Geoenvironmental Report FINAL - East Staffordshire · APPENDIX C – DESK STUDY CORRESPONDENCE APPENDIX D – EAST STAFFORDSHIRE BOROUGH COUNCIL REPORT ... • Kitling Greaves Lane

ES 6Upper Outwoods, Burton upon Trent, Staffordshire

ENVIRONMENTAL STATEMENT

Volume 6: Geoenvironmental

Appraisal

Outline Planning Application

January 2012

wendy.keach

Text Box

P/2013/00429 Received 12/04/2013

Geoenvironmental Appraisal – October 2008

Report: C2852- Upper Outwoods Farm, Burton-on Trent. Prepared For: Hallam Land Management Ltd.

GEOENVIRONMENTAL APPRAISAL

OF LAND at

UPPER OUTWOODS FARM,

BURTON-ON-TRENT

PREPARED FOR

HALLAM LAND MANAGEMENT LIMITED

CONTENTS

1.0 INTRODUCTION....................................................................................................................1 2.0 SITE DESCRIPTION..............................................................................................................1 3.0 ENVIRONMENTAL SETTING. ..............................................................................................2

3.1 Site History..................................................................................................................................................2 3.2 Geology. ......................................................................................................................................................4 3.3 Mining and Quarrying. ...............................................................................................................................4 3.4 Hydrology/Hydrogeology...........................................................................................................................5 3.5 Landfill Search............................................................................................................................................6 3.6 Radon...........................................................................................................................................................7

5.0 PRELIMINARY CONCEPTUAL SITE MODEL......................................................................7 5.1 General. .......................................................................................................................................................7 5.2 Potential Sources of Contamination. .......................................................................................................7 5.3 Potential Pathways for Contamination.....................................................................................................8 5.4 Potential Receptors....................................................................................................................................8

6.0 FIELDWORK. ......................................................................................................................10 6.1 Introduction...............................................................................................................................................10 6.2 Scope of Works. .......................................................................................................................................11 6.3 Strata Description.....................................................................................................................................11 6.4 Sampling and Insitu Testing. ..................................................................................................................12

7.0 GROUND CONDITIONS AND MATERIAL PROPERTIES. ................................................12 7.1 Made Ground. ...........................................................................................................................................13 7.2 Residual Soil. ............................................................................................................................................14 7.3 Bedrock .....................................................................................................................................................14 7.4 Groundwater. ............................................................................................................................................14 7.5 Visual / Olfactory Evidence of Contamination. .....................................................................................14

8.0 CONTAMINATION ASSESSMENT. ....................................................................................15 8.1 General. .....................................................................................................................................................15 8.2 Testing Schedule......................................................................................................................................15 8.3 Current Guidance and the Interpretation of Analytical Data................................................................16 8.4 Chemical Results and Generic Quantitative Risk Assessment...........................................................17 8.5 Reassessment of Site Conceptual Model. .............................................................................................22

9.0 HAZARDOUS GAS MONITORING. ....................................................................................25 9.1 General. .....................................................................................................................................................25 9.2 Monitoring Procedure. .............................................................................................................................26 9.3 Results.......................................................................................................................................................26 9.4 Discussion. ...............................................................................................................................................26

10.0 CONCLUSIONS AND RECOMMENDATIONS..................................................................28

Geoenvironmental Appraisal – October 2008


10.1 Mining and Quarrying. ...........................................................................................................................28 10.2 Contamination Constraints to Development. ......................................................................................28 10.3 Hazardous Gas. ......................................................................................................................................28

APPENDICES APPENDIX A – DRAWINGS

Drawing No Drawing Title C2852/1 Site Location Plan C2852/2 Preliminary Conceptual Site Model C2852/3 Exploratory Hole Location Plan C2852/4 Post Development Conceptual Site Model

APPENDIX B – GROUNDSURE REPORT APPENDIX C – DESK STUDY CORRESPONDENCE APPENDIX D – EAST STAFFORDSHIRE BOROUGH COUNCIL REPORT APPENDIX E – EXPLORATORY HOLE LOGS APPENDIX F – CHEMICAL ANALYSIS APPENDIX G - GAS MONITORING

Geoenvironmental Appraisal –October 2008 Page 1 of 29


1.0 INTRODUCTION. Sirius Geotechnical and Environmental Ltd. (Sirius) was commissioned by Hallam Land Management Ltd. to undertake a Geoenvironmental Appraisal of land at Upper Outwoods Farm, Burton-on-Trent, Staffordshire. The site is currently in use as a farm of mixed arable and livestock land usage. The works were undertaken to provide environmental and gas risk information regarding a series of infilled marl pits located across the farm. It is understood that consideration is being given to the redevelopment of the entire site for mixed end use including residential and commercial together with sports provision and sustainable drainage features. If this is not the case significant amendments to the conclusions and recommendations presented in this report may be required. The fieldwork was carried out between the 23rd April and the 25th April 2008 and comprised five cable percussive boreholes and nineteen window sample holes. Combined gas/groundwater monitoring wells were installed in each cable percussive borehole and in seventeen window sample holes. Following completion of the fieldwork, selected soil and water samples were scheduled for a range of geotechnical and chemical analyses. A gas/groundwater monitoring regime has been completed.

This report presents the factual information derived during this investigation, followed by an interpretation of this data and recommendations relating to the proposed end use of the site. Where the report refers to the potential presence of invasive plants 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. The comments and opinions presented in this report are based on the findings of a review of available information, ground conditions encountered during the intrusive investigation work and on the results of tests carried out in the laboratory. There may be other conditions prevailing on the site which have not been disclosed by this investigation and which have not been taken into account by this report. Responsibility cannot be accepted for conditions not revealed by the investigation. Any diagram or opinion of the possible configuration of ground conditions between exploratory holes is conjectural and given for guidance only and confirmation of intermediate ground conditions should be considered if deemed necessary.

2.0 SITE DESCRIPTION. Table 1: Site Description

National Grid Ref:

422850 325514

Site Location The site is located off Beamhill Road, approximately 3.0km to the north west of Burton town centre. The location of the site is shown on Drawing No. C2852/1, presented in Appendix A to this report.

Approximate 49.1 (121.4)



Site Area – Hectares (acres)

Site Description The site straddles a small valley. From the north, the land slopes gently downhill to the stream that flows west-east across the centre of the site. The slope rising to the southern boundary is substantially steeper. The only buildings are the farm house and associated farm buildings (byre, barn, storage shed etc.), all clustered in the west of the site adjacent to the stream. The land use is a mix of wheat fields and grazing land for cattle. Some low lying areas of the site have been planted with saplings.

Fuel Storage Tanks

No ASTs were present in the area of investigation.

Adjacent Land Uses

The site is in an area of mixed land use, with residential areas to the north and east and agricultural land to the south and west.

3.0 ENVIRONMENTAL SETTING.

3.1 Site History. In order to investigate the history of the site, extracts of Ordnance Survey (OS) plans dated from 1882 to 2005 have been examined. Copies of all of the plans referenced are presented in Appendix B. Table 2 gives a summary of the salient points relating to the history of the site from 1882 with respect to the proposed end use. It is not the intention of this report to describe in detail all the changes that have occurred on or adjacent to the site, only those pertinent to the proposed development. Table 2: Historical Features

OS Map Edition Date Scale

On-site Features Off-site Features

1882 1:10,560 • A building is shown in the current location of the farm house.

• The site is divided into approximately 30 separate parcels of land.

• A stream is shown trending west-east along the centre of the site.

• Kitling Greaves Lane follows the north bank of the stream across the eastern two-thirds of the site.

• Five old clay and marl pits are shown in the southern half of the site.

• A road lies 50m north, running parallel to the northern site boundary.

• Field Lane comes within 50m of the south east site boundary.

• A Methodist chapel and a small cluster of houses are shown 60m from the north west corner of the site.

• Highfield House is shown 60m from the south east corner of the site.

• Old clay and marl pits are shown throughout the area, the closest being 30m to the south of the southern boundary.

• A brick yard is shown 450m west. • A village is shown 500m east (named





Horninglow in later maps). • A brewery is shown 600m east in

Horninglow.

1883-1884 1:2,500 • Two small buildings are shown north of the farm house.

• No significant changes.

1900 1:10,560 • No significant changes • An isolation hospital, mortuary and covered reservoir are shown 300m south.

• A hospital has been constructed 650m south adjacent to a ‘Union Workhouse’.

• A Burton upon Trent Corporation sewage tank is shown 450m east.

• The brick yard 450m west is now named ‘Anslow Brick Works’.

• Horninglow has expanded with new housing, a Sunday School and pumping station constructed 500m southeast.

1901 1:2,500 • Allotment gardens are shown within a small single field division straddling the north boundary of the site.

• No significant changes

1920-1924 1:10,560 • Two small farm buildings have been erected to the immediate west and south west of the existing farm house.

• The area between the mortuary and Horninglow village is now shown as allotment gardens.

• The Union Workhouse is now shown as ‘Burton Upon Trent Poor Law Institution’.

• The sewage tank east of the site is no longer shown.

1923 1:2,500 • Several additional small buildings have been constructed around the farm house.


1924 1:10,560 • No significant changes.


1937-1938 1:2,500 • Several additional buildings have been constructed around the farm house.

• A ‘windpump’ is shown in the south-centre of the site.

• Houses have been constructed along Beamhill Road to the north, Field Lane to the south, and Kitling Greaves Lane to the east.

1938 1:10,560 • No significant changes. • Increase in size of Horninglow village with the construction of Westfield Road, Rowton Street and Longmead Road.

1949 1:10,560 • Site not shown. • Majority of allotment garden space given over to housing.

1949-1951 1:10,560 • No significant changes. • Housing constructed along Beamhill Road directly adjacent to the northwest border of the site.

• The A38 has been constructed 1km southeast of the site.





1951 1:2,500 • Only eastern third of site shown on plan.



1971-1972 1:2,500 • Only eastern third of site shown. • No significant changes

• Further housing built 100m north and 200m south east of the site.

1973 1:10,000 • A tank is shown 60m south of the wind pump near the southern site boundary.

• The last of the allotment gardens has been given over to housing.

• Three schools have been constructed on land 300m east.

1990-1993 1:10,000 • No significant changes. • No significant changes.

1996 1:2,500 • No significant changes • No significant changes.

2002 1:10,000 • The tank south of the wind pump is no longer shown.


2005 1:10,000 • No significant changes. • No significant changes.

3.2 Geology. Table 3: Summary of Geological Information

Maps/ Publications Referenced

BGS 1:50,000 scale Geology Map – Sheet 140 Solid and Drift Edition

Drift Geology No drift deposits shown.

Solid Geology Mercia Mudstone (Triassic) dipping at 2° to the south west.

Encountered Geology Thin veneer of topsoil overlying weathered mudstone/siltstone. Solid geology encountered in two locations (brown mudstone in WS7 at 1.90m and brown siltstone in WS9 at 2.90m). The GroundSure Report states the following potentials for ground stability hazards on site:

• Maximum Shrink-Swell hazard rating – very low. • Maximum Landslide hazard rating – moderate. • Maximum Soluble Rocks hazard rating – negligible. • Maximum Compressible Ground hazard rating – negligible. • Maximum Collapsible Rocks hazard – nul - negligible. • Maximum Running Sand hazard – negligible.

3.3 Mining and Quarrying.



Mining The site is not located within an area likely to be affected by coal mining and therefore a coal authority report was not required in accordance with the Law Society Guidance Notes. Information was sought from British Gypsum regarding potential mining issues relating to gypsum and anhydrite extraction beneath the site. They stated that there are no gypsum mine workings in the vicinity and to the best of their knowledge, there has not been any mining of gypsum and anhydrite under the property. Furthermore, the site does not lie within the present planning consent area for underground mining. Quarrying The site lies in an area of extensive marl/clay extraction. Several ‘old marl pits’ are shown onsite, and immediately offsite, in the historical maps, the locations of which can be seen in drawing no. C2852/3 in Appendix A to this report.

3.4 Hydrology/Hydrogeology. Surface Water The nearest surface water is a stream running west-east across the centre of the site at the base of the broad valley. The Environment Agency has no information on river quality within 500m of the site. The GroundSure report identifies no surface water abstraction licenses within 1000m of the site. No source protection zones are found within 500m of the site. No potable water abstraction licenses are found within 2000m of the site. The GroundSure Report reveals four licensed discharge consents within 500m of the site. The first is listed 267m south west at Glen Holme, Field Lane. The effluent type is listed as ‘sewage discharges – final/treated effluent – not water company’. The receiving water is given as Trib River Trent &/or land. Two licensed discharge consents are listed as Tutbury Road Storm Overflow. The first is placed 314m east and the second 326m east. Assigned separate permit numbers, they are both listed as ‘sewage discharges – sewer storm overflow – water company’. The receiving water in both cases is Kitling Greaves Brook. The fourth consent is listed 320m west at Outwoods Lane, Anslow. The effluent type is given as ‘sewage discharges – final/treated effluent – not water company’. The GroundSure report lists one Environment Agency Recorded Pollution Incident (Incident Identification 166701). Dated June 17th 2003, it occurred on site and is listed as a category 3 (minor) impact to water. The incident had no impact to air or land. According to the GroundSure Report the site does not lie within 250m of any Environmental Agency Zone 2 or Zone 3 floodplains.



Groundwater The Mercia Mudstone strata which underlie the site are classed as a non aquifer by the EA. These are defined as: “Formations which are generally regarded as containing insignificant quantities of groundwater. However, flow through such rocks, although imperceptible, does take place and needs to be considered in assessing the risk associated with persistent pollutants”. No drift deposits are shown to lie beneath the site. Information sought from GroundSure indicates that the EA has seven records of active licensed groundwater abstractions within 1km of the site. Two abstractions are within the site boundary, detailed for general farming and domestic use. The first relates to the windpump and well located south of Kitling Greaves Lane. The second relates to a well at Upper Outwoods Farm. The nearest off-site abstraction is located at Wyggeston Street Well 693m south east, detailed as either ‘evaporative cooling’ or ‘process water’. Further groundwater abstractions are located 861m east, 877m south east, 888m south east and 960m south east. Full details are presented in Appendix B to this report.

3.5 Landfill Search. Information on landfill sites in the vicinity of the property was sought from GroundSure. This includes information derived from the Environment Agency and BGS. A copy of the GroundSure Report is presented as Appendix B to this report. According to the GroundSure Report there are two Environment Agency historic landfill locations onsite and a further two located within 500m of the site. There is no data regarding the waste material in the first landfill although anecdotal evidence suggests that it is household waste. The second landfill, named Cockpitt Tip is recorded as containing industrial and household waste. It should be noted that there is a discrepancy between the locations of Cockpitt Tip as shown in the GroundSure Report and information sourced from East Staffordshire Borough Council. The current landowner was present at the time the landfill was in use and confirmed that the information supplied by GroundSure is accurate. The landowner was further able to delineate the extent of the landfill on the ground. The nearest landfill outside the site boundary is recorded as being located 59m north, on the far side of Beamhill Road. It is recorded to contain household waste. A fourth recorded landfill is situated at Denton Road Development 167m south east and contains industrial waste. A copy of the East Staffordshire Borough Council search is included as Appendix D to this report.



3.6 Radon. To determine whether the site is at risk from Radon gas the BRE document “Radon: Guidance on Protective Measures for New Buildings (2007)” and the NRPB document “Radon Atlas of England and Wales (2002)” have been referenced. Both documents indicate that the site is in an area where no radon gas protection measures are currently required.

5.0 PRELIMINARY CONCEPTUAL SITE MODEL

5.1 General. The first stage in assessing the potential risks from contaminated land is to develop a conceptual model of the site. The UK approach to risk assessment is based on the contaminant-pathway-receptor scenario. In order for there to be a risk from contamination, there must be a contaminant, a receptor (an entity which might be affected by the contamination) and a mechanism or pathway by which the receptor can be exposed to the contaminant. Potential sources of contamination are usually associated with current and historical industrial activities, where the processing, storage, use, transportation and disposal of raw materials, products and waste often leads to contamination of the underlying ground. In addition to industrial processes, natural processes can also give rise to contamination, such as hazardous gases and elevated concentrations of heavy metals etc. Potential pathways can include permeable ground conditions, underground voids, services, groundwater and surface water. The mechanisms by which a receptor can be exposed to a contaminant can include direct contact, ingestion / uptake and inhalation. Potential receptors can include human health, environmental receptors (including controlled waters) and buildings or structures. In order to develop a site specific conceptual model, a review of the current and historical land uses in the area and the site's environmental setting has been carried out to identify the potential contaminants, pathways and receptors. The preliminary conceptual site model (PCSM) detailed below is based on the site’s current state and all available information for assessment and interpretation. A diagrammatical representation of the preliminary conceptual site model is shown in drawing no C2852/2 in Appendix A

5.2 Potential Sources of Contamination.

On Site Sources The historical maps for the site show a series of old marl pits across the extent of the site (cf. C2852/2). According to the GroundSure Report and anecdotal evidence, these have been backfilled with a mixture of industrial and household waste. This backfilling took place during the lifetime of the current landowner who was able to delineate the former pits on the ground



and to give an estimate of the depths of the former pits. A slight depression was often visible in these areas. The current landowner commented that although domestic refuse was placed, and recalls refuse wagons visiting the site to deposit waste, the majority of the waste at the time (pre Clean Air Act) was of ash. As the source of the waste is unknown, the types of contaminant potentially present can not be surmised and a range of organic and inorganic contaminants may be present. The made ground in addition may have the potential for generation of ground gases (methane and carbon dioxide) with associated explosion and asphyxiation risks. Owing to the unknown nature of the made ground, it is considered that the likelihood of contamination being present on the site may be moderate.

Off Site Sources Off site sources of contamination are relevant to the site if pathways for migration of contaminants exist (see the discussion of pathways below). The historical land usage of the surrounding area is predominantly agricultural with progressive encroachment of residential areas to the southeast. Infilled marl pits are known, however, to exist up to the boundary of the site. It is considered that the likelihood of the site being affected by the presence of any off-site contamination is low to moderate.

5.3 Potential Pathways for Contamination. Contamination on site may be able to migrate along the following pathways:

• Migration of mobile contaminants on or off site via services, sewers and man made conduits.

• Migration through the underlying solid strata, as no drift deposits are indicated by the geological plan.

• Direct contact, ingestion and inhalation of contaminants on site. • Migration of contaminated dusts during earthworks. • Migration of mobile contaminants into groundwater and transport into surface waters. • Migration of hazardous gases. • Uptake of toxins/phytotoxins by plants.

5.4 Potential Receptors. In assessing risk, the categorisation shown in Table 4 has been developed. Table 4 is intended to be an aid in assessing the degree of risk. It should be noted that in terms of the Environmental Protection Act 1990 there is no differing degree of risk. It is either ‘significant’ or not.



Table 4: Risk Categorisation

Term Description Very High Risk There is a high probability that severe harm could arise to a

designated receptor from an identified hazard at the site without appropriate remedial action.

High Risk Harm is likely to arise to a designated receptor from an identified hazard at the site without appropriate remedial action.

Moderate Risk It is possible that without appropriate remedial action harm could arise to a designated receptor. It is relatively unlikely that any such harm would be severe, and if any harm were to occur it is more likely that such harm would be relatively mild.

Low Risk It is possible that harm could arise to a designated receptor from an identified hazard. It is likely that, at worst, if any harm was realised any effects would be mild.

Negligible Risk The presence of an identified hazard does not give rise to the potential to cause harm to a designated receptor.

As discussed above, the potential for significant contamination to be present on site is considered to be moderate to high, with the following receptors possibly at risk. Human receptors include:

1. Site investigation or construction workers during the redevelopment of the site from hazardous short term exposure.

2. Future users of the site and buildings. 3. Users of adjacent areas due to off site migration of gases, vapours or contaminated

dust. Controlled Waters

Groundwater The site is shown to be located directly upon mudstones of the Mercia Mudstone Group, and as such, it is considered likely downward migration of contaminants will be limited. The underlying strata are considered to represent a non aquifer. There are no abstraction points recorded within 1km of the site. The site does not lie within a source protection zone. Taking into account the above points, it is considered that the risk of contamination to the underlying groundwater is low.

Surface Waters A stream runs across the centre of the site at the base of the valley. The site must therefore be considered a high risk to surface waters.

Ecological Sites / Ecosystems

No areas of local ecological importance have been identified within a kilometre of the site according to the GroundSure Report.



Where phytotoxic contamination is identified at shallow depth within existing made ground soils, a risk to new planting in gardens /soft landscaping areas within the final development may exist.

Buildings, Foundations and Services Future redevelopment of the site will include the construction of new foundations. Elevated sulphate concentrations could affect the integrity of buried concrete structures. Services may be affected by the presence of aggressive contaminants which may corrode or penetrate services. Water supply pipes can be susceptible to penetration by hydrocarbons which may then affect the quality of the water supply. Based upon the aforementioned receptors, Table 5 summaries the potential risk and also provides an initial assessment of the likelihood of the identified hazard with regard to potential pollutant linkages and the redevelopment of the site, as proposed. Diagrammatic representation of the above Preliminary Conceptual Site Model (PCSM) for the site is shown on drawing No. C2852/2 in Appendix A. Table 5: Potential Contaminant-Pathway-Receptor Relationships

Contaminant Pathway Receptor Anticipated potential for the hazard to be present

Historical placement of made ground within former marl pits: Inorganic and organic contaminants, carbon dioxide & methane.

• Direct contact / Ingestion / Inhalation.

• Migration of mobile contamination into controlled waters.

• Gas migration. • Accumulation of gas in

buildings. • Migration along

services, sewers and man made conduits.

• Uptake of toxins/phytotoxins by plants.

• Consumption of contamination attached to home grown vegetables.

• Current site users. • Future site users. • Residents adjacent to

the site. • Site investigation or

construction workers. • Controlled waters. • Buildings, foundations

and underground services (especially plastic water supply pipes).

• Plant growth.

Moderate

6.0 FIELDWORK.

6.1 Introduction. The fieldwork was carried out to the design of Sirius, on the instruction of Hallam Land Management Limited. All work was carried out in general accordance with Eurocode 7.



Intrusive works were undertaken between the 23rd and 25th April 2008. A gas/groundwater monitoring programme has been completed. The fieldwork objectives were to establish the current ground conditions, and provide a contamination assessment of the ground in order to provide data for the proposed development and allow recommendations to be made in relation to disposal and/or reuse of made ground and natural soils identified below the site. Particular attention was paid to seven areas that were previously identified as marl pits infilled with domestic and industrial waste, located both on site and immediately off site.

6.2 Scope of Works. The PCSM was used as a basis for the design of an appropriate ground investigation. The ground investigation comprised a series of cable percussive boreholes and window sample holes boreholes in order to:

• Allow the determination of shallow soil conditions, • Determine the extents of infilled marl pits, • Recover soil samples for laboratory testing, • Assess groundwater, • Install wells for a programme of gas/groundwater monitoring.

Five cable percussive boreholes were drilled to a maximum of 9.10m. These were positioned within the expected areas of deepest made ground in order to determine composition and maximum depths of the backfilling. Following the completion of the drilling, groundwater and gas monitoring standpipes were installed in each borehole. Monitoring wells comprised 50mm slotted and solid HDPE casing surrounded by non calcareous pea gravel. Slotted sections of pipe were placed within made ground or natural soil to assess the potential presence of soil gasses within the site and to allow determination of groundwater levels/quality beneath the site. The monitoring installations were sealed with bentonite cement and completed with a gas tap assembly and lockable security cover. Care was taken to ensure that the boreholes did not provide any new pathways for the migration of contaminants. Nineteen window sample boreholes were drilled to a maximum of 4.00m. These were positioned to determine shallow ground conditions across the site and to determine the potential for hazardous gas migration. The seventeen window sample monitoring wells were constructed in the same way as the cable percussive borehole installations. The remaining boreholes were backfilled with arisings. Specific details regarding the installation of each well can be seen on the respective exploratory hole record sheets in Appendix E to this report. An experienced Sirius Geoenvironmental engineer supervised the fieldworks.

6.3 Strata Description. Depths and descriptions of strata and groundwater, together with details of the samples recovered are presented on the exploratory hole record sheets within Appendix E of this report.



Strata descriptions are based on an examination of the strata encountered together with consideration of the in situ and laboratory test data. The fieldwork was undertaken in general accordance with the procedures and principles contained in Eurocode 7. The information contained in this report is limited to land within the site boundary, as indicated on the site plan shown in Appendix A and to areas accessible during the ground investigation.

6.4 Sampling and Insitu Testing. A total of 145 samples of soil/made ground were obtained during the site investigation in order to provide a reasonable lateral and vertical representation of on-site conditions. The distribution and depth of samples taken across the site are recorded on the exploratory hole logs presented in Appendix B. Samples were selected by a representative of Sirius during the site investigation works. Samples of soil for chemical analysis were placed into 1 litre plastic containers and 0.50 litre brown glass jars. In addition, headspace screening was carried out on all the samples taken, for volatile organic compounds (VOCs) using a photo-ionisation detector fitted with a 10.6 eV bulb (PID). Samples were stored at approximately 4°C using cool boxes until the subsequent transport to a UKAS and MCERTS accredited laboratory. After the site investigation six site visits were made for monitoring. A landfill gas monitor was used to measure any ground gas production and a dip meter was used to measure the water levels.

7.0 GROUND CONDITIONS AND MATERIAL PROPERTIES. Generally, the encountered ground conditions consisted of a thin veneer of topsoil overlying red brown sandy gravelly clay. This clay is typically low in plasticity. At shallow depths, the horizons encountered are described as clayey sandy gravels and clayey gravelly sands with mudstone the predominant gravel found. Horizontal bedding is typically evident on a millimetre scale. The made ground found within the infilled marl pits is variable as the pits were infilled at different times and the material for each pit came from different sources. It should be noted that the test holes completed only provide data on the area immediately around the exploratory hole location, interpolation is then used to provide an overall picture of the site ground conditions. In general, the ground conditions encountered can be considered representative of the whole site. The possibility of variations in the conditions between exploratory points may be present, and such variations cannot therefore be taken into account in this report. Reference should be made to Sirius’ exploratory hole records enclosed in Appendix E of this report for a detailed description of the actual ground conditions revealed and when reading the following general notes.



7.1 Made Ground. Six infilled former marl pits were identified in the desk study (cf. hatched areas A-G in drawing no. C2852/2). There is a discrepancy between the location of Cockpitt Tip from different sources. Information sourced from East Staffordshire Borough Council placed it at Area B whilst information sourced from GroundSure placed it further south east at Area D. The current landowner was present at the time of infilling and confirmed the location at Area D was correct. Both areas were investigated as a matter of course. The material found in each location is detailed below. Area A (BH1 and BH2) Made ground in this area predominantly consists of a sand horizon with varying amounts of clay and gravel. Gravel includes mudstone, ash, clinker and brick. Fragments of glass, ceramics and wood were also noted. The made ground was deepest in the north (BH1) with a depth of 4.00m recorded. Area B (WS4) This is the area that that the landowner believes was mistakenly placed on the map as Cockpitt Tip. No evidence of made ground was found in this area during the investigation. Area C (BH3 and BH4) Made ground in this area is described as black slightly clayey gravelly sand. The gravel consists of mudstone, sandstone, quartz, ash, clinker and brick. Fragments of glass, ceramics and metal were also noted. The made ground was deepest in the south with a maximum depth of 9.00m recorded. Area D (WS9) Made ground was found to a depth of 0.85m and comprised three separate clay horizons. The deepest horizon (0.70m – 0.85m) was buried topsoil. No domestic or industrial waste was found. This is consistent with the landowner’s recollection of Cockpitt Tip being infilled with excavated natural material being used to fill the old pit, which from the depth of the made ground encountered was a hollow (dell) in the ground. Area E (WS10) Made ground in this area consists of sandy clay layers with varying amounts of gravel to a depth of 1.40m. The gravel documented includes mudstone, sandstone, quartz, coal, ash, clinker and brick. Black rubber resin was noted at a depth of 1.25m – 1.35m. Area F (WS12 and WS14) Area F consists of two small infilled pits separated by a small shoulder of land. The northern pit was investigated by WS12, the southern pit by WS14. The made ground in WS12 was encountered to a depth of 3.30m. The upper metre was recorded as sandy gravelly clay with



gravel of mudstone, sandstone and quartz. The deeper horizon from 1.00m to 3.30 was described as gravelly sand with gravel of mudstone, sandstone, ash and brick. Numerous glass and ceramic fragments were noted. The made ground in WS14 was encountered to a depth of 2.45m and proved more variable than that of WS12. Eight separate horizons were noted within the window sample borehole ranging from a shallow clay layer containing mudstone, sandstone, quartz, ash and brick through to an ash sand layer at the base. Also encountered were layers of a silty compressed powder, wood fragments, and sand layers containing plastic and glass. A full description is given in the window sample log contained in Appendix E. Area G (WS18) Area G is found on a steeply sloped area at the east of the site and was investigated by WS18. The depth of the made ground was not determined but anecdotal evidence that it is not much greater than the depth achieved by the window sample rig. The made ground encountered consisted of sandy gravelly clay with gravel of mudstone, sandstone, brick, ash and clinker. Occasional timber fragments were encountered. The made ground here is the remnants of a demolished bungalow. No asbestos was encountered during the investigation but its presence can not be discounted.

7.2 Residual Soil. Topsoil was found in all locations and is characteristically described as brown sandy gravelly clay with gravel of mudstone and quartz and containing frequent rootlets.

Beneath the topsoil, away from the infilled marl pits, red brown clay of low plasticity containing mudstone gravel and rootlet traces was encountered. The plasticity decreases with depth as the horizon becomes increasingly granular. By 1.00m the horizon is typically described as a sand or gravel but this may occur as shallow as 0.20m (WS1). Horizontal bedding is evident within these horizons.

7.3 Bedrock Mudstone/siltstone was encountered in WS7 at 1.90m and in WS9 at 2.90m.

7.4 Groundwater. No groundwater was encountered during the site investigation. Some minor groundwater was encountered sporadically during the last two monitoring visits following periods of heavy rain. It is thought that this represents surface runoff and not a continuous groundwater body.

7.5 Visual / Olfactory Evidence of Contamination. No visual/olfactory evidence of hydrocarbon contamination was encountered during the investigation.



8.0 CONTAMINATION ASSESSMENT.

8.1 General. The Preliminary Conceptual Site Model (Section 5) identified that the site is considered to pose a moderate risk of potentially having caused significant ground contamination. The site is considered to lie within a setting of moderate environmental sensitivity. Facts that are considered pertinent are:

• A watercourse runs through the centre of the site in a west-east direction. • The site is underlain by little or no drift, overlying a non aquifer. • There are two groundwater abstraction points within the site boundary and a further five

within a kilometre of the site. • There are no licensed surface water abstractions within 1km of the site. • The site does not lie within a source protection zone. • The site does not lie within a fluvial or tidal indicative floodplain. • The site lies within a rural/residential setting.

Consideration is being given to the development of the site for a mixture of residential and commercial end use, with buildings, areas of hardstanding and areas of private gardens and landscaping. This is considered to represent a moderate to high sensitivity end use.

8.2 Testing Schedule. Twelve soil samples (11 of made ground and 1 of natural soils) were analysed for the following determinants:

• pH, total and water soluble sulphate, sulphur, total monohydric phenols, speciated polycyclic aromatic hydrocarbons (PAH), and metals (arsenic, cadmium, chromium, copper, lead, mercury, selenium, nickel and zinc).

The leachable concentrations of the following determinants were measured in five samples of made ground:

• pH, metals (arsenic, cadmium, chromium, copper, lead, mercury, selenium, nickel and zinc), phenols and speciated PAH.

In addition the following tests were carried out on made ground soils:

• Ten asbestos screens • Three banded TPH analyses;

Two water samples were also analysed (one taken upstream of the site and one taken downstream of the site) for the following determinants:



• pH, metals (arsenic, cadmium, chromium, lead, mercury, copper, nickel, zinc and selenium), hardness, monohydric phenol, speciated PAHs, electrical conductivity and ammonia.

8.3 Current Guidance and the Interpretation of Analytical Data. Contaminated land is defined under law through Part IIA of the Environmental Protection Act 1990, implemented through Section 57 of the Environment Act 1995. This supports a ‘suitable for use’ based approach to the risk assessment of contaminated land. The site specific risk assessment is based upon an assessment of plausible pollutant linkages, referred to as the contaminant → pathway → receptor (or target) model, based upon the current or proposed use of the site. One of the main objectives of this investigation was to provide information on land contamination at the site, required for assessing relevant pollutant linkages, to undertake a risk assessment and where necessary, determine remedial options. These works were carried out in accordance with the risk assessment and options appraisal sections of the Model Procedures for the Management of Land Contamination (CLR11). The first stage of a contaminated land risk assessment is to devise a conceptual site model (see Section 5) in order to identify potential contaminants, pathways and targets which may combine to form a pollution linkage. Where pollution linkages are identified site investigation works should be carried out to provide data to refine the initial assessment. This would be carried out in the following manner.

• Comparison of the soil analysis results against generic soil screening values. • Statistical testing for the Planning Scenario by the methods described in CL:AIRE &

CIEH “Guidance on Comparing Soil Contamination Data with a Critical Concentration”, May 2008.

• If the screening levels are exceeded, more detailed quantitative risk assessment (DQRA) may be undertaken, if deemed appropriate or alternatively suitable cost effective remedial action may be taken to break the pollutant linkages.

In accordance with the above, the chemical concentrations encountered on site have been compared to generic soil screening levels. The initial generic screening levels used by Sirius are derived from the following guidance documents: CLEA (2002)/ CLEA UK For general human health risk assessment purposes, the current best practice soil screening values for use in UK were derived using the DEFRA Contaminated Land Exposure and Assessment (CLEA 2002) model. A number of land use scenarios are defined within CLEA from which generic soil guideline values (SGVs) were then derived. CLEA 2002 has now been withdrawn and replaced by CLEA UK, although the published SGVs remain valid. At the time of writing, however, published SGVs are only available for a limited number of parameters, although toxicological data is also available for a range of other compounds.



As the proposed end use of the site is mixed residential and commercial, but with no development layout plan currently available, a worst case scenario of a ‘residential with plant uptake’ end use has been considered for the purposes of this contamination assessment. The most recent EA guidance indicates that “since its release in November 2005, feedback from CLEA UK beta users has suggested that this software has performed effectively in the majority of cases. It is therefore recommended by the Environment Agency for use in human health risk assessment in conjunction with advice on our CLEA web pages”. “The Environment Agency will consider the formal status of CLEA UK beta software following the review of the Soil Guideline Values being undertaken by Defra”. Land Quality Management and Chartered Institute for Environmental Health, Generic Assessment Criteria for Human Health Risk Assessment (2007). LQM and CIEH have derived a set of Generic Assessment Criteria (GAC) for soil contaminants, for which there are no Defra or Environment Agency published SGVs. In the absence of published SGVs for hydrocarbon fractions, copper, zinc and a number of PAH compounds, it is considered that these GAC are appropriate for use for human health purposes. A ‘residential with plant uptake’ end use has been considered. PAHs For those other PAH compounds for which SGVs or GACs presented by LQM have not been issued, GAC values were derived by Sirius in accordance with current UK guidance using CLEA-UK software, details of which can be provided on request. Environment Agency Environmental Quality Standards For the purposes of this report, a Tier I (R&D P20) assessment using leachability analytical concentrations from the site soils has been carried out to assess potential risks to local controlled waters. The results of the leachability analysis has been compared directly with the Environmental Quality Standards (EQS) for Fresh Waters, owing to an on-site stream being the nearest controlled waters receptor. Where a freshwater EQS is not available the Water Supply (Water Quality) Regulations (2001) have been used for screening purposes.

8.4 Chemical Results and Generic Quantitative Risk Assessment. Total Soils Analysis The results of the made ground soils analysis as received from the laboratory are presented in Appendix F to this report, and are summarised in the tables below. Made Ground The chemical analysis identified elevated concentrations of arsenic, lead, copper, nickel, zinc, total sulphate, water soluble sulphate, chrysene, benzo(a)pyrene, diesel range organics and mineral oil range organics respect to a residential with plant uptake end use. Table 6: Summary of Total Soil Concentrations and Generic Quantitative Risk Assessment – Made Ground

Parameter Screening value No. of samples No. of Maximum concentration



(mg/kg, unless otherwise

stated)

above screening value

samples tested

exceeding threshold (mg/kg, unless otherwise stated)

Metals/Metalloids Arsenic 20 (a) 5 11 88 in BH3 at 6.00m Cadmium 1 (pH 6) (a)

2 (pH 7) 8 (pH 8)

0 11

Chromium (Total) 130 (a) 0 11 Lead 450 (a) 2 11 1470 in BH1 at 2.70m Mercury 8 (a) 0 11 Selenium 35 (a) 0 11 Copper 111 (b) 5 11 1780 in BH1 at 2.70m Nickel 50 (a) 4 11 101 in BH3 at 6.0m Zinc 330 (b) 4 11 1360 in BH3 at 6.0m Inorganics pH <5 0 11 All samples between 7.1 and

8.3 Total Sulphate 2,400 (c) 2 11 11,000 in BH1 at 2.70m and

BH3 at 6.00m Water Soluble Sulphate 0.5 g/l (c) 2 11 2.0 in BH1 at 2.70m Organics Monohydric Phenol 78 (1% SOM) (a)

150 (2.5% SOM) 280 (5% SOM)

0 11

Naphthalene 3.47(1% SOM) (a) 8.47 (2.5% SOM)

17 (5% SOM)

0 11

Acenaphthylene 18 (1% SOM) (a) 46 (2.5% SOM) 91 (5% SOM)

0 11

Acenaphthene 45.7(1% SOM) (a) 112 (2.5% SOM) 220 (5% SOM)

0 11

Fluorene 38.4(1% SOM) (a) 91.4 (2.5% SOM)

184 (5% SOM)

0 11

Phenanthrene 16 (1% SOM) (a) 39.3 (2.5% SOM)

77 (5% SOM)

0 11

Anthracene 19900 0 11 Fluoranthene 1700 0 11 Pyrene 1300 0 11 Benz[a]anthracene 9.3 0 11 Chrysene 1.3 1 11 2.2 in WS18 at 0.20m-0.40m Benzo[b]fluoranthene 10.1 0 11 Benzo[k]fluoranthene 36 0 11 Benzo[a]pyrene 1.12(1% SOM) (a)

1.08 (2.5% SOM)1.09 (5% SOM)

2 11 2.2 in WS18 at 0.20m-0.40m

Indeno[1,2,3-cd]pyrene 13.6 0 11 Dibenz[a,h]anthracene 1.14(1% SOM) (a)

1.13 (2.5% SOM)1.10 (5% SOM)

0 11

Benzo[ghi]perylene 19 0 11 TPH PRO 575 µg/l 0 3



DRO 1.94 3 3 40 in BH1 at 2.0m MRO 157 1 3 226 in BH1 at 2.0m Miscellaneous Asbestos Fibres Present 0 10 None detected

Notes: (a) DEFRA soil guideline values for ‘residential with plant uptake’ end-use. (b) LQM CIEH Generic Assessment Criteria for ‘residential without plant uptake’ end use. (c) BRE (2005) Special Digest 1, 3rd Edition, Concrete in aggressive ground. Upper limits for DS-1 Design Sulphate Class concrete. The made ground on site is not a continuous body but distinct unconnected areas that bear no relation to each other, either in source or time of placement. It is preferable therefore to analyse these areas separately. The area designations below correspond to those shown in drawing no.: C2852/3. Area A – BH1/BH2 A sample from BH1 returned elevated sulphate, arsenic, copper and lead and benzo(a)pyrene. Area C – BH3/BH4 The made ground in BH3 returned elevated results for sulphate, arsenic, copper, lead, nickel and zinc. Area D – WS9 All results were below the threshold for ‘residential with plant uptake’ end use. Area E – WS10 All results were below the threshold for ‘residential with plant uptake’ end use. Area F - WS12/WS14 A sample from WS12 returned elevated results for arsenic, copper, nickel and zinc. A sample from WS14 returned results below the threshold for ‘residential with plant uptake’ end use. Area G – WS18 A sample from WS18 returned elevated results for chrysene and benzo(a)pyrene. TPH Contamination Three samples were tested for TPH contamination – BH1 at 2.0m, BH3 at 3.5m and WS18 at 1.4m-1.6m. Each sample showed slightly elevated diesel range with recorded results of 40 mg/kg, 23 mg/kg and 19mg/kg respectively. Other



No asbestos fibres were identified in the made ground samples screened. The other analytes tested were detected at less than laboratory detection limits or found not to exceed their adopted generic threshold values. Natural soils WS 8 was drilled away from any area of made ground to allow for control testing to be carried out. The thresholds for a ‘residential with plant uptake’ were not exceeded in for any determinand. Leachable Concentrations in Soils Leachate analysis was undertaken to provide an indication if any potential contaminants were leachable from the made ground. The results of the leachability testing are summarised in Table 11 and the laboratory results are presented in Appendix F to this report. The lack of elevated leachable determinands indicates that should the made ground come into contact with water via infiltration or via direct contact with groundwater, these contaminated should not become mobile, reducing the risk to controlled waters. Table 7 Summary of Soil Leachate Concentrations and Generic Quantitative Risk Assessment Parameter Screening value

(units µg/L unless otherwise stated)

No. of samples above screening

value

No. of samples tested

Maximum concentration above screening value (units µg/L unless otherwise stated)

Metals/Metalloids Arsenic 50 (a) 0 5 Cadmium 5 (a) 0 5 Chromium 250 (a) 0 5 Lead 250 (a) 0 5 Mercury 1 (a) 0 5 Selenium 10 (a) 0 5 Copper 28 (a) 0 5 Nickel 200 (a) 0 5 Zinc 500 (a) 0 5 Organics Naphthalene 10 (a) 0 5 Benzo(a)pyrene 0.01 (b) 0 5 Benzo(ghi)perylene* 0.1 (b) 0 5 Indeno(1,2,3-cd) pyrene* 0.1 (b) 0 5 Others pH 6-9pH units 0 5 pH range: 7.4 in BH1 at

2.70m to 8.0 in WS18 at 0.20m-0.40m

(a) Environment Agency (2002) Environment Agency technical advice to third parties on pollution of controlled waters for Part IIA of the EPA

1990. Freshwater EQS. (b) The Water Supply (Water Quality) (Amendment) Regulations 1989 2001 and 2007.



Groundwater Analysis No groundwater was encountered during the site investigation. Occasional water recorded during the later monitoring visits followed extended periods of rain and is not thought to represent a distinct groundwater body. Surface Water Analysis A water sample was taken from positions upstream and downstream from the site. Table 8: Summary of Concentrations and Generic Quantitative Risk Assessment Parameter Generic Assessment

Criterion (µg/l unless otherwise

stated)

No. of samples

above screening

value

No. of samples tested

Maximum concentration above screening value (µg/l

unless otherwise stated)

Metals/Metalloids Arsenic 50 (a) (10) (b) 0 2 Cadmium 5 (a, b) 0 2 Chromium+ 5-250 (a) (50) (b) 0 2 Lead+ 4-250 (a) (25) (b) 0 2 Mercury 1 (a, b) 0 2 Selenium 10 (b) 0 2 Copper+ 1-28 (a) (2,000) (b) 0 2 Nickel+ 50-200 (a) (20) (b) 0 2 Zinc+ 8-500 (a) (5,000) (b) 0 2 Inorganics Sulphate (400 mg/l) (a) 250 mg/l (b) 0 2 Ammonia (NH3 as N) Ammonium (as NH4

+) 15 (a)

(500) (b)

Organics Naphthalene 10 (a) 0 2 Benzo(a)pyrene 0.01 (b) 0 2 Benzofluoranthene* 0.1 (b) 0 2 Benzo(ghi)perylene* 0.1 (b) 0 2 Indeno(1,2,3-cd)pyrene* 0.1 (b) 0 2 Phenol (30) (a) 0.5 (b) 0 2 Others Electrical Conductivity 2,500 μS/cm @ 20ºC (b) pH 6-9 pH units (c) 0 2 pH range: 8.3 (WAT B)

to 8.4 (WAT A) (a) Environment Agency (2002) Environment Agency technical advice to third parties on pollution of controlled waters for Part IIA of the EPA

1990. Freshwater Environmental Quality Standards (EQS). (b) The Water Supply (Water Quality) (Amendment) Regulations 2001 and 2007. (c) The Surface Waters (Fishlife) (Classification) Regulations 1997. + Hardness related (Lowest values are applied in the absence of site-specific hardness data). * The sum of all 4 individual PAHs marked with an asterisk (*)



8.5 Reassessment of Site Conceptual Model. As discussed in Section 5 risk assessment is based on contaminant > pathway > receptor principles. With respect to the subject land and the analytical results these can be defined as follows: Identified Contaminants of Concern • Elevated metals and/or PAHs within Areas A, C, F and G. • Slightly elevated hydrocarbon fractions in BH1, BH3 and WS18 corresponding to diesel

contamination. Pathways • Dermal contact with potentially contaminated Made Ground; • Direct/Indirect Ingestion of potentially contaminated Made Ground; • Inhalation of dust from potentially contaminated Made Ground; • Migration of any mobile contamination, gases and vapours via permeable Made Ground; • Potential plant uptake of contamination in soil. Targets/Receptors • Current site users; • Future users; • Adjacent residents; • Construction and maintenance workers; • Controlled waters; • Building, foundations and underground services • Plant growth. In assessing risk, the categorisation shown in Table 4 has been applied to assess the degree of risk. Overview The intrusive investigation and subsequent soil testing has broadly confirmed the made ground soils to comprise ash and soil made ground with inclusions of ceramic, glass, sandstone and brick. There is little putrescible content to the made ground and leachate testing has indicated that there is low leaching potential from the made ground. End Users / Landscaping Based on the contaminant > pathway > receptor philosophy, it is considered that widespread elevated toxic metals and PAH concentrations within the made ground moderate risk to end users. Four of the made ground areas identified by the desk study returned chemical testing results with elevated metals and/or PAHs. All three made ground samples showed slightly elevated diesel range hydrocarbon contamination. The presence of minor diesel contamination in the



other two made ground areas can not be discounted. The CLEA model addresses contaminants within the top 1 m of the soil profile in the context of various potential pathways. In this report it is assumed that contaminants within the top 1 m may be accessible to site users and therefore it is considered that the backfilled marl pits could pose a moderate risk to current and future site users. Where these made ground soils are to remain in situ, it is recommended that private gardens/landscaped areas be covered by providing a suitably designed cover layer of clean inert soils, subject to local authority agreement. The cover layer will remove the direct pollutant linkage and therefore the significant risk to end users and future soft landscaping/plants. In addition it will provide a suitable growing medium for shallow rooted plants. Deep rooted plants will need to be potted in a suitable depth of topsoil. It is recommended that a minimum thickness of 600mm be used (including topsoil). Where hardstand is proposed (whether it is buildings or car parking) it will remove the direct pollutant linkage between the made ground and end users and therefore remove the risk. In such areas made ground soils could remain in-situ, subject to their engineering properties being deemed suitable. In summary, the identified contaminants of concern are considered to pose a negligible risk to end users provided that the made ground areas are either capped with clean soil as described above, or alternatively excavated and removed off site as the potential pollutant linkages will then be broken. A graphical interpretation of the post development conceptual model for the site is presented as drawing do. C2852/4 in Appendix A. Gas protective measures are discussed in Section 10 of this report Construction and Maintenance Workers Construction workers involved in the groundworks and construction during the site redevelopment are at risk from exposure to contaminated soils given their close proximity and contact with the soil which may result in a short term human health risk from the detected contaminants. The primary contaminant exposure pathways are considered to be dermal contact, indirect soil ingestion and inhalation of soil dusts and vapours. These risks can be reduced by appropriate PPE, hygiene precautions and good working practices. It is recommended that normal health and safety procedures should be adopted by groundworkers including no eating, drinking or smoking on-site, designated clean and wash areas and protective clothing. It is also recommended that procedures outlined in the HSE document “Protection of Workers and the General Public during Redevelopment of Contaminated Land” be followed. There will be a requirement to comply with the COSHH (Control of Substances Hazardous to Health 1994) Regulations and the CDM (Construction Design and Management 1995) Regulations during any proposed development works. This report should be forwarded to the construction company undertaking the groundworks in order for them to assess the risk to their personnel.



Adjacent Site Users Adjacent site users may be potentially exposed on a short term basis (primarily through potential inhalation/ingestion of dust) to the made ground if it is disturbed during the redevelopment of the site. However, this could be adequately controlled by careful excavation of the material and standard dust control measures during redevelopment works. Controlled Waters Leachate testing has indicated that there are no elevated leachable concentrations of metals and PAH present within the made ground. This would indicate that should the made ground come into contact with water via infiltration, contaminants should not become mobile. No groundwater was encountered during the site investigation and only in isolated pockets during the latter stages of the monitoring period. The water table may show considerable seasonal variation, however, and the presence of shallow groundwater during the winter months should not be discounted at this time. The potential risks associated with the migration of contaminated waters into the underlying controlled waters contained within the Triassic mudstone strata, and risk associated with such an occurrence, are considered to be low due to:

• The presence of clayey deposits limiting vertical migration of contaminants; • The underlying Triassic mudstone strata being classified as a non aquifer; • The site does not lie within a designated groundwater Source Protection Zone; • No potable water abstraction licenses are found within 2000m of the site;

Surface water testing upstream and downstream of the site has shown no significant contamination associated with the site or entering the site. Surface waters are not therefore considered to be a significant risk. A graphical interpretation of the post development conceptual model for the site is presented on drawing no. C2852/4 in Appendix A to this report. Built Development Water soluble sulphate analysis of the made ground soils returned results ranging from 2.0 g/l in BH1 to lower than the detection limit of 0.1 g/l in seven samples. The variability of made ground found across the site precludes a general Design Sulphate Class and ACEC class being applied across the made ground as a whole. Should the made ground be left in-situ, a copy of the chemical results should be forwarded to the appropriate utility companies in order to determine the necessity for service protection. The classification of the site as a whole was beyond the scope of this investigation. Upon construction, services excavated through the areas of made ground should be constructed within oversized trenches and backfilled with clean inert fill in all directions. This will allow any future maintenance works to be undertaken in clean material, minimising the risk of contact with any contaminated material.



9.0 HAZARDOUS GAS MONITORING.

9.1 General. Hazardous concentrations of methane and carbon dioxide can be generated by the degradation of organic matter/biodegradable materials. Methane is a flammable gas and a mixture containing 5% and 15% v/v in air is explosive. Carbon dioxide is an asphyxiant and toxic. Approved Document C to the Department of the Environment’s Building Regulations 2004, requires that a gas risk assessment is undertaken, which may require investigation and monitoring. Notwithstanding the requirements for a risk assessment, Approved Document C states that ground gas monitoring is required for the following ground conditions:

A) There is a landfill within 250m of the site; B) There is wide scale deposition of biodegradable substances; C) The site has been subject to wide spread spillages of petrol, oil, or solvents; D) The site is in an area of naturally occurring methane or carbon dioxide;

Where there may be gaseous contamination of the ground, Approved Document C cross references Construction Industry Research and Information Association (CIRIA) Report 149 for advice on remedial measures. Where there may be gaseous contamination of the ground but the level of methane is unlikely to exceed 1% by volume, the ground floor of any house or similar small building shall be constructed of suspended concrete and ventilated as described in BRE Digest Report “Construction of New Buildings on Gas Contaminated Land”. The document also requires specific design measures to be taken if a level of 5% volume carbon dioxide exists or is exceeded within the ground. CIRIA has also issued several guidance documents on landfill gas namely: CIRIA Report 149 ‘Protecting Development from Methane’ (1995) CIRIA Report 150 ‘Methane Investigation Strategies’ (1995) CIRIA Report 151 ‘Interpreting Measurement of Gas in the Ground’ (1995) CIRIA Report 152 ‘Risk Assessment for Methane and other gases from the ground’

(1995) CIRIA C665 ‘Assessing risks posed by hazardous ground gases to buildings

(revised)’ (2007) The above documents are intended to provide advice on how to investigate and deal with gas contaminated ground with respect to general development. However, for low rise residential housing, the NHBC document report 10627-R01-(02) “Guidance on Evaluation of Development Proposals on Sites where Methane and Carbon Dioxide are Present” 2007 is the most appropriate guidance. This document assesses both gas concentrations and flows ad how this may affect dwellings, adopting a “traffic light” system of classification of gas regime.



Reference has also been made to British Standard BS8485:2007 “Code of Practise for the Characterisation and Remediation from Ground Gas in Affected Developments” published in 2007.

9.2 Monitoring Procedure. The gas monitoring was undertaken in accordance with the Guidance given in CIRIA Report 151 ‘Interpreting Measurements of Gas in the Ground’ (1995) and the more recent CIRIA C665 (2007). The gas monitoring wells installed by Sirius were monitored for methane, carbon dioxide and oxygen using a LMSx infra red gas analyser. Groundwater levels were measured using an electronic dip meter. The results are presented in Appendix G to this report.

9.3 Results. The worse case results of the monitoring visits can be summarised as: Maximum methane concentration – 0.9% v/v (BH4) Maximum carbon dioxide concentration – 24.0% v/v (BH4) and 15.7% in BH1 Minimum oxygen concentration – 0.8% v/v (BH4) Maximum flow rate – + 1.2 l/hr (WS16 and WS18) Barometric pressure varied between 996 and 1014 mbar, representing periods of low to high atmospheric pressure. An assessment of the recorded data, in accordance with CIRIA C665, indicates Gas Screening Values (GSVs) of 0.0108 l/hr and 0.288 l/hr for methane and carbon dioxide respectively.

9.4 Discussion. We would note that the ground gases found over the landfilled areas comprise up to a maximum of 0.1% methane over the areas of landfill, and 0.9% outside landfill areas. Carbon dioxide was recorded at a maximum of 15.7% on onsite landfill and less than 5% outside the landfill areas. Gas flows up to a maximum of 1.2 l/hr were recorded. A reading of 24% carbon dioxide has been obtained from an area of landfill immediately beyond the site boundary. Evidence from surrounding monitoring points indicates there is no gas migration occurring from the identified landfills. As a preliminary overview it can therefore be stated that the majority of the site can be regarded as unaffected by ground gases, although this will require confirmation by further site investigations by developers as parcels of land are released for development. Over the areas of made ground, the ground gas precautions required are as follows.



The proposed development consists of a mixture of residential and commercial properties. According to CIRIA C665: Assessing Risk Posed by Hazardous Ground Gases to Buildings this represents a mixture of Situation A and Situation B type properties with regard to gas protection measures, in which Situation B refers to low rise housing with a vented underfloor void (min 150mm), and Section A encompasses all other development types. Situation A – all development types except those in Situation B The carbon dioxide Gas Screening Value of 0.288 l/h places the site in Characteristic Situation 2, a ‘low risk’ classification. For commercial development, 1 to 2 levels of protection are required in this case. A typical scope of protective measures (taken from CIRIA C655) includes:

a) Reinforced concrete cast in situ floor slab (suspended, non-suspended or raft) with at least 1200 g DPM2.

b) Beam and block or pre cast concrete slab and minimum 2000 g DPM/reinforced gas membrane.

c) Possibly underfloor venting or pressurisation in combination with a) and b) depending on use.

d) All joints and penetrations sealed. Situation B – Low rise housing with a ventilated underfloor void (min 150mm) We would note the maximum carbon dioxide level of 15.7% would classify Landfill A as comprising Amber 1 gas conditions, which subject to more detailed analysis and risk assessment, may be revised downwards. The maximum gas readings over Landfill C of 24% carbon dioxide would classify this area as Amber 2, which could be revised downwards on the basis of further risk assessments. This, however, is not part of the brief of this report. We could note the worst case GSV of 0.288 l/h for carbon dioxide could reclassify the site in the Green category of the NHBC Traffic Light system. If approved, this would necessitate negligible level gas protection measures for buildings in Situation B. Residential buildings, outside the scope of Section B, as defined by the NHBC guidance, require Amber 1 or Amber 2 levels of protection. In this case the scope of protective measures includes:

a) Reinforced concrete cast in situ floor slab (suspended, non-suspended or raft) with at least 1200 g DPM and possibly underfloor venting.

b) Beam and block or pre-cast concrete and 2000g DPM/ proprietary gas membrane and underfloor venting.

c) All joints and penetrations sealed.

Radon Radon protective measures are not currently required for development on this site.



10.0 CONCLUSIONS AND RECOMMENDATIONS. The site comprises existing agricultural land that has been subject to localised mineral extraction for marl pits, since backfilled with waste in the 1960s.

10.1 Mining and Quarrying. The conceptual site model for the site identified a negligible risk to surface stability from past coal mining or gypsum extraction.

10.2 Contamination Constraints to Development. The preliminary risk assessment revealed that the site has historically been occupied by a farm containing a serious of marl pits that have since been backfilled with household and industrial waste. The domestic refuse is typical of pre-Clean Air Act wastes and comprises mostly ashy fills with little putrescible materials. Laboratory soils testing has indicated contamination to be present. There is no evidence, however, that the contamination can leach into controlled waters. Surface water analysis indicates levels of contamination below guidance levels. Within the made ground deposits elevated levels of sulphate, arsenic, copper, lead, nickel, zinc, benzo(a)pyrene and chrysene were encountered. Only samples taken from Area D and Area E returned all results below the thresholds for a ‘residential with plant uptake’ end use. Each sample of made ground tested for TPH contamination returned slightly elevated results for diesel range organics. The possibility that areas D and E may also have slightly elevated levels can not be discounted. In order to remove the risks to end users from the identified contaminated made ground deposits it is recommended that the former marl pits should be suitably remediated. Given the localised nature of these areas, it is considered that the most appropriate form of remediation will be the excavation and off-site disposal of these soils. All remediation works should be validated by a suitably qualified consultant. It is strongly recommended that consultation takes place with the regulatory authorities to agree remediation measures prior to site works taking place. Any materials removed from site should be undertaken in accordance with the Duty of Care Regulations 1991 and the Hazardous Waste Regulations 2005. It is possible that areas of more significant contamination may be encountered on site during redevelopment. If any areas of noxious, odorous, brightly coloured, fibrous, liquid etc. contamination are identified, further advice should be sought from a suitably qualified consultant.

10.3 Hazardous Gas. The proposed development contains both Situation A and Situation B buildings in which Situation B refers to low rise housing with a vented underfloor void (min 150mm), and Section A



encompasses all other development types, as outlined in CIRIA C665: Assessing Risks Posed by Hazardous Ground Gases to Buildings. For Section B, reference is made to the NHBC document. The majority of the site appears to be unaffected by elevated ground gases, which appear to be limited to the identified areas of landfill. The generally ashy content of the made ground, with low volumes of putrescible materials present, would typically indicate a low likelihood of existing or future methane generation but may often be associated with elevated carbon dioxide levels. The gas readings observed to date would appear to confirm this general overview. Potential gas precautions required over the landfill areas are therefore as follows: Situation A The carbon dioxide Gas Screening Value of 0.288 l/h places the site in Characteristic Situation 2, a ‘low risk’ classification. For commercial development, 1 to 2 levels of protection are required in this case. A typical scope of protective measures includes:

a) Reinforced concrete cast in situ floor slab (suspended, non-suspended or raft) with at least 1200 g DPM.

b) Beam and block or pre cast concrete slab and minimum 2000 g DPM/reinforced gas membrane.

c) Possibly underfloor venting or pressurisation in combination with a) and b) depending on use.

d) All joints and penetrations sealed. If residential buildings outside the scope of Section B are to be constructed (i.e. greater than three storeys), two levels of protection are required. In this case the scope of protective measures includes:

a) Reinforced concrete cast in situ floor slab (suspended, non-suspended or raft) with at least 1200 g DPM and underfloor venting.

b) Beam and block or pre-cast concrete and 2000g DPM/ reinforced gas membrane and underfloor venting.

c) All joints and penetrations sealed.

Situation B Typical maximum gas concentrations of methane do not exceed 1% by volume across the site as measured to date, and typical maximum gas concentrations of carbon dioxide of 15.7% are indicative of Amber 1 conditions. A reading of 24% was taken from a landfill off site (landfill C) which would be classified as Amber 2 precautions. More detailed risk assessment will be required in due course dependent upon the final use of these areas. Initial assessments are that low gas flows have been observed and the worst case Gas Screening Value (GSV) for carbon dioxide places the site in the Green category of the NHBC Traffic Light system. Gas protection measures are not considered necessary in this situation.

Radon protective measures are not currently required for development on this site.

Documents

Geoenvironmental Report FINAL - East Staffordshire · APPENDIX C – DESK STUDY CORRESPONDENCE APPENDIX D – EAST STAFFORDSHIRE BOROUGH COUNCIL REPORT ... • Kitling Greaves Lane