0.3 Demolition Arisings 2.8 1.2 0.9 42 37 150 A TP21 0.1 Demolition Arisings 3.6 1.5 1.1 46 63 150 A TP25 0.1 Demolition Arisings 2.4 0.1 0.1 44 23 49 A TP31 0.5 Demolition Arisings 3.6 0.2 0.1 45 30 110 A TP32 0.2 Demolition Arisings 2.9 0.3 0.1 60 120 180 A TP42 0.2 Demolition Arisings 3.5 2.7 0.5 43 93 330 A TP51 0.3 Demolition Arisings 2.9 16 1.8 8.9 35 72 A TP54 0.3 Demolition Arisings 2.8 6.9 0.8 41 73 770 A TP69 0.2 Demolition Arisings 5.9 0.8 0.6 42 30 58 A TP79 0.3 Demolition Arisings 2.7 2.6 0.7 40 78 340 A TP01 0.2 Made Ground Topsoil 1.9 2.3 0.6 35 56 210 A TP30 0.1 Made Ground Topsoil 8.2 0.1 0.1 47 30 71 A TP37 0.1 Made Ground Topsoil 2.4 4.2 0.5 41 56 520 A TP68 0.2 Made Ground Topsoil 3.6 0.6 0.3 39 34 98 B TP05 0.6 Cohesive Made Ground 1.6 0.2 0.1 41 26 57 B TP44 0.3 Demolition Arisings 2.6 1.8 0.6 41 33 74 B TP64 0.1 Demolition Arisings 3.5 0.3 0.1 48 27 41 B TP55 0.4 Granular Made Ground 2.1 2.4 0.2 38 39 130 B TP05 0.3 Made Ground Topsoil 4.8 11 1.6 13 69 280 B TP09 0.2 Made Ground Topsoil 6.0 0.9 0.5 12 30 69 B TP53 0.1 Made Ground Topsoil 4.1 2.8 0.5 44 41 110 B TP59 0.1 Made Ground Topsoil 3.4 0.1 0.1 39 27 76 B TP61 0.9 Made Ground Topsoil 5.8 0.7 0.1 61 41 180 B TP10 0.1 Sub-Base 0.5 0.1 0.1 1.0 1 1 B TP11 0.1 Sub-Base 0.9 0.1 0.1 1.0 1 1
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Concentrations in mg/kg. Results are quoted to 1 decimal place if <10, and whole numbers if >10. Trigger Level Concentrations are shown in BLUE and assume a residential with gardens (and no cover) end use Site Expl Depth Material PAH TPH - C6 to C40 Area Hole (m) % TOC B(a)P ∞ Naphthalene GRO~ C6 to C10 DRO◊ C10 to C21 LRO C21 to C40 5 8 30 151 1000 B TP11 0.1 Sub-Base 0.9 0.1 0.1 1.0 1 1 B TP13 0.4 Sub-Base 0.6 0.1 0.1 43 47 59 B TP13 0.4 Sub-Base 0.6 0.1 0.1 43 47 59 B TP16 0.2 Sub-Base 1.7 5.8 0.9 41 26 52 B TP16 0.2 Sub-Base 1.7 5.8 0.9 41 26 52 B TP60 0.5 Sub-Base 2.5 0.3 0.1 49 48 70 C WS05 0.2 Ash & Clinker 6.4 1.4 2.7 - - - C WS21 0.2 Ash & Clinker 14.0 0.8 1.5 - - - C WS28 0.4 Ash & Clinker 20.0 14 1.6 - - - C WS29 0.35 Ash & Clinker 3.3 5.9 0.7 - - - C WS34 0.35 Ash & Clinker 27.0 26 15 - - - C WS35 0.4 Ash & Clinker 13.0 310 4.1 - - - C WS38 0.4 Ash & Clinker 18.0 290 5.2 - - -
Key Source of guidance trigger level Directive (2000/60/EC) Establishing a Framework for Community Action in the Field of Water Policy 60 Parameter tested for and in excess of Tier 1 concentration ~ (Water Framework Directive) 0.3 Parameter tested for but not in excess of Tier 1 concentration * Water Supply (Water Quality) Regulations 1989, as amended in 2000 # PAH = sum of benzo(ghi)perylene + indeno(1,2,3-cd)pyrene x Environment Agency advice
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ANNEX III
Graph plot 1 – Graph showing Triaxial test results vs. depth
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Graph plot 2 – Graph showing hand vane test results vs. depth
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Graph plot 3 – Graph showing SPT ‘N; value converted into shear strength vs. Depth
56
Appendix A
General Notes 01 - Environmental setting
Generic notes – geoenvironmental Investigations
General Third party information obtained from the British Geological Survey (BGS) the Coal Authority the Local Authority etc is presented in the “Search Responses” Appendix of this Geoenvironmental Report. Geology, mining & quarrying In order to establish the geological setting of a site Lithos refer to BGS maps for the area and the relevant geological memoir. Further information is sourced by reference to current and historical OS plans. In July 2011 the Coal Authority (CA) formalised their requirements in relation to planning applications and introduced some new terminology. The CA using its extensive records has prepared plans for all coalfield Local Planning Authorities which effectively refines the defined coalfield areas into High Risk and Low Risk areas. High Risk areas are likely to be affected by a range of legacy issues that pose a risk to surface stability including: mine entries shallow coal workings workable coal seam outcrops mines gas and previous surface mining sites. Low Risk areas comprise the remainder of the defined coalfield and are areas where no known defined risks have been recorded although there may still be unrecorded issues. Where a site lies within either a High or Low Risk area a mining report is obtained from the CA. Landfills Lithos obtain data from Landmark or Groundsure the Environment Agency and the Local Authority with respect to known areas of landfilling within 250m of the proposed development site. Historical OS plans are also inspected for evidence of backfilled quarries railway cuttings colliery spoil tips etc. Radon Radon is a colourless odourless gas which is radioactive. It is formed in strata that contain uranium and radium (most notably granite) and can move though fissures eventually discharging to atmosphere or the spaces under and within buildings. Where radon occurs in high concentrations it can pose a risk to health. In order to assess potential risks associated with radon gas Lithos refer to BRE Report BR2111 and the Public Health England website. Advice on the limitation of exposure of the population to radon in buildings was originally published in 1990 by the National Radiological Protection Board (NRPB) which joined the Health Protection Agency (HPA) in 2005 the HPA updated NRPB advice in July 20102. The HPA became part of Public Health England in 2013. The HPA recommended that the NRPB radon Action Level for homes be retained and a new Target Level for radon in homes be introduced. The values of the Action Level and Target Level expressed as the annual average radon concentration in the home are 200 Bqm–3 and 100 Bqm–3 respectively. The Target Level was to provide an objective for remedial action in existing homes and preventive action in new homes. The term 'radon Affected Area' is defined as those parts of the country with >1% of homes estimated to be above the Action Levels. The NRPB first indicated which parts of the country should be regarded as radon Affected Areas in 1990. A more detailed mapping method was developed by the HPA in conjunction with the British Geological Survey in 20073. The level of protection needed is site-specific and can be determined by reference to this mapping on the Public Health England website which indicates the highest radon potential within each 1km grid square. Each 1km grid square is classified on the basis of the percentage of existing homes within that grid square estimated to have radon concentrations above the Action Level. There are 6 ‘bands’: <1% 1 to 3% 3 to 5% 5 to 10% 10 to 30% and >30%. The NRPB advised that action should be taken to reduce radon concentrations in existing homes if the radon concentration exceeded the Action Level of 200 Bqm–3 in room air averaged over a year ten times the average UK domestic radon concentration. NRPB advice informed changes in the requirements for radon protection in new buildings. • Basic preventive measures are required in new buildings extensions conversions and refurbishments if the probability of exceeding the Action Level is >3% in England and Wales and >1% in Scotland and Northern Ireland. • Provision for further preventive (Full) measures is required in new buildings if the probability of exceeding the Action Level is >10%. At present Building Regulations Approved Document C advocates basic measures for the probability banding 3% to 10% and full measures if >10%. However Public Health England would like to see all new build include basic measures. Action and Target Levels should also be applied to non-domestic buildings with public occupancy exceeding 2 000 hours per year and to all schools. Hydrogeology Lithos obtain information from the Environment Agency (EA) and Landmark or Groundsure with respect to: • Groundwater quality • Recorded pollution incidents • Licensed groundwater abstractions
From April 2010 the EA’s Groundwater Protection Policy uses aquifer designations that are consistent with the Water Framework Directive. These designations reflect the importance of aquifers in terms of groundwater as a resource (drinking water supply) but also their role in supporting surface water flows and wetland ecosystems. The aquifer designation data is based on geological mapping provided by the British Geological Survey. The maps are split into two different types of aquifer designation: • Superficial (Drift) - permeable unconsolidated (loose) deposits. For example sands and gravels • Bedrock - solid permeable formations e.g. sandstone chalk and limestone
The maps display the following aquifer designations: Principal aquifers: These are layers of rock or superficial deposits that have high intergranular and/or fracture permeability - meaning they usually provide a high level of water storage. They may support water supply and/or river base flow on a strategic scale. In most cases principal aquifers are aquifers previously designated as major aquifer. Secondary aquifers: These include a wide range of rock layers or superficial deposits with an equally wide range of water permeability and storage. Secondary aquifers are subdivided into three types: • Secondary A - permeable layers capable of supporting water supplies at a local rather than strategic scale and in some cases forming an important source of base flow to rivers. These are generally aquifers formerly classified as minor aquifers • Secondary B - predominantly lower permeability layers which may store and yield limited amounts of groundwater due to localised features such as fissures thin permeable horizons and weathering. These are generally the water-bearing parts of the former non-aquifers • Secondary undifferentiated - In most cases this is because the rock type in question has previously been designated as both a minor and non-aquifer in different locations due to the variable characteristics.
1 BRE Report BR211 2015: Radon: guidance on protective measures for new buildings. 2 Limitation of Human Exposure to Radon Documents of the Health Protection Agency - Radiation Chemical and Environmental Hazards RCE-15. July 2010. 3 Miles JCH Appleton JD Rees DM Green BMR Adlam KAM and Myers AH (2007). Indicative Atlas of Radon in England and Wales. Chilton HPA-RPD-033.
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Generic notes – geoenvironmental Investigations
Unproductive strata: These are rock layers or superficial deposits with low permeability that have negligible significance for water supply or river base flow. The EA maps only display the principal and secondary aquifers as coloured areas. All uncoloured areas on the map will be unproductive strata. However for uncoloured areas on the superficial (drift) designation map it is not possible to distinguish between areas of unproductive strata and areas where no superficial deposits are present to do this it is necessary to consult the published geological survey maps. For the purposes of the EA’s Groundwater Protection Policy the following default position applies unless there is site specific information to the contrary: • If no superficial (drift) aquifers are shown the bedrock designation is adopted • In areas where the bedrock designation shows unproductive strata (the uncoloured areas) the superficial designation is adopted • In all other areas the more sensitive of the two designations is used (e.g. If secondary superficial overlies principal bedrock an overall designation of principal is assumed)
The EA have also designated groundwater Source Protection Zones which are based on proximity to a groundwater source (springs wells and abstraction boreholes). The size of a Source Protection Zone is a function of the aquifer volume of groundwater abstracted and the effective rainfall and may vary from tens to several thousand hectares. Hydrology Lithos obtain information from the Environment Agency and Landmark or Groundsure with respect to: • Surface water quality • Recorded pollution incidents • Licensed abstractions (groundwater & surface waters) • Licensed discharge consents • Site susceptibility to flooding
The EA have set water quality targets for all rivers. These targets are known as River Quality Objectives (RQOs). The water quality classification scheme used to set RQO planning targets is known as the River Ecosystem scheme. The scheme comprises five classes (RE1 to RE5) which reflect the chemical quality requirements of communities of plants and animals occurring in our rivers. General Quality Assessment (GQA) grades reflect actual water quality. They are based on the most recent analytical testing undertaken by the EA. There are 6 GQA grades (denoted A to F) defined by the concentrations of biochemical oxygen demand total ammonia and dissolved oxygen. The susceptibility of a site to flooding is assessed by reference to a Flood Map on the Environment Agency's website. These maps show natural floodplains - areas potentially at risk of flooding if a river rises above its banks or high tides and stormy seas cause flooding in coastal areas. There are two different kinds of area shown on the Flood Map: 1. Dark blue areas (Flood Zone 3) could be flooded by the sea by a flood that has a 0.5% (1 in 200) or greater chance of happening each year or by a river by a flood that has a 1% (1 in 100) or greater chance of happening each year 2. Light blue areas (Flood Zone 2) show the additional extent of an extreme flood from rivers or the sea. These outlying areas are likely to be affected by a major flood with up to a 0.1% (1 in 1000) chance of occurring each year
These two colours show the extent of the natural floodplain if there were no flood defences or certain other manmade structures and channel improvements. Where there is no blue shading (Flood Zone 1) there is less than a 0.1% (1 in 1000) chance of flooding occurring each year. The maps also show all flood defences built in the last five years to protect against river floods with a 1% (1 in 100) chance of happening each year or floods from the sea with a 0.5% (1 in 200) chance of happening each year together with some but not all older defences and defences which protect against smaller floods. The Agency’s assessment of the likelihood of flooding from rivers and the sea at any location is based on the presence and effect of all flood defences predicted flood levels and ground levels. It should also be noted that as the floodplain shown is the 1 in 100 year areas outside this may be flooded by more extreme floods (e.g. the 1 in 1000 year flood). Also parts of the areas shown at risk of flooding will be flooded by lesser floods (e.g. the 1 in 5 year flood). In some places due to the shape of the river valley the smaller floods will flood a very similar extent to larger floods but to a lesser depth. If a site falls within a floodplain it is recommended that a flood survey be undertaken by a specialist who can advise on appropriate mitigating measures i.e. raising slab levels provision of storage etc. In accordance with Chapter 10 of the National Planning Policy Framework a site- specific flood risk assessment is required for: proposals of 1 hectare or greater in Flood Zone 1 or in an area within Flood Zone 1 which has critical drainage problems (as notified to the local planning authority by the Environment Agency) and any new development in Flood Zones 2 and 3. COMAH & explosive sites Lithos obtain information from Landmark or Groundsure with respect to Control of Major Accident Hazards (COMAH) or explosive sites within 1km of the proposed development site. Lithos’ report refers to any that are present and recommends that the Client seeks further advice from the HSE. Areas around COMAH sites (chemical plants etc) are zoned with respect to the implementation of emergency plans. The HSE are a statutory consultee to the local planning authority for all COMAH sites. The COMAH site may have to revise its emergency action plan if development occurs. This might be quite straightforward or could entail significant expenditure. Consequently the COMAH site may object to a proposed development (although it is the Local Authority who have final say and they are likely to place more weight on advice from the HSE). Preliminary conceptual site model The site’s environmental setting (and proposed end use) is used by Lithos to assess the significance of any contamination encountered during the subsequent ground investigation. Assessment of contaminated land is based on an evaluation of pollutant linkages (source-pathway-receptor). Contaminants within the near surface strata represent a potential source of pollution. The environment (most notably groundwater) site workers and end users are potential receptors. Potential pollutant linkages are shown on a preliminary conceptual site model (pCSM). A CSM is essentially a cross-section through a site that reflects both the surface topography and underlying geology and shows surface features of interest. The most significant sources of contamination are then superimposed onto this cross-section together with potential receptors (human health & controlled waters) and plausible pathways between the two. In addition to environmental issues the CSM should also highlight geotechnical issues. A pCSM is prepared after consideration of all available “desk study” data and before design of the ground investigation. Data reviewed should include historical plans (with superimposition on a current-day plan) previous SI reports geological maps etc. The pCSM in conjunction with knowledge of site constraints (buildings services slopes etc) is used to design the ground investigation. The revised CSM takes account of data obtained during the ground investigation including the distribution of made ground the nature and distribution of contamination etc.
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Generic notes – geoenvironmental investigations
General Lithos Ground Investigations are undertaken in accordance with current UK guidance including: BS5930:2015 “Code of practice for site investigation” Eurocode 7: BS EN 1997-1:2004. Geotechnical design - Part 1: General rules Eurocode 7: BS EN 1997-2:2007. Geotechnical design - Part 2: Ground investigation and testing BS10175:2013 "Code of practice for the identification of potentially contaminated sites" “Technical Aspects of Site Investigation” – EA R&D Technical Report P5-065/TR (2000) “Development of appropriate soil sampling strategies for land contamination” – EA R&D Technical Report P5-066/TR (2001) Contaminated Land Reports 1 to 6 most notably CLR Report No. 4 “Sampling strategies for contaminated land” “Guidance on the protection of housing on contaminated land” – NHBC & EA R&D Publication 66 (2000) AGS: 1996 “Guide to the selection of Geotechnical Soil Laboratory Testing” Exploratory hole locations Exploratory hole locations are selected by Lithos prior to commencement of fieldwork to provide a representative view of the strata beneath the site and to target potential contaminant sources identified during the preliminary investigation (desk study). Additional exploratory locations are often determined by the site engineer in light of the ground conditions actually encountered this enables better delineation of the depth and lateral extent of organic contamination poor ground relict structures etc. Investigation techniques Ground conditions can be investigated by a number of techniques the procedures used are in general accordance with BS5930: 2015 and BS1377: 1990. Techniques most commonly used by Lithos include: Machine excavated trial pits usually equipped with a backactor and a 0.6m wide bucket. Cable percussive (Shell & Auger) boreholes typically using 150mm diameter tools and casing. Window or windowless sampling boreholes (dynamic sampling). Constraints associated with existing buildings operations and underground service runs can render some sites partly or wholly inaccessible to a mechanical excavator. In such circumstances window sampling is often the most appropriate technique. A window sampling drilling rig can be manoeuvred in areas of restricted access and results in minimal disturbance of the ground (a 150mm diameter tarmac/concrete core can be lifted and put to one side). However it should be noted that window sampling allows only a limited inspection of the ground (especially made ground with a significant proportion of coarse material). Rotary percussive open-hole probeholes are typically drilled using a tri-cone rock roller or polycrystalline diamond compact (PDC) bit with air as the flushing medium. Probeholes are generally lined through made ground with temporary steel casing to prevent hole collapse.
Where installed gas\groundwater monitoring wells typically comprise a lower slotted section surrounded by a filter pack of 10 mm non- calcareous gravel and an upper plain section surrounded in part by a bentonite seal and in part by gravel or arisings. The top of the plain pipe is cut off below ground level and the monitoring well protected by a square stopcock type manhole cover set in concrete or the plain pipe is cut off just above ground level and the well protected by 100mm diameter steel borehole helmet set in concrete. Monitoring well details including the location of the response zone and bentonite seal are presented on the relevant exploratory hole logs. In-situ testing Relative densities of granular materials given on the trial pit logs are based on visual inspection only they do not relate to any specific bearing capacities. The relative densities of granular materials encountered in cable percussive boreholes are based on Standard Penetration Test (SPT) results. SPTs are carried out boreholes in accordance with BS 1377 1990 Part 9 Section 3.3. Where full penetration (600mm) is not possible N values are calculated by linear extrapolation and are shown on the logs as N* = x. The strength of cohesive deposits is determined using a hand shear vane. Shear strength test results (hand vane readings) reported on trial pit logs are considered to be more reliable than those reported on window sample logs. Significant sample disturbance occurs during window sampling and consequently shear strength results on disturbed window samples are generally lower than results obtained during trial pitting in-situ or in large excavated blocks. Sampling Typically Lithos collect at least three soil samples from each exploratory hole although in practice a greater number are often taken. The collection of a sufficient number of samples provides a sound basis upon which to schedule laboratory analysis ensuring: A sufficient number of samples from each (common) site material are tested Horizontal and vertical coverage of the site is adequate thereby providing a robust data set for use in the conceptual ground model Any localised significant but non-pervasive conditions are considered
Made ground and natural soils encountered in the field during a ground investigation often contain a significant proportion of coarse grained material (e.g. brick etc). Soil samples obtained during most investigations are often only truly representative of the in-situ soil mass where there is an absence of particles coarser than medium gravel i.e the entire soil mass would pass a 20mm sieve. Representative bulk samples of the soil mass are retrieved from coarse soils for specific geotechnical tests (most notably grading and compaction) this typically requires the collection of at least 10kg of soil and occasionally >50kg. However in the context of assessing land contamination it is generally accepted that samples should be representative of the soil matrix of the stratum from which they are taken. Consequently truly representative samples of coarse soils for subsequent contaminant analysis are not obtained - only the finer fraction is placed in sample containers. Coarse constituents not sampled would typically comprise any 'particles' with an average diameter greater than about 20mm (i.e. coarse gravel cobble and boulder). At present neither ISO/IEC 17025 nor MCERTS specify sample pre-treatment with respect to stone removal. Unsurprisingly therefore UKAS accredited testing laboratories do not adopt the same approach to stones1 – some crush and test the “as received” soil whilst others sieve out stones and analyse only the residual soil (the sieve size used varies depending on the laboratory).
1 Mark Perrin. Stoned – Sample Preparation for Soils Analysis. Ground Engineering, April 2007.
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In essence samples taken from coarser soils for contaminant analysis are “screened” by the geoenvironmental engineer in the field and often sieved again by the laboratory during sample preparation. Geoenvironmental engineers do not typically re-calculate soil mass contaminant concentrations by taking account of the unsampled coarse fraction. Likewise laboratories that remove stones typically report contaminant concentrations based on the dry weight of soil passing the sieve. In the context of land contamination and human health risk assessment this is considered reasonable because it is the soil matrix which is of greatest concern. Stones are unlikely to: Provide a significant source for plant uptake (consumption of vegetables) Remain on vegetables after washing (consumption of vegetables) Be eaten (accidentally by an adult or deliberately by a child) Be whipped-up by the wind for dust generation (inhalation) Stick to the skin for any length of time (dermal contact) Yield toxic vapour (inhalation)
Consequently Lithos instruct labs to remove all stones >10mm and to report the results as dry-weight based on the mass of matrix tested. However the laboratory are given site-specific instruction where coarse stones are coated in say oil or impregnated with mobile contaminants such as diesel. Where the stones are predominantly natural or inert (e.g. brick concrete etc) removal will clearly result in higher reported concentrations than if the stones were crushed and added to the matrix. Where the stones include a significant proportion of contaminant-rich material (e.g. slag fragments of galvanised metal etc) an argument could be made for crushing and analysing. However provided the stones are stable (i.e. unlikely to disintegrate or degrade) they should not pose a significant risk to human health for the reasons stated above. Sometimes it is necessary to obtain samples that are not representative of the wider soil matrix for example when investigating localised significant but non-pervasive conditions. Any such unrepresentative samples are annotated with the suffix ‘*’ (eg 2D* or 4G*). Lithos’ site engineer describes both the unrepresentative sample and the soil mass from which it was been taken. Sample Containers (for contaminant analysis). Samples of soil for contaminant testing are placed into appropriate containers (see below). Soil samples for organic analysis are stored in cool boxes at a temperature of approximately 4ºC until delivery to the selected laboratory.
Anticipated testing Container(s)
Asbestos identification 500ml plastic tub pH & metals and non-volatile organics 500ml glass jar Speciated TPH 500ml & 50ml glass jars VOCs (incl. naphthalene and\or GRO) 50ml glass jar
Sample Containers (for geotechnical analysis). The majority of samples are only scheduled for PI and sulphate testing for which 500g of sample is required (a full 0.5-litre plastic tub). However bulk bags are taken where scheduling of compaction or grading tests is proposed. Groundwater Where encountered during fieldwork groundwater is recorded on exploratory hole logs. If monitoring wells are installed groundwater levels are also recorded on one or more occasions after completion of the fieldwork. Long-term monitoring of standpipes or piezometers is always recommended if water levels are likely to have a significant effect on earthworks or foundation design. It should be borne in mind that the rapid excavation rates used during a ground investigation may not allow the establishment of equilibrium water levels. Water levels are likely to fluctuate with season/rainfall and could be substantially higher at wetter times of the year than those found during this investigation. Description of strata Soils encountered during a Lithos investigation are described (logged) in general accordance with BS 5930 2015. The descriptions and depth of strata encountered are presented on the exploratory hole logs and summarised in the Ground Conditions section within the main body of text. The materials encountered in the trial pits are logged samples taken and tests performed on the in-situ materials in the excavation faces to depths of up to 1.2m below this depth these operations are conducted at the surface on disturbed samples recovered from the excavation. Key to exploratory hole logs Keys to logs are presented in the Appendix containing the logs. There are two Keys – Symbols & Legends and Terms & Definitions.
Generic notes – Ground investigation fieldwork Page 2 of 2 03 – Geotechnical laboratory testing
Generic notes – geoenvironmental investigations
General Soil samples are delivered to the laboratory for testing along with a schedule of testing drawn up by Lithos. All tests are carried out in accordance with BS 1377:1990. The following laboratory testing is routinely carried out on a selection of samples: Atterberg limits & moisture contents Soluble sulphate & pH
Where soft cohesive soils are encountered one-dimensional consolidation tests are scheduled in order to assess settlement characteristics and unconsolidated undrained triaxial compression tests to assess shear strength.
The additional tests are typically only scheduled where significant earthworks regrade is anticipated: Grading Compaction tests Particle density
Test results are presented as received in an Appendix to the Geoenvironmental Report. Atterberg limits & moisture content The Liquid and Plastic Limits of samples of natural in-situ clay are determined using the cone penetrometer method and the rolling thread test. These tests enable determination of an average Plasticity Index (PI) for each “type” of clay although judgement is applied where variable results are reported. PI can be related to shrinkability (low medium or high) and then to minimum founding depth. Lithos typically only consider a soil to be shrinkable if the proportion finer than 63μm is >35%. PI results are compared against guidance given in the NHBC Standards Chapter 4.2 (revised April 2003) which advocates the use of modified Plasticity Index (I’p) defined as: I’p = Ip * (%< 425µm/100) i.e. if PI is 30% but the soil contains 80% < 425µm then: I’p = 30 * 80/100 = 24%. It should be noted that in accordance with the requirements of BS 1377 the % passing the 425µm sieve is routinely reported by testing labs. Lithos apply engineering judgment where PI results are spread over a range of classifications. Consideration is given to: The average values for each particular soil type (ie differentiate between residual soil and alluvium) The number of results in each class and The actual values
Unless the judgment strongly indicates otherwise Lithos typically adopts a conservative approach and recommends assumption of the higher classification. Soluble sulphate and pH Sulphates in soil and groundwater are the chemical agents most likely to attack sub-surface concrete resulting in expansion and softening of the concrete to a mush. Another common cause of concrete deterioration is groundwater acidity. The rate of chemical attack depends on the concentration of aggressive ions and their replenishment at the reaction surface. The rate of replenishment is related to the presence and mobility of groundwater. Lithos refer to BRE Special Digest 1 (SD1) “Concrete in aggressive ground. Part 1: Assessing the aggressive chemical environment” (2005). SD 1 provides definitions of: The nature of the site (greenfield brownfield or pyritic) The groundwater regime (static mobile or highly mobile) The design sulphate class (DS class) and The aggressive chemical environment for concrete (ACEC class)
Lithos reports clearly state each of the above for the site being considered. The concentrations of sulphate in aqueous soil/fill extracts are determined in the laboratory using the gravimetric method. The results are expressed in terms of SO4 for direct comparison with BS 5328:1997. The pH value of each sample was determined by the electrometric method. SD1 also discusses determination of “representative” sulphate concentration from a number of tests. Essentially if <10 samples of a given soil- type have been tested the highest measured sulphate concentration should be taken. If >10 samples have been tested the mean of the highest 20% of the sulphate test results can be taken. With respect to groundwater the highest sulphate concentration should always be taken. With respect to pH (soil & groundwater) the value used is the lowest value if <10 samples have been tested and the mean of the lowest 20% if >10 samples have been tested. Oedometer (Consolidation) tests Oedometer tests measure a soil's consolidation properties and are performed by applying different loads to a soil sample and measuring the deformation response. Typically the sample is subject to 5 incremental pressures (4 loading & 1 unloading) and the convention is for each subsequent pressure to be double the previous pressure. BS1377 suggests the initial pressure should be: a) For stiff soils the effective overburden pressure* b) For firm soils “somewhat less” than the effective overburden pressure c) For soft soils “appreciably less” than the effective overburden pressure usually 25 kPa or less d) For very soft soils very low typically 5 kPa or 10 kPa
* Effective overburden pressure (kNm-2) = depth (m) x soil bulk unit weight (kNm-3)
Results from these tests are used to predict how a soil in the field will deform in response to a change in effective stress.
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Generic notes – geoenvironmental investigations
Triaxial tests This test measures the mechanical properties of a soil by placing the sample between two parallel platens which apply stress in one (usually vertical) direction with fluid used to apply a confining pressure in the perpendicular directions. During the test the surrounding fluid is pressurized and then stress on the platens is increased until the material in the cylinder fails. From triaxial test data it is possible to extract fundamental material parameters including its angle of shearing resistance apparent cohesion and dilatancy angle. These parameters are then used in computer models to predict how the material will behave in a larger-scale engineering application. Quick (single stage, Unconsolidated, Undrained tests) are most appropriate for foundation design. This is because load is applied relatively quickly and shear strength of the clay will be lowest initially after the applied load causes some consolidation of the ground (after drainage results in dissipation of short-term excess pore water pressure) the in-situ clays will become progressively stronger and hence the factor of safety will increase. Confining pressure is specified as equivalent to overburden pressure (kNm-2). Foundations on granular soils would use effective shear strength parameters (c’ and phi’) to assess safe bearing capacity as the soil would fully drain quickly. These effective shear strength parameters could be determined from Consolidated Undrained (or sometimes the more expensive Consolidated Drained) triaxial tests but often correlations to the SPT are used. Unconsolidated Undrained triaxial tests are most appropriate for assessment of the stability of fill slopes on clays. Similar to foundations the application of load gradually increases the strength of the clays and hence the critical case is the short term undrained condition. Consolidated Undrained (or sometimes Consolidated Drained) triaxial tests are most appropriate for assessment of the stability of cut slopes in clays. This is because unloading of the ground leads to short term reduction in pore pressures that approximately balance the unloading hence the soil strength is largely unchanged. Over time the reduced pore pressures suck water in which leads in to the progressive increase in pore pressure and loss of strength. The fully drained state is critical which must be modelled using effective strength parameters and a reasonable estimate of the long term water table conditions. Slopes formed in granular soils would use effective shear strength parameters (c’ and phi’) to assess safe bearing capacity as the soil would fully drain quickly. These effective shear strength parameters could be determined from Consolidated Undrained (or sometimes the more expensive Consolidated Drained) triaxial tests but often correlations to the SPT are used.
Generic notes – Geotechnical laboratory testing Page 2 of 2 04 - Contamination analysis & interpretation (including WAC)
Generic notes – geoenvironmental investigations
Determination of analytical suite An assessment of potential contaminants associated with the former usages of the site is undertaken with reference to CLR 8 “Potential contaminants for the assessment of land” and the relevant DETR Industry Profile(s). Common contaminants Common Inorganic Contaminants include: • Metals most notably cadmium copper chromium mercury lead nickel and zinc • Semi-metals most notably arsenic selenium and (water soluble) boron • Non-metals most notably sulphur • Inorganic anions most notably cyanides (free & complex) sulphates sulphides and nitrates
With respect to the terminology used by most analytical laboratories: Total cyanide = Free cyanide + Complex cyanide Total cyanide (CN) is determined by acid extraction whereas free cyanide is the water soluble fraction. Complex cyanide is "bound" in compounds and is hard to breakdown. Laboratory determination of complex CN involves subjecting the sample to UV digestion for determination of both free and total CN. Thiocyanate (SCN) is a different species combined with sulphur.
Elemental sulphur (S) and free sulphur are the same. Total sulphur is all forms including that present in sulphates (SO4) sulphides etc. There are 2 forms of chromium (Cr) chromium VI and chromium III. Chromium VI is the more toxic of these. In soils total chromium is determined by a strong aqua regia acid digestion. Chromium VI is an empirical method based on a water extract test. Common Organic Contaminants include hydrocarbons phenols and polychlorinated biphenyls. Petroleum is a mixture of hydrocarbons produced from the distillation of crude oil and includes aliphatics (alkanes alkenes and cycloalkanes) aromatics (benzene and derivatives) and hydrocarbon-like compounds containing minor amounts of oxygen sulphur or nitrogen. Petroleum hydrocarbons can be grouped based on the carbon number range:
• GRO – Gasoline Range Organics (typically C6 to C10). Also referred to as PRO – Petroleum Range Organics
• DRO – Diesel Range Organics (typically C10 to C28)
• LRO - Lubricating Oil Range Organics (typically C28 to C40)
• MRO – Mineral Oil Range Organics (typically C18 to C44)
However it should be borne in mind that the terms “GRO” and “DRO” analysis are purely descriptive terms the exact definition of which varies. Total Petroleum Hydrocarbons (TPH) is also a poorly defined term some testing laboratories regard TPH as hydrocarbons ranging from C5-C40 whereas others define TPH as C10-C30. The composition of a TPH plume migrating through the ground can vary significantly this is primarily dictated by the nature of the source (eg petrol diesel engine oil etc). Furthermore different hydrocarbons are affected differently by weathering processes and this can result in further variation in the chemical composition of the TPH.
Gasoline contains light aliphatic hydrocarbons (especially within the C4 to C5 range) that are volatile. The aromatic hydrocarbons in gasoline are primarily benzene toluene ethylbenzene and xylenes referred to as BTEX. Small amounts of polycyclic aromatic hydrocarbons (PAHs) such as benzo(a)pyrene may also be present. Diesel and light fuel oils have higher molecular weights than gasoline. Consequently they are less volatile and less water soluble. About 25 to 35% is composed of aromatic hydrocarbons. BTEX concentrations are generally low. Heavy Fuel Oils are typically dark in colour and considerably more viscous than water. They contain 15 to 40% aromatic hydrocarbons. Polar nitrogen sulphur and oxygen-containing compounds (NSO) compounds are also present. Lubricating Oils are relatively viscous and insoluble in groundwater. They may contain 10 to 30% aromatics including the heavier PAHs. NSO compounds are also common. Polycyclic Aromatic Hydrocarbons (PAHs) have more than two fused benzene rings as a structural characteristic. PAH compounds are present in both petrol and diesel although in significantly lower concentrations than in coal tars. Certain PAH compounds are carcinogenic (benzo(a)pyrene) and\or mobile in the environment (naphthalene). Volatile Organic Compounds (VOCs) are organic chemicals and most are liquids that readily evaporate on exposure to air. Examples include benzene toluene xylene chloroform etc. Semi-Volatile Organic Compounds (sVOCs) include phenol and benzo(a)pyrene and have relatively low boiling points. Both groups of chemicals are readily absorbed through skin and some such as benzene are believed to be linked to tumour growth. Phenols are compounds that have a hydroxyl group (-OH) attached to an aromatic ring (ie include a benzene ring and an –OH group). Most are colourless solids. A solution of phenol in water is known as carbolic acid and is a powerful antiseptic. However phenol vapour is toxic and skin contact can result in burns. Polychlorinated Biphenyls (PCBs) were used in pre-1974 transformers as dielectric fluids. PCB’s are of increasing toxicity relative to the degree of chlorination. Acute symptoms of PCB poisoning are irritation of the respiratory tract leading to coughing and shortness of breath. Nausea vomiting and abdominal pain are caused by ingestion of PCB’s.
Dioxins and furans (polychlorinated dibenzodioxins and polychlorinated dibenzofurans) are some of the most toxic chemicals known in the environment they tend to bio-accumulate in the food chain. Dioxin is a general term that describes a group of hundreds of chemicals that are highly persistent in the environment. The most toxic compound is 2 3 7 8-tetrachlorodibenzo-p-dioxin or TCDD.
Dioxin is formed by burning chlorine-based chemical compounds with hydrocarbons. The major source of dioxin in the environment comes from waste-burning incinerators and also from backyard burn-barrels. Dioxin pollution is also affiliated with paper mills which use chlorine bleaching in their process and with the production of Polyvinyl Chloride (PVC) plastics and with the production of certain chlorinated chemicals (like many pesticides). Methods of analysis (organic compounds)
TPH by GC-FID is an analytical technique which only detects hydrocarbons (aliphatic and aromatic) in the range C10 to C40 (volatiles heavy tars humic material and sulphur are not detected). The laboratory can provide a broad ‘banded’ breakdown of the TPH results into gasoline range organics (GRO) diesel range organics (DRO) and heavier lubricating oil range organics (LRO) or fully speciated results with the reporting of hydrocarbon concentrations in 14 specific carbon bandings based upon behavioural characteristics e.g. aliphatic C6 to C8 aromatic C10 to C12 etc. Speciated VOC (by GC-MS) analysis quantifies the concentrations of 30 USA-EPA priority compounds. These include chlorinated alkanes and alkenes (in the molecular weight range chloroethane to tetrachloroethane) trimethylbenzenes dichlorobenzenes and the 4 BTEX compounds (benzene ethyl-benzene toluene & xylene).
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Generic notes – geoenvironmental investigations
Speciated sVOC by (GC-MS) analysis quantifies the concentrations of a variety of organic compounds including the 16 USA-EPA priority PAHs phenols 7 USA EPA priority PCB congeners herbicides & pesticides. Note: PAHs are hydrocarbons and consequently (where present) will be picked-up when scheduling TPH by GC-FID. Note: Risk assessment models require physiochemical properties (solubilities toxicities etc) of compounds in order to model their behaviour in the environment. These physiochemical properties cannot be derived from a single “TPH” “GRO” or “DRO” value. However the carbon banded fractions can be used in risk assessment models. Current UK guidance The UK approach to contaminated land is set out in Contaminated Land Report No. 11 (2004) “Model Procedures for the Management of Land Contamination”. The approach is based upon risk assessment where risk is defined as the combination of the probability of occurrence of a defined hazard and the magnitude of the consequences of the occurrence. In the context of land contamination there are three essential elements to any risk: (1) a contaminant source (2) a receptor (eg controlled water or people) and (3) a pathway linking (1) and (2). Risk can only exist where all three elements combine to create a pollutant linkage. Risk assessment requires the formulation of a conceptual model which supports the identification and assessment of pollutant linkages. Lithos adopt a tiered approach to risk assessment consistent with UK guidance and best practice. The initial step of such a risk assessment (or Tier 1) is the comparison of site data with appropriate UK guidance levels Lithos risk-derived screening values or remedial targets. It should be noted that exceedance of Tier 1 does not necessarily mean that remedial action will be required. Soil screening values used by Lithos
In March 2002 DEFRA and the Environment Agency published a series of technical papers (R&D Publications CLR 7 8 9 and 10) outlining the UK approach to the assessment of risk to human health from land contamination. In 2008 CLR 7 9 and 10 and all corresponding SGV and Tox reports were withdrawn and superseded by new guidance including: • Guidance on Comparing Soil Contamination Data with a Critical Concentration - CL:AIRE and CIEH May 2008 • Evaluation of models for predicting plant uptake of chemicals from soil - Science Report – SC050021/SR • Human health toxicological assessment of contaminants in soil - Science Report: SC050021/SR2 • Updated technical background to the CLEA model - Science Report: SC050021/SR3 • CLEA Software Handbook (Version 1.071) Science report: SC050021/SR4 • Compilation of data for priority organic pollutants for derivation of Soil Guideline Values - Science Report: SC050021/SR7 The approach set out in these documents represents current scientific knowledge and thinking and includes the Contaminated Land Exposure Model (CLEAv1.06). The Environment Agency are in the process of using this updated approach to regenerate a selection of Soil Guideline Values (SGVs). CLEA SGVs were derived for standard land use scenarios predominantly in the context of Part IIA using a conceptual site model (CSM) defined in SR3. Lithos have incorporated amendments to the CSM used to derive SGVs that more accurately reflect redevelopment within the planning regime consequently Lithos have not adopted any published SGV as a screening value. The CLEA conceptual site model assumes a source located in a sandy loam with 6% soil organic matter (SOM) - equivalent to 3.5% total organic carbon (TOC). However where the average TOC value for a particular soil type is significantly lower than the 3.5% evaluation of Lithos Screening Values should be undertaken and a site specific risk assessment will usually be required. Other CLEA default characteristics adopted by Lithos are:
Sandy Loam characteristics (source) Default values adopted
Total porosity (fraction) 0.53
Water filled porosity (fraction) 0.33
Air filled porosity (fraction) 0.2
Lithos have derived Screening Values for four different CSMs (scenarios) these are: A - Residential with gardens but no cover (or only up to 300mm) B - Residential with gardens and 600mm ‘clean’ cover C - Residential apartments with landscaping (i.e. no home grown produce) D - Commercial/industrial with landscaping E – Importation of soil cover
The exposure pathways considered for each scenario are detailed in the table below.
Scenario Land use Pathways Justification
• Direct ingestion of soil Residential with garden • Dermal contact Minimal cover – insufficient to break any pathways A but no cover (or only up • Consumption of vegetables & soil attached to vegetables therefore all exposure pathways are relevant. to 300mm) • Inhalation of indoor vapours and dust • Inhalation of outdoor vapours and dust
Residential with garden • Inhalation of indoor vapours The 600mm cover removes the risk from all B minimum 600mm cover • Inhalation of outdoor vapours pathways other than inhalation.
• All pathways applicable due to possible exposure Residential apartments Direct ingestion of soil from landscaped areas. However consumption of with landscaped areas • Dermal contact C home grown produce not included as unlikely to be and minimum 300mm • Inhalation of indoor vapours and dust grown in landscaped areas. Where vegetables are cover • Inhalation of outdoor vapours and dust to be grown site specific QRA may be required. • Direct ingestion of soil All pathways applicable due to possible exposure Commercial/ industrial • Dermal contact from landscaped areas. Assumed the commercial D with landscaped areas • development consists of offices to provide a no cover Inhalation of indoor vapours and dust conservative assessment. • Inhalation of outdoor vapours and dust • Direct ingestion of soil Material used as cover to break existing pathways Importation of soil for • Dermal contact therefore all direct and indirect pathways relevant E cover in garden and • however cover is not placed below plots therefore landscaped areas Consumption of vegetables & soil attached to vegetables indoor inhalation is not relevant. • Inhalation of outdoor vapours and dust
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Lithos have assumed the source of contamination is directly below the building foundations i.e. a depth to source of 0.15m as opposed to the CLEA default of 0.65m. This assumption provides for a more conservative approach than the UK default. This adjustment has been included to account for sites where made ground is re-engineered to enable new buildings to be established on raft foundations. In such situations contamination may lie directly beneath the foundation. The Soil Screening Values referred to in this document are not intended to be used when considering potential risks associated with: • Existing land uses in the context of Part IIA of the Environment Protection Act 1990 • End uses such as allotments sports fields children’s playgrounds care homes hospitals etc and • Controlled waters. In December 2013 Defra published the results of research project SP1010 – Development of Category 4 Screening Levels (C4SLs) for Assessment of Land Affected by Contamination. The objective of this project was provide technical guidance in support of Defra’s revised Statutory Guidance for Part 2A of the Environmental Protection Act 1990 (Part 2A). The revised Statutory Guidance published in April 2012 introduced a new four-category system for classifying land under Part 2A where Category 1 includes land where the level of risk is clearly unacceptable and Category 4 includes land where the level of risk posed is acceptably low. Project SP1010 aimed to deliver: • A methodology for deriving C4SLs for four generic land-uses comprising residential commercial allotments and public open space and • Demonstration of the methodology via derivation of C4SLs for 6 substances – arsenic cadmium chromium IV lead benzene & benzo(a)pyrene. The methodology for deriving both the previous Soil Guideline Values and the new Category 4 Screening Levels is based on the Environment Agency’s Contaminated Land Exposure Assessment (CLEA) methodology. Development of C4SLs has been achieved by modifying the toxicological and\or exposure parameters used within CLEA (while maintaining current exposure parameters). The Part 2A Statutory Guidance was developed on the basis that C4SLs could be used under the planning regime. However policy responsibility for the National Planning Policy Framework falls to the Department for Communities and Local Government. Defra anticipate that where they exist C4SLs will be used as generic screening criteria and Lithos consider C4SLs to be suitable for use as Tier 1 Screening Values. Lithos have discussed this matter with both NHBC and YAHPAC (collection of Yorkshire & Humberside local authorities) and received confirmation that they are satisfied with this approach. With respect to inorganic determinands Lithos derived Tier 1 values for the five Scenarios A to E are presented below:
Tier 1 assessment criteria (mg/kg) for Scenarios A to E Inorganic Comments/notes contaminant SGV* C4SL* A B C D E
As 32 37 37 40 640 37 C4SL adopted
Cd 10 26 26 149 410 26 C4SL adopted
Cr 3 000 3 000 30 000 3 000 Assumes Cr is CrIII
Pb 450 200 200 Use (A) in SI Report for 310 2 330 200 C4SL adopted initial screen . Ni 130 127 127 1 700 127 Assessment of health risk only Se 350 350 If >5 x A then 595 13 000 434 consider increase of Hg 170 169 cover to 1 000mm 238 3 640 199 Assumes in an inorganic compound B 5 5 5 5 Based on phytotoxic risks as plants are the more Cu 80-200 80-200 80-200 80-200 sensitive receptor (Cu is pH dependant) Zn 200 200 200 200
With respect to organic determinands Lithos derived Tier 1 values for the five Scenarios A to E are presented below:
Organic contaminant Tier 1 assessment criteria (mg/kg) for Scenarios A to E Comments/notes (all sourced via CLEA) SGV* C4SL* A B C D E
Benzene 0.33 0.87 0.9 0.9 3.3 98 N/A C4SL adopted
Toluene 610 600 3 000 2 700 5 000 N/A
Ethyl Benzene 350 350 932 843 5 000 N/A Calculated value over 10 000 Xylenes 240 246 327 321 5 000 N/A
Phenol 420 412 2 400 519 5 000 N/A
PCBs 2 8 2 38 N/A Based on toxicity of EC7
Benzo(a)pyrene 5 5 25 5.3 76 5 C4SL adopted. Where source is not a coal tar
Naphthalene 8 9 9 1 000 12
Gasoline Range Organics 30 34 34 5 000 45
Diesel Range Organics 151 156 154 5 000 219 See 3-step assessment of TPH below
Lubricating Range Org 1 000 5 000 2 000 5 000 1 000
* For a residential end use
The significance of PAHs can be determined by considering indicator compounds. In most cases benzo(a)pyrene (BaP) is adopted as an indicator due to the amount of toxicological data available and has been used by various authoritative bodies to assess the carcinogenic risk of PAHs in food. A surrogate marker approach can be used to estimate the toxicity of a mixture of PAHs in soil using toxicity data for individual indicator compounds within that mixture. Exposure to the surrogate marker is assumed to represent exposure to all PAHs in that matrix. The surrogate marker approach relies on a number of assumptions: • Surrogate marker (bap) must be present in all soil samples • Profile of the different pah relative to bap should be similar in all samples • PAH profile in the soil samples should be similar to that used in the pivotal toxicity study1
1 SP1010 Appendix E Provisional C4Sls for benzo(a)pyrene as a surrogate marker for PAHs CL AIRE 2013
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To assess the PAH profile in a soil sample the ratio of the seven genotoxic PAHs (benz[a]anthracene benzo[b]fluoranthene benzo[k]fluoranthene benzo[g h i]perylene chrysene dibenz[a h]anthracene and indeno[1 2 3-c d]pyrene) relative to BaP should be calculated. The ratio relative to BaP should lie within an order of magnitude above and below the mean ratio to BaP. Naphthalene should also be considered separately against its generic screen. Whilst classed as a PAH naphthalene is more volatile and mobile in the environment than most other PAHs. As such the significance of naphthalene cannot be considered within the surrogate marker approach. Similarly TPH cannot be assessed as a single “total” value and reference has been made to the Environment Agency’s document P5-080/TR3 “The UK approach for evaluating human health risks from petroleum hydrocarbons in soils”. This document supports the assumptions and recommendations made by the US Total Petroleum Hydrocarbons Criteria Working Group (TPHCWG). The TPHCWG have broken down “TPH” into representative constituent fractions or “EC Bandings”. The TPHCWG have derived a series of physiochemical and toxicological parameters for each of the bandings. The significance of speciated TPH results can be assessed by following the 3 steps outlined in the tables below.
Step Result Action
1. Consider indicator compounds: Are BTEX naphthalene benzo(a)pyrene above their respective Yes Remediation or dQRA required Tier 1 values? No Proceed to Step 2
Yes Remediation or dQRA required 2. Consider individual TPH fractions: are they above respective screening values? No Proceed to Step 3
Yes Remediation or dQRA required 3. Assess Cumulative effects: Is the calculated Hazard Index for each source >1 No TPH compounds pose no significant risk
Step 1 - Assessing indicator compounds
TPH fraction End use specific screening value (mg/kg) Indicator compound A: Residential no cover B: Residential with 600mm cover C: Residential no gardens D: Commercial\ industrial
Benzene 0.9 0.9 3.3 98
Toluene 600 3 000 2 700 5 000
Ethyl Benzene 350 932 843 5 000
Xylenes 246 327 321 5 000
Naphthalene 8 9 9 1 000
Benzo(a)pyrene 5 25 5.3 76
Step 2 - Assessing individual TPH fractions
End use specific screening value (mg/kg)
TPH fraction B: Residential with 600mm C: Residential with no A: Residential no cover D: Commercial/ industrial cover gardens
Aliphatic 5-6 GRO 41 41 42 Aliphatic 6-8 GRO 125 125 125 Aliphatic 8-10 GRO 31 31 32 Aliphatic 10-12 DRO 151 156 154 Aliphatic 12-16 DRO 500^ 500^ 500^ Aliphatic 16-21 DRO 1 000^ 5 000# 1 000^ Aliphatic 21-35 LRO 1 000^ 5 000# 1 000^ 5 000^ per fraction Aromatic 5-7 GRO 100 123 122 Aromatic 7-8 GRO 30 34 34 Aromatic 8-10 GRO 47 50 50 Aromatic 10-12 DRO 215 287 266 Aromatic 12-16 DRO 689 1 000* 1 000* Aromatic 16-21 DRO 1 000^ 5 000# 1 000^ Aromatic 21-35 LRO 1 000^ 5 000# 1 000^
* Calculated Screening Value exceeded soil saturation limit and could indicate free product therefore calculated soil saturation limit adopted as a target ^ Calculated Screening Value close to soil saturation limit screening value selected by Lithos considering visual and olfactory impacts. # Five times the screening value for Scenario A.
Step 3 - Assessing Cumulative Effects
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Other screening values used by Lithos
Tier 1 risk assessment of hazardous gas is undertaken through reference to the following documents (and further information is presented in Generic Note No. 5 – Hazardous Gas): • Approved Document C Building Regulations 2000 • Boyle & Witherington (2007) – Guidance on evaluation on development proposals on sites where methane and carbon dioxide are present incorporating “traffic lights”. Report Ref. 10627-R01-(02) for NHBC • CIRIA C665 (2007) – Assessing risks posed by hazardous ground gases to buildings • BS 8485 2015 – Code of Practice for the characterisation & remediation from ground gas in affected developments With respect to the assessment of potential phytotoxic effects of contaminants Lithos refer to “The Soil Code” (MAFF 1998) for copper and zinc. The CLEA SGV is adopted for nickel due to its human health effects. The potential risk to building materials is considered through reference to relevant BRE Digests with particular emphasis on BRE Special Digest 1 ‘Concrete in aggressive ground’ 2005. With respect to the interpretation of the calorific values at present there are no accepted methods to assess whether a sample is combustible and under what circumstances it might smoulder. Some guidance is given in ICRCL Note 61/84 “Notes on the fire hazards of contaminated land” which states that: “In general … it seems likely that materials whose CV’s exceed 10MJ/kg are almost certainly combustible, while those with values below 2MJ/kg are unlikely to burn”. Tier 1 groundwater risk assessments are undertaken by comparing leachate or groundwater concentrations with the appropriate water quality standard. Tier 1 Screening Values have been discussed with the Environment Agency and typically those in bold below are adopted.
Source of Tier 1 Screening Value (g/l)
Analyte Surface water (Abstraction for Water Supply Regulations 2000 Water Framework Directive EA Advice drinking) 1996 Arsenic 50 10 50 Selenium 10 10 Cadmium 5 5 1.5 Chromium 50 50 32 Copper 50 2 000 28 Lead 50 10 7.2 Nickel 20 20 Zinc 3 000 125 Boron 1,000 Mercury 1 1 0.07 Petroleum Hydrocarbons 10 1 1 1-Trichloroethane 100
1 1 Dichloroethane 100 1 2-Dichloroethane 3 10 1 1-Dichloroethene 100 Benzene 1 10 Ethylbenzene 10 Tetrachloroethene 10 10 Toluene 50 Trichloroethene 10 10 Vinyl Chloride 0.5 Trichloromethane 2.5 Xylenes 30 Chloroethane 100
Waste classification & WAC
In the context of waste soils generated by remediation and\or groundworks activities on brownfield sites the following definitions (from the Landfill Regulations 2002) apply: • Inert (e.g. uncontaminated ‘natural’ soil bricks concrete tiles & ceramics) • Non-Hazardous (e.g. soil excavated from a contaminated site which contains dangerous substances but at concentrations below prescribed thresholds) • Hazardous (e.g. soil excavated from a contaminated site which contains dangerous substances at concentrations above prescribed thresholds) Dangerous substances include compounds containing a variety of determinants commonly found in contaminated soils on brownfield sites for example arsenic lead chromium benzene etc. Landfill operators require Waste Acceptance Criteria (WAC) laboratory data if soil waste is classified as hazardous and such waste must have been subjected to pre-treatment. However subject to WAC testing it may be possible to classify it as stable non-reactive hazardous waste which can be placed within a dedicated cell within the non-hazardous landfill. Lithos typically only include WAC analysis in site investigation proposals and reports if significant off-site disposal (of soil classified as hazardous waste) is anticipated for example where redevelopment proposals include basement construction etc. If off-site disposal of soils classified as hazardous waste during redevelopment is anticipated then WAC analysis should be scheduled at an early stage in the remediation programme. However organic compounds (BTEX TPH PAH etc) are the most common contaminants that result in soils being classed as hazardous and these contaminants can often be dealt with by alternative technologies (eg by bioremediation or stabilisation) and consequently retention on site is often possible. It should be noted that non-hazardous soil waste can go to a non-hazardous landfill facility no further testing (eg WAC) is required.
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Possible action in event of Tier 1 exceedance Should any of the Tier 1 criteria detailed above be exceeded then three potential courses of action are available. (The first is only applicable in terms of human health but the second and third could also be applied to groundwater or landfill gas). 1. Undertake further statistical analysis following the approach set out in “Guidance on Comparing Soil Contamination Data with a Critical Concentration - CL:AIRE and CIEH, May 2008” in order to determine whether contaminant concentrations of inorganic contaminants within soil\fill actually present a risk (only applicable to assessing the risk to human health). 2. Carry out a more detailed quantitative risk assessment in order to determine whether contamination risks actually exist. 3. Based on a qualitative risk assessment advocate an appropriate level of remediation to “break” the pollutant linkage - for example the removal of the contaminated materials or the provision of a clean cover. Prior to undertaking any statistical analysis the issue of the averaging area requires further consideration. The CL:AIRE\CIEH document still refers to CLR 7 which suggests averaging area should reflect receptor behaviour and therefore might be a single garden or an open area used by the local community as a play area. This approach to averaging areas is considered applicable within the context of Part IIA of the Environmental Protection Act (EPA) 1990 in terms of an existing residential development. However Lithos consider the concept of a single garden as an averaging area to be inappropriate with respect to brownfield redevelopment which is regulated by the planning regime. In this context contamination across the entire site needs to be characterised by reference to the Conceptual Site Model. Consequently Lithos gather and analyse sample results by fill type and\or by former use in a given sub-area of the site before undertaking statistical analysis ie the averaging area is associated with the extent of a particular fill type or an area affected by spillage\leakage. In terms of brownfield redevelopment this is considered a more appropriate methodology which provides a more representative sample population for statistical analysis. As such the entire site is considered in terms of the proposed end use be this residential with or without gardens. Analysis by soil\fill type is appropriate for essentially immobile contaminants associated with a particular fill type for example arsenic in colliery spoil metals in ash & clinker sulphate in plaster-rich demolition rubble etc. Analysis by former use is appropriate where more mobile contaminants have entered the ground for example diesel associated with leakage from a former fuel tank downward migration of leachable metals through granular materials various soluble contaminants present in a wastewater leaking into the ground via a fractured sewer etc. In these circumstances it may be appropriate to undertake statistical analysis of sample results from a variety of different soil\fill types. However consideration would have to be given to factors such as porosity which might influence impregnation of a mobile contaminant into the soil mass ie contamination would normally be more pervasive and significant in granular soils than cohesive soils
Generic notes – Contamination Page 6 of 6
Appendix B
Drawings The Site TA 135 302
Reproduced from OS Explorer map 1:25,000 scale by permission of Ordnance Survey on behalf of The Controller of Her Majesty's Stationery Office. Crown copyright. All rights reserved. Licence number 100049696.
CLIENT JOB TITLE DRAWING TITLE DRAWN DATE GLM 12/10/2018
CHECKED DATE KEEPMOAT PRESTON ROAD, SITE LOCATION REG 12/10/2018
STATUS HOMES HULL PLAN FOR COMMENT DRAFT [email protected] FOR APPROVAL FINAL www.lithos.co.uk SCALE SHEET DRAWING NO. REVISION Tel 01937 545330 1:25,000 A4 3039/1 NOTES
GRASS & GARDEN AREAS
FORMER BUILDING - DEMOLISHED
BUILDING - EXISTING/OCCUPIED (Oct. '18)
MACADAM ROAD/FOOTPATH
LINE OF FORMER DRAINAGE WATERCOURSE / POND (As shown on 1891 OS PLan)
APPROXIMATE SITE BOUNDARY LB
TCB PRESTON ROAD
REV. DESCRIPTION DATE
BRIGHAM GROVE
HOLDERNESS DRAIN
FOSTON GROVE [email protected]
HILSTON GROVE www.lithos.co.uk WANSFORD GROVE Tel 01937 545330 Holderness Drain HOLMPTON GROVE
CLIENT A G A
CRANSWICK GROVE ST JOHNS GROVE KEEPMOAT HOMES
HARPHAM GROVE
A G
JOB TITLE
TCB PRESTON ROAD, HULL
DRAWING TITLE
Playground
SITE FEATURES
Playground
DRAWN DATE STATUS GLM 18/10/2018 FOR COMMENT FOR APPROVAL CHECKED DATE DRAFT
REG 18/10/2018 FINAL
SCALE SHEET DRAWING NO. REVISION 1:2,500 A3 3039/3 NOTES
GRASS & GARDEN AREAS
BUILDING - EXISTING & OCCUPIED
BUILDING - EXISTING & UNOCCUPIED
FORMER BUILDING - DEMOLISHED
MACADAM ROAD/FOOTPATH
APPROXIMATE SITE BOUNDARY
LOCATION & ORIENTATION OF PHOTOGRAPH 9
T S
9
07 1
0 8 3 REV. DESCRIPTION DATE
S
B
9 2 3
B
1 1
Y S S 23 B
1
1 9 D WN NG
B
2
2
2 3
[email protected] www.lithos.co.uk
Tel 01937 545330 8
92 CLIENT
2 3 A A
7 3
6
6
66
4 76
28
28 23
33 9
30 KEEPMOAT
B
8
6 36 9 HOMES
0
S 8
25 0
3 y 6 S 30 9 9 22 0
0 8
0 0
32 32
28 28
2 2
JOB TITLE
PRESTON ROAD, HULL
DRAWING TITLE
SITE PHOTOGRAPHS
DRAWN DATE STATUS GLM 18/10/2018 FOR COMMENT FOR APPROVAL CHECKED DATE DRAFT
REG 18/10/2018 FINAL
SCALE SHEET DRAW NG NO. REVISION NOT TO SCALE A3 3039/4 NOTES
EXISTING ROADS EXISTING POSSIBLE RELICT DEMOLISHED WITH ASH SUB-BASE RESIDENTIAL FOUNDATIONS & DWELLINGS WITH & UTILITY RUNS DWELLINGS & FLOOR SLABS 1.0m TURNOVER GARDENS
1 2 1 2 1 2 4 X 5 V W
D C A B A D A C A C A C
REV. DESCRIPTION DATE
SAND/PEAT LENS Y 3 3 FORMER DRAINAGE Z PERCHED HOLDERNESS DRAIN 3 CHANNELS GROUNDWATER (SURFACE WATERCOURSE) 3
[email protected] www.lithos.co.uk
Tel 01937 545330 SAND/GRAVEL LENS
CLIENT
PERCHED Z GROUNDWATER KEEPMOAT HOMES
Z GROUNDWATER (PRINCIPAL AQUIFER & SPZ3)
JOB TITLE
PRESTON ROAD, HULL KEY SOURCES PATHWAYS RECEPTORS
TOPSOIL A MADE GROUND (INORGANICS) 1 DERMAL CONTACT V END USERS (RESIDENTS) DRAWING TITLE MADE GROUND, INC MG TURNED 2 INGESTION/INHALATION OVER FOLLOWING DEMOLITION B LEAKAGE/SPILLAGE (ORGANICS) W SITE WORKERS PRELIMINARY CONCEPTUAL SITE MADE GROUND BENEATH ROADS, LEACHING OF CONTAMINANTS MODEL LIKELY ASH FILL C ASH FILL & ASH TIPPING (PAHs) 3 X VEGETATION COHESIVE ALLUVIAL DEPOSITS D ASBESTOS 4 UPTAKE BY PLANTS Y SURFACE WATERS DRAWN DATE STATUS GLM 19/10/2018 FOR COMMENT COHESIVE GLACIAL DEPOSITS (TILL) FOR APPROVAL 5 VOLATILISATION GROUNDWATER CHECKED DATE Z DRAFT
REG 19/10/2018 FINAL FLAMBOROUGH CHALK FORMATION
SCALE SHEET DRAW NG NO. REVISION Not to scale A3 3039/5 Sta
107
71
56
60 54 58
301
83 318
Shelter Club
LB 97
106 314 312
291
TCB
Community Centre 111
PO
Estate Office
TP79 281 68 Youth Centre
El Sub Sta 123 302 BH06 TCB WS20 189
TP73 199 55 IP01 WS27
TP75 294 53 TP74
2 LB TP78 TP70
IP02 Shelter TP71 TP36 WS30 TP37 WS01 TP25 TP28
TP77 TP76 TP33
TP72 TP69 TP32
TP29 200 292 200a TP26 WS19 WS18 WS31 TP35 BH01 WS26 TP34 BH03 TP30
TP27 Crown Hotel (PH) WS21 WS28 TP68 WS29 TP31 TP38 TP09 WS17 WS32 TP66 TP42 WS34 WS33 WS02 TP43 TP18 TP20 TP08 TP23 BH05
WS22 TP67 35 TP41 TP24 TP10 TP39 WS16 TP19 TP40 WS35 WS23 TP21 TP17 BH02 TP22 TP62 WS37 TP63 WS36 Holderness Drain TP13 TP12 TP61 TP44 BH04 WS38
BH07 TP11 WS03 TP46 TP51 78
TP45 92 WS24
TP47 263
TP14 TP64 TP07 WS15 TP52 TP49 TP50
TP06 TP48 WS39
WS40 WS05 57
257
TP15
TP60 71
30 24
32 34 WS06 TP53 TP16 26 TP58 WS04
2 TP01 TP65 1 WS07 TP55 26a
Mulberry Court 260
3 BH08 WS25 66
7 1 to 35
4
56 76
BH10 6
TP56 28 WS08 TP59 TP54 WS09 2 TP02 TP03 TP57 28a 23
WS10 167 250 1 33 Regeneration Centre WS11 159
161 21
40 30 36 BH09 WS12 15 WS14 TCB
WS13
152
TP04 IP03 148
176
36
164
196
TP05 16 28
30a
El Sub Sta 2 184
32 20
El Sub Sta
58 54 50
62 33 2 Foredyke 3 42 38 Primary 66 46 34 43 Playground 4 31 26 23 27 School 11 15 47 30 9 19 22 7 10
70 18 14 6
74
59
78
KEY NOTES STATUS CLIENT JOB TITLE DRAWING TITLE TRIAL PIT LOCATION TP FOR COMMENT FOR APPROVAL DRAFT FINAL CABLE PERCUSSION BOREHOLE LOCATION BH01 DRAWN DATE ROAD CORE & DYNAMIC SAMPLE BOREHOLE GLM 19/11/2018 WS40 LOCATION EXPLORATORY HOLE LOCATIONS CHECKED DATE PRESTON ROAD, HULL IP01 INSPECTION PIT LOCATION REG 19/11/2018 KEEPMOAT HOMES (TO DATE) [email protected] EXISTING RESIDENTIAL DWELLING SCALE SHEET www.lithos.co.uk 1:1,000 A1 GRASS & GARDEN AREAS Tel 01937 545330 DRAWING NO. REVISION MACADAM ROAD/FOOTPATH 3039/6 REV. DESCRIPTION DATE APPROXIMATE SITE BOUNDARY NOTES
EXISTING ROADS EXISTING POSSIBLE RELICT DEMOLISHED WITH ASH SUB-BASE RESIDENTIAL FOUNDATIONS & DWELLINGS WITH & UTILITY RUNS DWELLINGS & FLOOR SLABS 1.0m TURNOVER GARDENS
1 2 4 X V 2 W
B A A MEDIUM STRENGTH
REV. DESCRIPTION DATE
VERY LOW STRENGTH FROM c. 1.5m Y COHESIVE HOLDERNESS DRAIN EXTREMELY LOW STRENGTH FROM c. 2.0m MADE (SURFACE GROUND WATERCOURSE) [email protected] www.lithos.co.uk
Tel 01937 545330
CLIENT
VERY HIGH STRENGTH FROM c. 6.7m
KEEPMOAT HOMES BEDROCK AT >30m
Z GROUNDWATER (PRINCIPAL AQUIFER & SPZ3)
JOB TITLE
PRESTON ROAD, HULL KEY SOURCES PATHWAYS RECEPTORS
TOPSOIL 1 DERMAL CONTACT A MADE GROUND (INORGANICS) V END USERS (RESIDENTS) DRAWING TITLE MADE GROUND, INC MG TURNED 2 INGESTION/INHALATION OVER FOLLOWING DEMOLITION B ASBESTOS W SITE WORKERS REVISED CONCEPTUAL SITE MODEL MADE GROUND BENEATH ROADS, LEACHING OF CONTAMINANTS LIKELY ASH FILL 3 X VEGETATION COHESIVE ALLUVIAL DEPOSITS UPTAKE BY PLANTS 4 Y SURFACE WATERS DRAWN DATE STATUS GLM 14/12/2018 FOR COMMENT COHESIVE GLACIAL DEPOSITS (TILL) VOLATILISATION FOR APPROVAL 5 Z GROUNDWATER CHECKED DATE DRAFT FLAMBOROUGH CHALK FORMATION REG 14/12/2018 FINAL
SCALE SHEET DRAW NG NO. REVISION Not to scale A3 3039/7 NOTES
TRIAL PIT LOCATION TP CABLE PERCUSSION BOREHOLE LOCATION BH01 ROAD CORE & DYNAMIC SAMPLE BOREHOLE WS40 LOCATION
AREA A (LAND WHICH HAD UNDERGONE DEMOLITION & CLEARANCE)
AREA B (LAND AWAITING DEMOLITION & CLEARANCE)
LB MACADAM ROAD/FOOTPATH
TCB LOCATION OF FORMER (AREA A) OR EXISTING (AREA B) RESIDENTIAL DWELLING
APPROXIMATE SITE BOUNDARY
TP79 BH06 WS20
TP73 WS27 TP75 TP74
TP78 TP70
TP71 TP36 WS30 TP37 WS01 TP25 TP28
TP77 TP76 TP33 TP32 TP72 TP69 TP29
TP26 WS19 WS18 WS31 TP35 BH01 WS26 TP34 BH03 TP30
TP27 WS21 WS28 TP68 WS29 TP31 TP38 TP09 WS17 WS32 TP66 TP42 WS34 WS33 WS02 TP43 TP18 TP20 TP08 TP23 BH05
WS22 TP67 TP41 TP24 TP10 TP39 WS16 TP19 TP40 WS35 WS23 TP21 TP17 BH02 TP22 TP62 WS37 WS36 Holderness Drain TP13 TP12 TP63 TP61 TP44 BH04 WS38 BH07 TP11 WS03 TP46 TP51 TP45
WS24 TP47 A G A TP14 TP64 REV. DESCRIPTION DATE TP07 WS15 TP52 TP49 TP50
TP06 TP48 WS39
WS40 WS05 TP15 TP60
WS06 TP53 TP16 [email protected] TP58 WS04 www.lithos.co.uk TP01 TP65 WS07 TP55 Tel 01937 545330 BH08 WS25
CLIENT TP56 BH10 WS08 TP59 TP54 WS09 TP02 TP03 TP57A G WS10 WS11 BH09 WS12 WS14 KEEPMOAT TCB WS13 TP04 HOMES
TP05
JOB TITLE
PRESTON ROAD, HULL
Playground
DRAWING TITLE SITE AREAS (BASED ON FEATURES/GROUND CONDITIONS) Playground
DRAWN DATE STATUS GLM 19/11/2018 FOR COMMENT FOR APPROVAL CHECKED DATE DRAFT REG 19/11/2018 FINAL
SCALE SHEET DRAWING NO. REVISION 1:1,000 A1 3039/8
Appendix C
Commission 004/3039/REG
10th October 2018
Mr A Bradley Registered in England 07068066 Keepmoat Homes Yorkshire East Parkhill The Waterfront Wetherby Lakeside Boulevard West Yorkshire Doncaster LS22 5DZ DN4 5PL T 01937 545 330 www.lithos.co.uk
Dear Andy
Preston Road, Hull
Further to our site meeting on Monday afternoon, please find attached our updated proposal for undertaking a site investigation on the above land. This proposal now takes account of the most recent demolition plan (dated 25th June 2018) and Monday’s walkover.
We understand that your proposed development will include traditional 2 storey domestic dwellings with associated gardens, POS and adoptable roads and sewers; although no layout is available yet.
Review of the information supplied suggests that the site consists of a single parcel of land of approximately 15 hectares between Flinton Grove (west) and Marleet Lane (east), and Preston Rd (North) and St Johns Grove/Cranswick Grove/Wansford Grove (south).
It was apparent from Monday’s visit that about half the houses have been demolished, with most the remainder boarded-up, although a few are still occupied. Whilst many properties remain in the southern half, the vast majority are vacant and boarded-up and access into the rear gardens of these for pitting and boring looks reasonable. Consequently, we now expect to be able to complete ground investigation of the entire site in “one hit”.
Brief review of Old Maps and Environment Agency data suggests the site:
• Appears to have remained undeveloped until the 1940s, when a housing estate was built; • Is not located within 250m of a known landfill site; and, • Is not within a groundwater source protection zone, although an SPZ3 lies adjacent to the west.
Brief examination of the relevant geological map suggests the site is underlain by Tidal Flat Deposits (soft clays) to about 6m, over Boulder Clay, with chalk bedrock likely at significant depth (>30m). This site is located beyond the Coal Authority’s defined coalfields, therefore a mining report is not required.
A nearby Keepmoat development required plots to be founded on piles driven to depths of around 16m. However, it was interesting to note that the post-war, 2-storey houses built on this estate were established on relatively shallow (<1m deep) footings; and no evidence of structural distress was evident during the walkover. Keepmoat might consider low load (timber frame) plot construction here if could new dwellings could also be built on strips. Lithos will inspect the foundations of a few plots not yet demolished and discuss findings with NHBC.
It is understood that the demolition specification (copy not seen by Lithos) included removal of slabs and foundations (c. 1m deep strips), and that the uppermost 1m of ground within plot footprints (& 0.5m in gardens) be turned-over to chase-out all relict obstructions. This is likely to have resulted in mixing of topsoil and subsoil in garden areas.
It is also understood that services have been disconnected in the footpath (those already cleared). Consequently, exploratory holes can be advanced anywhere (beyond footpath) where houses have already been cleared. However, where houses have not yet demolished, we will restrict exploratory holes to former back gardens only.
The scope of works outlined in this letter should enable us to assess abnormal development issues, associated with ground. However, the nature of site investigation is such that it is not always possible to foresee all the potential issues. Consequently, it is sometimes necessary to recommend additional work, but where this occurs we will inform you immediately, provide costs, and seek your further instruction. We have visited site and reviewed available geological maps in order to minimise the likelihood of further work.
Our site investigation will be undertaken in accordance with UK good practice (as outlined in BS5930, BS10175, CLR11 etc). Our Report may not be fully compliant with Eurocode 7 (EC7) and will not purport to be a Ground Investigation Report, nor a Geotechnical Design Report as defined by EC7. Our ground appraisal is intended to assist others as they proceed with design of the proposed development.
This proposal allows for the following works:
Desk study: Environmental search data and historical maps (obtained from Landmark or Groundsure), will be reviewed in order to determine whether any past land uses have had any effect on the proposed development. In addition, published geological plans of the area will be examined.
We will also visit site to undertake a walkover survey.
Fieldwork: As the whole site is essentially accessible now, fieldwork will comprise 7 day’s trial pitting and the drilling of 10 cable percussion boreholes to depths of about 20m. All trial pits and boreholes will be supervised and logged by an experienced geoenvironmental engineer.
The boreholes are primarily intended to enable the retrieval of geotechnical data from depth, but will also allow the installation of groundwater wells. On completion of the works we will dip the monitoring wells monthly for 3 months.
Based on anticipated ground, soakaways are considered highly unlikely to provide a satisfactory solution for surface water drainage and no allowance has been made for soakaway testing at this stage.
Representative soil samples of natural and man-made ground, including any contaminated samples, will be taken during the works. In-situ shear strengths of any cohesive soils encountered will be determined by the use of a hand-held shear vane.
We will make every effort to compact arisings and ‘sweep’ them over each pit. However, you should be aware that on completion of the investigation, “graves” of spoil (each about 3m long by 1m wide) unsuitable for trafficking, will be left up to 400mm proud at each trial pit location. At this stage, no allowance has been made for any further reinstatement such as removal of excess arisings, replacement of turf.
This investigation should yield sufficient data to enable a foundation zoning plan, and possibly a detailed Foundation Schedule. However, if ground conditions are found to be more variable than anticipated, a ‘tighter’ grid of pits will be necessary prior to preparation of a detailed Foundation Schedule. This proposal does not allow for the preparation of a detailed Foundation Schedule, but we will provide a quote on completion of the site investigation if requested.
Page 2 of 6
This site is unlikely to be underlain by significant thicknesses of made ground. Furthermore, we are not aware of any other sources of hazardous gas (shallow mine workings, landfill sites etc) within influencing distance of the site. Consequently, at this stage, we have not allowed for undertaking a hazardous gas risk assessment but we will review the need for this in light of desk study data and the ground conditions actually encountered.
We will also advance mini-percussion boreholes to about 1m depth at about 40m intervals along those roads expected to be retained (shown by blue lines on the LTP Highways Concept Plan, dated 4th Oct. ’10), and 80m centres along those roads expected to be removed. This will enable determination of existing road construction. The holes will be cored through tarmac (surface & base courses), with dynamic sampling through the underlying sub-base, and into deeper formation material (possibly natural soils). As requested by Hull CC (Highways), these boreholes will be backfilled with concrete to about 0.15m bgl, and topped-off with cold-lay tarmac.
Boreholes will be located off the road centre-line (c. 1.5m from kerb) in order to minimise disruption to traffic (very light at present given small number of occupied dwellings). As discussed with Hull CC, each working area will be temporarily fenced-off with “Chapter 8” barriers and traffic cones to prevent vehicular access.
Hull CC have advised that road construction is likely to comprise c. 500mm of fire ash (with slag) and brick rubble, topped off with tarmac. Hull CC recommended that new highways be constructed on the existing sub-base, after first planning of the tarmac surface course.
It should be noted that such holes are not be of sufficient size to take any samples of existing sub- base / capping materials for geotechnical laboratory testing – for this we would need to perform plate load tests in inspection pits (c. 1m square) excavated through the road to derive equivalent California Bearing Ratio (CBR) values. CBR testing in pits through the road would not be a good idea due to the significant damage that would result, and the subsequent need for reinstatement.
However, if required (cost to be confirmed), we might be able to undertake CBR testing of the formation through the cored hole, provided the formation material is clay or sand – if it is a gravelly soil or bedrock, plate load tests in inspection pits would be required to obtain meaningful CBR results.
Testing: This will include routine geotechnical soils analysis, comprising 30 moisture content & Atterberg limits, and 30 pH & water-soluble sulphate.
Given the anticipated soft and potentially compressible alluvial deposits, we have allowed for single stage, undrained unconsolidated triaxial tests on 24 undisturbed samples to assess shear strength, and one-dimensional analysis on 12 undisturbed samples to assess the potential for settlement and thereby the effects of down-drag (negative skin friction).
At this stage routes, we will simply estimate CBR values from strata descriptions and classification test results.
At this stage, we have no reason to expect wide areas of the site to be underlain by significant thicknesses of made ground. Consequently, during each (of the two) phases of fieldwork we have only allowed for contaminant testing of up to 40 samples of made ground (and any topsoil). The test suite will include heavy metals, speciated PAH, and banded TPH (with supplementary speciation as/where appropriate.
Within in our proposal we have allowed for the screening (ID) of 40 samples for asbestos. In the event that positive IDs are reported, it is likely that we will need to schedule further analysis (asbestos quantification), in order to determine the significance of the results. Asbestos quantification is currently a relatively expensive test and consequently we have not allowed for it at this stage. We will inform you immediately after receipt of results if we consider asbestos quantification is required.
Page 3 of 6
Reporting & timescales: In order to provide you with sufficient information to enable assessment of abnormal costs at the earliest opportunity we will issue a concise overview report within 3 days of fieldwork completion.
On completion of the desk study, fieldwork and laboratory testing a comprehensive bound, factual and interpretative report will be issued. This will contain detailed engineering records, laboratory test results, copies of all relevant correspondence and drawings of the site. The report will include qualitative risk assessment with respect to both controlled waters and human health. The report will also include consideration of foundation types.
Fieldwork could be commenced within 3 weeks of receipt of your written instruction to proceed. Our comprehensive geoenvironmental appraisal report will be issued within 4 weeks of fieldwork completion.
Given previous usage of this land, it is considered likely that a Remediation Strategy report will be required by the Local Authority, and our proposal allows for this.
It should be noted that a Remediation Strategy outlines the remediation objectives necessary to protect environmental receptors, and render a site suitable for the proposed end use. A Remediation Strategy is not the same as a Method Statement; the latter should be prepared subsequently, usually by a Contractor, in order to detail how the objectives will be achieved.
A copy of the final report will be issued to the relevant regulatory authorities on receipt of written instruction from yourselves.
Invoicing: The attached proposal provides a breakdown of the costs associated with this investigation. This breakdown is for information only and the proposal can be regarded as a lump sum prices of £ plus VAT.
Variation will only occur in the event that a given item is not undertaken or that substantial additional works are recommended, in which case we will inform you immediately, provide costs for the required works, and seek your prior consent.
Our proposals allow for submission of the report to the Local Authority and NHBC, and for submission of a single piece of subsequent correspondence with each regulator to address any queries they may have. Any further meetings, correspondence etc, would be chargeable.
We will submit invoices for this project on completion of each Item(s) instructed.
Health, safety & welfare: The works outlined above will be carried out in accordance with Lithos’ task- and site- specific Risk Assessments and Method Statements.
Details of welfare will be included within the Method Statements. This investigation is expected to last for at least 7 working days and therefore ordinarily we would allow for provision of a Welfare Unit, but given the high risk of significant vandalism, we will simply make use of local facilities, perhaps including those at your nearby development off Southcoates Lane.
Utility plans are required in order to protect operatives from the hazards associated with striking buried services and avoid potentially substantial disruption\repair costs. We will make every effort not to damage any services (including review of utility plans and use of a CAT detector). However, Lithos cannot accept liability for damage to any underground services that are not accurately marked on plans made available to us prior to commencement of our field investigation, or have not been accurately marked on the ground by a responsible third party (e.g. utility company, site owner).
Most developers have copies of the necessary utility plans (including electricity, gas, water, drainage & telecom), and it would be appreciated if you could forward these prior to the proposed fieldworks. However, if you do not have the necessary plans, Lithos will obtain them direct from each of the utility companies.
Page 4 of 6
It is highly likely that the site is underlain by many “private” services and drains etc which will not be shown on statutory utility plans. Consequently, it would be appreciated if copies of plans showing these services could be made available to our field engineer, and\or someone with site knowledge could advise us with respect to safe locations for our exploratory holes.
Under the CDM Regulations 2015, Lithos must be provided with pre-construction information already in your possession, or information that can reasonably be obtained through sensible enquiry. This information must be relevant to the project, have an appropriate level of detail, and be proportionate to the nature of the risks.
Terms & conditions: This work will be undertaken in accordance with our Standard Terms and Conditions, a copy of which are enclosed.
It is hoped the above is sufficient for your present needs. However, should you require any further information, please contact the undersigned.
Yours sincerely
Mark Perrin Director for and on behalf of LITHOS CONSULTING LIMITED
Page 5 of 6 Keepmoat Homes The Waterfront Lakeside Boulevard Doncaster South Yorkshire DN4 5PL
Our Ref E1.11
4th October 2018
Lithos Consulting Ltd Parkhill Walton Road Wetherby Road LS22 5DZ
For the attention of Mr Mark Perrin
Dear Mark,
Proposed Development at Preston Road – Site Investigation Appointment (including core sampling)
Further to our enquiry of the 6th March 2018 ref E1.10 and your subsequent quotation in the sum of £ we are pleased to confirm your quotation meets with our approval. We hereby appoint you as our Geotechnical Engineers for the above project.
We confirm the Terms and Conditions of our contract will be set out in the following documentation:- 1. Your quotation reference 002/3039/REG 2. Keepmoat Homes Site Investigation brief dated 6th March 2018 Ref E1.10
Please provide a copy of your Professional Indemnity Cover for our records unless previously provided and note any policy restrictions or endorsements. The limit of indemnity should be a minimum of five million pounds (£5 million) for each and every claim.
Note that this appointment has been commissioned jointly by Hull City Council and the Hull City Wide Consortium (Consisting of Keepmoat Homes, Strata Homes and Home Group).
Attached for your attention are:
A. Existing Utility Plan(s). B. Records received from individual utilities.
The site is open and all areas are accessible other than the dwellings still currently occupied.
We would also like to remind you of the duties of a Designer under the CDM15 regulations – a copy of the document “CDM15 Industry Guidance for Designers” can be viewed at http://www.citb.co.uk/health-safety-and-other-topics/health- safety/construction-design-and-management-regulations/cdm-guidance-documents. You should be aware that there are key duties that apply to you and you must ensure you comply with the requirements set out in the above document. Please ensure you work in accordance with these Industry Guidelines with particular reference to:
Keepmoat is the trading name of Keepmoat Homes Limited, a company registered in England and Wales with company number 02207338, whose registered office address is at The Waterfront, Lakeside Boulevard, Doncaster DN4 5PL. Keepmoat Homes The Waterfront Lakeside Boulevard Doncaster South Yorkshire DN4 5PL
Section 2 – Eliminate, reduce and control risk through design – what you have to do Section 3 – What information do you need? Section 5 – What information you must provide?
Your invoice for the works should be returned to our accounts department at Keepmoat Homes Limited – Yorkshire Region, The Waterfront, Lakeside Boulevard, Doncaster, DN4 5PL. The invoice should clearly state the work undertaken, the site details and the name of the undersigned.
We trust that this is satisfactory but should you require any further information please get in touch.
Yours sincerely,
Chris Cammidge Senior Engineer [email protected]
Keepmoat is the trading name of Keepmoat Homes Limited, a company registered in England and Wales with company number 02207338, whose registered office address is at The Waterfront, Lakeside Boulevard, Doncaster DN4 5PL.
Appendix D
Historical OS Plans Yorkshire Published 1855 - 1856 Source map scale - 1:10,560 The historical maps shown were reproduced from maps predominantly held at the scale adopted for England, Wales and Scotland in the 1840`s. In 1854 the 1:2,500 scale was adopted for mapping urban areas; these maps were used to update the 1:10,560 maps. The published date given therefore is often some years later than the surveyed date. Before 1938, all OS maps were based on the Cassini Projection, with independent surveys of a single county or group of coun ies, giving rise to significant inaccuracies in outlying areas. In the late 1940`s, a Provisional Edition was produced, which updated the 1:10,560 mapping from a number of sources. The maps appear unfinished - with all military camps and other strategic sites removed. These maps were initially overprinted with the National Grid. In 1970, the first 1:10,000 maps were produced using the Transverse Mercator Projection. The revision process continued until recently, with new editions appearing every 10 years or so for urban areas.
Map Name(s) and Date(s)
Historical Map - Slice A
Order Details Order Number: 181983015_1_1 Customer Ref: PO13631/JW/3039 National Grid Reference: 513570, 430250 Slice: A Site Area (Ha): 16.47 Search Buffer (m): 1000 Site Details Preston Road, HULL, HU9 3UN
Tel: 0844 844 9952 Fax: 0844 844 9951 Web: www.envirocheck co uk
A Landmark Information Group Service v50.0 04-Oct-2018 Page 2 of 18 Historical Aerial Photography Published 1946 Source map scale - 1:1,250 The Historical Aerial Photos were produced by the Ordnance Survey at a scale of 1:1,250 and 1:10,560 from Air Force photography. They were produced between 1944 and 1951 as an interim measure, pending preparation of conventional mapping, due to post war resource shortages. New security measures in the 1950's meant that every photograph was re- checked for potentially unsafe information with security sites replaced by fake fields or clouds. The original editions were withdrawn and only later made available after a period of fifty years although due to the accuracy of the editing, without viewing both revisions it is not easy to spot the edits. Where available Landmark have included bo h revisions.
© Landmark Information Group and/or Data Suppliers 2010. Map Name(s) and Date(s)
Historical Aerial Photography - Segment A10
Order Details Order Number: 181983015_1_1 Customer Ref: PO13631/JW/3039 National Grid Reference: 513570, 430250 Slice: A Site Area (Ha): 16.47 Search Buffer (m): 100 Site Details Preston Road, HULL, HU9 3UN
Tel: 0844 844 9952 Fax: 0844 844 9951 Web: www.envirocheck co uk
A Landmark Information Group Service v50.0 04-Oct-2018 Page 5 of 16 Historical Aerial Photography Published 1946 Source map scale - 1:1,250 The Historical Aerial Photos were produced by the Ordnance Survey at a scale of 1:1,250 and 1:10,560 from Air Force photography. They were produced between 1944 and 1951 as an interim measure, pending preparation of conventional mapping, due to post war resource shortages. New security measures in the 1950's meant that every photograph was re- checked for potentially unsafe information with security sites replaced by fake fields or clouds. The original editions were withdrawn and only later made available after a period of fifty years although due to the accuracy of the editing, without viewing both revisions it is not easy to spot the edits. Where available Landmark have included bo h revisions.
© Landmark Information Group and/or Data Suppliers 2010. Map Name(s) and Date(s)
Historical Aerial Photography - Segment A11
Order Details Order Number: 181983015_1_1 Customer Ref: PO13631/JW/3039 National Grid Reference: 513570, 430250 Slice: A Site Area (Ha): 16.47 Search Buffer (m): 100 Site Details Preston Road, HULL, HU9 3UN
Tel: 0844 844 9952 Fax: 0844 844 9951 Web: www.envirocheck co uk
A Landmark Information Group Service v50.0 04-Oct-2018 Page 5 of 18 Yorkshire Published 1938 Source map scale - 1:10,560 The historical maps shown were reproduced from maps predominantly held at the scale adopted for England, Wales and Scotland in the 1840`s. In 1854 the 1:2,500 scale was adopted for mapping urban areas; these maps were used to update the 1:10,560 maps. The published date given therefore is often some years later than the surveyed date. Before 1938, all OS maps were based on the Cassini Projection, with independent surveys of a single county or group of coun ies, giving rise to significant inaccuracies in outlying areas. In the late 1940`s, a Provisional Edition was produced, which updated the 1:10,560 mapping from a number of sources. The maps appear unfinished - with all military camps and other strategic sites removed. These maps were initially overprinted with the National Grid. In 1970, the first 1:10,000 maps were produced using the Transverse Mercator Projection. The revision process continued until recently, with new editions appearing every 10 years or so for urban areas.
Map Name(s) and Date(s)
Historical Map - Slice A
Order Details Order Number: 181983015_1_1 Customer Ref: PO13631/JW/3039 National Grid Reference: 513570, 430250 Slice: A Site Area (Ha): 16.47 Search Buffer (m): 1000 Site Details Preston Road, HULL, HU9 3UN
Tel: 0844 844 9952 Fax: 0844 844 9951 Web: www.envirocheck co uk
A Landmark Information Group Service v50.0 04-Oct-2018 Page 9 of 18
Appendix E
Search Responses & other Correspondence