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Contaminated Land Remediation Strategy: Rugby Cattle Market
Final
Barteak Developments Limited
August 2008
Prepared by: ................................................ Approved by: ................................................. Philip Smart Chris Paterson Technical Director Director Contaminated Land Remediation Strategy: Rugby Cattle Market
Rev No Comments Date
0 Draft to Barteak Developments for comments 1 February 2008
1 FINAL 5 August 2008 14 Queen Victoria Road, Coventry, CV1 3PJ Telephone: 02476 253300 Fax: 02476 253301 Website: http://www.fabermaunsell.com Job No 54735icvg Reference FINAL Date Created August 2008 This contains confidential and commercially sensitive information, which shall not be disclosed to third parties. f:\projects\54735icvg rugby cattle market\report\contaminated land remediation strategy final.doc
1 Introduction ..................................................................................................................... 3 1.1 Background........................................................................................................... 3 1.2 Purpose of Report................................................................................................. 3 1.3 Supporting Information ......................................................................................... 3 1.4 Limitations............................................................................................................. 3
2 Site Location and Background Information ................................................................. 6 2.1 Site Location ......................................................................................................... 6 2.2 Site History and Development Proposals ............................................................. 6 2.3 Geology................................................................................................................. 6 2.4 Hydrogeology........................................................................................................ 7 2.5 Hydrology.............................................................................................................. 7 2.6 Previous Investigations......................................................................................... 7 2.6.1 Geology................................................................................................................. 7 2.6.2 Soil quality............................................................................................................. 7 2.6.3 Ground gases ....................................................................................................... 8 2.7 Ground Investigation 2007.................................................................................... 8 2.8 Site Condition Survey ........................................................................................... 9
3 Ground and Groundwater Conditions ........................................................................ 11 3.1 Geology............................................................................................................... 11 3.2 Soil Chemical Results ......................................................................................... 11 3.3 Hydrogeology...................................................................................................... 14 3.3.1 Groundwater level............................................................................................... 14 3.3.2 Groundwater quality............................................................................................ 14 3.4 Ground gases ..................................................................................................... 14 3.5 Summary............................................................................................................. 15
4 Conceptual Model and Risk Assessment................................................................... 17 4.1 Introduction ......................................................................................................... 17 4.2 Conceptual Model ............................................................................................... 17 4.2.1 Sources............................................................................................................... 17 4.2.2 Receptors............................................................................................................ 17 4.2.3 Pathways ............................................................................................................ 17 4.3 Remediation Strategy ......................................................................................... 18 4.3.1 Methodology ....................................................................................................... 18 4.3.2 Remediation Strategy ......................................................................................... 19 4.4 Soils Testing ....................................................................................................... 19 4.5 Compliance with Legislation ............................................................................... 20 4.6 Ground gases ..................................................................................................... 20 4.7 Soakaways.......................................................................................................... 20
5. Conclusions and Recommendations.......................................................................... 23 5.1 Conclusions. ....................................................................................................... 23 5.2 Recommendations .............................................................................................. 24
Table of Contents
Figures
Figure 2.1 Plan showing the site location Figure 2.2 Site layout Figure 2.3 Plan of 2006 investigation borehole locations Figure 2.4 Summary of ground contamination identified in 2006 Figure 2.5 Plan of 2007 investigation borehole locations Figure 3.1 Thickness of made ground (m) Figure 3.2 Thickness of sands and gravels (m) Figure 3.3 Depth to Lias Clay (m) Figure 3.4 Geological cross-section Figure 3.5 Groundwater contours (mAOD)
Appendices
Appendix A Site Masterplan 2007 (SK16.11.07A) Appendix B Trial pit, probehole and borehole logs 2007 Appendix C Laboratory data sheets for soil samples 2007 Appendix D Laboratory data sheets for groundwater samples 2007 Appendix E Groundwater level and ground gas monitoring results
Introduction
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 3
1.1 Background
Faber Maunsell Limited is commissioned by Barteak Developments Limited to provide technical
advice in respect of the proposed re-development of Rugby Cattle Market for a mixed use
development, including residential and commercial uses. Previous investigations carried out on
the site have shown the presence of ground contamination, with a number of contaminants
present at concentrations above the guidance levels for a residential end use.
1.2 Purpose of Report
The purpose of this report is:-
• to review the ground and groundwater conditions at the Rugby Cattle Market site;
• to identify the potential risks posed by the ground and groundwater conditions at the
site on human health and controlled waters; and
• to identify any remedial measures, which are considered necessary to render the site
suitable for the proposed re-development.
1.3 Supporting Information
The assessment of the ground and groundwater conditions on the site is based on the following
sources of information:-
• British Geological Survey (BGS) 1:50,000 scale map, Sheet 184 Warwick and 1:10,000
scale map SP57NW;
• Faber Maunsell report reference 45773ibme, entitled ‘Rugby Cattle Market:
Contaminated Land Survey Report’ dated March 2006;
• Faber Maunsell report reference 53581cvg, entitled ‘Rugby Cattle Market – Health and
Safety Site Inspection Report and Risk Assessment’ dated September 2007;
• NHBC Document Report No.4, entitled ‘Guidance on evaluation of development
proposals on sites where methane and carbon dioxide are present’ dated March 2007;
• Discussions held with the Contaminated Land Officer of Rugby Borough Council; and,
• The results of a geo-environmental investigation and subsequent environmental
monitoring carried out at the site between November 2007 and January 2008.
1.4 Limitations
This report has been prepared on behalf of and for the sole use of Barteak Developments
Limited. Any third party relies on this report at its own risk unless it is the beneficiary of a
warranty executed by Faber Maunsell Limited specifically for the purpose of creating a duty to
it.
The interpretation of the geological and hydrogeological conditions at the site is based on an
assessment of published information and an extrapolation of point-source information using
geological experience. There is a degree of subjectivity in any interpretation. Groundwater
conditions are subject to variation, the range of which may not have been recorded within the
limited period of monitoring.
1 Introduction
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 4
The design of the ground investigation carried out in November/December 2007 and the
assessment are based on the assumption that the site of the will be developed generally in
accordance with the Masterplan drawing, drawing reference SK16.11.07A provided by Barteak
Developments Limited, reproduced in Appendix A. Should the site be developed for an
alternative use, it may be necessary to re-assess the results and conclusions of this strategy.
The effects of ground and water borne contamination on the environment are constantly under
review and authoritative guidance values are subject to change. The discussions and
conclusions presented in the report are based on the guidance available at the time this report
was prepared. No liability can be accepted for the retrospective effects of any changes or
amendments to the legislation or guidance.
The copyright in this document (including its electronic form) shall remain vested in Faber
Maunsell Ltd but the Client shall have a licence to copy and use the document for the purpose
for which it was provided. Faber Maunsell shall not be liable for the use by any person of the
document for any purpose other than that for which the same were provided by Faber Maunsell.
This document shall not be reproduced in whole or in part or relied upon by third parties for any
use whatsoever without the express written authority of Faber Maunsell.
Site Location and Background Information
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 6
2.1 Site Location
The Rugby Cattle Market site is centred on National Grid Reference (NGR) SP509757,
immediately south west of Rugby railway station, as shown on Figure 2.1.
The site consists of a roughly square area of land of approximately 4ha, which is owned by
Rugby Borough Council, together with an additional area to the north of approximately 1.2ha in
private ownership. The Council’s site is occupied largely by the existing cattle market with its
animal stalls, sheds and ancillary buildings in the centre of the site and two public car parks and
a small play area in the southern part of the site. The northern part of the development site is
occupied by the railway station car park in the north eastern corner and by Boults factory in the
north western part of the site.
The proposed development site is bounded to the north by Rugby railway station; to the west by
Railway Terrace; to the east by Murray Road; and to the south by Craven Road. The site
layout is shown on Figure 2.2.
2.2 Site History and Development Proposals
To investigate the previous activities on the site and the potential for past contaminative uses,
historical Ordnance Survey plans of the site and the surrounding area were reviewed for the
period 1889 to 1999. Details of the review and copies of the plans are provided in Faber
Maunsell report of March 2006.
It is understood that the site has been used as a livestock market since 1878. The south
eastern part of the site, now a car park, was used for animal slaughtering and meat processing
from before 1925 until at least 1960. The area of land in the north west of the site, now
occupied by Boults was used as the Tattersalls from at least 1905 until at least 1939. The plan
dated 1960 shows that this area is now occupied by a ‘depot’. The market is currently only in
use on Mondays of each week.
It is proposed that the area of the cattle market, Boults land to the north west and part of the
railway station car park are re-developed for a mixture of residential, commercial and
community uses. The proposed Masterplan for the site is provided at Appendix A. The
Masterplan shows residential development in the eastern half of the site with an hotel at the
northern end. The western half of the site will be re-developed with an area of employment in
the north west, public open space and a community centre in the central part and a nursing
home in the south western corner.
2.3 Geology
The geology of the site is taken from the BGS plans of the area and from the findings of the
ground investigations carried out at the site in January 2006 and in November/December 2007.
On the BGS 1:50,000 scale map, the site is shown as being underlain by the Jurassic, Lower
Lias Clay, consisting of a grey calcareous mudstone, with occasional cementstone bands. In
the south eastern corner, the Lower Lias is covered by the Wolston Clay, a stoneless clay and
silt. The results of the investigations in 2006 and 2007 confirm the presence of the Lower Lias
Clay but suggest that the clay is overlain by a variety of superficial deposits. Much of the cattle
market area has a surface covering of concrete and the car park areas have a covering of
asphalt gravel.
2 Site Location and Background
Information
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 7
2.4 Hydrogeology
It is likely that the clays and mudstone of the Lower Lias have a low primary permeability which
restricts the movement of groundwater. The cementstone bands also have a low primary
permeability but a higher secondary permeability imparted by the presence of fractures, which
facilitate groundwater movement. It is likely that the cementstone bands provide minor but
preferential groundwater flowpaths.
It is likely that the Wolston Clay has a low permeability which restricts vertical groundwater flow
and may support a minor perched water table in the overlying made ground.
The Lower Lias is designated as a non-aquifer in the Environment Agency ‘Groundwater
protection: policy and practice’’. The superficial deposits are classified as a minor aquifer.
There are no licensed groundwater sources within 1km of the site. Based on information
contained in the Rugby Borough Council Contaminated Land Strategy (June 2001), it is
understood that any private water supplies are located in rural areas of the borough and not
within Rugby town.
2.5 Hydrology
The cattle market site is located in the catchment of the River Avon, which flows westerly
approximately 700m to the north of the site (Figure 2.1). There are two licensed water
abstractions from the River Avon, approximately 800m and 900m north of the site. There are
no surface watercourses within 600m of the site.
2.6 Previous Investigations
A ground investigation was carried out at the site by Faber Maunsell Limited, on behalf of
Rugby Borough Council, in January 2006. The investigation was designed to identify the
presence of contaminated ground on the site, which could present a risk to human health and a
constraint on the site development. The investigation was restricted to that part of the site
owned by Rugby Borough Council.
The investigation comprised the drilling of 20 shallow probeholes to a maximum depth of 2m.
The locations of the probeholes are shown on Figure 2.3. Samples of the materials proved in
the probeholes were submitted for geochemical testing and a programme of groundwater and
ground gas monitoring was carried out in 10 probeholes which were equipped for monitoring.
2.6.1 Geology
The probeholes proved a surface layer of made ground/fill, which varied in thickness from
0.15m to 1.2m. The made ground comprised concrete hardstanding, angular sands and
gravels, bricks and general debris.
All of the probeholes proved a light grey clay and a brown sandy, silty clay with sand pockets
below the made ground across the whole site, in contrast to the BGS plan. The full thickness of
the superficial deposits was not proved due to the limited depth of the probeholes.
2.6.2 Soil quality
A total of 30 soil samples of the made ground and underlying natural deposits were analysed
for the presence of contamination. There was evidence of significant organic contamination
and locally elevated metals concentrations in the made ground. There was no evidence of
widespread significant contamination in the underlying superficial deposits. Elevated metal
concentrations were reported principally for arsenic, up to 56mg/kg; boron, up to 8.7mg/kg;
copper, up to 690mg/kg; lead, up to 1800mg/kg; nickel, up to 110mg/kg; and, zinc up to
850mg/kg.
The contamination in the made ground was associated principally with polycyclic aromatic
hydrocarbons (PAH), including benzo(a)pyrene (BaP). Total petroleum hydrocarbons were
recorded up to 17,000mg/kg and PAH(16) up to 1542mg/kg. BAP was recorded up to
120mg/kg. The organic contamination was attributed to the tarmac asphaltic gravel which has
been used as a surface covering to the car parks and which also is present in the sub-base
materials. Locally elevated concentrations of arsenic, nickel, lead and boron were present in
the made ground (Figure 2.4).
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 8
Apart from one sample in probehole WS6, on the southern edge of the site, contamination of
the natural deposits was limited to locally elevated concentrations of arsenic and boron, which
are present at much lower concentrations than in the made ground. From discussions with the
Contaminated Land Officer of Rugby Borough Council, it is understood that elevated arsenic
concentrations are present naturally in soils in the area and reflect the weathering of
argillaceous materials such as silt and clay.
Based on the findings of the soils analyses in 2006, it was concluded that the recorded levels of
soil contamination in the surface layer of made ground posed a risk to human health and, in the
absence of remedial measures, placed a constraint on any proposed development of the site.
2.6.3 Ground gases
The 10 monitoring probeholes were monitored for the presence of ground gases (methane,
carbon dioxide, oxygen, hydrogen sulphide and carbon monoxide) together with the gas flow
rate on three occasions in January 2006. Methane was recorded in two probeholes at
concentrations up to 2.4%v/v. Carbon dioxide was recorded in all the probeholes, with the
maximum recorded concentration of 10.2%v/v. Carbon dioxide above the guidance level of
5%v/v was reported in five of the probeholes. Elevated gas flow rates were not recorded in any
of the probeholes with a maximum flow of 0.7 l/hour.
2.6.4 Groundwater quality
Due to the limited depth of the probeholes, it only was possible to recover groundwater samples
from five of the probeholes. The remaining five probeholes were dry.
The laboratory analyses of the samples showed generally minor contamination of the
groundwater principally with hydrocarbons and locally ammoniacal nitrogen. The recorded
hydrocarbon levels generally were low at less than 0.3ng/l, apart from the sample from
probehole WS20 on the central part of eastern site boundary, which recorded TPH (C5-C40) at
16.18mg/l. Slightly elevated ammoniacal nitrogen concentrations were recorded for the
samples from probeholes WS12 in the north western part of the site and WS15 in the centre of
the site at 1.1mg/l and 1.2mg/l respectively. No elevated PAH levels were recorded.
2.7 Ground Investigation 2007
The ground investigation carried out in November and December 2007 was designed to extend
the findings of the 2006 investigation. The investigation was designed to:-
• clarify the volume of contaminated materials on the site;
• investigate the ground conditions beneath Boult’s land and the north eastern area of
the site for which access was not possible in 2006;
• confirm the groundwater quality and the impact of contaminated ground at the site on
groundwater;
• provide sufficient data to facilitate human health and groundwater risk assessments
and the design of a contaminated land remediation strategy; and,
• provide geotechnical information for foundation design purposes.
The investigation consisted of the excavation of 4 trial pits and the drilling of 7 probeholes using
a window sampling technique and 7 ground investigation boreholes using a percussive, cable –
tool drilling technique. Samples of the materials proved in the trial pits, probeholes and
boreholes were submitted for both geotechnical and geochemical analysis. The trial pits were
excavated to a depth of 4m. The probeholes were drilled to depths of 4m to 6m and the
boreholes to 10m. The logs of the trial pits, probeholes and boreholes are provided at
Appendix B. The locations of the trial pits, probeholes and boreholes are shown on Figure 2.5.
Following completion of the drilling, groundwater samples were collected from three probeholes
and three boreholes as part of a programme of environmental monitoring.
An assessment of the results of the geo-technical testing of the soil samples to inform the
foundation designs is provided in a separate document and is not considered in the
contaminated land assessment.
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 9
A total of six soil samples were submitted for analysis of the suite of contaminants listed in
Table 2.1. The samples were collected from locations in the northern part of the site, which
was not assessed in the 2006 investigation. The laboratory data sheets for the soils analysis
are presented at Appendix C. The six groundwater samples were analysed for the parameters
listed in Table 2.2 and the laboratory data sheets are provided at Appendix D. An assessment
of the ground and groundwater conditions based on the findings of both the 2006 and 2007
investigations is provided in Section 3.
Table 2.1 Soils analysis suite
Arsenic, cadmium, chromium, lead, mercury, selenium, boron (water soluble), copper, nickel, zinc, polyaromatic hydrocarbons (PAH16 speciated by GC-MS), total petroleum hydrocarbons (TPH by GC-FID), sulphide, sulphate (water soluble) and pH. SVOC and VOC. Asbestos. Soil Organic Matter.
Table 2.2 Groundwater analysis suite
Arsenic, cadmium, chromium, lead, mercury, selenium, boron, copper, nickel, zinc, polyaromatic hydrocarbons (PAH16 by GC-MS), cyanide, extractable petroleum hydrocarbons (EPH by GC-FID), sulphide, sulphate and pH.
2.8 Site Condition Survey
Prior to the ground investigation, Faber Maunsell Limited was commissioned by Rugby Borough
Council to undertake a health and safety risk assessment of the cattle market site. The
purpose of the survey was to identify to the Council hazards currently on the site and the
potential risk posed by these hazards to the health and safety of those entering the site and to
enable the Council to take appropriate precautions to reduce the health and safety risks
following closure of the Cattle Market.
The main conclusions of the survey were:-
• the need to prevent as far as possible unauthorised access to the site.
• the need to restrict access to buildings on the site.
• the need to install appropriate signage to identify potential risks.
• the need to review the existing Type 3 asbestos survey to clarify potential risks
associated with the known presence of asbestos on the site.
Further details of the survey are provided in the Faber Maunsell report of September 2007.
Ground and Groundwater Conditions
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 11
3.1 Geology.
The geology of the site has been assessed from an interpretation of the BGS plans and the
results of the ground investigations carried out in 2006 and 2007. The site is underlain by a
variable thickness of made ground, overlying superficial deposits which rest on the Jurassic
Lias Clay.
The made ground comprises a surface concrete slab and associated sub-base layer over much
of the northern half of the site and in the southern area by mainly an asphaltic gravel which
forms the surface of the car parking areas. The sub-base comprises a granular aggregate of
brick, clinker, ash and gravel. The made ground typically is approximately 0.5m thick, apart
from the north eastern part of the site where the made ground is 1.0m to 2.4m thick. Figure 3.1
shows the variation in the thickness of the made ground across the site.
The superficial deposits beneath the made ground consist of a mixture of stony clay and sands
and gravels varying in thickness between 1.1m in trial pit TP30 and 3.95m in borehole CP26.
Locally the sands and gravels are very thin or absent and the made ground rests directly on the
Lias Clay, as in probehole WS15 and trial pit TP22. Figure 3.2 shows the thickness of the
sands and gravels across the site. Figure 3.3 shows the depth to the surface of the Lias Clay.
In the southern part of the site, the superficial deposits consist principally of a stiff, brown and
grey stony clay. From Figure 3.3, it is interpreted that the surface of the Lias Clay typically is
more than 1.5m below the existing ground level and increases to the north of the site to more
than 4.5m.
Sands and gravels are developed mainly below the central and northern parts of the site. The
sands and gravels thicken to the north. In Boult’s land in the north western part of the site, the
sands and gravels are 2.6m to 4m thick and consist of a medium-dense, orangish-brown clayey
sand with sandstone and flint gravel. In this area the surface of the Lias Clay is at a depth of up
to 4.7m.
The sands and gravels are interpreted as a river terrace deposit associated with the River Avon
located to the north of the site. Figure 3.4 shows a geological cross-section running north-south
through the site. To the north of the site, the land falls by approximately 5m. The BGS
1:10,000 scale plan shows that the Lias Clay crops out at the base of the slope to the north of
the site.
The Lias Clay which underlies the superficial deposits consists of a firm to stiff, grey clay and
silt, locally grading in to a weak mudstone. At the junction with the clay, the overlying sands
and gravels are described as soft, possibly reflecting the presence of groundwater perched on
the clay.
3.2 Soil Chemical Results
A limited number of soil samples were analysed as part of the 2007 investigation. In the 2006
investigation, 30 soil samples had been analysed. In the recent investigation, six soil samples
were submitted for analysis from five locations in the northern half of the site, principally where
data was lacking from the 2006 study. The laboratory data sheets for the 2007 samples are
provided at Appendix C. A summary of the laboratory analyses for both sets of samples is
provided in Table 3.1.
Based on the results of the laboratory analyses of the soil samples, a risk assessment was
carried out to determine the potential impacts on human health. Soil Guideline Values (SGVs)
published by DEFRA as part of the CLEA programme, have been used to indicate the potential
risks to human health. At the time of preparing this assessment, ten SGVs have been
published.
3 Ground and Groundwater Conditions
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 12
As the site redevelopment proposals include residential usage, the generic model ‘residential
with plant uptake’ has been used in the assessment. This is considered the most appropriate
model for use in screening the soils contaminant concentrations at the site. The recorded
concentrations of contaminants have been compared against the SGVs derived for a residential
with plant uptake land use.
Where available, the SGVS have been used to indicate the potential chronic risks to human
health. In the absence of an SGV for a particular contaminant, Soil Screening Values (SSV)
have been developed in accordance with the Environment Agency and DEFRA Contaminated
Land Reports CLR 9 and 10 and the CLEA Briefing Notes 1-4.
For the phytotoxic metals of copper, zinc and boron, which rarely pose a risk to human health
unless present in very high concentrations, alternative guidance values have been used. The
copper and zinc concentrations have been compared against guidance values specified in the MAFF document ‘Code of Good Agricultural Practice for the Protection of Soil’’(1993) In this
document, a guidance concentration of 200mg/kg copper and 300mg/kg zinc is specified for
soils with pH above 7.
There currently is no published guidance level for boron in soils. Previously trigger levels were
specified in the now-withdrawn ICRCL 59/83 guidance document. Whilst it is recognised that
the ICRCL guidance no longer is used, in the absence of alternative acceptable guidelines it is
considered that the former ICRCL guidance level of 3mg/kg provides an initial screening value
for boron.
Guidance on polycyclic aromatic hydrocarbons (PAH 16) also was provided in the ICRCL 59/83
document. However, emphasis is now placed on the individual compounds, such as
benzo(a)pyrene [B(a) P], a potential carcinogen. The acceptable concentration of B(a)P varies
according to the individual site conditions. Discussions with the National House Building
Council and experience from other similar situations suggest that an acceptable B(a)P
concentration for a residential end-use is in the range 1mg/kg-2mg/kg.
For the Rugby Cattle Market site, the former ICRCLl trigger value of 50mg/kg for PAH (16) has
been used as an initial screening value with a more specific assessment placed on the B(a)P
concentration, adopting a conservative guidance value of 1mg/kg.
The analysis of the samples taken in 2006 showed elevated hydrocarbon contamination of the
made ground, particularly in the south eastern part of the site associated with the surface layer
of asphaltic gravel on the car parking area. Elevated metal concentrations also were recorded.
In the 2007 study, the soil samples analysed were all from the sub-base underlying the
concrete hardstanding of Boult’s land and the cattle market. In contrast to the 2006 samples,
none of the samples showed evidence of significant contamination.
For the majority of the 2007 samples, the reported metal concentrations were significantly
below the CLEA and MAFF soil guidance values. Arsenic concentrations exceed the CLEA
SGV of 20mg/kg in two samples from probeholes WS31 and WS33 on Boult’s land, with
concentrations of 33mg/kg and 44mg/kg respectively. The sample from probehole WS31 also
recorded a high zinc concentration of 500mg/kg, above the MAFF guideline value of 300mg/kg.
None of the other soil samples recorded metal concentrations above the guidance levels, with
many of the samples recording levels at only a fraction of the trigger values.
None of the six samples analysed recorded elevated hydrocarbon levels. Total extractable
petroleum hydrocarbon (EPH) varied between 8mg/kg and a maximum 110mg/kg in the sample
from probehole WS33 at 0.4m depth. The total hydrocarbon levels are significantly lower than
recorded in 2006. Total PAH (16) concentrations also were low varying from less than
0.1mg/kg to a maximum 25mg/kg, in the sample from trial pit TP22 on the northern edge of the
site at a depth of 0.5m. The B(a)P concentration varied between less than 0.1mg/kg and a
maximum 12mg/kg in the sample from probehole WS27 at 0.2m depth.. Probehole WS27 is
located in the eastern part of the cattle market area.
The absence of significant contamination of the made ground beneath the northern part of the
site, beneath the concrete hardstanding, is consistent with the findings of the 2006 survey, in
which the bulk of the contamination was attributed to the asphaltic gravel covering the car
parking areas. The asphaltic gravel is absent in the northern part of the site.
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 13
Asbestos was not identified in any of the six soil samples analysed in the 2007 investigation.
Table 3.1 Summary of the soil analytical results – 2006 and 2007
Parameter Min Max
Guidance
Values
(SGV/MAFF1/
ICRCL2/DIV
3)
No. of
samples
No. of
samples
above
guidance
values
No of
samples
below limit
of detection
Arsenic 6.4 56 20 36 8 0
Boron <0.5 8.7 32
36 8 11
Cadmium <0.5 1.9 2 36 0 8
Chromium 11 69 130 36 0 0
Copper 7.3 690 2001
36 2 0
Lead 7.9 1800 450 36 3 0
Mercury <0.3 2.8 8 36 0 28
Nickel 5.9 110 50 36 3 0
Selenium <1 4.5 35 36 0 12
Zinc 27 850 3001
36 3 0
Free cyanide <5 203
30 0 30
Total cyanide <5 1/203
30 0 30
pH 7.3 11.9 36 0 N/A
Sulphide <10 1700 2502
30 1 10
Thiocyanate <5 502
30 0 30
TPH (C10-C40) 8 17,000 50/50003
16 8/4 0
PAH(16) <0.1 1542.26 502 36 12 9
B(a)P <0.1 120 1 36 17 11
Benzene <0.01 <0.025 0.05/13
16 0/0 16
Toluene <0.01 <0.025 3 16 0 16
Ethyl-
benzene <0.01 <0.025 9 16 0 16
Xylene <0.01 <0.025 6 16 0 16
MBTE <0.025 n/a 10 0 10
Phenol <0.1 0.26 78 36 0 35
All units as mg/kg except pH.
KEY
1 – MAFF Soil Guidance value
2 – ICRCL 59/83 trigger value
3 – Dutch action/intervention values
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 14
3.3 Hydrogeology
3.3.1 Groundwater level
Groundwater is present in the sands and gravels. It is considered that the groundwater in the
sands and gravels is perched on the underlying low permeability Lias Clay. A programme of
groundwater level monitoring has been carried out and the results of the monitoring are
presented at Appendix E. Based on the information collected on 9 January 2008, a
groundwater contour plan for the sands and gravels has been prepared (Figure 3.5). The
groundwater depth varies across the site from 0.5m below ground level (bgl) in borehole CP21
in the north eastern part of the site to approximately 3mbgl in probehole WS31 in the north
eastern corner of the site. Groundwater in the sands and gravels flows in a north north
westerly direction from 96.2mAOD in probehole WS7 in the car park in the south east of the site
to 92.8mAOD in probehole WS31 in the north western corner of Boult’s land.
3.3.2 Groundwater quality
Groundwater samples taken in the 2006 investigation showed evidence of slight contamination
of groundwater in the sands and gravels, principally by hydrocarbons. Figure 4.5 of the Faber
Maunsell report of March 2006 provides a summary of the results of the groundwater sampling.
As part of the 2007 investigation, six groundwater samples were collected. Four samples were
collected from locations in the northern part of the site (CP21, WS23, WS27 and WS31), down
hydraulic gradient of the area of known soil contamination. The remaining two samples were
collected from boreholes CP32 and CP36 located in the car parking areas in the south of the
site. The samples were analysed for the suite of parameters listed in Table 2.2. The laboratory
data sheets are provided at Appendix D.
The results of the analyses show no evidence of groundwater contamination. Total
hydrocarbons were not recorded above the limit of detection of 0.01mg/l in any of the samples.
Individual PAHs also were not recorded above the limit of detection of 0.1µg/l. The
concentrations of the remaining parameters were compared against Environmental Quality
Standards (EQS) published by the EA. As there currently are no EQS published for
groundwater, the EQS for ‘freshwaters’ were used for assessment purposes. For the majority
of the metal and metalloids, the recorded levels were at or below the respective limits of
detection and below the EQS.
The groundwater is slightly acidic at pH 6.5 to 6.9, apart from the sample from borehole CP21 on the northern edge of the site, which recorded an anomalous alkaline pH of 11.6. The sample
taken from borehole CP36 in the southern part of the site recorded an anomalously high
sulphate concentration of 580mg/l, compared with the other samples in which the sulphate
concentration varied between 50mg/l and 82mg/l.
Based on the results of the groundwater quality monitoring in December 2007, it is concluded
that there is no evidence of contaminated groundwater beneath the Rugby Cattle Market site.
Elevated concentrations of contaminants observed in the made ground are not reflected in the
groundwater. Accordingly, it is concluded that contaminants in the made ground are present in
non-mobile forms and do not present a risk to groundwater quality.
3.4 Ground gases
Ground gas monitoring was carried out at the site on three occasions. The results of the
monitoring are provided at Appendix E.
The results show that methane above the limit of detection of 0.1%v/v was not detected on the
site. Carbon dioxide, above the limit of detection, was recorded in seven of the monitoring
points on one or more occasions. The highest concentration of 5.9%v/v was recorded in
probehole WS14 in the northern part of the site. None of the monitoring points recorded an
elevated gas flow rate. Gas flow rates were negligible on all occasions, with a maximum flow
rate of 0.4 l/hour.
No carbon monoxide or hydrogen sulphide was recorded on the site.
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 15
Guidance documents state that if methane exceeds 1%v/v and/or carbon dioxide exceeds
5%v/v together with a measurable gas flow rate, gas control measures should be incorporated
in the building design to protect the building from the ingress of ground gases. Carbon dioxide
above 5%v/v has been recorded in probeholes WS11 and WS14. Based on the results of the
monitoring, it is considered in the absence of elevated gas levels together with the absence of
elevated gas flow rates that no gas control measures will be needed on the site.
3.5 Summary
Based on the results of the ground investigations carried out in 2006 and 2007, it is considered
that there is ground contamination on the site which presents a risk to human health and a
potential constraint to the proposed development. The highest levels of ground contamination
are associated with the thin surface layer of made ground principally in the car parking areas in
the south and east of the site.
There is no evidence of groundwater contamination in the sands and gravels beneath the site.
It is considered that the contaminants recorded in the made ground on the site are present in
immobile forms and do not present a risk to the quality of the groundwater.
No methane has been recorded at the site. Slightly elevated carbon dioxide levels, above the
trigger level of 5%v/v, have been recorded locally on the site. However as the gas flow rates
are negligible, it is considered that the carbon dioxide levels do not present a major risk.
Conceptual Model and Risk Assessment
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 17
4.1 Introduction
Qualitative and quantitative risk assessment were carried out to identify the principal aspects
concerning the presence of contamination at the site and its likely impacts.
To assess the potential environmental impacts associated with the proposed development, a
qualitative risk assessment has been undertaken using the source-pathway-receptor approach
promoted by DEFRA and the Environment Agency. For there to be an identifiable risk, not only must there be contaminants present on the site (source) ie contaminated ground, leachate,
landfill gas but also there must be a receptor and a pathway which allows the source to reach
the receptor. All three elements must be present to form a pollutant linkage before there can be
a potential risk to specific receptors. In accordance with standard practice, a conceptual model
of the potential or actual pollutant linkages was developed for the proposed scheme, to
evaluate the likely impacts.
4.2 Conceptual Model
A conceptual model of the Rugby Cattle Market site has been developed based on the findings
of the 2006 and 2007 investigations and the results of subsequent environmental monitoring.
The site is underlain by a generally thin layer of made ground which overlies a variable
thickness of sands and gravels and clays. The sands and gravels rest on the Lias Clay. The
sands and gravels are water-bearing and groundwater beneath the site flows in a north north
westerly direction.
4.2.1 Sources
The principal source of contamination on the site is the thin layer of made ground, which locally
contaims elevated levels of contaminants, principally hydrocarbons.
4.2.2 Receptors
The main receptors which may be susceptible to contamination arising on or beneath the site
are:-
• Construction staff involved in the proposed redevelopment of the site;
• Future site occupants and end-users;
• Groundwater in the sands and gravels; and,
• Surface water features, including site drainage and the River Avon.
4.2.3 Pathways
The principal routes by which the source of contamination may impact on sensitive receptors
include:-
• Inhalation of dust and contact with or ingestion of contaminated soils;
• Ingestion of plants/vegetables grown on the site;
• Exposure to rainfall and mobilisation of soluble contaminants during construction;
• Leaching of soluble contaminants to groundwater in the sands and gravels; and,
• Movement of soluble contaminants in the groundwater to the surface drainage system.
Based on the conceptual model, it is concluded that currently there are plausible pollutant
linkages on the site which potentially pose a risk to human health and controlled waters
(surface water and groundwater). The results of the groundwater quality monitoring
demonstrate that the linkage to groundwater has not been realised. However, the presence of
4 Conceptual Model and Risk
Assessment
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 18
elevated contaminant levels in the made ground across parts of the site render the site currently
unsuitable for the proposed development in the absence of remedial measures. The principal
area of concern is the residential development, including the garden areas, proposed for the
eastern and south eastern parts of the site, where there is known hydrocarbon contamination of
the made ground.
In order to render the site suitable for the proposed development, remedial measures will be
required to remove the potential risks to human health from the contaminated soils present on
the site. The contamination is limited to the made ground and, in particular, to the asphaltic
gravel surfacing of the car parking areas.
4.3 Remediation Strategy
4.3.1 Methodology
The principle of any remediation strategy adopted at the site is to disrupt any pollutant linkages
between the source of contamination and receptors (site construction workers and end users of
the site). The remediation scheme also will be developed to re-use as much material as
possible and thereby minimise the volume of material removed off-site. Based on a preliminary
assessment of the proposed development, it is estimated that there is a surplus volume of
material on the site of approximately 10,000m3.
Based on the results of the soils analyses, it is considered that contamination generally is
restricted to the surface layer of made ground. Apart from the north eastern corner of the site,
the made ground typically is less than 1m thick and consists of concrete slabs and sub-base
beneath Boult’s land and much of the cattle market; asphaltic gravel across the car parking
areas in the south and east; and, general fill. Including the concrete slabs, it is estimated that
the volume of made ground on the site is approximately 29,000m3, of which the concrete slabs
comprise approximately 4,600m3.
Made ground contaminated by hydrocarbons in the southern and eastern parts of the site
covers an area of approximately 21,800m2 and has an estimated volume of approximately
9950m3. Chemical analysis of the sub-base materials beneath the concrete slabs suggests that
this material is uncontaminated and does not pose a risk to human health. This material has a
volume of approximately 14,200m3. A summary of the made ground is provided in Table 4.1. It
is considered that both the concrete and the underlying sub-base are suitable for re-use on the
site with no restrictions.
Table 4.1 A summary of the made ground
Made ground Estimated volume
(m3)
Concrete slabs 4,600
Sub-base to concrete slabs and other
uncontaminated fill
14,200
Contaminated ground – principally car park
surfacing
9,950
TOTAL 28,750
It also should be recognised that there are negligible soils on the site and that it will be
necessary to import soils for the residential gardens, the area of public open space and the
‘green’ landscaped areas.
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 19
4.3.2 Remediation Strategy
The most sensitive areas from a ground contamination perspective are in the eastern part of the
site proposed for residential end-use, particularly the 26 houses with gardens, as these present
a greater risk of exposure of end-users to the contaminated ground. Other than the two houses
at the northern end of this area, the made ground underlying the proposed residential area is in
the order of 0.5m thick. There is a need to import subsoil and topsoil to form the gardens to the
houses. The soils in the garden areas will consist of a minimum 0.1m topsoil and 0.5m subsoil.
It is proposed that across the whole of the proposed residential area, the surface is lowered by
a minimum of 0.5m, which will result in the removal of the majority of the contaminated ground.
To achieve the final profile of the residential area, clean subsoil and topsoil to a minimum
combined thickness of 0.6m will be imported to the garden areas. The landscaping areas will
be restored by a minimum 0.1m topsoil overlying 0.2m subsoil and 0.2m of clean material
recovered from other parts of the site. The roads, car parking areas and the ‘squares’ will
include a sub-base layer of crushed concrete and other clean materials recovered from the site.
Where the contaminated ground is greater than 0.6m thick in the eastern part of the site, the
contaminated material will be excavated to a minimum depth of 0.6m and clean material
covered with subsoil and topsoil will be replaced. The presence and thickness of the soil layers
will depend on the proposed use for that specific part of the site; such as residential gardens,
car parking areas etc.
The contaminated materials removed from the eastern part of the site will be deposited in the
western half of the site beneath the area of public open space in the central part of the western
area and beneath the community area, the squares and the landscaped areas around the
Nursing Home. Where the contaminated material will not be covered by an impermeable layer,
the material will be covered by a minimum thickness of 0.5m of topsoil, subsoil and clean
materials. Covering of the contaminated materials either beneath hardstanding or a minimum
0.5m thickness of clean cover will break the pollutant linkage between users of these parts of
the site and the contaminant source and thereby reduce the risk to human health.
Whilst every effort will be made to minimise the volume of material removed from the site for
disposal, based on a preliminary assessment of the development proposals, it is estimated that
there is a surplus of material on the site of approximately 10,000m3. This material will be
uncontaminated and will be suitable for re-use, recycling or for disposal at a site which has a
registered exemption from Waste Management Licensing.
Whilst much of the site has been assessed for its contaminant potential, the risk of excavating
currently unidentified small areas of contamination cannot be discounted. In the event that
excavations prove additional areas of visually contaminated ground consistent with
hydrocarbon contamination, the material will be isolated on the site and samples taken for
laboratory testing for the contaminant suite in Table 4.2. The management of these materials
will be determined, based on the results of the laboratory testing.
It is considered that the proposed methodology for removing contaminated materials from the
sensitive residential area of the site and covering this material beneath impermeable cover or
beneath a minimum 0.5nm of clean soil cover in less-sensitive areas effectively will break the
pollutant linkage and minimise the risk of adverse impacts on human health.
4.4 Soils Testing
It will be necessary to ensure that the development of the site does not cause an increased risk
to human health or to groundwater. All material imported to the site, in particular subsoil, will be
tested to determine its suitability for use on the site in both residential gardens and landscaping
areas. The imported material will be tested for the contaminant suite listed in Table 4.2, as part
of a validation testing exercise. The purpose of the testing is to validate the quality of any
materials imported to the site and to determine the contaminant concentrations of materials
which may be retained in-situ or redistributed across the site.
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 20
Table 4.2 Validation and contamination testing suite for soils
Arsenic, cadmium, chromium, lead, mercury, selenium, boron (water soluble), copper, nickel, zinc, polyaromatic hydrocarbons (PAH16 speciated by GC-MS), total petroleum hydrocarbons (TPH by GC-FID), sulphide, sulphate (water soluble) and pH. SVOC and VOC. Asbestos. Soil Organic Matter.
4.5 Compliance with Legislation
The need to regrade the made ground and to re-deposit contaminated materials in other areas
of the site to achieve the development site levels, potentially is the subject of Waste
Management Licensing. It is recommended that confirmation is obtained from the Environment
Agency that this operation is exempt from Waste Management Licensing or complies with its
policy on necessary regrading works.
Any materials removed off-site for treatment or disposal should be managed in accordance with
the Duty of Care. The deposit of any contaminated materials to landfill can benefit from an
exemption from Landfill Tax, provided that this is obtained in advance of materials leaving the
site.
4.6 Ground gases
The results of ground gas monitoring at the site have shown that methane is not present above
the limit of detection and that carbon dioxide is slightly elevated locally across the site.
However gas flow rates are very low, with a maximum recorded flow of 0.4 l/hour.
Guidance on the risks posed to developments from the presence of ground gases is provided in the NHBC document of March 2007, entitled ‘Guidance on Evaluation of Development
Proposals on Sites where Methane and Carbon Dioxide are Present’. Based on the risk
assessment in Table 14.1 of the document, and the maximum recorded carbon dioxide
concentration of 5.9%v/v, a gas screening value of 0.024 l/hour is derived. Using this gas
screening value as an initial guide, it is considered that the ground gas conditions at the site do
not pose a significant risk to the development. Guidance provided in Table 14.2 of the NHBC
document suggest that either no gas protection measures are required or that only low-level
gas protection measures will be necessary.
Only limited ground gas monitoring has been carried out at the site. In order to confirm the
need, if any, for gas protection measures it is recommended that further ground gas monitoring
for methane, carbon dioxide, oxygen, carbon monoxide and hydrogen sulphide together with
gas flow is carried out monthly at the site.
4.7 Soakaways
As part of the scheme development, there is a proposal to use soakaways to dispose of surface
drainage. The effectiveness of soakaways depends on the thickness of the unsaturated zone
and the nature of the underlying materials. It is considered likely that the sands and gravels
provide conditions suitable for the use of soakaways.
However, in the southern part of the site, the sands and gravels are relatively thin and it is
considered unlikely that soakaways will be effective in this part of the site. The sands and
gravels thicken to the north and the groundwater table typically is at a depth of up to
approximately 3m. It is likely that soakaways in the northern part of the site will be effective.
However, the land surface to the north of the site falls significantly. Geological information
suggests that the Lower Lias Clay outcrops to the north of the site. Accordingly, it is considered
likely that there is a seepage face to the north of the site at the junction between the sands and
gravels and the Lias Clay. There is a risk that additional discharges to the sands and gravels
through soakaways may increase the rate of seepage, potentially causing flooding to the land to
the north of the site.
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 21
If the proposal to use soakaways is progressed, it is recommended that soakaway tests are
carried out to confirm the suitability of the underlying geology and that a detailed assessment of
the drainage on the lower land north of the site is carried out to assess the likely impacts.
Conclusions and Recommendations
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 23
5.1 Conclusions.
Based on an appraisal of the results of the two ground investigations carried out at the site in
2006 and 2007, the following conclusions can be drawn:-
• The site has been used as a livestock market and associated activities since
approximately 1878.
• The market area occupies the central part of the site, owned by Rugby Borough
Council with mainly hardstanding and car parking areas in the east and south. The
northern part of the development area is under third party ownership.
• The surface of the site is covered by a layer of made ground, typically in the order of
0.5m thick but locally up to 2.4m. The made ground consists of a mixture of concrete
and underlying sub-base layer and fill (asphaltic gravel) used to surface the car parking
areas in the south and east of the site.
• The made ground overlies superficial deposits of sands and gravels with clays. The
superficial deposits overlie the Lias Clay.
• The sands and gravels thicken to the north west where they are up to 4m thick.
• The sands and gravels are water-bearing. The groundwater depth varies between
0.5m and 3m below ground level. Groundwater in the sands and gravels flows in a
north north westerly direction.
• The made ground on the site locally is contaminated, mainly by hydrocarbons in the
southern and eastern parts of the site, where contamination is associated with the
surface cover to the car parks of asphaltic gravel. Locally, elevated metal
concentrations, in particular arsenic, lead, nickel and zinc also are present in the made
ground.
• There is no evidence of contamination of the groundwater in the sands and gravels.
• Contamination present locally in the made ground does not pose a risk to groundwater
quality but locally does pose a constraint on the proposed development of the site,
particularly for those areas of proposed residential development. It is concluded that
remedial measures are required to render the site suitable for the proposed
development.
• There is no evidence for the presence of ground gases at elevated concentrations on
the site. Gas flow rates are low and it is considered that at worst only low level gas
protection measures will be required.
• The proposed contaminated land remediation strategy includes the need for the
redistribution of contaminated materials around the site away from the areas proposed
for residential development. The contaminated materials should be placed below lower
sensitivity areas in the west of the site, such as car parks, landscaped areas or floor
slabs or in open spaces provided that the materials are covered with clean soils to
disrupt any pollutant linkages.
5. Conclusions and Recommendations
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 24
5.2 Recommendations
The contaminated land remediation strategy has been prepared to minimise the risks to human
health. In order to confirm the suitability of the strategy, it is recommended that:-
1. once the development proposals have been finalised, the contaminated land strategy should
be reviewed to ensure that the detailed remediation proposals reflect the final development of
the site.
2. ground gas monitoring at the site is continued on a monthly basis to identify variations in the
gas (methane, carbon dioxide, oxygen, carbon monoxide and hydrogen sulphide)
concentrations and flow rates and the need for the inclusion of gas protection measures as part
of the final scheme.
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 25
Appendix A
Site Masterplan 2007 (SK16.11.07A)
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 26
Appendix B
Trial pit, probehole and borehole logs 2007
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 27
Appendix C
Laboratory data sheets for soil samples 2007
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 28
Appendix D
Laboratory data sheets for groundwater samples 2007
Faber Maunsell Contaminated Land Remediation Strategy: Rugby Cattle Market 29
Appendix E
Groundwater level and ground gas monitoring results