GROUND INVESTIGATION REPORT for the site at ***************** on behalf of *****************

Transcription

1 GROUND INVESTIGATION REPORT for the site at ***************** on behalf of ***************** Land Science (Brighton) Ltd Carlton Terrace Portslade Brighton East Sussex BN41 1UR T: F: W: landscience.co.uk

2 D O C U M E N T C O N T R O L Title: GROUND INVESTIGATION REPORT Site: ***************** Client: ***************** Date: 08/12/2010 Reference: Version: LS0237 v2 (updated to incorporate CP borehole) Prepared by: SALLY REDMAN M.Sc., B.Sc. (Hons.), F.G.S., AIEMA Engineer Checked by: ELLIOT TOMS CEnv., M.Sc., B.Sc. (Hons.), F.G.S., MIEnvSci Managing Director Land Science (Brighton) Ltd is part of the Land Science Ltd group of companies, specialist consultants in Geotechnical Engineering and Contaminated Land for construction, regulation, property ownership, and due diligence. By understanding our client s needs and appreciating the role that ground issues play within a wider context, we are able to provide focused, pragmatic, and technically excellent advice. For more information on how Land Science can benefit your project, please visit Ground Investigation Page 2 of 19 *****************

3 C O N T E N T S 1.0 INTRODUCTION General The Site Form of Development Geotechnical Objectives Geo-Environmental Objectives Scope of Works Schedule of Work Standards Conditions DESK STUDY Site Walkover Survey Geology Hydrogeology Hydrology Sensitive Land Uses Industrial Land Uses Radon Ground Gases Historical Data Previous Ground Investigations CONCEPTUAL SITE MODEL Contamination Sources Identified Receptors Source-Pathway-Receptor Linkages Environmental Investigation Strategy ENCOUNTERED CONDITIONS Soils Groundwater Obstructions Geotechnical Field Testing Geotechnical Laboratory Testing ENGINEERING CONSIDERATIONS Traditional Foundations Piled Foundations Ground Floor Slabs continued Ground Investigation Page 3 of 19 *****************

4 5.4 Excavations Retaining Walls and Slope Stability Pavements Building Materials Soakaways F I G U R E S FIGURE 1: FIGURE 2: Site Location Plan Investigation Layout Plan A P P E N D I C E S APPENDIX A: APPENDIX B: APPENDIX C: Desk Study Engineering Logs Geotechnical Testing Results Ground Investigation Page 4 of 19 *****************

5 1.0 INTRODUCTION 1.1 General Land Science (Brighton) Limited was instructed by ***************** to undertake a phase I and phase II geotechnical and geo-environmental investigation in relation to the proposed redevelopment of the site at ***************** (see figure 1). 1.2 The Site In summary, the site comprised two residential development plots which were situated on a steeply sloping land within the grounds of *****************. A site walkover survey is presented in section Form of Development It was understood that the proposed development was to comprise the construction of two residential properties together with private gardens, areas of car parking, provision of utility services, and associated infrastructure. The steeply sloping nature of the site required a number of low retaining walls to be constructed. Figure 2 illustrates the layout of the proposed development. 1.4 Geotechnical Objectives A geotechnical investigation was required to provide an interpretation of ground conditions with respect to foundation design, pavement construction, soakaways, concrete specification, excavation stability, basement construction parameters, and basic slope stability considerations. 1.5 Geo-Environmental Objectives Furthermore, an investigation into geo-environmental aspects of the site was required, in order to provide a generic quantitative risk assessment (GQRA) in respect of the proposed redevelopment, adjacent land uses, and the wider environment, in the context of the planning regime and PPS Scope of Works Phase I of the investigation was to comprise a desk study of geotechnical and environmental factors pertaining to the site, in order to formulate a geo-environmental Conceptual Site Model ( CSM ), and to identify areas of geotechnical concern relevant to the proposed redevelopment. In turn, this information was used in the design of the Phase II intrusive investigation and, within the constraints of the original appointment, the investigative positions and laboratory testing were to be targeted to geotechnical and geo-environmental areas of concern as appropriate. The scope of works initially agreed with the client broadly comprised the drilling of a series of window sampler boreholes and accompanying dynamic probes, with preliminary falling head soakage tests undertaken in a number of positions. Ground Investigation Page 5 of 19 *****************

6 Soft weak Head Deposits were identified in the location of one of the proposed new dwellings (lower plot), and Land Science returned to site with the Client to excavate a two further trial holes in this location. Based on the findings, it was agreed to that a piled foundation solution was likely to be required in this location, it was agreed to return to site to drill a cable percussive borehole to obtain pile design parameters. 1.7 Schedule of Work The following table summarises the dates that the various elements of the investigation works were conducted: Element Instruction Desk Study Fieldwork Details An instruction to proceed with the investigation was received from ************ on behalf of ************ on 29 th October, The desk study was commenced immediately upon receipt of the Client s instruction to proceed. A site walkover survey was conducted as part of the field work. The initial phase of intrusive investigation was completed on 9 th November, Land Science returned on 29 th November 2010 to excavate two further trial holes with the Client on the lower plot. Based on the results, Land Science returned to site on 6 th December 2010 to drill a cable percussive borehole. Laboratory Analysis Samples were submitted to the geotechnical laboratory (K4 Soils Ltd) immediately upon completion of the first phase of fieldwork, with the analysis completed by 26 th November Schedule of completion of investigation works 1.8 Standards Where practicable, the ground investigation and subsequent geotechnical and environmental assessments were undertaken in accordance with the following documents and guidance: o CLR11: Model Procedures for the Management of Contaminated Land, DEFRA and Environment Agency 2004 o Environment Agency Guidance on Requirements for Land Contamination Reports, Version 1 dated July o o Planning Policy Statement (PPS) 23: Pollution. Building Regulations Approved Document C: Site preparation and resistance to contaminants and moisture. o NHBC Standards Chapter 4.1 Land Quality - Managing Ground Conditions, September Other technical sources have been identified in respect of specific aspects of the investigation, as referenced throughout the text. Ground Investigation Page 6 of 19 *****************

7 1.9 Conditions Geotechnical and/or environmental interpretations are inherently dependant on the conditions revealed by a limited set of data and the accepted means of interpreting that data in use at the time of the investigation. Every effort is made to ensure that such data is accurate and representative, and that any assessment is performed under current best practice. However, we do not accept any liability for the scope of the investigation, for conditions that have not been directly revealed through the investigation, or for the ultimate reliability of any published and current assessment criteria or procedures adopted in interpreting that data. Any spatial or temporal extrapolation or inference is conjectural and no liability can be accepted for its accuracy; in particular, differing conditions may be revealed between or under points of investigation, and the concentrations or levels of mobile liquid and gaseous materials are likely to vary over time. It is also an inherent aspect of any investigation that areas of concern not previously anticipated are identified as works progress, and elements of the project design may vary during or after completion of the investigation; whilst every effort is made to tailor the investigation to suit within practical constraints as works progress, it may become necessary to undertake additional investigation work. Information contained in this report is intended for the use of the Client and his agents for the purposes set-out in the text, and Land Science (Brighton) Ltd makes no warranty or representation whatsoever express or implied with respect to the use of this information by any other party or for uses other than those described. We do not indemnify the Client or any third parties against any dispute, claim or consequential losses arising from any finding or other result of this investigation report. No aspect of this report should be taken as a guarantee that a site is free of hazardous or potentially contaminative materials. Ground Investigation Page 7 of 19 *****************

8 2.0 DESK STUDY The findings of the Phase I Desk Study are summarised in the following section, with relevant information obtained presented in Appendix A. Comments made in the following section are based purely on the desk study. 2.1 Site Walkover Survey Land Science undertook two formal inspections of the site, once during the fieldwork on 9 th November 2010, and again on 29 th November 2010 to inspect excavations being made as part of site enabling works. In summary, the areas under investigation comprised two residential development plots situated on steeply sloping land within the grounds of *************. The lower plot was situated adjacent to the *************, with a flat level area (upon which the new dwelling was to be constructed) and a bank at the rear rising steeply at around 30 O to 40 O. The ground was noted to be soft under foot. The area was heavily wooded; there were numerous tall mature trees around the perimeter of the plot, and a number of old tree stumps were noted within the plot itself. Conditions in this area had broadly remained unchanged by the time of the second visit, with the exception of a small cut having been made into the toe of the existing slope revealing heavily weathered light brown Chalk putty with abundant intact Chalk fragments. Access to the plots was gained via a shared driveway with *************. The driveway transversed the slope diagonally upwards to the upper plot, before turning back on itself towards the existing dwelling. The upper plot sloped less steeply than the bank between the two plots, at an angle in the order of 10 O. This plot comprised more formal gardens of the existing dwelling, with the area being mainly laid to lawn with shrubs and the like. By the time of the second visit an excavation into the slope to create the working area for the building construction had been made, with a cut face up-slope approximately 2.00m high standing near vertically and comprising reasonably unweathered blocky chalk. 2.2 Geology British Geological Survey 1:50,000 sheet number 300 entitled "Alresford indicated the geology of the site to comprise the Lewes Nodular Chalk Member (hard nodular chalk with flints) with a thin tract of Head Deposits along the lower southern boundary (variable deposits of sandy silty clay, locally gravelly, chalky and flinty in dry valleys). 2.3 Hydrogeology The table overleaf summarises the relevant groundwater vulnerability data for the site: Ground Investigation Page 8 of 19 *****************

9 Aspect Classification Details Superficial Deposits (south of the site) Secondary Aquifer (undifferentiated) Assigned in cases where it has not been possible to attribute either category A or B to a rock type. Bedrock geology Principle Aquifer These are layers of rock or drift 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. Groundwater vulnerability data The site has been identified to lie within a Source Protection Zone III. An SPZ is a protection zone placed around a well or borehole that supplies groundwater of potable quality. An SPZ is divided into three zones defined as follows: o o o Zone I - Travel time (of water) of 50 days or less to the groundwater source. Zone II - Either 25% of the source area or a travel time of 400 days whichever is greater. Zone III - The total area needed to support the abstraction. There were no groundwater abstractions identified within 500m of the site. 2.4 Hydrology There are no major watercourses on site or in the immediate vicinity. The site does not lie within an area classified as being susceptible to flooding. There were no surface water abstractions, discharge licenses, or pollution incidents identified within 500m of the site. 2.5 Sensitive Land Uses No such sensitive land uses were identified within a 250m radius of the site. 2.6 Industrial Land Uses No potentially contaminative land uses were identified on site or in the immediate vicinity. 2.7 Radon In accordance with BRE 211:2007, the site lies in an area where between 1% and 3% of homes exceed the government threshold for Radon gas in residential dwellings. A BGS report obtained by Land Science confirmed that basic Radon Protection Measures are required at this site. Basic Radon Protection Measures include the use of a well-constructed damp-proof membrane through wall cavities and beneath the floor scree. Such details should be shown on proposed construction drawings, and installation should be verified by the building inspector. Ground Investigation Page 9 of 19 *****************

10 2.8 Ground Gases A search waste treatment and disposal sites was undertaken as part of the desk study. Such sites may form an artificial source of land gases, such as Carbon Dioxide and Methane, where wastes are buried or disposed of to landfill. No such waste facilities or landfill sites were identified within a 1km radius of the site. The risk to the site is likely to be generally very low in this respect. In terms of land gases generated from natural sources, it was noted that the site was underlain by Chalk. The dissolution of carbonate cements by the infiltration of acidic waters may give rise to the generation of low levels of Carbon Dioxide. 2.9 Historical Data Historical maps dating back to 1870 were obtained as part of the desk study. A summary of the apparent key features noted on the map extracts both on the site and within the local area is presented on the table below. Date On Site Off Site 1870 The site comprises open land and a small area of woodland. The surrounding area comprises open land with small areas of woodland. Beech Farm is located to the north-west. A track runs along to the south of the site No significant changes noted. No significant changes noted ************* is indicated; the dwelling is not in the same location as the present day and lies within a parcel of land larger than the present day. The development plots fall within the associated gardens An ancillary building is noted to the north of the main property and a possible garage located to the south, adjacent to the drive A further small ancillary building has been developed adjacent to the north of the main building. The driveway appears to have been realigned onto land to the east Insufficient coverage. Insufficient coverage The dwelling appears to have been demolished and replaced with a new structure, commensurate with the present day house. Summary of Historical Map extracts Residential properties have been developed to the east and west. Further residential properties have been developed to the north and east. Beech Farm is now known as The Old Farm. Further residential properties are indicated in the immediate vicinity. The track to the south is now labelled *************. One residential property has been developed adjacent to the site. Ground Investigation Page 10 of 19 *****************

11 In summary, the site appeared to initially comprise open fields and woodland until c.1910, whereby the land fell within the grounds of *************. The dwelling was located to the west of the current existing property, close to the proposed location of the new dwelling on the upper plot. A number of outbuildings and a garage were shown on subsequent maps. The 1997 map shows the old dwelling to have been replaced with the current dwelling. The surrounding area comprised open land with small woodland/scrubland areas, with a farm (Beech Farm) located to the north-west up until c.1910 (later Beech Place). By c.1910, residential properties had been developed within the immediate vicinity of the site, with further dwellings being built after this date Previous Ground Investigations Land Science (Brighton) Ltd was not aware of any previous investigation that may have been undertaken on the site. Ground Investigation Page 11 of 19 *****************

12 3.0 CONCEPTUAL SITE MODEL The following sections summarise the anticipated environmental factors likely to impact upon the site in the context of the proposed redevelopment, in order to provide a justification and rationale for the subsequent phase II ground investigation. 3.1 Contamination Sources Possible sources of contamination identified or discounted as part of the desk study are summarised on the following table: Source Description Notes Land Gases Carbon Dioxide generated from the dissolution of carbonate cements Possible trace levels of Carbon Dioxide (CO 2 ). within the New Pit Chalk Formation. Radon Gas Naturally occurring Radon gas Basic Radon Protection Measures are required for new dwellings at this site. Possible Sources of Contamination 3.2 Identified Receptors Furthermore, potential receptors associated with the site and its redevelopment, identified or otherwise discounted, are summarised on the following table: Receptor Description Notes Site Workers Persons involved in construction and Major ground works are proposed future maintenance. including foundation excavation. End Users Occupants of the proposed redevelopment. Soft Landscaping Areas of planting including lawns, shrubs, trees, etc. Building Materials Elements of the built environment in direct contact with the ground. Adjacent Land Users Ground Water Possible Receptors of Contamination Sensitive land uses identified within the immediately vicinity Controlled Waters contained within the aquifer(s) beneath the site Residential development with private domestic gardens. Substantial areas of private soft landscaping are proposed. Buried plastics (e.g. water supplies) and concrete (e.g. foundations) may be laid. Residential gardens were identified immediately adjacent to the site. The site overlies a major aquifer and the site lies within a groundwater SPZ III (total catchment). Surface water and ecological receptors have not been identified as significant receptors. Ground Investigation Page 12 of 19 *****************

13 3.3 Source-Pathway-Receptor Linkages Whilst the various possible sources and receptors have been identified, the following matrix illustrates the identified pathways by which a contaminant linkage might plausibly exist: Source Land Gases Radon Gases Site Workers Asphyxiation None End Users None None Receptors Soft Landscaping None None Building Materials None None Adjacent Land Users Not applicable Not applicable Ground Water None None Identified Source-Pathway-Receptor linkages The proposed dwellings will include basic Radon Protection Measures. Such measures are also sufficient to protect against low concentrations of Carbon Dioxide. No other sources have been identified. As such no risks are posed to End Users. Radon Gas and Land Gases (Carbon Dioxide) will not pose a risk to soft landscaping, building materials, or groundwater, and pathways between off-site receptors and ubiquitous sources of contamination that exist both on-site and off-site are not applicable to this assessment. The concentrations of Radon Gas at this site are such that the workplace exposure limit set at 200Bq.m -3 is unlikely to be exceeded; thus no significant risk is posed in this respect. Whilst a plausible risk may exist with respect to trace levels of Carbon Dioxide and site personnel working in confined spaces such as deep excavations, pre-entry monitoring in accordance with Health and Safety requirements should ensure that any risks posed in this respect are adequately dealt with. 3.4 Environmental Investigation Strategy On the basis that no significant plausible source-pathway-receptor linkages have been identified, no environmental investigation was considered necessary. Deep excavation must be pre-monitored for Carbon Dioxide and Oxygen (amongst any other gases as identified by a confined space risk assessment) prior to personnel entry. Ground Investigation Page 13 of 19 *****************

14 4.0 ENCOUNTERED CONDITIONS A factual record of the conditions encountered during the physical investigation of the site is presented in the following sections. 4.1 Soils According to published information the anticipated geological succession beneath the site was indicated to comprise Lewes Nodular Chalk with a thin tract of Head Deposits in the southern lower part of the site. The investigation generally confirmed the anticipated geological succession. Topsoil was encountered in all window sampler boreholes, to depths in the range of 0.30m and 0.50mbgl. In summary, these materials generally comprised dark brown clayey sandy gravelly silt with rootlets. Head Deposits were encountered on the lower plot within WS2, WS3, the two further trial holes, and BH1, and were proved to a maximum depth of 2.70mbgl (within the trial holes). Generally these materials were identified as brown silty, sandy very gravelly CLAY (the gravel being fine to coarse angular flint). A further zone of similar materials was also encountered within WS6 to a depth of 2.80mbgl, close to the location of the garage at the upper plot. These materials may represent localised weathering of the underlying Chalk. The Lewes Nodular Chalk was encountered across the site from depths in the range of 0.30m to 2.80mbgl, and was proved to a maximum depth of 15.50mbgl within the cable percussive borehole. In the lower plot, the Chalk was noted to comprise white to light brown putty CHALK with limited proportions of gravel sized medium density Chalk fragments. In the upper plot, these materials were recovered as weak off-white gravel to cobble sized intact CHALK with horizons bearing limited proportions of weathered Chalk putty; the in-situ Chalk exposed in the ongoing excavation at the upper plot inspected during the second site visit was noted to be blocky and structured with widely spaced and open (<3mm) joints and occasional flint beds. 4.2 Groundwater Groundwater was not encountered during excavation of any of the investigative positions, and was not anticipated at shallow depth. 4.3 Obstructions No below ground artificial impenetrable solid obstructions were encountered during the fieldwork. 4.4 Geotechnical Field Testing Super Heavy Dynamic Probes were undertaken at positions WS1 and WS4. Ground Investigation Page 14 of 19 *****************

15 Generally the results from WS1 ranged between DP N =1 to DP N =13, (predominantly less than DP N =9, and averaging DP N =4); the values increased considerably between at 5.70m and 5.90m, and the probe was terminated at 5.90m upon a flint or similar. The results from WS4 generally ranged between DP N =3 to DP N =20 (predominantly less than DP N =12, averaging approximately DP N =8); the values increased considerably between 5.50m to 6.00m with the position being terminated at 6.00m. In-situ SPT tests were undertaken at 1.5m centres within the cable percussive borehole. A test result of SPT N =9 was obtained for the Head Deposits. For the Chalk, two identical results of SPT N =16 were obtained for the more weathered putty, increasing to between SPT N =18 and SPT N =41 within the more intact Chalk below 6.00m. 4.5 Geotechnical Laboratory Testing The results of two Particle Size Distribution determinations undertaken on the New Pit Chalk indicated the proportion of gravel was 32.9%-38.4%, sand 19.5%-24.6%, and silt/clay 36.9%-47.6 %. The laboratory description of this material was off white putty CHALK with occasional fine to medium intact chalk fragments. The results of two Particle Size Distribution determinations undertaken on the Head Deposits indicated the proportion of gravel was 43.3%-55.1%, sand 10.7%-12.5%, and silt/clay 34.2%-44.2%. The laboratory description of this material was brown sandy gravelly CLAY with occasional fine to medium chalk fragments (gravel is fine to medium and sub rounded to angular). Atterberg Limit analysis on a sample of the New Pit Chalk gave a plasticity index of 6% (or 3.1% when modified to account for the proportion passing the 425µm sieve). Within the Head Deposits, plasticity indexes ranged between 20% and 40%, or between 11.8% and 21.2% when modified to account for the proportion passing the 425µm sieve. Water soluble Sulphate determination were undertaken on a total of two samples of soil, with the results ranging between 0.09g/l and 0.10g/l; the accompanying ph results ranged between ph7.4 and 7.6. Elevated Sulphate and highly acidic soil is not generally associated with Chalk strata. Ground Investigation Page 15 of 19 *****************

16 5.0 ENGINEERING CONSIDERATIONS Subsequent to intrusive investigation of the site and receipt of the laboratory results, the following interpretative assessments have been made with respect to engineering considerations. 5.1 Traditional Foundations Based on the ground and groundwater conditions encountered within the boreholes on the upper (northern) plot, it is considered that traditional foundations are appropriate for the proposed development in that location. However, on account of the deep Head Deposits and soft weathered putty nature of the underlying Chalk, and on account of potential requirements for trench stability and heave precautions, it is recommended that an alternative foundation such as the use of piles is considered for the Lower (southern) plot. The following recommendations in respect of traditional foundations apply to the northern plot only. The Chalk should be treated as not being susceptible to volume change as defined by the NHBC Standards 4.2 (i.e. non shrinkable). Based on the in-situ testing results and typical settlement parameters for the types of soil encountered, a maximum net allowable bearing capacity of 150kPa is applicable to trench foundations taken through any Made Ground, soft or loose zones, or disturbed soils, and wholly into or onto the intact blocky Chalk of the Lewes Nodular Chalk Formation. This assessment includes an appropriate factor of safety against shear failure, and total settlements should remain within tolerable limits. A zone of Head Deposits was identified at WS6, outside the footprint of the proposed main dwelling structure but in close proximity to the nearby garage. The foundation excavations for the garage should be carefully inspected, and where Head Deposits are encountered it is recommended that either the widths are increased based on a maximum net allowable bearing capacity of 50kPa and foundation nominally reinforced, or that they are taken down onto the less weathered blocky Chalk. It should also be noted that the Head Deposits corresponded to a medium volume change potential as defined by the NHBC Standards, and that heave precautions would be required within the zone of influence of trees. It might be prudent to set out the foundations in this area and excavate a number of strategically placed trial holes prior to construction to assess ground conditions in this area. No evidence of solution features was noted on the site during the investigation. The site lies within an area where solution features may be present, and care should be taken during construction to identify any possible suspect soil conditions. Special precautions may be required where evidence of solution features is identified. Ground Investigation Page 16 of 19 *****************

17 5.2 Piled Foundations Piled foundations are recommended for the lower (southern) plot on account of the significant thicknesses of soft shrinkable Head Deposits and weathered Chalk. The construction of piled foundations is a specialist job and the advice of a reputable local contractor familiar with the type of ground and groundwater conditions encountered on this site should be sought prior to finalising the design. The actual working load for proposed piles will depend on the particular type of pile and method of installation adopted. The contractor should design piles in accordance with CIRIA Project Report 11, and in particular should adopt factors of safety of 2.5 and 5 on the skin friction and end bearing working loads respectively. For pile groups, the bearing value of each individual pile should be reduced by a factor of 0.8 and a calculation made to check for the factor of safety against block failure. All piles should be taken at least five times their diameter into the founding strata. Where bored piles are adopted, casing may be required in the upper sections to prevent necking. In accordance with the NHBC Standards, heave precautions may be required on the upper portions of piles and on ground beams within the zone of influence of trees, and the piles should be designed to resist uplift forces that may develop. 5.3 Ground Floor Slabs Ground floor slabs on the upper dwelling may be constructed as ground bearing, with a maximum net allowable bearing capacity of 25kN/m 2. The sub-grade should be carefully proof rolled and any soft or loose zones replaced with compacted granular engineering fill. The use of a ground bearing floor slab for the garage at the upper plot will depend on ground conditions exposed at the formation level; where significant thicknesses of Head Deposits are encountered it would be necessary to adopt a suspended ground floor slab. On account of the soil conditions at the lower plot, ground floor slabs should be fully suspended. 5.4 Excavations Excavations within the Head Deposits may be generally stable in the short term, being susceptible to possible localised spalling and collapse; shallow trenches to be left open for short periods may simply be battered back to a safe angle, whilst appropriate trench support should be considered for deeper trenches to be left open for prolonged periods. Excavations within the Chalk should remain generally stable. 5.5 Retaining Walls and Slope Stability A number of retaining walls are proposed, independent of the building construction, in order to accommodate the new dwellings. A full engineering assessment of slope stability issues was outside the scope of this report, although the following advice is given for preliminary purposes. Ground Investigation Page 17 of 19 *****************

18 The excavations for the retaining walls at the upper plot had already been commenced at the time of the second site visit by Land Science. The cut face was up to approximately m in height, and exposed blocky and structured Chalk with broadly horizontal widely spaced and open (<3mm) joints and occasional flint beds. Whilst cut faces in structured blocky Chalk can stand near vertically, there are issues with long-term instability associated with spalling, issues related to weathering and surface protection, and issues associated with serviceability. Where a cut slope is to be incorporated into the final landscaping design, the angle should not exceed 60 O and faces should be provided with a basic surface protection to prevent spalling and weathering; above this angle, it is recommended that a basic form of retaining wall is constructed. Retaining walls approximately 1.50m in height are also required at the rear of the lower plot, involving excavation along the toe of the slope, and special care and consideration should be given when designing the associated temporary and permanent works. Materials in this area comprise a mixture of weathered putty Chalk and soft Head Deposits, and it is likely that some form of embedded retaining wall would be most appropriate. With reference to BS8002:2004, parameters for retaining wall design in Head Deposits have been assessed as follows: Parameter Value Co-efficient of active earth pressure (K a ) 0.28 Co-efficient of passive earth pressure (K p ) 5.0 Saturated bulk density (γ) 18.0 Angle of shearing resistance of the soil (φ ) Preliminary retaining wall design parameters These values are based on a number of critical assumptions, which must be checked and verified as part of the actual retaining wall design: 30 O o o o Angle of shearing resistance between the ground and the wall, δ = 20 O The surface of the ground level to the rear of the wall is inclined at an angle, ß = 30 O The retained soil may be characterised as a firm clay 5.5 Pavements Given the variability of the likely sub-grade, it is recommended that the formation should be treated as being frost susceptible for pavement design purposes, and therefore a minimum pavement thickness of 450mm adopted. The formation should be carefully proof rolled and any soft or loose zones replaced with well compacted granular fill. 5.6 Building Materials The results of the Sulphate and ph analyses fell into Class DS-1 of the current revision of BRE Special Digest 1. An ACEC class of AC-1 is appropriate based on the ph results and known site history. The advice of this publication should be taken for the design and specification of all sub surface concrete. Ground Investigation Page 18 of 19 *****************

19 5.7 Soakaways Preliminary falling head soakage tests were undertaken within WS3 and WS6, which gave infiltration rates of 1.4x10-4 m.s -1 and 5.8x10-6 m.s -1 respectively. Both boreholes were drilled through Head Deposits with Chalk towards the base; the higher result in WS3 may be on account of more granular materials within the Head Deposits. Given this variability, soakaways constructed into the Head Deposits should be designed based on the more conservative lower infiltration rate of 5.8x10-6 m.s -1. Higher infiltration rates may be realised within the blocky fissured Chalk. Should improve infiltration rates be required, it would be necessary to conduct full-scale soakage tests in accordance with BRE365. Given the sites location within a groundwater Source Protection Zone, and in order to protect groundwater resources, the Environment Agency might have special requirements for the design of soakaways including water seals, closed surface entries or interceptors. The consideration of the Agency should be sought in this respect. Concentrated discharges into the Chalk from surface water drainage may cause the dissolution of carbonate cements within rock matrix, which may in turn lead to voiding, instability, and surface collapse. Such discharges may also potentially reactivate any inactive dissolution features. It is therefore recommended that all soakaways be located a minimum of 10m distant from any sensitive structures. Finally, soakaways should be carefully positioned so as to avoid concentrated point discharges close to the existing slope, as this may cause instability. Ground Investigation Page 19 of 19 *****************

20 TITLE: Site Location Plans REF: LS0237 PROJECT: VERSION v1 CLIENT: FIGURE: 1 PREPARED: CHECK: DATE: SHEET No: SR ET 29/10/2010 page: 1 of 1 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

21 WS4 WS5 WS6 WS1 BH1 WS2 WS3 TITLE: Investigation Layout Plans REF: LS0237 PROJECT: ************************** VERSION v1 CLIENT: ************************** FIGURE: 1 PREPARED: CHECK: DATE: SHEET No: SR ET 29/10/2010 page: 1 of 1 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

22 APPENDIX A

23 TITLE: 1870 Historical Map 1:2500 REF: LS0237 PROJECT: ************** VERSION v1 CLIENT: ************** FIGURE: 1 PREPARED: CHECK: DATE: SHEET No: SR ET 30/11/2010 page: 1 of 1 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

24 TITLE: PROJECT: CLIENT: 1896 Historical Map 1:2500 REF: LS0237 ************** VERSION v1 ************** FIGURE: 1 PREPARED: CHECK: DATE: SHEET No: SR ET 30/11/2010 page: 1 of 1 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

25 TITLE: PROJECT: CLIENT: 1910 Historical Map 1:2500 REF: LS0237 ************** VERSION v1 ************** FIGURE: 1 PREPARED: CHECK: DATE: SHEET No: SR ET 30/11/2010 page: 1 of 1 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

26 TITLE: PROJECT: CLIENT: PREPARED: REF: 1939 Historical Map 1:2500 VERSION ************** FIGURE: ************** SR LS0237 CHECK: ET DATE: 30/11/2010 v1 1 SHEET No: page: 1 of 1 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

27 TITLE: PROJECT: CLIENT: 1977 Historical Map 1:2500 REF: LS0237 ************** VERSION v1 ************** FIGURE: 1 PREPARED: CHECK: DATE: SHEET No: SR ET 30/11/2010 page: 1 of 1 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

28 TITLE: PROJECT: CLIENT: 1997 Historical Map 1:2500 REF: LS0237 ************** VERSION v1 ************** FIGURE: 1 PREPARED: CHECK: DATE: SHEET No: SR ET 30/11/2010 page: 1 of 1 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

29 APPENDIX B

30 DESCRIPTION TESTING SAMPLING Dark brown SILT with fine to coarse angular gravel and cobbles, and rootlets. (TOPSOIL) D D WATER FILL Weak white and occasional light brown putty CHALK with layers of gravel sized medium density chalk fragments. (LEWES NODULAR CHALK MEMBER) D D D D D D D D D Continued on next page REMARKS TITLE: REFERENCE: POSITION: Stability: No instability encountered Borehole log LS0237 Groundwater: No groundwater encountered PROJECT: ELEVATION: CO-ORDINATES: Chiselling: Not applicable ************** N/A Not to scale CLIENT: METHOD: Casing/dia: Not recorded ************** Archway "Dart" Windowless Sampler Backfilling: Position backfilled with arisings DRILLED BY: LOGGED BY: STARTED: SCALE: Obstructions: No obstructions encountered AA DRILLING SR 09/11/2009 Not to scale INPUTTED BY: CHECKED BY: COMPLETED: SHEET No: Others: Hand excavated to 0.40mbgl SR ET 09/11/2009 Page: 1 of 2 WS1 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

31 DESCRIPTION TESTING SAMPLING WATER Continued..Weak white and occasional light brown putty CHALK with layers of gravel sized medium density chalk fragments. (LEWES NODULAR CHALK MEMBER) D FILL D Borehole complete at 6.00m REMARKS TITLE: REFERENCE: POSITION: Stability: No instability encountered Borehole log LS0237 WS1 Groundwater: No groundwater encountered PROJECT: ELEVATION: CO-ORDINATES: Chiselling: Not applicable ************** N/A Not to scale CLIENT: METHOD: Casing/dia: Not recorded ************** Archway "Dart" Windowless Sampler Backfilling: Position backfilled with arisings DRILLED BY: LOGGED BY: STARTED: SCALE: Obstructions: No obstructions encountered AA DRILLING SR 09/11/2009 Not to scale INPUTTED BY: CHECKED BY: COMPLETED: SHEET No: Others: Hand excavated to 0.50mbgl SR ET 09/11/2009 Page: 2 of 2 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

32 DESCRIPTION Dark brown clayey SILT with rootlets. (TOPSOIL) TESTING SAMPLING D WATER FILL Brown silty, sandy gravelly CLAY. (HEAD DEPOSITS) D D Off white slightly weathered CHALK, very weak. Structurless mélange composed of 70% subangular medium to coarse gravel sized fragments set in 30% soft, off white chalk matrix; Grade Dc. (LEWES NODULAR CHALK MEMBER) Off white CHALK, medium to high density. Discontinuities very closely spaced (20mm), open (<3mm); medium to high density Grade B5. (LEWES NODULAR CHALK MEMBER) D D D D D Borehole complete at 3.00m REMARKS TITLE: REFERENCE: POSITION: Stability: No instability encountered Borehole log LS0237 WS2 Groundwater: No groundwater encountered PROJECT: ELEVATION: CO-ORDINATES: Chiselling: Not applicable ************** N/A Not to scale CLIENT: METHOD: Casing/dia: Not recorded ************** Archway "Dart" Windowless Sampler Backfilling: Position backfilled with arisings DRILLED BY: LOGGED BY: STARTED: SCALE: Obstructions: No obstructions encountered AA DRILLING SR 09/11/2009 Not to scale INPUTTED BY: CHECKED BY: COMPLETED: SHEET No: Others: Hand excavated to 0.30mbgl SR ET 09/11/2009 Page: 1 of 1 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

33 DESCRIPTION TESTING SAMPLING WATER D Dark brown wood chippings. (TOPSOIL) FILL Brown silty, sandy slighty gravelly CLAY with fine to medium angular chalk. (HEAD DEPOSITS) Light brown silty sandy very gravelly CLAY. Gravel is fine to coarse angular flint. (HEAD DEPOSITS) D D D Brown clayey silty sandy GRAVEL. Gravel is fine to coarse angular flint. (HEAD DEPOSITS) D Brown silty sandy very gravelly CLAY. Gravel is fine to coarse angular flint. (HEAD DEPOSITS) D Off white slightly weathered. CHALK, weak. Structureless D mélange composed of 80% subangular to rounded medium to coarse high density grzel sized fragments set in 20% soft, off 3.00 white, silt sized chalk matrix; Grade Dc. (LEWES NODUALR CHALK MEMBER) Borehole complete at 3.00m. REMARKS TITLE: REFERENCE: POSITION: Stability: No instability encountered Borehole log LS0237 WS3 Groundwater: No groundwater encountered PROJECT: ELEVATION: CO-ORDINATES: Chiselling: Not applicable ************** N/A Not to scale CLIENT: METHOD: Casing/dia: Not recorded ************** Archway "Dart" Windowless Sampler Backfilling: Position backfilled with arisings DRILLED BY: LOGGED BY: STARTED: SCALE: Obstructions: No obstructions encountered AA DRILLING SR 09/11/2009 Not to scale INPUTTED BY: CHECKED BY: COMPLETED: SHEET No: Others: Hand excavated to 0.40mbgl SR ET 09/11/2009 Page: 1 of 1 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

34 DESCRIPTION TESTING SAMPLING WATER Loose dark brown clayey sandy SILT with rootlets and occasional fine to coarse gravel sized angular chalk. (TOPSOIL) Off white CHALK, weak with high density chalk fragments. Discontinuities closely spaced (20-60mm), open (<3mm); high D density Grade B5. (LEWES NODUALR CHALK MEMBER) D FILL D White CHALK, medium density. Discontinuities very closely spaced (<20mm), open (<3mm); medium density Grade B5. (LEWES NODUALR CHALK MEMBER) D D Off white CHALK, weak. Structureless mélange composed of 80% subangular to rounded, low density chalk fragments set in 20% soft, off white, silt size chalk matrix; Grade Dc. (LEWES NODUALR CHALK MEMBER) D D White CHALK, very weak. Structureless mélange composed of 20% subangular to rounded medium sized fragments set in 80% soft, off white/brown silt size chalk matrix; Grade Dm. (LEWES NODUALR CHALK MEMBER) D D Continued on next page 5.00 REMARKS TITLE: REFERENCE: POSITION: Stability: No instability encountered Borehole log LS0237 WS4 Groundwater: No groundwater encountered PROJECT: ELEVATION: CO-ORDINATES: Chiselling: Not applicable ************** N/A Not to scale CLIENT: METHOD: Casing/dia: Not recorded ************** Archway "Dart" Windowless Sampler Backfilling: Position backfilled with arisings DRILLED BY: LOGGED BY: STARTED: SCALE: Obstructions: No obstructions encountered AA DRILLING SR 09/11/2009 Not to scale INPUTTED BY: CHECKED BY: COMPLETED: SHEET No: Others: Hand excavated to 0.30mbgl SR ET 09/11/2009 Page: 1 of 2 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

35 DESCRIPTION TESTING SAMPLING WATER Continued White CHALK, very weak. Structureless mélange composed of 20% subangular to rounded medium sized fragments set in 80% soft, off white/brown silt size chalk matrix; Grade Dm. (LEWES NODUALR CHALK MEMBER) D FILL Borehole complete at 6.00m REMARKS TITLE: REFERENCE: POSITION: Stability: No instability encountered Borehole log LS0237 WS4 Groundwater: No groundwater encountered PROJECT: ELEVATION: CO-ORDINATES: Chiselling: Not applicable ************** N/A Not to scale CLIENT: METHOD: Casing/dia: Not recorded ************** Archway "Dart" Windowless Sampler Backfilling: Position backfilled with arisings DRILLED BY: LOGGED BY: STARTED: SCALE: Obstructions: No obstructions encountered AA DRILLING SR 09/11/2009 Not to scale INPUTTED BY: CHECKED BY: COMPLETED: SHEET No: Others: Hand excavated to 0.30mbgl SR ET 09/11/2009 Page: 2 of 2 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

36 DESCRIPTION TESTING SAMPLING WATER Loose light brown clayey sandy gravelly SILT with rootlets. Gravel is fine to coarse chalk and brick. (MADE GROUND) D FILL Off white, slightly weathered CHALK, weak. Structureless mélange composed of 80% medium to coarse high density chalk fragments set in 20% soft, brown silt size chalk matrix; Grade Dc. (LEWES NODUALR CHALK MEMBER) Off white CHALK, strong, high density. Discontinuities closely spaced (20-60mm), open (<3mm); High density Grade B4. (LEWES NODUALR CHALK MEMBER) D D D Off white/grey very high density gravel of CHALK. (LEWES NODUALR CHALK MEMBER) D 2.30 Off white CHALK, strong, high density. Discontinuities very closely spaced (<20mm), open (<3mm); High density Grade B4. (LEWES NODUALR CHALK MEMBER) D Borehole complete at 3.00m REMARKS TITLE: REFERENCE: POSITION: Stability: No instability encountered Borehole log LS0237 WS5 Groundwater: No groundwater encountered PROJECT: ELEVATION: CO-ORDINATES: Chiselling: Not applicable ************** N/A Not to scale CLIENT: METHOD: Casing/dia: Not recorded ************** Archway "Dart" Windowless Sampler Backfilling: Position backfilled with arisings DRILLED BY: LOGGED BY: STARTED: SCALE: Obstructions: No obstructions encountered AA DRILLING SR 09/11/2009 Not to scale INPUTTED BY: CHECKED BY: COMPLETED: SHEET No: Others: Hand excavated to 0.50mbgl SR ET 09/11/2009 Page: 1 of 1 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

37 DESCRIPTION TESTING SAMPLING WATER Loose dark brown silty sandy gravelly CLAY with rootlets. Gravel is fine to coarse chalk. (TOPSOIL) D FILL Brown silty sandy very gravelly CLAY with rootlets. Gravel is fine to coarse angular and sub rounded flint and chalk. (HEAD DEPOSITS) D Brown very silty sandy slightly gravelly CLAY. Gravel is fine to coarse angular to sub rounded flint and chalk. (HEAD DEPOSITS) D D Brown silty sandy very gravelly CLAY with rootlets. Gravel is fine to coarse angular and sub rounded flint and chalk. (HEAD DEPOSITS) D Off white, slightly weathered CHALK, low density. Discontinuities very closely spaced (<20mm), open (<3mm); Low density Grade B5. (LEWES NODULAR CHALK MEMBER) Borehole complete at 3.00m D 3.00 REMARKS TITLE: REFERENCE: POSITION: Stability: No instability encountered Borehole log LS0237 WS6 Groundwater: No groundwater encountered PROJECT: ELEVATION: CO-ORDINATES: Chiselling: Not applicable ************** N/A Not to scale CLIENT: METHOD: Casing/dia: Not recorded ************** Archway "Dart" Windowless Sampler Backfilling: Position backfilled with arisings DRILLED BY: LOGGED BY: STARTED: SCALE: Obstructions: No obstructions encountered AA DRILLING SR 09/11/2009 Not to scale INPUTTED BY: CHECKED BY: COMPLETED: SHEET No: Others: Hand excavated to 0.50mbgl SR ET 09/11/2009 Page: 1 of 1 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK

38 Interval DP N 100 Interval DP N 100 m blows/100mm m blows/100mm * fell under own weight * to 0.40m * * position terminated at 5.9m TITLE: PROJECT: CLIENT: Hammer mass 63.5 kg Rod weight 6 kg Date Completed 09/11/2010 Gravity constant 9.8 N/kg Base of cone m 2 Ground level Not available height of fall m Friction correction None Drilling rig Archway Dart Anvil weight 30 kg Friction precautions None Contractor AA Drilling Methodology EN DD1997-3:1999 "Eurocode 7 : Geotechnical Design - design assisted by field testing", Clause 6 Remarks No interuptions. No calibration data. Super Heavy Dynamic Probing (SHDP) record POSITION: *********** WS1 GRID REF: *********** N/A OPERATIVES: CHECKED: DATE: SHEET: AJ/TR ET 18/11/ of 1 REF: LS0237 CARLTON HOUSE, CARLTON TERRACE, PORTSLADE, BRIGHTON, BN41 1UR TEL: FAX: BRIGHTON@LANDSCIENCE.CO.UK