Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01

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Network Rail Oxford Corridor Phase 2 Capacity Improvement Scheme

Town and Country Planning (Environmental Impact Assessment) Regulations 2017

Network Rail

Oxford Corridor Phase 2 Capacity Improvement Scheme

Environmental Impact Assessment – Appendix 7.2: Preliminary Risk Assessment

Document Reference 163390-JAC-REP-EEN-070002

Author Jacobs

Date June 2021

Revision Number A01

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Network Rail Oxford Corridor Phase 2 Capacity Improvement Scheme

Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01

Environmental Impact Assessment – Appendix 7.2: Contaminated Land Risk Assessment

Document Version Control

Version Date Author Reviewer Approver

A01 Jun 2021 J. Thompson & M. Williams A. Naik F. Giacomello

Report for: Authored by:

Network Rail Jacobs SN1 1180 Eskdale Rd Station Road Winnersh Swindon Reading SN11DG RG41 5TU

© Copyright 2021 . The concepts and information contained in this document are the property of Network Rail. Use or copying of this document in whole or in part without the written permission of constitutes an infringement of copyright.

Limitation: This document has been prepared on behalf of Network Rail, and for the exclusive use of Network Rail, and is subject to, and issued in accordance with, the provisions of the contract between Jacobs and the Network Rail. Jacobs accepts no liability or responsibility whatsoever for, or in respect of, any use of, or reliance upon, this document by any third party.

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 Contents

1. INTRODUCTION ...... 1 2. HISTORICAL REPORTS ...... 2 2.2 Oxford Corridor Capacity Improvement Phase 1 and Phase 2 Ground Investigation Report, September 2014...... 3

2.3 Contaminated Land Risk Assessment October 2014 ...... 7

2.4 Geo-environmental Summary Memorandum, 2014 ...... 8

2.5 Oxford Corridor, Down Sidings Contaminated Land Study Report, April 2018 ...... 9

2.6 Oxford Corridor, Phase 2, Detailed Design Environment Management Plan, GRIP Stage 5 ...... 12

3. CONCEPTUAL MODEL ...... 13 3.1 Legislative Background and Assessment of Risk ...... 13

3.2 Conceptual Model ...... 15

3.3 Preliminary Risk Assessment ...... 16

3.4 Conclusions ...... 24

REFERENCES ...... 26

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 Tables

Table A2.1: Historical reports ...... 2

Table A2.2: Groundwater strikes ...... 5

Table A2.3: Summary of boreholes from Roger Dudman Way investigation ...... 9

Table A3.1: Classification of consequence (based on CIRIA, 2001) ...... 13

Table A3.2: Estimation of likelihood ...... 14

Table A3.3: Risk matrix – Risk ratings ...... 14

Table A3.4: Risk descriptions ...... 15

Table A3.5: Potential sources of contamination ...... 15

Table A3.6: Potential pathways ...... 16

Table A3.7: Conceptual model and risk assessment - Sheepwash Bridge replacement ...... 18

Table A3.8: Conceptual model and risk assessment - Roger Dudman Way, western entrance, Platform 5 ...... 19

Table A3.9: Conceptual model and risk assessment - Platform 5 and subway ...... 20

Table A3.10: Conceptual model and risk assessment - Botley Road Bridge widening ...... 21

Table A3.11: Conceptual model and risk assessment - Becket Street station car park and temporary Co-operative Childcare ...... 22

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01

1. INTRODUCTION

1.1.1 This Contaminated Land Risk Assessment takes into account geology and soils baseline data, potential sources of contamination identified in the review of current and historical land uses and previous ground investigations results. This information is used to create a conceptual model and risk assessment.

1.1.2 A review has been undertaken of historical reports from the previous stages of the Oxford Corridor Phase 2 Scheme.

1.1.3 The reports’ content and relevance to Chapter 7 Geology and Soils in Volume 2 of the Environmental Statement have been reviewed (e.g. ground investigations data, chemical analysis, groundwater, and ground gas monitoring). These reports are not presented in their entirety within the Environmental Statement. Rather a summary of the findings of each of the reports is given within this appendix. The reports themselves can be made available upon request if required. Contamination noted from these reports is included in the Conceptual Model and Risk Assessment within this appendix.

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 2. HISTORICAL REPORTS

2.1.1 The historical reports in Table A2.1 have been prepared by Halcrow – Tata Joint Venture (THJV). They are reviewed and summarised within this appendix.

Table A2.1: Historical reports

Year Title September Oxford Corridor Capacity Improvement Phase 1 and Phase 2 Ground 2014 investigation Report * October 2014 Oxford Corridor Capacity Geo-Environmental Summary Memorandum October 2014 Oxford Corridor Capacity Improvement - Contaminated Land Risk Assessment June 2017 Oxford Corridor Roger Dudman Way Factual Ground Investigation Report April 2018 Oxford Corridor Down Sidings Contaminated Land Study Report November Oxford Corridor Phase 1 Design Environmental Management Plan 2020 * This report includes previous ground investigations by: MLM, Bridgeway Consulting, THJV and Global Rail Consulting

2.1.2 A summary of the contamination identified in previous ground investigation reports from Table A2.1 and potential sources of contamination identified within the study area are bulleted below:

• Made ground found across the site in the historical ground investigations including asbestos where tested (within red line boundary);

• Hydrocarbon contamination found in groundwater sampled from a borehole at Osney Lane footbridge (location shown in Figure 7.2) (outside red line boundary);

• Historical land uses including sidings and depots at Roger Dudman Way car park (outside red line boundary);

• Former diesel tanks located within the Down Carriage Sidings associated with historical hydrocarbon contamination (outside red line boundary);

• Diesel spill at Castel Mill redevelopment site (outside red line boundary);

• Three historical landfills (outside red line boundary); and

• Historical industrial land use including Tallow Factory, Eagle Foundry (Iron and Brass) and Ink Works (outside red line boundary).

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 2.2 Oxford Corridor Capacity Improvement Phase 1 and Phase 2 Ground Investigation Report, September 2014.

2.2.1 THJV was commissioned by Network Rail to undertake a ground investigation to provide the required ground information to complete the Oxford Corridor Capacity Improvement Scheme design to Approval in Principal (THJV, 2014a).

2.2.2 The area covered in this report is much larger than the current study area. In the current review focuses on the information provided within the geology and soils study area as defined in Chapter 7 within Volume 2 of the Environmental Statement.

2.2.3 A map of the boreholes is provided in Appendix H of the 2014 report. There are: five boreholes on Roger Dudman Way BH07, BH08, BH09, BH10 and BH11; two boreholes and two window samples south of the Botley Road Bridge BH01, BH06, WS01 and WS02; and four Window samples and two boreholes east of the station outside the current main station building, WS14, WS03, WS05, WS06, BH03 and BH04a. Boreholes from investigations prior to the 2014 investigation are also included in Appendix H of the 2014 Phase 1 and Phase 2 report.

2.2.4 Laboratory testing sheets are provided by i2. It is noted that asbestos was detected and some levels of Total Petroleum Hydrocarbons (TPH) are elevated, especially in BH12. Soil and groundwater samples were tested for a limited number of determinands (metals, TPH, asbestos, volatile organic carbons, cyanides, and benzene toluene ethylbenzene xylenes for groundwater only).

2.2.5 Geological cross sections are provided in Appendix K of the 2014 Phase 1 and Phase 2 report.

2.2.6 Ground gas data provided suggest an average ground gas flow across all boreholes of 1l/hr. Elevated CO2 was detected in BH01 and BH05A. This is assessed in the “Down Sidings Contaminated Land Study Report”.

2.2.7 During the ground investigation visual and olfactory signs of contamination were recorded. Noted below are the observations of contamination recorded within the red line boundary:

• BH01 – Strong hydrocarbon odour within the made ground, specifically an old railway sleeper from 2.40m to 2.60m below ground level (bgl) (Botley Road Bridge);

• BH12 (just north of the Sheepwash Bridge outside the Scheme) – Strong hydrocarbon odour throughout the fine grained made ground between Page 3 of 26 OFFICIAL

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01

1.20m and 3.50m bgl. Free product was recorded above the water table during the excavation of this borehole (Down Carriage Sidings and Sheepwash Bridge);

• WS03 – Strong hydrocarbon odour throughout the fine grained made ground between 0.58m and 0.63m bgl (close to new subway proposed);

• WS05 – Strong hydrocarbon odour throughout the fine grained made ground between 0.60m and 0.88m bgl (close to new subway proposed); and

• WS15a (just north of the Sheepwash Bridge outside the Scheme) – Strong hydrocarbon odour throughout both the coarse and fine grained made ground between 1.00m and 5.00m bgl. (Down Carriage Sidings).

2.2.8 The report states that made ground varies across the site, which includes the current red line boundary, with both fine and coarse material present. Around Botley Road Bridge, the made ground maximum thickness was 4.2m. It was noted that the thickness of the made ground was related to the height of the railway embankment. The borehole logs suggest the made ground grades downward into the alluvium.

2.2.9 Alluvium was observed across the site, which includes within the red line boundary, as a very soft to firm silty, sandy, slightly gravelly clay. Pockets and thin horizons of peat were observed but according to the report, these are not considered widespread or of significant thickness. The thickness of the alluvium varied along the site and is observed as being locally absent. It is suggested that the thickness of the alluvium is influenced by the thickness of the made ground as a result of material excavation as part of the placement of the made ground. Therefore, there are large variations even locally.

2.2.10 River Terrace Deposits were encountered across the majority of the site, including within the current red line boundary. However, a number of boreholes could not be completed prior to encountering the River Terrace Deposits and their presence can only be inferred based on the dynamic probe results obtained through the base of the borehole. The proven thickness of this layer varies greatly, with thicknesses ranging from 0.97m to 5.5m. The report states that this variation in thickness is typical for a linear site which follows a meandering river valley. The Scheme would intercept differing parts of the river meander and therefore cross different deposition evolution environments of the river valley.

2.2.11 The Oxford Clay was recorded in all cable percussion boreholes taken to depth. It was proven to underlie the River Terrace Deposits and has a proven thickness of at least 12.5m.

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 Groundwater strikes were recorded in the majority of the exploratory holes during the ground investigation. Where encountered, the groundwater was recorded around the base of the alluvium and in the upper part of the River Terrace Deposits. Groundwater strikes are presented in Table A2.2.

Table A2.2: Groundwater strikes

Area of site Groundwater strikes (m. bgl) Borehole 4.5 BH01 16 Botley Road widening and rail bridge 18 replacement 3.7 BH06 13.1 4.50 BH07 16.0 5.20 BH08 Western entrance to the station 4.90 BH09 4.0 BH10 5.0 BH11 11.0 4.50 BH07 New Platform 5 and subway 16.0 Sheepwash Bridge replacement. 3.50 BH12

2.2.12 The 2014 Oxford Corridor Capacity Improvement Phase 1 and Phase 2 Ground Investigation Report recommends further investigation of the Botley Road as the ground and groundwater conditions were not fully understood at this location. It also recommends further water quality sampling to delineate existing groundwater contamination.

2.2.13 The 2014 Oxford Corridor Capacity Improvement Phase 1 and Phase 2 Ground Investigation Report also includes information from four historical ground investigations. These are:

• MLM Consulting Freight Train Lengthening Project in 2012;

• THJV Ground investigation in 2012;

• Bridgeway Consulting Limited Ground Investigation in 2013; and

• Global Rail Construction Limited Oxford Re-signalling Ground Investigation in 2014;

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 2.2.14 In 2012, MLM carried out twenty-three window sample boreholes up to 2.60m in depth. Track bed trial pits were also carried out, but trial pit logs were not included in any of the factual reports. The MLM ground investigation is provided in Appendix F of the Phase 1 & 2 Ground Investigation Report. Plans of boreholes and trial pits along the tracks are provided but only window sample borehole logs were available to review. Boreholes and trial pits span a large distance from Oxford Station north along the railway past Godstow Lock. The trial pits were within the study area at Sheepwash Bridge and outside the front of the station, but the trial pit logs were not available for review. Only window sample WS1 in the Down Sidings area is relevant to the current Scheme, just north of the red line boundary. This window sample borehole encountered mainly alluvium.

2.2.15 In 2012, THJV carried out three window sample boreholes to the north of Sheepwash Bridge to the east of the tracks, including geotechnical and geoenvironmental laboratory testing. Information from this investigation is provided in Appendix G of the Phase 1 & 2 Ground Investigation Report. Maps are provided in the main Phase 1 & 2 Ground Investigation Report. The boreholes are not within the red line boundary. Limited geo-environmental testing is provided with only two soil samples from the made ground analysed for a suite of metals and TPH. Borehole logs provide depths of strata, water strikes and any visual or olfactory contamination. None of the boreholes record visual or olfactory contamination. Made ground included brick, clay pipe, and decomposing wood.

2.2.16 In 2013, Bridgeway Consulting carried out five dynamic sample boreholes drilled to a maximum of 12.06m and eight window sample boreholes. The ground investigation was carried out as part of the freight train lengthening scheme. These boreholes are north of Walton Well Road, outside the study area. Chemical results are only for Building Research Establishment (BRE) special digest 1 (BRE 2005) testing. Information from this investigation is provided in Appendix E of the Phase 1 & 2 Ground Investigation Report.

2.2.17 In 2014 Global Rail Construction Limited undertook a ground investigation named Oxford Re-signalling. The boreholes from the investigation focussed around the Botley Road Bridge including BHOD2368 Cantilever, WSOD2368+2366 and DPM OD2368. Information from this investigation is provided in Appendix D of the Phase 1 &2 Ground Investigation Report. No geo-environmental data are available. Borehole logs available show made ground and water strikes. Made ground was variable across the two positions.

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 2.3 Contaminated Land Risk Assessment October 2014

2.3.1 In parallel with the Phase 1 & 2 Ground Investigation Report, THJV produced a generic quantitative risk assessment risk assessment (THJV 2014b). The 2014 THJV report includes a preliminary contaminated land risk assessment to inform future works to be undertaken at the Oxford Corridor, a soil and controlled water risk assessment as a generic quantitative risk assessment and a ground gas assessment. The report identifies source-pathway-receptor linkages based on a conceptual site model produced from a desktop assessment. It includes known ground investigation data of the site and associates a risk level to each potential contamination source.

2.3.2 The report splits the site into zones of potential contamination. This is followed through to the conceptual model. Only zone 2 and zone 3 represent the geology and soils in the current study area. The THJV conceptual model is comprehensive and includes contamination sources during construction and operation. The majority of risks are classified as Moderate/Low to High based on the qualitative risk assessment Research & Development publication 2008. A revised conceptual model is provided at the end of the report after key risks and mitigation are considered. The risks are reduced although there are still some risks categorised as “very high”.

2.3.3 The following key contamination risk areas have been identified from the contamination assessment in the report:

2.3.4 BH00, located south of the current red line boundary, close to the Osney Lane footbridge. This area has elevated levels of hydrocarbon contamination associated with the former sidings in the area, where Becket Street station car park is now located. According to the 2014 risk assessment report, the extent of this contamination is unknown and should be delineated to identify if the groundwater contamination plume may have effect on the works at Botley Road Bridge.

2.3.5 BH12/WS15a, located in the Down Carriage Sidings. This area also has elevated levels of hydrocarbon contamination, noted as free product during the ground investigation and subsequent monitoring visits. The source of contamination has been identified as fuel tanks. According to the 2014 risk assessment report, the extent of contamination in this area is unknown and a further assessment should be completed as part of the works whilst the area is accessible.

2.3.6 Botley Road Bridge. Contamination levels directly beneath the bridge are unknown. As a dewatering scheme is proposed at this area, a detailed

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 groundwater study is required to assess the groundwater regime beneath the site.

2.3.7 Asbestos has been identified in isolated areas but is not considered to be pervasive.

2.3.8 Ground gas has been identified as a significant risk. Any buildings designed within the Oxford Station would be provided with gas protection measures.

2.3.9 The majority of the soils have been given an indicative hazardous waste classification of non-hazardous. However, isolated contamination hotspots have been identified as having a hazardous, or potentially hazardous, waste classification. These included BH12, WS15A, BH01, BH04 and BH00, sample depths of hazardous waste were not provided within the report.

2.4 Geo-environmental Summary Memorandum, 2014

2.4.1 On 21st October 2014 THJV issued a geo-environmental summary memorandum (THJV, 2014c). This states the key contamination issues arising following the targeted ground investigation undertaken throughout the Oxford Corridor site. Key contamination areas identified are the Down Sidings and the Osney Lane footbridge.

2.4.2 In the Down Carriage Sidings area, soil has been found to be heavily contaminated by hydrocarbons. Visual petroleum contamination and a strong hydrocarbon odour were encountered during the 2014 ground investigation and up to 1.4m of free product was recorded above the water table. The likely source of contamination is the old storage tanks located within the Down Carriage Sidings. The full extent of contamination in the area was not proven and would require delineation by a targeted ground investigation.

2.4.3 Isolated contamination was found in the Osney Lane footbridge at BH00. According to the memorandum, the made ground and the groundwater were identified to be significantly contaminated by hydrocarbons. The extent of the contamination in this area is unknown. Historical sidings and goods sheds are recorded on historical maps for this area.

2.4.4 Other contamination issues have been reported including asbestos detection, hazardous materials (for waste disposal purposes) and elevated levels of ground gas.

2.4.5 Roger Dudman Way Factual Ground Investigation Report, 2017

2.4.6 This report presents the factual information of the ground investigation completed within Roger Dudman Way on land owned by The University of Oxford. As part of the ongoing investigation of the Network Rail Down Sidings Page 8 of 26 OFFICIAL

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 area, the requirement to undertake sampling outside of the Network Rail boundary along Roger Dudman Way was identified.

2.4.7 The ground investigation works along Roger Dudman Way were carried out between 22nd and 23rd February 2017. Three monitoring visits for obtaining groundwater samples from monitoring installations were included. Two window sample boreholes (WS1B and WS2) were excavated as part of this ground investigation. Details are summarised in Table A2.3

Table A2.3: Summary of boreholes from Roger Dudman Way investigation

Exploratory Ground Installation Comment Level response zone Hole I.D. (mAOD) WS1B 58.0 0.5 – 1.5m.bgl Located between Sheepwash Channel and the Down Sidings. WS1 and WS1A encountered services and were abandoned. WS2 58.0 0.5 – 1.5m.bgl Located between the surface water course and 3.20 – 3.70m.bgl the Down Sidings. Has two installations.

2.4.8 Chemical tests were carried out on selected soil and groundwater samples. The testing was targeted at hydrocarbon contamination (TPH-CWG and Banded TPH) and polyaromatic hydrocarbon contamination (Speciated PAH- USEPA16). The metal suite was also analysed.

2.4.9 The made ground within the Roger Dudman Way was in the region of 1.4m to 1.5m thick. It comprised coarse grained made ground (top 1.0m) of mixed sand and gravel comprising brick, slag, clinker, ash, and concrete underline by fine grained material. The fine grained made ground was encountered beneath the coarse-grained layer across the Down Sidings area, comprising soft to firm, locally stiff, silty clay with varying sand and gravel content. It is possible that this material is a combination of reworked alluvium and Oxford Clay.

2.4.10 Groundwater was monitored on four occasions showing groundwater encountered within the borehole response zone three times out of four in WS01B; WS2 was found to be dry at all times within the made ground response zone and groundwater was found with the river deposits response zone.

2.4.11 The report does not include discussion of the chemical results.

2.5 Oxford Corridor, Down Sidings Contaminated Land Study Report, April 2018

2.5.1 The scope of work is concerned with the delineation of soil, free phase and groundwater contamination at the Down Sidings. Page 9 of 26 OFFICIAL

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 2.5.2 The following activities were undertaken:

• a contaminated land ground investigation to delineate the extent of the hydrocarbon contamination identified from the initial ground investigation; and

• a Detailed Quantitative Risk Assessment (DQRA) for the Down Sidings.

2.5.3 The report includes a review and a summary of previous desk study and ground investigation completed at the Down Sidings. Historical contaminative sources were identified within the Down Sidings (railway maintenance and engineering sheds and later the presence of four above ground storage tanks). During an early ground investigation, significant hydrocarbon contamination was identified around the location of the above ground storage tanks, including the accumulation of free product within a monitoring well. The sensitivity of the underlying groundwater aquifer (River Terrace Deposits) and the close proximity of surface watercourses (Fiddlers Island Stream and River Thames) identified the Down Sidings as a potential significant contamination risk.

2.5.4 To address the contamination concern, THJV developed a contamination delineation study within the Down Sidings, which gained Environment Agency approval. Ground investigation works were carried out between 8th February 2016 and 17th February 2016. The investigation comprised thirteen trial pits to understand near surface contamination within the made ground; nine boreholes to allow monitoring of made ground and perched ground contamination; and five boreholes in the underlying River Terrace Deposits to review contamination within the main aquifer body. Exploratory holes were positioned to provide information at the source, as well as up gradient and down gradient.

2.5.5 Visual and olfactory signs of chemical contamination were recorded during the ground investigation as a vitreous black sheen, with a strong hydrocarbon and petrol odour recorded in DSTP01, DSTP02, DSTP3 and DSTP8. A strong hydrocarbon odour (heavy end) was noted, and free phase black oil was seen on the surface of the water as specks and mini plumes in DSTP10.

2.5.6 Site observations identified contamination within a coarse-grained horizon of made ground at approximately 1.2m to 2.5m below ground level. Contamination was mainly in the area around the suspected source, but also extended to the surrounding area. The presence of alluvium and minimal made ground within Roger Dudman Way appears to have restricted horizontal migration westwards to the river Thames, confining the made ground contamination within the proximity of the Network Rail boundary.

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 2.5.7 Perched groundwater encountered, contained visible free product. Beneath this coarse layer, the made ground was more cohesive. A reduction in contamination was observed within this cohesive made ground, and within the River Terrace Deposits beneath. This is supported by chemical laboratory data which confirmed significant hydrocarbon and PAH contamination within this area, with reduced concentrations recorded away from the source area and with depth within the aquifer. Groundwater contamination has been recorded within the aquifer.

2.5.8 Based on the ground investigation information and the subsequent human health and controlled waters risk assessment, the following key contamination concerns have been identified:

2.5.9 Soil contamination is not considered to pose an unacceptable risk to human health and no further action is required except in one location. This is the above ground storage tanks in the sidings which has been identified as having an unacceptable risk to both human health and controlled waters if left unmitigated.

2.5.10 PAH within the soil and TPH (aromatic range C10-C16) within the River Terrace Deposits groundwater (based on a Tier 1 and Tier 2 risk assessment) is considered to pose an unacceptable risk to controlled water and remedial action is required.

2.5.11 The fine-grained alluvium and made ground provide a horizontal and vertical barrier to contamination migration, restricting the contamination to within the footprint of the Down Sidings. Localised buried structures associated with the historical development are identified as potentially providing sinks within the made ground, concentrating the free product to a localised area.

2.5.12 Geochemical tests were carried out on selected soil and groundwater samples.

2.5.13 The groundwater local to the Down Sidings appears to flow in a northeast to southwest and north northeast to south southwest direction towards the local surface water courses.

2.5.14 Based on the information obtained as part of the ground investigation, a Stage 1 Generic Quantitative Human Health Risk Assessment was completed for the hydrocarbon and PAH contamination. According to the report the laboratory testing results were all below respective generic screening criteria and therefore the soil is considered not to pose a risk to human health and no further action is required.

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 2.5.15 In addition, a Stage 1 Generic Quantitative Controlled Waters Risk Assessment was completed for the hydrocarbon and PAH contamination. According to the report this assessment identified failures against the respective generic screening criteria and therefore a further Stage 2 DQRA for Controlled Waters was required.

2.5.16 The Stage 2 DQRA identified failures to the site-specific screening criteria for PAH within the soil and for TPH Aromatic splits C10-C16 within the River Terrace Deposits groundwater. Therefore, the hydrocarbon and PAH contamination at the site is considered to pose a risk to controlled waters and remedial action is required.

2.5.17 The groundwater quality testing at Roger Dudman Way shows a significant reduction in the concentration of hydrocarbons between the surface water course and the source area. Groundwater quality reduction was identified however.

2.6 Oxford Corridor, Phase 2, Detailed Design Environment Management Plan, GRIP Stage 5

2.6.1 Network Rail commissioned THJV to undertake a GRIP 5 study into the Oxford Corridor CP5 works.

2.6.2 The report includes a contaminated land section which identified the following contaminated land risks to the project:

• Excavations and installation of piles and other building foundations is likely to create a pathway for historical contamination associated with the railway corridor, infrastructure, and ground gas from neighbouring landfill sites; • Stockpiling of excavated contaminated materials may create new sources of contamination, or move existing contamination to new destinations within the site confines; • Asbestos originating from buildings or contained within ballast may be present. Asbestos has previous uses as brake linings in trains and is likely to be found in made ground; • Network Rail’s Hazard Directory noted asbestos at two localities; • There are 11 historic landfills within 250m of the project boundary; and • Heavy hydrocarbon contamination was discovered at the Down Sidings during THJV site investigation works. This is detailed in THJV ground investigation report (W1002B-TTS-REP-EGE-007002). 2.6.3 The report also discusses the need for a materials management plan and the potential for asbestos to be included in the environmental management plan for the site. Page 12 of 26 OFFICIAL

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 3. CONCEPTUAL MODEL

3.1 Legislative Background and Assessment of Risk

3.1.1 There are two broad regimes for addressing existing land contamination within the UK: Part 2A of the Environmental Protection Act (EPA) 1990; and accompanying statutory guidance (Department for Environment, Food and Rural Affairs, 2012). These deal with determination of land as ‘contaminated land,’ and the planning regime, which embraces a “suitable for use” approach to land development.

3.1.2 The contamination assessment in this report is based on government online guidance on Land Contamination: Risk Management published by the Environment Agency in 2020. An important thread throughout the overall process of risk assessment is the need to formulate and develop a Conceptual Model for the site, which supports the identification and assessment of contaminant linkages. Development of the Conceptual Model forms the main part of preliminary risk assessment, and the model is subsequently refined or revised as more information and understanding is obtained through the risk assessment process.

3.1.3 A risk assessment has been undertaken for the Scheme within the current red line boundary to identify the main potential contaminant linkages based upon a review of the site history, ground conditions and environmental setting. The method for risk evaluation has been based on guidance by CIRIA (2001) ‘C552: Contaminated Land Risk Assessment - A Guide to Good Practice’, which is a qualitative method of interpreting the risks based on the magnitudes of both the potential consequence (severity) and the probability (likelihood) of the risk occurring.

3.1.4 The risk matrix in tables A3.1 to A3.4 below has been used to estimate a score for each potential land contamination risk identified.

Table A3.1: Classification of consequence (based on CIRIA, 2001)

Classification Human Health Controlled Waters Buildings / Services Severe Short term (acute) risk Substantial pollution of Catastrophic damage. to human health. water resources is Concentrations present being caused such that likely to result in ‘significant pollution’ or ’significant harm’ as ‘significant possibility of defined by Part 2A of pollution’ of controlled the EPA. waters as defined by Part 2A of the EPA. Medium Chronic damage to Pollution of water Significant damage to human health. resources such that buildings, structures or Concentrations present there is a measurable the environment Page 13 of 26 OFFICIAL

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Classification Human Health Controlled Waters Buildings / Services that could result in (but not significant) making it unsafe to significant harm. reduction in water occupy, or damage resources compared to that may impair a the water quality Scheduled Monument. standard. Mild Slight short-term health Measurable reduction Minor damage to effects to humans. in water quality sensitive buildings, Exposure to human compared to baseline. structures, services, or health unlikely to lead the environment. to significant harm. Minor Non-permanent health Insubstantial pollution Easily repairable. effects to humans to water resources (easily prevented by compared to baseline. means such as personal protective clothing, etc.) Note the use of the term ‘significant’ in this table is in accordance with Land Contamination Risk Management and Part 2A statutory guidance on land contamination. Table A3.2: Estimation of likelihood

Classification Definition High Likelihood There is a pollution linkage and an event that either appears very likely in the short term and almost inevitable over the long term, or there is evidence at the receptor of harm or pollution. Likely There is a pollutant linkage and all the elements are present and in the right place, which means that it is probable that an event will occur. Circumstances are such that an event is not inevitable, but possible in the short term and likely over the long term. Low Likelihood There is a pollution linkage and circumstances are possible under which an event could occur. However, it is by no means certain that even over a longer period that such an event would take place and is even less likely in the shorter term. Unlikely There is a pollution linkage, but circumstances are such that it is improbable that an event would occur even in the very long term.

Table A3.3: Risk matrix – Risk ratings

Risk Matrix Consequence (Severity) Severe Medium Mild Minor

High Likelihood Very High High Moderate Moderate/Low

Likely High Moderate Moderate/low Low

Low Likelihood Moderate Moderate/Low Low Very Low (likelihood) Probability Probability Unlikely Moderate/Low Low Very Low Very Low

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Table A3.4: Risk descriptions

Risk Risk Description Very High There is a high likelihood of the event occurring and having severe consequences. If the risk is realised it is likely to result in a substantial liability. High Likely that an event with medium or even severe consequences could arise. If the risk is realised it may result in a substantial liability. Moderate It is possible that an event could occur, and it is either unlikely and consequences may be severe or if it were to occur it is likely that consequences would be relatively mild. Investigation would normally be required to clarify the risk and determine the potential liability. Low It is possible that an event could occur, but it is likely that the consequences would be at worst mild. Very Low It is unlikely that an event could occur, and if it happened the consequences are likely to be at worst mild.

3.2 Conceptual Model

Potential Sources

3.2.1 Table A3.5 lays out the potential sources of pollution within the Conceptual Model.

Table A3.5: Potential sources of contamination

Sources Potential Contaminants Within the red line boundary Made ground. Made ground of unknown composition can contain contaminants such us metals, asbestos and petroleum hydrocarbons. Asbestos was found in at least one sample of made ground and has various potential sources across the site from historical structures, insulation from trains, old brake pads. Fuels, and oil leaks may have occurred from trains along the railway line. Lubricants used on moving parts, ballast, coal, clinker, and slag have potential to contaminate made ground. Hydrocarbon contamination at Osney High hydrocarbon concentration found in one groundwater Lane footbridge. sample in BH00. Historical land uses including sidings Potential soil and groundwater contamination including and depots at Roger Dudman Way car petroleum hydrocarbons, metals and asbestos and ground park. gas may be present in this area. Outside red line boundary Soil and groundwater contamination Historical fuel tanks present on site from 1969 – 2003 from former Diesel tanks within Down have been proven as a point source of contamination from Carriage Sidings. previous ground investigations. Soil and groundwater hydrocarbon contamination has been recorded within this area.

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Sources Potential Contaminants Three historical landfills. Ground gas and landfill leachate in groundwater. Former industrial land use – Tallow Potential release of contaminants associated with the Factory, Eagle Foundry (Iron and historical land use can include metals, petroleum Brass), Ink Works. hydrocarbons, chlorinated solvents, and asbestos. Migration or run off of contaminants from past industrial land use may have impacted the soil and groundwater within the study area.

Potential Pathways

3.2.2 Table A3.6 lays out the potential pollution pathways within the CSM.

Table A3.6: Potential pathways

Pathways Description Inhalation, ingestion, Dermal contact Potential pathway to maintenance workers (breaking ground) and offsite humans. Leaching and infiltration Potential pathways to the Secondary A aquifer, vegetation, surface water drainage to the River Thames, Sheepwash Channel and Castle Mill Stream and Oxford Canal. Surface runoff Potential pathways to vegetation, surface water drainage and the River Thames, Sheepwash Channel, Castle Mill Stream and Oxford Canal. Gas migration through permeable Potential pathway to Maintenance workers (breaking strata ground) and infrastructure.

Potential Receptors

3.2.3 The following is a list of potential pollution receptors within the Conceptual Model:

• maintenance workers (breaking ground);

• offsite humans;

• surface water – River Thames, Sheepwash Channel, Castle Mill Stream, Oxford Canal;

• groundwater – Secondary A aquifer; and

• infrastructure.

3.3 Preliminary Risk Assessment

3.3.1 The preliminary risk assessment associated with the potential sources of contamination is split in to four areas:

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• Sheepwash Bridge replacement;

• Roger Dudman Way, and the western entrance;

• Platform 5 and subway; and

• Botley Road Bridge widening.

3.3.2 These areas are summarised in Tables A3.7 to 3.11. It should be noted that realisation of the potential risks identified is dependent on the contamination source being present. Some of the historical potential sources of contamination have been confirmed by previous ground investigation.

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 Table A3.7: Conceptual model and risk assessment - Sheepwash Bridge replacement

Source Pathway Receptor Explanation / possible mitigation Likelihood (with Consequence Risk (with mitigation) mitigation)

Made ground is likely to be Dermal contact, Workers (breaking Made ground contaminated from historical railway works. Mitigation would include Low Medium Moderate/Low present. Fuel, hydrocarbons, ingestion and inhalation ground) the use of correct PPE and watching brief. and oil leaks from trains. During construction dust may be produced which could migrate to offsite humans. Lubricants used on moving Dermal contact, Offsite humans This would be mitigated by adopting working practices to reduce dust generation at Unlikely Medium Low parts, ballast, coal, clinker, and ingestion and inhalation slag have potential to have the site. contaminated the made ground. Made ground, if contaminated, can leach contaminants into the below aquifer. Excavation undertaken during the works could create new pathways for the Groundwater – Leaching and infiltration contaminants to move vertically and laterally into the aquifer. Mitigation could Low Mild Low Asbestos may be within the Secondary A aquifer made ground. A signal box was include groundwater control, protecting excavations from surface water infiltration located just north of Sheepwash and removal of contaminated soils encountered during excavations. Bridge in 1878. This was likely Surface water – River The bridge is in a flood risk area. Due to flood protection measures however, there to have included asbestos. Thames, Sheepwash is a low likelihood of surface water flooding followed by surface run off. Surface runoff Low Mild Low Channel and Castle Contaminated materials would be stored out of flood risk area and away from Mill Stream surface water drains and surface water drains would be protected. Infrastructure could be impacted by ground gas generated by contaminants in the made ground. Gas migration through Infrastructure Low Mild Low permeable strata BH12 north of Sheepwash Bridge was classified as having a characteristic situation 2 due to its high carbon dioxide and flow. Mitigation would include gas venting or measures within the detailed design. Soil and groundwater Historical ground investigation confirmed that soil and groundwater are contamination by diesel spills at contaminated by fuels/hydrocarbons. According to the historical reports the fine location outside the red line grained alluvium and made ground provides a horizontal and vertical barrier to boundary. contamination migration, restricting the contamination to within the footprint of the Down Sidings only. However, groundwater flow direction identified in the historic Dermal contact, Maintenance workers ground investigation is toward the Castle Mill stream and Sheepwash Channel, Low Medium Moderate/Low Historical tanks located at the ingestion and inhalation (breaking ground) therefore in the direction of the Sheepwash Bridge area. Excavations undertaken Down Carriage Sidings have during the works could create new pathways for the contaminants to move towards been identified as a point source the Sheepwash Bridge. It is likely that workers may come into contact with this of contamination of diesel from contamination while breaking the ground. Mitigation would include the use of previous ground investigations. correct PPE and watching brief. The tanks have now been The majority of this contamination is underground within the groundwater and not removed but the concrete bunds Dermal contact, Offsite humans prone to being spread by dust. Therefore, it is unlikely offsite humans would come Unlikely Mild Very Low and underground pipes are still ingestion and inhalation present. The concrete bunds are in to contact with this contamination. infilled with soil. The Down Carriage Sidings ground investigation report confirmed groundwater is contaminated by historical diesel leaching tanks. According to the historical reports According to the Environment the fine-grained alluvium and made ground provides a horizontal and vertical barrier Agency a diesel spillage was to contamination migration, restricting the contamination to within the footprint of also recorded in the Walton the Down Carriage Sidings only. However, groundwater flow direction identified in Groundwater – Road Allotments during the Leaching and infiltration the historical ground investigation is toward the Castle Mill stream and Sheepwash Low Mild Low Secondary A aquifer development of Castle Mill Channel, therefore in the direction of the Sheepwash Bridge area. Excavations student accommodation. undertaken during the works could create new pathways for the contaminants. Mitigation would include dewatering procedures used during construction if Former tank recorded at the old groundwater is encountered, protecting excavations from surface water infiltration. engine shed (map 1878) Also, removal of contaminated soils encountered during excavations Rainfall could cause run off of exposed contaminants into the Sheepwash Surface runoff Surface water – River Low Mild Low Thames, Sheepwash Channel which could flow into the Castle Mill Stream and the River Thames.

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Groundwater – Contaminated groundwater would be removed from site and not discharged into The Walton Well Road Landfill Leaching and infiltration Low Mild Low Secondary A aquifer any rivers, streams or groundwater. Good practice by site workers would reduce lies 300m north west of the site. the likelihood of further contaminating groundwater such as wearing of appropriate PPE. See Appendix 7.1 (Volume 4 of the ES) for further information Ground gas from the landfill could impact infrastructure if not vented correctly. Gas migration through on landfills close to the site. Infrastructure Ground gas monitoring was undertaken at Rewley and Walton Well Road landfills Low Mild Low permeable strata and no significant flammable gases were found

Table A3.8: Conceptual model and risk assessment - Roger Dudman Way, western entrance, Platform 5

Source Pathway Receptor Explanation / possible mitigation Likelihood Consequence Risk (with mitigation) (with mitigation) Made ground (within red line Considerable made ground was found when breaking ground. Chemical boundary) Maintenance analyses on the made ground were not completed therefore presence of Dermal contact, ingestion, workers (breaking contamination is not proven. Low Medium Moderate/Low and inhalation Ground Investigation along ground) A watching brief is recommended during the exactions and appropriate PPE Roger Dudman Road showed should be worn. considerable made ground Considerable made ground was found when breaking ground. Chemical including ballast and clinker. analyses on the made ground were not completed therefore presence of Dermal contact, ingestion, contamination is not proven. Offsite humans Low Mild Low Asbestos is likely to be within and inhalation During construction dust may be produced which could contact offsite the made ground due to humans. This would be mitigated by adopting good working practices general usage on site including reducing dust generation (e.g. dust management plan). use in brake linings in trains. Made ground, if contaminated, can leach contaminants into the below Asbestos was not tested for aquifer. Excavation undertaken during the works can create new pathways during the Roger Dudman way for the contaminants to move vertically and laterally into the aquifer. investigation. Groundwater – WS2 was found to have elevated concentrations of hydrocarbons in the Leaching and infiltration Low Mild Low Secondary A aquifer groundwater. Whilst in construction, new pathways may be created which could increase the likelihood of further spreading of contamination within the groundwater. Mitigation would include groundwater control, protecting excavations from surface water infiltration, removal of contaminated soils encountered during excavations. Surface water – Rainfall could cause run off from exposed contaminated made ground into Surface runoff River Thames, the nearby water courses. Oxford Station is in a flood area, however due to Low Mild Low Sheepwash flood protection measures there is a low likelihood of surface water flooding

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 Source Pathway Receptor Explanation / possible mitigation Likelihood Consequence Risk (with mitigation) (with mitigation) Channel and Castle followed by surface run off. Contaminated materials would be stored out of Mill Stream flood risk area and away from surface water drains and surface water drains would be protected. Infrastructure could be impacted by ground gas from contaminants in the Gas migration through Infrastructure made ground. Gas monitoring or venting may be required during detailed Low Medium Moderate/Low permeable strata design. Historical landfills (outside red Workers would not be digging into off-site landfills but would be made aware line boundary) of potential contaminated groundwater and gas whilst breaking ground. The Walton Well Road Landfill Appropriate PPE would be worn whilst breaking ground. Maintenance lies 300m north west of the Dermal contact, ingestion, workers (breaking Low Medium Moderate/Low site. and inhalation ground) See Appendix 7.1 (Volume 4 of the ES) for further information on landfills close to the site. Contamination from the landfill is unlikely to be creating dust. Any contaminated groundwater which requires removal, would be removed from Dermal contact, ingestion, Offsite humans site and not discharged into any rivers, streams or groundwater. Good Unlikely Mild Very Low and inhalation practice by site workers would reduce the likelihood of contact with offsite humans.

Groundwater may be impacted by the landfill before it flows through the area of Roger Dudman Way. Groundwater – Contaminated groundwater which requires removal would be removed from Leaching and infiltration Secondary A site and not discharged into any rivers, streams or groundwater. Mitigation Low Mild Low aquifer could include groundwater control, protecting excavations from surface water infiltration, removal of contaminated soils encountered during excavations.

Surface water – Contaminated groundwater which requires removal would be removed from River Thames, site and not discharged into any rivers, streams or groundwater. Surface runoff Sheepwash Contaminated materials would be stored out of flood risk area and away Low Mild Low Channel and Castle from surface water drains and surface water drains protected. Mill Stream

Gas migration through Ground gas from the landfill could impact infrastructure if not vented Infrastructure Low Medium Moderate/Low permeable strata correctly.

Table A3.9: Conceptual model and risk assessment - Platform 5 and subway

Source Pathway Receptor Explanation / possible mitigation Likelihood (with Consequence Risk (with mitigation) mitigation)

Dermal contact, ingestion Maintenance workers (breaking Considerable made ground was found., a watching brief Made ground Low Medium Moderate/Low and inhalation ground) and appropriate PPE would be worn. Ground Investigation along the During construction dust may be produced which could front of the station have Dermal contact, ingestion contact offsite humans. This could be mitigated by good Offsite humans Unlikely Medium Low variable made ground and inhalation working practices reducing dust from the site eg by including ash, bricks, ballast production of a Dust Management Plan.

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 Source Pathway Receptor Explanation / possible mitigation Likelihood (with Consequence Risk (with mitigation) mitigation) and clinker. Some borehole Whilst in construction new pathways may be created which logs mention a strong odour of could increase the likelihood of further spreading of hydrocarbons within the made Groundwater – Secondary A contamination within the groundwater. Groundwater Leaching and infiltration Low Mild Low ground. aquifer control, protecting excavations from surface water infiltration, removal of contaminated soils encountered On historical maps the area during excavations would all be used where necessary. was part of a coal depot from The station is in a flood area, however due to flood 1876 – 1957. protection measures there is a low likelihood of surface Surface water – River Thames, water flooding followed by surface run off. Contaminated Surface Runoff Sheepwash Channel and Castle Low Mild Low materials would be stored out of flood risk area and away Asbestos is likely to be within Mill Stream the made ground due to from surface water drains and surface water drains would general usage on site be protected. including use in brake linings in trains. Infrastructure could be impacted by ground gas from Gas migration through Asbestos was not detected in Infrastructure contaminants in the made ground. gas monitoring or Low Medium Moderate/Low permeable strata any of the six boreholes venting may be required during detailed design. around the front of the station.

Table A3.10: Conceptual model and risk assessment - Botley Road Bridge widening

Source Pathway Receptor Explanation / possible mitigation Likelihood (with Consequence Risk (with mitigation) mitigation)

Made ground Dermal contact, ingestion Maintenance workers (breaking Considerable made ground was found. Watching brief and Low Medium Moderate/Low and inhalation ground) appropriate PPE should be worn as necessary. Ground Investigations along During construction dust may be produced which could Dermal contact, ingestion the front of the station have Offsite humans contact offsite humans. This could be mitigated by good Unlikely Medium Low and inhalation variable made ground working practices reducing dust from the site. including ash, bricks, ballast and clinker. Some borehole Whilst in construction new pathways may be created logs mention a strong odour of which could increase the likelihood of further spreading of Groundwater – Secondary A contamination within the groundwater. Groundwater hydrocarbons within the made Leaching and Infiltration Low Mild Low ground. aquifer control, protecting excavations from surface water infiltration and removal of contaminated soils encountered during excavations. Asbestos is likely to be within the made ground due to The station is in a flood risk area, however due to flood protection measures there is a low likelihood of surface general usage on site including Surface water – River Thames, water flooding followed by surface run off. Contaminated use in brake linings in trains. Surface Runoff Sheepwash Channel and Castle Low Mild Low materials would be stored out of flood risk area and away Asbestos was not detected in Mill Stream any of the six boreholes from surface water drains and surface water drains would around the front of the station. be protected. Gas migration through Infrastructure could be impacted by ground gas from Infrastructure Low Medium Moderate/Low permeable strata contaminants in the made ground. Historical Contamination Workers breaking ground should be made aware of Dermal contact, ingestion Maintenance workers (breaking offsite: potential contamination and appropriate PPE should be Low Medium Moderate/Low and inhalation ground) Tank just north of Botley Road worn. Bridge 1956 During construction dust may be produced which could Dermal contact, ingestion Meat Depot just south of Offsite humans contact offsite humans. This could be mitigated by good Unlikely Medium Low and inhalation Botley Road 1969 working practices reducing dust from the site.

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 Source Pathway Receptor Explanation / possible mitigation Likelihood (with Consequence Risk (with mitigation) mitigation) Whilst in construction new pathways may be created No contamination was found which could increase the likelihood of further spreading of from window sample in Groundwater – Secondary A contamination within the groundwater. Contaminated Leaching and Infiltration Low Mild Low location of tank north of Botley aquifer materials would be stored out of flood risk area and away Road. This is an area from surface water drains and surface water drains would expected to be excavated be protected. during the works. Whilst in construction new pathways may be created which could increase the likelihood of further spreading of Surface water – River Thames, contamination within the surface water. Store Surface Runoff Sheepwash Channel and Castle Low Mild Low contaminated materials out of flood risk area and away Mill Stream from surface water drains and protect surface water drains. Gas migration through Infrastructure could be impacted by ground gas from Infrastructure Low Medium Moderate/Low permeable strata contaminants.

Table A3.11: Conceptual model and risk assessment - Becket Street station car park and temporary Co-operative Childcare

Source Pathway Receptor Explanation / possible mitigation Likelihood (with Consequence Risk (with mitigation) mitigation) Made ground Dermal contact, ingestion Maintenance workers (breaking Considerable made ground was found, a watching brief and Low Medium Moderate/Low and inhalation ground) appropriate PPE should be worn. BH01 within the Becket Street During construction dust may be produced which could Dermal contact, ingestion station car park and BH00 to Offsite humans contact offsite humans. This could be mitigated by good Unlikely Medium Low and inhalation the south of the car park, next working practices reducing dust from the site. to the proposed temporary Whilst in construction new pathways may be created which cooperative childcare has Groundwater – Secondary A could increase the likelihood of further spreading of made ground to 4m and Leaching and infiltration Unlikely Medium Low aquifer contamination within the groundwater. Excavation would be hydrocarbon odour was noted shallow and likely not impact groundwater. within the borehole log. The station is in a flood area, however due to flood protection Made ground could include Surface water – River Thames, measures there is a low likelihood of surface water flooding asbestos. Surface runoff Sheepwash Channel and Castle followed by surface run off. Contaminated materials would be Low Mild Low Mill Stream stored out of flood risk area and away from surface water drains and surface water drains would be protected. Infrastructure could be impacted by ground gas from Gas migration through Infrastructure contaminants in the made ground. BH00 had low levels of Low Medium Moderate/ Low permeable strata carbon dioxide and methane. Historical off-site Dermal contact, ingestion Maintenance workers (breaking Workers breaking ground should be made aware of potential Low Medium Moderate/Low contamination. Groundwater and inhalation ground) contamination and appropriate PPE should be worn. from BH00 had hydrocarbon During construction dust may be produced which could contamination. Dermal contact, ingestion Offsite humans contact offsite humans. This could be mitigated by good Unlikely Medium Low and inhalation working practices reducing dust from the site. Whilst in construction new pathways may be created which could increase the likelihood of further spreading of Groundwater – Secondary A contamination within the groundwater. Groundwater control, Leaching and infiltration Low Mild Low aquifer protecting excavations from surface water infiltration and removal of contaminated soils encountered during excavations.

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3.4 Conclusions

3.4.1 Previous ground investigations and accompanying reports suggest contamination across the area of Oxford Station. The Scheme can be split in to four areas, Sheepwash Bridge replacement, Roger Dudman Way, Platform 5 and platform buildings, Botley Road Bridge and Becket Street station car park (including temporary Co-operative Childcare location).

Sheepwash Bridge Replacement

3.4.2 Ground and groundwater contamination are recorded north of Sheepwash Bridge within the Down Carriage Sidings area and Castle Mill. Historical fuel tanks within the Down Carriage Siding and a diesel spill during the Castle Mill development have led to hydrocarbon contamination within the soil and groundwater. According to the local groundwater flow direction, this contamination may have spread within the groundwater towards Sheepwash Bridge.

3.4.3 There is the potential that during the works a new pathway could be created which may mobilise contamination from the Down Carriage Sidings area and Castle Mill groundwater contamination to the Sheepwash Bridge. Ground gas may also be present. However, if mitigation within the risk assessment is adhered to, the risks are considered moderate/Low to Low.

Roger Dudman Way, Western Entrance

3.4.4 Ground investigation showed considerable made ground including ballast and clinker.

3.4.5 There is the potential that during the works, excavation may create pathways which could increase the risk for potential contamination to infiltrate into groundwater and reach the surface waters.

3.4.6 Further ground investigation is recommended before undertaking excavation works, to assess presence and levels of contaminants in soil and groundwater and to refine the risk assessment. However, if mitigation within the risk assessment is adhered to the risks are considered moderate/Low to Low.

Platform 5 and Platform Buildings

3.4.7 Variable made ground including ash, bricks, ballast, and clinker is recorded within these areas. Some borehole logs mention a strong odour of hydrocarbons within the made ground. Peat is also noted on the borehole logs. Chemical analysis of environmental matrix and ground gas monitoring has not been undertaken in these areas.

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 3.4.8 There is the potential that during the works, new pathways could be created for contamination which could increase the risk to groundwater and surface waters.

3.4.9 Ground investigation is recommended before undertaking excavation works to assess the presence and levels of contaminants in soil and groundwater, and to refine the risk assessment. However, if mitigation within the risk assessment is adhered to the risks are considered moderate/Low to Low.

Botley Road Bridge

3.4.10 There are very few boreholes around the Botley Road due to lack of traffic management provision. Made ground is of variable composition and thickness in this area. One borehole further south of Botley Bridge showed visual evidence of hydrocarbons.

3.4.11 There is the potential that during construction, new pathways could be created for contamination which could increase the risk to groundwater and surface waters.

3.4.12 Ground investigation is recommended before undertaking excavation works to establish presence and levels of contaminants in soil and groundwater and to refine the risk assessment. However, if mitigation within the risk assessment is adhered to the risks are considered moderate/Low to Low.

Becket Street Station Car Park (inc. Temporary Co-operative Childcare Relocation)

3.4.13 It is known from ground investigations that the site of the temporary Co- operative Childcare has hydrocarbon contamination. This was associated with low levels of carbon dioxide and methane. Ground gas may also be present. There is the potential that during the works a new pathway could be created which may mobilise this contamination. However, if mitigation within the risk assessment is adhered to the risks are considered moderate/Low to Low.

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Environmental Impact Assessment – Appendix 7.2 Contaminated Land Risk Assessment 163390-JAC-REP-EEN-070002 Revision A01 REFERENCES

Buildings Research Establishment (BRE) (2005). Special Digest 1. CIRIA. (2001). C552: Contaminated Land Risk Assessment - A Guide to Good Practice. Department for Environment, Food and Rural Affairs. (2012). Part 2A of the Environmental Protection Act (EPA) 1990. URL https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/223705/pb137 35cont-land-guidance.pdf. Accessed February 2021 Environment Agency. (2020). Land Contamination Risk Management; How to assess and manage the risks from land contamination. URL https://www.gov.uk/government/publications/land-contamination-risk-management-lcrm. Accessed February 2021 Halcrow – Tata Joint Venture. (2014a). Oxford Corridor Capacity Improvement Phase 1 and Phase 2 Ground investigation Report.

Halcrow – Tata Joint Venture. (2014b). Oxford Corridor Capacity Improvement - Contaminated Land Risk Assessment.

Halcrow – Tata Joint Venture. (2014c). Oxford Corridor Capacity Geo-Environmental Summary Memorandum.

Halcrow – Tata Joint Venture. (2015). Oxford Corridor Material Management Appraisal.

Halcrow – Tata Joint Venture. (2016). Oxford Corridor Ground Investigation ecological watching brief .

Halcrow – Tata Joint Venture. (2017). Oxford Corridor Roger Dudman Way Factual Ground Investigation Report.

Halcrow – Tata Joint Venture. (2018). Oxford Corridor Down Sidings Contaminated Land Study Report.

Halcrow – Tata Joint Venture. (2020). Oxford Corridor Phase 2 Design Environmental Management Plan .

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