Government Pipelines and Storage System (GPSS) Portfolio - Flax … · 2019-06-25 · Government Pipelines and Storage System (GPSS) Portfolio - Flax Bourton PSD LAND QUALITY ASSESSMENT

Government Pipelines and Storage System (GPSS) Portfolio - Flax Bourton PSD

LAND QUALITY ASSESSMENT REPORT

Combined Phase One and Two: LQA

DIO Project Number: 13199

Prepared by SKM Enviros for the Ministry of Defence, Defence Infrastructure Organisation, under commission FTS3/ELMG/100

FINAL

June 2013

DEFENCE INFRASTRUCTURE ORGANISATION

GPSS Portfolio – Flax Bourton PSD LAND QUALITY ASSESSMENT REPORT

Combined Phase One and Two: LQA

DIO Project Number: 13199

Task Officer Defence Infrastructure Organisation Kingston Road Sutton Coldfield West Midlands B75 7RL Tel: 0121 311 3618

Prepared by SKM Enviros for the Ministry of Defence, Defence Infrastructure Organisation, under commission FTS3/ELMG/100

MAIN CONTRIBUTOR ANDREW E. DAVIES

Report Issued by: ALAN WHITE

Report Reviewed by: CHRIS STEWART

Accepted by Task Officer on behalf of Defence Infrastructure Organisation:

Accepted by Sponsor:

SKM Enviros, Enviros House, Shrewsbury Business Park, Shrewsbury SY2 6LG Tel: +44 (0)1743 284800 Fax: +44 (0)1743 245558

GPSS Portfolio – Flax Bourton PSD Phase One & Two Land Quality Assessment Report Final

SKM Enviros

I:\JLWM\Projects\JL30611\Deliverables\Reports\Individual Sites\Flaxbourton PSD\Final Report\Flax Bourton Phase 1 & 2 LQA FINAL.docx

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Contents Land Quality Statement 1

Introduction 1

Site Description and History 1

Site Sensitivity 1

Potential Sources of Contamination 1

Preliminary Risk Assessment 2

Site Investigation Strategy 2

Investigation Works Undertaken 2

Ground Conditions Identified 2

Summary of Site Investigation Results 2

Updated Risks Assessment 3

Risk Descriptions 3

1. Introduction 4

1.1. Objectives 4

1.2. Methodology 4

1.3. Framework for Contaminated Land Assessment 5

1.4. Structure of this Report 6

2. Site Description 7

2.1. Site Location 7

2.2. Site Layout 7

2.3. Site Operations and Site Use 7

2.4. Surrounding Area 9

2.5. Public Register Information 9

3. Site History 11

3.1. Historical OS Maps 11

3.2. MOD and Other Sources 12

4. Site Sensitivity 15

4.1. Geology 15

4.2. Hydrogeology 15

4.3. Hydrology 16

4.4. Ecology 16

4.5. Site Sensitivity 16


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5. Initial Conceptual Site Model and Environmental Risk Assessment 17

5.1. Conceptual Model Outline 17

5.2. Potential Contaminant Sources 18

5.3. Identified Pathways 19

5.4. Identified Receptors 19

5.5. Preliminary Risk Assessment 19

5.6. Summary of Environmental Risks 23

6. Site Investigation Strategy 24

6.1. Scope of Works 24

6.2. Intrusive Works 24

6.3. Analytical Strategy 24

7. Site Investigation Methodology 26

7.1. Supervision 26

7.2. Summary of Works Undertaken 26

8. Summary of Ground Conditions 28

8.1. Ground Conditions 28

8.2. Natural Ground 28

8.3. Visual and Olfactory Contamination in Soils 28

8.4. Groundwater 29

9. Methodology for Interpretation of Chemical Analysis Data 30

9.1. Generic Assessment Criteria 30

9.2. Criteria for Assessment 30

9.3. Averaging Areas and Data Handling 31

9.4. Physico-chemical Soil Properties 31

10. Review of Laboratory Analysis 32

10.1. Chemical Soil Analysis 32

10.2. Surface Water Chemical Analysis 33

10.3. Summary of Analytical Data 34


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11. Updated Conceptual Site Model and Environmental Risk Assessment 36

11.1. Conceptual Site Model 36

11.2. Potential Contaminant Sources 37

11.3. Identified Pathways (All End-use Scenarios) 37

11.4. Identified Receptors (All Scenarios) 37

11.5. Updated Risk Assessment 37

11.6. Updated Risk Assessment Summary 41

12. Overall Land Quality and Suitability for Use 42

13. References 43

FIGURES

Figure 1: Site Location Plan

Figure 2: Site Layout, Potential Contaminant Sources and Exploratory Hole Locations

Figure 3: Initial Conceptual Site Model

APPENDICES

Appendix A Site Photographs

Appendix B Regulatory Data

Appendix C Historical Maps

Appendix D Risk Assessment Methodology

Appendix E Client Supplied Drawings

Appendix F Exploratory Hole Logs

Appendix G Laboratory Analysis Reports & Certificates

Appendix H Generic Assessment Criteria Methodology

Appendix I Assessment of Hydrocarbon Screening Value


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Land Quality Statement Introduction

In August 2012, SKM Enviros (SKM) was commissioned by the Defence Infrastructure Organisation (DIO) to undertake a combined Phase One and Two Land Quality Assessment (LQA) at the Government Pipelines and Storage System (GPSS) facility at Flax Bourton Petroleum Storage Depot (PSD), Station Road, Flax Bourton, North Somerset, BS48 1NG.

The objectives of this LQA, are to evaluate potential risks to human health and controlled waters which will allow identification of potential environmental risks for the MOD and support the disposal process for the site. The assessment has been completed on the understanding that the site is to be divested for continued or future commercial / industrial use (as a fuel management facility).

Site Description and History

GPSS Flax Bourton is centred on National Grid Reference (NGR) 350643, 169850 (ST506698), located, approximately 300 m north of the village of Flax Bourton, North Somerset, and approximately 9 km south west of Bristol City Centre. The site area is 6.84 hectares. The site is currently a mothballed petroleum storage depot which was operational between c 1939 and 1979, when operational large quantities of fuel were stored and handled on site. The main features are six semi-buried fuel tanks, high pressure fuel pipeline and associated infrastructure (slops tanks, manifold, pump house, electrical transformer, small work shop, offices etc). The majority of the fuel handling and storage was in below ground infrastructure except in the immediate vicinity of the manifold and pump house, where the high pressure pipeline was above ground.

Currently, the site is only used by a tenant farmer for grazing a small number of sheep and horses, and by visiting Costain personnel, who undertake general housekeeping and grounds maintenance tasks.

Site Sensitivity

Setting Description

Hydrogeology

The site is assessed as low to medium sensitivity with regard to groundwater as it is underlain by solid strata (Mercia Mudstone) classed as Secondary B Aquifer. The solid strata are overlain by superficial deposits (Head) classified as a Secondary Undifferentiated Aquifer. There are no recorded groundwater abstraction and source protection zones within 1 km of the site.

Hydrology

The site is assessed as having a high sensitivity with regard to surface water. The nearest surface water course, the Land Yeo river flows adjacent to the site’s north east boundary. It is thought that the site’s drainage flows through two interceptors and discharges to the river.

Ecology Ecological sensitivity has been assessed as being low as the site lies within an area of adopted green belt, but no other statutory designated areas are present within 1 km of the site.

Potential Sources of Contamination

Two groups of potential contaminant sources have been identified at the site; these are historical above and below ground fuel storage and handling (hydrocarbons) and electrical transformers (polychlorinated biphenyls (PCBs)).


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Preliminary Risk Assessment

Initially, a number of potentially significant risks from potential sources of contamination were identified based on the use of the site, history and sensitivity. The risks ranged from moderate to low depending on the potential source pathway receptor linkage. A targeted intrusive investigation was undertaken in order to refine the preliminary risk assessment.

Site Investigation Strategy

The objective of the intrusive investigation was to target areas identified as presenting the greatest risks to land quality, controlled waters and site users identified by the preliminary qualitative risk assessment. In the first instance, it was considered appropriate to investigate all sources of contamination where a moderate or greater risk was assessed. In addition it was also considered appropriate and cost effective, to investigate other sources at the same time given their similar nature. This will add additional confidence to the site investigation results and help deliver the objectives of the LQA. The works were planned to provide sufficient detail to allow identification of any major contamination concerns on site and the formulation of an outline remedial options assessment, if required, or more detailed investigation where necessary.

Investigation Works Undertaken

An intrusive investigation was undertaken in October 2012. A total of nine window sample holes were sunk to a maximum depth of 5 m below ground level. No groundwater was encountered during the boring and therefore none of the locations were installed as monitoring wells. Soil arisings from all window sample holes and hand dug pits were logged and samples were obtained for chemical analysis for key contaminants. Samples of the water from the Land Yeo river were collected on one occasion, from points upstream and downstream of the site. The surface water samples were tested for the same determinands as the soil samples.

Ground Conditions Identified

Limited made ground was identified across the site, and in all cases this comprised re-worked natural material, with no man-made artefacts identified.

Natural strata were encountered in all of the boreholes. The material was generally similar across the site and comprised approximately two metres of soft to firm silty, sandy, gravelly clay, with occasional discrete gravel bands. Below the clay, at depths of between approximately three to four metres below ground level a very weak mudstone was encountered.

Visual or olfactory evidence of suspected contamination in soils was detected in three of the nine window sample holes (WS2, WS5 and WS8), with very slight or slight suspected hydrocarbon odours recorded.

Summary of Site Investigation Results

The results demonstrate that there is not significant or extensive organic contamination on site; evidenced by a site-wide absence of organic contamination in any of the fourteen soil samples tested. Organic contamination was also absent from the two samples of surface water collected from the Land Yeo river.

One elevated concentration of lead, which exceeded the commercial / industrial Generic Assessment Criteria (GAC) was recorded at location, WS1. Concentrations across the rest of the site were much lower, and it is conjectured that the high lead concentration at WS1 is either an anomaly, or perhaps derived from historical fuel spills caused during refuelling of the old generator,


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which it is understood was located close by. All of the other inorganic determinands measured in the soil samples were recorded at low concentrations, below the respective GACs.

All of the inorganic determinands measured in the two river water samples were present at low concentrations which did not exceed the relevant Water Quality Standards (WQS).

Updated Risks Assessment

An updated qualitative risk assessment was undertaken at the site based on the findings of both the desk study and the intrusive investigation. This assessment carried out in accordance with government guidance on contaminated land, establishes connecting links between a hazardous source via an exposure pathway to a potential receptor (a “pollutant linkage”). The significance of any risk is based upon consideration of both the likelihood of an event and the severity of the potential consequence. Assessments have been completed for continued or future commercial / industrial use (as a fuel management facility). On this basis, the updated risk assessment did not identify any risks greater than Negligible with the exception of the risk to below ground workers from lead which is assessed as Moderate / Low, although this could be easily reduced to Negligible by use of appropriate PPE and risk assessment.

It should be noted that the assessment is based on a relatively small number of targeted sampling locations and there is the possibility that localised areas of contamination remain unidentified at the site. However, there is a good level of confidence from the information gathered that there is not significant and widespread contamination across the site.

Risk Descriptions

The following table provides definitions for the risk categories used in both the preliminary and updated risk assessments.

Term Description

Very High Risk

Severe harm to a receptor may already be occurring OR a high likelihood that severe harm will arise to a receptor, unless immediate remedial action works/mitigation measures are undertaken.

High Risk Harm is likely to arise to a receptor, and is likely to be severe, unless appropriate remedial actions/mitigation measures are undertaken. Remedial works may be required in the short term, but likely to be required over the long term.

Moderate Risk

Possible that harm could arise to a receptor but low likelihood that such harm would be severe. Harm is likely to be medium. Some remedial works may be required in the long term.

Moderate/ Low Risk

Possible that harm could arise to a receptor, but where a combination of likelihood and consequence results in a risk that is above low, but is not of sufficient concern to be classified as medium. It can be driven by cases where there is an acute risk which carries a severe consequence, but where the exposure is unlikely.

Low Risk Possible that harm could arise to a receptor. Such harm would at worse normally be mild.

Negligible Risk

Low likelihood that harm could arise to a receptor. Such harm unlikely to be any worse than mild.

Overall Land Quality and Suitability for Use

Overall, based on the findings of the desk study, intrusive investigation and risk assessments summarised above it is considered unlikely that there will be any land quality issues of concern constraining the use or redevelopment of the site for similar commercial / industrial use.


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1. Introduction In August 2012, SKM Enviros (SKM) was commissioned by the Defence Infrastructure Organisation (DIO) to undertake a combined Phase One and Two Land Quality Assessment (LQA) at the Government Pipelines and Storage System (GPSS) facility at Flax Bourton Petroleum Storage Depot (PSD), Station Road, Flax Bourton, North Somerset, BS48 1NG, hereafter referred to as GPSS Flax Bourton. This commission was carried out in accordance with the terms and conditions of FATS3, the Framework Agreement for Technical Support under Tasking Order FTS3/ELMG/100.

1.1. Objectives

The objectives of this LQA are to evaluate potential risks to human health and controlled waters which will allow identification of potential environmental risks for the MOD and support the disposal process for the site. The assessment has been completed on the understanding that the site is to be divested for continued or future commercial / industrial use (as a fuel management facility).

This LQA Report sets out the factual information and other evidence gathered through this desk based and subsequent intrusive assessment of the environmental condition of the site. The report establishes the overall site condition by identifying potential sources of contamination and receptors which may be sensitive to such contamination and by providing an appraisal of environmental risks.

1.2. Methodology

The assessment involved a review of available background information about the site and its neighbours from both public and Ministry of Defence (MOD) sources, together with a site reconnaissance undertaken on the 12th September 2012.

Information concerning current and past site use has been obtained by interviewing staff on site, from a review of historical site records and historical Ordnance Survey (OS) maps.

Information on the site sensitivity was obtained from geological and hydrogeological maps, together with information held by the Environment Agency and other regulatory authorities. These bodies were not contacted directly but the information was provided by a commercial search company, Landmark Information Group’s Envirocheck® report.

Data obtained from the public register relating to the site and its neighbours included information on the following:

Licensed and unlicensed waste disposal facilities (present and past);

Environmental Permits (formerly Integrated Pollution Prevention and Control Permits) under the Environmental Protection Act 1990;

Local Authority Environmental Permits (formerly Pollution Control Authorisations) under the Environmental Protection Act 1990;

Consents or enforcements under the Planning (Hazardous Substances) Act 1990;

Authorisations under the Radioactive Substances Act 1993;


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Information regarding contaminative uses from the planning register;

Consents to discharge to controlled waters;

Consents to discharge trade effluent to the foul sewer;

Licensed groundwater and surface water abstractions;

Details of pollution incidents; and

Breaches or prosecutions under environmental legislation.

Based on the information gathered an initial conceptual site model and qualitative risk assessment has been undertaken addressing the significance of any potential contamination identified in relation to the current and future commercial / industrial use of the site. The risk assessment was used to inform an intrusive investigation targeting those risks assessed as unacceptable or requiring further information to confirm the level of risk. The following works were undertaken on site between 29th and 30th October 2012:

Coring of nine boreholes using a Dando Terrier 2002 drive sampling rig to facilitate visual and olfactory observations of sub-surface conditions and collection of soil samples for laboratory analysis; and

Sampling of the Land Yeo river, which flows from east to west close to the site’s northern boundary. Samples were collected from one location upstream of the site and one location downstream of the site.

Based on the works described above and on the data following laboratory analysis of soil and surface water samples a Tier 1 generic risk assessment and update of the conceptual site model has been undertaken to assess the significance of any potential contamination identified in relation to the current or future commercial / industrial use of the site (as a fuel management facility).

1.3. Framework for Contaminated Land Assessment

Contaminated land risk assessment is based on development of a conceptual model for the site. This model is a representation of the relationship between contaminant sources, pathways and receptors developed on the basis of hazard identification. Risk assessment is the process of collating known information on a hazard or set of hazards in order to estimate actual or potential risks to receptors. The guiding principle behind this approach is an attempt to establish connecting links between a hazardous source, via an exposure pathway to a potential receptor, referred to as a ‘pollutant linkage’. If there is no pollutant linkage, then there is no risk. Therefore, only where a viable pollutant linkage is established does this assessment go on to consider the level of risk.

This approach is in accordance with the Department for the Environment Food and Rural Affairs (DEFRA) Statutory Guidance on Contaminated Land (Ref. 1) and the DEFRA / Environment Agency (EA) Model Procedures (CLR11, Ref. 2). The risk assessment undertaken in this document comprises a ‘preliminary risk assessment’ in the terminology used in CLR11.


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1.4. Structure of this Report

This report is structured as follows:

Chapter 2: Provides a description of the site layout and an outline of the activities undertaken and current potential sources of contamination;

Chapter 3: Outlines site history including a review of historical maps, anecdotal information from site sources and historical potential sources of contamination;

Chapter 4: Provides the environmental site setting and sensitivity in relation to its geology, hydrogeology, hydrology and ecology;

Chapter 5: Outlines the initial conceptual site model and qualitative risk assessment and provides justification for the areas prioritised for a further phase of intrusive assessment;

Chapter 6: Provides an outline of the site investigation strategy;

Chapter 7: Details the site investigation methodology;

Chapter 8: Summarises the ground conditions observed;

Chapter 9: Summarises the methodology for interpreting the chemical analysis results;

Chapter 10: Details the assessment of the chemical analysis results;

Chapter 11: Presents the updated conceptual site model for the site and the updated qualitative risk assessment;

Chapter 12: Presents a summary of the overall land quality and suitability of the site for its current and proposed use; and

Chapter 13: Details the references.


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2. Site Description

2.1. Site Location

GPSS Flax Bourton is centred on National Grid Reference (NGR) 350643, 169850 (ST506698), located adjacent the northern side of the Bristol to Taunton railway, approximately 300 m north of the village of Flax Bourton, North Somerset, and approximately 9 km south west of Bristol City Centre. The location of the site is shown on Figure 1.

2.2. Site Layout

The site occupies a total of 6.84 hectares (ha). The Ordnance Survey map shows the ground to be generally level with the 30 m contour passing through the centre of the site. The ground surrounding the site falls away gently to the north, with the 25 m contour running along the course of the Land Yeo river, and rising more steeply around 1 km south (beyond Flax Bourton village) to an elevation of approximately 130 m aOD.

The main access to the site is by means of a double metal security gate on Station Road in the east of the site. Within the site boundary there are six buried storage tanks, visible on the ground as flat topped circular mounds covered by short grass. The site is bisected through its centre by the route of a partially dismantled railway spur line (only occasional old railway sleepers remain), which adjoins the railway lines which run along the site’s southern boundary.

A number of small buildings are present in the east of the site, including offices, garage, mess room, w/c, store room and workshop. A temporary portacabin used by Costain personnel as a site office is located to the south of the site entrance. Additional buildings are present in the centre of the site, including a substation, manifold and pumphouse. The buildings are mostly constructed of concrete slabs with flat roofs covered by bitumen felt. Several track ways of asphalt surfacing pass from the eastern area of the site through the site’s centre, where they provide access to the entrance portals of each of the six storage tanks. Two underground slops tanks are located to the south east of Tank No. 6, and an emergency water storage tank is located further to the east of the two slops tanks. The water tank has a capacity of 30,000 gallons (136 m3). A brick structure, thought to be the site of an old generator (no longer present) is located in the north eastern area of the site.

All fuel pipeline infrastructure is buried below ground (including the pipelines entering and exiting the site, in the west), except in the immediate vicinity of the manifold and pumphouse, where the pipelines emerge above ground before passing into these two buildings.

A plan of the current site layout is shown in Figure 2. A selection of site photographs is provided in Appendix A.

2.3. Site Operations and Site Use

GPSS Flax Bourton is currently a mothballed petroleum storage depot situated on the Oil and Pipelines Agency (OPA) high pressure fuel pipeline network. No personnel are based on the site, although routine visits by Costain personnel to carry out housekeeping checks and grounds maintenance (e.g. grass cutting) are undertaken, these typically last less than one or two days. It is understood that all fuel/lubricants used as part of the ongoing programme of grounds maintenance carried out by Costain, are brought to site as and when needed. Spill kits for POL used during maintenance are carried in Costain vehicles.


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It was the opinion of the Costain site representative that all of the tanks were empty and that no fuel has passed through/been stored at the site since c.1979. The site representative had no records relating to any leaks or spills from the site, tank decommissioning, or of any previous integrity testing of any infrastructure on site.

Currently, a tenant farmer grazes a small number of livestock on the main area of the site (sheep and horses). Several of the animals were present at the time of the site visit.

2.3.1. Hazardous and Waste Material Storage

An electrical substation is present in the north of the site, with a transformer located adjacent to the north east corner of the substation building. Another transformer is located in the north west of the site. It was the opinion of the Costain representative that the transformer dated from the 1940s / 1950s, and on this basis it is possible that the transformer apparatus may have contained polychlorinated biphenyls (PCBs). However, it was not known whether the apparatus still contained PCBs and if so in what concentration.

It is understood that no waste materials are stored on the site. Any waste materials produced are bagged and removed by vehicle for disposal off site the same day. No other hazardous materials are stored on the site

2.3.2. Asbestos

It is beyond the scope of this LQA to assess or to provide an inventory of asbestos containing materials (ACMs) in the fabric of any current or former structures on the site. A copy of the asbestos survey report for the site is held at the Costain offices at Hallen PSD. The survey was carried out in March 2004 by DMW Safety Ltd. There is no known evidence of ground contaminated with ACMs.

2.3.3. Storage / Use of Munitions and Explosives

There are no known records of any explosive material ever being present on the site.

2.3.4. Burning Grounds and Incinerators

There is no known evidence or information relating to burning grounds or incinerators having ever been present at the site. The SKM walkover survey identified no evidence of areas of the site used for burning.

2.3.5. Radiological Materials

There are no known records of any radioactive materials having ever been stored or used on the site.

2.3.6. Vehicle Washing

It is understood that no vehicle washing has ever been undertaken on the site.

2.3.7. Site Services

No service plans (electrical, telecoms, water, etc) have been provided by Costain at the time of writing.


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2.3.8. Site Drainage and Discharge Consents

It is understood that the site’s surface water drainage, primarily from hardstanding areas in the east of the site and areas within the bunds surrounding the buried tanks, runs via a network of buried land drains to the site interceptors which are understood to be located in the north west and north east of the site. An Esso Petroleum site plan dated 1976 was photographed during the site visit and suggests that the drainage from both interceptors flows into the Land Yeo river. However, other plans included within the Dames and Moore International site investigation reports dated 1992 and 1996, indicate that a single (different) site interceptor is present at a distance of approximately 430 m north west of the current western boundary of the site, close to the southern bank of the Land Yeo river. This information is included in Appendix E. No recent plans showing the site’s drainage systems or details relating to the status of the interceptor have been reviewed by SKME. It should also be noted that the location/presence of the interceptor(s) was not known by the site representative at the time of the SKM site visit.

It is assumed likely that, on account of the mothballed status of the site, the drainage infrastructure in general has not been subject to maintenance in recent years. There are no recorded discharge consents associated with the site.

2.3.9. Other Information from the Site Visit

During the site visit it was noted that the site appeared to be generally well managed and was in a relatively tidy state with the majority of the site (except the eastern areas) being grazed by livestock (sheep, horses) belonging to a tenant farmer. The ungrazed areas were noted as being covered by rough grass, and it was the opinion of the Costain representative that grass cutting had not taken place for several months.

2.4. Surrounding Area

Adjoining the site’s north eastern boundary is the Land Yeo river, with agricultural land beyond. Disused railway sidings adjoin the western half of the site’s northern boundary. To the west of the site lies pasture used for grazing livestock (sheep and horses). To the south of the site, the Bristol to Taunton railway line adjoins the site boundary, with arable land beyond. To the east lies further arable land and several residential dwellings.

2.5. Public Register Information

The Envirocheck report, which contains public register information supplied by the Environment Agency and other statutory authorities, was purchased in August 2012. Key information relating to the site is identified and summarised below with a copy of the full report included in Appendix B. Information relating to discharge consents and water abstractions is discussed within Chapter 4 of this LQA.

2.5.1. Industrial Data Entries

The Envirocheck report identifies six Contemporary Trade Directory Entries within 1 km of the site, however, only two of these are currently reported as active. The two active entries relate to stained glass manufacture (283 m south west), and art restoration and cleaning (845 m east), both these entries are unlikely to affect the site.


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2.5.2. Fuel Station Entries

A closed fuel station identified as Farleigh Garage is located 954 m south west of the site. No other fuel stations are present within 1 km. Given the distance from site it is considered unlikely that this entry will affect the site.

2.5.3. Radon

The site is not in a Radon Affected Area (which is defined as an area with less than 1% of homes above the action level for radon).

2.5.4. Environment Agency Recorded Pollution Incidents

No EA recorded pollution incidents to controlled waters are identified in the Envirocheck report within 1 km of the site.

2.5.5. Contaminated Land Entries

There are no areas within 1 km of the site that have been determined as Contaminated Land under Section 78R of the Environmental Protection Act 1990.

2.5.6. Other Information

No records of other activities that may affect the site were identified within 500m.


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3. Site History The site history has been determined from a review of Ordnance Survey (OS) historical maps contained within the Envirocheck® report, and from information provided by site personnel during the site visit. The information below describes the significant historical activities on the site and surrounding area. The historical maps are presented in Appendix C.

3.1. Historical OS Maps

It should be noted that sites with a military or defence connection were often not included on OS maps during the war years and subsequent cold war, for reasons of national security.

3.1.1. On Site

The earliest map dated 1884 shows the site to be agricultural land, with no structures or other development present. A small footbridge can be seen crossing the Land Yeo river near to the site’s north east boundary.

The site remained as agricultural land up to the map dated 1934, which showed the presence at this time of shallow excavations or mounds, located within the eastern half of the site near to the site’s southern boundary.

Development of the site was evident from the Russian Military map dated 1972, with five tanks and several access roads shown.

The map dated 1977 to 1978 identified the site as a Depot, with six covered tanks and several access roads and buildings/structures shown. A branch line from the main railway line (located just to the south of the site), was shown crossing the centre of the site travelling in a north westerly direction. A level crossing was shown near to the site’s northern boundary.

No further changes are shown on later maps up to and including the most recent version dated 2012.

3.1.2. Off Site

The earliest map dated 1884 showed the surrounding areas to be predominantly agricultural field systems with occasional pockets of mixed woodland, and orchards in the vicinity of the villages of Flax Bourton and Farleigh, which were shown approximately 250 m south and 1 km south west respectively. The Great Western Railway (Bristol to Taunton Line) was shown, running adjacent to the site’s southern boundary. Buildings belonging to Bourton Mill (corn) were shown approximately 100 m east. . Several springs and issues were shown in the areas to the north and north west of the site.

The map dated 1903 showed that Bourton Mill was disused at this time.

The map dated 1921 identified Mail Apparatus on the railway, adjacent to the south west corner of the site.

The map dated 1932 shows small scale expansion of the villages of Farleigh and Flax Bourton.


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The map dated 1981 to 1982 indicated that continued expansion of Farleigh and Flax Bourton villages had taken place.A new residential development was also shown near to the north side of the railway between 300 and 600 m east of the site.

The maps dated 2006 and 2012 shows residential development near to Farleigh hospital, along with various drains, springs, issues and sinks present all around the site.

3.2. MOD and Other Sources

The GPSS was established to provide a secure oil distribution network for the United Kingdom at the beginning of World War Two in 1939. Over a period of years the pipeline route has been extended and amended, certain sections renewed and re-laid or diverted until it now covers approximately 2,500km of pipe and associated storage depots, pumping stations and other sites (Ref. 3).

GPSS Flax Bourton was commissioned and operated from circa 1939 until c.1979, and when operational was a petroleum storage depot situated on the Oil and Pipelines Agency (OPA) high pressure fuel pipeline network. It is understood that the fuel was pumped by underground pipeline to GPSS Flax Bourton for storage, from other GPSS facilities at Redcliffe Bay and Calne. It is also understood, from the site representative that several types of fuel passed through and/or were stored at the site, these included Jet A1 aviation fuel, kerosene, gasoline and diesel. Since the site’s closure in c.1979, the site has been mothballed, although it is understood that there have been recent plans to bring the site back into service.

In March 2012, Costain were awarded the asset support contract for the operation and maintenance of the GPSS on behalf of the OPA.

3.2.1. Historical Petroleum, Oil and Lubricant (POL) Storage

The main feature of the site are the six partially buried underground storage tanks (UST) which previously contained the fuels. In addition, two smaller slops tanks are also present. The tanks are of reinforced steel and concrete construction. All of the tanks are surrounded by earth bunds approximately three metres in height.

Table 3.1: Details of historical POL storage tanks at GPSS Flax Bourton

Tank Ref. AST/UST Tank Contents Dimensions (m) Volume (litres)

No. 1 UST

Currently empty - previous contents

not known.

35 (w) x 7 (h) 245,000

No. 2 UST 32 (w) x 7 (h) 224,000

No. 3 UST 32 (w) x 7 (h) 224,000

No. 4 UST 32 (w) x 7 (h) 224,000

No. 5 UST 32 (w) x 7 (h) 224,000

No. 6 UST 32 (w) x 7 (h) 224,000

Slops Tank 1 UST Waste fuels

9 (w) x 3 (h) 27,000

Slops Tank 2 UST 9 (w) x 3 (h) 27,000


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It was the opinion of the Costain site representative that all of the tanks were empty and that no fuel has passed through/been stored at the site since c.1979, although no evidence of this was available from the site representative. When operational the pipeline running beneath the site was regularly inspected using a ‘pig’ and telemetry at each end of the pipeline records liquid volumes (and potential loss of product). Any significant leaks would be detected and dealt with promptly. No visual evidence of spillage or residual contamination from historical fuel spills was identified during the site visit, and there are no records of spills or leaks held by the site representative.

3.2.2. Previous Investigations on Site

SKME undertook a visit to the OPA archives in December 2012. The following information sources were reviewed during this visit:

Three phases of site investigation works were completed by Dames and Moore International in 1992, 1995 and 1996. The objectives of each investigation were to assess the potential for significant contamination to exist on the site as a result of activities relating to the storage and handling of aviation fuel over approximately the previous forty years. A combination of shallow boreholes and trial pits were excavated during these site investigations and samples of shallow soils and groundwater were collected and analysed for the presence of hydrocarbons.

1992 Site investigation

Twelve shallow boreholes sunk, with twelve soil and five groundwater samples collected;

Concentrations of contaminants detected in soils and groundwater were not suggestive of the presence of a significant source of hydrocarbons in the soil or of a dissolved phase plume of hydrocarbon contamination within groundwater;

Results said to be indicative of residual contamination, probably from previous small releases of hydrocarbons across the site at each targeted exploratory location at depths of between 1.5m and 2.5m below ground level; and

No groundwater samples collected from boreholes sunk in the tank area as groundwater was not encountered at the depths investigated.


Five boreholes sunk in the tank area and four groundwater samples collected;

Evidence of hydrocarbon contamination was identified at only one location (MW-101, adjacent the northern side of Tank 1); evidenced by the presence of hydrocarbon vapours in shallow soils and a sheen on the purged water during sampling of this well. TPH concentrations were also present within the groundwater sample from this location at around 1000 µg/l;

No BTEX compounds were identified at concentrations greater than the laboratory detection limits;

Hydrocarbons identified near to Tank 1 were thought to be indicative of previous minor leakage. There was no evidence visible of this during the 2012 site walkover; and


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It was concluded that the difference (i.e. decline) in BTEX concentrations in groundwater between 1992 and 1995 investigations was attributed to natural biodegradation of the hydrocarbons.


Eleven boreholes and ten trial pits excavated across the site, and one groundwater sampling round undertaken, in which a total of ten samples were collected;

Soil samples were collected from seven trial pits and three boreholes; no significant contamination was identified at any location;

Groundwater samples were analysed for TPH and BTEX compounds. Two locations in the north east of the site (209 and 210) contained marginal TPH concentrations, just above the laboratory limits of detection;

Residual hydrocarbon contamination identified (relatively elevated TPH concentrations) again at MW-101. The results were similar to those obtained in 1995;

Analysis of water samples from the Land Yeo river did not suggest there was any contaminant migration to the river;

The overall conclusions drawn following the completion of the three phases of assessment were that the investigation results did not suggest there was significant widespread contamination at the site, aside from residual localised (and relatively low level) hydrocarbon contamination around MW-101; and

That the site should not be considered a concern to the Environment Agency, within the context of its continued mothballed industrial use and environmental setting.


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4. Site Sensitivity

4.1. Geology

4.1.1. Made Ground

The geological map for the area (Ref. 4) identifies the presence of Made Ground within the western area of the site, corresponding with the location of the five buried storage tanks. The composition of the Made Ground is not specified. However, the previous investigations identified local areas of Made Ground (particularly in the vicinity of the rail track) up to 0.6m thick comprising limestone ballast and ash.

4.1.2. Drift

The geological map for the area (Ref. 4) indicates that superficial deposits comprising Head are present over the entire site and is described as being formed from clay, silt, sand and gravel. This description was confirmed in the exploratory hole logs from the previous investigations.

4.1.3. Solid

The BGS website (Ref. 4) indicates that all areas of the site are underlain by rocks of the Mercia Mudstone Group, comprising mudstone and halite-rich sedimentary bedrock. This was confirmed in the exploratory hole logs from the previous investigations which encountered the Mudstone at depths from approximately 1.5m to approximately 4m below ground level.

4.2. Hydrogeology

The Environment Agency (EA) website (Ref. 5) records the superficial deposits (Head) beneath the site as a Secondary Undifferentiated aquifer. Note: This designation has been assigned in cases where it has not been possible to attribute either category A or B to a rock type. In most cases, this indicates that the layer in question has previously been designated as both a minor and a non-aquifer in different locations due to the variable characteristics of the rock type. The groundwater vulnerability map indicates that the site is underlain in the east of the site by soils of a low leaching potential, and in the west of the site by a non-aquifer. Therefore, the overall potential of the soils beneath the site to transmit contaminants to groundwater below is assessed as low.

The mudstone bedrock is recorded as a Secondary B Aquifer, comprising strata which are predominantly of lower permeability, and which may store and yield limited amounts of groundwater due to localised features such as fissures, thin permeable horizons and weathering. These layers are generally the water-bearing parts of the former non-aquifers.

The EA website (Ref. 5) does not list the site area as being a designated groundwater source protection zone.

The Envirocheck report identifies one current groundwater abstraction for domestic use at 788 m north west of the site.


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4.3. Hydrology

The nearest surface water is the Land Yeo river which runs along the site’s north eastern boundary; and flowing approximately on an east to west course. A pond identified as a Bathing Pond on the OS 1:25,000 scale map is located approximately 300 m north east of the site, within the woods of the same name. Several springs and issues are present approximately 750 m north west of the site, while two sinks are identified approximately 50 m south east of the site.

The Environment Agency General Quality Assessment (GQA) Scheme assesses surface waters in England and Wales according to their chemical and biological quality. The nearest monitoring point is on the Land Yeo, and is located approximately 3.8 km north west (i.e downstream of the site), where the river is classified as A (very good) for chemistry, unclassified for biology, and 4 (medium to high) for nitrate and 3 (medium) for phosphate (Ref. 5).

Two licensed discharge consents are recorded within the Envirocheck report within 1 km of the site. The first is located 525 m north east and relates to a soakaway for domestic sewage, and the second to discharge of site drainage from a gravel quarry to a tributary of the Land Yeo, 574 m south east.

The EA website indicates that the floodplain around the Land Yeo to the north west and south east of the site, but also extending within the central area of the site, is likely to flood with a probability of flooding of 1 per cent (1 in 100) each year.

4.4. Ecology

The site lies within an area of adopted green belt land as sanctioned by North Somerset Council in 2007. No other ecologically sensitive areas are present within 1 km of the site.

4.5. Site Sensitivity

Groundwater sensitivity: Low to Medium

The site is assessed as low to medium sensitivity with regard to groundwater as it is underlain by solid strata classed as Secondary B Aquifer, which is overlain by superficial deposits classified as a Secondary Undifferentiated Aquifer.

Surface Water Sensitivity: High

The site is assessed as having a high sensitivity with regard to surface water. The nearest surface water course, the Land Yeo river flows adjacent to the site’s north east boundary. It is understood that the site’s surface water drainage is discharged to the river, following passage through two interceptors.

Ecological Sensitivity: Low

Ecological sensitivity has been assessed as low as the site lies within an area of adopted green belt, but no other statutory designated areas are present within 1 km of the site.


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5. Initial Conceptual Site Model and Environmental Risk Assessment

This chapter presents the initial conceptual site model (CSM) developed for the site and identifies the presence of any potentially unacceptable risks. The conceptual model is a representation of the relationship between contaminant sources, pathways and receptors developed on the basis of hazard identification. Unique identification numbers or letters are allocated to each source, pathway and receptor; these are then carried forward to the CSM (as shown on Figure 3) and the risk assessment.

5.1. Conceptual Model Outline

The following provides a brief summary of the key features of the site (as detailed in full in Chapters 2 to 4) of relevance to the risk assessment. This initial conceptual model is shown schematically in Figure 3 along with the contaminant sources detailed below.

The site occupies an irregular area of level ground at approximately 30m aOD, covering approximately 6.84 hectares (ha), located to the north of the Bristol to Taunton railway line, and to the south of the Land Yeo river. The ground surrounding the site falls away gently to the north, with the 25 m contour running along the course of the Land Yeo river.

The site is currently a mothballed petroleum storage depot which was operational between c 1939 and 1979. Within the site boundary there are six buried fuel storage tanks with individual capacities of 224,000 litres to 245,000 litres, visible on the ground as flat topped circular mounds covered by short grass. The main area of the site (areas to the west of the disused railway sidings) containing the buried tanks is grazed by sheep and horses belonging to a tenant farmer. There are several small buildings present in the east of the site, including offices, garage, mess room, w/c, store room and workshop. Additional buildings are present in the centre of the site, to the north east of the buried tanks, and these include a substation, manifold and pumphouse. A brick structure is present in the north east of the site, and it is thought that this was once the location of a generator, although this is no longer present. Several asphalt access tracks pass from the eastern area of the site through the site’s centre, where they provide access to the entrance portals of each of the six storage tanks.

All fuel pipeline infrastructure is buried below ground (including the pipelines entering and exiting the site to the north west); the exception to this is in the immediate vicinity of the manifold and pumphouse, where the pipelines emerge above ground before passing into these two buildings. A substation is present in the north of the site along with two small transformers, one of which is adjacent the substation, while the other is located in the north west of the site, near to the area used for starting pipeline inspections using the pig – known as the ‘pig launching area’.

The site is underlain by superficial deposits (head) classified as a Secondary Undifferentiated Aquifer and by solid strata (Mercia Mudstone) classified as a Secondary B Aquifer.

The nearest surface water course is the Land Yeo river, which flows in close proximity to the northern boundary of the site along its entire length. The site lies within an adopted area of green belt; although, there are no further ecologically sensitive areas/habitats within 1 km.


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The site’s surface water drainage passes through two interceptors which are located in the north west and north east of the site. The location of the interceptor discharge is thought to be into the Land Yeo river to the north of the site.

The future end use for which the assessment has been undertaken is continued or future commercial / industrial use (as a fuel management facility).

5.2. Potential Contaminant Sources

Two potential sources of contamination have been identified at the site including current and historical sources:

5.2.1. On Site

The potential onsite sources of contamination at the GPSS Flax Bourton site include:

Potential Source Number (Carried to Risk Assessment)

Potential Source Description

Potential Source Location Area

(Shown on Figure 2 and 3)

S1 Electrical substation and two transformers, located in the north-central and north west of the site (oils and polychlorinated biphenyls (PCBs)).

Ref. 1

S2

Non-operational above and below ground high pressure fuel pipelines, storage tanks, and associated infrastructure (manifold, pumphouse, pig launching area, loading gantry, interceptors, site of old generator (hydrocarbons)).

Ref. 2.1

5.2.2. Off Site

The potential sources of contamination off site include:

Potential Source Number

(Carried to Risk Assessment)

Potential Source Description

Potential Source Location Area

(Shown on Figure 2 and 3)

S2 Non-operational below ground high pressure fuel pipeline (hydrocarbons). Before entering / exiting the site to the north west.

Ref. 2.2


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5.3. Identified Pathways

Potential environmental fate and exposure pathways specific to the site are:

Direct contact, ingestion or inhalation (pathway P1);

Leaching of contamination from soils via rainwater infiltration (pathway P2);

Vertical and lateral migration in groundwater (pathway P3);

Surface runoff into the adjacent surface water (pathway P4)

Direct contact (buildings and services) (pathway P5); and

Vapour migration and accumulation of vapours (pathway P6).

5.4. Identified Receptors

Potential receptors specific to the site are:

Human health Current and future site users under commercial industrial use (receptor A).

Human health Personnel involved in below ground and maintenance works (receptor B).

Groundwater Head (Secondary Undifferentiated Aquifer) and Mudstone (Secondary B Aquifer) (receptor C).

Surface Water Land Yeo river (receptor D).

Buildings and Services As a result of chemical attack or vapour ignition / explosion – whilst buildings are currently mothballed, future recommissioning is possible (receptor E).

Grazing livestock Sheep and horses currently graze the western and central areas of the site (receptor F).

5.5. Preliminary Risk Assessment

A preliminary risk assessment has been undertaken for these potential source-pathway-receptor linkages to identify potentially unacceptable risks on a qualitative basis. This approach is based on DEFRA (Ref. 6) and Construction Industry Research and Information Association (CIRIA) guidance (Ref. 7) on risk assessment and Model Procedures, whilst reference has also been given to the DIO LQA Management Guide (Ref. 8). Risk is therefore based on a consideration of both:

the likelihood of an event (probability – takes into account both the presence of the hazard and receptor and the integrity of the pathway); and

the severity of the potential consequence (takes into account both the potential severity of the hazard and the sensitivity of the receptor).

Further information on the risk assessment methodology used is given in Appendix D. The method of dealing with identified risks and the level of significance of those risks will be a function of site use. Potentially unacceptable risks identified for current or continued commercial / industrial use of the site are considered in Table 5.1 and summarised in Table 5.2.


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Table 5.1: Potential environmental risks for current / future commercial / industrial use and during below ground and maintenance works

Potential Source

Potential Pollutant

Potential Receptors

Potential Pathways

to Receptors

Associated Hazard

[severity]

Likelihood of Occurrence

Risk / Significance

S1 Electrical Substation and Transformers

PCBs Humans Health hazard It is possible that the transformer apparatus may have contained polychlorinated biphenyls (PCBs) given its age. However, it was not known whether the apparatus still contained PCBs and if so at what concentration. However, the transformer is of a small size, therefore only small volumes of oil may have leaked. Any impacted ground likely to be very localised.

A. Current and future use

P1. Direct contact, ingestion, inhalation

Medium Unlikely Disturbance of the ground in the vicinity of the transformer is unlikely during normal operations.

Low

B. Below ground and Maintenance workers

P1 - Direct contact, ingestion, inhalation

Medium Low Likelihood Disturbance of the ground is likely, but any exposure during groundworks will be very short term (acute rather than chronic).

Moderate / Low

(Could be reduced to Low by utilising appropriate PPE / risk assessment)

Controlled Waters

Environmental Impact

It is possible that the transformer apparatus may have contained polychlorinated biphenyls (PCBs) given its age. However, it was not known whether the apparatus still contained PCBs and if so at what concentration. However, the transformer is of a small size, therefore only small volumes of oil may have leaked. Any impacted ground likely to be very localised.

C. Groundwater

Secondary Undifferentiated and Secondary B Aquifer

P2 and P3. Leaching of contamination from soils by rainwater infiltration and migration through groundwater

Impact on groundwater quality

Medium

Unlikely

PCBs are highly immobile in the environment and unlikely to migrate far from the source of deposition.

Low


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Potential Source

Potential Pollutant

Potential Receptors

Potential Pathways

to Receptors

Associated Hazard

[severity]


Risk / Significance

S1 Electrical Substation and Transformers continued

PCBs continued D. Surface Water

P2, P3 and P4. Leaching of contamination from soils by rainwater infiltration and migration through groundwater in hydraulic continuity with the surface water and surface runoff

Impact on surface water in Land Yeo river

Medium

Unlikely

PCBs are highly immobile in the environment and unlikely to migrate far from the source of deposition. It is considered unlikely that appreciable quantities of PCBs (if present) would reach the river.

Low

F. Grazing livestock (sheep and horses)


Health of livestock

Medium

Unlikely

No visual evidence of contamination or vegetation die back. Any contamination present is likely to be relatively immobile and highly localised.

Low

S2 Non operational above and below ground high pressure fuel pipelines (on and off site) and associated apparatus; storage tanks (on site); interceptors (on site); former generator (no longer present) (on site).

Hydrocarbons Humans Health hazard All above/below ground pipework and tanks are non-operational. No evidence of spills or leaks, although there are no integrity test results available for below ground components. The GPSS operational pipeline network is inspected regularly; however, as the site is mothballed it is not known how often the site infrastructure is inspected, if at all.



Medium Unlikely Disturbance of the ground is unlikely during normal operations.

Low

B. Below Ground and Maintenance workers


Mild Low Likelihood Disturbance of the ground is likely, but any exposure during groundworks will be very short term (acute rather than chronic).

Low

(Could be reduced to Negligible by utilising appropriate PPE / risk assessment)


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Potential Source

Potential Pollutant

Potential Receptors

Potential Pathways

to Receptors

Associated Hazard

[severity]


Risk / Significance

S2 Non operational above and below ground high pressure fuel pipelines (on and off site) and associated apparatus; storage tanks (on site); interceptors (on site); former generator (no longer present) (on site). continued

Hydrocarbons continued

Controlled Waters


All above/below ground pipework and tanks are non-operational. No evidence of spills or leaks, although there are no integrity test results available for below ground components. The GPSS operational pipeline network is inspected regularly; however, as the site is mothballed it is not known how often the site infrastructure is inspected, if at all.

C. Groundwater




Severe [severe classification primarily due to the potentially large volumes of contaminant]

Low likelihood Presence of contamination has not been proven, however if storage tanks have leaked in the past, the underlying aquifer may be directly affected.

Moderate

D. Surface Water

Land Yeo river

P3. Migration through groundwater base flow

Impact on surface water

Severe [severe classification primarily due to the potentially large volumes of contaminant and proximity of surface waters]

Low likelihood No pollution incidents related to hydrocarbons have been reported by the Environment Agency. The tanks have been mothballed since 1979 and previous investigations have not identified substantial contamination.

Moderate

P4. Surface water runoff

Impact on surface water Medium

Low Likelihood No contamination visible on ground surface and no pollution incidents in relation to the site have been reported. Infrastructure has been mothballed since 1979 so the likelihood of new leaks and spills is limited. The area of site closest to the river has not been used for fuel storage.

Moderate / Low


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Potential Source

Potential Pollutant

Potential Receptors

Potential Pathways

to Receptors

Associated Hazard

[severity]


Risk / Significance

S2 Non operational above and below ground high pressure fuel pipelines (on and off site) and associated apparatus; storage tanks (on site); interceptors (on site); former generator (no longer present) (on site) continued


E. Buildings and Services

P5. Direct contact

Damage to buildings and services Mild

Low Likelihood Site mothballed in 1993. Buildings and services have been present many years and no impacts to date.

Low

P6. Vapour accumulation

Damage to services and structures Severe

Low Likelihood No evidence or records of spills or leaks and buildings and services have been present many years with no recorded impacts to date. Presence of significant volumes of contamination within subsurface is possible given the size of the infrastructure and the integrity of redundant underground tanks not established.

Moderate



Health of livestock

Medium

Low likelihood

No visual evidence of contamination or vegetation die back.

Moderate / Low

5.6. Summary of Environmental Risks

Table 5.2 summarises the risks from the potential sources identified.

Table 5.2: Summary of Preliminary Risk Assessment

Usage Scenario

Electrical Substation and Transformers

Above/Below Ground High Pressure Fuel Pipelines and

Associated Apparatus, Storage Tanks, Interceptors;

Site of Old Generator

CSM Source S1 CSM Source S2

Human health: Current and future commercial / industrial use

Low Low

Human health: During below ground maintenance works

Moderate / Low* Low*

Groundwater Low Moderate

Surface Water (via baseflow) Low Moderate

Surface water (via runoff) Low Moderate / Low

Buildings and services (direct contact) - Low

Buildings and services (vapour accumulation) - Moderate

Grazing livestock (sheep and horses) Low Moderate / Low

*Risk can be reduced by utilising appropriate risk assessment and personal protective equipment (PPE)


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6. Site Investigation Strategy

6.1. Scope of Works

The objective of the intrusive investigation was to target areas identified as presenting the greatest risks to land quality, controlled waters and site users identified by the preliminary qualitative risk assessment. In the first instance, it was considered appropriate to investigate all sources of contamination where a moderate or greater risk was assessed. In addition it was also considered appropriate and cost effective, to investigate other sources at the same time given their similar nature. This will add additional confidence to the site investigation results and help deliver the objectives of the LQA. These areas are summarised in Table 6.1.

Table 6.1: Selected Investigation Targets

Potential Source

Ref. Highest Risks

Identified Source Description

Contaminants of Concern

1. Electrical substation and

two small transformers

1

Moderate/Low risk to construction workers during below ground works

Electrical substation

PCBs

Two small transformers

2. Non-operational above and

below ground high pressure fuel pipelines and storage tanks, and associated

apparatus; site of old generator;

interceptors

2.1 Moderate risk to groundwater, surface water and buildings and services

Underground fuel storage tanks

Hydrocarbons

Underground fuel supply pipeline

Manifold

Pumphouse

Pig Launching Area

Loading Gantry

Interceptors

2.2 Underground fuel supply pipeline (off site)*

*Offsite source not targeted for investigation but should be factored into the assessment of results.

6.2. Intrusive Works

An intrusive investigation has been designed to effectively target the highest identified risk sources listed in Table 6.1. At this stage the intention is that the planned works would provide sufficient detail to allow identification of any major contamination concerns on site and the formulation of an outline remedial options assessment, if required, or more detailed investigation where necessary.

6.3. Analytical Strategy

The development of the initial CSM included consideration of the potential contamination present on site at each identified source. The chosen analysis suite takes into account the findings of the desk study described in Chapters 2 to 4. Samples will be selected for analysis on the basis of historical information about site activities, and olfactory and visual evidence from the arisings observed. The suites for soil and water are described in Table 6.2.


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Table 6.2: Selection of Laboratory Analytical Suites for Soils and Surface Water

Suite Reasoning behind Sampling Regime

Metals / Metalloids

Cyanide

Phenol (monohydric)

Speciated PAHs (16)

Speciated TPH (CWG)

Monoaromatic hydrocarbons (BTEX and MTBE)

PCBs

A general suite of analysis was selected to adequately cover the potential soil contaminants described in Table 6.1


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7. Site Investigation Methodology

7.1. Supervision

Throughout the works supervision was provided by SKM Enviros. This involved the selection of window sample positions, instruction and co-ordination of drilling subcontractors, logging of investigation arisings, appropriate field testing and monitoring and collection of soil samples.

7.2. Summary of Works Undertaken

7.2.1. Selection of Intrusive Locations and Service Clearance

Approximate locations for the majority of exploratory excavations were predetermined based on the findings of the desk study, identification of potential sources of contamination and preliminary qualitative risk assessment. A plan was sent to the site contacts for consideration prior to the commencement of intrusive works.

Service plans, provided by Costain, were consulted to aid location of each position in order to avoid buried services. Before commencement of drilling, each location was scanned with a cable avoidance tool (CAT). As an additional precaution a hand-dug observation pit was then excavated to a maximum depth of 1.2 m below ground level (bgl).

7.2.2. Window Sample Boring

Boreholes were sunk at nine locations using window sampling techniques, the locations are illustrated on Figure 2. The rig used was a Dando Terrier 2002 (Drive Sampling Rig), incorporating a percussion hammer, which was used to drive a one metre long sample barrel into the ground to recover soil samples for logging in a clear plastic sleeve liner. A clean liner was used on each one metre run to reduce the likelihood of cross contamination between horizons. Where necessary a 110 mm diameter casing was driven into the ground by the sample barrel to keep the boreholes open for further progress. Window sampling techniques enabled good sample returns and also created minimal surface disturbance. A selection of photographs showing the window sample rig set up at locations across the site is presented in Appendix A.

7.2.3. Soil Sampling

Soil arisings from all excavations were examined for visual and olfactory evidence of contamination and logged in general accordance with BS:5930 and EN ISO 14688. Excavation logs are provided in Appendix F. A selection of photographs showing the arisings seen on site are presented in Appendix A.

Soil samples were collected at regular intervals, on changes in strata and from any areas where visual or olfactory contamination was observed. Soil samples were obtained from the arisings using a stainless steel trowel. All sampling equipment was cleaned between samples to minimise as far as was reasonably practicable, the potential for cross-contamination. Visible dirt was removed from the stainless steel trowel after the collection of each sample and if further cleaning was necessary the trowel was also washed with detergent (Decon 90).


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Soil samples were collected, placed in sealed sample containers (appropriate to the type of analysis to be undertaken and compliant with the laboratory’s UKAS and MCERTS methodologies) and labelled with site specific sample identification. All samples were packed into pre-chilled cool boxes with frozen ice packs, along with chain of custody documentation. Samples were transported by courier to I2 Analytical Laboratories. Soil samples were tested to MCERTS standards where appropriate.

7.2.4. Groundwater Sampling

No groundwater sampling was undertaken as groundwater was not encountered during the works. The presence of groundwater cannot be ruled out as previous investigations did encounter it, but the variability of the superficial deposits in the area could lead to localised pockets of groundwater, this is reflected in the Undifferentiated Aquifer classification

7.2.5. Surface Water Sampling

Two samples of water were collected from the Land Yeo river on one occasion, 29th October 2012.

Land Yeo (A): Upstream of the site; collected from the northern bank of the river, immediately downstream of the road bridge (Station Road crossing the Land Yeo); and

Land Yeo (B): Downstream of the site; collected from the northern bank of the river, opposite the north-western corner of the site.

Sample locations are illustrated on Figure 2. All water samples were collected in clean sample containers, relevant to the type of analysis required and provided by the accredited laboratory (I2 Analytical). The samples were taken directly into the sample containers. All sample containers were appropriately labelled with their location, packed into pre-chilled cool boxes, along with chain of custody documentation and transported by courier to the laboratory.


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8. Summary of Ground Conditions

8.1. Ground Conditions

This chapter summarises the ground conditions encountered during the Phase Two investigation of the site. Borehole logs are provided in Appendix F. The generalised sequence of deposits beneath the site is summarised in the following sections.

8.1.1. Made Ground

Made ground was encountered in six of the nine boreholes sunk across the site. The made ground comprised reworked natural material at each of the six locations (WS2, WS3, WS4, WS7, WS8, WS9) and was identified to a maximum depth of 1.80m at WS9. No man-made artefacts such as concrete, brick or glass, etc. were identified at any location.

8.2. Natural Ground

Natural strata were encountered in all of the boreholes. The material was generally similar across the site, and can be summarised in sequence (with increasing depth):

Soft red brown to brown, silty, sandy, and slightly gravelly clay. Identified at WS1, WS5 and WS6;

Firm to stiff red brown and mottled greenish-grey, occasional slightly gravelly (sandstone) clay, identified at all locations;

Occasional sandstone gravel bands, of between 0.1 and 0.25 m thickness, present within the clay. Identified at WS1, WS4, WS5 and WS7; and

Very weak red brown and occasionally mottled greenish-grey mudstone. Identified at all locations except WS1 and WS2.

This is consistent with the review of geological maps in advance of the intrusive works, which suggested that the site is located on superficial deposits of Head (clay, silt, sand and gravels), and solid strata of the Mercia Mudstone group. The findings are also consistent with the previous investigations, with the exception of the Made Ground descriptions, which previously described ash.

8.3. Visual and Olfactory Contamination in Soils

Visual or olfactory evidence of contamination was detected in three of the nine boreholes drilled. These are detailed in Table 8.1.


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Table 8.1: Visual and Olfactory Evidence of Contamination

Location Potential Source Depth (m bgl)

Soil Type Description of Contamination

WS2 Ref 2.1 – Loading Gantry

2.2 to 2.3 Slightly gravelly clay

Slight suspected hydrocarbon odour

WS5 Ref 2.1 – Underground tank (Tank 3)

1.2 to 1.4 Silty clay Very slight suspected hydrocarbon odour

WS8 Ref 2.1 - Pumphouse

3.9 to 4.2 Mudstone Slight suspected gasoline/kerosene odour

8.4. Groundwater

Groundwater was not encountered during the site investigation, but its presence cannot be ruled out due to the variability of the superficial deposits in the area, which is reflected in the Undifferentiated Aquifer classification.


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9. Methodology for Interpretation of Chemical Analysis Data

9.1. Generic Assessment Criteria

In order to put the analytical results into context, the data for the site have in the first instance been screened against generic assessment criteria (GAC) derived from a number of sources. This is known as a Tier 1 assessment. Depending on the results of Tier 1 analysis further tiers of assessment may be deemed necessary.

9.2. Criteria for Assessment

The following information details the selection of generic criteria for the Tier 1 assessment.

9.2.1. Hazards to Human Health

Human health risk assessment has been undertaken in accordance with the approach currently advocated by the Environment Agency (EA) and DEFRA in England and Wales, using the CLEA (Contaminated Land Exposure Assessment) model. (Ref. 2). The model evaluates the risks to human health from contaminants via different pathways for a range of land use scenarios based on a detailed review of published research. To date, the Environment Agency has published Soil Guideline Values for five metals / metalloids (arsenic, cadmium, selenium, nickel and mercury) and six organic compounds (benzene, xylene, toluene, ethylbenzene, phenol and for dioxins, furans and dioxin-like PCBs).

For common substances where there is no SGV, SKM Enviros has calculated screening thresholds (GACs) for the standard CLEA land uses using the current CLEA methodology and model (version 1.06). The derivation of SKM Enviros GAC, including that for petroleum hydrocarbons, is fully detailed within Appendix H and I. All GACs are appropriate for industrial / commercial land uses.

9.2.2. Potential Contamination of Controlled Waters

The consideration of water pollution has been made in the specific context of the site and the risk it presents to controlled water. Given the controlled water receptors identified (Land Yeo river) comparison to annual average Environmental Quality Standards (EQS) for cyprinid fish have been made. Groundwater was not encountered during the investigation.

9.2.2.1. EQS

EQS are concentrations below which it is generally accepted that a contaminant will have no effect on the aquatic environment. However, even when an EQS is exceeded, this does not necessarily mean that there is a significant impact on aquatic organisms or plants. Further studies would be required to confirm the extent of any impact. The full list of the EQS used in this assessment is provided as Ref. 9 to 11.

In Chapter 10, EQS and DWS (drinking water standards) are referred to collectively as WQS (water quality standards).


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9.2.2.2. Hydrocarbons

The EQS and DWS for petroleum hydrocarbons refer to visual and olfactory evidence or are based on a determination of the ‘effect’ on the receiving ecosystem. Therefore, there is no absolute value available for comparison of laboratory data.

A Tier 1 screening value of 500 µg/l is proposed (for kerosene/diesel/fuel oil), based on the following:

An Intervention Value of 0.6 mg/l for mineral oil in groundwater cited in the Dutch government guidelines (Ref. 12);

Remediation criteria for benzene of 0.3 mg/l and for ethyl benzene of 0.7 mg/l for freshwater aquatic life cited in Canadian Environmental Quality Criteria (Ref. 13); and,

A 48 hour “no-observed effect loading rate” to the water flea (Daphnia magna) due to kerosene contaminated water of between 0.3 and 0.9 mg/l (depending upon the type of hydrocarbon measured – Ref. 14).

Of note is that the Bathing Waters (Classification) Regulations limit for mineral oil is that there is no film visible on the surface of the water and that there is no fuel odour (Ref. 15). More detailed justification is provided in Appendix H.

9.3. Averaging Areas and Data Handling

Consideration has been given to the most appropriate method of grouping the data. This can include separating the data spatially or by the different strata underlying the site. The required approach may differ for different contaminants as some may be associated with particular current or historical activities carried out in a particular location while others may be associated with materials (such as made ground) brought on to the site.

At GPSS Flax Bourton, intrusive locations were selected to target individual potential contaminant sources. Therefore, it is not considered appropriate to group the data spatially or by strata to undertake statistical analysis. Furthermore, the Made Ground identified was at all locations, reworked natural material. Guideline standards were compared to discrete samples for Tier 1 assessment. Where the laboratory has recorded results less than the LOD, the LOD has been used as the screening value.

9.4. Physico-chemical Soil Properties

Certain soil properties will greatly affect the mobility, migration and availability of contaminants. It is important to assess these properties prior to Tier 1 screening in order that the results can be interpreted in the correct context.

9.4.1. Soil Organic Matter

The mobility of organic contaminants can be strongly influenced by the organic content of the soil. This particularly affects the exposure pathways involving absorption and inhalation for soil vapours as well as the leachability of these substances. Although soil organic matter (SOM) content of the samples collected during the current site investigation was not determined, the GACs based on 1% organic matter have been used for the assessment. As organic content increases, the mobility of organic contaminants decreases, therefore 1% is considered conservative for a Tier 1 assessment.


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10. Review of Laboratory Analysis

10.1. Chemical Soil Analysis

A total of fourteen soil samples were scheduled for analysis of a range of determinands including metals and metalloids, petroleum hydrocarbons, monoaromatic hydrocarbons and polycyclic aromatic hydrocarbons (see Table 10.1). The window sample hole locations are shown in Figure 2. Chemical analysis results including covering certificates are included in Appendix G.

The preliminary risk screening exercise, comparing data against GACs, is considered to be a Tier 1 assessment and gives an indication of Contaminants of Concern. As it is proposed that the site is to be sold for continued commercial / industrial use (as a fuel management facility) the Tier 1 risk screening will use this end use as a basis for the assessment.

Soil samples were selected on the basis of visual and olfactory evidence of contamination, and on the basis of the risk identified in each of the targeted locations. Samples were submitted for analysis of key contaminants associated with specific potential contaminant sources of concern as outlined in Table 10.1.

Table 10.1: Sample Selection & Analysis

Location ID

Sample Depth (m bgl)

Source Material

Target

Analysis M

etal

s / M

eta

lloid

s

Sp

ecia

ted

TP

H (

CW

G)

Sp

ecia

ted

PA

H

Mo

no

aro

mat

ic

Hyd

roc

arb

on

s (B

TE

X &

M

TB

E)

To

tal

Cya

nid

e

To

tal

Ph

eno

ls

(Mo

no

hy

dri

c)

PC

Bs

WS1 1.0 to 1.1 Natural Ground Site of old generator (removed), interceptor

WS2 2.2 to 2.3 Natural Ground

Loading Gantry 3.6 to 3.7 Natural Ground

WS3 3.2 to 3.3 Natural Ground Buried tanks (Tank 5 & Tank 6)

WS4 0.5 to 0.6 Made Ground Buried tanks (Tank 4 &

Tank 5) 2.5 to 2.6 Natural Ground

WS5 1.2 to 1.3 Natural Ground

Buried tank (Tank 3) 2.3 to 2.4 Natural Ground

WS6 0.25 to 0.35 Natural Ground Pig Launching Area

WS7 1.0 to 1.1 Made Ground

Manifold 3.8 to 3.9 Natural Ground

WS8 0.3 to 0.4 Made Ground

Pumphouse 3.9 to 4.0 Made Ground

WS9 0.5 to 0.6 Made Ground Electrical Substation


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10.1.1. Analysis of Inorganic Contaminants

Fourteen of the samples collected were tested for selected inorganic determinands. The results of the initial screening are illustrated in Table 10.2. It should be noted that determinands that recorded concentrations less than the limit of detection in all samples have not been included.

Table 10.2: Inorganic Parameters in Soils (mg/kg)

Potential Contaminant Analyses

(No.)

GAC – Commercial /

industrial

Above GAC (No.)

Min Max Location of max.

Arsenic 14 640 0 2.5 45 WS1; 1.0 to 1.1 m

Water soluble boron 14 192495 0 <0.2 0.2 WS9; 0.5 to 0.6 m

Cadmium 14 230 0 <0.2 1.3 WS2; 2.2 to 2.3 m

Total chromium 14 30356 0 14 38 WS4; 0.5 to 0.6 m

Copper 14 71742 0 7.8 90 WS4; 0.5 to 0.6 m

Lead 14 750 1 <2.0 1,300 WS1; 1.0 to 1.1 m

Mercury 14 368 0 <0.3 0.6 WS6; 0.25 to 0.35 m

Nickel 14 1800 0 8.5 45 WS4; 0.5 to 0.6 m

Selenium 14 13000 0 <1.0 2.5 WS2; 2.2 to 2.3 m

Zinc 14 665453 0 81 600 WS8; 3.9 to 4.0 m

Lead

A single exceedance of the commercial/industrial GAC has been identified, relating to lead at WS1 at a depth of 1.0 to 1.1 m bgl. It should be noted that no samples from shallower depths (i.e. with increasing relevance to human health) are available to confirm the presence of lead at depths closer to the ground surface. However, markedly elevated lead concentrations similar to that measured at WS1 have not been identified elsewhere across the site; and may represent an anomaly (the elevated WS1 concentration is some twenty four times greater than the next highest result). The laboratory re-analysed the sample and the result was of the same order of magnitude as the original result.

No other inorganic determinands recorded concentrations greater than their respective GAC.

10.1.2. Analysis of Organic Contamination

All organic determinands (as detailed in Table 10.1) were measured at concentrations less than their respective laboratory limits of detection in all fourteen of the samples scheduled for organic testing.

10.2. Surface Water Chemical Analysis

Two surface water samples were collected from the Land Yeo river on one occasion (29th October 2012), as detailed in Section 7.2.6. The locations of surface water monitoring points (Land Yeo (A) and Land Yeo (B); respectively located upstream and downstream of the site) are illustrated in Figure 2. Analytical results are presented in Appendix G. The results of the water analysis have been compared to appropriate water quality standards, EQS and DWS.


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10.2.1. Inorganic Analysis

A summary of inorganic analysis data from the surface water monitoring is summarised in Table 10.3. It should be noted that determinands that recorded concentrations less than the limit of detection in both of the samples, have not been included in the table.

Table 10.3: Inorganic Parameters in Surface Water

Contaminant Units Limit of

Detection

WQS Land Yeo (A)

Land Yeo (B)

No of samples

above WQS

Location of exceedances EQS1 DWS2

Arsenic µg/l 1 50 10 8.0 7.2 0 N/A

Boron µg/l 10 2000 1000 47 46 0 N/A

Copper µg/l 0.4 10 2000 3.4 2.8 0 N/A

Chromium µg/l 0.7 3.44 50 0.5 0.6 0 N/A

Lead µg/l 1 7.2 25 1.3 <1 0 N/A

Nickel µg/l 0.3 20 20 1.1 1.2 0 N/A

Zinc µg/l 0.4 75 3 11 10 0 N/A

Notes:

1. Freshwater EQS values have been used. Where more than one EQS value exists, the value for the protection of salmonid fish has been used. Where a WQS has been set by the Water Framework Directive (for implementation by 2015) this value has been used.

2. DWS relate to Water Supply (Water Quality) Regulations (Northern Ireland) 2002 where possible. Where a standard was not set in these regulations the Water Supply (Water Quality) Regulations (England and Wales) 2000 and 1989 Regulations have been used.

3. N/A – Not applicable.

4. Lowest WFD standard for Cr(IV) used.

10.2.2. Organic Analysis

All of the organic determinands were measured at concentrations less than the laboratory detection limits in both the upstream and downstream samples.

10.3. Summary of Analytical Data

10.3.1. Soils

Inorganics: The review of chemical analysis data has identified lead at one location (WS1, 1.0 to 1.1 m) as a potential contaminant of concern. The concentration measured in this sample (1,300 mg/kg) is in exceedance of the GAC (750 mg/kg) for commercial/industrial land use. This concentration is also some twenty four times greater than the second highest concentration measured. It is conjectured that this concentration may be an anomaly, or could possibly have arisen from historical spills of leaded fuel during refuelling of the old generator, which it is understood was previously located close to this sample point. All of the other inorganic analyses showed soil concentrations to be well below the relevant GACs.


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Organics: The concentrations or all organic compounds determined were shown to be less than the laboratory limits of detection in all of the fourteen scheduled samples.

10.3.2. Surface Water

Inorganics: No exceedances of the WQS were recorded in relation to inorganic parameters.

Organics: The concentrations or all organic compounds determined were shown to be less than the laboratory limits of detection in both the upstream and downstream water samples collected from the Land Yeo river.

In respect of the locations excavated and samples analysed, the results demonstrate that there is no significant or widespread inorganic or organic contamination on the site. One soil sample from the north eastern area of the site did show a high concentration of lead, however, this is considered to be a very localised, unexplained ‘hot-spot’, and despite its proximity to the river, no such elevated concentration of lead was recorded in the nearby surface water course, indicating that the river water is not being impacted.


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11. Updated Conceptual Site Model and Environmental Risk Assessment

The following sections describe the updated CSM and the contaminant sources, pathways and potential receptors identified at the site following assessment of the chemical analysis results.

11.1. Conceptual Site Model

An updated CSM has been formulated based on the following site characteristics:

Current site use: mothballed fuel storage depot;

Surrounding area land-use comprises predominantly low lying agricultural pasture and arable land with several residential dwellings, located primarily to the east and south;

Site history: Fuel storage depot, constructed in the late 1930s and closed in c.1979.

Made Ground was identified at limited locations across the site, and in each instance was comprised of reworked natural material;

The geological map indicates that the site is underlain by superficial deposits comprising Head, which is composed of clays, silts, sands and gravels. Material of similar composition was identified in all nine window sample locations excavated across the site;

The solid geology beneath the site comprises mudstones of the Mercia Mudstone Formation. Mudstone was identified in six of the nine window sample holes;

The site is underlain superficial deposits (Head), classified as a Secondary Undifferentiated Aquifer, which is considered to have a low potential to transmit contaminants to groundwater, and by solid strata (mudstone) classified as a Secondary B Aquifer, which is considered to have the potential to store and transmit limited amounts of groundwater.

No groundwater was encountered in any of the window sample holes during the investigation; however, it is still thought possible that a pathway for contaminant migration within the aquifer and to the Land Yeo river remains. Previous investigations did encounter groundwater beneath the site. It is considered likely that a degree of hydraulic continuity exists, between the shallow groundwater and the Land Yeo river.

The Land Yeo river flows close to the site’s northern boundary (from east to west) and it is understood that it receives surface water drainage discharge from the site. The river is considered a receptor;

The site is not located within close proximity to sensitive ecological areas;

A single isolated ‘hot-spot’ of elevated lead concentrations was identified in natural soil at one location (WS1), the source of this is conjectured to be either an anomaly or contamination arising from a former generator, which it is understood was previously located nearby;

No other inorganic determinands were measured at concentrations exceeding the screening criteria in soils;


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All inorganic determinands were shown to be present at generally low concentrations in the surface water samples from the Land Yeo river, and were not in exceedance of the thresholds;

All organic analyses returned results less than the laboratory limits of detection in all soil and water samples, from all sample locations; and

SKM Enviros understands that the site is being retained in its present use. Human health receptors have therefore been assessed for continued commercial/industrial use only.

11.2. Potential Contaminant Sources

The initial potential sources of contamination identified at the site are detailed in Section 5.2. Two sources were identified, each comprised of various similar features, located across the entire site. Each source was assigned a unique reference number. The potential sources investigated as part of the October 2012 intrusive works were sources which were identified to have the highest risks to receptors, although lower risk sources were also investigated at the same time. The list of sources investigated is presented in Table 6.1 and are detailed in Sections 6.1 and 6.2. The preliminary risk assessment for the potential sources investigated has been updated

11.3. Identified Pathways (All End-use Scenarios)

The identified pathways are as per the original CSM (Figure 3).

11.4. Identified Receptors (All Scenarios)

The identified receptors are as per the original CSM (Figure 3).

11.5. Updated Risk Assessment

An updated risk assessment has been undertaken for these potential source-pathway-receptor linkages to identify potentially unacceptable risks on a qualitative basis based on the chemical analysis results detected during the intrusive works. This approach is based on DEFRA and the Environment Agency (Ref. 2) on risk assessment and Model Procedures, whilst reference has also been given to the DIO LQA Management Guide (Ref. 8) as described in Chapter 5. The updated risk assessment is presented in Table 11.1. Where risks have been updated based on the site investigation data the previous assessment is presented in brackets.


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Table 11.1: Updated summary of potential environmental risks for commercial / industrial end use and during below ground and maintenance works

Potential Source

Potential Pollutant

Potential Receptors

Potential Pathways

to Receptors

Associated Hazard

[severity]


Risk / Significance

S1 Electrical Substation and Transformers

PCBs Humans Health hazard Absence of organic contamination, in soil samples from WS9 which is located adjacent to the substation/transformer.



Minor

(initial severity Medium which assumed contaminant concentrations of significance)

Unlikely No elevated contaminant concentrations detected in shallow Made Ground or natural soils.

Negligible

(preliminary assessment Low)

B. Below ground and Maintenance workers


Minor


Unlikely No elevated contaminant concentrations detected in shallow Made Ground or natural soils.

Negligible

(preliminary assessment Moderate / Low)

Controlled Waters


Intrusive investigation has revealed an absence of organic contamination in soils across the site, and specifically, in soil samples from WS9 (adjacent the substation and transformer). No groundwater encountered in any of the window sample holes.

C. Groundwater



Minor


Unlikely

PCBs not identified in the samples tested

Negligible



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Potential Source

Potential Pollutant

Potential Receptors

Potential Pathways

to Receptors

Associated Hazard

[severity]


Risk / Significance

S1 Electrical Substation and Transformers continued

PCBs continued D. Surface Water

P2, P3 and P4. Leaching of contamination from soils by rainwater infiltration and migration through groundwater in hydraulic continuity with the surface water and surface runoff

Minor


Unlikely

PCBs not identified in samples tested.

Negligible




Health of livestock

Minor


Unlikely

No elevated contaminant concentrations detected in shallow Made Ground or natural soils

Negligible



Hydrocarbons Humans Health hazard No organic contaminants were identified in any soil sample above the laboratory limits of detection during the intrusive investigation.

However, a single elevated (concentration greater than the assessment criterion) occurrence of lead was identified in soil at WS1, this is considered to be a localised anomaly and not indicative of a wider lead contamination issue across the site.



Minor


Unlikely Significantly elevated contaminant concentrations not detected in shallow Made Ground or natural soils.

Negligible


B. Below Ground and Maintenance workers


Minor

(initial severity Mild which assumed contaminant concentrations of significance)

Low likelihood Significantly elevated contaminant concentrations not detected in shallow Made Ground or natural soils. .

Negligible



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Potential Source

Potential Pollutant

Potential Receptors

Potential Pathways

to Receptors

Associated Hazard

[severity]


Risk / Significance

S2 Non operational above and below ground high pressure fuel pipelines (on and off site) and associated apparatus; storage tanks (on site); interceptors (on site); former generator (no longer present) (on site) continued


Controlled Waters


Intrusive investigation has revealed an absence of organic contamination in soils across the site. All surface water samples analysed were below the relative WQS. No groundwater encountered in any of the window sample holes.

C. Groundwater




Minor (initial severity Severe which assumed contaminant concentrations of significance)

Low likelihood Groundwater was not encountered beneath the site, but the geology and hydrogeological classification is indicative of the potential for isolated pockets of groundwater to be present.

Negligible

(preliminary assessment Moderate)

D. Surface Water

Land Yeo river

P3. Migration through groundwater base flow

Impact on surface water

Minor (initial severity Severe which assumed contaminant concentrations of significance)

Unlikely Groundwater not encountered and no elevated contaminant concentrations detected in surface water.

Negligible

(preliminary assessment Moderate)

P4. Surface water runoff

Impact on surface water Minor


Unlikely No elevated contaminant concentrations detected in surface water.

Negligible

(preliminary assessment Moderate / Low)


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Potential Source

Potential Pollutant

Potential Receptors

Potential Pathways

to Receptors

Associated Hazard

[severity]


Risk / Significance



E. Buildings and Services

P5. Direct contact

Damage to buildings and services Minor

(initial severity Mild which assumed contaminant concentrations of significance)

Unlikely No elevated contaminant concentrations identified in the soil samples tested

Negligible


P6. Vapour accumulation

Damage to services and structures Minor (initial severity Severe which assumed contaminant concentrations of significance)

Unlikely No elevated contaminant concentrations identified in the soil samples tested – therefore it is considered unlikely that there is a significant potential for vapour generation

Negligible (preliminary assessment Moderate)



Health of livestock

Minor


Unlikely

No elevated contaminant concentrations detected in shallow Made Ground or natural soils in the areas of site used for grazing

Negligible (preliminary assessment Moderate / Low)

Elevated lead concentration

lead B. Below Ground and Maintenance workers


Medium

(not included in preliminary risk assessment as no known source)

Low likelihood Disturbance of the ground is likely, but any exposure during groundworks will be very short term (acute rather than chronic). Contamination is thought to be very localised as no other elevated concentrations were encountered

Moderate / Low

(Could be reduced to Negligible by utilising appropriate PPE / risk assessment)

11.6. Updated Risk Assessment Summary

The updated risk assessment has taken into consideration the reasoning behind the preliminary risk assessment and the findings of the site investigation in order reassess the risks for the site based on continued or future commercial industrial use (as a fuel management facility). On this basis, the updated risk assessment did not identify any risks greater than Negligible, with the exception of the risk to below ground workers from lead which is assessed as Moderate / Low, although this could be easily reduced to negligible by use of appropriate PPE and risk assessment.

It should be noted that the assessment is based on a relatively small number of targeted sampling locations and there is the possibility that localised areas of contamination remain unidentified at the site. However, there is a good level of confidence from the information gathered that there is not significant and widespread contamination across the site.


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12. Overall Land Quality and Suitability for Use GPSS Flax Bourton is a mothballed PSD which was operational between circa 1939 and 1979. Storage and handling of hydrocarbons was the primary function of the site with large quantities passing through the site.

Groundwater, surface water and ecological sensitivities for the site are assessed as Low to Medium, High and Low respectively.

Initially a number of potentially significant risks from potential sources of contamination were identified based on the site use, history and sensitivity. Predominantly the contaminants of concern were hydrocarbons, but also included PCBs. A targeted intrusive investigation was undertaken in order to refine the preliminary risk assessment. With the exception of one anomalous lead concentration in one soil sample the site investigation did not identify any contaminant concentrations in soils or water that were greater than appropriate generic assessment critera for commercial / industrial use. Specifically no hydrocarbon contaminants were identified above GAC threshold values. On this basis the updated risk assessment assessed all risks to be Negligible with the exception of the risk to below ground workers from lead which is assessed as Moderate / Low, although this could be easily reduced to negligible by use of appropriate PPE and risk assessment.

Overall the site is considered to be suitable for continued or future commercial / industrial use (as a fuel management facility).


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13. References 1. Department for Environment, Food and Rural Affairs, Environmental Protection Act

1990; Part 2A Contaminated Land Statutory Guidance. April 2012.

2. DEFRA/Environment Agency, Model Procedures for the Management of Land Contamination, CLR11, September 2004.

3. Ministry of Defence, Legislation to enable sale of the Government Pipeline and Storage System [information document], Reference DMC 00478 12/13. 04/11

4. British Geological Survey website, http://www.bgs.ac.uk/opengeoscience/

5. Environment Agency website, http://www.environment-agency.gov.uk/

6. Department for Environment Food & Rural Affairs, Environment Agency and Institute of Environmental Health. Guidelines for Environmental Risk Assessment and Management. HMSO July 2000.

7. Construction Industry Research and Information Association (CIRIA), Contaminated Land Risk Assessment. A Guide to Good Practice. CIRIA C552, 2001.

8. Defence Estates, Contaminated Land Management: Land Quality Assessment (LQA) Management Guide, PG 01/07, March 2007.

9. Environment Agency, Review of Crude Oil Derived Petroleum Products in the Aquatic Environment, Draft R&D Technical Report P75/i688, 1999.

10. Environment Agency, The UK Approach for Evaluating Human Health Risk from Petroleum Hydrocarbons in Soils. Science Report P5-080/TR3, 2005.

11. UK Technical Advisory Group on the Water Framework Directive, Application of Groundwater Standards to Regulation, March 2011

12. Ministry of Housing, Spatial Planning and Environment, 1994, Intervention values and target values – soil quality standards.

13. Canadian Council of Ministers of the Environment, 1991, Interim Canadian Environmental Quality Criteria for Contaminated Sites, Ref CCME EPC-CS34.

14. Environment Agency, Review of Crude Oil Derived Petroleum Products in the Aquatic Environment, Draft R&D Technical Report P75/i688, 1999.

15. The Bathing Waters (Classification) Regulations 1999, Statutory Instruments, 1991, Water, England and Wales.


SKM Enviros


FIGURES

Figure 1: Site Location Plan

Figure 2: Site Layout, Potential Contaminant Sources and Exploratory Hole Locations

Figure 3: Initial Conceptual Site Model


SKM Enviros


APPENDICES


SKM Enviros


Appendix A Site Photographs


SKM Enviros


Photograph 1: View west from the main site entrance, showing the offices and Loading Gantry

Photograph 2: The Loading Gantry


SKM Enviros


Photograph 3: Substation and small transformer

Photograph 4: Manifold building and Pumphouse (background)


SKM Enviros


Photograph 5: Interior of the Manifold building showing fuel supply apparatus

Photograph 6: Tank No. 5


SKM Enviros


Photograph 7: View to external from stairwell in Tank No. 5 entrance.

Photograph 8: View north east from top of Tank No. 5, showing the Manifold building and Substation (partially obscured by the earth bund)


SKM Enviros


Photograph 9: Tank No. 1

Photograph 10: View south west, Tank No. 2 and the adjacent earth bund


SKM Enviros


Photograph 11: Pig Launching Area

Photograph 12: View inside the interceptor, located in the north west of the site (i.e. north east of the Pig Launching Area)


SKM Enviros


Photograph 13: Proposed location of WS1, near to the site of the old generator (brick structure).

Photograph 14: Land Yeo (A), surface water sample location. Upstream of the site.


SKM Enviros


Photograph 15: Land Yeo (B), surface water sample location. Downstream of the site.

Photograph 16: Reworked made ground (slightly gravelly, silty clay) at WS2, 0 to 1.1 m bgl.


SKM Enviros


Photograph 17: Soft clay at WS2, 1.1 to 2.2 m bgl.

Photograph 18: Firm to stiff clay at WS3, 3 to 4 m bgl, with greyish sandstone gravel bands at 3.1 and 3.4 m bgl. Weak mudstone from 3.9 to 4 m bgl.


SKM Enviros


Photograph 19: Window sample coring in progress at WS5.

Photograph 20: Natural near surface material (slightly gravelly, silty clay) at WS6, 0 to 1 m bgl.


SKM Enviros


Photograph 21: Soft to firm, silty, slightly organic clay at WS6, 2 to 3 m bgl.

Photograph 22: Window sample coring in progress at WS7.

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Government Pipelines and Storage System (GPSS) Portfolio - Flax … · 2019-06-25 · Government Pipelines and Storage System (GPSS) Portfolio - Flax Bourton PSD LAND QUALITY ASSESSMENT